Tang Guo-Qing

Study on dynamic optical nonlinearities of excited state proton transfer in ethanol solution of 7-hydroxyquinoline

Abstract The dynamic process of 7-hydroxyquinoline with excited state proton transfer has been studied by the pump–probe method in which a three-dimensional degenerate four-wave mixing technique is employed for the probe. The molecular hyperpolarizability and lifetime of the excited state involved in the excited state proton transfer process of 7-hydroxyquinoline are obtained in our experiment. The decay time of the cation excited state is 35 ps and the decay time of the anion excited state is 250 ps. The molecular hyperpolarizability of 7-hydroxyquinoline in the enol form ground state, cation excited state and anion excited state are 1.3±0.2×10 −31 , 8.0±1.0×10 −31 and 5.8±0.8×10 −30 esu, respectively.

Study of energy transfer between rare earth ions in CaS host by photoluminescence spectra

When CaS:Sm3+, Eu2+ is excited at 476.5 nm (Ar+), the emission spectra taken at room temperature and at 77 K are different, indicating that there are two competitive energy transfer processes-Sm3+ --> Eu2+ and Eu2+ --> Sm3+ with phonon participation. So, the luminescence intensity of Sm3+ increases first, and then decreases as the concentration of Eu2+ is increasing

Correlation of Photosensitization and Binding Mode of Methylene Blue and DNA

Binding of methylene blue (MB) and DNA, photosensitization of MB in DNA, and correlation of photosensitization and binding mode are studied at different concentration ratios of DNA and MB. The absorption spectra indicate that the electrostatic binding is the main mode at low γ ratios (γ ≤ 2), while at high γ ratios (γ > 2) the intercalative binding is dominated. Studies on dynamics of photosensitization formation of singlet oxygen (1O2) for MB in DNA are carried out by using time-resolved technology. There are no obvious changes of the singlet oxygen lifetime and the triplet state MB molecule (MB3+*) lifetime at low ratios, they are about 4 μs and 1 μs, respectively. However, we could not obtain the 1O2 lifetime and MB3+* lifetime due to the great decrease of 1O2 phosphorescence signals at high ratios. These results show that the photosensitization and binding mode of MB in DNA possess high correlation. When MB binds with DNA by electrostatic interaction, type-II photosensitization of MB plays a major role in photodynamic effect, the damage of DNA probably could be ascribed to 1O2. However, at high ratios, binding mode between MB and DNA turns to intercalative binding, which greatly weakens the type-II photosensitization process. Charge transfer between MB and DNA possibly becomes the main damage mechanism.

Nonlinear Transmission Property of the Excited State Proton Transfer Molecule 7-Hydroxyquinoline

Nonlinear transmission property of 7-hydroxyquinoline with excited state proton transfer effect was investigated at 355 and 532 nm using picosecond laser pulses. The experiment result shows that the transmissivity of 7-hydroxyquinoline is nonlinear at 355 nm but it is linear at 532 nm. The nonlinear transmissivity of 7-hydroxyquinoline originates from the larger nonlinearity of anion and cation formed in excited state proton transfer process. Therefore, 7-hydroxyquinoline might be used as ultrafast optical amplitude limit material.

The linear and nonlinear optical properties of nanometer-sized In2O3 organosol

The linear and nonlinear optical properties of nanometer-sized In2O3 organosol were investigated by using TEM, ESR, UV-visible absorption spectrum, photoluminescence spectra and Z-scan technique. It was found that the prepared In2O3 organosol showed a series of new optical properties, which can be explained by its special structure. These new optical properties made its application in information optics enlarged.

X-RAY PHOTOELECTRON EMISSION STRUCTURES OF CuO NANOPARTICLES

In this paper we report the x-ray photoemission characteristics of CuO nanoparticles with surface modifications. We found the enhancement of interatomic resonant charge transfer and multi-electron relaxation processes in the coated CuO nanoparticles, which were in agreement with the conclusions of polaron-related structural transition appearing under quantum confinement and dielectric confinement effects, as observed in the optical absorption and infrared vibration spectra of this system.