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Spherical Ti-MCM-41, synthetized by co-condensation method, presented very promising activity in catalytic and photocatalytic oxidation of diphenyl sulfide with H2O2 to obtain diphenyl sulfoxide and diphenyl sulfone. Mesoporous silica materials with various titanium content were analyzed with respect to chemical composition (inductively coupled plasma optical emission spectrometry), structure properties (X-ray diffraction), textural properties (low-temperature N2 adsorption–desorption), morphology (scanning electron microscopy), forms and aggregation introduced titanium species (diffuse reflectance spectroscopy, Raman spectroscopy), and surface acidity (NH3-TPD). Titanium introduced in the samples was present mainly in the form of highly dispersed species, presenting catalytic and photocatalytic activities in diphenyl sulfide oxidation with H2O2. Efficiency of the reaction increased with an increase in titanium loading in the samples and was significantly intensified under UV irradiation. The role of various Ti species in diphenyl sulfide oxidation was presented and discussed.

Preparation of highly active core-shell/hybrid materials based on up-converting particles combined with semiconductors for photocatalytic application usually requires sophisticated and multi-step synthesis procedures. We propose a new design of a highly efficient NIR-driven photocatalytic system composed of spatially separated thin films of upconverting NaYF 4 :Yb,Tm particles (UCPs), and TiO 2 . Several samples of UCPs were prepared in the form of thin films and suspensions, directly coated with a titania layer or mixed with P25. Photocatalytic and photoelectrochemical studies have shown that thin film samples achieved significantly higher photocatalytic activity than their suspended counterparts. Moreover, the sample consisting of spatially separated layers of UCPs and P25 presented a significant photocatalytic activity and generated the highest photocurrent intensity. Separating the photocatalyst and upconverter layers allows for an interchangeable photocatalytic system active in a wide range of light., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Recent development in photocatalysis is increasingly focused on transforming organic compounds toward producing fine chemicals. Simple, non-selective oxidation reactions (degradation of pollutants) and very demanding solar-to-chemical energy conversion processes (production of solar fuels) face severe economic limitations influenced by still low efficiency and insufficient stability of the systems. Synthesis of fine chemicals, including reductive and oxidative selective transformations, as well as C-C and C-N coupling reactions, can utilise the power of photocatalysis. Herein, we present the recent progress in photocatalytic systems designed to synthesise fine chemicals. In particular, we discuss the factors influencing the efficiency and selectivity of the organic transformations, dividing them into intrinsic (related to individual properties of photocatalysts) and extrinsic (originating from the reaction environment). A rational design of the photocatalytic systems, based on a deep understanding of these factors, opens new perspectives for applied photocatalysis., (© 2024 Wiley-VCH GmbH.)

A new two-step method for developing a nanocomposite of polypropylene (PP) decorated with photocatalytically active TiO 2 nanoparticles (nTiO 2 ) is proposed. This method involves the low-temperature plasma functionalization of polypropylene followed by the ultrasound-assisted anchoring of nTiO 2 . The nanoparticles, polymeric substrate, and resultant nanocomposite were thoroughly characterized using nanoparticle tracking analysis (NTA), microscopic observations (SEM, TEM, and EDX), spectroscopic investigations (XPS and FTIR), thermogravimetric analysis (TG/DTA), and water contact angle (WCA) measurements. The photocatalytic activity of the nanocomposites was evaluated through the degradation of methyl orange. The individual TiO 2 nanoparticles ranged from 2 to 6 nm in size. The oxygen plasma treatment of PP generated surface functional groups (mainly -OH and -C=O), transforming the surface from hydrophobic to hydrophilic, which facilitated the efficient deposition of nTiO 2 . Optimized plasma treatment and sonochemical deposition parameters resulted in an active photocatalytic nTiO 2 /PP system, degrading 80% of the methyl orange under UVA irradiation in 200 min. The proposed approach is considered versatile for the functionalization of polymeric materials with photoactive nanoparticles and, in a broader perspective, can be utilized for the fabrication of self-cleaning surfaces.

A lab-scale reactor with a fixed-bed hematite catalyst for the effective decomposition of H 2 O 2 and bacteria inactivation was designed. The bactericidal effect is the largest at a low initial bacterial count of 2·10 3  CFU/L, which is typical for natural surface waters. When using a 5 mM H 2 O 2 solution and a residence time of 104 min, the reduction in the number of E. coli bacteria is about 3.5-log. At a higher initial bacterial count of 1-2·10 4  CFU/L, a 5 mM H 2 O 2 solution reduces the bacteria number by about 4-log. The H 2 O 2 decomposition follows the log-linear kinetics of a first-order reaction while the bacterial inactivation does not. The kinetics of bacterial inactivation was described using the Weibull model in the modified form: log 10 (N 0 /N) = b · t n . The values of the non-linearity parameter n were found to be lower than 1, indicating that bacterial inactivation slows down over time. With increasing initial H 2 O 2 concentration, the rate parameter b increases while the non-linearity parameter n decreases. With increasing temperature, both parameters increase. The stability of the catalyst has been proved by XRD, FTIR, SEM, and ICP-OES. The concentration of iron leaching into water during disinfection is much lower than the limit declared by WHO for iron in drinking water. The results show that technical-grade hematite is a promising Fenton-like catalyst for water disinfection. The fixed-bed reactor can be the basis of the mobile installations for water purification in emergencies., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The conversion of CO 2 into valuable solar fuels via photocatalysis is a promising strategy for addressing energy shortages and environmental crises. Here, novel In 2 O 3 @Co 2 VO 4 hierarchical heterostructures are fabricated by in situ growing Co 2 VO 4 nanorods onto In 2 O 3 nanofibers. First-principle calculations and X-ray photoelectron spectroscopy (XPS) measurements reveal the electron transfer between In 2 O 3 and Co 2 VO 4 driven by the difference in work functions, thus creating an interfacial electric field and bending the bands at the interfaces. In this case, the photogenerated electrons in In 2 O 3 transport to Co 2 VO 4 and recombine with its holes, indicating the formation of In 2 O 3 @Co 2 VO 4 S-scheme heterojunctions and resulting in effective separation of charge carriers, as confirmed by in situ irradiation XPS. The unique S-scheme mechanism, along with the enhanced optical absorption and the lower Gibbs free energy change for the production of * CHO, significantly contributes to the efficient CO 2 photoreduction into CO and CH 4 in the absence of any molecule cocatalyst or scavenger. Density functional theory simulation and in situ diffuse reflectance infrared Fourier transform spectroscopy are employed to elucidate the reaction mechanism in detail., (© 2023 Wiley-VCH GmbH.)

The results of this work cover the influence of plasmonic (gold) and non-plasmonic (palladium) nanostructures on the photocatalytic activity and redox properties of titanium dioxide. Materials decorated with gold, palladium and both materials were examined using photoelectrochemical and spectroelectrochemical methods to establish the changes introduced by the modifications and the possibility of the influence of the plasmonic effect from gold on their activity. Additionally, the photocatalytic tests of hydroxyl radical generation and hydrogen evolution were performed to confirm the activity of modified materials in oxidation and reduction reactions. It turned out that in the observed system the catalytic properties of palladium determine mostly the activity of modified materials, and the surface plasmon resonance of gold does not affect the activity. Moreover, the influence of the nanostructures on the activity, besides the catalytic performance, is the same for plasmonic and non-plasmonic ones and results in a change in the redox properties of the semiconductor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This work aimed to revise the mechanism of photocatalytic activity of the TiO 2 /Ag 2 O system in photocatalytic water splitting accompanied by methanol photoreforming. The transformation of Ag 2 O into silver nanoparticles (AgNPs) during photocatalytic water splitting/methanol photoreforming was monitored using XRD, XPS, SEM, UV-vis, and DRS techniques. The impact of AgNPs, grown on TiO 2 , on its optoelectronic properties was analysed through inter alia spectroelectrochemical measurements. The photoreduced material exhibited a significantly shifted position of the TiO 2 conduction band edge. Surface photovoltage measurements revealed the lack of photoinduced exchange of electrons between TiO 2 and Ag 2 O, indicating the absence of an efficient p-n junction. Furthermore, the impact of chemical and structural changes in the photocatalytic system on the production of CO and CO 2 from methanol photoreforming was analysed. It was found that fully formed AgNPs exhibit improved efficiency in the production of H 2 , whereas the Ag 2 O phototransformation, resulting in the growth of AgNPs, promotes simultaneously ongoing photoreforming of methanol., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Metal oxide-organic hybrid semiconductors exhibit specific properties depending not only on their composition but also on the synthesis procedure, and particularly on the functionalization method, determining the interaction between the two components. Surface adsorption is the most common way to prepare organic-modified metal oxides. Here a simple sol-gel route is described as an alternative, finely controlled strategy to synthesize titanium oxide-based materials containing organic molecules coordinated to the metal. The effect of the molecular structure of the ligands on the surface properties of the hybrids is studied using three enediols able to form charge transfer complexes: catechol, dopamine, and ascorbic acid. For each system, the process conditions driving the transition from the sol to chemical, physical, or particulate gels are explored. The structural, optical, and photoelectrochemical characterization of the amorphous hybrid materials shows analogies and differences related to the organic component. In particular, electron paramagnetic resonance (EPR) spectroscopy at room temperature reveals the presence of organic radical species with different evolution and stability, and photocurrent measurements prove the effective photosensitization of TiO 2 in the visible range induced by interfacial ligand-to-metal charge transfer.

In this paper, we describe the role of anatase and rutile crystal phases on diphenyl sulphide (Ph 2 S) catalytic and photocatalytic oxidation. The highly selective and efficient synthesis of diphenyl sulfoxide (Ph 2 SO) and diphenyl sulfone (Ph 2 SO 2 ) at titanium dioxide was demonstrated. Ph 2 S oxidation in the presence of hydrogen peroxide at anatase-TiO 2 can take place both as a catalytic and photocatalytic reaction, while at rutile-TiO 2 only photocatalytic oxidation is possible. The reaction at anatase leads mainly to Ph 2 SO 2 , whereas, in the presence of rutile a complete conversion to Ph 2 SO is achieved after only 15 min (nearly 100% selectivity). Studies on the mechanistic details revealed a dual role of H 2 O 2 . It acts as a substrate in the reaction catalysed only by anatase, but it also plays a key role in alternative photocatalytic oxidation pathways. The presented study shows the applicability of photocatalysis in efficient and selective sulfoxide and sulfone production., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Photocatalytic artificial fixation of N 2 to NH 3 occurs over NaYF 4 :Yb,Tm (NYF) upconversion nanoparticles (NPs) decorated carbon nitride nanotubes with nitrogen vacancies (NYF/NV-CNNTs) in water under near-infrared (NIR) light irradiation. NYF NPs with a particle size of ca. 20 nm were uniformly distributed on the surface of NV-CNNTs. The NYF/NV-CNNTs with 15 wt % NYF exhibited the highest NH 3 production yield of 1.72 mmol L -1 g cat -1 , corresponding to an apparent quantum efficiency of 0.50% under NIR light illumination, and about three times higher the activity of the bare CNNTs under UV-filtered solar light. 15 N isotope-labeling NMR results confirm that the N source of ammonia originates from the photochemical N 2 reduction. The spectroelectrochemical measurements reveal that NVs can greatly facilitate the photogenerated electron transfer without energy loss, while the presence of NYF NPs shifts both the deep trap state and the edge of conduction band toward a lower potential. Moreover, NYF NPs endow the photocatalyst with a NIR light absorption via the fluorescence resonance energy transfer process, and NVs have the ability to enhance the active sites for a stronger adsorption of N 2 and decrease the surface quenching effect of NYF NPs, which thus can promote the energy migration within the heterojunctions. This work opens the way toward full solar spectrum photocatalysis for sustainable ammonia synthesis under aqueous system.

The diffuse reflectance spectroelectrochemistry (SE-DRS) and reversed double-beam photoacoustic spectroscopy (RDB-PAS) provide unique, complementary information on the density of electronic states (DOS) in the vicinity of the conduction band bottom. The measurements are performed under quite different conditions, representing the solid/liquid and solid/gas interfaces in SE-DRS and RDB-PAS, respectively. DOS profiles obtained from both types of measurements can be considered as unique "fingerprints" of the tested materials. The analysis of DOS profiles recorded for 16 different TiO 2 samples confirms that both methods similarly describe the shapes of DOS profiles around the conduction band edges. The states characterized by energy higher than VBT (valence-band top) + E g can be considered as electronic states within the conduction band. Recognition of the potential of the conduction band bottom allows one to classify the electronic states as deep or shallow electron traps or conduction band states, which play different roles in photocatalysis. The comparative analysis shows that both methods provide very useful information which can be used in understanding and predicting the photo(electro)catalytic reactivity of semiconductors.

Hydrogen production by photocatalytic water splitting is one of the most promising sustainable routes to store solar energy in the form of chemical bonds. To obtain significant H 2 evolution rates (HERs) a variety of defective TiO 2 catalysts were synthesized by means of procedures generally requiring highly energy-consuming treatments, e.g. hydrogenation. Even if a complete understanding of the relationship between defects, electronic structure and catalytic active sites is far from being achieved, the band gap narrowing and Ti 3+ -self-doping have been considered essential to date. In most reports a metal co-catalyst (commonly Pt) and a sacrificial electron donor (such as methanol) are used to improve HERs. Here we report the synthesis of TiO 2 /C bulk heterostructures, obtained from a hybrid TiO 2 -based gel by simple heat treatments at 400 °C under different atmospheres. The electronic structure and properties of the grey or black gel-derived powders are deeply inspected by a combination of classical and less conventional techniques, in order to identify the origin of their photoresponsivity. The defective sites of these heterostructures, namely oxygen vacancies, graphitic carbon and unpaired electrons localized on the C matrix, result in a remarkable visible light activity in spite of the lack of band gap narrowing or Ti 3+ -self doping. The materials provide HER values ranging from about 0.15 to 0.40 mmol h -1 g cat -1 , under both UV- and visible-light irradiation, employing glycerol as sacrificial agent and without any co-catalyst., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Samples of TiO 2 (P25) doped with zinc, tin, and vanadium, thermally treated at 550 °C for 6 h, were tested as catalysts and photocatalysts for the oxidation of diphenyl sulphide to diphenyl sulfoxide and sulfone, using hydrogen peroxide as an oxidation agent. Thermal treatment of pure TiO 2 and its vanadium-doped forms resulted in a decrease of anatase and an increase of rutile content. The opposite effect was observed for TiO 2 doped with zinc or tin, where thermal treatment resulted in the rutile to anatase phase transition. The role of V, Zn, and Sn admixtures as TiO 2 phase-composition controllers was postulated. The catalytic and photocatalytic activity was found to be influenced more by the rutile and anatase contents of the samples than the presence of admixtures. The rutile-containing samples, TiO 2 and V-TiO 2 , presented much better activity in the catalytic oxidation of diphenyl sulphide compared with the catalysts that only contained the anatase phase, Sn-TiO 2 and Zn-TiO 2 . The reaction efficiency was significantly improved under UV radiation. In this case, the best photocatalytic activity was found for calcined TiO 2 , containing both anatase and rutile components. An increase in rutile content, observed in the vanadium-doped TiO 2 , decreased the efficiency of the photocatalytic diphenyl sulphide oxidation. Thus, the presence of both anatase and rutile phases, with their favourable contributions, typical for P25, is necessary for the effective oxidation of Ph 2 S to Ph 2 SO. Moreover, it was shown that for the second oxidation stage, Ph 2 SO to Ph 2 SO 2 , the presence of the rutile phase is very important., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

DFT/D  +  U and density functional based tight binding (DFTB) molecular modeling was used to investigate the role of the structural, electronic and optical properties of reduced graphene oxide surface (r-GO), hybridized with hydrated TiO 2 moieties of various size, ranging from small molecular Ti 2 O 4 clusters into extended Ti 43 O 86 rutile type nanocrystals of ~5 nm diameter. The calculated adhesion energies, varying from  -5.048 eV (r-GO|Ti 2 O 4 ), -12.159 eV (r-GO|Ti 5 O 10 ), -18.499 eV (r-GO|Ti 15 O 30 ) to  -42.484 eV (r-GO|Ti 43 O 86 ), indicate high stability of these composites. It was shown that electronic interactions at the r-GO|(1 1 0)TiO 2 interface give rise to net charge flow from the r-GO substrate towards the TiO 2 moieties, analyzed in terms of the partial charge density 3D plots and an interfacial dipole moment formation. The DOS structure of the composites was calculated by means of the time dependent DFTB approach, and the position and composition of the VB and CB edges, along with the presence of weak mid-gap 2p  C states originating from the intact graphene-like patches in the r-GO substrate were discussed in detail in the context of conceivable photocatalytic activity of the composites. The constructed band alignment diagram implies formation of the staggered type II scheme, with the electric field offset that is sensitive to the titania cluster size. In the case of the nano-reticular TiO 2 , where only a fraction of the Ti atoms is engaged in the Ti-O-C linkers formation, recombination of the photogenerated charges is inhibited owing to favorable spatial separation effect. For small molecular TiO 2 clusters with all Ti cations anchored to the r-GO layer fast cross-relaxation quenches the beneficial interfacial charge separation effect, since the strong hybridization of the oxygen and carbon states provides a convenient pathway for the efficient electronic coupling between the CB edge states of r-GO and the VB edge states of the TiO 2 moieties. A phenomenological model of the molecular r-GO|Ti 2 O 4 and the reticular r-GO|Ti 43 O 86 composites was constructed in account for different photocatalytic behavior of both junctions.

Particulate matter (PM) can strongly affect redox biochemistry and therefore induce the response of the immune system and aggravate the course of autoimmune diseases. Nanoparticles containing transition metal compounds possessing semiconductor properties (TiO 2 , ZnO) may act as photocatalysts and accelerate the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this study, the NIST standard reference material, SRM 1648a, has been analyzed in terms of this consideration. Organic compounds present in SRM 1648a were removed by cold oxygen plasma treatment. Samples of SRM 1648a with removed organic content (<2% of organic carbon, <1% of nitrogen) were obtained within 2 h of this treatment. The treatment did not affect the morphology of the powder. The reference material and PM2.5 collected in Kraków are composed of smaller particles and nanoparticles forming aggregates. The efficiency of (photo)generation of hydroxyl radicals and singlet oxygen was compared for original and organics-free samples. The analyzed samples showed the highest activity towards ROS generation when exposed to UV-vis-NIR light, moderate under UV irradiation, and the lowest in dark. Data collected in the present study suggest that the organic fraction is mostly responsible for singlet oxygen generation, as almost twice higher efficiency of 1 O 2 generation was observed for the original NIST sample compared to the material without the organic fraction. However, particulate matter collected in Kraków was found to have a five times higher activity in singlet oxygen generation (compared for original NIST and Kraków dust samples)., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The effect of Zn-doping in CoFe 2 O 4 nanoparticles (NPs) through chemical co-precipitation route was investigated in term of structural, optical, and magnetic properties. Both XRD and FTIR analyses confirm the formation of cubic spinel phase, where the crystallite size changes with Zn content from 46 to 77 nm. The Scherrer method, Williamson-Hall (W-H) analysis, and size-strain plot method (SSPM) were used to study of crystallite sizes. The TEM results were in good agreement with the results of the SSP method. SEM observations reveal agglomeration of fine spherical-like particles. The optical band gap energy determined from diffuse reflectance spectroscopy (DRS) varies increases from 1.17 to 1.3 eV. Magnetization field loops reveal a ferromagnetic behavior with lower hysteresis loop for higher Zn content. The magnetic properties are remarkably influenced with Zn doping; saturation magnetization (M s ) increases then decreases while both coercivity (H C ) and remanent magnetization (M r ) decrease continuously, which was associated with preferential site occupancy and the change in particle size.

Background: The main goal of periodontal therapy is to eliminate the infection spreading in periodontium. Antimicrobial photodynamic therapy may be applied in order to eradicate pathogens remaining in periodontal tissues after conventional mechanical debridement, to improve the treatment results. The aim of this in vitro study was to evaluate the susceptibility of selected key periopathogens to toluidine blue O-mediated photodynamic inactivation and the influence of photosensitizer's concentration and light dose on the effectiveness of this process., Methods: Following bacterial strains were used in the experiments: Porphyromonas gingivalis ATCC 33277, Aggregatibacter actinomyctemecomitans ATCC 33384, Fusobacterium nucleatum ATCC 10953. Toluidine blue O (TBO) was used in concentration ranging from 0.004 to 0.5mg/mL. Irradiation was performed by a non-laser red light source., Results: Complete eradication of P. gingivalis was obtained upon the application of TBO in the concentration of 0.1mg/mL and the highest light dose. A, actinomycetemcomitans was, in turn, not susceptible to photodynamic inactivation regardless of the dosimetric parameters applied. High viability reductions were also obtained for F. nucleatum, however no complete eradication. The effectiveness of photodynamic inactivation of susceptible periopathogens was dependent on the light dose and photosensitizer's concentration., Conclusions: Periopathogens differ in terms of their susceptibility to photodynamic inactivation. Antimicrobial PDT may be valuable in the treatment of those cases of periodontal disease, in which P. gingivalis is a dominating pathogen. Microbiological examination prior to clinical application of aPDT may be recommended., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Submicron particulate matter containing particles with an aerodynamic diameter ≤1 μm (PM1) are not monitored continuously by Environmental Protection Agencies around the World and are seldom studied. Numerous studies have indicated that people exposed to ultrafine (≤100 nm), submicron and fine particulate matter containing particles with an aerodynamic diameter ≤2.5 μm (PM2.5), can suffer from respiratory track diseases, cardiovascular, immunological or heart diseases and others. Inorganic pollutants containing redox active transition metals and small gaseous molecules, are involved in the generation of reactive oxygen and reactive nitrogen species. Inhalation of this kind of particles can affect immune-toxicity. Environmental pollution may aggravate the course of autoimmune diseases, in particular influence the mechanisms of the autoimmune system. Important factors that influence the toxicity of particulate matter, are particle size distribution, composition and concentration. This report deals with the composition of PM1 and PM2.5 fractions collected in Krakow, Poland. In spring 2015, the mean concentrations of PM1 and PM2.5 were 19 ± 14 and 27 ± 19 μg/m 3 , respectively. The PM2.5 fraction contained approximately 70 ± 17% of submicron particulate matter. In spring 2016, the mean concentrations of PM1 and PM2.5 were 12 ± 5 and 22 ± 12 μg/m 3 , respectively. The PM2.5 fraction contained approximately 60 ± 15% of submicron particulate matter. The concentrations of the elements Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr and Pb in both fractions were determined by X-ray fluorescence spectrometry. Most of the analyzed metals had higher concentrations in the fine fraction than in the submicron one. Concentrations of V and As were below the detection limit in both fractions, whereas concentrations of Mn and Ca were below the detection limits in the PM1 fraction. The results are discussed in terms of the consequences they may have on the APARIC project presently underway in Krakow., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Bare and photosensitized copper iodides were tested in photocatalysed degradation of an organic dye (Acid Red 1) and inactivation of fungi (Saccharomyces cerevisiae). CuI, with the band gap energy slightly lower than that of TiO 2 , appeared to be highly efficient in these processes. Sensitization of copper iodide was achieved by surface modification with [Cu(SCN) 2 (phen) 2 ]. The photosensitization mechanism encompasses a metal to metal charge transfer, Cu I → Cu II . The applied photosensitizer binds to CuI through thiocyanate ligands resulting in the formation of an active Cu II /Cu I hybrid photocatalyst ([Cu II (SCN) 2 (phen) 2 ]@Cu I I). Its absorption edge is red shifted towards a lower energy when compared with bare CuI, resulting in enhanced visible light induced photocatalytic activity. The studied materials appeared to be photoactive in current generation, degradation of organic compounds and inactivation of fungi.

A p-type semiconductor, CuI, has been synthesized, characterized, and tested as a photocatalyst for CO 2 reduction under UV/Vis irradiation in presence of isopropanol as a hole scavenger. Formation of CO, CH 4 , and/or HCOOH was observed. The photocatalytic activity of CuI was attributed to the very low potential of the conduction band edge (i.e., -2.28 V vs. NHE). Photocurrents generated by the studied material confirm a high efficiency of the photoinduced interfacial electrontransfer processes. Our studies show that p-type semiconductors may be effective photocatalysts for CO 2 reduction, even better than extensively studied n-type titanium dioxide, owing to the low potential of the conduction band edge., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Coordination compounds with a tin center surrounded by both organic and inorganic ligands ([SnI4{(C6H5)3PO}2], [SnI4{(C6H5)2SO}2], and [SnI4(C5H5NO)2]) acting as molecular semiconductors are in the spotlight of this article. This is a new class of hybrid semiconducting materials where optoelectronic properties of inorganic core (SnI4) were tuned by organic ligands. The valence band is located at the inorganic portion of the molecule while the conduction band is made of carbon-based orbitals. This suggests the great importance of hydrogen bonds where iodine atoms play the role of an acceptor. Weak intermolecular interactions between iodine atoms and aromatic rings are essential in a band structure formation. These materials form orange-red crystals soluble in most of organic solvents. Their semiconducting properties are addressed experimentally via photovoltage measurements, as well as theoretically, using DFT and semiempirical approaches.

Antimicrobial photodynamic therapy (aPDT) involves pathogens' destruction caused by means of toxic Reactive Oxygen Species (ROS) that are generated upon the interaction of a photoactivatable substance (photosensitizer), light of the appropriate wavelength and oxygen. Among many clinical applications, it is also used as a supplementary method of treatment of periodontal disease. Many in vitro studies confirmed, that a major periopathogenic bacterium, Porphyromonas gingivalis is susceptible to this method. Several animal model studies pointed, that even a single application of aPDT adjunctive to conventional scaling and root planning (SRP) promotes better tissue healing, reduces the inflammatory infiltrate and bone loss. The outcomes of clinical trials are, however, inconsistent. Although in several the superiority of combined treatment protocol (SRP+aPDT) over the conventional (SRP alone) was reported, it was not confirmed in other trials. Nonetheless, the reduction of bleeding indices favoring the combined therapy was observed in the majority of the studies. It indicates, that aPDT has an influence on the extent of inflammation and further studies are needed to establish an optimal protocol of treatment combining mechanical debridement with photochemotherapy in order to obtain good treatment outcomes in our patients., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Commercially available polypropylene foil was pretreated with a low temperature oxygen plasma and covered with a thin film of nanocrystalline titanium dioxide by dip coating. The films were then photosensitized by titanium(IV) surface charge transfer complexes formed by impregnation with catechol. The photoactivity of the coatings up to 460 nm was confirmed by photoelectrochemical measurements. The photoinactivation of Escherichia coli and Staphylococcus aureus was evaluated by a glass adhesion test based on ISO 27447:2009(E) in the presence of visible light. The coating showed good antimicrobial activity induced by light from a light-emitting diode (405 nm), in particular towards E. coli ATCC 25922 strain. Adaptation of ISO 27447:2009(E) to assess bacterial photoinactivation by photocatalytic coatings will allow this procedure to be applied for the comparison of photoactivity under a range of irradiation conditions.

The conversion of CO2 into high energy products (fuels) and the direct carboxylation of C-H bonds require a high energy input. Energy cannot be derived from fossil carbon, in this case. Solar energy can be used instead, with a low environmental impact and good profit. We have studied the use of white light or solar energy in the photoreduction of CO2 and in photocarboxylation reactions, using different semiconductors modified at their surface. Two examples of reduction of CO2 to methanol and CO will be shortly discussed, and two cases of carboxylation of organic substrates. The case of carboxylation of 2,3-dihydrofuran will be discussed in detail.

A hybrid enzymatic/photocatalytic approach for the conversion of CO2 into methanol is described. For the approach discussed here, the production of one mol of CH3OH from CO2 requires three enzymes and the consumption of three mol of NADH. Regeneration of the cofactor NADH from NAD(+) was achieved by using visible-light-active, heterogeneous, TiO2-based photocatalysts. The efficiency of the regeneration process is enhanced by using a Rh(III)-complex for facilitating the electron and hydride transfer from the H-donor (water or a water-glycerol solution) to NAD(+). This resulted in the production of 100 to 1000 mol of CH3OH from one mol of NADH, providing the possibility for practical application.

Attempts to increase the stability of photocatalytically active nanodispersions of titanium dioxide over a wide range of pH (3-10) were undertaken. Polyethylene glycols (PEGs) with different molecular weights and polyoxyethylenesorbitan monooleate (Tween® 80) were tested as stabilizing agents of TiO2 nanoparticles. The results of DLS measurements proved the stabilizing effect of Tween® 80 while the systems involving PEGs, independently of the polymer concentration, showed a tendency to form aggregates in neutral solutions. The colloids stabilized with Tween® 80 were photosensitized with 2,3-naphthalenediol (nd) or 2-hydroxy-3-naphthoic acid (hn) or catechol (cat). The photocatalytic activity of such colloids has been assessed in an azure B degradation reaction using both UV and visible light. The nd@TiO2 + Tween colloid appeared particularly photoactive upon visible light irradiation. Moreover, the comparison of activities of nd@TiO2 + Tween and TiO2 + Tween revealed a significantly better performance of the former nanodispersion, independently of the irradiation conditions (UV or visible light). This effect has been explained by different structures of micelles formed in the case of TiO2 and nd@TiO2 stabilized with Tween® 80.

Several techniques can be applied to characterize redox properties of wide bandgap semiconductors, however some of them are of limited use. In this paper we propose a new modification of the old spectroelectrochemical method developed two decades ago. A procedure based on measurements of the reflectance changes as a function of potential applied to the electrode coated with the studied material appears to be a very convenient tool for characterizing redox properties of semiconductors, forming either transparent or opaque films at a platinum electrode. A discussion on the measured redox parameters of semiconductor films concludes with a definition of a new term, the absorption onset potential of the material.

The generation of singlet oxygen in aqueous colloids of nanocrystalline TiO2 (anatase) modified by organic chelating ligands forming surface Ti(IV) complexes was studied. Detailed studies revealed a plausible and to date unappreciated influence of near-infrared irradiation on singlet oxygen generation at the surface of TiO2. To detect (1)O2, direct and indirect methods have been applied: a photon counting technique enabling time-resolved measurements of (1)O2 phosphorescence, and fluorescence measurements of a product of singlet oxygen interaction with Singlet Oxygen Sensor Green (SOSG). Both methods proved the generation of (1)O2. Nanocrystalline TiO2 modified with salicylic acid appeared to be the most efficient photosensitizer among the tested materials. The measured quantum yield reached the value of 0.012 upon irradiation at 355 nm, while unmodified TiO2 colloids appeared to be substantially less efficient generators of singlet oxygen with the corresponding quantum yield of ca. 0.003. A photocatalytic degradation of 4-chlorophenol, proceeding through oxidation by OH˙, was also monitored. The influence of irradiation conditions (UV, vis, NIR or any combination of these spectral ranges) on the generation of both singlet oxygen and hydroxyl radicals has been tested and discussed. Simultaneous irradiation with visible and NIR light did not accelerate OH˙ formation; however, for TiO2 modified with catechol it influenced (1)O2 generation. Singlet oxygen is presumably formed according to Nosaka's mechanism comprising O2˙(-) oxidation with a strong oxidant (hole, an oxidized ligand); however, the energy transfer from NIR-excited titanium(iii) centers (trapped electrons) plays also a plausible role.

The photoelectrochemical photocurrent switching (PEPS) effect, in the beginning regarded as a scientific curiosity, has become a field of extensive study for numerous research groups all over the world. This unique effect can be utilized for nanoscale switching and information processing, furthermore, is can serve as an interface between molecular information processing and macroscopic electronics. This review summarizes recent efforts in understanding photocurrent switching effects and their application for the construction of nanoscale switches and logic devices. Furthermore, some future prospects concerning the development of electronic/optoelectronic devices based on photoactive semiconducting hybrid materials are presented.

Phototoxicity of titanium dioxide modified with platinum(IV)-chloride complexes, [TiO2/PtCl4], irradiated with visible light was tested on murine macrophage cell line (RAW 264.7) in vitro. Presence of antioxidants such as alpha-tocopherol or beta-carotene during photodynamic treatment significantly increased cells viability. Our results indicate that observed cell death induced by [TiO2/PtCl4] was due to photogeneration of reactive species.

The visible light-induced phototoxicity of titanium dioxide modified with platinum(IV) chloride complexes, [TiO2/PtCl4], was tested. In vitro experiments with the mouse melanoma cells (S-91) have demonstrated phototoxicity of the [TiO2/PtCl4] material. Detection of efficiently generated various reactive oxygen species (.OH, O2. -, H2O2, 1O2) and also reactive chlorine species has proven the photodynamic activity of the tested material, induced by visible light (lambda>455 nm). The cellular death (recognized as a necrosis) is a result of the cell membrane peroxidation.

Visible light induced photocatalytic inactivation of bacteria (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis) and fungi (Candida albicans, Aspergillus niger) was tested. Carbon-doped titanium dioxide and TiO2 modified with platinum(IV) chloride complexes were used as suspension or immobilised at the surface of plastic plates. A biocidal effect was observed under visible light irradiation in the case of E. coli in the presence of both photocatalysts. The platinum(IV) modified titania exhibited a higher inactivation effect, also in the absence of light. The mechanism of visible light induced photoinactivation is briefly discussed. The observed detrimental effect of photocatalysts on various microorganism groups decreases in the order: E. coli > S. aureus approximately E. faecalis>>C. albicans approximately A. niger. This sequence results most probably from differences in cell wall or cell membrane structures in these microorganisms and is not related to the ability of catalase production.

Selected iron(II) complexes (ferrocene, ferrocenylboronic acid, hexacyanoferrate(II)) have been used as photosensitizers of titanium dioxide. Various types of electronic interactions between the surface complex and the semiconducting support are reflected in different yields of photocurrent generated upon visible-light irradiation and different efficiencies of the photosensitization effect. The studied systems, showing the photocurrent switching upon changes of electrode potential and energy of photons (the PEPS effect), are good models of simple photoelectrochemical logic devices. The mechanism of photosensitization and photocurrent switching is discussed with respect to the type of surface-complex-support interaction. Quantum-mechanical calculations support the proposed mechanisms.

Substitution of surface -OH groups of TiO2 may influence competition between photoinduced energy and electron-transfer processes and lead to improved singlet oxygen generation. In contrast to neat TiO2, surface modified titanium dioxide can photocatalyze degradation of a very stable substance, cyanuric acid. Presented results are in contradiction to usually accepted hypothesis of the mechanism of cyanuric acid photodegradation in the presence of fluorinated TiO2 (F-TiO2) in which "bulk" hydroxyl radicals play a key role. It seems plausible that the difference of activity observed for TiO2 and F-TiO2 is not related to various types of generated hydroxyl radicals, but rather to competition between electron-transfer processes (formation of radicals) and energy-transfer processes (formation of singlet oxygen).

Photosensitization of nanocrystalline titanium dioxide materials has been achieved by chemisorption of the pentacyanothiamineferrate(II) complex, which offers a relatively high redox potential that determines the photoelectrochemical properties of the photosensitized TiO(2). The adsorbed pentacyanoferrate complex binds to TiO(2) through the cyanide bridge and forms a new surface complex characterized by a metal-to-metal charge-transfer transition (MMCT) (Fe(II)-->Ti(IV)). The photosensitization can be observed only at low potentials at which Fe(II) moieties are present. Photocurrent switching between anodic and cathodic can be induced by varying either the photoelectrode potential or the wavelength of the incident light. Simple molecular modeling-together with spectroscopic and electrochemical measurements-allows the elucidation of the mechanism of the observed photoelectrochemical behavior.

Switching of photocurrent direction in semiconducting systems upon changes of the electrode potential or incident light wavelength was realized by a series of photoelectrodes covered with titania modified with pentacyanoferrate complexes, [Fe(CN)(5)L](n)(-) (L = NH(3), thiodiethanol, thiodipropanol). These materials were characterized by optical spectroscopy and electrochemistry. The structure of the surface complexes was modeled using simple quantum-chemical models. The electrodes described in this paper enable control of the photocurrent direction by two stimuli: Changing the wavelength or the photoelectrode potential easily switches the direction of photocurrent. The materials are different from those of similar characteristics studied by other authors: They are not composites comprising of two types of semiconductors but rather engineered uniform materials. The photocurrent switching phenomenon is an intrinsic feature resulting from a specific electronic structure of the surface-modified semiconductor.

Photoelectrodes made of nanocrystalline titanium dioxide modified with various pentacyanoferrates exhibit unique photoelectrochemical properties; photocurrent direction can be switched from anodic to cathodic and vice versa upon changes in photoelectrode potential and incident light wavelength (PhotoElectrochemical Photocurrent Switching, PEPS effect). At certain potentials, anodic photocurrent generated upon UV irradiation has the same intensity as the cathodic photocurrent generated upon visible irradiation. Under these conditions, simultaneous irradiation with UV and visible light results in compensation of anodic and cathodic photocurrents, and zero net photocurrent is observed. This process can be used for construction of unique light-driven chemical logic gates.

The band edge positions of a nitrogen-fixing nanostructured semiconductor thin film are determined both in the dark through spectroelectrochemistry and under irradiation by photovoltage measurements. Both methods afford the same result indicating that the film in addition to the dinitrogen-fixing phase Fe2Ti2O7 also contains titanium dioxide. Thus, both methods enable the analysis of a mixture of semiconducting thin films. For pH 7, values of -0.4 and +1.6 V were estimated for the conduction and valence band edge of the iron titanate film, respectively. A 3-fold photocurrent increase by methanol was observed only when the film was calcined at 600 degrees C but not below or above this temperature; the films calcined at temperatures other than 600 degrees C were also inactive in the photoreduction of dinitrogen. For a matter of comparison, an iron(III) oxide film was characterized analogously.