Search

Abstract: Over the last three decades, a handful of photochemical mechanisms have been applied to a large number of nanoscale assemblies that encapsulate a payload to afford spatio-temporal and remote control over activity of the encapsulated payload. Many of these systems are designed with an eye towards biomedical applications, as spatio-temporal and remote control of bioactivity would advance research and clinical practice. This review covers five underlying photochemical mechanisms that govern the activity of the majority of photoresponsive nanocarriers: 1. photo driven isomerization and oxidation, 2. surface plasmon absorption and photothermal effects, 3. photo driven hydrophobicity changes, 4. photo driven polymer backbone fragmentation and 5. photo driven de-crosslinking. The ways in which these mechanisms have been incorporated into nanocarriers and how they affect release are detailed, as well as the advantages and disadvantages of each system. [Copyright &y& Elsevier]

Abstract: In this study, the novel metal-free (4) and zinc (II) (5) phthalocyanine compounds substituted with four 1-(2-oxyethyl)-4-piperidone ethylene ketal functional groups at peripheral positions have been prepared. These new phthalocyanine compounds have been characterized by IR, 1H NMR, 13C NMR spectroscopy, MS spectral data and elemental analysis. The synthesized phthalocyanine compounds exhibited excellent solubility in common organic solvents and the zinc (II) phthalocyanine complex (5) showed J-type aggregation in chloroform. The photophysical and photochemical properties of metal-free (4) and zinc (II) (5) phthalocyanine complexes were also investigated in DMSO. The investigation of the photophysical and photochemical properties of photosensitizers is very useful for photodynamic therapy (PDT) applications. [Copyright &y& Elsevier]

The fruit of the cherry tomato (Lycopersicon esculentum (Solanaceae)) was analysed for mineral and antinutrient composition. Phosphorus (33.04 ± 0.21 mg/100g) was the most abundant mineral in the fruit, followed by calcium (32.04 ± 0.06 mg/100g), and potassium (11.9 ± 0.1 mg/100g) and manganese (9.55 ± 0.28 mg/100g) were also present in appreciable quantities. Antinutrients, including phytate, glycoside, saponin and tannin, were screened and quantified. Phytate (112.82 ± 0.1 mg/100g), glycoside (2.33 ± 0.00 mg/100g), saponin (1.31 ± 0.00 mg/100g) and tannin (0.21 ± 0.00 mg/100g) were present in the fruit but phlobatanin and glycosides with steroidal rings were not found. The calculated calcium:phytate ratio of the fruits was below the critical value and the calculated [calcium] [phytate]:[zinc] molar ratio was less than the critical value. The calcium:phosphorus ratio (0.97 mg/100g) shows the fruit to be a good source of food nutrients, while the sodium:potassium value was less than 1. Ca/P ratio below 0.5 indicates deficiency of these minerals while Na/K ratio above 1 is detrimental because of excessive sodium levels. The results of the study generally revealed the fruit to be rich in minerals but containing insufficient quantities of antinutrients to result in poor mineral bioavailability. [ABSTRACT FROM AUTHOR]

The photoelectrical properties of highly ordered TiO2 nanotube (TNT) arrays have been systematically and quantitatively studied and found to be closely related to their geometric and crystal structures. The geometric characteristics, including the nanotube diameter and length, were modified by adjusting the anodization potentials and durations, while the crystal structure was modified by thermal annealing at different temperatures. The nanotube array samples with the mixed crystalline phases possess higher photoconversion efficiency than those with the single anatase or rutile phase. The optimal content of rutile phase is about twice of that of anatase phase. In terms of the influence of the geometric structure, the TNT arrays with larger inner diameters and longer tube lengths have better photoelectrical properties. A geometric roughness factor has been applied to describe the combinative effect of the geometric characteristics. The TNT sample with the geometric roughness factor of 125.32 shows the superior photoconversion efficiency of 13.2%. The underlying mechanism has also been discussed in detail. [ABSTRACT FROM PUBLISHER]

Abstract: A new distannyl complex of the (η5-C5H5)Fe(CO)2 (Fp) system, FpSn t Bu2Sn t Bu2Cl (1), is formed by the reaction between Fp−Na+ and Cl t Bu2SnSn t Bu2Cl in hexane. Reaction of 1 with NaOMe (also in hexane solvent) yields FpSn t Bu2Sn t Bu2OMe (2). Both 1 and 2 are characterized by 13C, 29Si and 1H NMR spectroscopy, elemental analyses and single crystal X-ray diffraction. Both complexes are observed to thermally, and photochemically, transform to (η5-C5H5)Fe(CO)(Sn t Bu2)2X (X=Cl, OMe) involving a bridging Cl or OMe between the stannylene units. [Copyright &y& Elsevier]

Introduction: In the nuclear industry 1,4-dioxane is used as a solvent in liquid scintillation technique for measuring low-energy beta-emitters such as H or C in aqueous media. Improper disposal of 1,4-dioxane can contaminate the ground and surface waters. Conventional wastewater treatment processes like chemical treatment, air stripping, carbon adsorption, and biological treatment are ineffective for the degradation of 1,4-dioxane. Methods: In the present study, the kinetics of degradation of 1,4-dioxane using advanced oxidation processes viz., HO alone, Fe(II) + HO, UV (15 W) + HO, UV (15 W) + Fe(II) + HO, US (130 KHz) + Fe(II) + HO, and sunlight + Fe(II) + HO at pH 3.0 was investigated. The optimization of Fe (II) for the processes using Fe (II) + HO was carried out. Conclusions: The kinetics of degradation using sunlight + Fe (II) + HO was found to be fastest when compared to the other processes. The degradation was found to follow first-order kinetics. Formation of acidic intermediates was suspected from the observed pH changes during the degradation processes. [ABSTRACT FROM AUTHOR]

Abstract: The photoreceptor/RPE complex must maintain a delicate balance between maximizing the absorption of photons for vision and retinal image quality while simultaneously minimizing the risk of photodamage when exposed to bright light. We review the recent discovery of two new effects of light exposure on the photoreceptor/RPE complex in the context of current thinking about the causes of retinal phototoxicity. These effects are autofluorescence photobleaching in which exposure to bright light reduces lipofuscin autofluorescence and, at higher light levels, RPE disruption in which the pattern of autofluorescence is permanently altered following light exposure. Both effects occur following exposure to visible light at irradiances that were previously thought to be safe. Photopigment, retinoids involved in the visual cycle, and bisretinoids in lipofuscin have been implicated as possible photosensitizers for photochemical damage. The mechanism of RPE disruption may follow either of these paths. On the other hand, autofluorescence photobleaching is likely an indicator of photooxidation of lipofuscin. The permanent changes inherent in RPE disruption might require modification of the light safety standards. AF photobleaching recovers after several hours although the mechanisms by which this occurs are not yet clear. Understanding the mechanisms of phototoxicity is all the more important given the potential for increased susceptibility in the presence of ocular diseases that affect either the visual cycle and/or lipofuscin accumulation. In addition, knowledge of photochemical mechanisms can improve our understanding of some disease processes that may be influenced by light exposure, such as some forms of Leber''s congenital amaurosis, and aid in the development of new therapies. Such treatment prior to intentional light exposures, as in ophthalmic examinations or surgeries, could provide an effective preventative strategy. [Copyright &y& Elsevier]

The Photochemical and photocatalytic reactions of DDVP (Dichlorvos) have been studied in presence of ultra violet light. The effect of pH, effect of concentration, effect of amount of semiconductor and effect of semiconductor, effect of intensity of light have been investigated intensively. The results obtained during the course of present investigations clearly indicate that the photolysis of dichlorvos is fastest in the ultraviolet light in the presence of semiconductors. The reaction is much slow without catalyst. A tentative mechanism has been proposed for the photochemical reaction. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and characterization of new peripherally tetra-3,5-dimethylpyrazole-1-methoxy substituted metal-free (4), zinc (5), nickel (6), cobalt (7), copper (8) and lead (9) phthalocyanines are described for the first time in this study. The photophysical (fluorescence quantum yields and fluorescence lifetimes) and photochemical (photodegradation and singlet oxygen quantum yields) properties of metal-free (4), zinc (5) and lead (9) phthalocyanines are studied in dimethylsulfoxide (DMSO). Nickel (6), cobalt (7) and copper (8) phthalocyanines (6–8) did not evaluate for this purpose due to transition metal and paramagnetic behavior of central metals in the phthalocyanine cavity. The fluorescence quenching behavior of metal-free (4), zinc (5) and lead (9) phthalocyanines are also investigated. The fluorescence emissions of these phthalocyanines are effectively quenched by 1,4-benzoquinone in DMSO. [Copyright &y& Elsevier]

Abstract: In this study, TiO2−x N x /TiO2 double layers thin film was deposited on ZnO (80nm thickness)/soda–lime glass substrate by a dc reactive magnetron sputtering. The TiO2 film was deposited under different total gas pressures of 1Pa, 2Pa, and 4Pa with constant oxygen flow rate of 0.8sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2sccm in constant total gas pressure of 4Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600°C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet–visible light (UV–vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (∼1/5) of TiO2 film thickness, the optical transmittance of TiO2−x N x /TiO2 film was compared with TiO2 thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light. [Copyright &y& Elsevier]

Abstract: This study presents outcomes from a preliminary dispersion modeling exercise for the extent of aerosol loading owing to enhanced biomass combustion in the future energy mix. Secondary aerosol generation potential from photochemical interactions between the precursor emissions from a typical biomass based combined heat and power (CHP) plant and the associated local emissions from harvest and transportation of the biofuels has been estimated for a peri-urban site in the UK. The study provides results for two options – one, direct firing of the energy crop (miscanthus) i.e. base case; two, biomass gasification prior to combustion i.e. mitigation. We demonstrate that on considering the main life cycle stages of biofuel use i.e. harvest, transportation and combustion, the overall effect of the mitigation option is trivial. This is primarily due to increased emissions from harvest and transportation stages while meeting additional biomass feedstock demands incurred in achieving identical energy output as the base case. [Copyright &y& Elsevier]

Abstract: Heparosan is a polysaccharide, which serves as the critical precursor in heparin biosynthesis and chemoenzymatic synthesis of bioengineered heparin. Because the molecular weight of microbial heparosan is considerably larger than heparin, the controlled depolymerization of microbial heparosan is necessary prior to its conversion to bioengineered heparin. We have previously reported that other acidic polysaccharides could be partially depolymerized with maintenance of their internal structure using a titanium dioxide-catalyzed photochemical reaction. This photolytic process is characterized by the generation of reactive oxygen species that oxidize individual saccharide residues within the polysaccharide chain. Using a similar approach, a microbial heparosan from Escherichia coli K5 of molecular weight >15,000 was depolymerized to a heparosan of molecular weight 8000. The 1H NMR spectra obtained showed that the photolyzed heparosan maintained the same structure as the starting heparosan. The polysaccharide chains of the photochemically depolymerized heparosan were also characterized by electrospray ionization-Fourier-transform mass spectrometry. While the chain of K5 heparosan starting material contained primarily an even number of saccharide residues, as a result of coliphage K5 lyase processing, both odd and even chain numbers were detected in the photochemically depolymerized heparosan. These results suggest that the photochemical depolymerization of heparosan was a random process that can take place at either the glucuronic acid or the N-acetylglucosamine residue within the heparosan polysaccharide. [Copyright &y& Elsevier]

Abstract: A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W18O49 nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W18O49 NRs sensors exhibit superior reducing gas-sensing properties to those of bare W18O49 NRs, and they are highly selective and sensitive to NH3, acetone, and H2S with short response and recovery times. The Ag/AgCl/W18O49 NRs photocatlysts also possess higher photocatalytic performance than bare W18O49 NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W18O49 NRs composite were proposed. [Copyright &y& Elsevier]

Iron in water presents health hazard, its presence in water may cause taste and staining problems. Currently applied water treatment techniques consist of a combination of different methods to achieve the elimination of harmful pollutants. The aim of this study is to investigate the efficiency of the photo-assisted electrochemical oxidation process for the removal of dissolved iron as a cheaper technology. This process could be used at room temperature and low pressure without the need for special equipment and complex operation. The photo-electrochemical cell used in this study was composed of carbon cathode, aluminum anode and high pressure mercury lamp. The effect of the irradiation time, initial concentration of iron, amount of electrolyte and current intensity on the removal efficiency of iron was investigated through series of batch runs in a photo-electrochemical reactor. Results indicated that higher iron removal was obtained at neutral pH of the solution, 20 min irradiation time, 125 ppm of NaCl as electrolyte and (0.25 A) current intensity. By this technique, the ferrous ion was oxidized and is precipitated easily as ferric ions. [ABSTRACT FROM AUTHOR]

Abstract: The mechano-chemical degradation of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(n-butyl methacrylate) (PBMA) using ultrasound (US), ultraviolet (UV) radiation and a photoinitiator (benzoin) has been investigated. The degradation of the polymers was monitored using the reduction in number average molecular weight (Mn ) and polydispersity (PDI). A degradation mechanism that included the decomposition of the initiator, generation of polymer radicals by the hydrogen abstraction of initiator radicals, reversible chain transfer between stable polymer and polymer radicals was proposed. The mechanism assumed mid-point chain scission due to US and random scission due to UV radiation. A series of experiments with different initial Mn of the polymers were performed and the results indicated that, irrespective of the initial PDI, the PDI during the sono-photooxidative degradation evolved to a steady state value of 1.6±0.05 for all the polymers. This steady state evolution of PDI was successfully predicted by the continuous distribution kinetics model. The rate coefficients of polymer scission due to US and UV exhibited a linear increase and decrease with the size of the alkyl group of the poly(alkyl methacrylate)s, respectively. [ABSTRACT FROM AUTHOR]

The ability of light to enact damage on the neurosensory retina and underlying structures has been well understood for hundreds of years. While the eye has adapted several mechanisms to protect itself from such damage, certain exposures to light can still result in temporal or permanent damage. Both clinical observations and laboratory studies have enabled us to understand the various ways by which the eye can protect itself from such damage. Light or electromagnetic radiation can result in damage through photothermal, photomechanical, and photochemical mechanisms. The following review seeks to describe these various processes of injury and many of the variables, which can mitigate these modes of injury. [ABSTRACT FROM AUTHOR]

This review focuses on recent developments in the study of hydrogen generation from water splitting using photoelectrochemical (PEC) cells based on metal oxide (MO) nanomaterials. The emphasis is on the unique properties of MO nanostructures and their advantages as well as limitations for PEC solar hydrogen generation. While abundant and stable, metal oxide nanomaterials tend to have weak visible light absorption that limits their use for solar energy conversion. In addition, MO nanomaterials tend to exhibit a high density of trap states or defect sites that limit their overall efficiency. Different strategies have been developed to enhance visible light absorption (e.g., doping, dye, or quantum dot sensitization and band structure engineering using composite structures) as well as to enhance transport by reducing the density of trap states via surface modification, improving crystallinity, or using 1D structures. In some cases, combining different strategies has led to strong synergistic effects. Recent studies point to the importance and promise of engineering electronic band structure for improving PEC performance of MO nanostructures for hydrogen generation and other potential applications. [ABSTRACT FROM AUTHOR]

Water splitting to form hydrogen and oxygen over a heterogeneous photocatalyst using solar energy is a promising process for clean and renewable hydrogen production. In recent years, numerous attempts have been made for the development of photocatalysts that work under visible light irradiation to efficiently utilize solar energy. This article reviews recent research progress in the development of visible light-driven photocatalysts, focusing on the refinement of oxynitride materials. They harvest visible photons (~450–700 nm) and work as stable photocatalysts for water reduction and oxidation under visible light. Oxynitrides with d0 electronic configuration can be successfully applied to a two-step water-splitting system, which can harvest a wide range of visible photons (~660 nm), in the presence of an iodate/iodide shuttle redox mediator. Also d10-type oxynitrides of GaN–ZnO and ZnGeN2–ZnO solid solutions can achieve functionality as photocatalysts for overall water-splitting under visible light without noticeable degradation. [ABSTRACT FROM AUTHOR]

Abstract: Photochemical production of formaldehyde (HCHO) was measured in rainwater from 13 precipitation events in Wilmington, North Carolina, USA under conditions of simulated sunlight. HCHO concentrations increased in all samples irradiated with no changes observed in dark controls. HCHO photoproduction rates were strongly correlated with dissolved organic carbon (DOC) suggesting HCHO was derived from direct or indirect photolysis of rainwater DOC. The higher photoproduction rates (0.03–2.9μMh−1) relative to those reported for surface waters suggests that rainwater DOC is more photolabile in terms of HCHO production than surface waters. HCHO photoproduction rates were higher in growing season (1.0±1.0μMh−1) compared to non-growing season (0.08±0.05μMh−1) even when rates were normalized for DOC (6.8±3.6μMh−1 mM C−1 versus 1.8±1.0μMh−1 mM C−1). The higher growing season rate may be related to seasonal differences in the composition of DOC as evidenced by differences in fluorescence per unit carbon of rainwater samples. Irradiation of C18 extracts of rainwater also produced HCHO, but at lower rates compared to corresponding whole rain samples, suggesting that hydrophyllic components of rainwater play a role in HCHO photoproduction. Our results indicate that photolysis of rainwater DOC produces significant amounts of HCHO, and possibly other low molecular weight organic compounds, likely increasing its reactivity and bioavailability. [ABSTRACT FROM AUTHOR]

The poly(vinyl chloride) based nanocomposites with 3.0% weight content of the photo-active zinc oxide (ZnO) nanoparticles or the photo-inert calcium carbonate (CaCO3) nanoparticles was prepared by the solution mixing method, respectively. Their photo-oxidative degradation under ultraviolet irradiation (365 nm) at room temperature were compared with the pure poly(vinyl chloride) via Fourier transform infrared spectroscopy, Thermogravimetric analysis and x-ray photoelectron spectroscopy analyses. The results showed that the photo-inert calcium carbonate (CaCO3) nanoparticles hampered the photo-degradation of poly(vinyl chloride), whereas the photoactive zinc oxide (ZnO) nanoparticles accelerated the photodegradation of poly(vinyl chloride). Furthermore, the ZnO nanoparticles also favored the crosslinking reaction of the dehydrochlorinated poly(vinyl chloride). [ABSTRACT FROM AUTHOR]

The η2-alkene coordinated α,β-unsaturated ketone complex Os(CH=C(PPh3)C(O)-η2-CH=CH2)Cl2(PPh3)2 (3) is very stable even at elevated temperature due to the strong steric hindrance effect of PPh3 ligands. However, compound 3 in a chloroform solution can be almost quantitatively converted into the corresponding osmafuran [OsCl(CO)(PPh3)2(CHC(PPh3)C(CH3)O)]Cl (6) via hydrolysis of the η2-coordinated olefin under photochemical conditions. Osmafuran 6 has been characterized by single crystal X-ray diffraction analysis, NMR spectroscopy and elemental analysis data. The UV-induced reaction provides a new highly efficient method for preparation of osmafurans by hydrolysis of η2-α,β-unsaturated ketone complexes. [Copyright &y& Elsevier]

Abstract: A facile photochemical method was used to synthesize Ag nanoparticle (Ag NP) embedded-ZnO nanorods in this article. The as-synthesized Ag NP embedded-ZnO nanorod samples were characterized systematically by TEM, XPS, DSC, XRD and SEM. The characterization results confirmed that Ag NPs had been embedded in ZnO nanorods. The gas-sensing properties of Ag NP embedded-ZnO nanorods were also investigated. While the performances of the sensors can be enhanced by embedding Ag NPs onto the surfaces of ZnO nanorods, the response of Ag NP embedded-ZnO nanorod sensors to 50ppm ethanol is almost three times as high as that of those made from pure-ZnO nanorods. The responses of the sensors have no apparent degradation after being exposed to ethanol of 30ppm for 100 days. Our Ag NP embedded-ZnO nanorod sensors have long-term stability and exhibit highly enhanced gas-sensing performances in their response and selectivity for detecting ethanol vapor. [Copyright &y& Elsevier]

Abstract: This paper demonstrates secondary aerosol generation potential of biofuel use in the energy sector from the photochemical interactions of precursor gases on a life cycle basis. The paper is divided into two parts—first, employing life cycle analysis (LCA) to evaluate the extent of the problem for a typical biofuel based electricity production system using five baseline scenarios; second, proposing adequate mitigation options to minimise the secondary aerosol generation potential on a life cycle basis. The baseline scenarios cover representative technologies for 2010 utilising energy crop (miscanthus), short rotation coppiced chips and residual/waste wood in different proportions. The proposed mitigation options include three approaches—biomass gasification prior to combustion, delaying the harvest of biomass, and increasing the geographical distance between the biomass plant and the harvest site (by importing the biofuels). Preliminary results indicate that the baseline scenarios (assuming all the biomass is sourced locally) bear significant secondary aerosol formation potential on a life cycle basis from photochemical neutralisation of acidic emissions (hydrogen chloride and sulphur dioxide) with ammonia. Our results suggest that gasification of miscanthus biomass would provide the best option by minimising the acidic emissions from the combustion plant whereas the other two options of delaying the harvest or importing biofuels from elsewhere would only lead to marginal reduction in the life cycle aerosol loadings of the systems. [Copyright &y& Elsevier]

In the present study, modulation of the shape and their localized surface plasmon resonance (LSPR) properties of silver nanoparticles (AgNPs) were realized by halide ion etching and subsequent photochemical regrowth. Silver nanotriangles were chemically etched into nanodisks, and were then transformed into nanohexagons, truncated nanotriangles, and nanotriangles with sharp corners by photochemical regrowth process. By changing the excitation wavelength applied in the photochemical regrowth process, the LSPR properties of AgNPs were tuned in the range from 490 to 800 nm. [ABSTRACT FROM AUTHOR]

Life on a global biosphere basis is substantiated in the form of organics and organisms, and defined as the intermediate forms (briefly expressed as CH2O) hovering between the reduced (CH4, methane) and (CO2, carbon dioxide) ends, different from the classical definition of life as a complex organization maintaining ordered structure and information. Both definitions consider sustenance of life meant as protection of life against chaos through an input of external energy. The CH2O-life connection is maintained as long as the supply of H and O lasts, which is in turn are provided by the splitting of the water molecule H2O. Water is split by electricity, as well-known from school-level experiments, and by solar radiation and geothermal heat on a global scale. In other words, the Sun's radiation and the Earth's heat as well as radioactivity split water to supply H and O for continued existence of life on the Earth. These photochemical, radiochemical and geothermal processes have influences on the evolution and current composition of the Earth's atmosphere, compared with those of Venus and Mars, and influences on the planetary climatology. This view of life may be applicable to the "search-for-life in space" and to sustainability assessment of astrobiological habitats. [ABSTRACT FROM AUTHOR]

Abstract: Two important fluoropolymers, polytetrafluoroethylene [PTFE—(C2F4)N] and polyvinylidene fluoride [PVDF—(C2H2F2)N], respond to 157-nm laser radiation in dramatically different ways. At fluences sufficient to produce rapid etching, the volatile emissions from PTFE are dominated by (CF2)N fragments. The velocities of the fastest (CF2)N molecules at each mass are consistent with kinetic energies on the order of an electron volt—and change little with fluence. This fluence independence suggests that the velocities are not affected by collisions after emission. To account for the high kinetic energies and the unusual, half-monomer mass distribution, we propose that these fragments are produced by photochemical scission of the polymer backbone, and that a fraction of the excitation energy is delivered to each fragment as kinetic energy. In contrast, the principle neutral species from PVDF is HF. HF is produced by the scission of C–F bonds, followed by chemical reactions with nearby hydrogen. This process is accompanied by the conjugation of backbone C–C bonds. The photochemical cleavage of C–C bonds in PTFE and C–F bonds in PVDF is consistent with the lower C–C bond energy of PTFE. [Copyright &y& Elsevier]

Abstract: The quantity of chromophoric or coloured dissolved organic matter (CDOM) released by eleven species of intertidal and sub-tidal macroalgae commonly found on UK shores was investigated. The subsequent breakdown of CDOM was also measured by exposing collected CDOM samples to light and dark conditions for over two weeks. CDOM absorption properties were compared at a fixed wavelength of 440nm and across two integrated wave - bands; UV-A (400–315nm) and UV-B (315–280nm). Absorption spectra of macroalgal CDOM samples were typically characterized by peaks and shoulders in the UV bands, features which were species specific. The spectral slope, derived using the log-linear method, proved to be very specific to the species and to the effect of light. Slope measurements ranged from 0.010 to 0.027nm−1, in the range of normal seawater values. Significantly more CDOM was produced by algae which were illuminated, providing evidence for a light driven exudation mechanism. Averaged across all species, exudation in the dark accounted for 63.7% of that in the light in the UV-B band. Interspecific differences in exudation rate encompassed an order of magnitude, with the highest absorption measurements attributable to brown algae. However, some brown algae produced considerably less CDOM (e.g. Pelvetia canaliculata), which were more comparable to the green and red species. Over an exposure time of 16 days, significant photochemical degradation of CDOM was observed using a natural summer sunlight regime, showing that natural solar radiation could be an important removal mechanism for newly produced algal CDOM. Though the most obvious effect was a decrease in absorption, photo-bleaching also caused a significant increase in the spectral slope parameter of 0.004nm−1. [Copyright &y& Elsevier]

[Display omitted] Shape memory polymer composites (SMPC) are a kind of intelligent material that can change state from temporary situation to original form under the external stimulus. Among all actuating approaches, light-driven SMPC are particularly outstanding due to their features of easy operation and tele-control at a specified location. Consequently, this review will focus on the state-of-art light-responsive shape memory polymer composites. It covers the classification based on different wavelengths of driving light and illustrates the working principle of each photosensitive shape memory material with examples. Whereafter, listing the commonly used preparing methods of polymer composites and the technology for forming intelligent structures. Finally, the current applied research is shown and envisages future research directions. [ABSTRACT FROM AUTHOR]

Herein, the two synthesis strategies are employed for rational design of 0D/2DAg-Ag 2 S–CdS heterojunctions towards photocatalytic degradation of methyl orange (MO) under simulated solar light. As the first strategy, a ternary Ag–Ag 2 S–CdS nanosheet (NS) heterojunction was fabricated via combined cation exchange and photo-reduction (CEPR) method (Ag–Ag 2 S–CdS/CEPR). The second strategy employed coprecipitation (CP) method (Ag–Ag 2 S–CdS/CP). Strikingly, SEM, TEM and HR-TEM images are manifested the first strategy is beneficial for retaining the original thickness (20.2 nm) of CdS NSs with a dominant formation of metallic Ag, whereas the second strategy increases the thickness (33.4 nm) of CdS NSs with a dominant formation of Ag 2 S. The Ag–Ag 2 S–CdS/CEPR exhibited 1.8-fold and 3.5-fold enhancement in photocatalytic activities as compared to those of Ag–Ag 2 S–CdS/CP and bare CdS NSs, respectively. This enhanced photocatalytic activity could be ascribed to fact that the first strategy produces a high-quality interface with intimate contact between the Ag–Ag 2 S–CdS heterojunctions, resulting in enhanced separation of photo-excited charge carriers, extended light absorption, and enriched active-sites. Furthermore, the degradation efficiency of Ag–Ag 2 S–CdS/CEPR was significantly reduced to ∼5% in the presence of BQ (•O 2 − scavenger), indicating that •O 2 − is the major active species that can decompose MO dye under simulated solar light. [Display omitted] • The role of synthesis strategies on photoactivity of OD/2DAg-Ag 2 S–CdS was examined. • Plasmonic interface with intimate contact suppressed charge carrier recombination. • Enhanced and efficient methyl orange degradation was obtained under solar light. • Superoxide radicals (•O 2 −) are the main active species for methyl orange degradation. • Plausible methyl orange degradation mechanism over OD/2DAg-Ag 2 S–CdS is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Long-term durability and degradation mechanism of dye-sensitized solar cells (DSC) sensitized with organic dyes was studied with a yellow indoline dye (D131). Durability of DSC using D131 depended on electrolyte composition. The degradation mechanism of D131 were studied by model reaction in the organic solvent. Major degradation product was identified as decarboxylated D131 (DC131), and it was found that degradation was promoted by iodine and/or amine in the electrolyte. Analysis of degradation product in actual degraded cells showed that DC131 was produced in the cell. DSC with optimized electrolyte exhibited good outdoor stability over several months. [Copyright &y& Elsevier]

[Display omitted] • The MO/rGO nanocomposites can be synthesized by chemically and physical routes. • The increase in electronic conductivity of MO can be enhanced by rGO framework. • The synergetic properties of MO/rGO play an important role towards photochemical and electrochemical behaviour. The inorganic metal oxides and graphene in the form of nanocomposites have excellent potential application towards various practical usages. In this review, we have discussed recent research on MO-specific transition metal oxides (TMO) (e.g., Ti, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, W) and rare earth metal oxides (REMO) (e.g., La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb) anchored on reduced graphene oxide (rGO) nanocomposites that are being developed for photochemical applications such as degradation of aqueous pollutants and electrochemical behaviour including supercapaciors, Li-ion energy storage, and sensing. Also, we have discussed some future nano MO/rGO composite materials. [ABSTRACT FROM AUTHOR]

A photo-assisted sonoelectrochemical (UV/US/EC) hybrid process using a mixed metal oxide (MMO) (e.g., Ti/Ru 0.3 Ti 0.7 O 2) electrode was evaluated with the aim of investigating the degradation and mineralization of ofloxacin (OFL) in a chloride-containing medium. Under optimized condition (30 mA/cm2, 0.05 mol/L NaCl, 10 mL/min, and natural pH), the OFL concentration decayed to 0 in 5 min and, after only 60 min of treatment, ~60% TOC was removed. The comparison of different combinations of UV, US, and EC techniques showed that the UV/US/EC and UV/EC techniques were the most advantageous, due to the production of highly reactive radicals through photolysis of electrochemically generated active chlorine species. A significant reduction in OFL was only achieved in the presence of NaCl, compared to Na 2 SO 4 as supporting electrolyte, demonstrating that DSA® electrodes have high electrocatalytic activity for chlorine evolution. Under real conditions, the percentage of OFL removal from the river water sample was 97% after 10 min of treatment. Phytotoxicity tests indicated that it is possible to reduce the toxicity of the solution using NaCl as supporting electrolyte. In addition, a mineralization pathway for OFL was proposed for the process in question. [Display omitted] • Complete OFL degradation was reached within 5 min of UV/US/EC process. • 60% of TOC was removed after 60 min of treatment. • Positive synergistic effects were obtained for the UV/US/EC and UV/EC techniques. • The hybrid UV/US/EC process showed low energy consumption (55.48 kWh/m3, $0.99/m3). • The toxicity of the solution in chloride-containing medium was drastically reduced. [ABSTRACT FROM AUTHOR]

Abstract: Formation of paramagnetic centers arising in highly disordered MoO3 films due to photoinjection of hydrogen at room and liquid helium temperatures has been investigated. At room temperature the concentration of Mo5+ paramagnetic centers very quickly comes to a steady-state value, whereas at liquid helium temperature it grows continuously with exposure during the whole illumination time. Formation of free radicals forming due to the detachment of hydrogen atoms from the hydrogen-donor molecules has been observed at liquid helium temperature. Its reaction rate decreases twice during the illumination, whereas the formation rate of the Mo5+ centers decreases more than an order of the magnitude. This difference in behavior has been attributed to the pairing of the Mo5+ centers. [Copyright &y& Elsevier]

Abstract: Several chemical markers of organic matter source and age are shown to be susceptible to light-induced alteration. To test for the photochemical lability of markers previously employed for sediments from the Louisiana coastal zone, we subjected sediments under resuspension conditions to simulated sunlight, and monitored changes in C:N and Br:OC ratios, δ 13C, Δ14C, and lignin composition. Markers of terrigenous origin (high C:N, lignin) decreased and δ 13C became enriched in sediments containing primarily terrigenous organic matter, while a marker of marine organic matter (Br:OC) decreased in samples containing significant contributions from this source. Preferential loss of 14C from all sediments indicated enhanced photochemical lability of organic matter of relatively recent origin, consistent with the changes in chemical markers. Most, but not all, experimental alterations are consistent with field distributions of these markers. Relatively small experimental changes in the markers in combination with confounding processes in the environment, however, prevent these parallel trends from providing any more than a consistency test for the importance of photochemical reactions in this region. [Copyright &y& Elsevier]

Abstract: Intercalation compound of methylviologen into layered niobate K4Nb6O17 ·3H2O was achieved by ion-exchange method. The MV2+-K4Nb6O17 composite material was characterized using SEM, AFM, XRD, IR and element analysis. The photochemical and electrochemical behaviors of the MV2+-K4Nb6O17 hybrid thin film were investigated. The photo excitation of oxygen-present MV2+-K4Nb6O17 thin film with UV light indicated the electron transfer from the niobate layer to MV2+ to form MV+ radical cation and spin-paired radical cation dimer. The cyclic voltammogram of the MV2+-K4Nb6O17 hybrid thin film exhibited a surface-restricted process of MV2+/MV+ redox reaction and reduction of MV+ to MV0, together with a comproportionation reaction of MV0 which forms dimer. [Copyright &y& Elsevier]

Abstract: Two oligothiophene based organic semiconductors with photo-cross-linkable benzophenone (BP) groups were synthesized and characterized. Solution cast and evaporated thin film transistors (TFTs) were created and field effect mobilities exceeding 10−3 cm2 V−1 s−1 were achieved. Upon film cross-linking the mobility increased nearly a factor of two suggesting some molecular reorganization. The stability and crosslinking of the semiconducting films were monitored by Fourier Transform Infrared Spectroscopy (FTIR). Preliminary work was also performed to study the potential of attaching analyte molecules to the semiconductor surface via photo-attachment to the BP groups for future sensor applications. The water contact angle of the semiconductor layer before and after the attachment of l-glutamic acid was measured. A drop of nearly 20 degrees suggests incorporation of the amino acid onto the surface of the semiconductor film after UV crosslinking. [Copyright &y& Elsevier]

Abstract: A simple, sensitive and rapid method for the determination of the pesticides ziram and zineb was described. This new method was based on the coupling of FIA methodology and direct chemiluminescent detection; this approach had not been used up to now with these pesticides. The additional use of an ‘on line’ photochemical reaction, which was performed by using a photoreactor consisting of a long piece of PTFE helically coiled around a 15W low-pressure lamp, increased by a factor >20 the chemiluminometric response of the pesticides. An additional 3-fold improvement in the analytical signal was also achieved by using quinine as sensitizer. The obtained throughputs were very high (121 and 101h−1 for ziram and zineb, respectively); this feature together with its low limit of detection (1ngmL−1) makes this method particularly well suited to routine analyses of environmental samples. On the other hand, its applicability to two members of the dithiocarbamate family of pesticides, makes it promising for the determination of the rest of the members of this family. The method was demonstrated by application to spiked water samples from different origins (ground, river and irrigation). [Copyright &y& Elsevier]

Abstract: Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)5 yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η2,η2:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η2,η2:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%). [Copyright &y& Elsevier]

Abstract: Hydrogen peroxide (H2O2) is a valuable chemical commodity whose production relies on expensive and energy intensive methods. If an efficient, sustainable, and inexpensive solar-mediated production method could be developed from the reaction between dioxygen and water then the use of H2O2 as a fuel may be possible and gain acceptance. When concentrated at greater than 10M, H2O2 possesses a high specific energy, is environmentally clean, and is easily stored. However, the current method of manufacturing H2O2 via the anthraquinone process is environmentally unfriendly making the unexplored nature of its photochemical production at high concentration from solar irradiation of interest. Towards this end, we studied the concentration and quantum yield of hydrogen peroxide produced in an ultraviolet (UV-B) irradiated environment using solid, Zn(II)-centered, complexes of amino-substituted isomers of indazole, pyridine, and phenylenediamine to catalyze the reaction. Aqueous suspensions in contact with air were exposed to 280–360-nm light from a low-power lamp. Of the ten complexes studied, Zn-5-aminoindazole had the greatest first-day production of 63mM/day with a 37% quantum yield and p-phenylenediamine (PPAM) showed the greatest long-term stability. Isomeric forms of the catalysts’ organic components (e.g., amino groups) affected H2O2 production. For example, irradiation of diaminopyridine isomers indicated 2,3-diamino and 3,4-diamino structures were the most productive, each generating 32mM/day H2O2, whereas the 2,5-diamino isomer generated no H2O2. A significant decrease in H2O2 production with time was observed for all but PPAM, suggesting the possibility of a catalyst-poisoning mechanism. We propose a reaction mechanism for H2O2 production based on the stability of the resonance structures of the different isomers. [Copyright &y& Elsevier]

The influence of water vapor on photochemical ozone generation has been investigated. Tests of a coaxial ozone generator driven by an efficient, tubular, 172 nm xenon excimer lamp revealed that ozone saturation concentration strongly depends on moisture concentration in the process gas. In order to adequately model the data, catalytic ozone destruction by OH and HO2 radicals formed by reactions with trace amounts of water vapor in the process gas had to be included in the photochemical ozone production rate equation system. Based on the model, optimized ozone photoreactor designs for ambient air, dry air and dry oxygen are described. [ABSTRACT FROM AUTHOR]

Several novel, diarylamine-substituted 1,8-naphthalimide derivatives were synthesized and characterized by FT-IR, 1H, 13C NMR, mass spectra and elemental analyses. The asymmetry inherent in the compounds prevented them from crystallizing and high thermal stability compounds were formed, with glass transition temperatures up to 105°C. The UV–vis absorption and photoluminescent (PL) spectra of the compounds in n-hexane, tetrahydrofuran (THF) and CH2Cl2 were investigated. The lowest absorption band of the naphthalimide derivatives centered at ≈450nm was assigned to charge-transfer transition with an emission at 494–506nm in nonpolar solvents such as n-hexane and at 578–624nm in polar solvents such as THF and CH2Cl2. [Copyright &y& Elsevier]

Abstract: Colloidal gold was prepared by UV light irradiation of the mixture of HAuCl4 aqueous solution and poly(vinyl pyrrolidone) (PVP) ethanol solution in the presence of silver ions. The resulting sheet-like nanoparticles were found to self-assemble into nanoflowers by a centrifuging process. The results of control experiments reflected that only suitable size sheet-like nanoparticles could assemble into the flower-like structures. The presence of Ag ions and PVP are essential for the formation process of nanoflowers. They perform their function by serving as structure-directing agents to produce the sheet-like particles. The appearance of the flower-like assemblages is attributed to the combination of Van der Waals force and the anisotropic hydrophobic attraction between the nanoparticles. The flower-like assemblages films can be used as surface-enhanced Raman spectroscopy (SERS) substrates with 4-aminothiophenol (4-ATP) molecule as a test probe. [Copyright &y& Elsevier]

Simultaneous observations of surface ozone (O3) with its precursors namely, carbon monoxide (CO) and oxides of nitrogen (NOx) have been taken on diurnal scale from a tropical semi-urban site, Pune (18.54°N, 73.81°E) in India. We present the data for one year (2003–2004) period to study the salient features of these trace gases. The peak in amplitude of ozone is found during the noontime whereas in CO and NOX it is observed in the morning hours between 0800 and 0900 H. The concentration of these pollutants drop down considerably during southwest monsoon months and the diurnal pattern also become very weak. The diurnal trends of these gases are found to be different for different seasons, which are specific to the receptor site. Model simulations using 3-D chemical-transport model with regional emission inventories and observed winds have also been carried out. The comparison of model results with observations, on seasonal basis yielded a reasonable qualitative agreement. The relative role of local emissions and long range transport in the diurnal pattern for different seasons has been outlined, which reveals that the ozone is highly influenced by regional/long range transport in this region. The effect of precursor amounts in the morning on afternoon ozone peak levels has been investigated using the lag correlation study, which reveals that a time lag of 5–7 h is required for most of these precursor gases to photo-chemically produce ozone to its maximum potential. Results are discussed in the light of available topographic and meteorological conditions. [ABSTRACT FROM AUTHOR]

The generation of larger rings from intermediate cyclobutanes via a two-step [2+2] photocycloaddition – ring expansion, known as the de Mayo reaction, has been widely applied in synthesis. Herein a one-step synthesis of cyclopentanoids has been developed based on the photochemical irradiation of an enone in the presence of an allylsilane. The ability of the silyl moiety to stabilize the intermediate biradical is believed to be responsible for this unique transformation where one normally expects to see the [2+2] cyclobutane adduct. [ABSTRACT FROM AUTHOR]

Air samples were collected covering a full diurnal cycle during each month of the year 2002 at a mountaintop of Mt. Abu (24.6^∘ N, 72.7^∘ E, 1680 amsl). These samples were analyzed for C2−C4 NMHCs using a gas chromatograph (GC) equipped with flame ionization detector (FID). The seasonally averaged diurnal distributions of these NMHCs do not show significant variations in the summer season. While sharp peaks in the diurnal variation of some species during evening hours are additional features apart from higher levels in all NMHCs in the winter season. The seasonal variations in relatively long lived species (e.g. ethane, propane and acetylene) are observed to be more pronounced compared to those in reactive species (e.g. ethene, propene and butanes). The seasonal changes in transport patterns seem to be more dominant factor at this site for the observed variations in NMHCs than changes in OH radical concentration. The annual mean mixing ratios of ethane, ethene, propane, propene, i-butane, acetylene, and n-butane are 1.22 ± 0.58, 0.34 ± 0.24, 0.46 ± 0.20, 0.17 ± 0.14, 0.21 ± 0.18, 0.41 ± 0.43, and 0.31 ± 0.35 ppbv, respectively. Only few pairs of NMHCs are observed to show good correlations, mainly due to transport of air masses with different degree of photochemical processing. A comparison of this measurement with data reported for other remote sites of the globe indicates lower levels of light NMHCs in the tropical sites. The annual mean mixing ratios of various C2−C4 NMHCs at Mt. Abu are lower by factors ranging between 3 to 9 compared to a nearest urban site of Ahmedabad. The annual mean propylene (propene) equivalent concentrations of about 1.12 and 8.62 ppbC were calculated for Mt. Abu and Ahmedabad, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A series of reactions have been used to introduce oxygen substituents into (η-arene)(η-cyclopentadienyl) iron (II) complexes. Photochemical ligand exchange led to the formation of the first recorded trioxygenated complex as well as mono- and di-oxygenated species. Using microwave techniques, reaction times for SNAr displacement reactions of halobenzene complexes by phenols were reduced from several hours to a few minutes. Phenols protected by either t-butylation or trimethylsilylation were found to give modest yields of the corresponding phenol complexes, using conventional thermal ligand exchange reactions. Without such protection, yields were extremely low. The above method led to the synthesis of the first example of a dihydroxybenzene complex. Some miscellaneous syntheses are also reported. The Nef reaction has been adapted to convert (η6-α-nitroalkylarene)(η5-Cp) iron (II) salts to corresponding aldehyde and ketone complexes. The α-nitroalkyl arene complexes were synthesised in good yields from (η6-halobenzene)(η5-Cp) iron (II) complexes using NaOtBu in DMSO. H/D exchange reactions with 2[H]6-DMSO in the presence of K2CO3 showed partial D incorporation in the methyl group for the unreacted α-nitroethylbenzene complex and complete exchange for the carbanion generated by deprotonation. Conversion of the α-nitroalkylarene complexes to the corresponding aldehyde and ketone complexes was accomplished in moderate yields using three methods: [(A)] H2O2 and NaOtBu in DMSO followed by reaction with CF3CO2H. [(B)] SnCl2/aq. HCl. [(C)] K2CO3 in DMF using microwave-mediated reactions. In addition, two one-pot syntheses are reported using methods B and C. [Copyright &y& Elsevier]

Reactions of photochemically or radiolytically generated radicals with tetrakis(x-aminophenyl)porphyrin, tapp2−, initiate the polymerization of the porphyrin complexes Mtapp, where M=Ni or Zn. In the photochemical process, the porphyrin-centered excited state of Mtapp reacts with the ground state to generate oxidized and reduced radical species. The cationic radical, M(tapp·+), appears to be the initiator of the porphyrin polymerization. An electron transfer reaction between the excited state of Mtapp and a Co(III) complex generates also the cation radical and initiates the polymerization process. Pulse radiolytically generated Cl2- and OH· radicals were also able to initiate the polymerization of the porphyrin complexes. [Copyright &y& Elsevier]

Abstract: A simple and efficient photochemical process for in-situ fabrication of oligothiophene and polythiophene thin films and patterns is demonstrated. The process involves vapor deposition of monomeric precursor molecules, 2,5-diiodothiophene on a substrate followed by photodissociation of the C–I bond to produce monomer radicals that further react in the condensed phase to produce oligothiophene and polythiophene. The thienyl molecular structure of the precursor is preserved during the photochemical process, providing good π conjugation of the produced polymer. Alkyl and cross-linking defects are negligible in the produced film. The direct conversion of the adsorbed monomer to the conjugated polymer allows easy fabrication of thin films and micro-patterns of polythiophene. [Copyright &y& Elsevier]