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  • 251.
    Ye, Fei
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Vallhov, Helen
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institute and University Hospital Solna, Sweden.
    Qin, Jian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Daskalaki, Evangelia
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institutet and Universty Hospital Solan, Sweden.
    abhilash, Sugunan
    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.
    Fornara, Andrea
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Gabrielsson, Susanne
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institutet and Universty Hospital Solan, Sweden.
    Scheynius, Annika
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institutet and Universty Hospital Solan, Sweden.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis of high aspect ratio gold nanorods and their effects on human antigen presenting dendritic cells2011In: International Journal Of Nanotechnology, ISSN 1475-7435, Vol. 8, no 8-9, p. 631-652Article in journal (Refereed)
    Abstract [en]

    High aspect ratio (AR) gold nanorods (NRs) attract great interest for biomedical applications due to their novel physicochemical properties. Here, we report a facile method for preparation of high AR gold NRs through a seedless surfactant-mediated protocol with the additive of nitric acid. High-resolution transmission electron microscopy studies showed that the concentration of nitric acid has great effects on the crystal structures of the initially formed nuclei and consequently the growth of gold NRs. A mechanism based on the effect of nitrate ions on surfactant micelle elongation and Ostwald ripening process is proposed for the growth of high AR gold NRs. The biocompatibility of high AR NRs was evaluated on primary human monocyte derived dendritic cells (MDDCs), and compared with that of spherical gold nanoparticles (NPs) and low AR NRs. Low AR (similar to 4.5) gold NRs induced considerable cell death due to CTAB, while spherical gold NPs (7 nm) and high AR (similar to 21) gold NRs showed no or minor effects on viability and immune regulatory markers, which supports the further development of high AR gold NRs for medical applications.

  • 252.
    Zhao, Wei
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Acreo Swedish ICT AB, Sweden.
    Zhao, Yichen
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Karlsson, Mikael
    Wang, Qin
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Evaluation of Zinc Oxide Nano-Microtetrapods for Biomolecule Sensing Applications2015In: MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS, SPIE - International Society for Optical Engineering, 2015, article id UNSP 966833Conference paper (Refereed)
    Abstract [en]

    Zinc oxide tetrapods (ZnO-Ts) were synthesized by flame transport synthesis using Zn microparticles. This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four nano-microstructured legs, of which the diameter of each leg is 0.7-2.2 mu m in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solution to study the luminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region decreased with linear dependence on the glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with a thin film of Nafion to form active layers on Si/SiO2/Au substrate for electrochemical glucose sensing. The attachment of GOx and the coating of Nafion onto ZnO-Ts were confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers based on ZnO-Ts was investigated by cyclic voltammetry (CV) in various glucose concentration conditions. Stable current response of glucose was detected with linear dependence on the glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.

  • 253.
    Zhao, Yichen
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Lobov, Gleb
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Sugunan, Abhilash
    Chemistry, Materials and Surfaces Unit, SP Technical Research Institute of Sweden.
    Karlsson, Mikael
    Department of Sensor system, Acreo Swedish ICT AB.
    Marinins, Aleksandrs
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Delekta, Szymon Sollami
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wang, Qin
    Department of Sensor system, Acreo Swedish ICT AB.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Electrical Field Induced Alignment of P3HT NanofibersManuscript (preprint) (Other academic)
    Abstract [en]

    Abstract: Poly 3-hexylthiophene (P3HT) is one of the most studied conjugated polymers for organic solar cell applications due to its light weight, flexible processing methods and low cost fabrication. However, the hole mobility in P3HT is still relatively low compared to that of the inorganic semiconductors, which is one of the main challenges to achieve better performance of organic solar cells. The P3HT nanofibers with aligned by inducing an external electric field have been studied to improve the hole mobility in P3HT nanofibers. Here we present an AC electric field (1.3 V/µm, 50 Hz) induced alignment of P3HT nanofibers with two different lengths. The optical absorption spectra of aligned nanofibers were measured under different polarizations of incident light. The longer nanofibers showed higher dichroic raitos than that of shorter nanofibers, revealing a better alignment pattern. The photoconductivity of non-aligned and aligned P3HT nanofibers were measured and compared, where the aligned P3HT nanofibers showed a ~270% higher dark current than that of non-aligned sample. Moreover, the current measured under the illumination showed ~110% enhancement in the aligned P3HT nanofibers while only ~70% enhancement was obseved in non-aligned nanofibers, revealing that the alignment process have the potential to improve the mobility for optoelectronic applications. 

  • 254.
    Zhao, Yichen
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Sugunan, A.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Synthesis of nanostructured antimony telluride for thermoelectric applications2015In: Materials Research Society Symposium Proceedings, Elsevier, 2015, Vol. 1742, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Thermoelectric (TE) materials have been studied during past decades since they can generate electricity directly from waste heat. Antimony chalcogenides (Sb2M3, M = S, Se, Te) are well known as one of the promising candidates among the inorganic TE materials. We report on the synthesis of Sb2Te3 nanoparticle via thermolysis method. A systematic study was done to investigate the effect of reaction time and ratio between the precursors as well as the method of cooling on the morphology and composition of obtained nanoparticles. The ratio between precursors was varied to study the effect on the morphology. Furthermore, the high purity phase Sb2Te3 was obtained by a rapid cooling process.

  • 255.
    Zhao, Yichen
    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.
    Rihtnesberg, David B.
    Wang, Qin
    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.
    Size-tuneable synthesis of photoconducting poly-(3-hexylthiophene) nanofibres and nanocomposites2012In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, no 7, p. 1546-1550Article in journal (Refereed)
    Abstract [en]

    Poly-(3-hexylthiophene) (P3HT) has been applied in many fields such as organic solar cells, printed electronic circuits, due to superior semiconducting properties compared to other semiconducting polymers. The presence of p-p interaction causes regio-regular P3HT to form ordered lamellar stacks during crystallisation. Here we report a simple room temperature, solution based method to synthesise P3HT nanofibres with controllable sizes. Our method is based on differing solubility of P3HT in various solvents. In a mixed solvent environment, we could control the precipitation of P3HT to obtain nanofibres with various diameters by varying the ratios of the solvents. We found that the lengths of the nanofibres could be controlled with concentration of the solution. Other methods to obtain nanofibres of P3HT invariably involves heating and controlled cooling which makes reproducibility and morphology control difficult. Furthermore, we synthesised a nanocomposite consisting of P3HT nanofibres and quasi-type-II quantum dots and evaluated the photoelectric properties of the nanofibres as well as the nanocomposites using interdigitated gold microelectrodes.

  • 256.
    Zhao, Yichen
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sugunan, Abhilash
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. SP Tech Res Inst Sweden, Chem Mat & Surfaces Unit, Sweden.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Fornara, Andrea
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Relaxation is the key to longer life: suppressed degradation of P3HT films on conductive substrates2014In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 33, p. 13270-13276Article in journal (Refereed)
    Abstract [en]

    Here we show the dependence of the degree of degradation of poly-3-hexylthiophene (P3HT) films on the conductivity of the supporting substrate. P3HT is widely used for organic solar cells and electronic devices because it allows simple, low cost fabrication and has potential for the fabrication of flexible devices. However, P3HT is known to have a relatively low photostability, and investigating the photodegradation mechanism is an active research field. We find that P3HT films on conductive substrates show significantly retarded degradation and retain their chemical and morphological features when compared to similar films on glass substrates. This 'substrate effect' in retarding the degradation of P3HT films is evident even upon prolonged exposure to air for up to five months.

  • 257.
    Zhao, Yichen
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Sugunan, Abhilash
    Wang, Qin
    Yang, Xuran
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Rihtnesberg, David B.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Direct Determination of Spatial Localization of Carriers in CdSe-CdS Quantum Dots2015In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, article id 321354Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dots (QDs) have gained significant attention due to their tunable band gap, simple solution processability, ease of scale-up, and low cost. By carefully choosing the materials, core-shell heterostructure QDs (HQDs) can be further synthesized with a controlled spatial spread of wave functions of the excited electrons and holes for various applications. Many investigations have been done to understand the exciton dynamics by optical characterizations. However, these spectroscopic data demonstrate that the spatial separation of the excitons cannot distinguish the distribution of excited electrons and holes. In this work, we report a simple and directmethod to determine the localized holes and delocalized electrons in HQDs. The quasi-type-II CdSe-CdS core-shell QDs were synthesized via a thermolysis method. Poly(3-hexylthiophene) (P3HT) nanofiber and ZnO nanorods were selected as hole and electron conductor materials, respectively, and were combined with HQDs to form two different nanocomposites. Photoelectrical properties were evaluated under different environments via a quick and facile characterization method, confirming that the electrons in the HQDs were freely accessible at the surface of the nanocrystal, while the holes were confined within the CdSe core.

  • 258.
    Zhou, Jian
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Soliman, Hesham M. A.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Platzek, Dieter
    Müller, Eckhard
    Synthesis and Seebeck coefficient of nanostructured phosphorus-alloyed bismuth telluride thick films2008In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 5, no 11, p. 3453-3457Article in journal (Refereed)
    Abstract [en]

    Phosphorous-alloyed Bi2Te3 thick films have been prepared by electrochemical deposition. The average grain size of the films was calculated to be 14-26 nm based on Scherrer's equation. The effect of P on the Seebeck coefficient of thermoelectric P-alloyed Bi2Te3 thick film was investigated. The results show that P-alloyed thick film has n-type conductivity with the Seebeck coefficient of -35 mu V/K. The correlation between P site occupancy in the crystal and the Seebeck coefficient was discussed.

  • 259.
    Zhou, Jie
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, Shuai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Soliman, Herrera M. A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Toprak, Muhammet S.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Platzek, D.
    Mueller, E.
    Seebeck coefficient of nanostructured phosphorus-alloyed bismuth telluride thick films2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 471, no 1-2, p. 278-281Article in journal (Refereed)
    Abstract [en]

    Nanostructured phosphorous-alloyed Bi2Te3 thick films have been prepared by electrochemical deposition. The average grain size of the films was calculated to be 14-26nm based on Scherrer's equation. The effect of P on the Seebeck coefficient of the Bi2Te3 thick film was investigated. The results show that P-alloyed thick film has n-type conductivity with the Seebeck coefficient of -35 mu V/K. The correlation between P site occupancy in the crystal and the Seebeck coefficient was discussed.

3456 251 - 259 of 259
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