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  • 1.
    Afrasiabi, Roodabeh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Shahid, Robina
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Microwave mediated synthesis of semiconductor quantum dots2012Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, nr 7, s. 1551-1556Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    Dong, Lin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Pinos, Andrea
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. Helsinki University of Technology, Finland.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Measurement of radiative lifetime in CdSe/CdS core/shell structured quantum dots2009Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009, s. 5377385-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Radiative lifetime of chemically synthesized colloidal CdSe/CdS core/shell quantum dots is measured. Influence of the core size on the electron-hole pair separation is analyzed. A long radiative lifetime and the existence of electron-hole pair separation suggest high potential of these dots as gain material to achieve lasing under continuous-wave excitation.

  • 3.
    Dong, Lin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Hu, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Zhou, Sicheng
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots2013Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 52, nr 1, s. 105-109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.

  • 4.
    Fornara, Andrea
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Recalenda, Alberto
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fei, Ye
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Laurent, Sophie
    University of Mons.
    Muller, Robert
    University of Mons.
    Zou, Jing
    University of Tampere.
    Usama, Abo-RAmadan
    University of Helsinki.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Polymeric/inorganic multifunctional nanoparticles for simultaneous drug delivery and visualization2010Ingår i: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 1257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanoparticles consisting of different biocompatible materials are attracting a lot of interest in the biomedical area as useful tools for drug delivery, photo-therapy and contrast enhancement agents in MRI, fluorescence and confocal microscopy. This work mainly focuses on the synthesis of polymeric/inorganic multifunctional nanoparticles (PIMN) based on biocompatible di-block copolymer poly(L,L-lactide-co-ethylene glycol) (PLLA-PEG) via an emulsion-evaporation method. Besides containing a hydrophobic drug (Indomethacin), these polymeric nanoparticles incorporate different visualization agents such as superparamagnetic iron oxide nanoparticles (SPION) and fluorescent Quantum Dots (QDs) that are used as contrast agents for Magnetic Resonance Imaging (MRI) and fluorescence microscopy together. Gold Nanorods are also incorporated in such nanostructures to allow simultaneous visualization and photodynamic therapy. MRI studies are performed with different loading of SPION into PIMN, showing an enhancement in T2 contrast superior to commercial contrast agents. Core-shell QDs absorption and emission spectra are recorded before and after their loading into PIMN. With these polymeric/inorganic multifunctional nanoparticles, both MRI visualization and confocal fluorescence microscopy studies can be performed. Gold nanorods are also synthesized and incorporated into PIMN without changing their longitudinal absorption peak usable for lased excitation and phototherapy. In-vitro cytotoxicity studies have also been performed to confirm the low cytotoxicity of PIMN for further in-vivo studies.

  • 5.
    Lobov, Gleb S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Zhao, Yichen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Marinins, Aleksandrs
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Li, Jiantong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Thylen, Lars
    KTH, Skolan för bioteknologi (BIO).
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Ostling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy2016Ingår i: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 217, nr 9, s. 1089-1095Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofi bers and is referred to as alternating current poling method. P3HT nanofi bers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 mu m long nanofi bers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V mu m(-1), while 100-500 nm long nanofi bers respond to electric field negligibly. Effective optical birefringence of oriented 2 mu m long nanofi bers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofi bers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.

  • 6. Rihtnesberg, D. B.
    et al.
    Almqvist, S.
    Wang, Q.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Yang, Xuran
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Besharat, Zahra
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Materialfysik, MF (Stängd 20120101).
    ZnO nanorods/nanoflowers and their applications2011Ingår i: Proc. - Int. NanoElectronics Conf., INEC, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Single-crystalline zinc oxide (ZnO) nanorods (NRs) have been synthesized through a chemical bath deposition method. Their diameter is about 80 nm, and their length range from 1 μm to 7 μm can be controlled by growth time. Formation of nanoflower arrays composed of nanorods has been also achieved utilizing a standard micro-fabrication technique. Two types of ZnO nanorods devices are detailed to demonstrate their optoelectronic applications.

  • 7.
    Shahid, Robina
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Gorlov, Mikhail
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    El-Sayed, Ramy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Microwave assisted synthesis of ZnS quantum dots using ionic liquids2012Ingår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 89, s. 316-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we report results from microwave (MW) assisted synthesis of highly crystalline ZnS quantum dots (QDs) using ionic liquid (ILs) as MW absorbing medium. Two types of ionic liquids, imidazolium and phosphonium based, were used. The QDs are less than 5 nm in size and of wurtzite ZnS type, as characterized by high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) pattern. The optical properties were investigated by UV-vis absorption and show a blue shift in absorption as compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of the QDs show different trap state emissions.

  • 8.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors.

    We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable.

    We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers).

    In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating.

  • 9.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Photochemical and Photoelectric Applications of II-VI Semiconductor Nanomaterials2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated two different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdTe nanotetrapods synthesized by solution-based thermal decomposition of organo-metallic precursors. In both the cases our main focus has been optimizing material synthesis for improving potential applications based on photon-electron interactions.

    We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. The synthesis is based on epitaxial growth of ZnO seed-layer on a substrate in a chemical bath consisting of an aqueous solution of zinc nitrate and hexamethylenetetramine (HMT). We have suggested an additional role played by HMT during the synthesis of ZnO nanowire arrays. We have also extended this synthesis method to fabricate hierarchical nanostructures of nanofibers of poly-L-lactide acting as a substrate for the radially oriented growth of ZnO nanowires. The combination of high surface area of the nanofibrous substrate with the flexibility of the PLLA-ZnO hierarchical nanostructure enabled the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system that could effectively decompose single and combination of known organic pollutants in water, as well as render common waterborne bacteria nonviable.

    We have studied another chemical synthesis that is commonly used for size controlled synthesis of colloidal quantum dots, which was modified to obtain anisotropic nanocrystals mainly for CdE (E=S, Se, Te) compositions. In this work we demonstrate by use of oleic acid (instead of alkylphosphonic acids) it is possible to synthesize CdTe and CdSe nanotetrapods at much lower temperatures (~180 ºC) than what is commonly reported in the literature, with significantly different  formation mechanism in the low-temperature reaction.

    Finally, we have performed preliminary photoconduction measurements with CdTe nanotetrapods using gold ‘nanogap’ electrodes fabricated in-house, and obtain up to 100 times enhancement in current levels in the I–V measurements under illumination with a white light source.

  • 10.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Guduru, Veerendra K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    A ‘Continuous flow’ Photochemical Water Treatment System Based on Radially Oriented ZnO Nanowires on Flexible Poly-L-Lactide NanofibersManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Several oxide ceramics, notably ZnO and TiO2 are known to catalyze decomposition of organic molecules in water under ultra-violet irradiation. Here we describe fabrication of highly flexible ZnO-based hierarchical nanostructure obtained by growing radially oriented ZnO nanowires on poly-L-lactide nanofibers. Utilizing the flexibility and high surface area of polymeric nanofibers as novel ‘substrate’ for growth of the photochemically active ZnO nanowires we show a proof-of-principle demonstration of a ‘continuous flow’ water treatment set-up. We have monitored photocatalytic decomposition of known organic pollutants, such as methylene blue, monocrotophos and diphenylamine under illumination with ultraviolet light using this highly flexible hierarchical nanostructure.

  • 11.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Guduru, Veerendra K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Radially Oriented ZnO Nanowires on Flexible Poly-L-Lactide Nanofibers for Continuous-Flow Photocatalytic Water Purification2010Ingår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 93, nr 11, s. 3740-3744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several oxide ceramics, notably ZnO and TiO2 are known to catalyze decomposition of organic molecules in water under ultraviolet (UV) irradiation. Here we describe fabrication of highly flexible ZnO-based hierarchical nanostructure obtained by growing radially oriented ZnO nanowires on poly-L-lactide nanofibers. Utilizing the flexibility and high surface area of polymeric nanofibers as novel substrate for growth of the photochemically active ZnO nanowires we show a proof-of-principle demonstration of a continuous flow water treatment setup. We have monitored photocatalytic decomposition of known organic pollutants, such as methylene blue, monocrotophos, and diphenylamine under illumination with UV light using this highly flexible hierarchical nanostructure.

  • 12.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Jafri, S. Hassan M.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Blom, Tobias
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Leifer, Klaus
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Low-temperature synthesis of photoconducting CdTe nanotetrapods2010Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, nr 6, s. 1208-1214Artikel i tidskrift (Refereegranskat)
  • 13. Sugunan, Abhilash
    et al.
    Warad, Hemant C.
    Boman, Mats
    Dutta, Joydeep
    Zinc oxide nanowires in chemical bath on seeded substrates: Role of hexamine2006Ingår i: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 39, nr 1, s. 49-56Artikel i tidskrift (Refereegranskat)
  • 14.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhao, Yichen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Mitra, Somak
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Dong, Lin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Marcinkevicius, Saulius
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis of tetrahedral quasi-type-II CdSe-CdS core-shell quantum dots2011Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, nr 42, s. 425202-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesis of colloidal nanocrystals of II-VI semiconductor materials has been refined in recent decades and their size dependent optoelectronic properties have been well established. Here we report a facile synthesis of CdSe-CdS core-shell heterostructures using a two-step hot injection process. Red-shifts in absorption and photoluminescence spectra show that the obtained quantum dots have quasi-type-II alignment of energy levels. The obtained nanocrystals have a heterostructure with a large and highly faceted tetrahedral CdS shell grown epitaxially over a spherical CdSe core. The obtained morphology as well as high resolution electron microscopy confirms that the tetrahedral shell have a zinc blende crystal structure. A phenomenological mechanism for the growth and morphology of the nanocrystals is discussed.

  • 15.
    Toprak, Muhammet S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Vogt, Carmen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Active Cooperative Assemblies Towards Nanocomposites2009Ingår i: ADVANCES IN MATERIAL DESIGN FOR REGENERATIVE MEDICINE, DRUG DELIVERY AND TARGETING/IMAGING    / [ed] Shastri VP; Lendlein A; Liu L; Mikos A; Mitragotri S, 2009, Vol. 1140, s. 197-202Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work reports on the fabrication of novel type of assemblies bearing magnetic nanoparticles and inorganic shells prepared via a biomimetic route of complex coacervation. Magnetic nanoparticles fabricated under controlled conditions were surface modified with polyacrylic acid (PAA). Subsequently, PAA spontaneously formed spherical assemblies in contact with certain ions, such as Ca2+. The stability of these microspheres against environmental alterations such as pH, ionic strength, and dilution was increased through cross-linking. Ethylene diammine (EDA) was used as a cross-linker, which resulted in mechanically stabilized system that does not show sensitivity towards the external pH values. Important parameters for the formation of these coacervates as well as mechanism of formation and cross-linking have been evaluated by FTIR analysis. The cooperative assemblies are still active for further reaction and were used for the growth of an inorganic aluminum oxide shell. SEM analysis of these spheres showed that the structures are hollow with a large interior volume. A biocompatible outer surface combined with the magnetic functionality is very important for the targeted drug delivery devices for biomedical applications.

  • 16. Wang, Q.
    et al.
    Rihtnesberg, D. B.
    Bergström, A.
    Almqvist, S.
    Zhang, A. Z. Z.
    Kaplan, W.
    Andersson, J. Y.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Yang, Xuran
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Compacted nanoscale sensors by merging ZnO nanorods with interdigitated electrodes2011Ingår i: Proc SPIE Int Soc Opt Eng, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    ZnO nanorods (NRs) sensors utilizing hybrid or monolithic integration of the NRs on nanoscale or microscale interdigitated electrodes (IDEs) were fabricated and characterized. The IDEs with their finger electrode width ranging from 50 nm to 3 μm were formed on SiO2/Si substrates by nanoimprint lithography or conventional photolithography and metallization techniques, whereas the ZnO NRs were grown by chemical synthesis method. The average diameter of the ZnO NRs is about 100 nm, and their length can be varied from 2 to 5 μm by controlling growth time. When sensing targets, such as molecules or nanoparticles, bind onto the ZnO NRs, the conductance between IDEs will change. As probing test, II-VI quantum dots (QDs) were attached on the ZnO NRs, and clear responses were obtained by measuring and comparing current-voltage (I-V) characteristic of the sensor before and after binding the QDs.

  • 17.
    Wang, Xiaodi
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis of uniform quasi-octahedral CeO2 mesocrystals via a surfactant-free route2011Ingår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, nr 11, s. 5879-5885Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A facile surfactant-free nonaqueous method is presented to prepare uniform quasi-octahedral ceria, CeO 2 , mesocrystals, in which only Ce(NO 3 ) 3 and octanol were used as the reactants at a reaction temperature of 150 °C. CeO 2 sample synthesized using this technique consists of well-dispersed quasi-octahedrons and exhibits an uniform size and morphology. Based on structural characterization, it is proposed that the CeO 2 mesostructure was formed by self-assembly of primary nanocrystals based on unique 3D oriented-attachment mechanism. Optical characterization exhibited a strong quantum confinement, revealing small size of primary nanocrystals. The thermal stability and UV–Vis study reveal CeO 2 mesocrystal has various potential for high temperature applications and optical apparatus applications.

  • 18.
    Ye, Fei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Vallhov, Helen
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institute and University Hospital Solna, Sweden.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Daskalaki, Evangelia
    Clinical Allergy Research Unit, Department of Medicine, Karolinska Institutet and Universty Hospital Solan, Sweden.
    abhilash, Sugunan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fornara, Andrea
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, 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, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis of high aspect ratio gold nanorods and their effects on human antigen presenting dendritic cells2011Ingår i: International Journal Of Nanotechnology, ISSN 1475-7435, Vol. 8, nr 8-9, s. 631-652Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    Zhao, Yichen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Rihtnesberg, David B.
    Wang, Qin
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Size-tuneable synthesis of photoconducting poly-(3-hexylthiophene) nanofibres and nanocomposites2012Ingår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, nr 7, s. 1546-1550Artikel i tidskrift (Refereegranskat)
    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.

  • 20.
    Zhao, Yichen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF. SP Tech Res Inst Sweden, Chem Mat & Surfaces Unit, Sweden.
    Schmidt, Torsten
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Fornara, Andrea
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Relaxation is the key to longer life: suppressed degradation of P3HT films on conductive substrates2014Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 33, s. 13270-13276Artikel i tidskrift (Refereegranskat)
    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.

1 - 20 av 20
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