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ABSTRACT: This paper develops a facile solution-based method to synthesize hollow Cu(2-x) Te nanocrystals (NCs) with tunable interior volume based on the Kirkendall effect. Transmission electron microscopy images and time-dependent absorption spectra reveal the temporal growth process from solid copper nanoparticles to hollow Cu(2-x) Te NCs. Furthermore, the as-prepared hollow Cu(2-x) Te NCs show enhanced sensitivity for the detection of carbon monoxide (CO), which is often referred to as the "silent killer". The response and recovery time of the as-prepared sensor for the detection of 100 ppm CO gas are estimated to be about 21 and 100 s, respectively, which are sufficient to render it a promising candidate for effective CO gas-sensing applications. Such enhanced performance is achieved owing to the small grain size and large specific area of the hollow nanostructures. Therefore, the obtained hollow NCs based on the Kirkendall effect may have the potential as new functional blocks for high-performance gas sensors.
Small 11/2012; · 8.35 Impact Factor
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ABSTRACT: Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature.
Nanoscale 02/2011; 3(2):741-5. · 5.91 Impact Factor
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ABSTRACT: SnS nanocrystals have been synthesized in a simple and facile way. Sn(6)O(4)(OH)(4) is introduced to synthesize tin sulfide, which is used as tin precursor. By changing the reaction conditions (reaction temperature and Sn/S molar ratio), SnS nanocrystals with different shape and size can be produced. SnS nanoparticles and nanoflowers with orthorhombic crystal structure have uniform size distribution. The SnS nanoflowers firstly transform to polycrystalline nanoflowers, and then become amorphous nanosheets. The drive force of amorphization reduces the high free-energy of nanocrystals. The layered crystal structure of SnS is the main reason for the shape evolution and amorphization processes. The optical properties of nanoparticles are investigated by optical absorption spectra. The optical direct band gap and optical indirect band gap in SnS nanoparticles are 3.6 eV and 1.6 eV, respectively. Compared to direct band gap (1.3 eV) and indirect band gap (1.09 eV) in bulk SnS, both direct transition and indirect transition in nanoparticles show an obvious quantum-size effect.
Nanoscale 09/2010; 2(9):1699-703. · 5.91 Impact Factor
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ABSTRACT: Cubic beta-In(2)S(3) nanoparticles (NPs) have been synthesized by a simple and facile way, which is 6 nm in size. Absorption and emission spectra of In(2)S(3) NPs show obvious blue peak shift compared to band gap of bulk In(2)S(3), indicating the strong quantum size confinement effect. The fluorescence quantum yield of In(2)S(3) NPs is found to be 10%. During the synthesis process, the absorption spectra have no peak shift, which is responding to transition from valence band to the conduction band levels. This absorption spectra show that the nucleation and growth process of In(2)S(3) NPs is very quick. The PL lifetime spectra and time resolved spectra give two emission processes in In(2)S(3) NPs, which would be excitonic recombination and electron-hole recombination via defects levels. The blue shift of emission peaks show the emission process in In(2)S(3) NPs is from mainly electron-holes recombination via defects levels to excitonic recombination. The Stokes shift becomes smaller which is mainly contributed by blue shift of emission and smaller contribution from the UV-Vis absorption. The absorption and emission spectra show the size and crystallinity of In(2)S(3) NPs have no changes (HRTEM images provide enough proofs); however the surface-related defects changed greatly in the reaction process.
Journal of Colloid and Interface Science 07/2010; 347(2):172-6. · 3.07 Impact Factor
