PHOTOINDUCED BIREFRINGENCE AND NUMERICAL SOLUTION OF A NEW DYNAMIC MODEL IN AN AMORPHOUS COPOLYMER CONTAINING AZOBENZENE GROUPS

Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. The levels of birefringence signal are found to depend an the polarization angle between the pump beam and the probe beam, and on the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described by known biexponential equations. The rate constants and the amplitudes associated with the growth process of the photoinduced birefringence are observed to display a linear dependence with the pump beam intensity. A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the bans and cis isomers of azobenzene groups and the local polymer segments. The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.

Effects of Lycium barbarum polysaccharide on the photoinduced autophagy of retinal pigment epithelium cells

AIM:To investigate the relationship between autophagy and apoptosis in photoinduced injuries in retinal pigment epithelium(RPE)cells and how Lycium barbarum polysaccharide(LBP)contributes to the increased of RPE cells to photoinduced autophagy.METHODS:In vitro cultures of human RPE strains(ARPE-19)were prepared and randomly divided into the blank control,model,low-dose LBP,middle-dose LBP,high-dose LBP,and 3-methyladenine(3MA)groups.The viability of the RPE cells and apoptosis levels in each group were tested through cell counting kit-8(CCK8)method with a flow cytometer(Annexin V/PI double staining technique).The expression levels of LC3II,LC3I,and P62 proteins were detected with the immunofluorescence method.The expression levels of beclin1,LC3,P62,PI3K,P-mTOR,mTOR,P-Akt,and Akt proteins were tested through Western blot.RESULTS:LBP considerably strengthens cell viability and inhibits the apoptosis of RPE cells after photoinduction.The PI3K/Akt/mTOR signal pathway is activated because of the upregulation of the phosphorylation levels of Akt and mTOR proteins,and thus autophagy is inhibited.CONCLUSION:LBP can inhibit the excessive autophagy in RPE cells by activating the PI3K/Akt/mTOR signaling pathways and thereby protect RPE cells from photoinduced injuries.

PHOTOINDUCED ADDITION REACTIONS OF CHLORANIL WITH FURAN DERIVATIVES

Photoinduoed reaction of chloranil （TCBQ） with 2-methylfuran la and 2,5-dimethylfuran 1b in benzene gave addition products 2a and 2b respecvely together with tetrachlorohydroquinone 3. A mechanism of sequential electron and proton transfer from la or 1b to;TCBQ followed by coupling of the furfuryl and semiquinone radical pairs was proposed and is evidenced by the photo-CIDNP studies of the TCBQ-1a and TCBQ-1b systems.

Photoinduced Second Harmonic Generation of Bi_2S_3 Microcrystallite Doped Silica Glass

Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 μm and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.

PHOTOINDUCED S_(RN)1 REACTIONS OF ARYL HALIDES WITH CARBAZOLYL NITROGEN ANION

The photoinduced reactions of aryl halides with carbazolyl nitrogen anion,in dimethyl sulfoxide,yield the corresponding N-arylated products.These reactions are suggested in terms of the S;Nl mechaism of nucleophilic substitution.

Studies on the Technology and Mechanism of Laser Photoinduced Alignment of Liquid Crystal

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅａｎｉｓｏｔｒｏｐｙｏｆｌｉｑｕｉｄｃｒｙｓｔａｌｓｍａｋｅｓｉｔｐｏｓｓｉｂｌｅｔｏｂｅｍａｄｅｉｎｔｏｍａｎｙｋｉｎｄｓｏｆｅｌｅｃ－ｔｒｏ－ｏｐｔｉｃｄｅｖｉｃｅｓ．ＷｈｅｎｔｈｅｔｈｉｃｋｎｅｓｓｏｆｔｈｅＬＣｃ...

Study of Photoinduced Interaction between Calf Thymus-DNA and Bovine Serum Albumin Protein with H₂Ti₃O₇Nanotubes

Hydrogen titanate nanotubes were synthesized by hydrothermal process using 10 M NaOH and TiO2 anatase powder. The material synthesized was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to ensure the structural and morphological characteristics. The interaction of calf thymus DNA (CT-DNA) and bovine serum albumin protein with suspended aqueous solution of titanate nanotubes was investigated using UV absorption spectroscopy and the apparent association constant was found to be, Kb= 1.68 × 104 M-1 and Kap=5.41 × 103 M-1 for DNA and BSA respectively. Addition of the titanate nano material resulted quenching of fluorescence spectra of ethidium bromide-DNA in tris HCl buffer solution and that of aqueous protein solution. The apparent binding constant (Ksv= 5.46 × 104M-1 for DNA binding and Ksv = 6.063 × 103M-1 for protein binding) was deduced from relevant fluorescence quenching data using Stern-Volmer equation.

The Synthesis, Photoconductivity, Photoinduced Charge Transfer, and Other Properties of HEC-TCNQ

The donor-acceptor complex HEC-TCNQ (HEC = 9-hydroxyethylcarbazole; TCNQ = tetracyanoquinodimethane) has been synthesized. Under the illumination of Ar+ laser, the photoinduced charge transfer salt HEC(+)TCNQ(-) can be formed with a conductivity of at least one order of magnitude larger than that of HEC-TCNQ.

THE EFFECTS OF N-2-HYDROXYETHYL-N-METHYL-p-TOLUIDINE ON METHYL METHACRYLATE RADICAL POLYMERI-ZATION AND ACRYLONITRILE PHOTOINDUCED POLYMERIZATION

The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polymerization and the overall activation energy of polymerization were determined. Based on kinetics study and the end group analysis of the polymer obtained by UV spectrum method, the initiation mechanism is proposed.

Photoinduced Electron Transfer in Host-Guest Complexes of Naphthalene Derivatives with p-NBCD and m-NBCD

A number of naphthalene derivatives containing adamantanamine binding moiety and an （CH2）. （n = 2, 3, 4, 5, 6） spacer were prepared as electron donor. A supramolecular assembly was fabricated by the inclusion complexation of the donor substrates with the host molecules, mono-6-O-p-nitrobenzoyl-β-cyclodextrin （p-NBCD） and mono-6-O-m-nitrobenzoyl-β-cyclodextrin （m-NBCD）, in water. The fluorescence quenching in these systems was studied and detailed Stern-Volmer constants were measured. It revealed that an efficient photoinduced electron transfers （PET） between the naphthalene donors and the cyclodextrin acceptors occurred.

Photoinduced DNA Cleavage of Fullerols,Water-Soluble Polyhydroxylated [C_(60)] Fullerene Derivatives

The effects of polyhydroxylated [C60 ] fullerene derivatives fullerols on DNA was studied, using the piasmid pXJ41-neo DNA as the experimental model. The cleaved DNA products were detected by agarose gel electrophoresis. The results showed that fullerols could stimulate DNA cleavage in dose and irradiation dependent manners. 0.4 mmol/L fullerols together with 1.5 h exposure to a 500 W tungsten halogen lamp at a distance of 20 cm could convert most of plasmid DNA from the intact form into the nicked and linear forms. Scavengers of various reactive oxygen species （ROS） including sodium azide, mannitol and superoxide dismu- tase （SOD） could inhibit the photoinduced DNA cleavage of fuUerols. These data presented for the first time the photoinduced biological activities of fullerols, and implied a possible use of these fullerene derivatives as the candidates for novel photosensitizers in the biomedical therapy.

Review of photoinduced effect in manganite films and their heterostructures

Light–matter interaction plays an important role in the non-equilibrium physics, especially in strongly correlated electron systems with complex phases. Photoinduced effect can cause the variation in the physical properties and produce some emergent phases. As a classical archetype, manganites have received much attention due to their colossal magnetoresistance（CMR） effect and the strong interaction of charge, spin, orbital, and lattice degrees of freedom. In this paper, we give an overview of photoinduced effect in manganites and their heterostructures. In particular, some materials, including ZnO, Si,BiFeO3（BFO）, titanate-based oxides, and 0.7 Pb（Mg（1/3） Nb（2/3））O3-0.3 PbTiO3（PMN-PT） have been integrated with manganites. Heterostructures composed of these materials display some exciting and intriguing properties. We do hope that this review offers a guiding idea and more meaningful physical phenomena will be discovered in active areas of solid state physics and materials science.

Photoinduced Electron Transfer (PET) between C_(60) and Amines in Micelle Solution A Kinetic ESR Study

As indicated by kinetic ESR measurements, the key factor to affect electron recombination in the process of PET between C60 and amines is the space between donor and C60. To increase solubility of C60 in water, it was incorporated into micelle of surfactants. ]

KINETICS AND MECHANISM OF PHOTOINDUCED POLYMERIZATION BY α,α-DIMETHOXY-α-PHENYL ACETOPHENONE

α,α-dimethoxy-α-Phenyl acetophenone (DMPA) is an efficient and thermally stable photoinitiator. Here its spectral characteristics in the transient state were shown. The transient species were identified as a benzoyl radical and a dimethoxyi benzyl radical that played a primary initiation role in polymerization. The kinetics and mechanism of the bulk polymerization of MMA were investigated. The exponent of DMPA concentration and k_p/k_1^(1/2) value were found to be 0.5 and 0.066 mol(-1/2)l^(1/2)s^(-1/2), respectively. The existence of oxygen led to obtain the polymer with higher molecular weight, which can be attributed to the occurrence of the subsequent polymerization induced by active polymer end group. In the photocrosslinking reaction, the dependence of DMPA content on initial rate has been found. A principal reason is that the sample contained higher percentage of DMPA has higher light-absorbed efficiency. In solid film, higher concentration of DMPA is permitted to be used because there is little excited state self-quenching effect in the rigid medium.

PHOTOINDUCED CHARGE TRANSFER POLYMERIZATION OF STYRENE INITIATED BY ELECTRON ACCEPTOR

Photoinduced charge transfer polymerization of styrene(St) with electron acceptor as initiator was investigated. In case of fumaronitrile (FN) or maleic anhydride (MA) as initiator the polymerization takes place regularly, whereas the tetrachloro-1,4-benzenequinone (TCQ), 2,3-dichloro-5, 6-dicyano-1, 4-benzenequinone (DDQ). or tetracyano ethylene (TCNE) as initiator the polymerization proceeds reluctantly only after the photoaddition reaction. A mechanism was proposed that free radicals would be formed following the charge and proton transfer in the exciplex formed between St and electron accepters.

PHOTOINDUCED ALIGNMENT OF OPTICALLY ACTIVE POLYMER CONTAINING A TEMPO RADICAL END GROUP

A new azobenzene side-chain polymer (TEMPO-PAZ) containing TEMPO (4-hydroxy-2, 2, 6, 6-tetramethyl-piperidinooxy) radical end group was synthesized by free radical copolymerization. Photoinduced alignment was studied onthe polymer films at room temperature with linearly polarized light of 514.5 nm, The experimental results showed that themagnetic response intensity of the TEMPO-PAZ could be easily controlled by choosing the appropriate polarized lightirradiating times, presumably due to the nitroxide radical in the TEMPO-PAZ molecular structure. For the polymerinvestigated here, the photoinduced alignment technique was introduced to increase the magnetic response intensity ofpolymer under irradiation, aiming originally at searching for a new photo-active organic magnetic multifunctional materials.On the other hand, experimental results also showed that the TEMPO-PAZ can be used as a material for optical image storage.

PHOTOINDUCED CHARGE TRANSFER REACTION OF BENZOPHENONE WITH AMINE IN VESICLES

Photoinduced charge transfer reaction of benzophenone(BP) with, mine was carried out in the vesicles of dicetyldimethylammonium bromide (DCDAB) over wide ranges of amine concentration (0. 01～4. 0M). Linear plots of φ^(-1) vs. [TEA]^(-1) at low concentration of amine (<0.02M) and Φ^(-1) vs. [TEA]^(-2) at high concentration were obtained. Kinetic data demonstrate that the electron transfer is promoted significantly by DCDAB vesicles and proton transfer becomes more efficient at high Rmlne concentrations, leading to a decrease of Kd/Kr and increase of Kh/Ke. The kinetic expressions of photoreaction of BP bound to DCDAB bilayer are developed.

PHOTOINDUCED INTRAMOLECULAR ELECTRON TRANSFER IN A NOVEL ZINC PHTHALOCYANINE-VIOLOGEN-FERROCENE TRIAD SYSTEM

A novel triad system zinc phthalocyanine-viologen-ferrocene has been synthesized.Photoinduced intramolecular electron transfer in the new triad system was investigated by fluorescence quenching experiment and nanosecond flash photolysis technique,giving a final long-living charge- separated state.A mechanism of two-step charge separation was suggested.

PHOTOINDUCED ELECTRON TRANSFER I.INTER-AND INTRAMOLECULAR QUENCHING OF ZINC PHTHALOCYANINE FLUORESCENCE BY ANTHRAQUINONE

Inter-and intramolecular quenching of zinc phthalocyanine fluorescence by anthraquinone has been studied.The diminutions of fluorescence quantum yield and life-time are due primarily to electron transfer.Apparent electron transfer rate constants were calculated depending on the chain length and solvent polarity.

On-Line Photoinduced Fluorescence for Carbamazepine Determination after Multivariate Optimization

This work presents a simple and sensitive flow injection fluorimetric method for the determination of carbamazepine (CBZ) in pharmaceutical samples. It is based on the fluorescence signal measurement of the product generated by photoinduced (λex = 251 nm;λem = 434 nm) using a flow injection manifold containing an online homemade photoreactor. In order to optimize the experimental setup, the variable conditions were studied using a multivariate optimization method, thus finding the set of optimum parameters according to the evaluated responses (sensitivity and sampling frequency) and minimizing the number of experiments performed. Under optimal experimental conditions, linear relationship with good correlation coefficient (0.9956) was found between the fluorescence intensity and CBZ concentration in the range of 0.13 - 40 μg·mL-1. The limit of detection was 0.04 μg·mL-1. The precision of the method was satisfactory;the values of relative standard deviations were better than 4.36%. The proposed method was validated and successfully applied to the determination of CBZ in pharmaceuticals with good accuracy;being the recovery values from 89.45% - 112.20%.