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RISS 인기검색어
- 검색키워드
- 저자 : Santa Chawla (검색결과 5 건)
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White Light Emitting Magnetic ZnO:Sm Nanoparticles Prepared by Inclusive Co-Precipitation Synthesis
Santa Chawla,Monica Saroha,R.K. Kotnala 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1
Inclusion of rare earth Samarium as dopant in nanoparticles of ZnO has been achieved by co-precipitation in highly alkaline medium near room temperature. Substitutional doping of Sm in Zn position in the ZnO lattice could be inferred through change in lattice parameters in response to Sm doping concentration. Dopant Sm enhances broad visible emission of ZnO thus making it a bright white light emitter under UV (300 - 380 nm) excitation. Observation of room temperature intrinsic ferromagnetism with optimal Sm doping in ZnO:Sm suggests unpaired spin in Sm3+ at zinc substitutional sites could create spin ordering and long range ferromagnetic coupling. Such white light emitting magnetic nanoparticles of ZnO:Sm can have immense potential as LED phosphor and spin LED semiconductor.
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Synthesis and surface modification of ZnO:Cu nanoparticles by silica and PMMA
Bharti Choudhary,Santa Chawla,K. Jayanthi,K.N. Sood,Sukhvir Singh 한국물리학회 2010 Current Applied Physics Vol.10 No.3
ZnO nanoparticles doped with Cu were synthesized by solid state reaction using different precursor routes and varying growth environment. Average crystallite size varied from 40 to 100 nm depending upon synthesis temperature, lower temperature favouring smaller particle size. Scanning electron microscope (SEM) images showed that particles synthesized at 250 ℃ were in the shape of nanorods but those synthesized at 900 ℃ had spherical shape. Luminescence emission showed marked dependence on the growth conditions varying from ultraviolet (UV) emission to green emission. For making the luminescent nanoparticles bio-compatible, a bioinorganic interface on ZnO:Cu nanoparticles was created by coating them with inert silica. Surface modification of ZnO:Cu was also done with lipophilic polymethylmethacrylate (PMMA). ZnO:Cu nanoparticles showed hexagonal wurtzite structure and the coating of silica was confirmed with the presence of two extra peaks due to silica in the XRD spectra. Thermogravimetric analysis (TGA) and FTIR spectroscopy indicated that PMMA molecules were adsorbed on the surface of ZnO:Cu nanoparticles. SEM images revealed that PMMA adsorption improved the dispersibilty of ZnO:Cu nanoparticles.
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Electronic and Luminescent Characteristics of Aluminum Doped ZnO Nanocrystals
K. Jayanthi,Santa Chawla 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.1
Aluminium doped ZnO (AZO) nanocrystals were prepared under different ambient conditions (argon and air) to study the effect of structural, luminescence and electronic properties. AZO nanocrystals were highly crystallized in hexagonal wurtzite phase with spherical morphology. Prominent yellow emission is observed in both the AZO samples owing to recombination between Al3+ donor levels and intrinsic acceptor centre. Both AZO samples exhibit n-type conduction with resistivity of AZO prepared in inert (argon) ambient condition showing lower resistivity compared to the one synthesized in air atmosphere.
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Enhanced UV Emission in ZnO/ZnS Core Shell Nanoparticles Prepared by Epitaxial Growth in Solution
Simmi Sharma,Santa Chawla 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3
Co-precipitation in highly alkaline environment resulted in well crystalline ZnO nanoparticles over which ZnS shell was grown in situ in solution at room temperature. Formation of epitaxial hexagonal ZnS over wurtzite ZnO core particles have been confirmed by x-ray diffraction and transmission electron microscopy studies. The core ZnO nanoparticles show prominent UV emission which enhances appreciably due to ZnS shell formation in ZnO/ZnS core/shell particles. Experimental evidence indicates the quenching of non radiative recombination pathways due to shell formation. The results suggest that synthesized epitaxial core/shell particles have charge confinement mainly in the core region with type I characteristics of band alignment and can be useful for device applications.
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Red Upconversion Luminescence and Paramagnetism in Er/Yb Doped SnO2
Shweta Sharma,Jyoti Shah,R.K. Kotnala,Santa Chawla 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5
Red upconversion luminescence has been introduced in functional semiconductor SnO2 by doping rare earth ions Er3+ and Yb3+ and using 980 nm diode laser as pump source. High temperature solid state reaction leads to incorporation of trivalent lanthanide ions in SnO2. For high concentrations of lanthanide doping,partial reduction of Sn4+ to Sn2+ occurs for charge compensation making the material system SnO2-SnO alloy. Upconverting SnO2 exhibits paramagnetic characteristics with magnetization increasing with introduction of trivalent rare earth ions Er3+/Yb3+.
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