Novel synthesis of selective phase-shape orientation of AgInS2 nanoparticles at low temperature

In this work, phase- and shape-controlled AgInS2 (AIS) colloidal nanoparticles are synthesized by thermal decomposition of metal xanthate at a temperature of similar to 110 A degrees C in an organic solvent containing surfactant molecules. The spherical tetragonal-shaped AIS was observed when o-dichlorobenzene (DCB) with oleylamine (OLA) and trioctylphosphine (TOP) was used, while rod-shaped AIS with orthorhombic structure was observed in the presence of o-dichlorobenzene with pyridine (PY). The resulting nanoparticles are analyzed by X-ray diffraction (XRD), UV-vis, PL, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) techniques. It is also reported that the AIS nanoparticles (NPs) synthesized in the presence of OLA and TOP show a photoluminescence properties, and their fluorescence emission wavelength can readily be tuned from the ultraviolet (UV) to the visible spectrum region by merely prolonging the reaction time

Synthesis and optical properties of pure CdTiO₃ and Ni²⁺ and Zn²⁺ ion substituted CdTiO₃ obtained by a novel precursor route

1538-1544Monophasic CdTiO3 in ilmenite and perovskite structures have been synthesized by a novel precursor route using oxine as the complexing agent and their optical and photoluminescence properties have been characterized. The co-precipitated oxinates of cadmium and titanium on one time heating at 600 °C for 6 h yields the ilmenite structured CdTiO3 (space group R<i style="mso-bidi-font-style: normal"> ) with the lattice parameters a = 5.237(1) and <i style="mso-bidi-font-style: normal">c = 14.84 (6) Å as revealed by its powder X-ray diffraction pattern. The presence of rhombohedral symmetry is further confirmed by the six bands observed at 216, 246, 325, 461, 598, and 694 cm-1 due to Eg and <i style="mso-bidi-font-style: normal">Ag modes in the Raman spectroscopy. Phase transition from ilmenite to perovskite structure (space group <i style="mso-bidi-font-style: normal">Pbnm) occurs at 1000 °C. PXRD pattern of the transformed CdTiO3 is indexed in the orthorhombic symmetry with a = 5.305 (3); <i style="mso-bidi-font-style: normal">b = 5.421 (1); c = 7.617 (3) Å. The broadness and the shift of the Raman band position to 279, 326, 400, 444 and 578 cm-1 endorses the orthorhombic symmetry. From the diffuse reflectance measurements, band gap values of 2.9 eV and 2.8 eV have been estimated for the ilmenite and perovskite forms of CdTiO3. An additional emission band at 3.21 eV is observed in the photoluminescence spectrum of ilmenite CdTiO3. Synthesis and optical properties of Ni2+ and Zn2+ substituted CdTiO3 are also reported

Application of KZnF3 as a Single Source Precursor for the Synthesis of Nanocrystals of ZnO2:F and ZnO:F; Synthesis, Characterization, Optical, and Photocatalytic Properties

Mixed metal fluoride, KZnF3, possessing a cubic perovskite structure has successfully been employed as a single source precursor for the synthesis of fluoride-doped ZnO2 nanocrystals by a simple low-temperature oxidation procedure. Utilizing the fact that ZnO2 is a precursor for ZnO, F–-doped wurtzite ZnO was readily obtained by a straightforward decomposition procedure. The structure, optical, and photocatalytic properties of doped ZnO2:F and ZnO:F were studied and compared with the undoped ones. The preservation of the cubic pyrite structure of ZnO2 by the inclusion of F–-ions was revealed by the powder X-ray diffraction pattern. Uniform cube morphology of the nanocrystals of ZnO2:F was observed in both the scanning electron microscopy and transmission electron microscopy images with the crystallite size of 20 nm. The IR and Raman spectroscopy analysis implied the absence of any Zn–F direct bonding in ZnO2:F. The high-resolution core level X-ray photoelectron spectroscopy (XPS) spectrum of F 1s observed at 687.9 eV confirmed the presence of fluoride ions in the ZnO2 lattice. By fitting the core level F 1s spectrum, the concentration of the F– ion was found to be 8.6%. A red shift in the excitonic absorption was observed on F– doping in ZnO2. A similar trend was also observed in the band edge emission from the photoluminescence spectrum recorded at 300 K. The intensity of the violet emission in the pure ZnO2 (with a decay time of 18 ns) decreased on F– doping (with a decay time of 13 ns). While ZnO2 nanocrystals efficiently degraded methylene blue (MB) solution under UV radiation and moderately under visible radiation, F–-doped samples showed lesser efficiency for the photo degradation of the MB solution. F–-doped ZnO was obtained by decomposing the ZnO2:F in air at 450 °C for 3 h. The symmetry remained hexagonal on F–-doping as revealed by the powder X-ray diffraction pattern. The intensity of the Raman bands of fluoride-doped ZnO nano powders were in general less as compared to the undoped ZnO, except the one observed at 582 cm–1, which indicated the presence of higher oxygen vacancies in ZnO:F. Core level XPS measurements provided conclusive evidence for the doping of fluorine (6.1%) in ZnO. The band gap value of ZnO:F, estimated from the diffuse reflectance spectrum, was 3.0 eV, and it showed broad visible emission. As a consequence of higher oxygen vacancies, ZnO:F exhibited efficient photocatalytic activity under visible irradiation for the degradation of aqueous MB dye solution

One-pot synthesis of CuInS2 and CuInS2/MS (M=Cd, Zn) core-shell luminescent nanocrystals: a low-temperature and low-cost approach

The single-pot synthesis of highly crystalline and fluorescent chalcopyrite CuInS2 (CIS) colloidal nanoparticles has been reported by thermal decomposition of metal ethyl xanthate (at similar to 110 degrees C) for the first time. The fluorescence emission wavelength can also be readily tuned from the UV to the visible region by merely prolonging the reaction time, as the PL emission may be varied from 550 to 675 nm. The synthesized CIS is subjected to postdeposition treatment with CdS/ZnS in one pot route using cadmium/zinc xanthate at low temperature (similar to 80 degrees C) to improve the quantum yield of core-shell (CIS/CdS or ZnS) nanocrystallites as compared to CIS core. The stability of core-shell particularly CIS/ZnS system upon continuous laser exposure suggests the formation of surface bonds with superior mechanical stability. This low-cost synthesis of such nontoxic QDs using green chemical routes is a promising approach for the fabrication of optoelectronic and biosensing devices