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  • 1.
    Akan, Rabia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Metal-assisted chemical etching for nanofabrication of hard X-ray zone plates2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hard X-ray scanning microscopes, or nanoprobes, make it possible to image samples and probe their chemical, elemental and structural properties at nanoscale resolution. This is enabled by the use of nanofocusing optics. Commonly used optics in nanoprobes for high resolution X-ray experiments are zone plates. Zone plates are circular diffraction optics with radially decreasing grating periods. Their performance depends on their geometrical properties and material. The width of the outermost zone, which today is in the order of a few tens of nanometers, defines the zone plate resolution, while the zone thickness and the material define the X-ray focusing efficiency. For hard X-ray zone plates, the required zone thickness is several micrometers. Therefore, high-aspect ratio nanostructures are a prerequisite for high-resolution, high-efficiency zone plates. The very small structures together with the high-aspect ratios make zone plates one of the most challenging devices to fabricate. A wet-chemical nanofabrication process that has proved its capability of providing silicon nanostructures with ultra-high aspect ratios is metal-assisted chemical etching (MACE). MACE is an electroless, autocatalytic pattern transfer method that uses an etching solution to selectively etch a predefined noble metal pattern into silicon. In this thesis, MACE is optimized specifically for zone plate nanostructures and used in the development of a new zone plate device nanofabrication process. The MACE optimization for silicon zone plate nanostructures involved a systematic investigation of a wide parameter space. The preferable etching solution composition, process temperature, zone plate catalyst design and silicon type were identified. Parameter dependencies were characterized with respect to etching depth and verticality, mechanical stability of zones and silicon surface roughness. Zone plate molds with aspect ratios of 30:1 at 30 nm zone widths were nanofabricated using the optimized MACE process. For use with hard X-rays, the silicon molds were metallized with palladium using electroless deposition (ELD). The first order diffraction efficiency of such a palladium/silicon zone plate was characterized as 1.9 %. Both MACE for the zone plate pattern transfer and ELD for the silicon mold metalization are conceptually simple, relatively low-cost and accessible methods, which opens up for further developments of zone plate device nanofabrication processes.

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  • 2.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Frisk, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundberg, Fabian
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ohlin, Hanna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Johansson, Ulf
    Lund Univ, MAX IV Lab, S-22100 Lund, Sweden..
    Li, Kenan
    SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA..
    Sakdinawat, Anne
    SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA..
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Metal-Assisted Chemical Etching and Electroless Deposition for Fabrication of Hard X-ray Pd/Si Zone Plates2020In: Micromachines, E-ISSN 2072-666X, Vol. 11, no 3, article id 301Article in journal (Refereed)
    Abstract [en]

    Zone plates are diffractive optics commonly used in X-ray microscopes. Here, we present a wet-chemical approach for fabricating high aspect ratio Pd/Si zone plate optics aimed at the hard X-ray regime. A Si zone plate mold is fabricated via metal-assisted chemical etching (MACE) and further metalized with Pd via electroless deposition (ELD). MACE results in vertical Si zones with high aspect ratios. The observed MACE rate with our zone plate design is 700 nm/min. The ELD metallization yields a Pd density of 10.7 g/cm3, a value slightly lower than the theoretical density of 12 g/cm3. Fabricated zone plates have a grid design, 1:1 line-to-space-ratio, 30 nm outermost zone width, and an aspect ratio of 30:1. At 9 keV X-ray energy, the zone plate device shows a first order diffraction efficiency of 1.9%, measured at the MAX IV NanoMAX beamline. With this work, the possibility is opened to fabricate X-ray zone plates with low-cost etching and metallization methods.

  • 3.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, M. S.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructures2018In: RSC Advances, E-ISSN 2046-2069, Vol. 8, no 23, p. 12628-12634Article in journal (Refereed)
    Abstract [en]

    Metal-assisted chemical etching (MACE) reaction parameters were investigated for the fabrication of specially designed silicon-based X-ray zone plate nanostructures using a gold catalyst pattern and etching solutions composed of HF and H2O2. Etching depth, zone verticality and zone roughness were studied as a function of etching solution composition, temperature and processing time. Homogeneous, vertical etching with increasing depth is observed at increasing H2O2 concentrations and elevated processing temperatures, implying a balance in the hole injection and silica dissolution kinetics at the gold-silicon interface. The etching depth decreases and zone roughness increases at the highest investigated H2O2 concentration and temperature. Possible reasons for these observations are discussed based on reaction chemistry and zone plate design. Optimum MACE conditions are found at HFH2O2 concentrations of 4.7 M:0.68 M and room temperature with an etching rate of ≈0.7 μm min-1, which is about an order of magnitude higher than previous reports. Moreover, our results show that a grid catalyst design is important for successful fabrication of vertical high aspect ratio silicon nanostructures. 

  • 4.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, Muhammet S.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructuresManuscript (preprint) (Other academic)
    Abstract [en]

    Metal-assisted chemical etching (MACE) reaction parameters were investigated for the fabrication of specially designed silicon-based x-ray zone plate nanostructures using a gold catalyst pattern and etching solutions composed of HF and H2O2. Etching depth, zone verticality and zone roughness were studied as a function of etching solution composition, temperature and processing time. Homogeneous, vertical etching with increasing depth is observed at increasing H2O2 concentrations and elevated processing temperatures, implying a balance in the hole injection and silica dissolution kinetics at the gold-silicon interface. The etching depth decreases and zone roughness increases at the highest investigated H2O2 concentration and temperature. Possible reasons for these observations are discussed based on reaction chemistry and zone plate design. Optimum MACE conditions are found at HF:H2O2 concentrations of 4.7 M:0.68 M and room temperature with an etching rate of 0.7 micrometers per minute, which is about an order of magnitude higher than previous reports. Moreover, our results show that a grid catalyst design is important for successful fabrication of vertical high aspect ratio silicon nanostructures.

  • 5.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Investigation of Metal-Assisted Chemical Etching for Fabrication of Silicon-Based X-Ray Zone Plates2018In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115Article in journal (Refereed)
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  • 6.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Optimization of metal-assisted chemical etching for deep silicon nanostructuresManuscript (preprint) (Other academic)
  • 7.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Optimization of Metal-Assisted Chemical Etching for Deep Silicon Nanostructures2021In: Nanomaterials, E-ISSN 2079-4991, Vol. 11, no 11, article id 2806Article in journal (Refereed)
    Abstract [en]

    High-aspect ratio silicon (Si) nanostructures are important for many applications. Metal-assisted chemical etching (MACE) is a wet-chemical method used for the fabrication of nanostructured Si. Two main challenges exist with etching Si structures in the nanometer range with MACE: keeping mechanical stability at high aspect ratios and maintaining a vertical etching profile. In this work, we investigated the etching behavior of two zone plate catalyst designs in a systematic manner at four different MACE conditions as a function of mechanical stability and etching verticality. The zone plate catalyst designs served as models for Si nanostructures over a wide range of feature sizes ranging from 850 nm to 30 nm at 1:1 line-to-space ratio. The first design was a grid-like, interconnected catalyst (brick wall) and the second design was a hybrid catalyst that was partly isolated, partly interconnected (fishbone). Results showed that the brick wall design was mechanically stable up to an aspect ratio of 30:1 with vertical Si structures at most investigated conditions. The fishbone design showed higher mechanical stability thanks to the Si backbone in the design, but on the other hand required careful control of the reaction kinetics for etching verticality. The influence of MACE reaction kinetics was identified by lowering the oxidant concentration, lowering the processing temperature and by isopropanol addition. We report an optimized MACE condition to achieve an aspect ratio of at least 100:1 at room temperature processing by incorporating isopropanol in the etching solution.

  • 8.
    Alarcon, Aixa
    et al.
    Johnson Johnson Surg Vision Inc, Groningen, Netherlands..
    Canovas, Carmen
    Johnson Johnson Surg Vision Inc, Groningen, Netherlands..
    Van der Mooren, Marrie
    Johnson Johnson Surg Vision Inc, Groningen, Netherlands..
    Janakiraman, Priya
    Johnson Johnson Surg Vision Inc, Groningen, Netherlands..
    Rosen, Robert
    Johnson Johnson Surg Vision Inc, Groningen, Netherlands..
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Chang, Daniel H.
    Empire Eye Laser Ctr, Bakersfield, CA USA..
    Clinical measurements of peripheral contrast sensitivity in elderly phakic and pseudophakic eyes2022In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 63, no 7Article in journal (Other academic)
  • 9.
    Al-Farsi, Hissa M.
    et al.
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden.;Minist Hlth, Cent Publ Hlth Labs, Muscat, Oman..
    Al-Adwani, Salma
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden.;Sultan Qaboos Univ, Coll Agr & Marine Sci, Dept Anim & Vet Sci, Muscat, Oman..
    Ahmed, Sultan
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden..
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Ambikan, Anoop T.
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden..
    Leber, Anna
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden..
    Al-Jardani, Amina
    Minist Hlth, Cent Publ Hlth Labs, Muscat, Oman..
    Al-Azri, Saleh
    Minist Hlth, Cent Publ Hlth Labs, Muscat, Oman..
    Al-Muharmi, Zakariya
    Sultan Qaboos Univ, Coll Med & Hlth Sci, Dept Microbiol & Immunol, Muscat, Oman..
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Giske, Christian G.
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Microbiol, Stockholm, Sweden..
    Bergman, Peter
    Karolinska Inst, Dept Lab Med, Div Clin Microbiol, Stockholm, Sweden.;Karolinska Univ Hosp, Immunodeficiency Unit, Infect Dis Clin, Stockholm, Sweden..
    Effects of the Antimicrobial Peptide LL-37 and Innate Effector Mechanisms in Colistin-Resistant Klebsiella pneumoniae With mgrB Insertions2019In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 10, article id 2632Article in journal (Refereed)
    Abstract [en]

    Background Colistin is a polypeptide antibiotic drug that targets lipopolysaccharides in the outer membrane of Gram-negative bacteria. Inactivation of the mgrB-gene is a common mechanism behind colistin-resistance in Klebsiella pneumoniae (Kpn). Since colistin is a cyclic polypeptide, it may exhibit cross-resistance with the antimicrobial peptide LL-37, and with other innate effector mechanisms, but previous results are inconclusive. Objective To study potential cross-resistance between colistin and LL-37, as well as with other innate effector mechanisms, and to compare virulence of colistin-resistant and susceptible Kpn strains. Materials/Methods Carbapenemase-producing Kpn from Oman (n = 17) were subjected to antimicrobial susceptibility testing and whole genome sequencing. Susceptibility to colistin and LL-37 was studied. The surface charge was determined by zeta-potential measurements and the morphology of treated bacteria was analyzed with electron microscopy. Bacterial survival was assessed in human whole blood and serum, as well as in a zebrafish infection-model. Results Genome-analysis revealed insertion-sequences in the mgrB gene, as a cause of colistin resistance in 8/17 isolates. Colistin-resistant (Col-R) isolates were found to be more resistant to LL-37 compared to colistin-susceptible (Col-S) isolates, but only at concentrations >= 50 mu g/ml. There was no significant difference in surface charge between the isolates. The morphological changes were similar in both Col-R and Col-S isolates after exposure to LL-37. Finally, no survival difference between the Col-R and Col-S isolates was observed in whole blood or serum, or in zebrafish embryos. Conclusion Cross-resistance between colistin and LL-37 was observed at elevated concentrations of LL-37. However, Col-R and Col-S isolates exhibited similar survival in serum and whole blood, and in a zebrafish infection-model, suggesting that cross-resistance most likely play a limited role during physiological conditions. However, it cannot be ruled out that the observed cross-resistance could be relevant in conditions where LL-37 levels reach high concentrations, such as during infection or inflammation.

  • 10.
    Alimohammadi, Vahid
    et al.
    Univ Tehran, Sch Met & Mat, Coll Engn, Adv Magnet Mat Res Ctr, Tehran 111554563, Iran..
    Seyyed Ebrahimi, Seyyed Ali
    Univ Tehran, Sch Met & Mat, Coll Engn, Adv Magnet Mat Res Ctr, Tehran 111554563, Iran..
    Kashanian, Faezeh
    Univ Tehran, Sch Biol, Coll Sci, Tehran 111554563, Iran..
    Lalegani, Zahra
    Univ Tehran, Sch Met & Mat, Coll Engn, Adv Magnet Mat Res Ctr, Tehran 111554563, Iran..
    Habibi-Rezaei, Mehran
    Univ Tehran, Sch Biol, Coll Sci, Tehran 111554563, Iran..
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hydrophobic Magnetite Nanoparticles for Bioseparation: Green Synthesis, Functionalization, and Characterization2022In: MAGNETOCHEMISTRY, ISSN 2312-7481, Vol. 8, no 11, p. 143-, article id 143Article in journal (Refereed)
    Abstract [en]

    In this study, three types of hydrophobized alkyl-modified magnetic nanoparticles (MNPs) comprising direct alkylated-MNPs (A-MNPs), silica-mediated alkyl MNPs (A-SiMNPs), and arginine (Arg)-mediated alkyl MNPs (A-RMNPs) were synthesized successfully. For this purpose, the co-precipitation method was used to synthesize, and octadecyl trimethoxy silane (OTMS) was used as a functionalizing agent. Accordingly, the hydrophobic octadecyl moieties were connected to MNPs. The nanoparticles (NPs) were characterized by XRD, SEM, FTIR, CHN, DLS, and zeta potential analyses. The synthesized coated MNPs represented a decrease in surface charge and magnetization alongside increased surface hydrophobicity and size. It was revealed that the alkylation process was successfully performed to all three MNPs, but A-SiMNPs showed the highest hydrophobicity. Additionally, the novel A-RMNPs, as the most biocompatible type, and A-MNPs showed the highest magnetization among the synthesized MNPs. The results indicate that synthesized NPs can play an important role in bio applications. However, it was revealed that alkyl chains are easily connected to all three MNPs, and that A-MNPs contained the highest alkyl chains and could affect the re-folding and denaturation process of recombinant proteins.

  • 11. Almessiere, M. A.
    et al.
    Slimani, Y.
    Trukhanov, A. V.
    Sadaqat, A.
    Korkmaz, A. D.
    Algarou, N. A.
    Aydın, H.
    Baykal, A.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Review on functional bi-component nanocomposites based on hard/soft ferrites: Structural, magnetic, electrical and microwave absorption properties2021In: Nano-Structures and Nano-Objects, ISSN 2352-507X, Vol. 26, article id 100728Article in journal (Refereed)
    Abstract [en]

    Bi-component hard (H) (hexaferrite) and soft (S) (spinel) ferrites nanocomposites are gaining interest scientifically and technically, not only for combining the high magnetization of spinel ferrite nanomaterials and the high coercivity of hexaferrite magnetic nanomaterials but also for the outstanding exchange-coupling behavior among hard and soft magnetic phase. The improved magnetic features lead to produce a new nanocomposite with higher microwave absorption capacity in comparison with ferrites with a single absorption mechanism. Exchange-coupled effect has a potential application based on microwave absorption, recording media, permanent magnets, biomedical and other applications. Intensive studies have been conducted on this topic to produce hard/soft (H/S) ferrite nanocomposites with establishment of exchange coupled effect between the two phases. Preparation methods, microstructure, magnetics features, microwave and dielectric properties, and applications are elaborated. Consequently, a comprehensive effort has been made to contain an original reference investigating in detail the precise outcomes of the published papers. 

  • 12.
    Almessiere, M. A.
    et al.
    Imam Abdulrahman Bin Faisal Univ, Coll Sci, Dept Phys, POB 1982, Dammam 31441, Saudi Arabia.;Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Biophys, POB 1982, Dammam 31441, Saudi Arabia..
    Unal, B.
    Istanbul Univ Cerrahpasa, Inst Forens Sci & Legal Med, Buyukcekmece Campus, TR-34500 Istanbul, Turkey..
    Slimani, Y.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Biophys, POB 1982, Dammam 31441, Saudi Arabia..
    Gungunes, H.
    Hitit Univ, Dept Phys, Cevre Yolu Bulvari, TR-19030 Corum, Turkey..
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Tashkandi, N.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Nanomed Res, POB 1982, Dammam 31441, Saudi Arabia..
    Baykal, A.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Nanomed Res, POB 1982, Dammam 31441, Saudi Arabia..
    Sertkol, M.
    Imam Abdulrahman Bin Faisal Univ, Dept Basic Sci, Preparatory Year & Supporting Studies, POB 1982, Dammam 34212, Saudi Arabia..
    Trukhanov, A. V.
    Yildiz, A.
    Namik Kemal Univ, Corlu Engn Fac, Text Engn Dept, TR-59860 Corlu Tekirdag, Turkey..
    Manikandan, A.
    Bharath Univ, Bharath Inst Higher Educ & Res BIHER, Dept Chem, Chennai 600073, Tamil Nadu, India.;Bharath Inst Higher Educ & Res BIHER, Ctr Catalysis & Renewable Energy, Chennai 600073, Tamil Nadu, India..
    Effects of Ce-Dy rare earths co-doping on various features of Ni-Co spinel ferrite microspheres prepared via hydrothermal approach2021In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 14, p. 2534-2553Article in journal (Refereed)
    Abstract [en]

    The effects of Ce-Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni-Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni0.5-Co0.5CexDyxFe2-2xO4 were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E-g) and is found in the range 1.63 eV - 1.84 eV. Fe-57 Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy3+-Ce3+ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce3+-Dy3+ ions within the NiCo ferrite structure. The saturation magnetization (M-s), remanence (M-r), and coercivity (H-c) increased gradually with increasing Ce-Dy content. At x = 0.04, M-s, M-r, and H-c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n(B)) and magneto-crystalline anisotropy constant (K-eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce3+-Dy3+ content (i.e., x >= 0.06) was found to decrease M-s, M-r, and H-c values. The variations in magnetic parameters (M-s, M-r, and H-c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n(B)). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce-Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce-Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce-Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koop's phenomenological model.

  • 13. Amaya, Andrew J.
    et al.
    Pathak, Harshad
    Modak, Viraj P.
    Laksmono, Hartawan
    Loh, N. Duane
    Sellberg, Jonas A.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Sierra, Raymond G.
    McQueen, Trevor A.
    Hayes, Matt J.
    Williams, Garth J.
    Messerschmidt, Marc
    Boutet, Sebastien
    Bogan, Michael J.
    Nilsson, Anders
    Stan, Claudiu A.
    Wyslouzil, Barbara E.
    How Cubic Can Ice Be?2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 14, p. 3216-3222Article in journal (Refereed)
    Abstract [en]

    Using an X-ray laser, we investigated the crystal structure of ice formed by homogeneous ice nucleation in deeply supercooled water nanodrops (r approximate to 10 nm) at similar to 225 K The nanodrops were formed by condensation of vapor in a supersonic nozzle, and the ice was probed within 100 mu s of freezing using femtosecond wide-angle X-ray scattering at the Linac Coherent Light Source free-electron X-ray laser. The X-ray diffraction spectra indicate that this ice has a metastable, predominantly cubic structure; the shape of the first ice diffraction peak suggests stacking-disordered ice with a cubicity value, chi, in the range of 0.78 +/- 0.05. The cubicity value determined here is higher than those determined in experiments with micron-sized drops but comparable to those found in molecular dynamics simulations. The high cubicity is most likely caused by the extremely low freezing temperatures and by the rapid freezing, which occurs on a similar to 1 mu s time scale in single nanodroplets.

  • 14.
    Arsana, Komang G.Y.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Saladino, Giovanni
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Brodin, Bertha
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory Liquid-Jet X-ray Microscopy and X-ray Fluorescence Imaging for Biomedical Applications2024In: International Journal of Molecular Sciences, ISSN 1661-6596, E-ISSN 1422-0067, Vol. 25, no 2, article id 920Article in journal (Refereed)
    Abstract [en]

    Diffraction-limited resolution and low penetration depth are fundamental constraints in optical microscopy and in vivo imaging. Recently, liquid-jet X-ray technology has enabled the generation of X-rays with high-power intensities in laboratory settings. By allowing the observation of cellular processes in their natural state, liquid-jet soft X-ray microscopy (SXM) can provide morphological information on living cells without staining. Furthermore, X-ray fluorescence imaging (XFI) permits the tracking of contrast agents in vivo with high elemental specificity, going beyond attenuation contrast. In this study, we established a methodology to investigate nanoparticle (NP) interactions in vitro and in vivo, solely based on X-ray imaging. We employed soft (0.5 keV) and hard (24 keV) X-rays for cellular studies and preclinical evaluations, respectively. Our results demonstrated the possibility of localizing NPs in the intracellular environment via SXM and evaluating their biodistribution with in vivo multiplexed XFI. We envisage that laboratory liquid-jet X-ray technology will significantly contribute to advancing our understanding of biological systems in the field of nanomedical research.

  • 15. Attwood, D T
    et al.
    Hertz, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Midorikawa, K
    Obara, M
    Introduction to the issue on short wavelength and EUV lasers2004In: IEEE Journal of Selected Topics in Quantum Electronics, ISSN 1077-260X, E-ISSN 1558-4542, Vol. 10, no 6, p. 1241-1243Article in journal (Other academic)
  • 16.
    Azadpour, Behnam
    et al.
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
    Aharipour, Nazli
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
    Paryab, Amirhosein
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
    Omid, Hamed
    Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran.
    Abdollahi, Sorosh
    Department of Biomedical Engineering, University of Calgary, Alberta, Canada.
    Madaah Hosseini, Hamidreza
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
    Malek Khachatourian, Adrine
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Seifalian, Alexander M.
    Nanotechnology & Regenerative Medicine Commercialisation Centre (NanoRegMed Ltd, Nanoloom Ltd, & Liberum Health Ltd), London BioScience Innovation Centre, London, UK.
    Magnetically-assisted viral transduction (magnetofection) medical applications: An update2023In: Biomaterials Advances, E-ISSN 2772-9508, Vol. 154, article id 213657Article, review/survey (Refereed)
    Abstract [en]

    Gene therapy involves replacing a faulty gene or adding a new gene inside the body's cells to cure disease or improve the body's ability to fight disease. Its popularity is evident from emerging concepts such as CRISPR-based genome editing and epigenetic studies and has been moved to a clinical setting. The strategy for therapeutic gene design includes; suppressing the expression of pathogenic genes, enhancing necessary protein production, and stimulating the immune system, which can be incorporated into both viral and non-viral gene vectors. Although non-viral gene delivery provides a safer platform, it suffers from an inefficient rate of gene transfection, which means a few genes could be successfully transfected and expressed within the cells. Incorporating nucleic acids into the viruses and using these viral vectors to infect cells increases gene transfection efficiency. Consequently, more cells will respond, more genes will be expressed, and sustained and successful gene therapy can be achieved. Combining nanoparticles (NPs) and nucleic acids protects genetic materials from enzymatic degradation. Furthermore, the vectors can be transferred faster, facilitating cell attachment and cellular uptake. Magnetically assisted viral transduction (magnetofection) enhances gene therapy efficiency by mixing magnetic nanoparticles (MNPs) with gene vectors and exerting a magnetic field to guide a significant number of vectors directly onto the cells. This research critically reviews the MNPs and the physiochemical properties needed to assemble an appropriate magnetic viral vector, discussing cellular hurdles and attitudes toward overcoming these barriers to reach clinical gene therapy perspectives. We focus on the studies conducted on the various applications of magnetic viral vectors in cancer therapies, regenerative medicine, tissue engineering, cell sorting, and virus isolation.

  • 17.
    Azadpour, Behnam
    et al.
    Univ Tehran, Coll Engn, Adv Magnet Mat Res Ctr, Sch Met & Mat, Tehran 111554563, Iran.;Univ Tehran, Coll Sci, Sch Biol, Tehran 111554563, Iran..
    Kashanian, Faezeh
    Univ Tehran, Coll Sci, Sch Biol, Tehran 111554563, Iran..
    Habibi-Rezaei, Mehran
    Univ Tehran, Coll Sci, Sch Biol, Tehran 111554563, Iran..
    Ebrahimi, Seyyed Ali Seyyed
    Univ Tehran, Coll Engn, Adv Magnet Mat Res Ctr, Sch Met & Mat, Tehran 111554563, Iran..
    Yazdanpanah, Roozbeh
    Univ Tehran, Coll Engn, Adv Magnet Mat Res Ctr, Sch Met & Mat, Tehran 111554563, Iran.;Univ Tehran, Coll Sci, Sch Biol, Tehran 111554563, Iran..
    Lalegani, Zahra
    Univ Tehran, Coll Engn, Adv Magnet Mat Res Ctr, Sch Met & Mat, Tehran 111554563, Iran..
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Covalently-Bonded Coating of L-Arginine Modified Magnetic Nanoparticles with Dextran Using Co-Precipitation Method2022In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, no 24, article id 8762Article in journal (Refereed)
    Abstract [en]

    In this study, L-arginine (Arg) modified magnetite (Fe3O4) nanoparticles (RMNPs) were firstly synthesized through a one-step co-precipitation method, and then these aminated nanoparticles (NPs) were, again, coated by pre-oxidized dextran (Dext), in which aldehyde groups (DextCHO) have been introduced on the polymer chain successfully via a strong chemical linkage. Arg, an amino acid, acts as a mediator to link the Dext to a magnetic core. The as-synthesized Arg-modified and Dext-coated arginine modified Fe3O4 NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Both synthesized samples, XRD pattern and FT-IR spectra proved that the core is magnetite. FT-IR confirmed that the chemical bonds of Arg and Dext both exist in the samples. SEM images showed that the NPs are spherical and have an acceptable distribution size, and the VSM analysis indicated the superparamagnetic behavior of samples. The saturation magnetization was decreased after Dext coating, which confirms successive coating RMNPs with Text. In addition, the TGA analysis demonstrated that the prepared magnetic nanocomposites underwent various weight loss levels, which admitted the modification of magnetic cores with Arg and further coating with Dext.

  • 18. Ballikaya, S.
    et al.
    Oner, Y.
    Temel, T.
    Ozkal, B.
    Bailey, T. P.
    Toprak, Muhammet Sadaka
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Uher, C.
    Thermoelectric and thermal stability improvements in Nano-Cu 2 Se included Ag 2 Se2019In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 273, p. 122-127Article in journal (Refereed)
    Abstract [en]

    Recently, silver chalcogenides have attracted great attention due to their potential application for room temperature power generation and local cooling. In this work, we report the thermoelectric properties and thermal stability of bulk Ag 2 Se with nano-Cu 2 Se inclusions ((Ag 2 Se) 1-x (Cu 2 Se) x where x = 0, 0.02 and 0.05). Ag 2 Se samples were prepared via melting, annealing and the nanocomposite was prepared by ball milling this material with required amount of nano-Cu 2 Se; finally, the samples were consolidated by spark plasma sintering. High temperature and low temperature transport properties were assessed by the measurements of the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. The phase composition and microstructure were explored by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, while the thermal stability of samples was investigated via heating microscopy and heat capacity measurement. Room temperature PXRD and SEM indicated that two separate phases of Ag 2 Se and Cu 2 Se form in nano-Cu 2 Se included composites. Heating microscopy and the heat capacity measurement indicate that the thermal stability of Ag 2 Se is enhanced with increasing nano-Cu 2 Se inclusions. The sign of the Seebeck coefficient, in agreement with the Hall coefficient, shows that electrons are the dominant carriers in all samples. The electrical conductivity of the samples increases and the Seebeck coefficient decreases with increasing amount of the nano-Cu 2 Se inclusion, likely due to augmented carrier concentration. Despite the larger electrical conductivity, the thermal conductivity is suppressed with nano-Cu 2 Se inclusions. A high power factor and reduced thermal conductivity lead to a maximum ZT value of 0.45 at 875 K for (Ag 2 Se) 1-x (nano-Cu 2 Se) x sample where x is 0.05.

  • 19.
    Barnkob, Rune
    et al.
    Tech Univ Denmark, Lyngby, Denmark .
    Iranmanesh, Ida
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Bruus, Henrik
    Tech Univ Denmark, Lyngby, Denmark .
    Measuring acoustic energy density in microchannel acoustophoresis using a simple and rapid light-intensity method2012In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 12, no 13, p. 2337-2344Article in journal (Refereed)
    Abstract [en]

    We present a simple and rapid method for measuring the acoustic energy density in microchannel acoustophoresis based on light-intensity measurements of a suspension of particles. The method relies on the assumption that each particle in the suspension undergoes single-particle acoustophoresis. It is validated by the single-particle tracking method, and we show by proper re-scaling that the re-scaled light intensity plotted versus re-scaled time falls on a universal curve. The method allows for analysis of moderate-resolution images in the concentration range encountered in typical experiments, and it is an attractive alternative to particle tracking and particle image velocimetry for quantifying acoustophoretic performance in microchannels.

  • 20.
    Barreiro, D.
    et al.
    Univ Autonoma Madrid, Dept Chem, Madrid 28049, Spain..
    Oostenrijk, B.
    Lund Univ, Dept Phys, S-22100 Lund, Sweden..
    Walsh, N.
    Lund Univ, Dept Phys, S-22100 Lund, Sweden..
    Sankari, A.
    Lund Univ, Dept Phys, S-22100 Lund, Sweden..
    Mansson, E. P.
    DESY, Attosecond Sci Grp, Photon Sci Div, Schenefeld, Germany..
    Maclot, Sylvain
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH Royal Inst Technol, Stockholm, Sweden..
    Sorensen, S.
    Lund Univ, Dept Phys, S-22100 Lund, Sweden..
    Diaz-Tendero, S.
    Univ Autonoma Madrid, Dept Chem, Madrid 28049, Spain.;Univ Autonoma Madrid, IFIMAC, Madrid 28049, Spain..
    Gisselbrecht, M.
    Lund Univ, Dept Phys, S-22100 Lund, Sweden..
    Deepening into the nucleation and fission processes of nano-hydrated ammonia clusters - a combined theoretical and experimental study2020In: 31ST INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC XXXI) / [ed] Ancarani, LU Bordas, C Lepine, F Vernhet, D Bachau, H Bredy, R Dulieu, O Penent, F, IOP Publishing , 2020, article id 202030Conference paper (Refereed)
    Abstract [en]

    While largely studied in the macroscopic scale, the dynamics leading to the nucleation and fission of atmospheric aerosols are very poorly understood at the nano or molecular scale. A model system consisting on ionized hydrogen-bonded ammonia and water molecules have been studied experimentally using mass- and 3D momentum spectroscopy and theoretically using ab initio molecular dynamics simulations.

  • 21.
    Barrett, Laura
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Novel Coercive Field Engineering Method for Short Period KTiOPO42023In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper (Refereed)
    Abstract [en]

    The development of reliable periodic poling methods that allow for sub-µm quasi-phase matched (QPM) gratings and, at the same time, allow for waveguide implementation, is of paramount importance for a large number of applications. For instance, backward-wave optical parametric oscillators [1] are only viable if the QPM period is on the same order of magnitude as the wavelengths of the interacting waves. Furthermore, the integration of such QPM devices in a waveguide format would unveil countless possibilities in quantum optics employing the crystal as an ultrabright bi-photon source with unique spectral characteristics.

  • 22. Baskaran, Karthikeyan
    et al.
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lewis, Peter
    Unsbo, Peter
    Gustafsson, Jörgen
    Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus2012In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 9Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate the effect of eccentric refractive correction and full aberration correction on both high and low contrast grating resolution at the preferred retinal locus (PRL) of a single low vision subject with a longstanding central scotoma.

    Methods: The subject was a 68 year-old female with bilateral absolute central scotoma due to Stargardt’s disease. She has developed a single PRL located 25° nasally of the damaged macula in her left eye, this being the better of the two eyes. High- (100%) and low contrast (25% & 10%) grating resolution acuity was evaluated using four different correction conditions. The first two corrections were solely refractive error corrections; namely habitual spectacle correction and full sphero-cylindrical correction. The latter two corrections were two versions of adaptive optics corrections of all aberrations; namely full sphero-cylindrical refractive correction with additional aberration correction and habitual spectacle correction with aberration correction.

    Results: The mean high contrast (100%) resolution acuity with her habitual correction was 1.06 logMAR, which improved to 1.00 logMAR with full sphero-cylindrical correction. Under the same conditions, low contrast (25%) acuity improved from 1.30 logMAR to 1.14 logMAR. With adaptive optics aberration correction, the high contrast resolution acuities improved to 0.92/0.89 logMAR and the low contrast acuities, to 1.06/1.04 logMAR under both correction modalities. The low contrast (10%) resolution acuity was 1.34 logMAR with adaptive optics aberration correction; however, with purely refractive error corrections she was unable to identify the orientation of the gratings.

    Conclusion: Correction of all aberrations using adaptive optics improves both high and low contrast resolution acuity at the PRL of a single low vision subject with longstanding absolute central scotoma.

  • 23. Baskaran, Karthikeyan
    et al.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Gustafsson, Jörgen
    Influence of Age on Peripheral Ocular Aberrations2011In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 88, no 9, p. 1088-1098Article in journal (Refereed)
    Abstract [en]

    Purpose. To compare peripheral lower and higher order aberrations across the horizontal (+/- 40 degrees) and inferior (-20 degrees) visual fields in healthy groups of young and old emmetropes. Methods. We have measured off-axis aberrations in the groups of 30 younger (24 +/- 3 years) and 30 older (58 +/- 5 years) emmetropes. The aberrations of OD were measured using the COAS-HD VR Shack-Hartmann aberrometer in 10 degrees steps to +/- 40 degrees horizontally and -20 degrees inferiorly in the visual field. The aberrations were quantified with Zernike polynomials for a 4 mm pupil diameter. The second-order aberration coefficients were converted to their respective refraction components (M, J(45), and J(180)). Mixed between-within subjects, analysis of variance were used to determine whether there were significant differences in the refraction and aberration components for the between-subjects variable age and the within-subjects variable eccentricity. Results. Peripheral refraction components were similar in both age groups. Among the higher order coefficients, horizontal coma (C(3)(1)) and spherical aberration (C(4)(0)) varied mostly between the groups. Coma increased linearly with eccentricity, at a more rapid rate in the older group than in the younger group. Spherical aberration was more positive in the older group compared with the younger group. Higher order root mean square increased more rapidly with eccentricity in the older group. Conclusions. Like the axial higher order aberrations, the peripheral higher order aberrations of emmetropes increase with age, particularly coma and spherical aberration.

  • 24.
    Batili, Hazal
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Synthesis, Electrophoretic Deposition, and Characterization of Nanostructured Thermoelectric Materials2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The world’s increasing demand for energy and supplying this energy dominantlyfrom fossil fuels has a major impact on global climate change. Theenergy crisis has gotten more alarming in the recent years which increasedthe motivation for replacing fossil fuels with greener routes for energy harvest.There are various technologies developed for harvesting energy, andthe ability to recover energy from waste heat at a wide range of temperatures (from room temperature to more than 1000C) distinguished thethermoelectric (TE) materials from the rest. The drawback about the thermoelectricdevices is that they are too inefficient to be cost-effective in manyapplications, and the developments in nanotechnology is providing somesolutions to increase the efficiency of these materials and devices.

    The field of thermoelectrics suffer from large discrepancy of theresults in the literature, which is generally attributed to the variations inthe materials qualities, urging a need for the development of synthetictechniques that can lead to large-scale TE materials in reasonable timeframe. In this thesis, three different routes for rapid, scalable, and energyefficient, wet-chemical synthetic techniques for bismuth chalcogenidecompounds are presented. Microwave assisted heating during reactionprovided better control over the particle properties while reducing thereaction time and carbon footprint of the synthetic method, leading tomaterials bismuth chalcogenides with promising TE transport propertiesin a scalable and reproducible manner.

    Hybrid TE materials, and recently emerging solid-liquid TE materialsconcept, requires fabrication of porous TE films, to study the effect of variousinterfaces, including solid and liquid electrolytes. For this purpose, wedeveloped and optimized the electrophoretic deposition (EPD) process toprepare nanostructured porous TE films by preserving the size and morphologyof the as-synthesized bismuth chalcogenide particles. A new glass based substrate is designed and fabricated to study the electronic transportproperties of the electrically active films prepared via EPD. Using this platform,we could clearly demonstrate the significance of the synthetic methodon the surface chemistry and resultant transport properties of the TE materials.The methods and materials developed in this thesis are expected toimpact and expedite further developments in the field of thermoelectrics.

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    Summary
  • 25.
    Batili, Hazal
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ergül, Adem Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Szukiewicz, Rafal
    Institute of Experimental Physics, University of Wroclaw, Maxa Borna 9, 50–204 Wroclaw, Poland, Maxa Borna 9.
    Kuchowicz, Maciej
    Institute of Experimental Physics, University of Wroclaw, Maxa Borna 9, 50–204 Wroclaw, Poland, Maxa Borna 9.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    A comparative study on the surface chemistry and electronic transport properties of Bi2Te3 synthesized through hydrothermal and thermolysis routes2024In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 682, article id 132898Article in journal (Refereed)
    Abstract [en]

    Bismuth telluride-Bi2Te3 is the most promising material for harvesting thermal energy near room temperature. There are numerous works on Bi2Te3 reporting significantly different transport properties, with no clear connection to the synthetic routes used and the resultant surface chemistry of the synthesized materials. It is of utmost importance to characterize the constituent particles’ surface and interfaces to get a better understanding of their influence on the transport properties, that will significantly improve the material design starting from the synthesis step. Electrophoretic deposition (EPD) is a promising technique, enabling the formation of thick films using colloidally stabilized suspensions of pre-made nanoparticles, which can enable the study of the effect of surface chemistry, in connection to the synthetic route, on the material's transport properties. In order to explore the differences in surface chemistry and the resultant transport properties in relation to the synthetic scheme used, here we report on Bi2Te3 synthesised through two wet-chemical routes in water (Hydro-) and oil (Thermo-) as the solvents. XRD analysis showed a high phase purity of the synthesized materials. SEM analysis revealed hexagonal platelet morphology of the synthesized materials, which were then used to fabricate EPD films. Characterization of the EPD films reveal significant differences between the Hydro- and Thermo-Bi2Te3 samples, leading to about 8 times better electrical conductivity values in the Thermo-Bi2Te3. XPS analysis revealed a higher metal oxides content in the Hydro-Bi2Te3 sample, contributing to the formation of a resistive layer, thus lowering the electrical conductivity. Arrhenius plots of electrical conductivity vs inverse temperature was used for the estimation of the activation energy for conduction, revealing a higher activation energy need for the Hydro-Bi2Te3 film, in agreement with the resistive barrier oxide content. Both the samples exhibited negative Seebeck coefficient (S) in the order of 160–170 mV/K. The small difference in S of Hydro- and Themo-Bi2Te3 films was explained by the effective medium theory, revealing that the magnitude of S is linearly correlated with the surface oxide content. Based on the findings, TE materials synthesized through thermolysis route is recommended for further studies using soft treatment/processing of pre-made TE materials. EPD platform presented here is shown to clearly expose the differences in the electronic transport in connection to nanoparticle surface chemistry, proving a promising methodology for the evaluation of morphology, size and surface chemistry dependence of electronic transport for a wide range of materials.

  • 26.
    Batili, Hazal
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ergül, Adem Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Toprak, Muhammet
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    On the electrophoretic deposition of Bi2Te3 nanoparticles through electrolyte optimization and substrate design2022In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 649, p. 129537-, article id 129537Article in journal (Refereed)
    Abstract [en]

    Assembly of thermoelectric nanostructures with pre-defined morphology and surface chemistry on solid sub-strates has been one of the challenges for in-plane TE devices. Electrophoretic deposition (EPD) has the potential to be used for this purpose, where the use of non-conductive substrates is required to enable a reliable evaluation of the transport property of electrically active films. Bi2Te3 nanoparticles, which were synthesized using microwave-assisted hydrothermal route, were used for the EPD of thermoelectric films on glass substrates. A special substrate was fabricated using maskless photolithography, to evaluate the electronic transport properties of the TE films without the interference of the substrate. Electrolyte composition was optimized for high mobility of the suspended nanoparticles, and Bi2Te3 EPD films were fabricated with a high deposition rate, reaching 10 mu m/min. Initial EPD films showed high resistivity, ascribed to the surface oxide layer and capping ligands. The resistance was significantly reduced by the addition of a dithiol molecular linker, capable of interconnecting the Bi2Te3 nanoparticles through ligand-exchange. Seebeck coefficient in the range-150 to-180 mu V/K was measured, revealing the transport through the deposited films. Finally, a power factor of 169 nW/K-2.m was estimated, revealing the potential for the application of this technology to large area TE films as active coatings using the developed EPD process.

  • 27.
    Batili, Hazal
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ergül, Adem
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Szukiewicz, Rafal
    Kuchowicz, Maciej
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Electrophoretic Deposition and Characterization of Bi2Te3 Synthesized through Hydrothermal and Thermolysis RoutesManuscript (preprint) (Other academic)
    Abstract [en]

    Bismuth telluride-Bi2Te3 is a promising material for harvesting thermal energyfor applications near room temperature, where large-area applications requirenew methods of depositing pre-made particulate materials. Electrophoretic deposition(EPD) technique has the promise of enabling the formation of thickfilms using colloidally stabilized suspensions of pre-made nanoparticles. It isvery important to understand the thermoelectric (TE) materials’ performancein relation to the synthetic process, to enable promising and scalable materialstechnologies. EPD films allow to study the effect of surface chemistry, stronglylinked to the synthetic route, on the material’s physico-chemical and transportproperties. Here we report on the synthesis of Bi2Te3 through wet-chemicalreactions performed in two different media as water (hydrothermal-Hydro) andoil (thermolysis-Thermo). Synthesized materials possess platelet morphology,which were then used to fabricated EPD films on specially developed glass substrates. Characterization of the materials and films reveal significant differencesbetween the surface chemistry of the EPD films of Hydro- and Thermo-Bi2Te3samples, where a higher content of metal oxide phases are observed in the Hydro-Bi2Te3 sample. This has a big impact the electronic transport properties, asrevealed by about nine times higher resistance, confirmed by significantly higheractivation energy, of the Hydro-Bi2Te3 film as compared to the Thermo-Bi2Te3film. Slight difference in the Seebeck coefficient (S) was explained by the effectivemedium theory, revealing that the magnitude of S is linearly correlatedwith the surface oxide content. Based on the findings, TE materials synthesizedthrough thermolysis route is recommended for future studies focusing on EPD of TE materials.

  • 28.
    Batili, Hazal
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parsa, Parva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ergül, Adem
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Szukiewicz, Rafal
    Univ Wroclaw, Inst Expt Phys, Maxa Borna 9, PL-50204 Wroclaw, Poland..
    Kuchowicz, Maciej
    Univ Wroclaw, Inst Expt Phys, Maxa Borna 9, PL-50204 Wroclaw, Poland..
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Electrophoretic assembly and electronic transport properties of rapidly synthesized Sb2Te3 nanoparticles2023In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 637, article id 157930Article in journal (Refereed)
    Abstract [en]

    With the recent advances in thermoelectric (TE) technology, there is an increasing demand to develop thick films that would enable large-scale TE devices. Assembly of TE-films from size and morphology-controlled nano particles has been a challenging issue that can be addressed by the use of electrophoretic deposition (EPD) technique. In this work, morphology-controlled Sb2Te3 nanoparticles were synthesized through microwave assisted thermolysis, which were subsequently used for EPD of TE films on specially developed glass substrates. The electronic transport properties were measured in the temp-range of 22-45 degrees C. The as-made EPD films showed a high initial resistance, ascribed to high porosity and the presence of surface oxide/passivating layers. The impact of two types of small organic molecules-as hexanedithiol and dodecanethiol, on the electronic transport was investigated, resulting in a significant improvement in the electrical conductivity of the films. The XPS analysis suggests that the thiols bind to the surface of nanoparticles through formation of sulfides. Seebeck coefficient in the range of + 160 to + 190 & mu;V/K was measured, revealing the p-type transport through the deposited films. Finally, a power factor of about 2.5 & mu;W/K2.m was estimated the first time for p-type EPD films, revealing the potential of the developed nanoparticles and substrate, the small molecule additives and the EPD process presented in this work.

  • 29. Battiston, S.
    et al.
    Boldrini, S.
    Saleemi, Mohsin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Famengo, A.
    Fiameni, S.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fabrizio, M.
    Influence of Al and Mg addition on thermoelectric properties of higher manganese silicides obtained by reactive sintering2017In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 17, no 3, p. 1668-1673Article in journal (Refereed)
    Abstract [en]

    Higher manganese silicides (HMS), represented by MnSix (x = 1.71-1.75), are promising p-type candidates for thermoelectric (TE) energy harvesting systems at intermediate temperature range. The materials are very attractive as they may replace lead based compounds due to their non-toxicity, low cost of starting materials, and high thermal and chemical stability. Dense pellets were obtained through fast reactive sintering by spark plasma sintering (SPS). The addition -or nanoinclusion, of Al and Mg permitted the figure of merit enhancement of the material obtained with this technique, reaching the highest value of 0.40 at 600°C. Morphology, composition and crystal structure of the samples were characterized by electron microscopies, energy dispersive X-ray spectroscopy, and X-ray diffraction analyses, respectively.

  • 30.
    Beigi Kheradmand, Azam
    et al.
    Islamic Azad Univ, Shahrekord Branch, Dept Mech Engn, Shahrekord 8813733395, Iran..
    Mirdamadi, Shamseddin
    Islamic Azad Univ, Sci & Res Branch, Dept Mat Engn, Tehran 8244865179, Iran..
    Lalegani, Zahra
    Islamic Azad Univ, Shahrekord Branch, Young Researchers & Elite Club, Shahrekord 8813733395, Iran..
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Effect of Thermomechanical Treatment of Al-Zn-Mg-Cu with Minor Amount of Sc and Zr on the Mechanical Properties2022In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, no 2, article id 589Article in journal (Refereed)
    Abstract [en]

    In this study, the mechanical and microstructural properties of Al-Zn-Mg-Cu-Zr cast alloy with 0.1% Sc under homogeneous, dissolution, and T6 and thermomechanical treatments with the aim of increasing the volume fraction of MgZn2. Al-3(Sc,Zr) reinforcing precipitates were examined by hardness, microscopic examinations, tensile tests and software analysis. The results showed that, firstly, the hardness results are well proportional to the results of the tensile properties of alloys and, secondly, the strength of the alloy with thermomechanical treatments compared to T6 treatments increased from 492 MPa to 620 MPa and the elongation increased from 8% to 17% and was 100% upgraded. Microstructural and fracture cross section investigations showed that Al-3(Sc,Zr) nanosize dispersoids were evenly distributed among MgZn2 dispersoids and the alloy fracture was of semi-ductile type and nanosize dispersoids less than 10 nm were observed at the end of the dimples in the fracture section. The volume fraction of nanosize dispersoids in the whole microstructure of thermomechanical treatment samples was also much higher than that of T6 heat treated samples, so that the percentage of Al-3(Sc,Zr) precipitates arrived from less than 1% in T6 operation to 8.28% in the quench-controlled thermomechanical operation (with 50% deformation). The quality index (QI) in thermomechanical treatment samples is 19% higher than T6 samples, so that this index has increased from 641 in T6 operation to 760 in samples under thermomechanical treatment due to precipitate morphology, volume fraction of precipitates, their uniform distribution in the matrix, and nano sized precipitates in samples under thermomechanical treatment.

  • 31.
    Bertilson, Michael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory soft x-ray microscopy and tomography2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community.

    This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography.

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  • 32.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olof
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    High-resolution computed tomography with a compact soft x-ray microscope2009In: Optics Express, E-ISSN 1094-4087, Vol. 17, no 13, p. 11057-11065Article in journal (Refereed)
    Abstract [en]

    Computed tomography based on high-resolution soft x-ray microscopy utilizes the natural contrast for biological specimens provided by the water window (lambda = 2.4 - 4.4 nm) and the high resolving power of zone plate objectives. It is capable of revealing the 3D structure of biological specimens at sub-visible-microscopic resolution. To date, the technique has only been available at synchrotron-based microscopes, which limits the researchers access. In the present paper we demonstrate high-resolution soft x-ray tomography with a laboratory zone-plate-based soft x-ray microscope. The specimen, a diatom mounted on a glass capillary, was reconstructed from a tilt series of 53 images covering 180 using a filtered back projection algorithm. The resolution of the tomogram was estimated to a half period of 140 nm using a differential-phase-residual method. Cryo-fixation, increased source brightness and extended-depth-of-focus objectives are important for pushing the resolution of compact systems for biological samples.

  • 33.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Numerical model for tomographic image formation in transmission x-ray microscopy2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 12, p. 11578-11583Article in journal (Refereed)
    Abstract [en]

    We present a numerical image-formation model for investigating the influence of partial coherence, sample thickness and depth-of-focus on the accuracy of tomographic reconstructions in transmission x-ray microscopes. The model combines wave propagation through the object by finite difference techniques with Fourier methods. We include a ray-tracing model to analyse the origin of detrimental stray light in zone plate-based x-ray microscopes. These models allow optimization of x-ray microscopy systems for quantitative tomographic imaging of thick objects. Results show that both the depth-of-focus and the reconstructed local absorption coefficient are highly dependent on the degree of coherence of the optical system.

  • 34.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lindblom, Magnus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wilhein, Thomas
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Compact high-resolution differential interference contrast soft x-ray microscopy2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 064104Article in journal (Refereed)
    Abstract [en]

    We demonstrate high-resolution x-ray differential interference contrast (DIC) in a compact soft x-ray microscope. Phase contrast imaging is enabled by the use of a diffractive optical element objective which is matched to the coherence conditions in the microscope setup. The performance of the diffractive optical element objective is evaluated in comparison with a normal zone plate by imaging of a nickel siemens star pattern and linear grating test objects. Images obtained with the DIC optic exhibit typical DIC enhancement in addition to the normal absorption contrast. Contrast transfer functions based on modulation measurements in the obtained images show that the DIC optic gives a significant increase in contrast without reducing the spatial resolution. The phase contrast operation mode now available for our compact soft x-ray microscope will be a useful tool for future studies of samples with low absorption contrast.

  • 35.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Thieme, J.
    Lindblom, Magnus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Takman, Per
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    First application experiments with the Stockholm compact soft x-ray microscope2009In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 186Article in journal (Refereed)
    Abstract [en]

    Most soft x-ray microscopes operating in the water window (lambda = 2.3 - 4.4 nm) rely on synchrotron radiation sources. In the future we believe scientists will use soft x-ray microscopes as one imaging tool among others in their own laboratory. For this purpose we have developed a full field soft x-ray microscope with a laser-plasma source compact enough to fit on an optical table. In this contribution we describe the current status of this microscope now featuring stable operation at lambda = 3.37 nm or lambda = 2.48 nm. In-house fabricated single element zone plates offering the possibility to perform phase contrast imaging have been implemented. We also report on the first application experiments for compact soft x-ray microscopy, including results from studies of clay minerals and colloids existing in nature and results from phase optics experiments. Planned upgrades of the microscope include increasing the source brightness, implementing more efficient condenser optics, and installing a cryo sample stage for tomography. These improvements will open up for further applications, especially in the field of biological imaging.

  • 36.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Christakou, Athanasia E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory soft-x-ray microscope for cryotomography of biological specimens2011In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, no 14, p. 2728-2730Article in journal (Refereed)
    Abstract [en]

    Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.

  • 37.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Christakou, Athanasia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Jerlström-Hultqvist, J.
    Svärd, S.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory Soft X-Ray Cryo TomographyManuscript (preprint) (Other academic)
    Abstract [en]

    X-rays allow quantitative high-spatial-resolution three-dimensional (3D) imaging of intact unstained cells. Such 3D imaging is provided by soft x-ray lens-based methods (water-window cryo tomography) and hard x-ray lens-less methods (coherent diffraction imaging) are emerging. However, both methods rely on high-brightness synchrotron-radiation sources, which limit the accessibility of a wider scientific community. Here we show 3D water-window cryo tomography with a laboratory-source-based microscope arrangement. The system relies on a λ=2.48-nm liquid-jet laser-plasma source, normal- incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate imaging of intact unstained yeast, protozoan parasites and mammalian cells. 3D images show noise-limited features close to ~100 nm and intra-cellular structure is classified based on the local absorption coefficient. A comprehensive theoretical model of the tomographic imaging system allows optimization of system parameters and a quantitative estimate of the 3D imaging accuracy. The model includes issues such as non-geometric projections of the thick samples and stray light, and is applicable to laboratory as well as synchrotron-based x-ray microscopes. The model shows that laboratory x-ray cryo tomography will allow quantitative 3D imaging with ~30-nm (half-period) resolution over a full 5 µm object.

     

  • 38.
    Bertilsson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Takman, Per
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory arrangement for soft x-ray zone-plate efficiency measurements2007In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, no 2, p. 026103-Article in journal (Refereed)
    Abstract [en]

    We demonstrate a laboratory-scale arrangement for rapid and accurate measurements of the absolute and local efficiency of soft x-ray micro zone plates in the water window. This in-house instrument is based on a single-line lambda=2.88 nm liquid-jet laser-plasma source. Measurements are performed by a simultaneous comparison of first diffraction-order photon flux with the flux in a calibrated reference signal. This arrangement eliminates existing source emission fluctuations. The performance of the method is demonstrated by the result from measurements of two similar to 55 mu m diameter nickel micro zone plates, showing a groove efficiency of 12.9%+/- 1.1% and 11.7%+/- 1.0%. Furthermore, we show that spatially resolved efficiency mapping is an effective tool for a detailed characterization of local zone plate properties. Thus, this laboratory-scale instrument allows rapid feedback to the fabrication process which is important for future improvements.

  • 39. Beye, Martin
    et al.
    Oberg, Henrik
    Xin, Hongliang
    Dakovski, Georgi L.
    Dell'Angela, Martina
    Foehlisch, Alexander
    Gladh, Jorgen
    Hantschmann, Markus
    Hieke, Florian
    Kaya, Sarp
    Kuehn, Danilo
    LaRue, Jerry
    Mercurio, Giuseppe
    Minitti, Michael P.
    Mitra, Ankush
    Moeller, Stefan P.
    Ng, May Ling
    Nilsson, Anders
    Nordlund, Dennis
    Norskov, Jens
    Ostrom, Henrik
    Ogasawara, Hirohito
    Persson, Mats
    Schlotter, William F.
    Sellberg, Jonas A.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wolf, Martin
    Abild-Pedersen, Frank
    Pettersson, Lars G. M.
    Wurth, Wilfried
    Chemical Bond Activation Observed with an X-ray Laser2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 18, p. 3647-3651Article in journal (Refereed)
    Abstract [en]

    The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.

  • 40.
    Bielecki, Johan
    et al.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany..
    Svenda, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.
    Sellberg, Jonas A.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.
    Maia, Filipe R. N. C.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Lawrence Berkeley Natl Lab, NERSC, Berkeley, CA 94720 USA..
    Electrospray sample injection for single-particle imaging with x-ray lasers2019In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 5, article id eaav8801Article in journal (Refereed)
    Abstract [en]

    The possibility of imaging single proteins constitutes an exciting challenge for x-ray lasers. Despite encouraging results on large particles, imaging small particles has proven to be difficult for two reasons: not quite high enough pulse intensity from currently available x-ray lasers and, as we demonstrate here, contamination of the aerosolized molecules by nonvolatile contaminants in the solution. The amount of contamination on the sample depends on the initial droplet size during aerosolization. Here, we show that, with our electrospray injector, we can decrease the size of aerosol droplets and demonstrate virtually contaminant-free sample delivery of organelles, small virions, and proteins. The results presented here, together with the increased performance of next-generation x-ray lasers, constitute an important stepping stone toward the ultimate goal of protein structure determination from imaging at room temperature and high temporal resolution.

  • 41.
    Bjorling, Alexander
    et al.
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Kalbfleisch, Sebastian
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Kahnt, Maik
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Sala, Simone
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Carbone, Gerardina
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Johansson, Ulf
    Lund Univ, Max IV Lab, S-22100 Lund, Sweden..
    Ptychographic characterization of a coherent nanofocused X-ray beam2020In: Optics Express, E-ISSN 1094-4087, Vol. 28, no 4, p. 5069-5076Article in journal (Refereed)
    Abstract [en]

    The NanoMAX hard X-ray nanoprobe is the first beamline to take full advantage of the diffraction-limited storage ring at the MAX IV synchrotron and delivers a high coherent photon flux for applications in diffraction and imaging. Here, we characterize its coherent and focused beam using ptychographic analysis. We derive beam profiles in the energy range 6-22 keV and estimate the coherent flux based on a probe mode decomposition approach.

  • 42. Blomqvist, M.
    et al.
    Pålsson, M.
    Blomster, O.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fundamental-mode fiber-to-fiber coupling at high-power2009In: Solid State Lasers XVIII: Technology and Devices, SPIE - International Society for Optical Engineering, 2009, p. 71930F-Conference paper (Refereed)
    Abstract [en]

    Fiber-to-fiber coupling between two different fibers is a state of the art technology. Products are available on the market where multimode fibers can be coupled with very low power loss, at very high powers (multi-kilowatt). We have, however, always been forced to accept a certain loss in beam quality, manifesting as an increase in the Beam Parameter Product (BPP). In fundamental-mode fiber-to-fiber coupling no beam quality is lost. We instead expect to have a certain power loss in the coupling. This paper addresses the problems in free-space fundamental-mode fiber-to-fiber coupling, including theoretical estimations of expected power loss, estimated demands on the stability of the optics as well as measured values on a fundamental mode fiber-to-fiber coupler. The theoretical calculations of the sensitivity of the coupling efficiency due to radial misalignment and defocus (longitudinal displacement) have been confirmed experimentally. Experimental results at 100 W laser power include 88% coupling efficiency using a large mode area fiber with mode-field diameter (MFD) of 18 μm and 75 % coupling efficiency using a single-mode fiber with MFD of 6.4 μm.

  • 43.
    Branny, Artur
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Didier, Pierre
    Grenoble INP Phelma, F-38031 Grenoble, France..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zadeh, Iman E.
    Delft Univ Technol, ImPhys Dept, Fac Sci Appl, Opt Res Grp, NL-2628 Delft, Netherlands..
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector2021In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, E-ISSN 1558-2515, Vol. 31, no 4, article id 2200305Article in journal (Refereed)
    Abstract [en]

    We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10 nm thin NbTiN film and fabricated on a dielectric substrate (SiO2, Nb3O5) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25 ns temporal recovery time and 82 ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors.

  • 44. Bruus, Henrik
    et al.
    Dual, Jürg
    Hawkes, Jeremy
    Hill, Martyn
    Laurell, Thomas
    Nilsson, Johan
    Radel, Stefan
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Forthcoming lab on a chip tutorial series on acoustofluidics: Acoustofluidics - Exploiting ultrasonic standing wave forces and acoustic streaming in microfluidic systems for cell and particle manipulation2011In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 11, no 21, p. 3579-3580Article in journal (Other academic)
  • 45. Bucht, C.
    et al.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fully automated corneal endothelial morphometry of images captured by clinical specular microscopy2009In: Ophthalmic Technologies XIX, SPIE - International Society for Optical Engineering, 2009, p. 716315-Conference paper (Refereed)
    Abstract [en]

    The corneal endothelium serves as the posterior barrier of the cornea. Factors such as clarity and refractive properties of the cornea are in direct relationship to the quality of the endothelium. The endothelial cell density is considered the most important morphological factor. Morphometry of the corneal endothelium is presently done by semi-automated analysis of pictures captured by a Clinical Specular Microscope (CSM). Because of the occasional need of operator involvement, this process can be tedious, having a negative impact on sampling size. This study was dedicated to the development of fully automated analysis of images of the corneal endothelium, captured by CSM, using Fourier analysis. Software was developed in the mathematical programming language Matlab. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software automatically performed digital enhancement of the images. The digitally enhanced images of the corneal endothelium were transformed, using the fast Fourier transform (FFT). Tools were developed and applied for identification and analysis of relevant characteristics of the Fourier transformed images. The data obtained from each Fourier transformed image was used to calculate the mean cell density of its corresponding corneal endothelium. The calculation was based on well known diffraction theory. Results in form of estimated cell density of the corneal endothelium were obtained, using fully automated analysis software on images captured by CSM. The cell density obtained by the fully automated analysis was compared to the cell density obtained from classical, semiautomated analysis and a relatively large correlation was found.

  • 46. Bucht, C.
    et al.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fully automated corneal endothelial morphometry of images captured by clinical specular microscopy2010In: Ophthalmic Technologies XX, SPIE - International Society for Optical Engineering, 2010, p. 75501E-Conference paper (Refereed)
    Abstract [en]

    The corneal endothelium serves as the posterior barrier of the cornea. Factors such as clarity and refractive properties of the cornea are in direct relationship to the quality of the endothelium. The endothelial cell density is considered the most important morphological factor of the corneal endothelium. Pathological conditions and physical trauma may threaten the endothelial cell density to such an extent that the optical property of the cornea and thus clear eyesight is threatened. Diagnosis of the corneal endothelium through morphometry is an important part of several clinical applications. Morphometry of the corneal endothelium is presently carried out by semi automated analysis of pictures captured by a Clinical Specular Microscope (CSM). Because of the occasional need of operator involvement, this process can be tedious, having a negative impact on sampling size. This study was dedicated to the development and use of fully automated analysis of a very large range of images of the corneal endothelium, captured by CSM, using Fourier analysis. Software was developed in the mathematical programming language Matlab. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software automatically performed digital enhancement of the images, normalizing lights and contrasts. The digitally enhanced images of the corneal endothelium were Fourier transformed, using the fast Fourier transform (FFT) and stored as new images. Tools were developed and applied for identification and analysis of relevant characteristics of the Fourier transformed images. The data obtained from each Fourier transformed image was used to calculate the mean cell density of its corresponding corneal endothelium. The calculation was based on well known diffraction theory. Results in form of estimated cell density of the corneal endothelium were obtained, using fully automated analysis software on 292 images captured by CSM. The cell density obtained by the fully automated analysis was compared to the cell density obtained from classical, semiautomated analysis and a relatively large correlation was found.

  • 47.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    A model for corneal endothelial morphometry by diffraction2006In: Progr. Biomed. Opt. Imaging Proc. SPIE, 2006Conference paper (Refereed)
    Abstract [en]

    As a part of an ongoing project on corneal endothelium morphometry by diffraction, a model for corneal endothelium simulation has been developed. The model has been developed in the mathematical programming language Matlab™. Images of corneal endothelium were simulated and the diffraction pattern of the image was calculated. The diffraction pattern was calculated for a series of endothelial images while varying important variables in the simulated image. This rendered the theoretical relationships between values of variables in the diffraction pattern and values of morphometric variables in the image. At this stage, the analysis focused on the expression of endothelial mean cell size and coefficient of variation in the diffraction pattern, respectively. As expected from diffraction theory, it was found that there is a direct linear relationship between mean cell size and distance between periodic variations in the diffraction pattern. We further found that the ratio between the intensity in the central maximum and the intensity in the first harmonic of the diffraction pattern was functionally depending on the variation in cell size. The current findings demonstrate that it is possible to theoretically determine average cell size and coefficient of variation of cell size in the diffraction pattern.

  • 48.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Karolinska Institutet, Sweden.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Recording the diffraction pattern reflected from corneal endothelium2007In: Ophthalmic Technologies XVII, SPIE - International Society for Optical Engineering, 2007, p. 42610-42610Conference paper (Refereed)
    Abstract [en]

    As a part of an ongoing research project on morphometrical diagnosis of the corneal endothelium, an experimental optical setup has been created. The structure of the corneal endothelial cells could be considered a reflecting periodical aperture. Hence, the diffraction pattern reflected from the endothelium contains valuable morphometrical information. In the present work, focus has been on sampling the posterior surface of explanted corneas. Methods: An optical setup was created, using a 632.8 nm He-Ne laser as the light source. The desired diffraction pattern was produced as a collimated reflection. Hence, because the posterior surface of the cornea is concave, lenses were used to attain the right divergence of the light impingent on the corneal endothelium. These lenses also made it possible to adjust the sampling spot size. A beam splitter (BS) was used to provide an optical path for both the impinging laser beam as well as the reflected diffracted beam. The lens acting as a Fourier lens was then placed after the BS. At the back focal plane of the Fourier lens, a CCD detector was used for recording in the Fourier plane. In the process of creating the setup, explanted corneas were emulated using grated contact lenses. Results: The current optical set up allows identification of a diffraction pattern from a concave spherical surface with a radius of curvature of the same order as a human cornea.

  • 49.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    The impact of horizontal offset of the cornea during corneal specular microscopy2008In: Progr. Biomed. Opt. Imaging Proc. SPIE, 2008Conference paper (Refereed)
    Abstract [en]

    We are developing automated morphometric analysis of the corneal endothelium. Here, the general impact of horizontal offset of the cornea on morphometry was examined. Errors due to perspective during imaging with a Clinical Specular Microscope (CSM) were analyzed considering semi automated analysis software and fully automated Fourier analysis software. Methods: A mathematical model of the cornea was created. Trigonometry was applied to find the relationship between the horizontal offset of the cornea relative to the microscope objective, and the consecutive errors from perspective changes in the image. An experimental setup was created using a cornea made of polymethyl methacrylate (PMMA). The posterior surface of the PMMA cornea was horizontally marked. The PMMA cornea was placed in a holder. Difference in refractive index between real endothelium and aqueous humor was emulated using high refractive index liquid. Images with varying horizontal offset on the PMMA corneal posterior surface, along with their relative offset coordinates were captured, using CSM. Results: Experiments using controlled offset of the cornea in relation to its center estimated that analyzable images can be acquired within an interval of 1.26 mm, using central cornea sampling CSM. Because of refractive indices along with light scattering differences between the corneal tissue and PMMA , the 1.26 mm interval should be considered a first estimate for feasible CSM images. The effect of corneal endothelial offset during imaging with CSM or fully automated Fourier analysis should be considered.

  • 50.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Söderberg, Per
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors2011In: ACTA OPHTHALMOLOGICA, ISSN 1755-375X, Vol. 89, no 3, p. e242-e250Article in journal (Refereed)
    Abstract [en]

    Purpose: We aimed at developing simulation software capable of producing images of corneal endothelium close to identical to images captured by clinical specular microscopy with defined morphometrical characteristics. It was further planned to demonstrate the usefulness of the simulator by analysing measurement errors associated with a trained operator using a commercially available semi-automatic algorithm for analysis of simulated images. Methods: Software was developed that allows creation of unique images of the corneal endothelium expressing morphology close to identical with that seen in images of corneal specular microscopy. Several hundred unique images of the corneal endothelium were generated with randomization, spanning a physiological range of endothelial cell density. As an example of the usefulness of the simulator for analysis of measurement errors in corneal specular microscopy, a total of 12 of all the images generated were randomly selected such that the endothelial cell density expressed was evenly distributed over the physiological range of endothelial cell density. The images were transferred to a personal computer. The imagenet-640 software was used to analyse endothelial cell size variation, percentage of hexagonal endothelial cells, and endothelial cell density. Results: The simulator developed allows randomized generation of corneal specular microscopy images with a preset expected average and variation of cell structure. Calculated morphometric information of each cell is stored in the simulator. The image quality can secondarily be varied with a toolbox of filters to approximate a large spectrum of clinically captured images. As an example of the use of the simulator, measurement errors associated with one trained operator using the imagenet-640 software, and focusing on endothelial cell density, were examined. The functional dependence between morphometric information estimated with the imagenet-640 software algorithm and real morphometric information as provided by the simulator was analysed with regression. It was demonstrated that that the estimations of endothelial cell size variation was associated with a scaling error and that the random error was strongly dependent on the operator. Conclusion: The newly developed simulator for randomized generation of morphometrically defined corneal specular microscopy images for the first time makes it possible to estimate a spatial scaling error of an available semi-automatic algorithm and to determine the random measurement error of important morphometric estimates in a defined reference sample of images. It is anticipated that the simulator will be a valuable tool for the generation of a large set of morphometrically well-characterized corneal specular microscopy images that can be used for calibration among research centres, for minimization of random errors and for measurement of quality control. Simulated images will be useful for the development of fully automatic analysis of corneal endothelial cell morphometry.

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