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The interplay on anatase TiO2photoactivity between particle morphology and gold nanoparticles (NPs) deposition, via either deposition–precipitation (DP) or photodeposition (P), is here investigated by evaluating the photoactivity of Au modified anatase (Au/TiO2) nanocrystals with either a pseudospherical shape or a nanosheet structure in both reduction and oxidation test reactions. The presence of Au NPs on the anatase surface only slightly affects its photoactivity in Cr(VI) reduction, which is kinetically limited by the anodic half-reaction, whereas a larger exposure of highly oxidant {001} facets is beneficial for overcoming this rate-determining step. In the photocatalytic oxidation of both formic acid, proceeding through a direct mechanism, and rhodamine B (RhB) on surface fluorinated photocatalysts, occurring through a hydroxyl-radical-mediated mechanism, the presence of gold NPs produces a significant photoactivity increase only with spherically shaped photocatalysts, mainly exposing {101} facets. These results are rationalized in light of the preferential migration of photogenerated, oppositely charged carriers toward different crystal facets. In fact, when the Au/TiO2material mainly exposes the more oxidant {001} facets, where photoproduced holes preferentially migrate, recombination between these latter and the electrons captured by Au NPs is favored. Instead, Au NPs on {101} facets efficiently capture photopromoted electrons, preferentially migrating toward such facets with a consequent improvement of photoproduced charge separation.

The dynamics of photopromoted electrons in BiVO4, WO3, and WO3/BiVO4heterojunction electrodes has been directly probed by transient absorption (TA) midinfrared (mid-IR) spectroscopy in the picosecond to microsecond time range. By comparison of the dynamics recorded with the two individual oxides at 2050 cm–1with that of the heterojunction system after excitation at different wavelengths, electron-transfer processes between selectively excited BiVO4and WO3have been directly tracked for the first time. These results support the charge carrier interactions which were previously hypothesized by probing the BiVO4hole dynamics through TA spectroscopy in the visible range. Nanosecond mid-IR TA experiments confirmed that charge carrier separation occurs in WO3/BiVO4electrodes under visible-light excitation, persisting up to the microsecond time scale.

In the present work, two H2evolution photocatalysts were prepared by employing two different oxides, TiO2and zirconium titanate (ZrTiO4), as the support of various copper phases. For both the supports the same Cu loading (0.5% w/w) was adopted, but two different impregnation procedures have been followed, leading to different forms of Cu in the final composite material that are: (i) Cu(II) species dispersed on the oxide surface and (ii) Cu2O particles dispersed on the oxide surface. The present paper based on the parallel use of photocatalytic test and spectroscopic analysis performed in catalytic conditions illustrates the evolution of photocatalytic systems occurring during the H2evolution reaction tests, pointing out that the as-prepared materials represent a pre-catalyst and they are modified during irradiation leading to the real working systems different from the starting ones. The herein presented spectroscopic analysis aims to contribute to the living debate on the oxidation state of copper in mixed Cu/oxide materials and on its role in hydrogen evolution under photocatalytic conditions.

The time-resolved photoluminescence (PL) in the nanosecond time scale of TiO2materials undoped or codoped with nitrogen and fluorine (N,F-doping) and modified by noble metals (NM, i.e. Au or Pt) nanoparticles (NPs) photodeposition has been systematically investigated in relation to their photocatalytic activity in hydrogen production. The main aim of the study is to elucidate the origin of the NM-dependent synergistic effects in photoactivity produced by N,F-doping of TiO2and NM NPs deposition on the oxide surface. While TiO2doping with fluorine and nitrogen introduces new stabilized luminescent defective trap states below the conduction band revealed by long-living PL components, the presence of NM NPs on the TiO2surface produces a PL intensity suppression, which is more relevant for Au- rather than for Pt-NPs containing materials. Time-resolved PL analysis indicates that the electron transfer occurring at the TiO2/metal interface is affected by both the defective structure of anatase N,F-doped TiO2and the type of NM (Au or Pt). In particular, Au rather than Pt NPs appear to strongly interact with the charge carriers trapped at surface defect sites, gold NPs being expected to preferentially grow on such sites during photodeposition. Furthermore, plasmonic gold NPs excitation upon PL light absorption is evidenced by the PL spectral shape variation observed only in the case of Au/TiO2. Thus, the larger synergistic effect on photocatalytic hydrogen production observed upon Au NPs photodeposition on N,F-doped TiO2results from the opening of a new efficient electron transfer path from luminescent defective trap states on doped TiO2to Au NPs, where proton reduction occurs.

Photoelectrodes with the WO3/BiVO4heterojunction architecture are among the most efficient semiconductor oxide-based photoanodes for water oxidation. However, because of the different experimental conditions employed in their photoelectrochemical characterization (in particular the nature and concentration of the contact electrolyte and the pH of the solution), a direct and unambiguous comparison of their performance obtained in different laboratories is often quite difficult. In this work, we systematically tested identical WO3/BiVO4photoanodes in contact with solutions of the most commonly used electrolytes, i.e. Na2SO4and the potassium phosphate buffer (KPi), at various electrolyte concentration and pH. Furthermore, WO3/BiVO4photoanodes protected with a Ni/Fe oxyhydroxide oxygen evolution catalyst were also tested under identical conditions. In contact with KPi solutions, both unprotected and protected electrodes produce higher photocurrent than in contact with Na2SO4solutions, but they proved to be less stable, particularly under basic conditions. WO3/BiVO4heterojunction systems modified by deposition of the Ni/Fe oxyhydroxide cocatayst proved to be more stable and to produce higher photocurrent, with a cathodic shift of the photocurrent onset.

AbstractThe accumulation of nitrogen compounds represents a pivotal problem in the management of fish culture. Several methods were investigated in the last decades for treatment of waste waters, and the use of photocatalytic materials has received increasing attention. The photocatalytic degradation (PCD) process with titanium dioxide (TiO2) represents the most promising single-step method to promote the removal of nitrogen compounds from water. The present study compares for the first time the effects on fish culture of a classical mechanical, biological, and ultraviolet purification system to a TiO2-PCD one, with particular emphasis on water chemistry and on physiological responses in zebrafish. Fish were exposed for 14 days to the two different purification systems and samplings were performed 7 and 14 days after the experiment beginning. The photocatalytic system showed excellent efficiency in removing nitrogen compounds from water with no significant adverse effects on fish. Physiological analysis on fish samples included histological analysis of gills and gut, TUNEL assay of the gills, and real-time polymerase chain reaction (liver) of genes involved in stress response and growth. No significant biological alterations were detectable on the cultured fish.

WO3/BiVO4heterojunction photoanodes can be efficiently employed in photoelectrochemical (PEC) cells for the conversion of water into molecular oxygen, the kinetic bottleneck of water splitting. Composite WO3/BiVO4photoelectrodes possessing a nanoflake-like morphology have been synthesized through a multistep process and their PEC performance was investigated in comparison to that of WO3/BiVO4photoelectrodes displaying a planar surface morphology and similar absorption properties and thickness. PEC tests, also in the presence of a sacrificial hole scavenger, electrochemical impedance analysis under simulated solar irradiation, and incident photon to current efficiency measurements highlighted that charge transport and charge recombination issues affecting the performance of the planar composite can be successfully overcome by nanostructuring the WO3underlayer in nanoflake-like WO3/BiVO4heterojunction electrodes.

Preferential growth of anatase crystallites along different directions is known to deeply affect their photocatalytic properties, especially with respect to the exposure of the reactive {001} facets. Its extent can be easily quantified through simple geometric calculations, on the basis of crystal sizes extracted for specific directions by means of X-Ray Diffraction data analysis. Nevertheless, the actual results depend on the method employed for such a quantification. Here we report on a comparative morphological investigation, performed by employing the Scherrer equation and the line profile from Rietveld refinements, on shape-controlled anatase photocatalysts produced by employing HF as capping agent. Compared to the Rietveld-based method, the use of the Scherrer equation produces a systematic underestimation of crystallite dimensions, especially concerning the [100] direction, which in turn causes the percentage of exposed {001} crystal facets to be underestimated. Neglecting instrumental-related effects may further reduce the estimate.

The effects of TiO2surface modification by Ru nanoparticles (NPs) deposition have been investigated in the photocatalytic decomposition of aqueous ammonia. Two main Ru NPs deposition routes were chosen, i.e. (i) the deposition of surfactant-stabilized preformed metal NPs and (ii) a modified version of the well-known deposition-precipitation technique, employing urea as precipitating agent. Other Ru/TiO2photocatalysts were prepared (iii) by simply grafting Ru(III) metal ions on TiO2, which were tested either as prepared or (iv) after their thermal reduction under H2atmosphere, in order to obtain Ru NPs in full metallic state. The role played also by the relative nominal metal amount on the so obtained photocatalyst powders was investigated in terms of both ammonia conversion and selectivity towards mildly oxidized N2or highly oxidized nitrite and nitrate ions. The Ru NPs deposition technique was found to affect the reaction paths especially in terms of products selectivity, with fully reduced Ru NPs on TiO2being able to promote the environmentally friendly, highly desirable photocatalytic conversion of ammonia into innocuous N2.

Crystal shape control on a series of anatase photocatalysts was achieved by varying the amount of HF employed as a capping agent in their hydrothermal synthesis. A systematic comparison between their physicochemical properties, determined by several complementary surface and bulk techniques before and after thermal treatment at 500 °C, allowed one to discern the influence of the relative amount of exposed {001} crystal facets among a series of effects simultaneously affecting their oxidative photocatalytic activity. The results of both formic acid and terephthalic acid photo-oxidation test reactions point to the primary role played by calcination in making {001} facets effectively photoactive. Annealing not only removes most of the residual fluorine capping agent from the photocatalyst surface, thus favoring substrate adsorption, but also produces morphological modifications to a crystal packing that makes accessible a larger portion of surface {001} facets due to the unpiling of platelike crystals. The photocatalyst bearing the highest amount of exposed {001} facets (60%) shows the highest photoactivity in both the direct and the •OH-radical-mediated photocatalytic test reaction.

Aiming at understanding how plasmonic reactions depend on important parameters such as metal loading and strong metal–support interaction (SMSI), we report the plasmonic photodegradation of formic acid (FA) under green LED irradiation employing three TiO2supports (stoichiometric TiO2, N-doped TiO2, black TiO2) modified with Au nanoparticles (NPs) 3–6 nm in size. The rate of FA photooxidation follows different trends depending on Au loading for stoichiometric and doped Au/TiO2materials. In the first case, the only contribution of hot electron transfer produces a volcano-shaped curve of photoreaction rates with increasing Au loading. When TiO2contains intra-bandgap states the photoactivity increases linearly with the amount of Au NPs due to the concomitant enhancement produced by hot electron transfer and plasmon resonant energy transfer (PRET). The role of PRET is supported by finite element method simulations, which show that the increase in both Au NP inter-distance and SMSI enhances the probability of charge carrier generation at the Au/TiO2interface.

Bismuth vanadate (BiVO4) with a band gap of ∼2.4 eV has emerged as one of the visible photocatalysts that can absorb light below 520 nm. The electron/hole pairs that are generated following BiVO4band gap excitation are effective for water splitting, especially when BiVO4is combined with other metal oxides such as WO3. We report a solution processed method for designing transparent WO3/BiVO4heterojunction electrodes and observe a synergistic effect on the photoelectrochemical activity of WO3/BiVO4, with the combined system performing dramatically better than either individual component. Using ultrafast transient absorption spectroscopy, we elucidated the electronic interaction between WO3and excited BiVO4. Moreover, the photocatalytic reduction of thionine by WO3/BiVO4as well as by each individual oxide component is used to track electron injection processes and determine the energetics of the studied systems. In the composite WO3/BiVO4film a shifted quasi-Fermi level results, due to electronic equilibration between the two materials. The better performance of WO3/BiVO4heterojunction electrodes is thus a consequence of the electron injection from BiVO4into WO3, followed by back electron transfer from WO3to the holes in BiVO4.

TiO2photocatalysts, either doped with different amounts of fluorine or boron, or codoped with boron and fluorine, were prepared by sol–gel synthesis, followed by calcination at different temperatures (500–700 °C), and characterized by XRPD, BET, XPS, and UV–vis absorption analyses. The oxidative decompositions of both formic and acetic acid were employed as photoactivity test reactions, also in comparison with previous results obtained with NF-codoped TiO2. A detailed XPS analysis revealed the presence of B2O3on the surface of B-doped and BF-codoped TiO2, which could be removed by washing under acidic conditions and had no beneficial role in phototocatalysis. A correlation was found between the photoactivity of full anatase TiO2materials calcined at 500 °C, singly doped or codoped with nitrogen, fluorine, and boron, and their specific surface area, pointing to a major role of the latter, not of the different dopants, on photoactivity. Only samples containing fluorine, as dopant or codopant, exhibit a photoactivity increase with increasing the calcination temperature to 700 °C. This fact, together with an action spectra analysis on photocatalysts calcined at different temperatures, evidenced that only fluorine is responsible for the photoactivity increase in the UVA region observed with full-anatase, highly crystalline doped TiO2calcined at high temperature.

Aiming at discerning the role of fluorine from that of nitrogen as a dopant in N,F-codoped TiO2, a series of HF-doped TiO2photocatalysts were investigated in the decomposition of formic and acetic acid in aqueous suspensions, also as a function of the irradiation wavelength (action spectra analysis), in comparison with recent results obtained with an analogous series of NH4F-doped TiO2photocatalysts. Visible light absorption around 420 nm, which was found to be inactive in acetic acid decomposition, is definitely shown to be associated with nitrogen doping, whereas the enhanced absorption at ca. 365 nm, increasing with increasing calcination temperature, can be unambiguously attributed to structural modifications induced by fluorine doping. Action spectra analysis confirms that this absorption is active in acetic acid decomposition, in both HF- and NH4F-doped TiO2photocatalysts. From time-resolved photoluminescence (PL) spectroscopy analysis, a clear correlation is outlined between the photoactivity of the materials and the long-lasting component of the PL signal, which increases with the calcination temperature and is related to the formation of surface defects. Thus, fluorine doping, followed by calcination at high temperature, increases the amount of surface traps originating the long-lasting PL signal, which are beneficial in photoactivity by ensuring long-living photoproduced charge couples.

The photocatalytic production of hydrogen from aqueous systems is reviewed, stressing the very promising features of the process as an environmentally friendly, perfectly renewable way to produce hydrogen, the ideal fuel for the future. Starting with a brief historical background, the most recent achievements in the field on the basis of both relevant patents and published literature, are discussed here, with particular emphasis on the development of innovative materials able to capture a larger portion of the solar spectrum with respect to traditional photocatalytic materials, and on the different setups and devices which have been developed and tested.

The photocatalytic activity of titanium dioxide modified by surface fluorination (F-TiO2) and by differently deposited gold nanoparticles (Au/TiO2) was tested in the degradation of organic substrates, i.e. mainly formic acid and the azo dye Acid Red 1 (AR1), in comparison to that of unmodified titania. The effect of different noble metals deposition on TiO2 was also investigated in the photocatalytic production of hydrogen from water solutions. Surface fluorination increases the rate of photocatalytic oxidation proceeding through a hydroxyl radical-mediated path. These radicals accumulated in higher amount on F-TiO2, because of the shielding effect of adsorbed fluoride. By contrast, the degradation of substrates implying direct interaction with the photogenerated holes occurred at a lower rate on F-TiO2, because of their hampered absorption on the fluorinated surface. The method employed to reduce Au(III) to metallic gold in the preparation of Au/TiO2 photocatalysts was found to affect their photoactivity, also by modifying the surface properties of TiO2. The presence of gold on TiO2 facilitates both the electron transfer to O2 and the mineralization of formic acid, proceeding mainly through direct interaction with photoproduced valence band holes. For substrates undergoing mainly oxidation through a hydroxyl radical mediated mechanism, the photogenerated holes may partly oxidize gold nanoparticles, which consequently act as recombination centers of photoproduced charge carriers. Photocatalytic hydrogen production tests, either from water or from methanol reforming, performed in a special set up, closed recirculation laboratory scale photoreactor employing titanium dioxide and noble-metals-modified titanium dioxide samples prepared by different techniques, confirmed the main role of noble metals nanoparticles on TiO2 in facilitating electron transfer reactions also under anaerobic conditions. Higher hydrogen production rates were attained with the photocatalysts in contact with the vapor phase, i.e. in the absence of the liquid phase mass transfer limitations of aqueous suspensions. The activity of metal nanoparticles-containing photocatalysts prepared by one step flame spray pyrolysis was always higher than that of photocatalysts prepared by deposition on pre-formed gold nanoparticles on TiO2 , most probably because of the better noble metal dispersion on the photocatalyst surface.

Abstract: The photocatalytic activity of Au modified titanium dioxide was evaluated in the photodegradation of the azo dye Acid Red 1 (AR1) under 254 nm irradiation. Noble metal nanoparticles were deposited on TiO2 either through depositionprecipitation (DP), or by immobilisation of preformed metallic sols (polyvinylalcohol (PVA)/NaBH4 or tetrakis(hydroxymethyl)phosphonium chloride (THPC)/NaOH systems). Gold nanoparticles on the photocatalyst surface had dimensions of around 3–4 nm in diameter, as determined by HRTEM analysis, and exhibited visible light plasmon absorption. THPC Au/TiO2 appears to be the most photoactive amongst the photocatalysts with a 1 wt.% Au loading, while among THPC samples with different Au loadings (0.5–20.0 wt.%) the maximum photoactivity was attained with 5 wt.% Au/TiO2. The higher AR1 photodegradation rate observed on Au/TiO2 at basic pH can be related to the higher concentration of hydroxyl anions at the interface: these are able to effectively scavenge photoproduced valence band holes, possibly in competition with Au0 oxidation to Au+.

The photocatalytic activity of Au modified titanium dioxide was evaluated in the photodegradation of the azo dye Acid Red 1 (AR1) under 254 nm irradiation. Noble metal nanoparticles were deposited on TiO either through depositionprecipitation (DP), or by immobilisation of preformed metallic sols (polyvinylalcohol (PVA)/NaBH or tetrakis(hydroxymethyl)phosphonium chloride (THPC)/NaOH systems). Gold nanoparticles on the photocatalyst surface had dimensions of around 3-4 nm in diameter, as determined by HRTEM analysis, and exhibited visible light plasmon absorption. THPC Au/TiO appears to be the most photoactive amongst the photocatalysts with a 1 wt.% Au loading, while among THPC samples with different Au loadings (0.5-20.0 wt.%) the maximum photoactivity was attained with 5 wt.% Au/TiO. The higher AR1 photodegradation rate observed on Au/TiO at basic pH can be related to the higher concentration of hydroxyl anions at the interface: these are able to effectively scavenge photoproduced valence band holes, possibly in competition with Au oxidation to Au. [ABSTRACT FROM AUTHOR]

The effect of TiO2surface fluorination on the hydrogen peroxide evolution occurring in photocatalytic runs was investigated employing the azo dye Acid Red 1 (AR1) and two model organic molecules with acidic properties, i.e. formic acid (FA) and benzoic acid (BA), as substrates of oxidative degradation. While AR1 and BA photocatalytic degradation on fluorinated titanium dioxide (F–TiO2) was markedly faster than on unmodified TiO2, because of enhanced hydroxyl radical formation, H2O2concentration during the photodegradation of both substrates on F–TiO2was lower, possibly because of the reduced rate of interfacial electron transfer. By contrast, FA underwent slower photocatalytic degradation on F–TiO2, but, at the same time, hydrogen peroxide concentration was relatively high, while no H2O2could be detected during FA photodegradation on unmodified TiO2. Photocatalytic runs in the presence of the nitrate anion, able to react with the CO2−species produced from FA oxidation, but not with conduction band electrons, demonstrated that CO2−plays a relevant role in H2O2formation during FA degradation on F–TiO2. In fact, surface fluoride, having a shielding effect at the semiconductor–water interface, not only inhibits the photocatalytic decomposition of H2O2, but also favours CO2−desorption and reaction with dissolved O2, generating H2O2. By contrast, CO2−mainly gives electron transfer to the conduction band of naked TiO2and surface reduction of the photocatalytically produced H2O2.

Photocatalysis and sonolysis exhibit synergistic effects in the degradation of organic molecules in aqueous suspension, when low ultrasound frequency (i.e. 20 kHz) is employed. The degradation of the azo dye Acid Orange 8 in aqueous suspensions was systematically evaluated under sonolysis, photocatalysis and sonophotocatalysis as a function of dye concentration, amount and type of photocatalyst (TiO₂ or ZnO) and catalase addition, in terms of pseudo-first-order degradation rate constants. The evolution of hydrogen peroxide was also monitored. Synergistic effects of the combination of ultrasound and photocatalysis should mainly involve the aqueous phase and be due to an increased concentration of reactive radicals, consequent to the action of ultrasound on the peroxide species produced by both photocatalysis and sonolysis.

Water molecules retained in native cellulose gels obtained from Acetobacter xylinum (AX) were displaced by poly(ethylene glycol)s (PEG) of different molecular weight. The so obtained native cellulose/PEG material, characterized in film form by differential scanning calorimetry, dynamic mechanical thermal analysis and wide angle X-ray scattering, revealed that strong interactions occur between PEG and cellulose and that the polymer mixture is in the rubbery state at ambient temperature. Moreover, it could be dyed in supercritical carbon dioxide by disperse dyes, thus exhibiting typically lipophilic properties and suitability to be employed as a biocompatible support for lipophilic active species.

Poly(ethylene terephthalate) (PET) and cotton fibres, treated in an appositely set up RF SF₆ plasma reactor under different operating conditions, were characterised by XPS, EPR, DSC, XRD, ATR analyses, water contact angle and water droplet roll­off angle measurements. The ageing of plasma­treated samples was also investigated under different post­treatment conditions. Plasma treatment led to efficient implantation of fluorine atoms on the surface of both polymers; this resulted in water repellence without altering the bulk properties of the polymers. The radical species formed in the plasma­activated polymer surface were involved in its fluorination and in the subsequent uptake of atmospheric oxygen. Surface reorganisation of polymer segments, tending to reduce the interfacial energy between the polymer and the phase in contact with it, induced the surface modifications observed under ageing and in samples plasma­treated several times. An increase in the depth of the fluorinated layer, leading to outstanding stable hydrorepellence, was achieved by repeated SF₆ plasma treatments, followed by surface rearrangements favoured by swelling.

Silk samples, treated in an appositely set-up radio frequency SF6 plasma reactor under different operation conditions, were characterized by XPS, EPR, DSC, XRD, ATR analyses and water contact angle measurements, also as a function of storage time after the treatment. Efficient attachment of fluorine atoms on the polymer surface occurred during the plasma treatment, imparting water repellence to it. Also the percentage of surface oxygen increased after the treatment, partially as a consequence of radical scavenging by molecular oxygen and the formation of peroxides. An increase in silk crystallinity during the treatment seems to contribute to ensuring durable water repellence properties.

A series of Fe-silicalites with MFI structure, employed as catalysts in the title reaction, was investigated by FTIR analysis, using pyridine as the probe molecule for acidity determination. The oxidation reaction was also monitored by FTIR spectroscopy on the best-performing catalyst. An optimal content and distribution of extra-framework iron assures high selectivity, while high acidity increases benzene conversion, but lowers the phenol yield. Benzene conversion to phenol occurs on N₂O-pretreated Fe-silicalite catalysts only and N₂O does not adsorb as such on the catalyst, even at low temperature, but undergoes decomposition: this confirms the activating role of N₂O in the reaction mechanism. Under the experimental conditions adopted in reaction monitoring, the yield of adsorbed phenol is maximal around 550 K and the reaction is paralleled by the complete oxidation of benzene to CO₂.

The low-temperature uptake of the flavouring agents limonene and vanillin from supercritical carbon dioxide (CO2SCF) into films of a poly(ethylene terephthalate)-based copolyester (PET-G), polycaprolactam (PA6), and isotactic poly(propylene) (PP), also blended with hydrogenated oligo(cyclopentadiene) or polycaprolactam, have been investigated through thermogravimetric determination of the additive amount released in the temperature range 30–230°C. The uptake of an additive strongly depends on its relative solubility in the polymer and in CO2SCF: limonene can easily be transferred into lipophilic PP-based and PET-G polymers, also due to the plastifying action of CO2SCF on PET-G, while only the more polar vanillin can be taken up by hydrophilic PA6. The CO2SCF treatment is particularly suitable for the low-temperature uptake of heat-sensitive flavours into polymeric substrates to be used in “active” packaging.

Poly(propylene)/aromatic polyamide blends were prepared by melt mixing, without or with the addition of an interfacial modifier, viz. a poly(propylene) polymer grafted with 1 wt.-% of maleic anhydride. The characteristics of these polymer blends were investigated by differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy and surface tension measurements. The transport parameters of oxygen through films of such polymer blends were also determined by the differential permeation method. The new compatibilized blend materials, being transparent, sterilizable, dimensionally stable, and having very high barrier properties towards oxygen, are particularly suitable for packaging applications.

The photoreversible EZ isomerization of a series of protonated N-benzylideneanilines (X-C6H5CH=NC6H5-Y; X ≡ H, N(CH3)2; Y ≡ H, NO2) was investigated in concentrated sulphuric acid solution. The UV absorption spectra of the E isomers are practically independent of substituents on benzene rings and suggest a planar conformation for protonated N-benzylideneanilines. The UV spectra of Z isomers were obtained from photostationary state conditions at two wavelengths. Also the quantum yields of E → Z and Z → E photoisomerization are not markedly affected by the ring substituents and are compatible with a photoreversible process occurring through a common excited state.

The morphology, crystallisation and melting behaviour of binary blends prepared by extruding mixtures containing different amounts of starch valerate (SV) and a poly(3-hydroxybutyrate-co-hydroxyvalerate) copolymer have been investigated by optical and scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis and mechanical tensile tests. The absence of apparent phase separation, the increase in spherulite dimensions and the decrease of radial growth rate with increasing SV content, as well as the presence of a single composition-dependent Tg value, evidenced a high degree of compatibility between the two components, up to 20 wt.-% of SV. For higher SV contents, phase separation occurred, confirmed by the appearance of the Tg values of the pure components in thermal analyses.

The natural aging of cellulosic materials (high purity paper, cotton, raw and bleached flax, viscose) was simulated by thermal oxidation in air at constant temperature (123–192°C). Also the synergetic effect of light was investigated at 50–85°C. The kinetics of polymer degradation was followed through intrinsic viscosity measurements and was correlated with the degree of crystallinity, determined by X-ray diffraction, and with the surface oxidation of the investigated samples, evaluated through XPS analysis. At least two constant rate stages were observed in kinetic runs. The acceleration factors and time necessary for simulating a 20-year thermal aging of the investigated cellulosic materials were obtained from the calculated activation parameters by extrapolation of the process rate coefficients to room temperature. Surface oxidation parallel to aging led to the formation of low-molecular-weight, easily removable products in pure cellulose materials, while in lignin-containing materials mainly lignin was involved.

CuWO4is a ternary metal oxide semiconductor with promising properties for photoelectrochemical (PEC) water splitting and solar light conversion, due to its quite low band gap (2.3 eV) and high stability in an alkaline environment. Aiming at understanding the origin of the relatively low PEC efficiency attained with CuWO4photoanodes, we here investigate transparent CuWO4electrodes prepared by a simple solution-based method through the combination of femtosecond transient absorption spectroscopy with electrochemical, PEC, and photochromic characterizations. The very fast recombination dynamics of the charge carriers photogenerated in CuWO4, which is the reason for its low efficiency, is discussed in relation with its PEC performance and with the recently calculated band structure of this material, also in comparison with the behavior of other semiconductor oxides employed in PEC applications, in particular Fe2O3.

Direct experimental evidence of the higher concentration of hydroxyl radicals generated on fluorinated titanium dioxide F–TiO2 under irradiation was obtained by spin-trapping EPR measurements. The faster photoinduced bleaching of the azo dye Acid Red 1 AR1 observed in the presence of F–TiO2was explained by the high affinity of the azo double bond towards OH radicals. Moreover, the pronounced decrease of the AR1 bleaching rate by addition of 2-propanol, as hydroxyl radicals scavenger, on F–TiO2and not on naked TiO2demonstrated that on fluorinated titania AR1 is mainly degraded viaOH radical attack.

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