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Nanocrystal samples (particle size about 90 nm) of Eu3+-doped rutile titanium dioxide (TiO2) nanocrystals (rutile Eu3+/TiO2 nanocrystals) were synthesized by the sol–gel method with hydrothermal treatment. The pressure effect on photoluminescence (PL) and Raman spectra of the rutile Eu3+/TiO2 nanocrystals was investigated with a diamond anvil cell under hydrostatic pressure condition. Raman spectra of the samples at high pressures indicated that the critical pressure for the transition from the rutile phase to a new baddeleyite-type phase was between 10 and 14.2 GPa. The position of Raman bands shifted to high wavenumbers and the PL intensity of 5D 0→7F 2 transition of Eu3+ decreased down to zero with the increase of pressure before the phase transition occurred. After releasing the pressure, the rutile phase was not recovered and a α-PbO2-type phase was observed at ambient pressure. [ABSTRACT FROM PUBLISHER]

Abstract: Pressure-induced changes on fluorescence spectra of Congo red molecules were examined up to 8.7GPa using a diamond anvil cell at room temperature. The spectra changes are demonstrated to be sensitive to the pressure and solvent conditions. At hydrostatic pressure and with a solvent used as a pressure transmitting medium the fluorescence spectra show increase of intensity with elevated pressure up to about 2.3GPa and then drop at higher pressures. For Congo red crystal under quasi-hydrostatic condition without solvent the fluorescence intensity decreases monotonically and the lower energy band becomes dominant with the pressure increasing. The three vibronic bands show red shifts with increase of pressure. [Copyright &y& Elsevier]

Abstract: The sample of Eu3+-doped TiO2 (Eu3+/TiO2) nanocrystals is synthesized by the sol–gel method with hydrothermal treatment. Raman and photoluminescence (PL) spectra of the sample have been investigated under high pressure up to 18GPa using a diamond anvil cell. At ambient pressure, a strong PL signal associated with the 5D0→7FJ (J=0,1,2,3,4) transition of Eu3+ under the excitation wavelength at 514.5nm is observed. The emission peaks red shift slightly and the intensity decreases with the increase of pressure, while the intensity ratio between 5D0→7F2 and 5D0→7F1 decreases dramatically. A phase transition is observed at 8.2–10.6GPa by the Raman spectra analysis. Reducing of the intensity ratio between 5D0→7F2 and 5D0→7F1 value indicates the rising of the site symmetry and the weakening of the covalency of Eu–O bond. [Copyright &y& Elsevier]

Abstract: Pressure-induced changes of the fluorescence spectra of Nd:YVO4 crystals have been studied up to 10.88GPa using a diamond anvil cell at ambient temperature. The changes of spectra indicate that pressure has remarkably influenced both the fluorescence intensity and the energy levels of Nd:YVO4 crystals. With pressure increasing up to 7.45GPa, the intensity of the spectra decreases and the peak positions shift red gradually. For pressure above 7.5GPa, the fluorescence intensity decreases quickly and the shift rates of the peaks is slowed down. This suggests that 7.5GPa is a critical point of the pressure at which the crystal may have a pressure-induced phase transition and the crystal-field changes. The new characters of the fluorescence spectra remain stable as the pressure is released to ambient pressure. [Copyright &y& Elsevier]

Abstract: The pressure effect on photoluminescence (PL) and Raman spectra of the poly (para-phenylene vinylene) (PPV) has been investigated with a diamond anvil cell (DAC) under the hydrostatic pressure condition. The intensity ratios, I 1167/I 1622 and I 1543/I 1622, increase with pressure. This indicates that the conjugated length of PPV is enhanced at high pressures. In addition, appearance of a new Raman band corresponding to CC stretch at 1190cm−1 shows that the chain conformation defects decreased with increasing pressure. The redshift of the PL spectra and shift to higher frequencies for Raman bands with increase in pressure are explained by combining the conjugation model with amplitude mode model. [Copyright &y& Elsevier]