Synthesis, spectroscopy studies and applications of cadmium sulfide nanoparticles within MCM-41.
Item
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Title
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Synthesis, spectroscopy studies and applications of cadmium sulfide nanoparticles within MCM-41.
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Identifier
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AAI3169944
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identifier
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3169944
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Creator
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Liao, Yanting.
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Contributor
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Adviser: Daniel L. Akins
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical
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Abstract
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Cadmium sulfide nanoparticles have been successfully synthesized by the correspondent within both modified mesoporous aluminosilicate MCM-41 and siliceous SBA-15. The optical properties of the nanoparticles have been studied using XRD, UV-vis absorption, luminescence and Raman spectroscopies. Rigid chemically and thermally stable MCM-41 provides an ideal host for the nanoparticles synthesized therein, thus allowing the investigation of solvent effects on the optoelectronic properties of cadmium sulfide nanoparticles embedded in MCM-41 (referred to as CdS/MCM-41, hereinafter). The luminescence and photophysics of these nanoparticles were investigated by both steady-state and time-resolved emission spectroscopies. It was observed that the emission of cadmium sulfide nanoparticles in polar solvent produces a red shift with increases in excitation wavelength, which is similar to the "red-edge-excitation-shift" effect (REES). The origin of REES effect is due to the dipolar interaction of fluorophore with the polar solvent or media in both ground and excited states. Such strong interaction results in a decrease of the transition energy, leading to a red shift in emission. Also, for both protic and aprotic solvents, the emission maximum of US shifted to longer wavelengths with increases in the polarity of the solvent. The other rare property discovered for CdS/MCM-41 is its emission polarization. This property may be exploited in potential applications for biological labeling and probing. In studies reported here, the time-resolved fluorescence measurement provided rich information on the surface and solvent effects on the luminescent of cadmium sulfides nanoparticles. The quenching behavior of cadmium sulfides by methyl viologen and copper ions was found to exhibit solvent and surface charge carries effects, as well as a strong influence associated with the hosting environment of mesoporous materials. A linear temperature dependence was observed for the emission of CdS/MCM-41 (over the wide range, 77--298 K) suggests the potential application for luminescence nano-thermometry. The spontaneous formation of reduced methyl viologen radicals (MV+·) within mesoporous materials was observed in the presence of sulphide and MV2+ ions. In this case, the mesoporous material, MCM-41, works both as a micro-reactor and a catalyst. The catalytic reaction leading to MV+, a species whose location is determined by the optical absorption, provides a complementary means in combination with electron microscopy for probing the location of sulfide nanoparticles synthesized within the pores of mesoporous materials.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
