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A new ion sensor based on hybrid SiO2 -coated CdTe nanocrystals (NCs) was prepared and applied for sensitive sensing of Cu(2+) and Ag(+) for the selective quenching of photoluminescence (PL) of NCs in the presence of ions. As shown by ion detection experiments conducted in pure water rather than buffer solution, PL responses of NCs were linearly proportional to concentrations of Cu(2+) and Ag(+) ions < 3 and 7 uM, respectively. Much lower detection limits of 42.37 nM for Cu(2+) and 39.40 nM for Ag(+) were also observed. In addition, the NC quenching mechanism was discussed in terms of the characterization of static and transient optical spectra. The transfer and trapping of photoinduced charges in NCs by surface energy levels of CuS and Ag2 S clusters as well as surface defects generated by the exchange of Cu(2+) and Ag(+) ions with Cd(2+) ion in NCs, resulted in PL quenching and other optical spectra changes, including steady-state absorption and transient PL spectra. It is our hope that these results will be helpful in the future preparation of new ion sensors., (Copyright © 2012 John Wiley & Sons, Ltd.)

Micro- and nano-structures of iron oxide with tunable morphologies were fabricated through a solvothermal process by adjusting experimental parameters. In this route, the ethylene glycol (EG) solution of ferric chloride hexahydrate (FeCl3·6H2O), sodium bicarbonate (NaHCO3), and ethylenediamine (EDA) was heat-treated to create the micro- and nano-structures of Fe3O4, where EG acted as both solvent and reducing agent. NaHCO3 and EDA were crucial for the morphology and size of these micro- and nano-structures. Fe3O4 micro- and nano-structures revealed solid, porous and hollow morphologies by changing the reaction time, the type of solvent, and the amount of EDA and NaHCO3. Fe3O4 nanoparticles were created by controlling experimental parameters. As the reaction progressed, nanoparticles aggregated together to form solid Fe3O4 spheres, and then inner nanoparticles dissolved and recrystallized onto the outer shell of Fe3O4 spheres having been obtained through agglomerating together and then gradually developing into hollow micro- and nano-spheres due to an Ostwald ripening mechanism. Hematite (α-Fe2O3) was synthesized using ethyl alcohol instead of EG. These magnetic micro- and nano-structures revealed excellent magnetic properties. [ABSTRACT FROM AUTHOR]

Hierarchical urchin-like WO 2.72 microspheres decorated by uniform Au nanoparticles were synthesized via a two-step deposition process. The two-step deposition process, including weak reduction deposition and photo-deposition, ensures uniform size and well-dispersed Au nanoparticles. The gas-sensing properties of WO 2.72 and Au/WO 2.72 for trimethylamine (TMA) were investigated. The results show that Au/WO 2.72 has more outstanding gas-sensing performances, especially 3 wt% Au-loaded WO 2.72 (A3/WO 2.72). A3/WO 2.72 not only has superior selectivity and response for TMA gas but also exhibits fast response and recovery time. The response of A3/WO 2.72 –100 ppm of TMA at 260 °C can attain 87.3, which is approximately 6.1 times of pure WO 2.72. Besides, the good long-term effectiveness of A3/WO 2.72 -based sensor also can be observed. The mechanism of enhanced gas-sensing performances derived from the synergy of morphology, composition, and the sensitization effect of Au nanoparticles is proposed, which will facilitate the design and development of sensors decorated by noble metal. [ABSTRACT FROM AUTHOR]

Abstract: Undoped and Eu3+-activated Bi3TiNbO9 (BTNO) nanophosphors have been successfully synthesized by sol–gel combustion method. The effects of thermal annealing on the phase structure and crystallinity, morphology and UV–vis absorption of BTNO particles were investigated. Photoluminescence (PL) properties show that a broad blue emission was detected for BTNO nanoparticles, and the characteristic Eu3+ ion 5D0 → 7F J (J =1, 2, 3, 4) transitions were observed for the doped samples. Further investigation illuminates that the Eu3+ ions substituted for Bi3+ ions at A site in the pseudo-perovskite layers. It can be confirmed from high bright fluorescence image and short decay time that the novel orange-red phosphor has the potential applications in luminescence devices. [Copyright &y& Elsevier]

Abstract: Porous niobium oxide (Nb2O5) nanoparticles have been successfully prepared without any surfactant assisting. They were characterized by X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the porous Nb2O5 nanoparticles are polycrystalline, the Brunauer–Emmett–Teller (BET) surface area is 12.09m2/g and the average pore size is 3.4nm. In addition, spherical and flake-like Nb2O5 samples were obtained and characterized. Possible explanations for the formation of Nb2O5 nanocrystals with different morphologies are discussed. [Copyright &y& Elsevier]

Abstract: Pure and Mn-doped SrNb2O6 nanoparticles have been prepared by sol–gel combustion method using citric acid as fuel and complexing agent and nitrates as oxidants at a relatively low temperature compared to solid-state reaction method. X-ray diffraction (XRD) patterns of the pure SrNb2O6 samples show that the SrNb2O6 nanoparticles exhibited orthorhombic phase. Photoluminescence (PL) properties of all the undoped and Mn-doped samples were studied in detail. For the pure SrNb2O6 samples, a strong blue emission band centered at 442nm and two weak emission bands centered at 524nm and 626nm, respectively, can be observed. For the Mn-doped SrNb2O6 samples, no emission from Mn2+ was observed while the blue emission intensity of SrNb2O6 varied with the Mn-doping concentration. This novel PL characteristic of the doped samples was explained. [Copyright &y& Elsevier]

Abstract: Pure and Dy3+-doped Zn2SnO4 (ZTO) hollow spheres, integrated with nanoparticles, have been synthesized using the coprecipitation method. The ZTO spheres have been characterized with X-ray diffraction and scanning electron microscope. The photoluminescence and photocatalytic properties are investigated. The influences of Dy3+ ions on the morphology and the photoluminescence of ZTO have been explained in detail. [Copyright &y& Elsevier]

Abstract: Pure and Dy3+-doped NiNb2O6 nanoparticles have been prepared by a sol–gel combustion method using citric acid as fuel and complexing agent and nitrates as oxidants at a relatively low temperature compared to solid-state reaction method. The photoluminescence properties of these NiNb2O6 nanoparticles were studied in detail. For the pure NiNb2O6 nanoparticles, a blue emission band centered at 445nm is observed. For NiNb2O6:Dy3+ nanoparticles, no characteristic luminescence of Dy3+ can be observed while the host blue emission enhances. It is suggested that energy transfer from Dy3+ to niobate groups maybe occurs. [Copyright &y& Elsevier]