Photochemistry & Photophysics

This work deals with very thin (14-40 nm) films of a polyester containing diarylethene units in the main chain spin cast on a silicon wafer. By irradiation with UV light the colourless form turns blue due to the appearance of a strong absorption band centred at about 600 nm. The coloured state is thermally stable and the backward conversion can be triggered with visible light. Comparison of broadband (245-1700 nm) spectroscopic ellipsometry data with simulations based on an isotropic, Kramers-Kronig consistent, multiple-resonance model allowed us to determine the complex index of refraction ñ of the film in its blue and colourless forms. The refractive index of the blue phase neatly exceeds that of the transparent form for wavelengths in the NIR. In particular, out of resonance, at l $ 1700 nm, DRe( ñ) $ 0.05. Parallel to the DRe( ñ) increase, the analysis of ellipsometry data suggests a decrease of the film thickness (about 1.5%) during the transition from the open (transparent) to the closed (coloured) form.

Research on Titanium dioxide (TiO2) has attracted extensive interest because of its potential applications to photocatalysis, chemical sensors, solar cell electrodes and hydrogen storage materials. This study investigates the effect of Palladium (Pd) and Silver (Ag) doping on the photocatalytic efficiency of TiO₂ nanoparticles. The effect of modified TiO2 with palladium, silver and co-dopant of palladium and silver on TiO2 with its photocatalytic efficiency was studied using X-ray diffraction (XRD) and Brunauer-Emmet-Teller (BET). The photo-catalysts were prepared by the sol immobilisation method and characterised using XRD and BET techniques. The textural properties, such as surface area and pore size distribution of Ag/TiO2, Pd/TiO2 and Ag/Pd-TiO2, were analysed by using N2 physisorption using a NOVA 2200e. The X-ray diffraction patterns of the dopants were found to be uniform with the standard P25 Degussa TiO2. From the peak formation of anatase and rutile phases, it was found that the Pd/TiO2 formed a uniform matrix of anatase and rutile, indicating that palladium ion disperses evenly on P25 Degussa TiO2. The peak formation on Ag/TiO2 and Pd/AgTiO2 shows the same uniform distribution of silver and palladium ions, only that foreign peaks were observed on the formation of anatase and rutile because of impurity in silver. The crystalline size of the catalyst and full width at half maximum (FWHM) were also calculated at different angles of diffraction. The BET shows that the photocatalysts were mesoporous and had a type IV isotherm. The high mesopore of the catalyst increases its photocatalytic activity, and also type IV isotherm. The BET analysis shows that the pore size distribution of the catalyst is between 2nm and 50nm, which shows that the catalyst Chemistry and Biochemistry: Research Progress Vol. 6 Assessment of the Photo-catalytic Efficiency of Palladium/Silver Doped TiO2 Nanoparticles Using X-ray Diffraction and Brunauer-Emmet-Teller Analysis 124 is mesoporous. It also gives a high surface area with high volume and low pore size (crystalline size), which increases the photocatalytic efficiency. The study concluded that the doping and codoping of palladium and silver on TiO2 improve the photocatalytic activity of P25 degusa TiO2 by producing more active phase (anatase), which favours photocatalysis. So, co-doping of palladium and silver on TiO2 can serve as a strategy for the design of high-performance photocalysts for environmental benefits. These results demonstrate the potential of Pd/Ag codoped TiO₂ for advanced environmental remediation applications.

The effect of laser radiation on the formation of film-like deposits on the surface of optical parts located in closed volumes containing sealants such as VGO-1, KLT-30, U-2-28, and K-68 has been studied. X-ray photoelectron spectroscopy and IR spectroscopy were used to determine the composition of the film-like deposits. The composition of the gas medium was determined by mass spectrometry. The formation kinetics of film-like deposits were investigated as a function of the medium temperature and the laser radiation parameters. Possible formation mechanisms of the  lm-like deposits and methods for their elimination were considered.

A pillared-paddlewheel type metalÀorganic framework material featuring bodipy-and porphyrin-based struts, and capable of harvesting light across the entire visible spectrum, has been synthesized. Efficient-essentially quantitative-strut-to-strut energy transfer (antenna behavior) was observed for the well-organized donorÀacceptor assembly consituting the ordered MOF structure.

Solar irradiated plasmonic Ag-TiO 2 (P25) nanocomposites have proficiently harvested solar energy towards nitroaromatics reduction comparatively to almost irresponsive bare TiO 2 . p-Nitrotoulene (p-NT) and p-nitrobenzaldehyde (p-NBAL) were potentially reduced to p-aminotoulene (p-AT, 87% and 50%) and p-aminobenzaldehyde (p-ABAL, 70% and 38%) with Ag 5 -P25 (5 min photodeposition time (PDT)) and Ag 30 -P25 (30 min PDT) respectively. The focus of this study was mainly on the role of PDT (3-30 min) which was found to be directly co-related with size, distribution and oxidation state of deposited Ag nanoparticles (NPs) over titania surface, responsible for superior photocatalytic activity. HR-TEM images confirmed the average size of Ag nanoparticles to be ~1-2 nm and ~7-8 nm for Ag 5 -P25 and Ag 30 -P25 respectively. Further, XPS analysis suggested the formation of ternary hybrid (Ag 2 O/Ag-P25) in case of 5 min PDT whereas only metallic Ag was found to be photodeposited as the times was increased to 30 min.

The conventional methods of Au co-catalyst deposition onto TiO 2 surfaces generally do not offer fine tuning of the metal-TiO 2 interface for enhanced photoactivity because of the non-uniform distribution of the size and shape of metal nanodeposits. Hence, this study demonstrated the comparative co-catalysis activity imparted to TiO 2 by as-prepared coinage metal (Au, Ag and Cu) quantum dot particles of similar sizes (3-5 nm) as a function of their plasmonic interactions with TiO 2 under visible light irradiation. The physiochemical and interfacial properties of metal-TiO 2 composites are studied by optical band gap, XRD, XPS, TEM, surface area, time resolved spectroscopy, current-voltage characteristics, GC and GC-MS analysis. It was revealed that the optical band gap is shifted to 2.9 eV from 3.2 eV of bare TiO 2 and the specific surface area, 50 m 2 g À1 , of TiO 2 is notably reduced to 20-33 m 2 g À1 after metal nanoparticles impregnation (M-TiO 2 ) that were found to exist in the Au 0 and Ag 0 , and Cu +2 oxidation states. The average relaxation time E18 ms (bare TiO 2 ) o 20 ms (Cu-TiO 2 ) o 24 ms (Au-TiO 2 ) o 27 ms (Ag-TiO 2 ) of photoexcited charge species and the highest conductance value 1.65 Â 10 À7 S of Ag-TiO 2 as revealed by current-voltage studies strongly established that Ag-TiO 2 interface acts as a better electron sink to capture and store photogenerated electrons, thus displaying superior photocatalytic activity than Au/or Cu-TiO 2 interfaces. Thus, Ag-TiO 2 exhibited the highest rate constant k = 4 Â 10 À2 min À1 relative to k = 2.7 Â 10 À2 min À1 (Au-TiO 2 ) and k = 1.93 Â 10 À2 min À1 (Cu-TiO 2 ) for the oxidative degradation of benzaldehyde and nitrobenzaldehyde, respectively, to CO 2 under direct sunlight (40-50 mW cm À2 ) exposure. Scheme 1 Surface plasmon resonance effect of metal nanoparticles (Au, Ag or Cu) for TiO 2 photocatalysis under sunlight irradiation.

You are probably familiar with x-ray radiation therapy for treating cancer. But do you know that x-rays are ionizing radiation that can cause damage to many tissues besides killing cancer cells? Simphotek and others are using near-infrared or "gentle" visible light whose wavelength is longer than x-rays and with much lower energy so that it causes fewer side effects.

This study focused on the photocatalytic decolourization of cobaltous phthalocyaninate dye (PcCo) from ZnO suspension solution under artificial UV-A light. The results showed that the photo-decolourization process of this dye process was obeyed to pseudo-first order kinetics. Moreover, the optimization results explained that the maximum value of decolourization efficiency of this dye was achieved at the conditions: initial dye concentration 25 mg/L and the initial pH of dye aqueous solution is equal to 11.01. Arrhenius plot obtained at temperatures ranged (287.15-303.15) K, which is equal to 28.995 kJ mol-1. The thermodynamic parameters were calculated also and determined that the photoreaction is endothermic and non-spontaneous.

HIGHLIGHTS The luminescence decays of solid samples are often complex due in part to the presence of defects. In the case of these TADF molecular solids, the analysis of the decays after the addition of defects provides the quenching distance of the triplet and singlet states. ABSTRACT Nowadays, Thermally Activated Delayed Fluorescence (TADF) compounds have proven to be attractive for highly efficient optoelectronic devices as they can exploit both singlet and triplet excited states generated by charge recombinations that occur in such devices. However, quenching of excited states limits such benefits at high current densities. We have studied the quenching in the case of cationic copper(I) complexes coordinated by both Nheterolytic carbene (NHC) and 2,2'-dipyridylamine (dpa) ligands. Defects are created in their crystals by a strong laser irradiation. Then we have investigated, by analysing their fluorescence decay as a function of temperature, the quenching mechanism and the exciton mobility. Using a time-resolved version of the Perrin's quenching model, we show that the quenching volume depends on temperature according to the singlet/triplet equilibrium. At room temperature, the singlet states are responsible for 75% of the quenching although they contribute for 2% to the excited states population. From the analysis of the decay curves, we show that the excitons are not mobile in the crystals and are quenched through Förster Resonant Energy Transfer (FRET).

Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol-gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV-DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag-WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag-WZ hetero-interfaces.

Our previous research have demonstrated that 5-aminolevulinic acid (ALA), the precursor in the porphyrin synthesis pathway leads to heme, promotes aerobic energy metabolism via up-regulation of protein levels of mitochondrial respiratory chain complex IV (cytochrome c oxidase, COX) in mouse. On the other hand, tumor cells exhibit the characterized metabolic phenotype, the Warburg effect, which is a shift of ATP generation from oxidative phosphorylation to glycolysis. Moreover, tumor cells have a limited capacity of heme synthesis. Therefore ALA induces the accumulation of porphyrin in tumor cells. Hence, in the present study, we focus on energy and porphyrin metabolism in tumor cells. We examined aerobic respiration activities and porphyrin accumulation levels of human gastric cancer cell lines. COX enzyme activity and oxygen consumption rate in the cell culture medium were measured. The porphyrin accumulation level in tumor cells incubated with ALA was quantitatively determined by fluorescence measurement. COX activities in tumor cells were lower than that in normal cells. These results indicates that a reduction of COX activity is critical factor in the Warburg effect. Furthermore, differences in COX activities, oxygen consumption rates and porphyrin accumulation levels were observed among the cell lines. The cell line which showed high oxygen consumption rate exhibited the low porphyrin accumulation. On the other hand, the cell line which showd low oxygen consumption rate exhibited the high porphyrin accumulation. In the result, these data suggest that there is an inverse correlation between aerobic respiration ability and porphyrin accumulation level.

Simple and efficient photoacid generators (PAGs) for carboxylic and sulfonic acids based on N-acyl-N-phenylhydroxylamines have been demonstrated. Irradiation of o-carboxylates and thermally rearranged o-arenesulfonates of N-acyl-N-phenylhydroxylamines using UV light (!254 nm) in aqueous methanolic solution resulted in efficient generation of carboxylic and sulfonic acids, respectively. The carboxylic acid generation ability of N-acyl-N-phenylhydroxylamines was found to be dependent on their N-acyl substituents. Further, polymer bearing o-arenesulfonates of N-acyl-N-phenylhydroxylamine was synthesized and demonstrated as PAG for sulfonic acids.

A series of Ag-doped TiO 2 composite were obtained by impregnation of the commercial powder TiO 2 by plasma-chemically synthesized silver nanoparticles. The phase structure and morphology of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of Ag content on the antibacterial and photocatalytic activity of nanoparticles was tested. Ag doping also improved the antibacterial and photocatalytic activity of TiO 2 powder. The 2.0 mole % of Ag-doped TiO 2 shows 96% degradation of methylene blue (MB) within 50 min under visible light irradiation and exhibits highest photocatalytic performance.

The adsorptive removal and photocatalytic decolorization of Direct Orange 39 dye were investigated using ZnO as an adsorbent and a photocatalyst. The adsorption and decolorization experiments were performed in the dark and under UV light, respectively. The maximum adsorption capacity and removal percentage (Eremoval%) were investigated in the dark reactions using 25 ppm of dye and 0.20 g from ZnO and pH 10. On the other hand, the decolorization processes were accompanied by the measurement of the apparent rate constant (kapp.) and the efficiency of the photo-decolorization (De %). Several parameters were investigated and the photocatalytic activity of ZnO was optimized at pH 9, and 25 mg/L of Direct Orange 39 dye solution, and 0.35 g of ZnO. The results showed that the decolorization process in which ZnO is used as a photocatalyst is more efficient than the adsorption processes. The highest decolorization efficiency obtained under mentioned conditions was 99.151 % compared to 50.462 % for the adsorption process. The study of activation energy proves that the adsorption of the dye on ZnO surface is physical at low temperatures. Thermodynamic studies showed that the removal process of Direct Orange 39 is an exothermic, less random, and non-spontaneous process, while it was found to be spontaneous, exothermic, and less random for the decolorization process.

This study focused on the photocatalytic decolourization of cobaltous phthalocyaninate dye (PcCo) from ZnO suspension solution under artificial UV-A light. The results showed that the photo-decolourization process of this dye process was obeyed to pseudo-first order kinetics. Moreover, the optimization results explained that the maximum value of decolourization efficiency of this dye was achieved at the conditions: initial dye concentration 25 mg/L and the initial pH of dye aqueous solution is equal to 11.01. Arrhenius plot obtained at temperatures ranged (287.15-303.15) K, which is equal to 28.995 kJ mol-1. The thermodynamic parameters were calculated also and determined that the photoreaction is endothermic and non-spontaneous.

A N-doped titania-silver nanocomposites have been prepared by simple microwave assisted and impregnation-reduction method for the first time. As synthesized nanocomposites with different Ag contents were characterized for their phase purity, morphology, particle size, optical properties and elemental composition. It is found that N-doped TiO 2 silver nanocomposites are pure in anatase phase with an average crystallite size of 10 nm. The catalyst was tested for dye degradation and photodegradation efficiency was found to be 99.6 and 88.7 % within 90 min under UV and sunlight respectively. A 40 % enhancement in the photodegradation efficiency was achieved by Ag loading in comparison with the N-TiO 2 under sunlight. The fluorescence quenching of Ag loaded N-TiO 2 indicates decrease in rate of electron-hole pair recombination that enhances photocatalytic performance. The effects of photocatalytic operational parameters such as method of surface modification, catalyst loading and irradiation sources on the photodegradation of methyl orange were also investigated.

S EVERAL parameters have been studied in this manuscript to investigate the effect of certain conditions on the removal and the decolorization of the textile dyes: reactive yellow 14 (RY 14) and reactive green (RG) dyes from aqueous solution. Parameters such as temperature, initial concentration of dye and initial pH were taken into consideration to reach the perfect removal and decolorization for both dyes. This work was achieved in both dark and photoreaction processes. In dark reaction, the type of adsorption was determined based on Gibb's free energy values, activation energies and change in enthalpies, which were found that the physical adsorption for removal of both dyes is predominated, and the reaction is exothermic. The adsorption capacity and percentage of removal both dyes elevated with raised the dye concentration. The best initial pH for removal of RY 14 and RG dyes dyes was conducted and found equal to 5.14 and 9.75 respectively. The raised in temperature is not enhanced the adsorption process, that due to the dark reaction for both dye is exothermic. The small negative values of change in entropies are proved the associative mechanism of both dyes on ZnO surface. On the other hand, the results under the percent UV-light showed, that the optimal conditions were found at 303.15 K, with 25 ppm and optimum pH=11.01 for reactive green(RG) dye, while the optimum conditions were appearing at 50 ppm and best pH= 6.075 for reactive yellow 14 at same temperature. The decolorization process for both studied dyes was found to be a pseudo-first-order kinetic, fast (low activation energies), endothermic reaction (positive change in enthalpies), non-spontaneous (positive change Gibbs free energies) and less random (negative change in entropies). The photoreaction is a completed to removal process to depress the toxicity for these studied textiles dyes.

S EVERAL parameters have been studied in this manuscript to investigate the effect of certain conditions on the removal and the decolorization of the textile dyes: reactive yellow 14 (RY 14) and reactive green (RG) dyes from aqueous solution. Parameters such as temperature, initial concentration of dye and initial pH were taken into consideration to reach the perfect removal and decolorization for both dyes. This work was achieved in both dark and photoreaction processes. In dark reaction, the type of adsorption was determined based on Gibb's free energy values, activation energies and change in enthalpies, which were found that the physical adsorption for removal of both dyes is predominated, and the reaction is exothermic. The adsorption capacity and percentage of removal both dyes elevated with raised the dye concentration. The best initial pH for removal of RY 14 and RG dyes dyes was conducted and found equal to 5.14 and 9.75 respectively. The raised in temperature is not enhanced the adsorption process, that due to the dark reaction for both dye is exothermic. The small negative values of change in entropies are proved the associative mechanism of both dyes on ZnO surface. On the other hand, the results under the percent UV-light showed, that the optimal conditions were found at 303.15 K, with 25 ppm and optimum pH=11.01 for reactive green(RG) dye, while the optimum conditions were appearing at 50 ppm and best pH= 6.075 for reactive yellow 14 at same temperature. The decolorization process for both studied dyes was found to be a pseudo-first-order kinetic, fast (low activation energies), endothermic reaction (positive change in enthalpies), non-spontaneous (positive change Gibbs free energies) and less random (negative change in entropies). The photoreaction is a completed to removal process to depress the toxicity for these studied textiles dyes.

to-3.0 ~m~. m o l-~. This estimated value agrees well with AVO found experimentally in the present work for model B. For model A a AVO value of only about-1.2 cm3.mol-' would result from the experiments for each of the two H bonds in a cyclic dimer; since departure from bond linearity should decrease the absolute value of AVO, such a small AVO value, however, seems still reasonable. Comparison of the theoretically estimated AV with the AVO values determined experimentally must not be physically significant in any case because AVO is the difference of partial molar volumes a t infinite dilution. In the case of phenol in CC14, however, this comparison seems to be allowed since mixtures of liquid phenol with CCll exhibit nearly ideal V,,,(X) behavior3v2' (where V, is the molar volume) giving evidence that the reaction volumes presented in this paper are a measure for the volume change in forming the dimer from two monomers. Acknowledgment. The authors thank one of the reviewers for helpful suggestions for the revision of the manuscript. Financial support of the Fonds der Chemischen Industrie e.V. is gratefully acknowledged. References and Notes

The present study deals with studied the essential requirements for photo-decoulorization of nigrosine dye with suspension solution of photocatalyst (ZnO), under 250 Watt UV-A light (I o = 1.47 × 10 −7 ensien s −1). A kinetics study of photo-decolourization for this dye was obeyed to pseudo-first order. The best initial pH of decolorization at 25 mg/L of dye solution with 300 mg of ZnO was given a fast reaction at 8.17. The calculated activation energy for this photoreaction was found to be 31.549 kJ•mol −1. Thermodynamically, the reaction is exothermic and spontaneously. The efficiency of decolorizatio E% was 97.077 at 15 min that decreased with addition oxidant reagents such as H 2 O 2 , Fe 2+ and mixture from them.

The adsorptive removal and photocatalytic decolorization of Direct Orange 39 dye were investigated using ZnO as an adsorbent and a photocatalyst. The adsorption and decolorization experiments were performed in the dark and under UV light, respectively. The maximum adsorption capacity and removal percentage (Eremoval%) were investigated in the dark reactions using 25 ppm of dye and 0.20 g from ZnO and pH 10. On the other hand, the decolorization processes were accompanied by the measurement of the apparent rate constant (kapp.) and the efficiency of the photo-decolorization (De %). Several parameters were investigated and the photocatalytic activity of ZnO was optimized at pH 9, and 25 mg/L of Direct Orange 39 dye solution, and 0.35 g of ZnO. The results showed that the decolorization process in which ZnO is used as a photocatalyst is more efficient than the adsorption processes. The highest decolorization efficiency obtained under mentioned conditions was 99.151 % compared to 50.462 % for the adsorption process. The study of activation energy proves that the adsorption of the dye on ZnO surface is physical at low temperatures. Thermodynamic studies showed that the removal process of Direct Orange 39 is an exothermic, less random, and non-spontaneous process, while it was found to be spontaneous, exothermic, and less random for the decolorization process.

Prostate cancer is the most common cancer in American men, aside from skin cancer. As an alternative cancer treatment, photodynamic laser therapy (PDT) can be used to induce cell death. We evaluated the PDT effect, using methylene blue as a photosensitizer, in human prostate tumor cells (PC3). PC3 were subjected to four different conditions: DMEM (control); laser treatment (L-660 nm, 100 mW, 100 J.cm −2); methylene blue treatment (MB-25 μM, 30 min), and MB treatment followed by low-level red laser irradiation (MB-PDT). Groups were evaluated after 24 h. MB-PDT treatment reduced cell viability and migration. However, because MB-PDT did not significantly increase the levels of active caspase-3 and BCL-2, apoptosis was not the primary mode of cell death. MB-PDT, on the other hand, increased the acid compartment by 100% and the LC3 immunofluorescence (an autophagy marker) by 254%. Active MLKL level, a necroptosis marker, was higher in PC3 cells after MB-PDT treatment. Furthermore, MB-PDT resulted in oxidative stress due to a decrease in total antioxidant potential, catalase levels, and increased lipid peroxidation. According to these findings, MB-PDT therapy is effective at inducing oxidative stress and reducing PC3 cell viability. In such therapy, necroptosis is also an important mechanism of cell death triggered by autophagy.

The molecular weight distribution (MWD), formed during random crosslinking of polymers whose initial molecular weight distribution is given by the Schulz-Zimm distribution, is proposed. The obtained equation can be considered as a good approximation even for nonrandom crosslinking reactions such as free-radical and living crosslinking copolymerizations. When the initial molecular weight distribution is very narrow, namely, the polydispersity index (P, /Pn) is smaller than about 1,1, a multimodal distribution can be obtained. Quite often the MWD is represented solely by the average molecular weights such as number-and weight-average molecular weights in conventional approaches; however, such types of measure can not give enough description for multimodal distributions. Multimodal distributions may be obtained for the primary polymer molecules formed via living polymerizations. On the other hand, for the primary polymer molecules formed by free-radical polymerization whose polydispersity index must be larger than 1 3 , it is impossible to form a bimodal distribution as long as nonideal kinetics such as the size and structure dependence of crosslinking reactions are neglected.

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Esophageal cancer is the sixth most common cause of cancer-related death worldwide. Current chemotherapy regimens include a combination of 5-fluorouracil (5-FU) and cisplatin, but more efficient therapy strategies are needed to increase 5-year survival. Alterations in the signaling pathway of the tumor suppressor gene Rb-1, which encodes a phosphoprotein (pRB) that negatively regulates the G1/S transition of the cell cycle, are present in 70% of all tumors, but its role in esophageal cancer is still unclear. Most of these are alterations leading to up-regulation of the activity of cyclin-dependent kinases (CDKs) to phosphorylate pRB, which suggests that keeping the wild type pRB phosphorylated might be advantageous. Besides proliferation, pRB also regulates apoptosis induced by tumor necrosis factor-alpha (TNF-α) and DNA-damage. We investigated the status of phosphorylation of pRB along esophageal tumorigenesis stages, as well as whether hyperphosphorylation of pRB could suppress ap...

This work demonstrates that the fungicide thiophanate-methyl generates a sensitizing photoproduct upon irradiation in solar light and explains how the reaction proceeds. The degradation profileof aqueous thiophanatemethyl in simulated solar light showed an autoaccelerated shape indicating the formation of some photodegrading compounds. Among the detected photoproducts, I (λ max = 340 nm), a quinoxaline derivative generated in the very beginning of the reaction seemed to be the molecule responsible for this autoacceleration. Further experiments were conducted to confirm this hypothesis. The laser flash photolysis (λ exc = 355 nm) of I generated a transient species reminiscent to the triplet excited state of unsubstituted quinoxaline. The two triplets reacted with the phenolic probe, 2,4,6-trimethylphenol, with k = 2 × 10 9 M −1 s −1. Steady-state irradiations showed that thiophanate-methyl drastically accelerated the photolysis of the probe in an auto-accelerated reaction confirming the production of a sensitizing photoproduct. Moreover, unsubstituted quinoxaline sensitized the degradation of thiophanate-methyl showing that this latter contains labile H atoms. All these data confirmed that I was the sensitizer responsible for the auto-accelerated light induced transformation of thiophanate-methyl. The mechanism of formation of I was studied by quantum calculations. It proceeds through photocyclisation to form a SeS bridge, followed by intra and intermolecular H abstractions and finally departure of HSS. The sensitizing properties of micropollutants photoproducts open a large array of investigations. Our study provides a reliable approach to investigate the overlooked photosensitizing effect of photoproducts during photochemical reactions in water and opens the way to a vast array of research.

Soluble bio-based substances (SBO) isolated from urban waste promote the photodegradation of chlorophenols and the system detoxification. 2-chlorophenol, 3-chlorophenol and 4-chlorophenol were used as probe substrates. Experiments performed with 1.0x10-4 M substrate solutions irradiated for 24 h with UVa-vis light (λ > 340 nm) in the presence 500 mg L-1 SBO showed the progressive degradation of all the probe substrates. The experimental data were fitted to a pseudofirst order kinetics and the rate constant was found to decrease following the order: 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. Experiments performed at different pH showed that the reaction rate was higher at pH value where the substrates are mainly present in ionized form. Additional experiments performed in the presence of singlet oxygen and hydroxyl radical scavengers, and EPR measurements further supported the main role of singlet oxygen in the substrate photodegradation mechanism. Data collected at variable SBO concentration showed that the substrate photodegradation rate increased upon increasing SBO concentration, up to a plateau value occurring in the presence of 1 g L-1 SBO. Possible explanations for this behaviour are discussed.

Hybrid fluorescent metal−organic frameworks (MOFs) use long-range intermolecular structural motifs in which the properties of the scaffold molecular system can be designed for specific applications. In this work, we constructed a MOF−chromophore system with a strongly polarized fluorescence and a large emission wavelength shift. To achieve this, we first devised a fluorophore with a linear conjugated backbone, bulky and noninteracting side chains, and easily accessible nitrogen atoms on its pyridine end groups. The linear nature of the conjugated backbone can lead to a strongly polarized luminescence, the side groups assist structural stability and minimize intermolecular interactions, and the sterically accessible pyridines provide a large fluorescence colorchanging ability. These features were demonstrated by synthesizing a planar Zn-based MOF in which the linear backbone of the chromophore molecules was highly aligned. The MOFs demonstrated a strong polarization effect and a color-shifting ability from green-yellow to orange. The results show that hybrid metal−organic materials can be designed to generate a strong command of the material luminescence, in terms of both emission color and polarization.

Cancer has been a serious threat and impact on the health and life of human. Phototherapy is considered as a promising therapeutic method to replace the traditional treatment in clinic owing to its noninvasive nature and high efficiency. Photoinitiators have long been used in the field of photopolymerization; however, few studies have been carried out on their potential as anticancer agents under light irradiation. In this study, the effect of a photoinitiator, diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO), on breast cancer is investigated and the related mechanism is elucidated. It is found that TPO has low dark toxicity and significant phototoxicity. TPO can inhibit cell growth and development and promote cell apoptosis through a mitochondrial pathway under light irradiation. Further studies show that cell apoptosis is induced by free radicals produced from the photolysis of TPO to activate JNK phosphorylation. Overall, we identify the antitumor effects of TPO in vitro...

Pulsed F T proton magnetic resonance measurements and chemical shift analysis have been carried out in order to determine the dynamic solubilization site of the pyrene chromophore in cationic micellar solutions of pyrene, pyrene butyric acid (PBA), and pyrene sulfonic acid (PSA). Pyrene is solubilized in the interior of cetyltrimethyl ammonium bromide (CTAB) micelles while the pyrene chromophore of PBA and PSA is located in the outer core and surface region of the micelle, respectively. PSA and PBA in aqueous and micellar solutions were excited with 347.1-nm ruby laser light. The fluorescence lifetime of PSA is 62 nsec in water and 140 or 30 nsec in micellar solution of dodecyltrimethyl ammonium chloride (DTAC) or CTAB; for PBA the respective values are 140, 200, and 158 nsec. These results are explained in terms of stabilization of the excited singlet states of the probes by the micellar environment and quenching by Br-counterions. For PBA the quenching efficiency of Br-is much lower than for PSA due to the larger separation of the pyrene ring from the micellar Stern layer. The 347.1-nm laser photolysis of PSA and PBA in water also produces a large yield of hydrated electrons via a biphotonic photoionization process. In the case of PSA the photoionization is strongly inhibited by cationic micelles.

A heterobifunctional photocleavable cross-linker based on an o-nitrobenzyl ester moiety was synthesized. The cross-linker has N-hydroxysuccinimidyl and disulfide groups attached at each end and thus can anchor a protein to a gold-coated substrate surface. Steady-state spectroscopic studies suggest that the cross-linker undergoes a clean CO fragmentation upon irradiation with a quantum yield of 0.1. Consequently, immobilized proteins (such as avidin or antibodies) on a substrate surface can be released efficiently (>95%) under UV irradiation (λ > 300 nm) without degrading the protein functionality. We also demonstrated protein delivery via bioconjugation of protein molecules to a goldcoated atomic-force microscope (AFM) tip. When the proteins are photoreleased from the AFM tip, they are delivered to the substrate surface as protein clusters of uniform size. This has been confirmed using both AFM and fluorescence microscopy. The application of bioconjugation in this study opens a new avenue for tunable surface modification and controllable protein delivery in studies of biological systems on the nanometer scale.

The reactions of primary and secondary amines with 7,7,8,8-tetracyano-p-quinodimethane(TCNQ) lead to mono- and di-substituted adducts. Fluorescence emission has been observed for several of these compounds. The luminescence property of the TCNQ adducts, 2-{4-[(2,6-dimethylmorpholin-4-yl)(4-methylpiperidin-1-yl)methylene]cyclohexa-2,5-dien-1-ylidene}malononitrile (MORPIP) and 2-{4-[cyclohex-1-yltetrahydropyrimidin-2(1H)-ylidene]cyclohexa-2,5-dien-1-ylidene}malononitrile (AMINO) were investigated in a variety of environments. These included alcohol solutions and crystals at room temperature and glass forming solvents and polymer films as a function of temperature. The fluorescence quantum yields and Stokes' shifts were found to be very sensitive to the matrix. Crystal structure data show that the molecules are non-planar in the ground state. The matrix effect is discussed in terms of the conformational change during photo-excitation and the constraint imposed on this by the matrix.

Highlights A full photophysical characterisation has been carried out on the plant growth regulator 2-(1-naphthyl) acetamide these shows a marked solvent dependence the compound acts as a relatively strong excited state oxidant sensitised singlet oxygen reactions compete with electron transfer in the excited state reactivity this may be important in the photoreactivity under environmental conditions

Cytochrome c-mediated apoptosis in cells submitted to photodynamic therapy raises the question about the ability of photodynamically oxidized cytochrome c (cytc405) to trigger apoptosis as well as the effect of membranes on protein photo-oxidation. Cytochrome c was submitted to irradiation in the presence of MB ؉ in phosphate buffer and in the presence of four types of phosphatidylcholine/phosphatidylethanolamine/cardiolipin (PCPECL) liposomes (50/30/20%): totally saturated lipids (tsPCPECL), totally unsaturated lipids (tuPCPECL), partially unsaturated (80%) lipids, with unsaturation in the PC and PE content (puPCPECL80), and partially unsaturated (20%) lipids, with unsaturation in the CL content (puPCPECL20). Cytc405 was formed by irradiation in buffered water and in tsPCPECL and puPCPECL20 liposomes. In the presence of tuPCPECL and puPCPECL80, cytochrome c was protected from photodynamic damage (lipidprotected cytochrome c). In CL liposomes, 25% unsaturated lipids were enough to protect cytochrome c. The presence of unsaturated lipids, in amounts varying according to the liposome composition, are crucial to protect cytochrome c. Interesting findings corroborating the unsaturated lipids as cytochrome c protectors were obtained from the analysis of the lipid-oxidized derivatives of the samples. Native cytochrome c, lipid-protected cytochrome c, and cytc405 were microinjected in aortic smooth muscle cells. Apoptosis, characterized by nucleus blebbing and chromatin condensation, was detected in cells loaded with native and lipid protected cytochrome c but not in cells loaded with cytc405. These results suggest that photodynamic therapy-promoted apoptosis is feasible due to the protective effect of the mitochondrial lipids on the cytochrome c structure and function.

Solar fuels production is a cornerstone in the development of emerging sustainable energy conversion and storage technologies. Light-induced H 2 production from water represents one of the most crucial challenges to produce renewable fuel. Metal−organic frameworks (MOFs) are being investigated in this process, due to the ability to assemble new structures with the use of suitable photoactive building blocks. However, the identification of the reaction intermediates remains elusive, having negative impacts in the design of more efficient materials. Here, we report the synthesis and characterization of a new MOF prepared with the use of bismuth and dithieno[3,2b:2′,3′-d]thiophene-2,6-dicarboxylic acid (DTTDC), an electron-rich linker with hole transport ability. By combining theoretical studies and time-resolved spectroscopies, such as core hole clock and laser flash photolysis measurements, we have completed a comprehensive study at different time scales (fs to ms) to determine the effect of competitive reactions on the overall H 2 production. We detect the formation of an intermediate radical anion upon reaction of photogenerated holes with an electron donor, which plays a key role in the photoelectrocatalytic processes. These results shed new light on the use of MOFs for solar fuel production.

Despite the recent increase in PPDT2FBT polymer thin film applications for optoelectronic devices, a comprehensive study of this material's optical dispersion properties is unavailable. The optical properties of the PPDT2FBT thin film is investigated using variable-angle spectroscopic ellipsometry (VASE) at ambient conditions. Knowledge of optical dispersion properties is essential for designing and fabricating optoelectronic devices such as solar cells, photodetectors, and photodiodes. In this research, we determined the dielectric function of PPDT2FBT thin film using the B-spline model and then reproduced the dielectric function using Psemi-Tri oscillators. We estimated the refractive index (n) of the thin film to be between 2.00 and 2.15 and the extinction coefficient (k) to be in the range of 1.14-1.39 at a wavelength of 632.8 nm. We further verified the estimated optical properties from the model using directly measured quantities such as transmission and absorption data obtained using the ultraviolet-visible (UV-Vis) spectrometer and thicknesses obtained using a surface profilometer. In addition, we determined the optical band gap of PPDT2FBT using the absorption coefficient.

A pillared-paddlewheel type metalÀorganic framework material featuring bodipy-and porphyrin-based struts, and capable of harvesting light across the entire visible spectrum, has been synthesized. Efficient-essentially quantitative-strut-to-strut energy transfer (antenna behavior) was observed for the well-organized donorÀacceptor assembly consituting the ordered MOF structure.

Photoinduced electron transfer in donor-bridge-acceptor systems with zinc porphyrin (or its pyridine complex) as the donor and gold(III) porphyrin as the acceptor has been studied. The porphyrin moieties were covalently linked with geometrically similar bridging chromophores which vary only in electronic structure. Three of the bridges are fully conjugated π-systems and in a fourth, the conjugation is broken. For systems with this bridge, the quenching rate of the singlet excited state of the donor was independent of solvent and corresponded to the rate of singlet energy transfer expected for a Förster mechanism. In contrast, systems with a π-conjugated bridging chromophore show a solvent-dependent quenching rate that suggests electron transfer in the Marcus normal region. This is supported by picosecond transient absorption measurements, which showed formation of the zinc porphyrin radical cation only in systems with π-conjugated bridging chromophores. On the basis of the Marcus and Rehm-Weller equations, an electronic coupling of 5-20 cm-1 between the donor and acceptor is estimated for these systems. The largest coupling is found for the systems with the smallest energy gap between the donor and bridge singlet excited states. This is in good agreement with the coupling calculated with quantum mechanical methods, as is the prediction of an almost zero coupling in the systems with a nonconjugated bridging chromophore.

This study focused on the photocatalytic decolourization of cobaltous phthalocyaninate dye (PcCo) from ZnO suspension solution under artificial UV-A light. The results showed that the photo-decolourization process of this dye process was obeyed to pseudo-first order kinetics. Moreover, the optimization results explained that the maximum value of decolourization efficiency of this dye was achieved at the conditions: initial dye concentration 25 mg/L and the initial pH of dye aqueous solution is equal to 11.01. Arrhenius plot obtained at temperatures ranged (287.15-303.15) K, which is equal to 28.995 kJ mol-1. The thermodynamic parameters were calculated also and determined that the photoreaction is endothermic and non-spontaneous.

Photodynamic Therapy, a new approach in the treatment of oral cancer Terapia Fotodinámica, un nuevo acercamiento en el tratamiento del cáncer oral RESUMÉN La incidencia del cáncer de cabeza y cuello es aproximadamente 640.000 casos nuevos por año. El cáncer oral representa un tercio de todos los cánceres y es el octavo más diagnosticado en hombres. Los tratamientos más usados para estos tumores son la cirugía, radioterapia, quimioterapia, o una combinación de estas modalidades terapéuticas. Debido al gran deterioro estructural, funcional y estético que causan los tratamientos convencionales, muchos estudios buscan nuevos métodos para remplazar o asistir el tratamiento del cáncer oral. La terapia fotodinámica (PDT) es una nueva modalidad promisoria en el tratamiento del cáncer que apenas está siendo usada clínicamente. Este artículo describe el uso de PDT como una alternativa para el tratamiento del cáncer oral. Salud UIS 2010; 42: 167-174 Palabras clave: Terapia fotodinámica, cáncer...