Yunxia Jin

Nitrogen-rich carbon nitride hollow vessels: synthesis, characterization, and their properties.

Bulk quantities of nitrogen-rich graphitic carbon nitride are synthesized via a facile reactive pyrolysis process with a mixture of melamine and cyanuric chloride as the molecular precursors. Scanning electron microscopy and transmission electron microscopy studies show that micrometer-sized hollow vessels with high aspect ratios have been successfully elaborated without the designed addition of any catalyst or template. The composition of the prepared carbon nitride determined by combustion method is C(3)N(4.91)H(1.00)O(0.22), with the N/C ratio to be 1.64, indicating a high nitrogen content. X-ray diffraction pattern reveals the regular stacking of graphene CN(x) monolayers along the (002) direction with the presence of turbostratic ordering of C and N atoms in the a-b basal planes. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy investigations provide further evidence for graphite-like sp(2)-bonded building blocks based on both triazine and heptazine ring units bridged by 3-fold coordinated nitrogen atoms. The optical properties of the sample are investigated by UV-vis absorption and photoluminescence spectroscopy, which show features characteristic of pi-pi* and n-pi* electronic transitions involving lone pairs of nitrogen atoms. Thermogravimetric analysis curves of the synthesized graphitic carbon nitride hollow vessels show typical weight loss steps related to the volatilization of triazine and heptazine structural units.

XPS and Raman scattering studies of room temperature ferromagnetic ZnO : Cu

ZnO and Cu-doped ZnO nanocrystals have been synthesized by a sol–gel method. The nanocrystals have been investigated by XRD and all the particles are found to show the wurtzite structure. X-ray photoelectron spectroscopy and Raman scattering results provide evidence that Cu ions are mainly in the divalent state and incorporated into the ZnO lattice at Zn2+ sites. Magnetic measurements reveal that the as-grown Zn0.9894Cu0.0106O nanocrystals exhibit room temperature ferromagnetic behaviour with the saturation magnetization of 0.0053 emu g−1 and the Curie temperature above 300 K.

Investigation of photoluminescence in undoped and Ag-doped ZnO flowerlike nanocrystals

Flower-shaped undoped and Ag-doped ZnO nanocrystals have been synthesized by a hydrothermal method. The nanocrystals have been investigated by x-ray powder diffraction and all the particles are found to show the wurtzite structure. Scanning electron microscopy and high resolution transmission electron microscopy reveal the flower-shaped structures of the samples consist of many pricklelike nanopetals. The x-ray photoelectron spectroscopy results provide evidence that Ag ions are mainly in the monovalent state and incorporated into the ZnO lattice at Zn2+ sites. It was found from the UV–visible spectra that the bandgap of ZnO decreases due to Ag doping. Excellent enhancement of luminescence properties in the green band is observed in Ag-doped ZnO nanocrystals. The origin of this enhancement was discussed. It was demonstrated that oxygen vacancies and a spin-split impurity band are the key factors for deep level emissions. We believe that the present approach is a very simple but effective one for synthesis...

High-Pressure Structural Transitions of Sc2O3 by X-ray Diffraction, Raman Spectra, and Ab Initio Calculations

The high-pressure behavior of scandium oxide (Sc(2)O(3)) has been investigated by angle-dispersive synchrotron powder X-ray diffraction and Raman spectroscopy techniques in a diamond anvil cell up to 46.2 and 42 GPa, respectively. An irreversible structural transformation of Sc(2)O(3) from the cubic phase to a monoclinic high-pressure phase was observed at 36 GPa. Subsequent ab initio calculations for Sc(2)O(3) predicted the phase transition from the cubic to monoclinic phase but at a much lower pressure. The same calculations predicted a second phase transition at 77 GPa from the monoclinic to hexagonal phase.

Pressure-Induced Structural Transitions in MOO3·xH2O (x = 1/2, 2) Molybdenum Trioxide Hydrates: A Raman Study

The high-pressure behaviors of M(O)O(3).1/2H(2)O and M(O)O(3).2H(2)O have been investigated by Raman spectroscopy in a diamond anvil cell up to 31.3 and 30.3 GPa, respectively. In the pressure range up to around 30 GPa, both M(O)O(3).1/2H(2)O and M(O)O(3).2H(2)O undergo two reversible structural phase transitions. We observed a subtle structural transition due to O-H...O hydrogen bond in M(O)O(3).1/2H(2)O at 3.3 GPa. We found a soft mode phase transition in M(O)O(3).2H(2)O at 6.6 GPa. At higher pressures, a frequency discontinuity shift and appearance of new peaks occurred in both M(O)O(3).1/2H(2)O and M(O)O(3).2H(2)O, indicating that the second phase transition is a first-order transition. The frequency redshift of the O-H stretching bands of M(O)O(3).1/2H(2)O and M(O)O(3).2H(2)O are believed to be related to the enhancement of the O-H...O weak hydrogen bonds under high pressures.