Effect of ultrasound on the structural characteristics and oxidative stability of walnut oil oleogel coated with soy protein isolate-phosphatidylserine

In this study, the three-dimensional network system formed by rice bran wax (RBW) was used as the internal structure, and the external structure formed by soybean protein isolate (SPI) and phosphatidylserine (PS) was added on the basis of the internal structure to prepare walnut oil oleogel (SPI-PS-WOG). Ultrasonic treatment was applied to the mixed solution to make SPI-PS-WOG, on the basis, the effects of ultrasonic treatment on SPI-PS-WOG were investigated. The results showed that both β and β' crystalline forms were present in all SPI-PS-WOG samples. When the ultrasonic power was 450 W, the first weight loss peak in the thermogravimetric (TGA) curve appeared at 326 °C, which was shifted to the right compared to the peak that occurred when the ultrasonic power was 0 W, indicating that the thermal stability of the SPI-PS-WOG was improved by the ultrasonic treatment. Moreover, when the ultrasonic power was 450 W, the oil holding capacity (OHC) reached 95.3 %, which was the best compared with other groups. Both confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) showed that the ultrasonic treatment of appropriate power succeeded in making the SPI-PS-WOG samples more evenly dispersed in the internal structure and denser in the external structure. In terms of oxidative stability, it was found that the peroxide value of SPI-PS-WOG remained at 9.8 mmol/kg oil for 50 days under 450 W ultrasonic power treatment, which was significantly improved compared with liquid walnut oil (WO). These results provide a new idea for the preparation of oleogels, and also lay a theoretical foundation for the application of ultrasonic treatment in oleogels.

The composition difference of macrophyte litter-derived dissolved organic matter by photodegradation and biodegradation: Role of reactive oxygen species on refractory component

The overgrowth of macrophytes has become serious due to increasing eutrophication in shallow lakes. The primary degradation processes of macrophytes litter, including photodegradation and biodegradation, induce considerable patchiness in the concentration and bioavailability of dissolved organic matter (DOM). In this study we investigated the composition evolution of DOM derived from emergent aquatic plant litter, Phragmites australis, in microbial degradation, photodegradation, and the combination of bio- and photo-degradation. Results revealed that the effects of photo- and biodegradation on the composition difference of macrophyte litter-derived DOM during short- and long-term degradation phase were different. Although large changes in DOM were observed after five days of incubation, the abundance and chemical composition were similar in the three treatments. However, more concentration of DOM was produced by combined photo- and biodegradation at the long-term degradation phase, and the composition of DOM showed less lignin-like formulae, as well as less condensed aromatic and aromatic compounds when compared to sole treatments. More reactive oxygen species (ROS) were found under the combined treatments, thus the contents of refractory components (condensed aromatic- and aromatic compound groups) were reduced. This study provide deeper insight into the fate of DOM and relevant biogeochemical processes in eutrophic lakes.

Rapid photodegradation of terrestrial soil dissolved organic matter (DOM) with abundant humic-like substances under simulated ultraviolet radiation

Solar ultraviolet (UV) radiation exhibits a significant degradation for dissolved organic matter (DOM) in natural water ecosystems. However, research on photodegradation process of terrestrial components (e.g., humic-like substances) of DOM are limited due to drastic water dilution and rapid degradation. Here, photochemical degradation of terrestrial soil DOM with abundant humic-like substances from different land use were investigated by utilizing spectral technologies. Simulated UV radiation caused obvious losses on concentration, component structures, and fluorescence characteristic of soil DOM samples. The correlations between absorption specific parameters (a₂₈₀, SUVA₂₅₄, and S_R) and dissolved organic carbon (DOC) were especially pronounced (p < 0.05), which could be used as valid indicators to determine changes in DOM composition and molecular size during photobleaching process. The decreases of DOM fluorescence intensity were corresponded to first-order kinetic and half-life reactions. The greatest reduction on fluorescence intensity (31.56-81.97%) belonged to peak C (i.e., humic-like substances). Overall, DOM from forest and grass soil ecosystems was more easily photochemical degraded than anthropogenic soil DOM. Enhancive contribution of fresh DOM formed by photodegradation increased autochthonous characteristic and bioavailable nutrition by increasing biological index (BIX) values and ammonia nitrogen (NH₄⁺-N) concentration. The slight microbial decomposition effects on DOM happened in unsterilized dark condition. Our findings provided insights for understanding the rapid photodegradation processes of composition and structure of terrestrial DOM. Graphical abstract.

Novel cadmium oxide-graphene nanocomposite grown on mesoporous silica for simultaneous photocatalytic H2-evolution

Novel Cadmium Oxide-Graphene Nanocomposite Grown on Mesoporous Silica have been successfully prepared using a self-assembly method under the catering of cetyltrimethylammonium bromide (CTAB) as the surfactant template at ambient conditions. The structural and optical properties of the obtained nanocomposites were investigated by many different techniques. The results of photocatalytic measurements revealed that almost 100% of MB organic dye was removed with the presence of SiO₂/CdO-graphene composite under visible light irradiation. Moreover, the initial pH also plays an important role in the photodegradation processes. On the other hand, this work opens a way to enhance the photocatalytic activity of gallic acid at ambient conditions without any further different oxidation processes. From the evolutionary aspect, SiO₂/CdO-graphene composite revealed better H₂ generation than that of binary photocatalyst (CdO-graphene nanocomposite). The results of characterization and photodegradation suggest that SiO₂/CdO-graphene material constitutes a new photocatalyst for the degradation of organic contaminants, as well as the development of an efficient hetero-system for hydrogen production.

Visible light-activated degradation of natural organic matter (NOM) using zinc-bismuth oxides-graphitic carbon nitride (ZBO-CN) photocatalyst: Mechanistic insights from EEM-PARAFAC

In this study, the complex degradation behavior of natural organic matter (NOM) was explored using photocatalytic oxidation systems with a novel catalyst based on a hybrid composite of zinc-bismuth oxides and g-C₃N₄ (ZBO-CN). The photooxidation system demonstrated the effective removal of NOM under low-intensity visible light irradiation, presenting removal rates of 53-74% and 65-88% on the basis of dissolved organic carbon (DOC) and the UV absorption coefficient (UV₂₅₄), respectively, at 1.5 g/L of the catalyst. The NOM removal showed an increasing trend with a higher ZBO-CN dose. Comparative experiments with the hole and OH radical scavengers revealed that the direct oxidation occurring on the catalyst's surface might be the governing photocatalytic mechanism. Fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) revealed the individual removal behavior of the different constituents in bulk NOM. Different tendencies towards preferential adsorption and subsequent oxidative removal were found among dissimilar fluorescent components within a bulk terrestrial NOM, following the order of terrestrial humic-like (C1) > humic-like (C2) > microbial humic-like (C3) components. The result suggests the dominant operation of π-π and/or hydrophobic interactions between the NOM and the catalyst. The discriminative removal behavior was more pronounced in visible light versus UV-activated systems, probably due to the incapability of visible light to excite è - h⁺ pairs of ZnO and the triplet state of NOM. The high photoactivity and structural stability of ZBO-CN under visible light implies its potential for an effective, low-cost and energy-saving treatment technology to selectively remove large sized humic-like substances from water.

Photocatalytic degradation of organic pollutants in wastewater with g-C3N4/sulfite system under visible light irradiation

To develop low cost and high efficient sulfate radical (SO₄^-) based advanced oxidation processes (AOPs) for rapid remediation of contaminated waters is of great interest. In this study, a green and novel SO₄^- based AOPs, in situ visible light activation of sulfite by graphitic carbon nitride (g-C₃N₄), for the degradation of organic pollutants is reported. The g-C₃N₄+HSO₃^- + Vis system could achieve remarkably enhanced degradation of organic pollutants such as organic dyes and phenol in aqueous solution. The excellent reusability of the metal free catalyst was also observed during ten successive cycles. The efficiency of the system was dependent on the reaction conditions, which first increased and then decreased with the increase of HSO₃^- concentration and initial solution pH. The addition of HCO₃^- stimulated the pollutant degradation, but other water matrix components such as Cl^- and humic acid showed nearly no influence on the reaction. The mechanism investigations suggested that sulfite is oxidized in the system to sulfite radicals, which then react with dioxygen and superoxide radicals to form SO₅^- radicals and HSO₅^- respectively. SO₅^- radicals can be also reduced by sulfite or photoelectron to HSO₅^-. SO₄^- radicals were then produced from HSO₅^- reduction by photoelectron, and contributed to dye degradation in the system together with superoxide radicals. This study provides a novel new approach for efficient degradation of organic degradation via sulfite activation.

Petroleomic analysis of the treatment of naphthenic organics in oil sands process-affected water with buoyant photocatalysts

The persistence of toxicity associated with the soluble naphthenic organic compounds (NOCs) of oil sands process-affected water (OSPW) implies that a treatment solution may be necessary to enable safe return of this water to the environment. Due to recent advances in high-resolution mass spectrometry (HRMS), the majority of the toxicity of OSPW is currently understood to derive from a subset of toxic classes, comprising only a minority of the total NOCs. Herein, oxidative treatment of OSPW with buoyant photocatalysts was evaluated under a petroleomics paradigm: chemical changes across acid-, base- and neutral-extractable organic fractions were tracked throughout the treatment with both positive and negative ion mode electrospray ionization (ESI) Orbitrap MS. Elimination of detected OS⁺ and NO⁺ classes of concern in the earliest stages of the treatment, along with preferential degradation of high carbon-numbered O₂^- acids, suggest that photocatalysis may detoxify OSPW with higher efficiency than previously thought. Application of petroleomic level analysis offers unprecedented insights into the treatment of petroleum impacted water, allowing reaction trends to be followed across multiple fractions and thousands of compounds simultaneously.

Trade-offs in ecosystem impacts from nanomaterial versus organic chemical ultraviolet filters in sunscreens

Both nanoparticulate (nZnO and nTiO₂) and organic chemical ultraviolet (UV) filters are active ingredients in sunscreen and protect against skin cancer, but limited research exists on the environmental effects of sunscreen release into aquatic systems. To examine the trade-offs of incorporating nanoparticles (NPs) into sunscreens over the past two decades, we targeted endpoints sensitive to the potential risks of different UV filters: solar reactive oxygen production in water and disruption of zebrafish embryo development. First, we developed methodology to extract nanoparticles from sunscreens with organic solvents. Zebrafish embryos exposed to parts-per-million NPs used in sunscreens displayed limited toxicological effects; nZnO particles appeared to be slightly more toxic than nTiO₂ at the highest concentrations. In contrast, seven organic UV filters did not affect zebrafish embryogenesis at or near aqueous solubility. Second, to simulate potent photo-initiated reactions upon release into water, we examined methylene blue (MB) degradation under UV light. nTiO₂ from sunscreen caused 10 times faster MB loss than nZnO and approached the photocatalytic degradation rate of a commercial nTiO₂ photocatalysts (P25). Organic UV filters did not cause measurable MB degradation. Finally, we estimated that between 1 and 10 ppm of sunscreen NPs in surface waters could produce similar steady state hydroxyl radical concentrations as naturally occurring fluvic acids under sunlight irradiation. Incorporation of NPs into sunscreen may increase environmental concentrations of reactive oxygen, albeit to a limited extent, which can influence transformation of dissolved substances and potentially affect ecosystem processes.

Bimetallic Au-Pd nanoparticles on 2D supported graphitic carbon nitride and reduced graphene oxide sheets: A comparative photocatalytic degradation study of organic pollutants in water

Novel and sustainable bimetallic nanoparticles of Au-Pd on 2D graphitic carbon nitride (g-C₃N₄) and reduced graphene oxide (rGO) sheets was designed adopting an eco-friendly chemical route to obtain Au-Pd/g-C₃N₄ and Au-Pd/rGO, respectively. Elimination of hazardous pollutants, particularly phenol from water is urgent for environment remediation due to its significant carcinogenicity. Considering this aspect, the Au-Pd/g-C₃N₄ and Au-Pd/rGO nanocomposites are used as photocatalyst towards degradation of toxic phenol, 2-chlorophenol (2-CP) and 2-nitrophenol (2-NP) under natural sunlight and UV light irradiation. Au-Pd/g-C₃N₄ nanocomposite exhibited higher activity then Au/g-C₃N₄, Pd/g-C₃N₄ and Au-Pd/rGO nanocomposites with more than 95% degradation in 180 min under sunlight. The obtained degradation efficiency of our materials is better than many other reported photocatalysts. Incorporation of nitrogen atoms in the carbon skeleton of g-C₃N₄ provides much better properties to Au-Pd/g-C₃N₄ nanocomposite than carbon based Au-Pd/rGO leading to its higher degradation efficiency. Due to the presence of these nitrogen atoms and some defects, g-C₃N₄ possesses appealing electrical, chemical and functional properties. Photoluminescence results further revealed the efficient charge separation and delayed recombination of photo-induced electron-hole pairs in the Au-Pd/g-C₃N₄ nanocomposite. Generation of reactive oxygen species during photocatalysis is well explained through photoluminescence study and the sustainability of these photocatalyst was ascertained through reusability study up to eight and five consecutive cycles for Au-Pd/g-C₃N₄ and Au-Pd/rGO nanocomposites, respectively without substantial loss in its activity. Characterization of the photocatalysts after reaction signified the stability of the nanocomposites and added advantage to our developed photocatalytic system.

Facile Photoinduced Generation of Hydroxyl Radical on a Nitrocellulose Membrane Surface and its Application in the Degradation of Organic Pollutants

A simple, clean, and efficient method has been developed for generating hydroxyl radicals on a nitrocellulose membrane (NCM) under light of wavelengths greater than 280 nm. Hydroxyl radicals formed on the NCM surface, diffusing into the bulk solution under irradiation. Radical generation was shown to be dependent on the nature of the NCM and light, and independent of the properties of the bulk solution. The quantum yield for hydroxyl radicals from the NCM was 1.72×10^-4 , which is approximately 2.46 times that from TiO₂ . This hydroxyl radical generation method was preliminarily applied in the photodegradation of organic pollutants, in which electrostatic interactions between the pollutant molecules and the NCM surface were found to play a key role. Further applications of this hydroxyl radical generation method should be assessed.

A review of quantitative structure-property relationships for the fate of ionizable organic chemicals in water matrices and identification of knowledge gaps

Many organic chemicals are ionizable by nature. After use and release into the environment, various fate processes determine their concentrations, and hence exposure to aquatic organisms. In the absence of suitable data, such fate processes can be estimated using Quantitative Structure-Property Relationships (QSPRs). In this review we compiled available QSPRs from the open literature and assessed their applicability towards ionizable organic chemicals. Using quantitative and qualitative criteria we selected the 'best' QSPRs for sorption, (a)biotic degradation, and bioconcentration. The results indicate that many suitable QSPRs exist, but some critical knowledge gaps remain. Specifically, future focus should be directed towards the development of QSPR models for biodegradation in wastewater and sediment systems, direct photolysis and reaction with singlet oxygen, as well as additional reactive intermediates. Adequate QSPRs for bioconcentration in fish exist, but more accurate assessments can be achieved using pharmacologically based toxicokinetic (PBTK) models. No adequate QSPRs exist for bioconcentration in non-fish species. Due to the high variability of chemical and biological species as well as environmental conditions in QSPR datasets, accurate predictions for specific systems and inter-dataset conversions are problematic, for which standardization is needed. For all QSPR endpoints, additional data requirements involve supplementing the current chemical space covered and accurately characterizing the test systems used.

Complete and Partial Photo-oxidation of Dissolved Organic Matter Draining Permafrost Soils

Photochemical degradation of dissolved organic matter (DOM) to carbon dioxide (CO2) and partially oxidized compounds is an important component of the carbon cycle in the Arctic. Thawing permafrost soils will change the chemical composition of DOM exported to arctic surface waters, but the molecular controls on DOM photodegradation remain poorly understood, making it difficult to predict how inputs of thawing permafrost DOM may alter its photodegradation. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer of arctic soils to complete and partial photo-oxidation and investigated changes in the chemical composition of each DOM source following sunlight exposure. Permafrost and organic mat DOM had similar lability to photomineralization despite substantial differences in initial chemical composition. Concurrent losses of carboxyl moieties and shifts in chemical composition during photodegradation indicated that photodecarboxylation could account for 40-90% of DOM photomineralized to CO2. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic moieties with antioxidant properties. These results suggest that photodegradation will likely continue to be an important control on DOM fate in arctic freshwaters as the climate warms and permafrost soils thaw.

Insight into photocatalytic degradation of dissolved organic matter in UVA/TiO₂ systems revealed by fluorescence EEM-PARAFAC

Photocatalytic degradation of dissolved organic matter (DOM) using TiO2 as a catalyst and UVA as a light source was examined under various experimental settings with different TiO2 doses, solution pH, and the light intensities. The changes in UV absorbance and fluorescence with the irradiation time followed a pseudo-first order model much better than those of dissolved organic carbon. In general, the degradation rates were increased by higher TiO2 doses and light intensities. However, the exact photocatalytic responses of DOM to the irradiation were affected by many other factors such as aggregation of TiO2, light scattering, hydroxyl radicals produced, and DOM sorption on TiO2. Fluorescence excitation-emission matrix (EEM) coupled with parallel factor analysis (PARAFAC) revealed that the DOM changes in fluorescence could be described by the combinations of four dissimilar components including one protein-like, two humic-like, and one terrestrial humic-like components, each of which followed well the pseudo-first order model. The photocatalytic degradation rates were higher for protein-like versus humic-like component, whereas the opposite order was displayed for the degradation rates in the absence of TiO2, suggesting different dominant mechanisms operating between the systems with and without TiO2. Our results based on EEM-PARAFAC provided new insights into the underlying mechanisms associated with the photocatalytic degradation of DOM as well as the potential environmental impact of the treated water. This study demonstrated a successful application of EEM-PARAFAC for photocatalytic systems via directly comparing the kinetic rates of the individual DOM components with different compositions.

An overview on limitations of TiO2-based particles for photocatalytic degradation of organic pollutants and the corresponding countermeasures

The pollutants classified as "persistent organic pollutants (POPs)", are being subject to high concern among the scientific community due to their persistence in the environment. TiO2-based photocatalytic process has shown a great potential as a low-cost, environmentally friendly and sustainable treatment technology to remove POPs in sewage to overcome the shortcomings of the conventional technologies. However, this technology suffers from some main technical barriers that impede its commercialization, i.e., the inefficient exploitation of visible light, low adsorption capacity for hydrophobic contaminants, uniform distribution in aqueous suspension and post-recovery of the TiO2 particles after water treatment. To improve the photocatalytic efficiency of TiO2, many studies have been carried out with the aim of eliminating the limitations mentioned above. This review summarizes the recently developed countermeasures for improving the performance of TiO2-based photocatalytic degradation of organic pollutants with respect to the visible-light photocatalytic activity, adsorption capacity, stability and separability. The performance of various TiO2-based photocatalytic processes for POPs degradation and the underlying mechanisms were summarized and discussed. The future research needs for TiO2-based technology are suggested accordingly. This review will significantly improve our understanding of the process of photocatalytic degradation of POPs by TiO2-based particles and provide useful information to scientists and engineers who work in this field.

Time Resolved Spectroscopic Studies on a Novel Synthesized Photo-Switchable Organic Dyad and Its Nanocomposite Form in Order to Develop Light Energy Conversion Devices

UV-vis absorption, steady state and time resolved spectroscopic investigations in pico and nanosecond time domain were made in the different environments on a novel synthesized dyad, 3-(2-methoxynaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-en-1-one (MNTMA) in its pristine form and when combined with gold (Au) nanoparticles i.e., in its nanocomposite structure. Both steady state and time resolved measurements coupled with the DFT calculations performed by using Gaussian 03 suit of software operated in the linux operating system show that though the dyad exhibits mainly the folded conformation in the ground state but on photoexcitation the nanocomposite form of dyad prefers to be in elongated structure in the excited state indicating its photoswitchable nature. Due to the predominancy of elongated isomeric form of the dyad in the excited state in presence of Au Nps, it appears that the dyad MNTMA may behave as a good light energy converter specially in its nanocomposite form. As larger charge separation rate (kcs ~ 4 x 10(8) s-1) is found relative to the rate associated with the energy wasting charge recombination processes (kcR ~ 3 x 10(5) s-1) in the nanocomposite form of the dyad, it demonstrates the suitability of constructing the efficient light energy conversion devices with Au-dyad hybrid nanomaterials.

The effect of operational parameters on the photocatalytic degradation of Congo red organic dye using ZnO-CdS core-shell nano-structure coated on glass by Doctor Blade method

Photocatalytic degradation of Congo red was investigated using ZnO-CdS core-shell nano-structure coated on glass by Doctor Blade method in aqueous solution under irradiation. Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were used for the morphological and structural characterization of ZnO-CdS core-shell nanostructures. XRD results showed diffractions of wurtzite zinc oxide core and wurtzite cadmium sulfide shell. FESEM results showed that nanoparticles are nearly hexagonal with an average diameter of about 50 nm. The effect of catalyst loading, UV-light irradiation time and solution pH on photocatalytic degradation of Congo red was studied and optimized values were obtained. Results showed that the employment of efficient photocatalyst and selection of optimal operational parameters may lead to complete decolorization of dye solutions. It was found that ZnO-CdS core-shell nano-structure is more favorable for the degradation of Congo red compare to pure ZnO or pure CdS due to lower electron hole recombination. The results showed that the photocatalytic degradation rate of Congo red is enhanced with increasing the content of ZnO up to ZnO(0.2 M)/CdS(0.075 M) which is reached 88.0% within 100 min irradiation.

Facile synthesis of PbWO4: applications in photoluminescence and photocatalytic degradation of organic dyes under visible light

Stolzite polymorph of PbWO4 catalyst was prepared by the facile room temperature precipitation method. Structural parameters were refined by the Rietveld analysis using powder X-ray data. PbWO4 was crystallized in the scheelite-type tetragonal structure with space group I41/a (No. 88). Field emission scanning electron microscopy revealed leaf like morphology. Photoluminescence spectra exhibit broad blue emission (425 nm) under the excitation of 356 nm. The photocatalytic degradation of Methylene blue, Rhodamine B and Methyl orange dyes were measured under visible illumination. The 100% dye degradation was observed for MB and RhB dyes within 60 and 105 min. The rate constant was found to be in the decreasing order of MB>RhB>MO which followed the 1st order kinetic mechanism. Therefore, PbWO4 can be a potential candidate for blue component in white LEDs and also acts as a catalyst for the treatment of toxic and non-biodegradable organic pollutants in water.

Impact of UV/H2O2 pre-oxidation on the formation of haloacetamides and other nitrogenous disinfection byproducts during chlorination

Haloacetamides (HAcAms), an emerging class of nitrogen-based disinfection byproducts (N-DBPs) of health concern in drinking water, have been found in drinking waters at μg/L levels. However, there is a limited understanding about the formation, speciation, and control of halogenated HAcAms. Higher ultraviolet (UV) doses and UV advanced oxidation (UV/H2O2) processes (AOPs) are under consideration for the treatment of trace organic pollutants. The objective of this study was to examine the potential of pretreatment with UV irradiation, H2O2 oxidation, and a UV/H2O2 AOP for minimizing the formation of HAcAms, as well as other emerging N-DBPs, during postchlorination. We investigated changes in HAcAm formation and speciation attributed to UV, H2O2 or UV/H2O2 followed by the application of free chlorine to quench any excess hydrogen peroxide and to provide residual disinfection. The results showed that low-pressure UV irradiation alone (19.5-585 mJ/cm(2)) and H2O2 preoxidation alone (2-20 mg/L) did not significantly change total HAcAm formation during subsequent chlorination. However, H2O2 preoxidation alone resulted in diiodoacetamide formation in two iodide-containing waters and increased bromine utilization. Alternatively, UV/H2O2 preoxidation using UV (585 mJ/cm(2)) and H2O2 (10 mg/L) doses typically employed for trace contaminant removal controlled the formation of HAcAms and several other N-DBPs in drinking water.

A novel strategy to fabricate multifunctional Fe3O4@C@TiO2 yolk-shell structures as magnetically recyclable photocatalysts

Using poly(acrylic acid) (PAA) as a template, a novel Fe3O4@C@TiO2 yolk-shell structure derived from heat treatment on Fe2O3@PAA@TiO2 core-shell structures is constructed, where the interior void volume and shell thickness are readily tuned. In this method, the PAA shell between the original spherical α-Fe2O3 nanoparticle (NP) core and the outer TiO2 shell replaces the common SiO2 template leaving out the tedious treatment procedure of the template. After calcination, the α-Fe2O3 core was reduced to the Fe3O4 core providing the NPs with magnetic properties and the middle carbon coating around the magnetic core could avoid the occurrence of photodissolution. Moreover, the obtained Fe3O4@C@TiO2 yolk-shell nanocomposites (NCs) exhibit fine photocatalytic activity for the photodegradation of organic contaminants in waste water.

A role for calcium hydroxide and dolomite in water: acceleration of the reaction under ultraviolet light

Organic environmental pollutants are now being detected with remarkably high frequency in the aquatic environment. Photodegradation by ultraviolet light is sometimes used as a method for removing organic chemicals from water; however, this method is relatively inefficient because of the low degradation rates involved, and more efficient methods are under development. Here we show that the removal of various organic pollutants can be assisted by calcined dolomite in aqueous solution under irradiation with ultraviolet light. It was possible to achieve substantial removal of bisphenol A, chlorophenols, alkylphenols, 1-naphthol and 17β-estradiol. The major component of dolomite responsible for the removal was calcium hydroxide. Our results demonstrate that the use of calcium hydroxide with ultraviolet light irradiation can be a very effective method of rapidly removing organic environmental pollutants from water. This is a new role for calcium hydroxide and dolomite in water treatment.

Surface plasmonic effects on organic solar cells

Most high-performance organic photovoltaic (OPV) devices reported in the literature have been fabricated using the bulk heterojunction (BHJ) concept. Typically, the optimum thickness of the active layer for an OPV device is around 100 nm, or possibly less; such a thin layer can lead to low absorption of light. A thicker layer, however, inevitably increases the device resistance, due to the low carrier mobilities and short exciton diffusion lengths in organic materials. This situation imposes a trade-off between light absorption and charge transport efficiencies in OPV devices, motivating the development of a variety of light-trapping techniques. Metallic nanoparticles (NPs) such as Ag, Au, etc. and other metallic nanostructures are potential candidates for improving the light absorption due to the localized surface plasmon resonance (LSPR). LSPR contributes to the significant enhancement of local electromagnetic fields and improves the optical properties of the nanostructure devices. The excitation of LSPR is achieved when the frequency of the incident light matches its resonance peak, resulting in unique optical properties; selective light extinction as well as local enhancement of electromagnetic fields near the surface of metallic NPs. The resonance peak of LSPR depends strongly on the size, shape, and the dielectric environment of the metallic NPs. In this review article, progress on plasmonic enhanced OPV device performance is examined. The concepts of surface plasmonics for OPV devices, suitable plasmonic materials, location, optimum size and concentration of NP materials within the device are explored.

Fullerene derivatives as electron acceptors for organic photovoltaic cells

Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

Photodegradation of organic matter in fresh garbage leachate using immobilized nano-sized TiO2 as catalysts

Two immobilized nano-sized TiO2 catalysts, TiO2/activated carbon (TiO2/AC) and TiO2/silica gel (SG) (TiO2/SG), were prepared by the sol-gel method, and their use in the photocatalytic degradation of organic matter in fresh garbage leachate under UV irradiation was investigated. The influences of the catalyst dosage, the initial solution pH, H2O2 addition and the reuse of the catalysts were evaluated. The degradation of organic matter was assessed based on the decrease of the chemical oxygen demand (COD) in the leachate. The results indicated that the degradation of the COD obeyed first-order kinetics in the presence of both photocatalysts. The degradation rate of COD was found to increase with increasing catalyst dosage up to 9 g/L for TiO2/AC and 6 g/L for TiO2/SG, above which the degradation began to attenuate. Furthermore, the degradation rate first increased and then decreased as the solution pH increased from 2 to 14, and the degradation rate increased as the amount of H2O2 increased to 2.93 mM, after which it remained constant. No obvious decrease in the rate of COD degradation was observed during the first four repeated uses of the photocatalysts, indicating that the catalysts could be recovered and reused. Compared with TiO2/AC, TiO2/SG exhibited higher efficiency in photocatalyzing the degradation of COD in garbage leachate.

Preparation of graphene-ZrO2 nanocomposites by heat treatment and photocatalytic degradation of organic dyes

ZrO2 nanoparticles were synthesized by combining a solution containing zinconyl chloride in distilled water with a NH4OH solution under microwave irradiation. Graphene and ZrO2 nanocomposites were synthesized in an electric furnace at 700 degrees C for 2 hours. The heated graphene-ZrO2 nanocomposites were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In addition, UV-vis spectrophotometry was used to evaluate the heated graphene-ZrO2 nanocomposites as a catalyst in the photocatalytic degradation of organic dyes. The photocatalytic effect of the heated graphene-ZrO2 nanocomposites was compared with that of unheated graphene nanoparticles, heated graphene nanoparticles, and unheated graphene-ZrO2 nanocomposites in organic dyes (methylene blue, methyl orange, and rhodamine B) under ultraviolet light at 254 nm.

Gamma irradiation: a method to produce an abiotic control for biological activated carbon

The aim of this paper was to investigate the feasibility of using gamma irradiation to inhibit the microbial activity of biological powder activated carbon (PAC) without impacting its adsorptive properties. First of all, the range of dose of gamma rays required to produce abiotic PAC was selected on the basis of heterotrophic plate counts (HPC) inactivation and methylene blue (MB) adsorption kinetics. Doses inferior to 10 kGy were not sufficient to inhibit the culture of heterotrophic bacteria. On the other hand, doses superior to 15 kGy were demonstrated to affect the adsorption rate of MB. Consequently, a dose comprised between 10 and 15 kGy was selected for further investigation. In order to validate the adequacy of the range of dose (i.e. 10-15 kGy), adsorption characteristics were tested by monitoring the removal kinetics of refractory dissolved organic carbon (RDOC). No significant differences were observed between irradiated and non-irradiated biological PAC for the adsorption of RDOC. Irradiated, non-irradiated and virgin PAC were also evaluated in terms of abundance of viable (using the LIVE/DEAD BacLight method) bacteria and in terms of heterotrophic biomass activity. The results of the BacLight method demonstrated that attachment of the biofilm on the PAC was not impacted by the irradiation and heterotrophic activity measurements demonstrated that the latter could be radically reduced in the range of dose selected. In conclusion, when using a proper dose, the gamma irradiation of colonized activated carbon drastically reduced the heterotrophic activity on activated carbon without significantly impacting its adsorptive behaviour.

Designing artificial photosynthetic devices using hybrid organic-inorganic modules based on polyoxometalates

Artificial photosynthesis aims at capturing solar energy and using it to produce storable fuels. However, while there is reason to be optimistic that such approaches can deliver higher energy conversion efficiencies than natural photosynthetic systems, many serious challenges remain to be addressed. Perhaps chief among these is the issue of device stability. Almost all approaches to artificial photosynthesis employ easily oxidized organic molecules as light harvesters or in catalytic centres, frequently in solution with highly oxidizing species. The 'elephant in the room' in this regard is that oxidation of these organic moieties is likely to occur at least as rapidly as oxidation of water, meaning that current device performance is severely curtailed. Herein, we discuss one possible solution to this problem: using self-assembling organic-polyoxometalate hybrid structures to produce compartments inside which the individual component reactions of photosynthesis can occur without such a high incidence of deleterious side reactions.

Organic photovoltaic solar cells with cathode modified by ZnO

Solution processed cathode organic photovoltaic cells (OPVs) utilizing thin layer of ZnO with 27% increase in power conversion efficiency (PCE) to control devices have been demonstrated. Devices without the presence of ZnO layer have much lower PCE than the ones with ZnO layer. Cathode modification layer can be used to reduce photogenerated excitions and finally improve the performance of the OPVs. The successful demonstrations of OPVs with an introduction of ZnO cathode layer give promise of further device progresses.

Two-dimensional simulation of organic bulk heterojunction solar cell: influence of the morphology

Recent developments in organic solar cells show interesting power conversion efficiencies. However, with the use of organic semiconductors and bulk heterojunction cells, many new concepts have to be introduced to understand their characteristics. Only few models investigate these new concepts, and most of them are one-dimensional only. In this work, we present a two-dimensional model based on solving the drift-diffusion equations. The model describes the generation of excitons in the donor phase of the active layer and their diffusion towards an interface between the two separate acceptor and donor domains. Then, when the exciton reaches the interface, it forms a charge transfer state which can split into free charges due to the internal potential. Finally, these free charges are transported toward the electrodes within their respective domains (electrons in acceptor domain, holes in donor domain) before being extracted. In this model, we can follow the distribution of each species and link it to the physical processes taken into account. Using the finite element method to solve the equations of the model, we simulate the effect of the bulk heterojunction morphology on photocurrent curves. We concentrate on the morphology parameters such as the mean acceptor/donor domain sizes and the roughness of,the interface between the donor and acceptor domains. Results are discussed in relation with experimental observations.

Colour-coded photoluminescence and chemiluminescence of fluorene polymer-based organic nanowires in random and organised arrangements

Organic nanowires based on a fluorene homopolymer and a copolymer, i.e., poly(9,9-dioctylfluorene), F8, and poly(9,9-dioctylfluorene-co-benzothiadiazole), F8BT, respectively, were synthesised by solution assisted wetting of porous anodic alumina templates. Nanowires ranged between 3 microm and 50 microm in length, and were ca. 200 nm in diameter. Absorption and photoluminescence studies of F8BT nanowires yielded spectra characteristic of the parent material. By contrast, the well resolved spectra obtained for F8 nanowires indicated that, during synthesis, a fraction of the molecules within the wires underwent intra-chain re-orientation from the more random molecular conformations of the glassy phase to the more planar extended molecular conformation of the beta-phase. Importantly, both F8 and F8BT nanowires exhibited a distinct emission anisotropy, consistent with internal alignment of the emissive polymer chains along the long axes of the wires. This property was exploited by forming nanowire crossbar structures in which, by selecting either luminescence wavelength or polarisation state, spatial confinement and colour tuning of polarised light emission could be readily achieved. Finally, nanowire chemiluminescence was demonstrated. Characteristic blue and green-yellow luminescence was observed for F8 and F8BT wires, respectively, confirming that these novel nanostructures may act as nanoscale chemiluminescent light sources.

Inkjet printed solar cell active layers based on a novel, amorphous polymer

Organic solar cells are a favorable alternative to their inorganic counterparts because the functional layers of these devices can be processed with printing or coating on a large scale. In this study, a novel polymer was synthesized, blended with fullerene and deposited with inkjet printing for solar cell applications. Devices with printed layers were compared to those with spin coated films in order to evaluate inkjet printing as a thin film deposition method. Efficiency values of 3.7% were found for devices with inkjet printed or spin coated layers. Inkjet printing can be used to successfully process the active layers of organic solar cells consisting of novel polymers without sacrificing device performance.

Organic solar cells using a ZnO/Cu/ZnO anode deposited by ion beam sputtering at room temperature for flexible devices

The development of indium-free transparent conductive oxides (TCOs) on polymer substrates for flexible devices requires deposition at low temperatures and a limited thermal treatment. In this paper, we investigated the optical and electrical properties of ZnO/Cu/ZnO multi-layer electrodes obtained by ion beam sputtering at room temperature for flexible optoelectronic devices. This multilayer structure has the advantage of adjusting the layer thickness to favor antireflection and surface plasmon resonance of the metallic layer. We found that the optimal electrode is made up of a 10 nm-thick Cu layer between two 40 nm-thick ZnO layers, which results in a sheet resistance of 12 omega/(see symbol), a high transmittance of 85% in the visible range, and the highest figure of merit of 5.4 x 10(-3) (see symbol)/omega. A P3HT:PCBM-based solar cell showed a power conversion efficiency (PCE) of 2.26% using the optimized ZnO (40 nm)/Cu (10 nm)/ZnO (40 nm) anode.

Effect of structure and interlayer diffusion in organic position sensitive photodetectors based on complementary wedge donor/acceptor layers

We have developed organic photodetectors based on two complementary wedge layers made of CuPc and C60 and observed a strong spatial dependence of the spectral response on the position of the incident light spot. Photocurrent measurements are correlated with atomic force microscopy (AFM), micro-Raman and ellipsometry maps in order to provide insights into the local donor/acceptor concentration, layer thickness and nature of the donor-acceptor interface along the direction of the thickness gradient. Deviations in spatial dependence between experimental photocurrent values and those predicted with a model assuming a sharp and well defined organic-organic interface are discussed in terms of inter-diffusion layers.

Nanoimprinted organic semiconductor laser pumped by a light-emitting diode

An organic semiconductor laser, simply fabricated by UV-nanoimprint lithography (UV-NIL), that is pumped with a pulsed InGaN LED is demonstrated. Molecular weight optimization of the polymer gain medium on a nanoimprinted polymer distributed feedback resonator enables the lowest reported UV-NIL laser threshold density of 770 W cm(-2) , establishing the potential for scalable organic laser fabrication compatible with mass-produced LEDs.

Carrier transport in the V[TCNE]x (TCNE = tetracyanoethylene; x ~ 2) organic-based magnet

The carrier transport of chemical vapor deposition (CVD) prepared films of the room temperature organic-based magnet V[TCNE]x (TCNE = tetracyanoethylene; x ~ 2) over a broad temperature and magnetic field range is reported. Due to disorder the [TCNE](·-) sites are located in statistically different environments, and their energies vary from site-to-site, which leads to tailing the density of states into the energy gap, creating electronic traps and suppressing the electron mobility. Conversely, these variations have little effect on the valence band derived from the octahedral V(II)3d(t(2g)) levels, and, hence, on the hole mobility. Presuming a Gaussian distribution of the energies of the localized states in the gap, a model that adequately describes the experimental data is proposed. In this model the T(-1) temperature dependent term was added to the Arrhenius activation energy, Ea, which effectively describes its decrease on cooling. The linear increase of positive magnetoresistance with magnetic field, as well as its weak temperature dependence [ is proportional to (1-T/Tc)(-1/2)] is discussed in terms of a small contribution to Ea associated with the change of magnetic energy.

Comparison of graphene oxide with reduced graphene oxide as hole extraction layer in organic photovoltaic cells

A comparison was performed between the use of graphene oxide (GO) and reduced graphene oxide (rGO) as a hole extraction layer (HEL) in organic photovoltaic (OPV) cells with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester. Hydrazine hydrate (HYD) and the thermal method (Thermal) were adopted to change the GO to rGO. The GO HEL was deposited on an indium tin oxide electrode by spin coating, followed by the reduction process to form the rGO HELs. The success of the reduction processes was confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoemission spectroscopy, transmittance, and 2-point probe method. The OPV cell with the GO (-3 nm) HEL exhibits an increased power conversion efficiency (PCE) as high as 2.5% under 100 mW/cm2 illumination under air mass conditions, which is higher than that of the OPV cell without HEL, viz. 1.78%. However, the PCE of the OPV cell with rGO HEL is not high as the values of 1.8% for the HYD-rGO and 1.9% for the Thermal-rGO. The ultraviolet photoemission spectroscopy results showed that the work function of GO was 4.7 eV, but those of HYD-rGO and Thermal-rGO were 4.2 eV and 4.5 eV, respectively. Therefore, it is considered that GO is adequate to extract the holes from the active layer, but HYD-rGO and Thermal-rGO are not appropriate to use as HELs in OPV cells from the viewpoint of the energy alignment.

Optoelectrical and low-frequency noise characteristics of flexible ZnO-SiO2 photodetectors with organosilicon buffer layer

The present study demonstrates the optoelectrical and low-frequency noise characteristics of ZnO-SiO(2) nanocomposite solar-blind metal-semiconductor-metal photodetectors (MSM PDs) on flexible polyethersulfone (PES) substrate with and without an organosilicon [SiO(x)(CH(3))] buffer layer. For a given bandwidth of 100 Hz and a -5 V applied bias, the noise equivalent powers of the ZnO-SiO(2) nanocomposite MSM PD on PES with and without the SiO(x)(CH(3)) buffer layer were 1.39 × 10(-14) and 5.72 × 10(-14) W at 240nm, respectively, corresponding to the normalized detectivities of 5.04 × 10(14) and 1.22 × 10(14) Hz(0.5) W(-1), respectively. These findings indicate that a lower noise level and a higher detectivity can be achieved for ZnO-SiO(2) nanocomposite MSM PDs on PES by introducing a SiO(x)(CH(3)) buffer layer.

Characterizing the fluorescent products of waste activated sludge in dissolved organic matter following ultrasound assisted ozone pretreatments

This study investigated the effects of ozone and ultrasound (US) pretreatments, both individually and combined, on waste activated sludge reduction. Batch tests were conducted first to optimize the individual ozone and US pretreatments. Maximum sludge reduction ratios of 10.89% and 23% were obtained at 0.15g O3/g total solids ozone dose and 1.5W/mL US energy density, respectively. The combined ozone and US pretreatments were studied using response surface methodology. A maximum sludge reduction ratio of 40.14% was achieved by the combined ozone/US pretreatment with an ozone dose of 0.154g O3/g total solids and an US energy density of 1.445W/mL. The analysis of the dissolved organic matter by three-dimensional excitation-emission matrix fluorescence spectroscopy showed that the combined pretreatment was superior to the individual ozone and US pretreatments, and also demonstrated the synergetic effect of these two combined pretreatments.

Impact of temperature, microwave radiation and organic loading rate on methanogenic community and biogas production during fermentation of dairy wastewater

This study analyzed dairy wastewater fermentation in convection- and microwave-heated hybrid reactors at loadings of 1 and 2 kg COD/(m3 d) and temperatures of 35 and 55 °C. The biomass was investigated at a molecular level to determine the links between the operational parameters of anaerobic digestion and methanogenic Archaea structure. The highest production of biogas with methane content of ca. 67% was noted in the mesophilic microwave-heated reactors. The production of methane-rich biogas and the overall diversity of Archaea was determined by Methanosarcinaceae presence. The temperature and the application of microwaves were the main factors explaining the variations in the methanogen community. At 35 °C, the microwave heating stimulated the growth of highly diverse methanogen assemblages, promoting Methanosarcina barkeri presence and excluding Methanosarcina harudinacea from the biomass. A temperature increase to 55 °C lowered Methanosarcinaceae abundance and induced a replacement of Methanoculleus palmolei by Methanosarcina thermophila.

Fabrication of nanobeads from nanocups by controlling scission/crosslinking in organic polymer materials

The development of several kinds of micro/nanofabrication techniques has resulted in many innovations in the micro/nanodevices that support today's science and technology. With feature miniaturization, the fabrication tools have shifted from light to ionizing radiation. Here, we propose a simple micro/nanofabrication technique for organic materials using a scanning beam (SB) of ionizing radiation. By controlling the scission/crosslinking of the material via three-dimensional energy-deposition distribution of the SB, appropriate solvents can easily peel off only the crosslinked region from the bulk material. The technique was demonstrated using a focused ion beam and a chlorinated organic polymer. The polymer underwent main-chain scission upon irradiation, but it crosslinked after high-dose irradiation. Appropriate solvents could easily peel off only the crosslinked region from the bulk material. The technique, 'nanobead from nanocup', enabled the production of desired structures such as nanowires and nanomembranes. It can be also applied to the micro/nanofabrication of functional materials.

Origin of low sensitizing efficiency of quantum dots in organic solar cells

Organic semiconductors are of great interest for application in cheap and flexible solar cells. They have a typical absorption onset in the visible. Infrared light can be harvested by use of lead-chalcogenide quantum dot sensitizers. However, bulk-heterojunction solar cells with quantum-dot sensitizers are inefficient. Here we use ultrafast transient absorption and time-domain terahertz spectroscopy to show that charge localization on the quantum dot leads to enhanced coulomb attraction of its counter charge in the organic semiconductor. This localization-enhanced coulomb attraction is the fundamental cause of the poor efficiency of these photovoltaic architectures. It is of prime importance for improving solar cell efficiency to directly photogenerate spatially separated charges. This can be achieved when both charges are delocalized. Our findings provide a rationalization in the development of photovoltaic architectures that exploit quantum dots to harvest the near-infrared part of the solar spectrum more efficiently.

Sunlight-induced reduction of ionic Ag and Au to metallic nanoparticles by dissolved organic matter

Despite the possible occurrence of metal nanoparticles in the environment due to the discharge of engineered nanoparticles and the natural transformation of metal ions into metal nanoparticles, little is known about the transformation mechanism, fates, behaviors, and effects of these nanoparticles in the environment. Here, we show that dissolved organic matter (DOM) in environmental waters can mediate the reduction of ionic Ag and Au to their metallic nanoparticles under natural sunlight, suggesting that this process may be general for metals with high reduction potential. We demonstrated that the reduction was mediated by superoxide from photoirradiation of the phenol group in DOM, and the dissolved O(2) significantly enhanced the formation of Ag nanoparticles. These results imply that previous knowledge about O(2)-induced dissolution and its effect on persistence of Ag nanoparticles should be reconsidered in a sunlit DOM-rich aqueous environment. This study can also shed light on understanding possible natural sources of Ag and Au nanoparticles in the aquatic environment, which is possibly critical in the supergene enrichment of Ag and Au.

Transformation of organic-inorganic hybrid films obtained by molecular layer deposition to photocatalytic layers with enhanced activity

We present the transformation of organic-inorganic hybrid titanicone films formed by TiCl(4) as metal precursor and ethylene glycol (EG) using solvent-free MLD to highly active photocatalytic films. The photocatalytic activities of the films were investigated using hydroxyl-functionalized porphyrin as a spectroscopic marker. TEM imaging and electron diffraction, XPS, UV-vis spectroscopy, and spectroscsopic ellipsometry were employed for structural and composition analyses of the films. The photocatalytic activity of Ti-EG films was investigated for different anneal temperatures and compared to TiO(2) films prepared by ALD using TiCl(4) as metal precursor and H(2)O (TiO(2) films). Overall, our results indicate that the photocatalytic activity of the thermally annealed Ti-EG film is about 5-fold increased compared to that of the TiO(2) film prepared by ALD for optimal process conditions. The combined results indicate that the structural and photocatalytic properties can be assigned to three states: (I) amorphous state, intermediate dye loading, low photocatalytic activity, (II) intermediate film state with both crystalline and amorphous regions, high dye loading, high catalytic activity, and (III) highly crystalline film with low dye loading and low photocatalytic activity. The formation of photocatalytic nanotubes (NTs) is demonstrated using sacrificial Ge nanowires (NWs) scaffolds to yield Ti-EG NT structures with controllable wall thickness structures and enhanced dye loading capacity. Our results demonstrate the feasibility and high potential of MLD to form metal oxides with high photocatalytic activity.

Nanoscale geometric electric field enhancement in organic photovoltaics

Generic design rules for electrode-organic semiconductor contacts that transcend specific materials are urgently required to guide the development of new electrodes and provide a framework for engineering this important class of interface. Herein a novel nanostructured window electrode is utilized in conjunction with three-dimensional electrostatic modeling to elucidate the importance of geometric electric field enhancement effects at the electrode interfaces in organic photovoltaics. The results of this study show that nanoscale protrusions at the electrode surfaces in organic photovoltaics dramatically improve the efficiency of photogenerated charge carrier extraction to the external circuit and that the origin of this improvement is the local amplification of the electrostatic field in the vicinity of said protrusions. This wholly geometric approach to engineering electrodes at the nanoscale is materials generic and can be employed to enhance the efficiency of charge carrier injection or extraction in a wide range of organic electronic devices.

Synthesis, characterization, photophysical properties of a novel organic photoswitchable dyad in its pristine and hybrid nanocomposite forms

In the present paper the method of synthesis and characterization of a novel organic dyad, 3-(1-Methoxy-3,4-dihydro-naphthalyn-2-yl-)-1-p-chlorophenyl propenone, have been reported. In this paper our main thrust is to fabricate new hybrid nanocomposites by combining the organic dyad with different noble metals, semiconductor nanoparticle and noble metal-semiconductor core/shell nanocomposites. In this organic dyad, donor part is 1-Methoxy-3, 4-dihydro-naphthalen-2-carboxaldehyde with the acceptor p-chloroacetophenone. We have carried out steady state and time-resolved spectroscopic measurements on the dyad and its hybrid nanocomposite systems. Some quantum chemical calculations have also been done using Gaussian 03 software to support the experimental findings by theoretical point of view. Both from the theoretical predictions and NMR studies it reveals that in the ground state only extended (E-type or trans-type) conformation of the dyad exists whereas on photoexcitation these elongated conformers are converted into folded forms (Z- or cis-type) of the dyad, showing its photoswitchable character. Time resolved fluorescence spectroscopic (fluorescence lifetime by TCSPC method) measurements demonstrate that in chloroform medium all the organic-inorganic hybrid nanocomposites, studied in the present investigation, possess larger amount of extended conformers relative to folded ones, even in the excited singlet state. This indicates the possibility of slower energy destructive charge recombination rates relative to the rate processes associate with charge-separation within the dyad. It was found that in CHCl3 medium, the computed charge separation rate was found to be approximately 10(8) s(-1) for the dyad alone and other hybrid nanocomposite systems. The rate is found to be faster than the energy wasting charge recombination rate approximately 10(2)-10(1) s(-1), as observed from the transient absorption measurements for the corresponding hybrid systems. It indicates the conformational geometry has a great effect on the charge-separation and recombination rate processes. The suitability for the construction of efficient light energy conversion devices especially with Ag-Dyad nanocomposite of all the systems studied here is hinted from the observed long ion-pair lifetime.

Effects of UV 254 irradiation on residual chlorine and DBPs in chlorination of model organic-N precursors in swimming pools

Ultraviolet (UV) irradiation is commonly applied as a secondary disinfection process in chlorinated pools. UV-based systems have been reported to yield improvements in swimming pool water and air chemistry, but to date these observations have been largely anecdotal. The objectives of this investigation were to evaluate the effects of UV irradiation on chlorination of important organic-N precursors in swimming pools. Creatinine, L-arginine, L-histidine, glycine, and urea, which comprise the majority of the organic-N in human sweat and urine, were selected as precursors for use in conducting batch experiments to examine the time-course behavior of several DBPs and residual chlorine, with and without UV(254) irradiation. In addition, water samples from two natatoria were subjected to monochromatic UV irradiation at wavelengths of 222 nm and 254 nm to evaluate changes of liquid-phase chemistry. UV(254) irradiation promoted formation and/or decay of several chlorinated N-DBPs and also increased the rate of free chlorine consumption. UV exposure resulted in loss of inorganic chloramines (e.g., NCl(3)) from solution. Dichloromethylamine (CH(3)NCl(2)) formation from creatinine was promoted by UV exposure, when free chlorine was present in solution; however, when free chlorine was depleted, CH(3)NCl(2) photodecay was observed. Dichloroacetonitrile (CNCHCl(2)) formation (from L-histidine and L-arginine) was promoted by UV(254) irradiation, as long as free chlorine was present in solution. Likewise, UV exposure was observed to amplify cyanogen chloride (CNCl) formation from chlorination of L-histidine, L-arginine, and glycine, up to the point of free chlorine depletion. The results from experiments involving UV irradiation of chlorinated swimming pool water were qualitatively consistent with the results of model experiments involving UV/chlorination of precursors in terms of the behavior of residual chlorine and DBPs measured in this study. The results indicate that UV(254) irradiation promotes several reactions that are involved in the formation and/or destruction of chlorinated N-DBPs in pool settings. Enhancement of DBP formation was consistent with a mechanism whereby a rate-limiting step in DBP formation was promoted by UV exposure. Promotion of these reactions also resulted in increases of free chlorine consumption rates.

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.

Enhanced biogas production from anaerobic codigestion of solid waste by sonolysis

This paper examines the effectiveness of sonolysis in improving the anaerobic biodegradability of the organic fraction of municipal solid waste coming from mechanical selection, thus enhancing biogas production and energy recovery as well. Methane yield of solid organic material anaerobic digestion is significantly affected by substrate availability that was evaluated, in this investigation, through organic matter solubilisation tests carried out at different conditions of ultrasound treatment. Results show that sonolysis can significantly improve the solubilisation of organic solid waste, thus allowing higher biogas production from anaerobic treatment of sonicated substrates. After 45 days, the biogas produced during anaerobic codigestion tests for the sonicated mixture was 24% higher than untreated one. Therefore, these results can lay the basis for the development of technologies useful to produce high biogas quantities, in order to improve clean energy generation from biowaste.

Ultrasound-assisted lipase-catalyzed transesterification of soybean oil in organic solvent system

This work reports the transesterification of soybean oil with ethanol using two commercial immobilized lipases under the influence of ultrasound irradiation. The experiments were performed in an ultrasonic water bath, following a sequence of experimental designs to assess the effects of temperature, enzyme and water concentrations, oil to ethanol molar ratio and output irradiation power on the reaction yield. Results show that ultrasound-assisted lipase-catalyzed transesterification of soybean oil with ethanol might be a potential alternative route to conventional alkali-catalyzed method, as high reaction yields (~90 wt.%) were obtained at mild irradiation power supply (~100 W), and temperature (60 °C) in a relatively short reaction time, 4h, using Lipozyme RM IM as catalyst. The repeated use of the catalyst under the optimum experimental condition resulted in a decay in both enzyme activity and product conversion after two cycles. The use of Novozym 435 led to lower conversions (about 57%) but the enzyme activity was stable after eight cycles of use, showing, however, a reduction in product conversion after the forth cycle.

Bi-component semiconductor oxide photoanodes for the photoelectrocatalytic oxidation of organic solutes and vapours: a short review with emphasis to TiO2-WO3 photoanodes

The use of binary semiconductor oxide anodes for the photoelectrocatalytic oxidation of organic species (both in solution and gas phase) is reviewed. In the first part of the review, the principle of electrically assisted photocatalysis is presented, the preparation methods for the most common semiconductor oxide catalysts are briefly mentioned, while the advantages of appropriately chosen semiconductor combinations for efficient UV and visible (vis) light utilization are highlighted. The second part of the review focuses on the discussion of TiO(2)-WO(3) photoanodes (among the most studied bi-component semiconductor oxide systems) and in particular on coatings prepared by electrodeposition/electrosynthesis or powder mixtures (the focus of the authors' research during recent years). Studies concerning the microscopic, spectroscopic and photoelectrochemical characterization of the catalysts are presented and examples of photoanode activity towards typical dissolved organic contaminants as well as organic vapours are given. Particular emphasis is paid to: (a) The dependence of photoactivity on catalyst morphology and composition and (b) the possibility of carrying out photoelectrochemistry in all-solid cells, thus opening up the opportunity for photoelectrocatalytic air treatment.

Photochemical hydrogen production from water using three-dimensional Zn-Pd metal-organic frameworks

A Zn-Pd heterometallic metal-organic framework (MOF) based on 3,5-pyridine-dicarboxylic acid (H2-pydc), namely [Zn2(H2O)3{PdCl2(pydc)2}]n (Zn-Pd-2) was successfully synthesized by a slow diffusion method and characterized by single-crystal X-ray diffraction, CHN elemental analysis, FT-IR spectroscopy, thermogravimetric (TG) analysis and N2 gas adsorption measurement. The single-crystal X-ray analysis revealed that the framework morphology of Zn-Pd-2 is as same as that of [Zn2(DMF)3{PtCl2(pydc)2}]n. The Zn-Pd-2 was found to be an effective catalytic performance for the photochemical reduction of water in a well-known photo-system made up of [Ru(bpy)3Cl2] (bpy = 2,2'-bipyridine), MV(2+) (methyl-viologen) and Na2 EDTA (Disodium ethylenediaminetetraacetate); 20.2 turnover based on Zn-Pd-2 was achieved at 4 h irradiation.