Preparation and Luminescent Characteristics of LaPO_4∶Eu Nanoparticles and Nanowires

Nanoparticles and nanowires of LaPO 4: Eu phosphors were synthesized by hydrothermal method. Their luminescent properties including electronic transition, surface effect, and temperature-dependent luminescent characteristics were systemically studied and compared to the bulk powders. It can be concluded that in comparison with the bulk powders, the fluorescence intensity decreases in nanoparticles and nanowires, while the lifetime increases, indicating that the radiative transition rate decreases. The nonradiative transition rate in nanowires decreases than that in nanoparticles due to its decreased surface to volume ratio. The temperature-dependent experiments indicate that the thermal quenching in nanopowders becomes weaker than that in the bulk powders.

Apoptotic Effects of Hypocrellin A on HeLa Cells

Hypocrellin A（ HA）, a photosensitive perylenequinone compound of Hypocrella bambusae, inhibited the proliferation of several tumor cell lines. Human cervical cancer cells, HeLa ceils, were used as a model to elucidate the molecular mechanisms of HA-induced tumor cell death. The results show that HA can induce the oligonucleosomal fragmentation of DNA in HeLa cells and also can increase the expression of apoptosis inducer Bax mRNA and that it decreases the expression of apoptosis suppressor, Bcl-2 mRNA, in mitochondria. It can be concluded from the data that HA-induced apoptosis is related to the balance between Bcl-2 and Bax gene expressions.

Fabrication of Ormocer Containing Eu^(3+) Ion and Their Optical Spectra

Eu 3+ ions were incorporated in sol and gel by a sol gel processing using 3 glycidoxypropyltrimethoxysilane (CH 2OCHCH 2O(CH 2) 3Si(OCH 3) 3, GPTMS) and ethyl silicate (TEOS) as precursors. The basic chemical physical properties such as DTA curve, FT IR spectra and specific surface area were recorded. The characteristics of their optical spectra were measured and investigated. The results indicate that the emission intensity of Eu 3+ ion in ormocer is much higher and the global line width is wider than those in SiO 2 gel. The relationship between the composition and structure of gels and the fluorescence intensity and width were discussed. The obtained ormocer shows good mechanical strength, which can be cut and polished in machine without broken.

Structure and Luminescent Properties of Co-doped Nanocrystalline Y_2O_3∶Eu

Nanocrystalline Y_2O_3∶Eu powders doped with different metal ions M (M: Li +,Na +,K +,Mg (2+),Sr (2+),Ba (2+),B (3+) and Al (3+)) were synthesized by glycine combustion. Their structure and luminescent properties were studied and compared with each other. The nanocrystalline Y_2O_3 were cubic in symmetry by XRD pattern. It can be concluded that co-doping can modify the size and crystallinity of nanoparticles. As a consequence,the luminescent properties such as the fluorescent intensity,lifetime of (() 5D_0)-(() 7F_2) and the location of charge transfer band (CT band) vary with co-dopants. The variation depends more strongly on the crystallinity of nanoparticles than the size. Especially,in Li +-doped Y_2O_3∶Eu nanoparticles,the emission intensity improves as large as three times than that of undoped ones.

Preparation of CdSe/ZnSe Core-shell Nanocrystal in One-step Reaction

High-quality Zn-doped CdSe core-shell nanocrystals were successfully prepared by incorporating a stoichiometric amount of Zn precursor into the CdSe reaction system, in which the Se precursor was excess and an Se-rich surface was formed. By injecting different amounts of Zn precursor, the core-shell nanocrystals demonstrated by the emission spectra were formed. The obtained Zn-doped CdSe nanocrystals exhibit a photoluminescence efficiency from 30% to 85%, which is comparable to those for the reported CdSe/ZnS, CdSe/CdS in the literature. In particular, a shell ZnSe layer with different thicknesses of ZnSe can be formed in this experiment by only changing the amount of Zn precursor added, which is simple and effective.

Effect of TiO_2 Nanoparticles on Photochromism of WO_3 Colloids

WO2 and TiO2 colMds were synthesized by the hydrolysis technique and part of the TiO2 colloid was treated by means of the hydrothermal method. The photochromic performances of the resulting materials obtained via combining the WO3 colloid with the treated TiO2 colloid and the non-treated TiO2 colloid, respectively, are very different. The TiO2 colloid without hydrothermal treatment can effectively improve the photochromic performance of the WO3colloid. The TiO2 nanoparticles were investigated in detail by XRD, TEM, surface photovohage spectra（SPS） and field-induced surface photovoltage spectrometry（FISPS）. The photochromism mechanism of WO3 colloid is discussed.

Properties of Local Structure Surrounding Eu^(3+)Ion in Various Niobate-Silicate Glasses

A Series of niobate silicate glasses doped with Eu 3+ ions were prepared. The emission, phonon side band spectra, fluorescence line narrowing spectroscopy and fluorescence lifetimes in these glasses were studied. The intensity parameters and crystal field parameter of Eu 3+ were obtained. The results indicate that the intensity ratio of the electric dipole to magnetic dipole transition and the intensity parameter Ω 2 increase with the increasing concentration of Nb 2O 5, indicating that the symmetry becomes lower, the Eu O bonds become stronger and the covalency of Eu O bond increases. The value of B 20 decreases with the increasing concentration of Nb 2O 5, indicating that the distance between the Eu 3+ ion and oxygen decreases and the Eu O bond becomes strong, corresponding to the results of the former. As the concentration of Nb 2O 5 increases, the electron phonon coupling becomes stronger, thus the nonradiative transition rate of 5D 0 becomes larger and the lifetime of 5D 0 becomes shorter.

Influence of Rinse on Self-Activated Luminescence in ZnS Nanocrystallite

The self-activated (SA) luminescence in ZnS nanoparticles was studied by comparing the UV-light irradiation induced spectral change, Raman spectra, and EPR spectra of the un-rinsed and rinsed samples. The results show that the SA centers prefer to occupy the sites near the surface and that the donor of SA emission may be related to organic functional groups such as -OH, -CH 3, and -COO. The EPR signals are enhanced remarkably in the rinsed nanoparticles comparing with that in the un-rinsed ones. It is believed that organic functional groups physically combine with the surface dangling bonds of ZnS nanoparticles, leading the nonradiative transition channels to decrease, and thus the SA emission to increase.

Time-Resolved Photoluminescence Spectroscopy： A Novel Technique for Determination of Luminescence of Quantum Dots

The time-resolved photoluminescence （PL） spectroscopy measured by the gradually increasing start delay time is utilized as a tool for the determination of the luminescence of quantmn dots （QDs）. The luminescence evolution of self-assembled CdSe QDs during the luminescence decay is fully revealed in terms of the experiment technique. The characteristic narrow luminescence lines of self-assembled CdSe QDs are obtained with increasing start delay time.

TDDFT-SOS Studies on the Polarizabilities and Second-order Hyperpolarizabilities of Zn_3O_3 II-VI Semiconductor Clusters

The geometrical structure of semiconductor clusters including Zn3O3 was optimized by the DFT B3LYP method. With the same basis sets, dipole moments, polarizabilities and secondorder hyperpolarizabilities have been calculated and compared with the results obtained by TDDFT B3LYP method combined with sum-over-state （SOS） formula. The calculation results indicate that the dipole moments of the ground state depend on the atom radius and electronegative differences between elements and are their balance point as well. The polarizabilities of the clusters accord with the rule of the corresponding energy transformation from ground to excited state. The results predict an increase of second-order hyperpolarizabilities with increasing the distances between atoms in the clusters as well as a decrease of the polarizabilities and second-order hyperpolarizabilities in the same serial of semiconductor clusters with increasing the dipole moments of the ground states. The changes of dipole moments in ground states are inconsistent with transition moments. Spatial structure, charge transfer and other factors play an important role in composing the transition moments.

Upconversion Luminescence Dynamics in Er^3＋/Yb^3＋ Codoped Nanocrystalline Yttria

The upconversion luminescence and dynamics in Er^3＋ /Yb^3＋ codoped nanocrystalline yttria （7-65 nm） are studied under 980-nm pulsed laser excitation, It is found that the red emission of ^4F9/2-^4I15/2 and the green emission of ^2H11/2/^4S3/2 in nanoparticles with lower concentration of Yb^3＋ result from a two-photon excitation, In nanocrystals with higher Yb^3＋ concentration, the red emissions from a two-photon excitation, while the green emissions from a three-photon excitation, The luminescence dynamics indicates that as the particle size decreases, both the rise and the decay time constants become shorter, As the size decreases to several nanometres, the rise process nearly disappears, suggesting that the upconversion luminescence originates mainly from self-excitation of Er^3＋, instead of the energy transfer of Yb^3＋→ Er^3＋.

Preparation and optical spectroscopy of phosphate glasses containing divalent europium ions

P2O5.BaO.Na2O.K2O glasses doped with various content of Eu2O3 were prepared using high temperature melting method, and the Eu2+ ions in the phosphate glasses were obtained with the aid of the reductive action of silicon powder. The fabricating conditions, fluorescence, excitation spectra of the glasses were then studied. The glasses containing europium show a broad emission band at 450 nm and sharp bands from 580 to 650 nm, and the co-existence of Eu2+ and Eu3+ is identified. Also, a good glass with a dominant proportion and large quantity of Eu2+ ions can be obtained by the reductive action of silicon powder and proper processing.

Application of ring-opening metathesis polymerization in study of polymer molecular weight-mediated catalytic properties of immobilized lipase

Recently, significant efforts have been devoted into the study of the effect of hydrophobic supports on the catalytic properties of immobilized lipases. It seems that immobilization lipases on hydrophobic supports is a simple and efficient method to improve the catalytic activity of lipases. In this study, the hydrophobic poly(N-propyl-norbornene-exo-2,3-dicarboximide)s with well-controlled molecular weight were synthesized by the living ring-opening metathesis polymerization, and the lipases from Pseudo- monas sp. were then immobilized on these hydrophobic polymer supports through the physical ad- sorption. The immobilized lipases exhibited higher activity and enantioselectivity for the transesterifi- cation of 2-octanol than those of free lipases. Furthermore, we investigated the polymer molecular weight-mediated catalytic properties of immobilized lipases. It was found that the catalytic activity and E value of the immobilized lipases increased with the increase of the polymer molecular weight. At the polymeric molecular weight of about 40kDa, the highest E value (58 at 54.2% of conversion, enanti- omeric excess = 99%) was reached. After the molecular weight of polymers getting higher than 40 kDa, catalytic activity and E value of the immobilized lipase decreased.