tailieunhanh - Báo cáo hóa học: " Luminescence of colloidal CdSe/ZnS nanoparticles: high sensitivity to solvent phase transitions"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Luminescence of colloidal CdSe/ZnS nanoparticles: high sensitivity to solvent phase transitions | Antipov et al. Nanoscale Research Letters 2011 6 142 http content 6 1 142 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Luminescence of colloidal CdSe ZnS nanoparticles high sensitivity to solvent phase transitions 111 1 2 2 1 Andrei Antipov Matt Bell Mesut Yasar Vladimir Mitin William Scharmach Mark Swihart Aleksandr Verevkin Andrei Sergeev 1 Abstract We investigate nanosecond photoluminescence processes in colloidal core shell CdSe ZnS nanoparticles dissolved in water and found strong sensitivity of luminescence to the solvent state. Several pronounced changes have been observed in the narrow temperature interval near the water melting point. First of all the luminescence intensity substantially approximately 50 increases near the transition. In a large temperature scale the energy peak of the photoluminescence decreases with temperature due to temperature dependence of the energy gap. Near the melting point the peak shows N-type dependence with the maximal changes of approximately 30 meV. The line width increases with temperature and also shows N-type dependence near the melting point. The observed effects are associated with the reconstruction of ligands near the ice water phase transition. Optical methods for the characterization of phase transitions have attracted attention of many research groups as sensitive rapid and extremely effective technique which responds to small changes in crystallographic structures stress and local lattice distortions changes in stoichiometry and dislocations 1-3 . Variety of luminescence techniques such as thermoluminescence electroluminescence cathodoluminescence X-ray irradiation and ion beam luminescence can be used for excitation of luminescence 4 . A phase transition in bulk inevitably alters luminescence spectra line widths efficiency of excitation and recombination excited state lifetimes and polarization of emission bands. On the other hand the unique .

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