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Featured researches published by Qiliang Cui.


Journal of Physical Chemistry B | 2010

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

Yingai Li; Jian Zhang; Qiushi Wang; Yunxia Jin; Dahai Huang; Qiliang Cui; Guangtian Zou

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.


Applied Physics Letters | 2006

Pressure-induced structural transition in AlN nanowires

Longhai Shen; Xiaokun Li; Yanmei Ma; Kaifeng Yang; Weiwei Lei; Qiliang Cui; Guangtian Zou

The structural transition of AlN nanowires was investigated under pressures up to 51.1GPa by in situ angle dispersive high-pressure x-ray diffraction using synchrotron radiation source and a diamond anvil cell. A pressure-induced wurtzite to rocksalt phase transition starts at 24.9GPa and completes at 45.4GPa. The high-pressure behaviors of AlN nanowires differing from the bulk and nanocrystal AlN might arise from the intrinsic geometry in nanowires.


Journal of Physical Chemistry B | 2009

Pressure-induced phase transition in hydrogen-bonded supramolecular adduct formed by cyanuric acid and melamine.

Kai Wang; Defang Duan; Run Wang; Dan Liu; Lingyun Tang; Tian Cui; Bingbing Liu; Qiliang Cui; Jing Liu; Bo Zou; Guangtian Zou

Single-crystal samples of the 1:1 adduct between cyanuric acid and melamine (CA.M), an outstanding case of noncovalent synthesis, have been studied by Raman spectroscopy and synchrotron X-ray diffraction in a diamond anvil cell up to pressures of 15 GPa. The abrupt changes in Raman spectra around 4.4 GPa have provided convincing evidence for pressure-induced structural phase transition. This phase transition was confirmed by angle dispersive X-ray diffraction (ADXRD) experiments to be a space group change from C2/m to its subgroup P2(1)/m. On release of pressure, the observed transition was irreversible, and the new high-pressure phase was fully preserved at ambient conditions. We propose that this phase transition was due to supramolecular rearrangements brought about by changes in the hydrogen bonding networks.


Journal of Physical Chemistry B | 2012

In Situ Observation of Multiple Phase Transitions in Low-Melting Ionic Liquid [BMIM][BF4] under High Pressure up to 30 GPa

Lei Su; Xiang Zhu; Zheng Wang; Xuerui Cheng; Yongqiang Wang; Chaosheng Yuan; Zhenping Chen; Chunli Ma; Fangfei Li; Qiang Zhou; Qiliang Cui

In situ characterization of phase transitions and direct microscopic observations of a low-melting ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]), has been performed in detail by Raman spectroscopy. Compression of [BMIM][BF(4)] was measured under hydrostatic pressure up to ~30.0 GPa at room temperature by using a high-pressure diamond anvil cell. With pressure increasing, the characteristic bands of [BMIM][BF(4)] displayed nonmonotonic pressure-induced frequency shifts, and it is found to undergo four successive phase transitions at around 2.25, 6.10, 14.00, and 21.26 GPa. Especially, above a pressure of 21.26 GPa, luminescence of the sample occurs, which is connected with the most significant phase transition at around this pressure. It was indicated that the structure change under high pressure might be associated with a conformational change in the butyl chain. Upon releasing pressure, the spectrum was not recovered under a pressure up to 1.16 GPa, thereby indicating that this high-pressure phase remains stable over a large pressure range between 30 and 1.16 GPa in low-melting ionic liquid [BMIM][BF(4)]. Although the sample was kept under the normal pressure for 24 h, the spectrum was recovered, and it showed that the phase transition of [BMIM][BF(4)] was reversible. In other words, such a low-melting ionic liquid [BMIM][BF(4)] remains stable even after being treated under so a high pressure of up to 30 GPa.


Applied Physics Letters | 2009

Ferromagnetic Sc-doped AlN sixfold-symmetrical hierarchical nanostructures

Weiwei Lei; Dan Liu; Pinwen Zhu; Xin Chen; Qiang Zhao; Gehui Wen; Qiliang Cui; Guangtian Zou

Sc-doped AlN (AlN:Sc) sixfold-symmetrical hierarchical nanostructures were grown by direct current (dc) arc discharge plasma method using the direct reaction of Al and Sc metals with N2 gas. Energy-dispersive x-ray spectroscopy, x-ray diffractometry, and Raman spectra analysis clearly showed that Sc was doped in the AlN hierarchical nanostructures. The magnetization curves indicate the existence of room-temperature ferromagnetic behavior. The saturation magnetization and the coercive fields (Hc) of the AlN:Sc nanostructures are about 0.04 emu g−1 and 200 Oe, respectively. The results reveal that Sc is a potential nonmagnetic dopant for preparing diluted magnetic semiconductor nanomaterials.


Journal of Chemical Physics | 2005

High pressure-temperature Brillouin study of liquid water: Evidence of the structural transition from low-density water to high-density water

Fangfei Li; Qiliang Cui; Zhi He; Tian Cui; Jian Zhang; Qiang Zhou; Guangtian Zou; Shigeo Sasaki

The structural transformations occurring to water from low-density (LDW) to high-density (HDW) regimes have been studied by Brillouin scattering for the first time at temperatures up to 453 K and at pressures up to the solidification point. At ambient temperature (293 K) a discontinuity in pressure response of the sound velocity is observed. Furthermore, there are evident breaks in the linear behavior of log10 C11 versus log10(rho/rho0) when pressure increases up to 0.29, 0.21, and 0.19 GPa at the temperature of 293, 316, and 353 K, respectively. It is supposed to indicate the structural transition from LDW to HDW, and the possible transition boundary between LDW and HDW is in good agreement with the molecular-dynamics simulation.


Journal of Physics D | 2009

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

Yunxia Jin; Qiliang Cui; Gehui Wen; Qiushi Wang; Jian Hao; Shuang Wang; Jian Zhang

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.


Journal of Applied Physics | 2009

High-pressure Raman scattering and x-ray diffraction of phase transitions in MOO3

Dedi Liu; Weiwei Lei; Jian Hao; Dan Liu; Bingguo Liu; Xi Wang; Xin Chen; Qiliang Cui; Guangtian Zou; J. Liu; S. Jiang

The high-pressure behavior of molybdenum trioxides (MoO3) has been investigated by angle-dispersive synchrotron x-ray powder diffraction and Raman spectroscopy techniques in a diamond anvil cell up to 43 and 30 GPa, respectively. In the pressure range of up to 43 GPa, structural phase transitions from the orthorhombic α-MoO3 phase (Pbnm) to the monoclinic MoO3-II phase (P21/m), and then to the monoclinic MoO3-III phase (P21/c), occurred at pressures of about 12 and 25 GPa at room temperature, respectively. Our observation of the transition from the orthorhombic α-MoO3 to the monoclinic MoO3-II phase is in disagreement with earlier studies in which the phase transition could not be obtained when only pressure is applied. The changes in the Mo–O distances and O–Mo–O and Mo–O–Mo angles may explain the changes in Raman spectrum. The pressure dependence of the volume of two monoclinic high-pressure phases is described by a third-order Birch–Murnaghan equation of state, which yields a bulk modulus value of B0=1...


Journal of Applied Physics | 2011

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

Yunxia Jin; Qiliang Cui; Kai Wang; Jian Hao; Qiushi Wang; Jian Zhang

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...


Langmuir | 2009

Stability of hydrogen-bonded supramolecular architecture under high pressure conditions: pressure-induced amorphization in melamine-boric acid adduct.

Kai Wang; Defang Duan; Run Wang; Aolei Lin; Qiliang Cui; Bingbing Liu; Tian Cui; Bo Zou; Xi Zhang; Jingzhu Hu; Guangtian Zou; Ho-kwang Mao

The effects of high pressure on the structural stability of the melamine-boric acid adduct (C3N6H(6).2H3BO3, M.2B), a three-dimensional hydrogen-bonded supramolecular architecture, were studied by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy. M.2B exhibited a high compressibility and a strong anisotropic compression, which can be explained by the layerlike crystal packing. Furthermore, evolution of XRD patterns and Raman spectra indicated that the M.2B crystal undergoes a reversible pressure-induced amorphization (PIA) at 18 GPa. The mechanism for the PIA was attributed to the competition between close packing and long-range order. Ab initio calculations were also performed to account for the behavior of hydrogen bonding under high pressure.

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