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The nuclear erythroid 2-related-factor (Nrf2) transcription factor/hemoxygenase 1 (HO-1) is a key regulator of an important neuroprotection response by driving the interpretation of various cytoprotective gene to encode for anti-inflammatory, antioxidant, and detoxifying proteins. Various studies investigated that the upregulation of Nrf2/HO-1 has become the potential therapeutic approach in amyotrophic lateral sclerosis (ALS). Amyotrophic lateral sclerosis is a motor neuron disease in which there is a progressive loss of upper motor neuron and lower motor neurons of the motor cortex, brain stem, and corticospinal tract. A result of this upregulation of Nrf2/HO-1 indicates that in the brain, anti-oxidant capacity is reinforced. Further, this shows a cytoprotective effect against oxidative stress in amyotrophic lateral sclerosis. A study reported functions associated with the Nrf2/HO-1 in the neuronal cell, oligodendrocytes, microglia, and astrocytes. Although ALS's pathogenesis is not yet clear, but it is compelling. The evidence shows any dysfunction in the brain such as mitochondrial dysfunction, protein aggregation, glial cell activation, excitotoxicity, and apoptosis which gives ALS-like symptoms. In this review, we have mainly focused on detailing the downregulation of Nrf2/HO-1, which may be the prime reason and may further serve as a pathological hallmark for ALS development. As surveyed, there are limited targetbased interventions that only provide symptomatic relief but do not cure the disease completely. Dysregulation of the Nrf2/HO-1 signaling pathway leads to many physiological changes contributing to neurological conditions, including ALS. Based on the above view, we summarized the combined role of Nrf2/HO-1 signaling in ALS and explored potential therapeutic strategies for disease improvement through pathway modulators.

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease (MND) characterized by the death of upper and lower motor neurons (corticospinal tract) in the motor cortex, basal ganglia, brain stem, and spinal cord. The patient experiences the sign and symptoms between 55 to 75 years of age, which include impaired motor movement, difficulty in speaking and swallowing, grip loss, muscle atrophy, spasticity, and sometimes associated with memory and cognitive impairments. Median survival is 3 to 5 years after diagnosis and 5 to 10% of the patients live for more than 10 years. The limited intervention of pharmacologically active compounds, that are used clinically, is majorly associated with the narrow therapeutic index. Pre-clinically established experimental models, where neurotoxin methyl mercury mimics the ALS like behavioural and neurochemical alterations in rodents associated with neuronal mitochondrial dysfunctions and downregulation of adenyl cyclase mediated cAMP/CREB, is the main pathological hallmark for the progression of ALS in central as well in the peripheral nervous system. Despite the considerable investigation into neuroprotection, it still constrains treatment choices to strong care and organization of ALS complications. Therefore, this current review specially targeted the investigation of clinical and pre-clinical features available for ALS to understand the pathogenic mechanisms and to explore the pharmacological interventions associated with the up-regulation of intracellular adenyl cyclase/cAMP/ CREB and activation of mitochondrial-ETC coenzyme-Q10 as a future drug target in the amelioration of ALS mediated motor neuronal dysfunctions.

Silver-containing complex oxides present interesting light absorption and electronic properties pointing to their applicability for solar fuel generation and environmental remediation. In this vein, the syntheses, characterization, and photoelectrochemical properties of the Aurivillius oxide, AgBiW2O8, and a triphasic material, AgBiW2O8/Bi2WO6/Ag, are described herein. From UV–vis diffuse reflectance analysis, both oxides’ nanoparticles exhibited intense absorption at wavelengths <455 nm, with an additional band centered at ∼500 nm for the triphasic material, attributed to surface plasmon resonance of the metallic Ag phase. The triphasic material was further characterized by a variety of structural and spectroscopic probes, indicating a defect-rich crystalline structure. Voltammetric measurements were performed in the dark and under simulated solar irradiation with polarization at potentials more negative than the rest potential. Thin film electrodes of both materials showed p-type semiconductor behavior, with enhanced cathodic photocurrent in the presence of electron acceptors in aqueous media.

The ternary compound, CuBi2O4, a 1:1 stoichiometric derivative of the two component oxides CuO and Bi2O3, has attracted attention from the solar water splitting and photocatalysis communities as a p-type semiconductor responsive to visible light. This study demonstrates that solution combustion synthesis (SCS) can be used to prepare powders not only of this compound but also nanocomposites with either CuO or Bi2O3in excess. This was simply done by tuning the SCS precursor mixture composition. The synthesized crystalline samples were characterized by powder X-ray diffraction (with Rietveld refinement for phase purity), diffuse reflectance UV–visible spectroscopy, electron microscopy, and photoelectrochemical (PEC) techniques. The band structure and photoactivity of these oxides were probed by linear sweep voltammetry and by measuring their photoaction spectra (internal photon-to-electron conversion efficiency vs wavelength). The photoactivity (attributed to hydrogen evolution and CO2photoreduction) was considerably improved in the CuO/CuBi2O4nanocomposites because of electron transport of the photogenerated charge carriers between the CuBi2O4and the CuO nanoparticles.

This study reports on the solution combustion synthesis of two different ternary niobium oxides, namely, p-CuNb2O6and n-ZnNb2O6. Such ternary oxides are attractive candidates in the “Holy Grail” search for efficient and stable semiconductors for solar energy conversion and environmental remediation. We demonstrate how this time- and energy-efficient method is capable of synthesizing high surface area and crystalline nanoparticles of the above compounds with enhanced optoelectronic properties. The synthesized crystalline samples were characterized by powder X-ray diffraction (with Rietveld refinement for phase purity), diffuse reflectance UV–visible and Raman spectroscopy, electron microscopy, and photoelectrochemical (PEC) techniques. The band structure of these oxides was probed by linear sweep voltammetry and by measuring their photoaction spectra (internal photon to electron conversion efficiency vs wavelength). The obtained bandgap energy values (1.9 and 3.2 eV for the Cu- and Zn-containing compounds, respectively) were in reasonable agreement with those obtained via electronic structure calculations (2.07 and 3.53 eV). Finally, p-CuNb2O6showed promising activity for the PEC reduction of CO2, while n-ZnNb2O6was active for sulfite and water photooxidation.

This paper describes the solution combustion synthesis, solid-state characterization, photoelectrochemical behavior, and photocatalytic properties of bismuth vanadate (BiVO4). In particular, the influence of combustion precursor was addressed in this study. Bismuth nitrate pentahydrate was used as the bismuth precursor and either vanadium chloride or vanadium oxysulfate was used as the vanadium precursor. Urea, glycine, or citric acid was used as the fuel. Stoichiometric mixtures (1:1) of the fuels and oxidants (with the Bi:V mole ratio also maintained at 1:1) were subjected to solution combustion synthesis. The resultant samples were characterized by X-ray diffraction, highresolution transmission electron microscopy, diffuse reflectance spectrophotometry, thermal analyses, and laser Raman spectroscopy. Methyl orange was used as a probe to test the photocatalytic attributes of the combustionsynthesized (CS) samples, and benchmarked against a commercial bismuth vanadate sample. The CS samples were superior to the commercial benchmark sample, and samples derived from vanadium chloride were superior to vanadium oxysulfate counterparts. The photoelectrochemical properties of the various CS samples were also studied and these samples were shown to be useful both for environmental photocatalytic remediation and water photooxidation applications.

The feasibility of photobleaching and detoxification of three disperse azo dyes, namely, Disperse Orange 1, Disperse Red 1 and Disperse Red 13, in 0.1 mol L-1Na2SO4containing anionic surfactant was investigated using Ti/TiO2nanotubular array electrodes prepared by the electrochemical anodization of Ti foil. The results were compared with nanoporous Ti/TiO2 electrodes prepared by the sol-gel method. After 60 min of photoelectrocatalytic oxidation of solutions containing 5.0 × 10-5mol L-1of Disperse Red 1, Disperse Orange 1 and Disperse Red 13 and 80 mg L-1of anionic surfactant (Emulsogen) under UV light and an applied potential of +1.0 V (vs. Ag|AgCl|satd. KCl reference electrode), 100% of discoloration was obtained for all the dyes investigated. The rate constants for the nanotubular TiO2array were almost 2-3 times higher for the photoelectrocatalytic removal of these dyes compared to their sol-gel derived counterparts. Measurement of TOC removal showed ca. 70% reduction after 3 h of photoelectrocatalytic oxidation and the HPLC chromatograms presented complete extinction of the signals. All the samples of dyes extracted in organic phase, without surfactant influence, presented lower toxicity when submitted to photoelectrocatalytic oxidation suggesting that this process would be a good option to remove disperse azo dyes from aqueous media and decrease their cytotoxicity. However it is worth noting that the Emulsogen anionic surfactant presented an increase in the acute toxicity for human embryonic kidney (HEK293) cells even after photoelectrocatalysis and indicates the requirement of other auxiliary procedures before its own release to the aquatic environment. These results underline the need for caution in interpreting toxicity data when a surfactant is also present in addition to an organic dye.

This review focuses on the electrosynthesis, in situ characterization, and technological applications of Prussian blue analogues with the generic formula AhMk[Fe(CN)6]l·mH2O, where h, k, l, and m are stoichiometric numbers, A = alkali metal cation, and M is a transition metal. Six such metal hexacyanoferrate (MHCF) compounds derived from Cu, Pd, In, V, Co, and Ni are featured in this article against the backdrop of the Prussian blue parent compound itself and other related compounds. The use of cyclic voltammetry and complementary techniques including scanning probe microscopies, quartz crystal microgravimetry, and ac impedance spectroscopy, for studying the growth of MHCF films on targeted substrates, is discussed. Spectroelectrochemical in situ characterization of these films in the UV−visible and IR regions is then reviewed. Finally, the use of Prussian blue and its analogues in devices for displays and “smart” windows, photoimaging, environmental remediation, chemical/biological sensing, energy conversion, and magneto-optic/opto-magnetic switching is described. Electrocatalysis of targeted reactions and structural changes upon ion uptake by the MHCF compounds constitute the other topics in this review.

A description is given of the modification of the adsorption of Tl(I) on a titania (Degussa P-25) surface by the presence of organic or inorganic co-additives in aqueous suspensions. The addition of oxalate, formate, acetate and phosphate anions (the latter at low levels below ~0.03 M) increased Tl(I) adsorption while the phosphate anion (at levels > ~0.03 M) inhibited Tl(I) adsorption. A surface complexation model comprising the titania surface sites, the anchor co-additives and bound Tl(I) species was invoked to explain the adsorption enhancement observed. The data presented build upon and complement those acquired earlier showing how metal ion adsorption on a TiO2surface is strongly influenced by co-additives in the aqueous medium.

Temporal changes in the potential of TiO2 films (supported on Au substrates) were monitored under ultraviolet irradiation in aqueous media. Prior to these experiments, mimicing heterogeneous photocatalysis reaction conditions, the open-circuit potentials (Eoc) of the prepared TiO2 films were monitored as a function of medium pH in the 3−11 range. A slope of −26 mV/pH was measured; this value is compared with previous studies of the pH dependence of Eoc and the TiO2 flat-band potential, Efb. Perhaps the most remarkable aspect of the presented (Eph−t) profiles concerns the very slow (minute regime) changes in the TiO2 film potential when the UV light is turned on. The extent of negative potential excursion (when the UV light is initially switched on) and the plateau potential attained (at times greater than ~5 min) are dependent on the nature of the metal ion “depolarizer”, the incident photon flux, and the presence of any co-additive in the 0.05 M Na2SO4 supporting electrolyte. When the light is turned off, the TiO2 film potential returns to its rest value (in the “dark”) in exponential fashion. A simple model, based on initial photocharging of the TiO2 film/solution interface and subsequent carrier trapping/detrapping events, is presented to account for the observed trends in the measured (Eph−t) profiles. Simulations based on this model afford chronopotentiometric profiles in good agreement with their experimental counterparts.

The cobalt hexacyanoferrate system, Mh%@mt;sys@%Co%@sx@%%@ital@%k%@rsf@%%@be@%A%@sxx@%%@mx@% [Fe^B(CN)6]l, (where M is an alkali metal cation, and the subscripts h, k, and l are stoichiometric coefficients, and A and B are the formal oxidation states of the Co and Fe metal sites in the structure) was shown to contain a rich series of compounds that are inter-linked through various redox processes (involving both electron and cation transfer) either in the dark or under the near-infrared (IR) activation. These processes were studied by a combined use of cyclic voltammetry, in situ IR spectroelectrochemistry (using both intensity or potential modulation), and ex situ X-ray photoelectron spectroscopy.

A diverse array of semiconductor-based composite materials have been prepared, characterized, and utilized in many applications ranging from photocatalysis, photovoltaic cells, photoelectrochromic displays, and light-emitting devices to sensors. The composite architectures (nanoarchitectures in many cases) are equally diverse. In this review, we highlight the advances that have been made and identify some of the gaps in our current knowledge of these materials. Size quantization effects and semiconductor quantum dots are also discussed.

The photoelectrochemical oxidation of aqueous sulfite on composite electrode films comprising titania particles as the dispersed component and nickel as the matrix (Ni−TiO2) is described. These composite films exhibit unusual photocurrent enhancement for sulfite oxidation relative to the corresponding neat TiO2 films containing no nickel. Both the morphology of the composite films and their surface chemical composition (Ni:Ti ratio) are shown to play a role in the photocurrent enhancement mechanism. Two potential domains for sulfite photooxidation separated by the onset of dark oxidation of sulfite by the nickel matrix itself are considered.

The galvanic reaction of metallic copper in Cr(VI)-laden aqueous solutions of varying pH was examined by in situu.v.–visible spectrophotometry, rotating disc electrode chronopotentiometry and cyclic voltammetry. The galvanic reaction in 0.2 M H2SO4solutions was pseudo first order in Cr(VI) concentration. Experiments with both magnetically stirred solutions and a copper mesh or a copper film in a rotating disc electrode configuration revealed the reaction to be diffusion-controlled with respect to Cr(VI) transport to the copper surface. Finally, cyclic voltammetry data in Cr(VI)-laden media of varying pH underline the important role of protons in the galvanic reaction.

Scanning electron microscopy was used to study the morphology of metal−TiO2 composite films prepared for photoelectrochemical applications. These films consisted of electrodeposited Ni, Cu, Ag, or In with TiO2 (Degussa P-25) particles occluded in them. In the case of Ni−TiO2 composites, co-clusters of nickel and TiO2 were observed superimposed on the “flat” regions of the film containing only nickel. This co-cluster formation facilitated efficient separation of photogenerated electron−hole pairs in the TiO2 component. On the other hand, the distribution of TiO2 on the indium film surface was such that electron−hole pair recombination resulted on photoexcitation of TiO2. Whereas Cu−TiO2 composite films exhibited n-type photoelectrochemical behavior in pH 7 sulfite medium, p-type activity resulted when the photovoltammetry experiment was repeated in 0.1 M NaOH. This behavior was attributed to Cu2O formed in situ in the Cu−TiO2 composite film.

Heterogeneous photocatalytic reactions in UV-irradiated TiO2 suspensions are comprised of two conjugate reaction pathways involving the photogenerated electrons and holes, respectively. The role of the hole reaction pathway in the dynamics of the photocatalytic reduction of Cr(VI) is a major focus of this study. It is shown that proton supply plays a crucial role in this reduction reaction. Thus, the Cr(VI) photoreduction kinetics switch from first order to zero order as the proton concentration is systematically increased in the aqueous suspensions. Ammonium ions are also shown to exert a dramatic accelerating influence on Cr(VI) reduction in media of initial pH 6. This new observation is rationalized by considering that these species act as hole scavengers. The consequent improvement in quantum yield combines with the facile proton generation upon NH4⁺ photooxidation, to result in the observed rate enhancement. Other interfacial aspects (i.e., adsorption) are also discussed.

A two-part study was undertaken to examine the feasibility of combining a batch-recirculated photoreactor with a hollow-fibre membrane based ultrafiltration unit for heterogeneous photocatalysis applications. Methylene Blue (MB) and titanium dioxide (Degussa, P-25) were used as the test substrate and photocatalyst respectively for this study. This paper, which forms Part I of this study, describes the influence of MB concentration, recirculation flow rate, TiO2 dose, solution volume in the reservoir and solution pH on the photocatalytic reaction rate. The dark adsorption of MB on the TiO2 particle surface was also analysed. The combination of the reservoir and the annular reaction vessel could be modelled as a continuous flow stirred tank in series with a plug-flow reactor. This model predicts that the reaction rate should increase with a decrease of solution volume in the reservoir, both in the low and high substrate concentration regimes of the Langmuir–Hinshelwood kinetics formalism. This prediction was borne out by the experimental data for the low concentration regime. Part II of this series will describe experiments and modelling of the UF unit, and the operation of the combined system, respectively.

A batch-recirculated photoreactor was combined with a hollow-fibre membrane ultrafiltration (UF) unit for heterogeneous photocatalysis applications. This paper focuses on the operation and modelling of the UF process component and on the performance of the integrated photoreactor–UF process assembly. Methylene blue and titanium dioxide (Degussa P-25) were used as the test pollutant and photocatalyst, respectively. The influence of cross-flow velocity, transmembrane pressure, and TiO2dose on the permeate flux through the hollow fibre membrane is described. These data are modelled on the basis of concentration polarization and gel layer formation at the membrane surface/feed slurry boundary. The operation of the integrated photoreactor–UF assembly over ten repeat cycles is described. Photocatalyst separation was complete as gauged by nephelometric turbidity measurements. However, a systematic degradation in the photocatalyst performance was noted with each repeat cycle. Dynamic laser light scattering data are consistent with agglomeration of the TiO2particles as a result of the UF process, and suggest a possible factor in the degraded photocatalytic activity. Possible solutions to this problem are finally presented.

Recent developments in the characterization of the thermophysical properties of various types of oil shales are reviewed. Changes in the thermal, mechanical and electrical properties of these technologically important materials are discussed, with temperature and organic content as the experimental variables. Structural models are presented to aid in predicting the variation of thermophysical parameters with organic content in the shale. Comparison of calculated results with experimental data are shown with thermal diffusivity as a representative parameter. Areas where further research of a fundamental nature would be of particular relevance are also highlighted in the review.

This article builds upon a companion review on electrochemical techniques [1] and discusses photocatalytic methods for the treatment and analysis of pollutants in water and air. Organic, inorganic and microbiological pollutants are considered. Areas wherein further research and development are needed are identified. Finally, perspectives on commercialization of this technology are presented.

Advances in electrochemical methods for pollutant remediation, recycling and sensing are reviewed. Additionally, applications of these methods in the drinking water industry, and for disinfection scenarios are discussed. Lastly, new electrode materials for environmental applications are described. In a companion review, photoelectrochemical methods will be discussed.

Abstract: Stabilization of the light-harvesting semiconductor electrode is a key factor in the design of a photoelectrochemical (PEC) system for solar energy conversion. Approaches to circumvent the problem of PEC corrosion of these electrodes involve four major categories of materials: (a) the electrode materials themselves; (b) protective coatings; (c) catalysts; and (d) electrolytes. Wide band-gap semiconductors are candidates for electrode materials; however, their use hinges on devising effective means of sensitizing their photoresponse to wavelengths comprising the solar spectrum. These and related aspects in the design of PEC systems are reviewed in this article. Devices both of the regenerative type as well as photoelectrolysis approaches are considered.

The pulsed plasma polymerization of tetramethyltin monomer was studied as a function of the radio frequency (rf) duty cycle employed, all other plasma variables being held constant. Progressive increases in the relative tin content of the plasma deposited films were observed with systematic decreases in the rf duty cycles employed during film formation. The variations in tin content of these films were documented by XPS, FT-IR, TEM, AFM, and electrochemical analyses. A particularly interesting aspect of this work is the microstructure of the films which reveals spherical tin particles of essentially uniform diameters (20−30 nm) independent of the duty cycle during deposition. The increasing metal content in these films with decreasing duty cycle corresponds to increased aggregation of these nanosized particles into progressively larger sized clusters. The results obtained are supportive of the use of the variable duty cycle pulsed plasma deposition technique as a new route to improved nanoscale film chemistry control in the synthesis of organometallic composite films.

Mixtures of aluminum chloride (AlCl3) with triethylammonium chloride (Et3NHCl), 1,6-ethyl lutidinium bromide (EtluBr), tert-butyl pyridinium bromide (BPBr), and dialkyl imidazolium chloride (R2ImCl), in certain molar ratios yielded ionic liquids at room temperature which were studied with respect to their applicability as electrolytes in photoelectrochemical (PEC) cells. Background voltammograms were obtained for these electrolytes on carbon and n-GaAs electrodes. The anodic stability limit was found to be enhanced on n-GaAs relative to carbon in all cases. The cathodic decomposition potential of the electrolyte showed a smaller positive shift on n-GaAs with the exception of the 3:1 AlCl3-BPBr electrolyte. The difference in electrolyte stability behavior on carbon and n-GaAs is interpreted in terms of carrier density effects. Cyclic voltammograms were compared on carbon in the various electrolytes for a model redox system comprising the ferrocene/ferricenium couple. The separation of the cathodic and anodic waves in all the cases was consistent with a quasi-reversible redox behavior—the most sluggish electron transfer being observed in the case of the 3:1 AlCl3-BpBr electrolyte. These results are compared with those obtained previously on the AlCl3-butyl pyridinium chloride (BPC) system. Capacitance-voltage measurements were made on n-GaAs electrodes in contact with the various electrolytes. Flatband-potentials (Vfb) were deduced from these data using Mott-Schottky plots. The relative positions of the n-GaAs band-edges and the redox levels were mapped on a common potential scale utilizing these data. The ferrocene/ferricenium redox level was placed negative of the conduction band-edge in n-GaAs in all the cases. The implications of this result for PEC applications and the role of specific ion adsorption of electrolyte species on the electrostatic aspects of the n-GaAs/molten salt electrolyte interface are discussed with the aid of energy band diagrams.

Irradiated TiO2suspensions in water were used to inactivate Escherichia coliand Hansenula polymorpha. Two types of batch reactors employing static and recirculating solutions were used in this study. Sonolysis using a 20 kHz ultrasonic unit was found to enhance the microorganism inactivation in all instances, although the enhancement was more modest for the batch recirculation reactor. These data are interpreted within the framework of four possible mechanisms. The mechanism based on sonolytic creation of ·OH appears to provide the most satisfactory explanation of the data trends. The present data also implicate ·OH as the dominant bactericidal agent in irradiated TiO2suspensions.

Manganese tricarbonyl complexes of fluorinated tris(pyrazolyl)borate ligands [HB(3,5-(CF3)2Pz)3]^- and [HB(3-(CF3)Pz)3]^- (where Pz = pyrazolyl) were synthesized by treating BrMn(CO)5 with [HB(3,5-(CF3)2Pz)3]Ag(THF) or [HB(3-(CF3)Pz)3]Na(THF). The reaction of [HB(3-(CF3)Pz)3]Na(THF) with copper(I) trifluoromethanesulfonate under CO afforded [HB(3-(CF3)Pz)3]CuCO. Compounds [HB(3,5-(CF3)2Pz)3]Mn(CO)3 (5), [HB(3-(CF3)Pz)3]Mn(CO)3 (6), and [HB(3-(CF3)Pz)3]CuCO (7) were characterized by ¹H NMR, ¹⁹F NMR, and IR spectroscopy and by X-ray crystallography. They have relatively high C−O stretching frequencies. However, the νCO values are much lower than that in free CO and the relative lowering is higher for manganese adducts. The CF3 substitution on the 5-position has a significant effect on the metal center. This is readily apparent from the infrared spectroscopic data. Theoretical calculations of the geometries of [tris(pyrazolyl)borato]manganese(I) and -copper(I) carbonyls are in excellent agreement with the experimental results. Increasing the degree of fluorination lengthens the metal−C and metal−N bonds and shortens the C−O distance. The metal−Pz bonding is essentially a pure σ-interaction. Cyclic voltammetry data for the copper complexes show high oxidation potentials for the fluorinated analogs. IR spectroscopic data of the [tris(pyrazolyl)borato]manganese and -copper carbonyls have also been compared to those of cyclopentadienyl analogs.

The photoelectrochemical behavior of chemically modified Ni/TiO2 nanocomposite films in aqueous 0.1 M NaNO3 electrolyte is described. Two types of such films were prepared, either starting with a Ni/TiO2 nanocomposite photoelectrode that was subsequently cycled in 0.01 M K3Fe(CN)6 + 0.1 M NaNO3 (type I) or with a Ni electrode derivatized in situ with nickel hexacyanoferrate (NHF) and TiO2 (type II). The photoactivity of both types of films was compared with the parent Ni/TiO2 film in 0.1 M NaNO3. Type I electrodes exhibited minimal photoactivity until potentials into the NHF II → III redox regime were accessed (>ca. 0.40 V). Thereafter, the anodic photocurrents were significantly higher than the parent Ni/TiO2 counterpart. Type II electrodes exhibited “bipolar” photoactivity, the switch from cathodic photo- to anodic photobehavior again occurring at potentials close to the NHF II → III redox location. These observations on type I and type II nanocomposite films stand in marked contrast to the usual photocurrent−voltage behavior of n-type semiconductor electrodes. The unusual photoeffects are interpreted within the framework of a model including charge transfer from the photoexcited TiO2 particles to the NHF redox sites within the nanocomposite film.

The chemical composition and electrochemical properties of thin films polymerized from ferrocene and vinylferrocene under pulsed plasma conditions are reported. Relatively large scale and systematic variations in composition and properties of these films are observed with progressive changes in the pulsed duty cycles employed during synthesis, all other plasma variables being held constant. Compositional changes in both percent Fe content and the ratio of Fe^II/Fe^III with variations in the duty cycles are clearly shown by X-ray photoelectron spectroscopy analysis of these films. Voltammetric studies of the plasma-polymerized films deposited on glassy carbon electrodes provide additional evidence for the variations in the electroactive iron content of the films with changes in the pulsed plasma duty cycles employed during synthesis. Overall, the results of this study provide further support for the utility of the pulsed plasma technique to provide controlled film composition during synthesis of organometallic films.

Thallium(I) is shown to be a sensitive probe of titania particle/aqueous solution interfaces in the dark and under ultraviolet (UV) illumination. We show that experimental conditions can be chosen such that photocatalytic reduction or oxidation of this probe is avoided. Thus, any changes in the measured solution levels of this probe can be simply attributed to corresponding variations in its adsorption tendency on the TiO2 particle surface. Data are presented on how this interfacial probe tracks modulations in the oxide surface charge induced either by variations in solution pH or by UV irradiation.