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  • 1.
    A. M. Naiini, Maziar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Horizontal Slot Waveguides for Silicon Photonics Back-End Integration2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.

    The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.

    The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.

    From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.

    With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.

     

     

     

     

  • 2.
    Abbasi, Saeed
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Zhu, Yi
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel-rail contact2013In: Tribology International, ISSN 0301-679X, Vol. 60, 136-139 p.Article in journal (Refereed)
    Abstract [en]

    Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of theworn-off material is transformed into airborne particles. Although such wear is well understood, few studiestreat the particles generated. We investigated friction modifiers' effects on airborne particles characteristicsgenerated in wheel-rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pinloaded by a dead weight load 40 N simulated maximum contact pressure over 550 MPa. Airborne particlecharacteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease andwater- and oil-based friction modifiers. The number of particles declined with the grease; the number ofultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.

  • 3.
    Abedin, Ahmad
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Noroozi, Mohammad
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Primetzhofer, Daniel
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Radamson, Henry.H
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    GeSnSi CVD Epitaxy using Silane, Germane, Digermane, and Tin tetrachlorideArticle in journal (Refereed)
    Abstract [en]

    In this study, strain relaxed and compressive strained Ge1-x-ySnxSiy (0.015≤x≤0.15 and 0≤y≤0.15) layers were epitaxially grown on Si substrate in a chemical vapor deposition reactor at atmospheric pressure. Digermane (Ge2H6) and germane (GeH4) were used as Ge precursors and tin tetrachloride (SnCl4) was used as Sn precursor. The growth temperature was kept below 400ᵒC to suppress Sn out diffusion. The layers crystal quality and strain were characterized using XRD, high resolution reciprocal lattice mapping and transmission electron microscopy and the surface morphology was investigated by atomic force microscopy (AFM). Furthermore, the low temperature epitaxial growth up to 15% Si atoms incorporation in Ge0.94Sn0.06 was demonstrated by adding silane (SiH4) as Si precursor. Sn contents calculated from high resolution XRD patterns were confirmed by Rutherford backscattering spectroscopy which shows that Sn atoms are mostly positioned in substitutional sites. AFM analysis showed below 1nm surface roughness for both strained and strain relaxed GeSn layers which make the promising materials for photonics and electronics applications.

  • 4. Abermann, S.
    et al.
    Efavi, J. K.
    Sjoblom, G.
    Lemme, Max C.
    AMO GmbH, AMICA, Aachen, Germany.
    Olsson, J.
    Bertagnolli, E.
    Processing and evaluation of metal gate/high-kappa/Si capacitors incorporating Al, Ni, TiN, and Mo as metal gate, and ZrO2 and HfO2 as high-kappa dielectric2007In: Microelectronic Engineering, ISSN 0167-9317, Vol. 84, no 5-8, 1635-1638 p.Article in journal (Refereed)
    Abstract [en]

    We evaluate various metal gate/high-K/Si capacitors by their resulting electrical characteristics. Therefore, we process MOS gate stacks incorporating aluminium (Al), nickel (Ni), titanium-nitride (TiN), and molybdenum (Mo) as the gate material, and metal organic chemical vapour deposited (MOCVD) ZrO2 and HfO2 as the gate dielectric, respectively. The influence of the processing sequence - especially of the thermal annealing treatment - on the electrical characteristics of the various gate stacks is being investigated. Whereas post metallization annealing in forming gas atmosphere improves capacitance-voltage behaviour (due to reduced interface-, and oxide charge density), current-voltage characteristics degrade due to a higher leakage current after thermal treatment at higher temperatures. The Flatband-voltage values for the TiN-, Mo-, and Ni-capacitors indicate mid-gap pinning of the metal gates, however, Ni seems to be thermally unstable on ZrO2, at least within the process scheme we applied.

  • 5. Abermann, S.
    et al.
    Efavi, J.
    Sjoblom, G.
    Lemme, Max C.
    AMO GmbH, AMICA, Aachen, Germany.
    Olsson, J.
    Bertagnolli, E.
    Impact of Al-, Ni-, TiN-, and Mo-metal gates on MOCVD-grown HfO2 and ZrO2 high-k dielectrics2007In: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 47, no 4-5, 536-539 p.Article in journal (Refereed)
    Abstract [en]

    In this work we compare the impacts of nickel (Ni), titanium-nitride (TiN), molybdenum (Mo), and aluminium (Al), gates on MOS capacitors incorporating HfO2- or ZrO2-dielectrics. The primary focus lies on interface trapping, oxide charging, and thermodynamical stability during different annealing steps of these gate stacks. Whereas Ni, Mo, and especially TIN are investigated as most promising candidates for future CMOS devices, Al acted as reference gate material to benchmark the parameters. Post-metallization annealing of both, TiN- and Mo-stacks, resulted in very promising electrical characteristics. However, gate stacks annealed at temperatures of 800 degrees C or 950 degrees C show thermodynamic instability and related undesirable high leakage currents.

  • 6. Abermann, S.
    et al.
    Sjoblom, G.
    Efavi, J.
    Lemme, Max C.
    AMO GmbH, AMICA, Aachen, Germany.
    Olsson, J.
    Bertagnolli, E.
    Comparative study on the impact of TiN and Mo metal gates on MOCVD-grown HfO2 and ZrO2 high-kappa dielectrics for CMOS technology2007In: Physics of Semiconductors, Pts A and B, 2007, 293-294 p.Conference paper (Refereed)
    Abstract [en]

    We compare metal oxide semiconductor capacitors, investigating Titanium-Nitride and Molybdenum as gate materials, as well as metal organic chemical vapor deposited ZrO2 and HfO2 as high-kappa dielectrics, respectively. The impact of different annealing steps on the electrical characteristics of the various gate stacks is a further issue. The positive effect of post metallization annealing in forming gas atmosphere as well as observed mid-gap pinning of TiN and Mo metal gates is presented.

  • 7.
    Afrasiabi, Roodabeh
    KTH, School of Information and Communication Technology (ICT).
    Hysteresis and Time-delay in the pH Response of Al2O3 and SiO2-gated Silicon Nanoribbon FET SensorsManuscript (preprint) (Other academic)
    Abstract [en]

    The conventional ion-sensitive field-effect transistor (ISFET) with SiO2 as the insulator of choice has been used as an electrochemical sensor to measure ion concentrations in solutions for many decades. With the ongoing progress in use of silicon nanoribbon (SiNR) FET sensors for fast reliable sensing and the recent demand for pH-sensing technologies in biological applications, it is important to identify the true pH response of the device. However, it has become much more difficult to achieve reliable results across a broad range of pH using SiO2-gated SiNR FET sensors and limitations such as long term drift and hysteresis (also referred to as memory effects) during pH measurements need to be addressed. In this work, we have investigated the electrochemical pH response behavior of silicon oxide-gated SiNR FET sensors and compared it with similar devices (same NR size) but with Al2O3 as the gate oxide. Our studies show that devices passivated with SiO2 show a large hysteresis in the pH response both in acidic and in basic direction, whereas Al2O3 surfaces show slight hysteresis and only in the acidic pH range. Furthermore, in case of SiO2, the total response-time after a pH change appears to be a combination of a fast transient and a slow drift which is related both to the type of oxide and the concentration of the background electrolyte. Consequently, to minimize errors in pH measurements caused by hysteresis and delayed response, we advise performing the measurements at low ionic concentrations and preferably to replace SiO2 by Al2O3 as the gate oxide. In biological applications, we also recommend the integration of an on-chip reference nanoribbon FET for real-time monitoring of problems such as long-term drift and slow response.

  • 8.
    Afrasiabi, Roodabeh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Silicon Nanoribbon FET Sensors: Fabrication, Surface Modification and Microfluidic Integration2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past decade, the field of medical diagnostics has seen an incredible amount of research towards the integration of one-dimensional nanostructures such as carbon nanotubes, metallic and semiconducting nanowires and nanoribbons for a variety of bio-applications. Among the mentioned one-dimensional structures, silicon nanoribbon (SiNR) field-effect transistors (FET) as electro-chemical nanosensors hold particular promise for label-free, real-time and sensitive detection of biomolecules using affinity-based detection. In SiNR FET sensors, electrical transport is primarily along the nanoribbon axis in a thin sheet (< 30 nm) serving as the channel. High sensitivity is achieved because of the large surface-to-volume ratio which allows analytes to bind anywhere along the NR affecting the entire conductivity by their surface charge. Unfortunately, sensitivity without selectivity is still an ongoing issue and this thesis aims at addressing the detection challenges and further proposing effective developments, such as parallel and multiple detection through using individually functionalized SiNRs.We present here a comprehensive study on design, fabrication, operation and device performance parameters for the next generation of SiNR FET sensors towards multiplexed, label-free detection of biomolecules using an on-chip microfluidic layer which is based on a highly cross-linked epoxy. We first study the sensitivity of different NR dimensions followed by analysis of the drift and hysteresis effects. We have also addressed two types of gate oxides (namely SiO2 and Al2O3) which are commonly used in standard CMOS fabrication of ISFETs (Ion sensitive FET). Not only have we studied and compared the hysteresis and response-time effects in the mentioned two types of oxides but we have also suggested a new integrated on-chip reference nanoribbon/microfluidics combination to monitor the long-term drift in the SiNR FET nanosensors. Our results show that compared to Al2O3, silicon-oxide gated SiNR FET sensors show high hysteresis and slow-response which limit their performance only to background electrolytes with low ionic strength. Al2O3 on the other hand proves more promising as the gate-oxide of choice for use in nanosensors. We have also illustrated that the new integrated sensor NR/Reference NR can be utilized for real-time monitoring of the above studied sources of error during pH-sensing. Furthermore, we have introduced a new surface silanization (using 3-aminopropyltriethoxysilane) method utilizing microwave-assisted heating which compared to conventional heating, yields an amino-terminated monolayer with high surface coverage on the oxide surface of the nanoribbons. A highly uniform and dense monolayer not only reduces the pH sensitivity of the bare-silicon oxide surface in a physiological media but also allows for more receptors to be immobilized on the surface. Protocols for surface functionalization and biomolecule immobilization were evaluated using model systems. Selective spotting of receptor molecules can be used to achieve localized functionalization of individual SiNRs, opening up opportunities for multiplexed detection of analytes.Additionally, we present here a novel approach by integrating droplet-based microfluidics with the SiNR FET sensors. Using the new system we are able to successfully detect trains of droplets with various pH values. The integrated system enables a wide range of label-free biochemical and macromolecule sensing applications based on detection of biological events such as enzyme-substrate interactions within the droplets.

  • 9.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO), Protein Technology.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Microwave-assisted silanization of SiNW-FET: characterization and effect on sensing propertiesManuscript (preprint) (Other academic)
  • 10.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Sugunan, Abhilash
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Shahid, Robina
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Microwave mediated synthesis of semiconductor quantum dots2012In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, no 7, 1551-1556 p.Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dots (QD) have tuneable optoelectronic properties and can be easily handled by simple solution processing techniques, making them very attractive for a wide range of applications. Over the past decade synthesis of morphology controlled high quality (crystalline, monodisperse) colloidal QDs by thermal decomposition of organometallic precursors has matured and is well studied. Recently, synthesis of colloidal QDs by microwave irradiation as heating source is being studied due to the inherently different mechanisms of heat transfer, when compared to solvent convection based heating. Under microwave irradiation, polar precursor molecules directly absorb the microwave energy and heat up more efficiently. Here we report synthesis of colloidal II-VI semiconductor QDs (CdS, CdSe, CdTe) by microwave irradiation and compare it with conventional synthesis based on convection heating. Our findings show that QD synthesis by microwave heating is more efficient and the chalcogenide precursor strongly absorbs the microwave radiation shortening the reaction time and giving a high reaction yield.

  • 11.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Söderberg, Lovisa M.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Joensson, Haakan N.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Björk, Per
    Svahn Andersson, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Integration of a Droplet-Based Microfluidic System and Silicon Nanoribbon FET Sensor2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 8Article in journal (Refereed)
    Abstract [en]

    We present a novel microfluidic system that integrates droplet microfluidics with a silicon nanoribbon field-effect transistor (SiNR FET), and utilize this integrated system to sense differences in pH. The device allows for selective droplet transfer to a continuous water phase, actuated by dielectrophoresis, and subsequent detection of the pH level in the retrieved droplets by SiNR FETs on an electrical sensor chip. The integrated microfluidic system demonstrates a label-free detection method for droplet microfluidics, presenting an alternative to optical fluorescence detection. In this work, we were able to differentiate between droplet trains of one pH-unit difference. The pH-based detection method in our integrated system has the potential to be utilized in the detection of biochemical reactions that induce a pH-shift in the droplets.

  • 12. Ahmed, Aseel Bala
    et al.
    Jibril, B.
    Danwittayakul, S.
    Dutta, Joydeep
    Sultan Qaboos Univ, Water Res Ctr, Chair Nanotechnol, Muscat, Oman.
    Microwave-enhanced degradation of phenol over Ni-loaded ZnO nanorods catalyst2014In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 156-157, 456-465 p.Article in journal (Refereed)
    Abstract [en]

    Nickel was loaded onto hydrothermally-grown ZnO nanorods on cordierite substrates and tested as catalysts in microwave-enhanced degradation of phenol from its aqueous solution (100 ppm) at 70 degrees C. Effects of metal loadings (1, 10 and 20 mM impregnation solutions) on the degradation of phenol in aqueous solution was investigated. The catalyst performances were monitored based on phenol degradation, product distributions and carbon dioxide (CO2) evolutions. Based on the type of the catalysts, two different mechanistic pathways for the decomposition were observed-through catechol and/or hydroquinone as intermediates. It was found that the 10mM nickel loaded sample catalyzed the degradation through one pathway with hydroquinone as the benzenediol intermediate formed, while the 20 mM nickel impregnated sample catalyzed the reaction through two pathways, producing catechol as well as hydroquinone by products. These differences in reaction pathways were attributed to the variation in the composition of the nickel compounds and surface structures between the two catalysts. Furthermore, the effect of hydrogen peroxide (H2O2) as an oxidant was explored. It was found that although addition of H2O2 led to an increase in the degree of phenol degradation, it also led to enhanced catalyst leaching. There was also an increase in CO2 evolution due to the addition of H2O2. It was observed that 20 mM nickel-loaded sample without the addition of H2O2 exhibited optimum performance in terms of phenol degradation and CO2 evolution with no drawback of catalyst leaching. Catalytic microwave enhanced degradation is an effective means for the removal of dissolved organic compounds from wastewater.

  • 13. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Rehr, John J.
    Di Ventra, Massimiliano
    Schuller, Ivan
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 12, 125705- p.Article in journal (Refereed)
    Abstract [en]

    Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.

  • 14. Al Alawai, Reem
    et al.
    Laxman, karthik
    Dastgir, Sarim
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM. Sultan Qaboos University, , Oman.
    Role of bonding mechanisms during transfer hydrogenation reaction on heterogeneous catalysts of platinum nanoparticles supported on zinc oxide nanorods2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, 200-206 p.Article in journal (Refereed)
    Abstract [en]

    For supported heterogeneous catalysis, the interface between a metal nanoparticle and the support plays an important role. In this work the dependency of the catalytic efficiency on the bonding chemistry of platinum nanoparticles supported on zinc oxide (ZnO) nanorods is studied. Platinum nanoparticles were deposited on ZnO nanorods (ZnO NR) using thermal and photochemical processes and the effects on the size, distribution, density and chemical state of the metal nanoparticles upon the catalytic activities are presented. The obtained results indicate that the bonding at Pt-ZnO interface depends on the deposition scheme which can be utilized to modulate the surface chemistry and thus the activity of the supported catalysts. Additionally, uniform distribution of metal on the catalyst support was observed to be more important than the loading density. It is also found that oxidized platinum Pt(IV) (platinum hydroxide) provided a more suitable surface for enhancing the transfer hydrogenation reaction of cyclohexanone with isopropanol compared to zero valent platinum. Photochemically synthesized ZnO supported nanocatalysts were efficient and potentially viable for upscaling to industrial applications.

  • 15. Al-Fori, M.
    et al.
    Dobretsov, S.
    Myint, M. T. Z.
    Dutta, Joydeep
    Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, PO Box 17, Postal Code - 123, Al Khoud, Muscat, Oman.
    Antifouling properties of zinc oxide nanorod coatings2014In: Biofouling, ISSN 0892-7014, Vol. 30, no 7, 871-882 p.Article in journal (Refereed)
    Abstract [en]

    In laboratory experiments, the antifouling (AF) properties of zinc oxide (ZnO) nanorod coatings were investigated using the marine bacterium Acinetobacter sp. AZ4C, larvae of the bryozoan Bugula neritina and the microalga Tetraselmis sp. ZnO nanorod coatings were fabricated on microscope glass substrata by a simple hydrothermal technique using two different molar concentrations (5 and 10 mM) of zinc precursors. These coatings were tested for 5 h under artificial sunlight (1060 W m(-2) or 530 W m(-2)) and in the dark (no irradiation). In the presence of light, both the ZnO nanorod coatings significantly reduced the density of Acinetobacter sp. AZ4C and Tetraselmis sp. in comparison to the control (microscope glass substratum without a ZnO coating). High mortality and low settlement of B. neritina larvae was observed on ZnO nanorod coatings subjected to light irradiation. In darkness, neither mortality nor enhanced settlement of larvae was observed. Larvae of B. neritina were not affected by Zn2+ ions. The AF effect of the ZnO nanorod coatings was thus attributed to the reactive oxygen species (ROS) produced by photocatalysis. It was concluded that ZnO nanorod coatings effectively prevented marine micro and macrofouling in static conditions.

  • 16. Al-Hamdi, A. M.
    et al.
    Sillanpää, M.
    Dutta, Joydeep
    Department of Nanotechnology, Water Research Center, Sultan Qaboos University, 123 Al-Khoudh, Musqat, Oman.
    Photocatalytic degradation of phenol in aqueous solution by rare earth-doped SnO2 nanoparticles2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 14, 5151-5159 p.Article in journal (Refereed)
    Abstract [en]

    The influence of heterogeneous semiconductors on the photodegradation of phenol in water was investigated using doped tin dioxide (SnO2) nanoparticles. Photocatalysts of SnO2 were synthesized with lanthanum (La), cerium (Ce), and neodymium (Nd) dopants. These photocatalysts were synthesized from tin tetrachloride by sol-gel method with different dopant concentrations, and its photocatalytic degradation was investigated up to 0.8 % under UV-A light in aqueous suspensions. The photocatalytic oxidation reactions were studied by varying photocatalyst composition, light intensity, reaction time, pH of the reaction medium, and phenol concentration. It was found that the photocatalytic activity of rare earth-doped SnO2 for phenol decomposition under UV light irradiation was considerably higher than that of pure SnO2 nanoparticles. The experimental results also indicate that more than 95 % phenol was effectively oxidized in the presence of an aqueous suspension of La: SnO2 nanoparticles within 120 min of UV light irradiation.

  • 17. Al-Hamdi, Abdullah M
    et al.
    Sillanpää, Mika
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University, Oman.
    Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation2015In: Journal of Alloys and Compounds, ISSN 0925-8388, Vol. 618, 366-371 p.Article in journal (Refereed)
    Abstract [en]

    Iodine doped tin oxide (SnO2:I) nanoparticles were prepared by sol-gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO2:I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO2 nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO2 nanoparticles under similar illumination conditions.

  • 18. Al-Hinai, A. T.
    et al.
    Al-Hinai, M. H.
    Dutta, Joydeep
    Sultan Qaboos Univ, Water Res Ctr, Al Khoud 123, Oman.
    Application of Eh-pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media2014In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 49, no 1, 645-650 p.Article in journal (Refereed)
    Abstract [en]

    Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO3) particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a solution containing stoichiometric amounts of Zn2+ and Sn4+ was controlled for the precipitation in a one pot synthesis step at room temperature (25 degrees C). The effect of the concentration of the reactants on the particle size was studied by varying the concentration of the precursor (Zn2+ + Sn4+) solution. Scanning electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-organization olnano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and thermo gravimetric analysis (TGA) show that the particles are in ZnSnO3.3H(2)O form.

  • 19. Al-Hinai, M. H.
    et al.
    Al-Hinai, A. T.
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University, 123 Al Khoud, Oman.
    Phase transformation behavior of zinc metastannates obtained by aqueous precipitation at different temperatures2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 20, 7282-7289 p.Article in journal (Refereed)
    Abstract [en]

    Phase transformation studies in ZnO-SnO2 system from zinc metastannate (ZnSnO3) to zinc orthostannate (Zn2SnO4) with annealing temperature are reported. Non-centrosymmetric oxides show unique symmetry dependent and spontaneous polarization properties, which are technologically important. ZnSnO3 particles were synthesized by a simple aqueous synthesis at low temperatures designed with the assistance of potential-pH diagrams. ZnSnO3 particles synthesized at 4 A degrees C are more porous losing the ilmenite structure upon annealing at 200 A degrees C, while the other samples prepared at higher temperatures (25-65 A degrees C) becomes amorphous at 300 A degrees C. The phase transformation into the inverse spinel orthostannate phase occurs around 750 A degrees C in all the samples.

  • 20. Al-Naamani, Laila
    et al.
    Dobretsov, Sergey
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Burgess, J. Grant
    Chitosan-zinc oxide nanocomposite coatings for the prevention of marine biofouling2017In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 168, 408-417 p.Article in journal (Refereed)
    Abstract [en]

    Marine biofouling is a worldwide problem affecting maritime industries. Global concerns about the high toxicity of antifouling paints have highlighted the need to develop less toxic antifouling coatings. Chitosan is a natural polymer with antimicrobial, antifungal and antialgal properties that is obtained from partial deacetylation of crustacean waste. In the present study, nanocomposite chitosan-zinc oxide (chitosan-ZnO) nanoparticle hybrid coatings were developed and their antifouling activity was tested. Chitosan-ZnO nanoparticle coatings showed anti-diatom activity against Navicula sp. and antibacterial activity against the marine bacterium Pseudoalteromonas nigrifaciens. Additional antifouling properties of the coatings were investigated in a mesocosm study using tanks containing natural sea water under controlled laboratory conditions. Each week for four weeks, biofilm was removed and analysed by flow cytometry to estimate total bacterial densities on the coated substrates. Chitosan-ZnO hybrid coatings led to better inhibition of bacterial growth in comparison to chitosan coatings alone, as determined by flow cytometry. This study demonstrates the antifouling potential of chitosan-ZnO nanocomposite hybrid coatings, which can be used for the prevention of biofouling. (C) 2016 Elsevier Ltd. All rights reserved.

  • 21. Al-Saadi, Mubarak J.
    et al.
    Al-Harthi, Salim H.
    Kyaw, Htet H.
    Myint, Myo T. Z.
    Bora, Tanujjal
    Laxman, Karthik
    Al-Hinai, Ashraf
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Influence of Atomic Hydrogen, Band Bending, and Defects in the Top Few Nanometers of Hydrothermally Prepared Zinc Oxide Nanorods2017In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 12, 22Article in journal (Refereed)
    Abstract [en]

    We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H2O within the structure of the NRs. In the absence of H2O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H2O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV (similar to 1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H2O/H* species.

  • 22. Al-Sabahi, Jamal
    et al.
    Bora, Tanujjal
    Al-Abri, Mohammed
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Controlled defects of zinc oxide nanorods for efficient visible light photocatalytic degradation of phenol2016In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 9, no 4, 238Article in journal (Refereed)
    Abstract [en]

    Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO) nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC) was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.

  • 23. Al-Shammari, Rusul M.
    et al.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rice, James H.
    Rodriguez, Brian J.
    Tunable Wettability of Ferroelectric Lithium Niobate Surfaces: The Role of Engineered Microstructure and Tailored Metallic Nanostructures2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 12, 6643-6649 p.Article in journal (Refereed)
    Abstract [en]

    An important aspect of optimizing micro- and optofluidic devices for lab on -a-chip systems is the ability to engineer materials properties including surface structure and charge to control wettability. Biocompatible ferroelectric lithium niobate (LN), which is well-known for acoustic and nonlinear optical applications, has recently found potential micro- and optofluidic applications. However, the tunable wettability of such substrates has yet to be explored in detail. Here, we show that the contact angle of LN substrates can be reproducibly tailored between similar to 7 degrees and similar to 421 degrees by controlling the surface topography and chemistry at the nano- and micrometer scale via ferroelectric domain and polarization engineering and polarization-directed photoassisted deposition of metallic nanostructures.

  • 24. Anceno, A J
    et al.
    Bonduush, I
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology,Thailand.
    Stuetz, R M
    Shipin, O V
    Of Quantum Dots and Microbes: Smart materials for fluorescence based characterization of environmental microflora2013In: Proc. of the Intl. Conf. on Future Trends in Structural, Civil, Environmental and Mechanical Engineering – FTSCEM 2013, SEEK Digital Library , 2013, 61-65 p.Conference paper (Refereed)
    Abstract [en]

    Manganese doped zinc sulfide (ZnS:Mn2+) quantum dots (QDs) were surface derivatized for use as versatile fluorescent reporters is the study of microorganisms of relevance in environmental bioprocesses. When intracellularly introduced into permeabilized target bacterial cells, mercaptoacetic acid (MAA) or dithiothreitol (DTT) treatedZnS:Mn2+QDs proved to be good visualization enhancers for morphological observations with epifluorescence microscopy. Alternatively, cell surface adhesion of chitosan capped ZnS:Mn2+QDs also led to a similar effect, namely of QD enhanced contrast of target cells from intrinsic background fluorescence. When DTT surface derivatized ZnS:Mn2+QDs were conjugated with oligonucleotide probes and used in fluorescent in situ hybridization (FISH) analysis, specific detection of bacterial strains representative ofsome proteobacterial classes was achieved.

  • 25. Anceno, A. J.
    et al.
    Bonduush, I.
    Shipin, O. V.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology.
    Nanoparticle self-assembly via facile (Bio)chemistry: Charge-stabilized metal nanoparticles on microbial cell surfaces2010In: Journal of Bionanoscience, ISSN 1557-7910, Vol. 4, no 1-2, 92-98 p.Article in journal (Refereed)
    Abstract [en]

    With a view of achieving up-scaled nutrition-driven biomimetic assembly of gold nanoparticles, the self-assembly of glutamate- or chitosan stabilized colloidal gold was attempted using viable microbial cells as templates in nutrient rich or poor assembly environment. The likelihood of achieving self-assembly given the type of microbial template, nanoparticle stabilization and predominant biochemical conditions is discussed. While the realization of industrially useful microcomponents from the assembly route maybe technically remote as yet, it was found that present nanoparticles and suitable assembly environment find immediate application in conventional microscopy or as contrast enhancers in the routine study of microbial cell morphology.

  • 26.
    Andersson, Helene
    et al.
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    van den Berg, Albert
    KTH.
    Where are the biologists?: A series of mini-reviews covering new trends in fundamental and applied research, and potential applications of miniaturised technologies2006In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 6, no 4, 467-470 p.Article in journal (Refereed)
  • 27. Andersson, Sandra
    et al.
    Sundberg, Marten
    Pristovsek, Nusa
    Ibrahim, Ahmed
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab. Natl Res Ctr, Egypt.
    Jonsson, Philip
    Katona, Borbala
    Clausson, Carl-Magnus
    Zieba, Agata
    Ramstrom, Margareta
    Soderberg, Ola
    Williams, Cecilia
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab. Univ Houston, USA; Karolinska Inst, Sweden.
    Asplund, Anna
    Insufficient antibody validation challenges oestrogen receptor beta research2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, 15840Article in journal (Refereed)
    Abstract [en]

    The discovery of oestrogen receptor beta (ER beta/ESR2) was a landmark discovery. Its reported expression and homology with breast cancer pharmacological target ER alpha (ESR1) raised hopes for improved endocrine therapies. After 20 years of intense research, this has not materialized. We here perform a rigorous validation of 13 anti-ER beta antibodies, using well-characterized controls and a panel of validation methods. We conclude that only one antibody, the rarely used monoclonal PPZ0506, specifically targets ER beta in immunohistochemistry. Applying this antibody for protein expression profiling in 44 normal and 21 malignant human tissues, we detect ER beta protein in testis, ovary, lymphoid cells, granulosa cell tumours, and a subset of malignant melanoma and thyroid cancers. We do not find evidence of expression in normal or cancerous human breast. This expression pattern aligns well with RNA-seq data, but contradicts a multitude of studies. Our study highlights how inadequately validated antibodies can lead an exciting field astray.

  • 28. Armbrecht, L.
    et al.
    Dincer, C.
    Kling, A.
    Horak, Josef
    KTH, School of Biotechnology (BIO), Protein Technology. University of Freiburg, Germany.
    Kieninger, J.
    Urban, G.
    Self-assembled magnetic bead chains for sensitivity enhancement of microfluidic electrochemical biosensor platforms2015In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 15, no 22, 4314-4321 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a novel approach to enhance the sensitivity of microfluidic biosensor platforms with self-assembled magnetic bead chains. An adjustable, more than 5-fold sensitivity enhancement is achieved by introducing a magnetic field gradient along a microfluidic channel by means of a soft-magnetic lattice with a 350 mu m spacing. The alternating magnetic field induces the self-assembly of the magnetic beads in chains or clusters and thus improves the perfusion and active contact between the analyte and the beads. The soft-magnetic lattices can be applied independent of the channel geometry or chip material to any microfluidic biosensing platform. At the same time, the bead-based approach achieves chip reusability and shortened measurement times. The bead chain properties and the maximum flow velocity for bead retention were validated by optical microscopy in a glass capillary. The magnetic actuation system was successfully validated with a biotin-streptavidin model assay on a low-cost electrochemical microfluidic chip, fabricated by dry-film photoresist technology (DFR). Labelling with glucose oxidase (GOx) permits rapid electrochemical detection of enzymatically produced H2O2.

  • 29.
    Atwa, Mohamed
    KTH, School of Information and Communication Technology (ICT).
    Chemical Vapor Deposition Growth and Density Functional Theory Calculations of Trilayer Graphene2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Density functional theory was employed to investigate the energetics of ABA, ABC, and intermediary stacked phases for both pristine and s-triazine functionalized graphene trilayers. The energy of the ABC-stacked phase relative to the pristine ABA-stacked ground state showed a 94% increase when s-triazine was adsorbed to the graphene surface, confirming previous studies of the ability of s-triazine to facilitate the ABC to ABA phase-transition. This work is outlined in an enclosed publication titled “Trilayer Graphene as a Candidate Material for Phase Change Memory Applications.”

    Subsequently, low-pressure CVD was used to synthesize single-crystal graphene trilayers of up to 200 µm, the largest reported thus far. The defect density, stacking density, and morphology of the CVD-grown graphene trilayers are evaluated using Raman spectroscopy. The layers are also shown to be directly discernable as-grown on copper substrates using dark-field optical microscopy even without contrast oxidation of the copper film, representing a quick and reliable method for their identification. Slow-etching of the graphene yielded well-aligned, hexagonal domains further indicating the high-quality, single-crystalline of the graphene.

  • 30.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Karabulut, Erdem
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tran, Amy
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Tom
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Transparent Nanocellulosic Multilayer Thin Films on Polylactic Acid with Tunable Gas Barrier Properties2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, Vol. 5, no 15, 7352-7359 p.Article in journal (Refereed)
    Abstract [en]

    The layer-by-layer (LbL) deposition method was used for the build-up of alternating layers of nanofibrillated cellulose (NFC) or carboxymethyl cellulose (CMC) with a branched, cationic polyelectrolyte, polyethyleneimine (PEI) on flexible poly (lactic acid) (PLA) substrates. With this procedure, optically transparent nanocellulosic films with tunable gas barrier properties were formed. 50 layer pairs of PEI/NFC and PEI/CMC deposited on PLA have oxygen permeabilities of 0.34 and 0.71 cm(3).mu m/m(2).day.kPa at 23 degrees C and 50% relative humidity, respectively, which is in the same range as polyvinyl alcohol and ethylene vinyl alcohol. The oxygen permeability of these multilayer nanocomposites outperforms those of pure NFC films prepared by solvent-casting. The nanocellulosic LbL assemblies on PLA substrates was in detailed characterized using a quartz crystal microbalance with dissipation (QCM-D). Atomic force microscopy (AFM) reveals large structural differences between the PEI/NFC and the PEI/CMC assemblies, with the PEI/NFC assembly showing a highly entangled network of nanofibrils, whereas the PEI/CMC surfaces lacked structural features. Scanning electron microscopy images showed a nearly perfect uniformity of the nanocellulosic coatings on PLA, and light transmittance results revealed remarkable transparency of the LbL-coated PLA films. The present work demonstrates the first ever LbL films based on high aspect ratio, water-dispersible nanofibrillated cellulose, and water-soluble carboxymethyl cellulose polymers that can be used as multifunctional films and coatings with tailorable properties, such as gas barriers and transparency. Owing to its flexibility, transparency and high-performance gas barrier properties, these thin film assemblies are promising candidates for several large-scale applications, including flexible electronics and renewable packaging.

  • 31.
    Austrell, Per-Erik
    et al.
    Division of Structural Mechanics, Lund Institute of Technology.
    Kari, LeifKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Constitutive Models for Rubber IV: proceedings of the 4th European Conference for Constitutive Models for Rubber, ECCMR 2005, Stockholm, Sweden, 27-29 June 20052005Collection (editor) (Refereed)
    Abstract [en]

    The unique properties of elastomeric materials are taken advantage of in many engineering applications. Elastomeric units are used as couplings or mountings between stiff parts. Examples are shock absorbers, vibration insulators, flexible joints, seals and suspensions etc.

     

    However, the complicated nature of the material behavior makes it difficult to accurately predict the performance of these units, using for example finite element modelling. It is therefore necessary that the constitutive model accurately capture relevant aspects of the mechanical behavior.

     

    The latest development concerning constitutive modelling of rubber is collected in these proceedings. It is the fourth ECCMR-European Conference on Constitutive Modelling in a series on this subject.

     

    Topics included in this volume are, Hyperelastic models, Strength, fracture & fatigue, Dynamic properties & the Fletcher-Gent effect, Micro-mechanical & statistical approaches, Stress softening, Viscoelasticity, Filler reinforcement, and Tyres, fiber & cord reinforced rubber.

  • 32. Aziz, F.
    et al.
    Ouazzani, N.
    Mandi, L.
    Muhammad, M.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Uheida, Abdusalam
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Composite nanofibers of polyacrylonitrile/natural clay for decontamination of water containing Pb(II), Cu(II), Zn(II) and pesticides2017In: Separation science and technology (Print), ISSN 0149-6395, E-ISSN 1520-5754, Vol. 52, no 1, 58-70 p.Article in journal (Refereed)
    Abstract [en]

    Composite nanofibers containing polyacrylonitrile and natural clay particles were fabricated and investigated for the removal of Pb(II), Cu(II) and Zn(II) from aqueous solutions. The adsorption behavior of Pb(II), Cu(II) and Zn(II) can be well described by the Langmuir adsorption model and high loading capacities at pH 7 were obtained. The kinetics of the adsorption process showed that equilibrium was attained after 60 min and the experimental data followed a pseudo-first-order model. The nanocomposites were also tested for photocatalytic degradation of Monocrotophos pesticides in which high degradation efficiency (>90%) was obtained in less than 60 min.

  • 33. Bacsa, W. S.
    et al.
    Dutta, Joydeep
    Vibrational Raman spectroscopy of silicon powders produced by plasma enhanced chemical vapor deposition1995In: Analusis, Vol. 23, no 10, 531-532 p.Article in journal (Refereed)
  • 34.
    Baghban, Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Schollhammer, Jean
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Waveguide Gratings in Thin-Film Lithium Niobate on Insulator2017In: CLEO: 2017, OSA Technical Digest, Optical Society of America, 2017Conference paper (Refereed)
  • 35.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Impact of longitudinal fields on second harmonic generation in lithium niobate nanopillars2016In: APL Photonics, ISSN 2378-0967, Vol. 01, no 06, 061302Article in journal (Refereed)
    Abstract [en]

    An optimized focused ion beam process is used to fabricate micrometer-long LiNbO3 nanopillars with diameters varying between 150 and 325 nm. Polarimetric mappings of second harmonic generation from a wavelength of 850 nm demonstrate the ability to modify the polarization features of the nonlinearresponse through a fine adjustment of the pillar size. The effect is ascribed to the non-negligible contribution of the longitudinal fields associated with sub-wavelength light confinement in the LiNbO3nanopillars. The results also highlight the importance of a fine control over the nanopillar size in order to effectively engineer their nonlinear response.

  • 36. Bahramirad, S.
    et al.
    Atallah, Jad G.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Albrecht, S.
    A low phase noise VCO for multi band wireless transceivers2007In: Proceedings - 2007 International Conference on Design and Technology of Integrated Systems in Nanoscale Era, DTIS 2007, IEEE , 2007, 148-153 p.Conference paper (Refereed)
    Abstract [en]

    this paper presents a CMOS voltage controlled oscillator for multi standard wireless transceivers. The VCO structure is based on All- PMOS LC oscillators. The frequency range extends from 1.7 GHz to 2.5 GH, and tuning between frequencies is done by means of capacitor banks and varactors.

  • 37. Banerjee, S.
    et al.
    Sarkar, S.
    Lakshman, K.
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University, P.O. Box 17, 123 Al-Khoudh, Oman.
    Pal, S. K.
    UVA radiation induced ultrafast electron transfer from a food carcinogen benzo[a]pyrene to organic molecules, biological macromolecules, and inorganic nano structures2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 14, 3726-3737 p.Article in journal (Refereed)
    Abstract [en]

    Reactions involving electron transfer (ET) and reactive oxygen species (ROS) play a pivotal role in carcinogenesis and cancer biochemistry. Our present study emphasizes UVA radiation induced ET reaction as one of the key aspects of a potential carcinogen, benzo[a]pyrene (BP), in the presence of a wide variety of molecules covering organic p-benzoquinone (BQ), biological macromolecules like calf-thymus DNA (CT-DNA), human serum albumin (HSA) protein, and inorganic zinc oxide (ZnO) nanorods (NRs). Steady-state and picosecond-resolved fluorescence spectroscopy have been used to monitor such ET reactions. Physical consequences of BP association with CT-DNA have been investigated through temperature-dependent circular dichroism (CD) spectroscopy. The temperature-dependent steady-state, picosecond-resolved fluorescence lifetime and anisotropy studies reveal the effect of temperature on the perturbation of such ET reactions from BP to biological macromolecules, highlighting their temperature-dependent association. Furthermore, the electron-donating property of BP has been corroborated by measuring wavelength-dependent photocurrent in a BP-anchored ZnO NR-based photodevice, offering new physical insights for the carcinogenic study of BP.

  • 38. Bansal, Akshaya
    et al.
    Liu, Haichun
    Jayakumar, Muthu Kumara Gnanasammandhan
    Andersson-Engels, Stefan
    Zhang, Yong
    Quasi-Continuous Wave Near-Infrared Excitation of Upconversion Nanoparticles for Optogenetic Manipulation of C. elegans2016In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 12, no 13, 1732-1743 p.Article in journal (Refereed)
    Abstract [en]

    Optogenetics is an emerging powerful tool to investigate workings of the nervous system. However, the use of low tissue penetrating visible light limits its therapeutic potential. Employing deep penetrating near-infrared (NIR) light for optogenetics would be beneficial but it cannot be used directly. This issue can be tackled with upconversion nanoparticles (UCNs) acting as nanotransducers emitting at shorter wavelengths extending to the UV range upon NIR light excitation. Although attractive, implementation of such NIR-optogenetics is hindered by the low UCN emission intensity that necessitates high NIR excitation intensities, resulting in overheating issues. A novel quasi-continuous wave (quasi-CW) excitation approach is developed that significantly enhances multiphoton emissions from UCNs, and for the first time NIR light-triggered optogenetic manipulations are implemented in vitro and in C. elegans. The approach developed here enables the activation of channelrhodopsin-2 with a significantly lower excitation power and UCN concentration along with negligible phototoxicity as seen with CW excitation, paving the way for therapeutic optogenetics.

  • 39.
    Banuazizi, Seyed Amir Hossein
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Sani, Sohrab R.
    Eklund, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Naiini, Maziar M.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Mohseni, Seyed Majid
    Chung, Sunjae
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Univ Gothenburg, Sweden.
    Durrenfeld, Philipp
    Malm, B. Gunnar
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Univ Gothenburg, Sweden.
    Order of magnitude improvement of nano-contact spin torque nano-oscillator performance2017In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 5, 1896-1900 p.Article in journal (Refereed)
    Abstract [en]

    Spin torque nano-oscillators (STNO) represent a unique class of nano-scale microwave signal generators and offer a combination of intriguing properties, such as nano sized footprint, ultrafast modulation rates, and highly tunable microwave frequencies from 100 MHz to close to 100 GHz. However, their low output power and relatively high threshold current still limit their applicability and must be improved. In this study, we investigate the influence of the bottom Cu electrode thickness (t(Cu)) in nano-contact STNOs based on Co/Cu/NiFe GMR stacks and with nano-contact diameters ranging from 60 to 500 nm. Increasing t(Cu) from 10 to 70 nm results in a 40% reduction of the threshold current, an order of magnitude higher microwave output power, and close to two orders of magnitude better power conversion efficiency. Numerical simulations of the current distribution suggest that these dramatic improvements originate from a strongly reduced lateral current spread in the magneto-dynamically active region.

  • 40. Barrefelt, Åsa
    et al.
    Saghafian, Maryam
    Kuiper, Raoul
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Egri, Gabriella
    Klickermann, Moritz
    Brismar, Torkel B.
    Aspelin, Peter
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Daehne, Lars
    Hassan, Moustapha
    Biodistribution, kinetics, and biological fate of SPION microbubbles in the rat2013In: International Journal of Nanomedicine, ISSN 1176-9114, E-ISSN 1178-2013, Vol. 8, 3241-3254 p.Article in journal (Refereed)
    Abstract [en]

    Background: In the present investigation, we studied the kinetics and biodistribution of a contrast agent consisting of poly(vinyl alcohol) (PVA) microbubbles containing superparamagnetic iron oxide (SPION) trapped between the PVA layers (SPION microbubbles). Methods: The biological fate of SPION microbubbles was determined in Sprague-Dawley rats after intravenous administration. Biodistribution and elimination of the microbubbles were studied in rats using magnetic resonance imaging for a period of 6 weeks. The rats were sacrificed and perfusion-fixated at different time points. The magnetic resonance imaging results obtained were compared with histopathologic findings in different organs. Results: SPION microbubbles could be detected in the liver using magnetic resonance imaging as early as 10 minutes post injection. The maximum signal was detected between 24 hours and one week post injection. Histopathology showed the presence of clustered SPION microbubbles predominantly in the lungs from the first time point investigated (10 minutes). The frequency of microbubbles declined in the pulmonary vasculature and increased in pulmonary, hepatic, and splenic macrophages over time, resulting in a relative shift from the lungs to the spleen and liver. Meanwhile, macrophages showed increasing signs of cytoplasmic iron accumulation, initially in the lungs, then followed by other organs. Conclusion: The present investigation highlights the biological behavior of SPION microbubbles, including organ distribution over time and indications for biodegradation. The present results are essential for developing SPION microbubbles as a potential contrast agent and/or a drug delivery vehicle for specific organs. Such a vehicle will facilitate the use of multimodality imaging techniques, including ultrasound, magnetic resonance imaging, and single positron emission computed tomography, and hence improve diagnostics, therapy, and the ability to monitor the efficacy of treatment.

  • 41. Barua, S
    et al.
    Dutta, Joydeep
    Sultan Qaboos University, Sultanate of Oman.
    Liquified Petroleum Gas Sensing using Microballs of ZnO2013In: lndian ]ournal of Science and Technology, ISSN 0974-6846, Vol. 6, no S3, 190-193 p.Article in journal (Refereed)
    Abstract [en]

    Liquefied petroleum gas (LPG) is extensively used in households and industries. It is a combustible gas and leakages can lead toexplosions. It is also toxic and exposure to it above a certain level can be fatal and as such real time monitoring and accidentalleakage detection is crucial. Metal oxide semiconductors are known for their gas sensing property. Spherical microstructures ofZnO, a wide band gap semiconductor, were synthesized following a simple hydrothermal route. Thin films of these microsphereswere used to detect LPG down to 1000 ppm by observing the change in electrical resistance. Platinum (Pt) nanoparticles weredeposited on the sensing mediurn as a catalyst to improve the performance of the sensors. Maximum response of 55.8% wasachieved for 5000 ppm ofLPG at 250oC.

  • 42. Baruah, S.
    et al.
    Dutta, J.
    Centre of Excellence in Nanotechnology, Asian Institute of Technology,Thailand.
    Hydrothermal growth of ZnO nanostructures2009In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 10, no 1Article in journal (Refereed)
    Abstract [en]

    One-dimensional nanostructures exhibit interesting electronic and optical properties due to their low dimensionality leading to quantum confinement effects. ZnO has received lot of attention as a nanostructured material because of unique properties rendering it suitable for various applications. Amongst the different methods of synthesis of ZnO nanostructures, the hydrothermal method is attractive for its simplicity and environment friendly conditions. This review summarizes the conditions leading to the growth of different ZnO nanostructures using hydrothermal technique. Doping of ZnO nanostructures through hydrothermal method are also highlighted.

  • 43. Baruah, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Effect of seeded substrates on hydrothermally grown ZnO nanorods2009In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 50, no 3, 456-464 p.Article in journal (Refereed)
    Abstract [en]

    We report a study on the effect of seeding on glass substrates with zinc oxide nanocrystallites towards the hydrothermal growth of ZnO nanorods from a zinc nitrate hexahydrate and hexamethylenetetramine solution at 95 °C. The seeding was done with pre-synthesized ZnO nanoparticles in isopropanol with diameters of about 6–7 nm as well as the direct growth of ZnO nanocrystallites on the substrates by the hydrolysis of pre-deposited zinc acetate film. The nanorods grown on ZnO nanoparticle seeds show uniform dimensions throughout the substrate but were not homogenously aligned vertically from the substrate and appeared like nanoflowers with nanorod petals. Nanorods grown from the crystallites formed in situ on the substrates displayed wide variations in dimension depending upon the preheating and annealing conditions. Annealing the seed crystals below 350 °C led to scattered growth directions whereupon preferential orientation of the nanorods perpendicular to the substrates was observed. High surface to volume ratio which is vital for gas sensing applications can be achieved by this simple hydrothermal growth of nanorods and the rod height and rod morphology can be controlled through the growth parameters.

  • 44. Baruah, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Nanotechnology applications in pollution sensing and degradation in agriculture2009In: Environmental Chemistry Letters, ISSN 1610-3653, E-ISSN 1610-3661, Vol. 7, no 3, 191-204 p.Article in journal (Refereed)
    Abstract [en]

    With the rise in the global population, the demand for increased supply of food has motivated scientists and engineers to design new methods to boost agricultural production. With limited availability of land and water resources, growth in agriculture can be achieved only by increasing productivity through good agronomy and supporting it with an effective use of modern technology. Advanced agronomical methods lay stress not only on boosting agricultural produce through use of more effective fertilizers and pesticides, but also on the hygienic storage of agricultural produce. The detrimental effects of modern agricultural methods on the ecosystem have raised serious concerns amongst environmentalists. The widespread use of persistent pesticides globally over the last six decades has contaminated groundwater and soil, resulting in diseases and hardships in non-target species such as humans and animals. The first step in the removal of disease causing microbes from food products or harmful contaminants from soil and groundwater is the effective detection of these damaging elements. Nanotechnology offers a lot of promise in the area of pollution sensing and prevention, by exploiting novel properties of nanomaterials. Nanotechnology can augment agricultural production and boost food processing industry through applications of these unique properties. Nanosensors are capable of detecting microbes, humidity and toxic pollutants at very minute levels. Organic pesticides and industrial pollutants can be degraded into harmless and often useful components, through a process called photocatalysis using metal oxide semiconductor nanostructures. Nanotechnology is gradually moving out from the experimental into the practical regime and is making its presence felt in agriculture and the food processing industry. Here we review the contributions of nanotechnology to the sensing and degradation of pollutants for improved agricultural production with sustainable environmental protection.

  • 45. Baruah, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    pH-dependent growth of zinc oxide nanorods2009In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 8, 2549-2554 p.Article in journal (Refereed)
    Abstract [en]

    Here we study the effect of pH variation on the dimension and morphology of zinc oxide (ZnO) nanorods grown through hydrothermal process at temperatures less than 100 °C. ZnO nanorods were grown on pre-seeded glass substrates using zinc nitrate hexahydrate as the source of Zn ions and hexamethylenetetramine as the source of hydroxyl ions. The pH of the reaction bath was found to change gradually from 6.4 to 7.3 in 5 h during the growth process. The growth of the ZnO nanorods was observed to be faster, both laterally and longitudinally, when the growth solution was in basic conditions. However, flower petal like ZnO nanostructures were obtained when the growth process was initiated in basic condition (pH 8–12), indicating that initial acidic conditions were required to obtain nanorods with well-defined hexagonal facets. ZnO is known to erode in acidic condition and the final dimension of the nanorods is determined by a competition between crystal growth and etching. ZnO nanorods of different dimensions, both laterally (diameters ranging from 220 nm to 1 μm) and longitudinally (lengths ranging from 1 to 5.6 μm) were successfully synthesized using the same concentration of zinc nitrate and hexamine in the reaction bath and the same growth duration of 5 h simply through appropriate control of the pH of the reactant solution between 6 and 7.3.

  • 46. Baruah, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Zinc stannate nanostructures: Hydrothermal synthesis2011In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 12, no 1Article in journal (Refereed)
    Abstract [en]

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature.

  • 47. Baruah, S.
    et al.
    Jaisai, M.
    Imani, R.
    Nazhad, M. M.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Photocatalytic paper using zinc oxide nanorods2010In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 11, no 5Article in journal (Refereed)
    Abstract [en]

    Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm–2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions.

  • 48. Baruah, S.
    et al.
    Pal, S. K.
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University, P. O. Box 17, Al-Khoudh123, Oman.
    Nanostructured zinc oxide for water treatment2012In: Nanoscience and Nanotechnology - Asia, ISSN 2210-6812, Vol. 2, no 2, 90-102 p.Article in journal (Refereed)
    Abstract [en]

    Environmental pollution and industrialization on a global scale have drawn attention to the vital need for developing new hygienically friendly purification technologies. Existing wastewater treatment technologies demand high capital investment and operation &amp; maintenance cost, and large area. Cost-effective treatment of pollutants requires the transformation of hazardous substances into benign forms and the subsequent development of effective risk management strategies from harmful effects of pollutants that are highly toxic, persistent, and difficult to treat. Application of nanotechnology that results in improved water treatment options might include removal of the finest contaminants from water (&lt; 300 nm) and "smart materials" or "reactive surface coatings" with engineered specificity to a certain pollutant that destroy, transform or immobilize toxic compounds. Nanomaterials have been gaining increasing interest in the area of environmental remediation mainly due to their enhanced surface and also other specific changes in their physical, chemical and biological properties that develop due to size effects. Heterogeneous photocatalytic systems via metal oxide semiconductors like TiO2 and ZnO, are capable of operating effectively and efficiently for waste water treatment which has been discussed along with other nanotechnology routes that can be useful for water treatments. Multifunctional photocatalytic membranes using ZnO nanostructures are considered advantageous over freely suspended nanoparticles due to the ease of its removal from the purified water. A short discussion on the study of charge transfer mechanisms during photocatalytic reactions has also been included.

  • 49. Baruah, S.
    et al.
    Rafique, R. F.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Visible light photocatalysis by tailoring crystal defections in zinc oxide nanostructures2008In: Nano, ISSN 1793-2920, Vol. 3, no 5, 399-407 p.Article in journal (Refereed)
    Abstract [en]

    The photocatalytic activity of zinc oxide (ZnO) nanoparticles, films and nanowires as a potential visible light photocatalyst is presented in this work. ZnO nanoparticles were synthesized in different alcoholic solvents. Crystal defects were introduced either by doping the crystallites with manganese or by fast crystallization (using microwave irradiation during synthesis). ZnO, with a band gap of 3.37 eV, normally absorbs electromagnetic waves in the ultraviolet region, but introducing defects into its crystal lattice can shift the absorption more toward the visible light band from 400 nm to 700 nm by creating intermediate states which inhibit electron-hole recombination. The undoped ZnO nanoparticles synthesized using microwaves showed comparable photocatalytic activities to the doped samples using the conventional heating method. To increase the effective surface area of the photocatalyst, ZnO nanowires were grown by a solution-based technique. Methylene blue degradation was observed to be enhanced in the presence of the ZnO nanowires compared to the ZnO nanoparticles. Intentional defect creation in photocatalysts could be an attractive possibility to apply in the visible light photocatalytic degradation studies.

  • 50. Baruah, S.
    et al.
    Sinha, S. S.
    Ghosh, B.
    Pal, S. K.
    Raychaudhuri, A. K.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technolo, Thailand.
    Photoreactivity of ZnO nanoparticles in visible light: Effect of surface states on electron transfer reaction2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 7Article in journal (Refereed)
    Abstract [en]

    Wide band gap metal oxide semiconductors such as zinc oxide (ZnO) show visible band photolysis that has been employed, among others, to degrade harmful organic contaminants into harmless mineral acids. Metal oxides show enhanced photocatalytic activity with the increase in electronic defects in the crystallites. By introducing defects into the crystal lattice of ZnO nanoparticles, we observe a redshift in the optical absorption shifting from the ultraviolet region to the visible region (400-700 nm), which is due to the creation of intermediate defect states that inhibit the electron hole recombination process. The defects were introduced by fast nucleation and growth of the nanoparticles by rapid heating using microwave irradiation and subsequent quenching during the precipitation reaction. To elucidate the nature of the photodegradation process, picosecond resolved time correlated single photon count (TCSPC) spectroscopy was carried out to record the electronic transitions resulting from the de-excitation of the electrons to their stable states. Photodegradation and TCSPC studies showed that defect engineered ZnO nanoparticles obtained through fast crystallization during growth lead to a faster initial degradation rate of methylene blue as compared to the conventionally synthesized nanoparticles.

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