Search

The fluids near the solid substrate display different properties compared to the bulk fluids owing to the asymmetric interaction between the fluid and substrate; however, to the best of our knowledge, no work has been conducted to determine the interfacial properties of fluids experimentally. In this work, we combined a pycnometer with experimental measurements and data processing to determine the standard thermodynamic properties of interfacial fluids for the first time. In the study, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Hmim][NTf2]) and titanium dioxide (P25) were chosen as the probes to prove the concept. It was found that, with the combination of the Gay-Lussac pycnometer and the colligative law, together with selecting a suitable solvent, it is possible and reliable to determine the standard molar volume of the immobilized [Hmim][NTf2]. Compared to the bulk phase, the molar volumes of [Hmim][NTf2] on the P25 surface reduce by 20.8%-23.7% at temperatures from 293.15 to 323.15 K, and the reduction degrees decrease with increasing temperatures. The newly determined standard thermodynamic data was used to obtain the model parameters of hybrid electrolyte perturbed-chain statistical associating fluid theory density functional theory (ePC-SAFT-DFT), and further predictions of the density of interfacial ionic liquids with different film thicknesses were proved to be reliable in comparison with the experiment results. [ABSTRACT FROM AUTHOR]

Understanding the role of oxygen vacancies in the phase transformation of metal oxide nanomaterials is fundamental to design more efficient opto-electronic devices for a variety of applications, including sensing, spintronics, photocatalysis, and photo-electrochemistry. However, the structural mechanisms behind the phase transformation in reducible oxides remain poorly described. Here, we compare P25 and black TiO2 during the thermal anatase-to-rutile transformation using in situ synchrotron powder diffraction. The precise measurement of the phase fractions, unit cell parameters, and Ti-O bond sheds light on the phase transformation dynamics. Notably, we observe distinct temperature-dependent shifts in the relative phase fractions of anatase and rutile in both materials highlighting the role of the oxygen vacancy in promoting the phase transformation. We employ bond valence concepts for structural modeling, revealing unique trends in temperature evolution of Ti-O distances of black rutile, confirming that this TiO2 phase is preferentially reduced over anatase. These findings not only enhance our understanding of phase transitions in TiO2 but also open new ways for the design of advanced photocatalytic materials through targeted phase control. [ABSTRACT FROM AUTHOR]

This article reported an extremely easy method of optical radiation-assisted thermal excitation to dramatically increase photocatalytic hydrogen generation ability of water splitting with P25 as a model compound. This method compensated for the time waste, high cost and operational complexity of traditional catalytic material modification methods, and largely improved the photocatalytic hydrogen production ability of photocatalytic materials. The hydrogen generation rates at room temperature is 1090 μmol/g/h. At 50 °C, the rate increase to 10670 μmol/g/h. The quantum rates at room temperature and 50 °C are 6.5 and 63.3, respectively. It is clear that appropriate low-temperature heating could largely accelerate the hydrogen generation rate of P25. This work presents the detailed mechanism how this method largely enhances photocatalytic hydrogen generation of P25 as well as the laws. The new method offers some evidences and reference for research on how the photothermic synergistic action facilitates the photocatalytic hydrogen generation of catalytic materials. • Ultra-high photocatalytic activity. • Low-temperature-assisted photocatalysis. • Photothermic synergistic action. [ABSTRACT FROM AUTHOR]

Jana Bacova,1 Petr Knotek,2 Katerina Kopecka,2 Ludek Hromadko,3 Jan Capek,1 Pavlina Nyvltova,1 Lenka Bruckova,1 Ladislava Schröterova,4 Blanka Sestakova,4 Jiri Palarcik,5 Martin Motola,3 Dana Cizkova,6 Ales Bezrouk,7 Jiri Handl,1 Zdenek Fiala,8 Emil Rudolf,4 Zuzana Bilkova,1 Jan M Macak,3,9 Tomas Rousar1 1Department of Biological and Biochemical Sciences, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic; 2Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic; 3Center of Materials and Nanotechnologies, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic; 4Department of Medical Biology and Genetics, Faculty of Medicine in Hradec Kralove, Charles University, Hradec Kralove, Czech Republic; 5Institute of Environmental and Chemical Engineering, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic; 6Department of Histology and Embryology, Faculty of Medicine in Hradec Kralove, Charles University, Hradec Kralove, Czech Republic; 7Department of Medical Biophysics, Faculty of Medicine in Hradec Kralove, Charles University, Hradec Kralove, Czech Republic; 8Department of Preventive Medicine, Faculty of Medicine in Hradec Kralove, Charles University, Hradec Kralove, Czech Republic; 9Central European Institute of Technology, Brno University of Technology, Brno, Czech RepublicCorrespondence: Tomas Rousar, Department of Biological and Biochemical Sciences, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Tel +420 466 037 707, Fax +420 466 036 361, Email Tomas.Rousar@upce.czPurpose: Titanium dioxide nanoparticles, 25 nm in size of crystallites (TiO2 P25), are among the most produced nanomaterials worldwide. The broad use of TiO2 P25 in material science has implied a request to evaluate their biological effects, especially in the lungs. Hence, the pulmonary A549 cell line has been used to estimate the effects of TiO2 P25. However, the reports have provided dissimilar results on caused toxicity. Surprisingly, the physicochemical factors influencing TiO2 P25 action in biological models have not been evaluated in most reports. Thus, the objective of the present study is to characterize the preparation of TiO2 P25 for biological testing in A549 cells and to evaluate their biological effects.Methods: We determined the size and crystallinity of TiO2 P25. We used four techniques for TiO2 P25 dispersion. We estimated the colloid stability of TiO2 P25 in distilled water, isotonic NaCl solution, and cell culture medium. We applied the optimal dispersion conditions for testing the biological effects of TiO2 P25 (0– 100 μg.mL− 1) in A549 cells using biochemical assays (dehydrogenase activity, glutathione levels) and microscopy.Results: We found that the use of fetal bovine serum in culture medium is essential to maintain sufficient colloid stability of dispersed TiO2 P25. Under these conditions, TiO2 P25 were unable to induce a significant impairment of A549 cells according to the results of biochemical and microscopy evaluations. When the defined parameters for the use of TiO2 P25 in A549 cells were met, similar results on the biological effects of TiO2 P25 were obtained in two independent cell laboratories.Conclusion: We optimized the experimental conditions of TiO2 P25 preparation for toxicity testing in A549 cells. The results presented here on TiO2 P25-induced cellular effects are reproducible. Therefore, our results can be helpful for other researchers using TiO2 P25 as a reference material.Keywords: titanium dioxide, nanoparticles, P25, nanotoxicity, A549 cells, dispersion

Annealing treatment of P25 with PEG leads to not only the construction of visible light reponsive hetrojunction but also the formation of oxygen vacancy (Vo). [Display omitted] • Visible light responsive P25 heterojunction is constructed via annealing treatment with PEG. • The optimal mass ratio of P25 to PEG is proved to be 5:1. • Annealing treatment introduces oxygen vacancy into P25 favoring the separation of photogenerated charge carriers. As the most widely used titanium dioxide (TiO 2) photocatalysts, P25 is not able to absorb the visible light due to its limited light response range. In this work, visible light responsive P25 was prepared via the annealing treatment at 300 ℃ under anaerobic conditions with polyethylene glycol (PEG) as the additive. The annealing treatment with PEG not only endows P25 the visible light responsive property but also creates oxygen vacancy (Vo) favoring the separation of charge carriers, which both contributes to its efficient photocatalytic activity. Our work offers a facile approach for the construction of visible light responsive heterojunction via the annealing treatment with organic additive. [ABSTRACT FROM AUTHOR]

This work presents and discusses TiO 2 microspheres synthesized by ultrasonic spray pyrolysis. A simple setup allowed for the continuous production of TiO 2 nanocrystals. During the process, the particles experienced a short residence time (ca. 40 s) at the set temperature (700 °C), promoting phase stability and limited particle coarsening. As a result, porous anatase TiO 2 microspheres with crystallite size ∼8 nm and specific surface area ∼27 m2 g-1 were produced as soft spherical agglomerates of ∼0.6 μm. Samples were analyzed using X-ray diffraction, BET specific surface area, SEM, TEM, XPS, and UV/Vis diffuse reflectance spectra, as well as in their photocatalytic activities. Photoactivity was evaluated through the degradation of the model contaminant acetaminophen under UV irradiation, and the results confirmed the superior performance of the synthesized TiO 2 microspheres, exceeding the commercial standard TiO 2 P25 by ca. 60% in terms of reactivity. [Display omitted] [ABSTRACT FROM AUTHOR]

BACKGROUND: The wide bandgap and low activity under visible light of titanium dioxide (TiO2) have limited its use in many industrial processes. This limitation is associated with the inadequate solar spectrum that activates its surface, where most of the photoexcited electron–hole pairs recombine thus, leading to a drop in the photocatalytic performance. Immobilization of TiO2 on the surface of other materials such as silicon is a suitable approach to overcome these drawbacks. However, the known immobilization methods require either high‐temperature or high‐pressure conditions. The objective of the present work is to introduce and evaluate a low power‐consumption electrodeposition method for creating a new photocatalyst that can act in visible light using electrochemical anodization for immobilizing the TiO2 on a silicon wafer surface. Two methods were utilized for immobilization which is electrodeposition and sol–gel. The prepared photocatalyst surface and composition were characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). RESULTS: The laser‐aided electrodeposition method created a unique porous silicon surface after the itching process, where the TiO2 was successfully immobilized on the silicon surface. The resulting SEM images confirmed the formation of three‐dimensional (3D)‐like structures on the silicon surface that resulted in a higher light absorption efficiency. The methylene blue degradation rate was higher by 60% using the 3D structured surface when compared with that prepared by the sol–gel method. CONCLUSION: Unique microstructures were created on the silicon surface by the laser‐aided electrodeposition method that enables photocatalysis in visible light. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) is the most used semiconductor for heterogeneous photocatalysis. However, there is a limitation on its application since TiO 2 works as catalyst only under ultraviolet radiation. Therefore, the synthesis of high-performance TiO 2 NPs by a direct method without further calcination could improve the use of this catalyst. The current work aimed to obtain anatase/rutile TiO 2 nanoparticles for photocatalysis under UV light by a direct method without further heat treatment. A 2k factorial design was used to evaluate the effect of the order of addition and ratio of the precursor/reducing agents on the synthesis of the NPs. TiO 2 nanoparticles with large surface area were synthesized via the controlled precipitation method. The NPs were characterized by the XRD, DSC/TG, FTIR, BET, DLS, ELS, UV–Vis, FESEM-EDS techniques, and by the photocatalytic activity test. The commercial TiO 2 NP P25 Evonik was used as standard photocatalyst for comparison with the obtained samples. The specific surface area (BET) of the TiO 2 NP samples was three to five times higher in comparison to P25. The photoactivity of the TiO 2 NP samples and P25 was determined as the discoloration of methylene blue and rhodamine B dyes under UVA radiation (330 nm, 12 W/m2) for 180 min. The results showed that the discoloration efficiency of the synthesized TiO 2 NP samples is equivalent to that of the P25 sample. The synthesis of TiO 2 nanoparticles via the controlled precipitation method using only two reagents proved to be a viable and promising route. The method does not require heat treatment for titanium dioxide crystallization and is still capable of producing a mixture of ideal phases to delay the recombination of the photogenerated electron-hole pair, contributing to the increase of the photocatalytic efficiency. The TiO 2 NP samples will be used to the degradation of recalcitrant pollutants in water as textile dyes and pharmaceutical byproducts. • Synthesis of TiO 2 NPs at room temperature using TiCl 4 and NH 4 OH by precipitation. • NPs were spherical with crystallites of 12–26 nm and a mix of 82/18 of anatase/rutile. • Ti– O –Ti bonds were identified by FTIR and the specific surface area was 130–230 m2/g. • The band gaps ranged from 3.13 to 3.25 eV in comparison to 3.44 eV for the P25. • The degradation of methylene blue was 100% and 87% for rhodamine B after 180 min. [ABSTRACT FROM AUTHOR]

Visible light absorption peak from near-field dielectric scattering was observed in case of Pt nanoparticles directly supported on P25. This absorbed scattered light could drive visible-light photocatalytic pure water splitting (λ>420 nm). It is interesting that the roles of Pt and P25 in photocatalytic hydrogen generation were switchable under different irradiation conditions. Under UV–vis irradiation, P25 represented a photocatalyst while Pt was cocatalyst. Under visible light irradiation (λ>420 nm), Pt would prefer to act as a photocatalyst while P25 was analogous to cocatalyst. Moreover, defects (Ti 3+ or V O ) on the surface of Pt/P25 would be generated under UV irradiation. These defects are similar with a sacrificial agent to consume photogenerated holes, which are necessary for visible-light-drive photocatalytic pure water splitting. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Commercial TiO 2 photocatalyst P25 was first used as a support to prepare Ag-deposited catalysts by adsorbed-layer nanoreactor synthesis (ANS). Characterizations were performed by UV–vis diffuse reflectance spectroscopy, TEM, XRD, XPS, PL spectroscopy, and photo-electrochemical analysis. Results showed that Ag nanoparticles with size of less than 10 nm distributed very homogeneously on the TiO 2 surface. The adsorption layer on the TiO 2 surface acting as a nanoreactor led to tight interaction between quantum-size Ag particles and the TiO 2 surface, thereby introducing staggered heterojunction structures into the catalysts. The heterojunction between quantum-sized Ag particles (less than 10 nm) and TiO 2 led to the surface plasmon resonance effect and strong visible-light response of catalysts. Ag deposition further caused distortions in TiO 2 crystal lattices. Both the heterojunction and TiO 2 lattice distortions enhanced the separation efficiency of charge carriers, which improved the photocatalytic activity for phenol in seawater under visible-light irradiation. The catalyst exhibited high stability and reusability after six cycles because of its morphological stability. [ABSTRACT FROM AUTHOR]

The physical integrity and photocatalytic performance of titanium dioxide (TiO 2 ) deteriorate with aging. Here we propose a pre-treatment with nitric or sulfuric acid of commercial TiO 2 nanopowders used in coating, mortars, or paints. The diffuse reflectance is increased between 1500 and 2500 nm by 0.04 and 0.06, respectively, with nitric and sulfuric acid (unaffected by neutralization). Nitric acid causes a decrease in crystallinity and photocatalytic activity, which drops by almost 20%; this drawback is prevented by post-treatment neutralization, which allows to recover initial photocatalytic efficiency and even increase it. Treatment with sulfuric acid shows no significant effect on photoactivity, instead. [ABSTRACT FROM AUTHOR]

Photoremediation of pesticides under natural sunlight will not be distant a dream any more due to rapid development in the field of catalysis and its related technology. 2,4-dichlorophenoxyacetic acid (2,4-D) is a common broad-leaved weeds, found in surface and groundwater at concentrations above the maximum containment level, is chosen as model pollutant in this study. Hydrothermal synthesis of TiO 2 under sol-gel route resulted in altered band gap material with good crystallinity and particle size. Further, the overview of its degradation is compared with commercial TiO 2 such as P25, Hombicat UV-100 and commercial brand of TiO 2 (C-TiO 2 ). More importantly, commercial viability of the catalyst was assessed in natural sunlight for its photocatalytic activity and selectivity. The chosen catalyst was characterized using XRD, SEM, EDAX, Raman spectroscopy, FTIR and DRS-UV for its structural, functional and electronic properties. Hydrothermal catalyst (H-TiO 2 ) showed degradation of 96% under UV light and 83% under solar light due to its altered band gap (3.16 eV), selective anatase phase ratio appending to similar particle size and crystallinity as that of P25. The major intermediates of 2,4-D degradation were identified for H-TiO 2 and its selective degradation mechanism was highlighted. Thus, this work not only puts forward the importance of material characteristics for mitigation of model pollutant but also its feasibility for practical implication under natural sunlight. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) were successfully synthesized by a facile and green hydrothermal method, and further coupled with P25 (commercial TiO 2 ) to form CQDs/P25 heterojunctions for enhanced photocatalytic activity. Two typical precursors, glucose and citric acid were selected as precursors for the synthesis of CQDs. The effects of precursors on the properties of CQDs and the photocatalytic activity of resultant CQDs/P25 was indeed investigated. The TEM, Raman and XPS analysis revealed the good combination of CQDs on the surface of P25. The photodegradation experiments indicated that CQDs/P25 exhibited enhanced photocatalytic performance than that of pure P25. In addition, with the better crystallinity of CQDs, the higher photocatalytic activity of CQDs/P25 was achieved. More importantly, based on the comprehensive and detailed discussion, the hydrothermal carbonization process of various precursors and the possible mechanism for the enhanced photocatalytic activity of different CQDs/P25 composites were significantly put forward. [ABSTRACT FROM AUTHOR]

The defect structures of photocatalytic improved Degussa P25 powder were evaluated by X-ray photoelectron spectroscopy (XPS), paramagnetic resonance spectroscopy (EPR) and in situ studies of the electrical resistivity in order to understand the charge carrier transport inside the material. Annealing the titanium dioxide in vacuum at temperatures below the phase transition temperature did not increase the oxygen defect concentration drastically. However, annealing Degussa P25 powder in vacuum resulted in a redistribution of Ti 3+ -lattice states and lattice oxygen vacancies. The diffusion of these lattice oxygen vacancies from the bulk to the surface of the material forms charge carrier trapping sites. Such transformation of the defect structure of TiO 2 leads to switching from an insulating state to a conducting state. [ABSTRACT FROM AUTHOR]

In this article, ferrite materials BiFeO 3 (BFO), CoFe 2 O 4 (CFO) and Y 3 Fe 5 O 12 (YIG) are prepared by hydrothermal method and introduced into dye-sensitized solar cells (DSSCs) for the first time. The properties of ferrite materials were measured by XRD, UV and TEM. The DSSCs, sensitized by N719, were tested under 100 mW cm −2 , AM 1.5G simulated sunlight. The power conversion efficiency(PCE)of DSSC based on P25 TiO 2 doped with ferrites was increased compared with undoped P25 TiO 2 . The best doping amount was 0.2% for all the ferrites. The optimized Jsc of 11.7 mA/cm 2 and PCE of 5.67% were achieved in the DSSC doped with 0.2% of CFO. The enhanced performance is attributed to its improved optical absorption, light scattering effect and better charge transfer properties induced by the existence of ferrites in P25 TiO 2 . [ABSTRACT FROM AUTHOR]

Deposition of copper on titanium dioxide holds great promise in producing materials with high activity in the photo-production of hydrogen by aqueous reforming of alcohols. This work aims at comparing hydrogen evolution through photoreforming of alcohols over photocatalysts prepared by in situ photodeposition of copper on three TiO 2 commercial samples (P25, pure anatase, and pure rutile). The adoption of a single catalyst preparation method and experimental setup allowed to unequivocally ascribe the differences in hydrogen evolution to surface properties of the TiO 2 sample tested, thus overcoming the major constraints found in the literature. The resulting samples were extensively characterized by several complementary techniques. Correlations between hydrogen production rates and physical-chemical properties of the samples are discussed. The analyses highlight the major role played by physical size and surface properties of TiO 2 particles in determining the morphology, the dispersion of zero-valent copper nanoparticles on the TiO 2 surface and, ultimately, the photocatalytic performances. Understanding the correlation between properties and photocatalytic response of copper-modified TiO 2 nanoparticles acts as a remarkable lever for the future development of new TiO 2 -based materials exhibiting high efficiency for hydrogen generation under UV–visible light irradiation. [ABSTRACT FROM AUTHOR]

We report a systematic study of the controlled synthesis of new hybrid spherical TiO 2 nanoparticle cluster (TiO 2 -NPC) homogeneously decorated with noble metal nanoparticles (NPs) by gas-phase evaporation-induced self-assembly. Silver NP (AgNP) was used as the representative noble metal NP. The degradation of methyl blue (MB) in the aqueous solution was chosen as the representative system for the study of photocatalysis, which were tested and evaluated with respect to irradiation conditions and the presence of bovine serum albumin (BSA). The results show that particle size and chemical composition of the hybrid nanostructure were tunable by choosing the suitable concentration of precursors. The photocatalytic activity of AgNP-decorated TiO 2 -NPC was strongly affected by the light irradiation and the ligand-nanoparticle interfacial interaction. The presence of BSA influenced molecular conjugation to the surface of the hybrid nanostructure. Under conditions of simultaneous competitive adsorption of MB and BSA, the combination of AgNPs improved the photocatalytic activity of the TiO 2 -NPC-based catalysts. Our work describes a prototype methodology to fabricate TiO 2 -NPC homogeneously decorated with noble metal NPs with well-controlled material properties. The mechanistic understanding developed in this study can be useful for the future optimization of material properties of hybrid nanostructures versus interfacial interactions with the surrounding molecules. [ABSTRACT FROM AUTHOR]

For photocatalytic degradation of organic pharmaceutical pollutants in wastewater, an important limitation is low photonic efficiency. To solve this problem, using periodic illumination is a good option. However, due to the nature of widely applied traditional mercury lamp, which cannot be turned on and off efficiently, the study of periodic illumination was limited. In this research, ultraviolet-A/light emitting diode (UVA/LED) lamp was introduced and a TiO 2 /UVA/LED photocatalytic system was setup for acetaminophen (Ace) degradation study. The background study was conducted, which included the effects of H 2 O 2 , humic acid and bicarbonate ion concentrations. Different periodic pulse frequencies were applied, results in this study shows that smallest duty cycle (0.2) and shortest cycle time (20 ms) gave the highest photonic efficiency for photocatalytic degradation of Ace in the studied range. The effect of additional H 2 O 2 was also studied. H 2 O 2 added into the heterogeneous reaction system enhanced both decomposition rate and photonic efficiency under both continuous illumination mode and periodic illumination mode. The enhancement effect of H 2 O 2 , however, was found more obvious for controlled periodic illumination, especially for small duty cycles and short cycle times. In addition, by the addition of H 2 O 2 , the mineralization of Ace was accelerated probably due to the increase of hydroxyl radical concentration. [ABSTRACT FROM AUTHOR]

The development of photoactive materials with self-cleaning and depolluting qualities is a hot topic in materials science, given their impact on several technologies, in a wide range of contexts of applications. Anatase phase titanium dioxide (TiO 2 ) is the largest used photocatalyst, with increasing applications ranging from air quality control to renewable energies, to green building materials for zero energy communities. Yet, it is partially transmissive in the near infrared (NIR), which negatively affects the solar reflectance of TiO 2 containing materials. In this contribution we describe an unexpected increase in anatase near infrared (NIR) reflectance observed during environmental exposure. We unveil its complex mechanisms, based on the contact with nitric acid generated by NO x photocatalytic degradation, which causes partial reduction and decrease in crystallinity to TiO 2 . This may open the way for introducing multiple environmentally beneficial effects on TiO 2 pollutants degradation, self-cleaning, and energy performance. [ABSTRACT FROM AUTHOR]

Photocatalytic removal of organic pollutants is a promising pollution treatment technology from the aspect of carbon neutrality. The complex diversity of actual wastewater components, as opposed to single-component systems, can significantly affect photocatalytic mechanisms. In this study, complex pollutant systems were created using various coordinating agents, and the effects of P25 on the photocatalytic removal of methyl orange (MO) in these systems and corresponding photocatalytic mechanism were investigated. The results show that photocatalytic removal of MO by P25 using ligands is significantly more efficient, especial removal of MO by the EDTA-P25 (P-E 2.5) coordination system resulted dramatically improved MO removal (97.4% versus 12.3% achieved by pure P25 after 15 min), with the reaction rate improved 23.8-fold. Theoretical calculations show that the effective coordination bonds formed by the coordinating agent and Ti atoms reduce the adsorption energy of P25 for MO. In addition, introduction of the coordinating agent EDTA reduces the transition state energy during the MO degradation process and greatly accelerates the reaction rate, and the conduction band position of the EDTA-P25 coordination system shifts to a more negative potential, which induces to the generation of •O 2 − for effective MO degradation. [Display omitted] • Coordination-induced causes a change in the photocatalytic mechanism. • Coordination-induced reduces the adsorption energy and the transition state energy. • Photocatalytic mechanism in complex organic pollutant systems is analyzed in depth. [ABSTRACT FROM AUTHOR]

A new composite of TiO 2 (P25) and N-doped carbon quantum dots (P25/NCQD) was prepared by a hydrothermal method and was used for the first time as catalyst of the photo- oxidation of NO under UV and visible light irradiation. P25/NCQD composite exhibited a NO conversion (27.0%) more than two times higher of that observed for P25 (10%) under visible light and the selectivity of the process was increased from 37.4% to 49.3%. The composite also showed better photocatalytic performance than P25 in the UV region with increases of 36.3% on NO conversion and 16.8% on selectivity. Moreover, compared with P25, the photodegradation ratio of methylene blue was enhanced from 68% to 91% after UV irradiation for 1 h. NCQD played a crucial role on the photocatalytic activity improvement of P25/NCQD, increasing visible light absorption, slowing the recombination and improving the charge transfer. [ABSTRACT FROM AUTHOR]

The work focused on improvement of the current response to NO and the reduction of response time of both NO and NO 2 . By adding a layer of TiO 2 catalyst layer, the shortcoming of NO insensitivity of traditional NASICON based amperometric NO 2 sensor was solved. TiO 2 was known as an n-type semiconductor and a high-performance NO oxidation catalyst. We separately applied different types of TiO 2 (rutile and Degussa P25) on the device and compared the test results with the traditional type without a catalyst layer. The results showed that the TiO 2 attached device exhibited a significant improvement to NO response, and P25 was better than rutile TiO 2 on account of the higher activity of anatase TiO 2 . In addition, TiO 2 also played a role of a semiconductor electrode, resulting in the increase of response to NO 2 . The response time of NO and NO 2 was separately shrunk from 153 s, 70 s to 77 s, 43 s owing to the P25 layer. The current responses were found to be barely affected by the coexistence of CO 2 . [ABSTRACT FROM AUTHOR]

Electrophoretic deposition was used to produce titanium dioxide (TiO2) nanostructured films on copper substrate in aqueous media for photocatalytic application. Polyvinyl pyrrolidone (PVP) with a weight rate from 0 to 15% was added to TiO2 P25 suspension in order to enhance film adhesion. The films were characterized by X-ray diffraction, optical microscopy, contact angle measurement, nanoindentation, scratch test and photoluminescence. The photocatalytic activity of the films was tested with amido black 10B under UV irradiation. The results indicated that the morphology and the mechanical properties of films depended on the added PVP amount. Scratch test showed that adhesion strength rose with increased PVP amount. The photocatalytic activity indicated that TiO2 film synthesized with 13% PVP had the highest efficiency. [ABSTRACT FROM AUTHOR]

In this study, a set of CoFe 2 O 4 /SiO 2 /TiO 2 nanocomposites was synthesized. The total concentration of metals (Co + Fe) was varied from 3 to 9 mmol with respect to 1 g of SiO 2 . Titania was formed in two concentrations — 2 and 4 mmol/g. The structure of the samples was analyzed by application of XRD, UV–vis spectroscopy, magnetometry, SEM, low-temperature nitrogen adsorption–desorption and Mössbauer spectroscopy. Photocatalytic degradation of an organic model compound – carbamazepine (CBZ) – was studied in the presence of the nanocomposites under ultraviolet irradiation ( λ = 254 nm) in a batch reactor. Two types of media (distilled and tap water) were used. The X-ray diffraction patterns demonstrate the formation of CoFe 2 O 4 and TiO 2 (anatase). The studied materials reveal a better activity than commercial sample of P25 (Evonik) during degradation of carbamazepine (CBZ). It has been found that the type of water medium affects the CBZ decomposition differently: there is residual CBZ observed in distilled water in 60 min of treatment. Contrastingly, in tap water the total decomposition of CBZ took place. This may be due to the occurrence of Fe 3+ ions which stimulate the formation of active sites of chlorine dissolved in tap water. [ABSTRACT FROM AUTHOR]

Antifungal properties of anatase and rutile crystallites isolated from commercial titania P25 photocatalyst were investigated by mycelium growth in the dark and under indoor light. Investigated fungi, i.e., Pseudallescheria boydii , Scedosporium apiospermum , Pseudallescheria ellipsoidea , Scedosporium aurantiacum, Aspergillus versicolor , Aspergillus flavus , Stachybotrys chartarum , Penicillium chrysogenum , Aspergillus melleus , were isolated from air and from moisture condensed on walls. Anatase and rutile were isolated from homogenized P25 (homo-P25) by chemical dissolution, and then purified by washing and thermal treatment. For comparison, homo-P25 was also thermally treated at 200 °C and 500 °C. Titania samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and scanning transmission electron microscopy (STEM). It was found that properties of titania, i.e., band-gap energy, impurities adsorbed on the surface, nanoparticle aggregation, and kind of fungal structure, highly influenced resultant antifungal activities. It is proposed that some fungi could uptake necessary water and nutrient from titania surface. It was also found that even when differences in mycelium growth were not significant, the sporulation and mycotoxin generation were highly inhibited by light and presence of titania. [ABSTRACT FROM AUTHOR]

TiO 2 microspheres have been employed as a promisingly new photocatalyst for water and wastewater treatment. P25 TiO 2 is commonly employed and its properties are well established as photocatalyst. In this study, photocatalytic activities of the two TiO 2 samples are compared by degrading sulfosalicylic acid (SSA), phenol, and 2,4-Dichlorophenoxyacetic acid (2,4-D) under 365 nm UV illumination in a suspension system at neutral pH and associated optimized TiO 2 dosages. The results showed that the three organic compounds unexceptionally degraded more rapidly on P25 than on TiO 2 microspheres in terms of the concentration–time curves and total organic carbon removals at 120 min. This might me attributed the presence of oxygen vacancies and Ti(III) defects already present on P25 as determined by electron paramagnetic resonance, implying that the defects played an important role for the enhancement of the charge transfer step as rate-determining step. The degradations of three organic compounds on P25 and TiO 2 microspheres could be well described by the first-order rate equation, while the degradation kinetics of SSA on TiO 2 microspheres was quite different. The difference was ascribed to the medium adsorption ability of SSA on the TiO 2 surface. [ABSTRACT FROM AUTHOR]

In this study, we identified the toxic effects of sheet-type titania (TNS), which are being developed as a material for UV-blocking glass, comparing with P25, a benchmark control for titania, in MH-S cells, a mouse alveolar macrophage cell line. After 24 h exposure, the TNS-exposed cells formed large vacuoles while the P25-exposed ones did not. The decreased levels of cell viability were similar between the P25 and TNS groups, but ATP production was clearly lower in cells exposed to the TNS. P25 decreased the expression of calnexin protein, an endoplasmic reticulum (ER) membrane marker, and increased the number of cells generating ROS in a dose dependent manner. Meanwhile, TNS dilated the ER and mitochondria and increased the secretion of NO and pro-inflammatory cytokines, but not of ROS. Subsequently, we studied the molecular response following TNS-induced vacuolization. TNS started to form vacuoles in the cytosol since 20 min after exposure, and the expression of the mitochondria function-related genes were down-regulated the most in the cells exposed for 1 h. After 24 h exposure, the number of apoptotic cells and the relative levels of BAX to Bcl-2 increased. The expression of SOD1 protein, but not of SOD2, also dose-dependently increased with an increase in caspase-8 activity. Additionally, the MAPK pathway was significantly activated, even though the expression of p-EGFR did not change significantly. Furthermore, the number of apoptotic cells increased rapidly with time and with the inhibition of vacuole formation. Taken together, we suggest that P25 and TNS may target different organelles. In addition, TNS, but not P25, induced paraptosis accompanied by apoptosis in MH-S cells, and the formation of the cytoplasmic vacuoles allowed delay apoptosis following TNS exposure. [ABSTRACT FROM AUTHOR]

Photocatalytic properties of titanium (IV) oxide (TiO) in anatase form can be used for various purposes, including photocatalytic purification of water. For such an application, suspended or fixed photocatalytic reactors are used. Those with fixed phase seem to be preferred due to some advantages, one of which is the avoidance of photocatalyst filtration. To avoid leaching and exfoliation of the fixed phase, an immobilization procedure leading to a good adhesion of a catalyst to a substrate is crucial. Within this work, we present physical and photocatalytic characterization results of five commercially available TiO photocatalysts (P25, P90, PC500, KRONOClean 7000, VPC-10) and one pigment (Hombitan LO-CR-S-M), which were successfully immobilized on glass slides by a 'sol suspension' procedure. Different mechanical tests and characterization methods were used to evaluate the stability and morphology of the layers. Evaluation of photocatalytic activity was done by tests under UVA and UV-vis irradiation, using a method based on the detection of the fluorescent oxidation product of terephthalic acid (TPA), i.e., hydroxyterephthalic acid (HTPA). Aeroxide® P90 incorporated into the silica-titania binder was the most photocatalytically active layer and, unlike the others, showed significant increase of photocatalytic activity through the entire range of tested UVA irradiation intensities (2.3 mW/cm-6.1 mW/cm). The high mechanical stability of some photocatalytic layers allows using them in water photocatalytic purification reactions. [ABSTRACT FROM AUTHOR]

Highlights: [•] A modified sol–gel method was applied in order to prepare photocatalytically active TiO2–P25 nanocomposite thin films. [•] Peroxotitanic acid sol (PTA) was employed to produce TiO2 and TiO2–P25 nanocomposite thin films on borosilicate glasses after three dip coatings. [•] Band-gap investigations were performed on both TiO2 and TiO2–P25 nanocomposite thin films revealed negligible difference on their optical property. [•] The photocatalytic activities of TiO2–P25 nanocomposite thin films were quite superior in compared with those in TiO2 thin films. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wavelength and irradiance dependences of standard commercial TiO2 samples. [•] Photoactivity and colour change in Kronos C–TiO2 under UVA light. [•] Implications for outdoor environmental applications. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanotube (TNT) films were prepared by pulsed laser deposition (PLD) of P25 and P90 TiO2nanoparticles onto stainless steel foils followed by a hydrothermal treatment (HT). Heating the PLD films in a TNT precursor solution at 150°C resulted in a well-adhered dense mat of TNTs that were ∼10 nm in diameter with a pore size of ∼4 nm. The TiO2nanotube films were characterised by SEM, TEM, XRD and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) and the benchmark TiO2 photocatalyst (P25) were used to prepare different composites (GOP), by a simple method of mixing and sonication, varying the GO content and the heat-treatment temperature under nitrogen. The composites were characterized by thermogravimetric (TG) and differential thermogravimetric (DTG) analyses, scanning electron microscopy (SEM), physical adsorption of nitrogen, UV–Vis and IR diffuse reflectance spectroscopies (DRUV and DRIFT), and point of zero charge (pHPZC) measurements. The morphology, microporosity and S BET of the composites did not vary significantly in comparison to P25, while an increase of their mesoporosity and mesopore diameter were observed due to the formation of GO aggregates coated with P25 nanoparticles. The aggregates were stabilized by the formation of Ti O C bonds, which in turn produced a narrowing of the band gap relative to P25. The surface chemistry of GOP composites varied with the GO content, being more acidic when higher GO content was used. The photocatalytic performance was evaluated for the degradation of diphenhydramine (DP) pharmaceutical and methyl orange (MO) dye under near-UV/Vis irradiation. The first order rate constant of MO photodegradation increased four times for some GOP composites with relation to P25 (i.e., from k =52×10−3 to 207×10−3 min−1). Comparable efficiencies were observed when DP was used as model pollutant (i.e., around k =54×10−3 min−1). The best performing photocatalyst was that containing 1.4wt.% GO and treated at 200–300°C. The improved performance was attributed to the reduction of GO during the thermal treatment and to the good contact between the TiO2 and the carbon phases. [ABSTRACT FROM AUTHOR]

Abstract: Anatase and rutile have the same chemical composition as TiO2 but different crystalline structures and surface structures, which draws effect on the properties of their supported catalysts. Additionally, titania mixture, e.g., Degussa P25, which consists of both anatase and rutile, presents different physicochemical properties with anatase and rutile. In this work, P25-, anatase- or rutile-supported copper oxide catalysts (signed as CuO/P25, CuO/A and CuO/R) were prepared and characterized to study the titania support effect on the physicochemical properties and catalytic properties for the trace CH4 combustion. It is found that the activity of CuO/R is better than the corresponding CuO/A sample when their pore size and specific surface area are comparable, which is attributed to the different chemical states of the copper oxide caused by the different TiO2 support polymorphs. The loading of CuO and subsequent calcination promotes more significant sintering and anatase to rutile transform for CuO/P25 than those for CuO/A. Thus, CuO/R shows better stability than CuO/P25. [Copyright &y& Elsevier]

Abstract: Degussa TiO2 powder (P25) with Cu2O nanocrystals of different sizes deposited on the surface were prepared by a facile ethanol-induced deposition followed with a calcination process at 350 °C and characterized by XRD, XPS, HRTEM and UV–Vis diffuse reflectance spectra, respectively. In our protocol, Cu2O nanocrystals is formed by reducing Cu(II) with the ethanol adsorbed on the surface of P25. The absorption edge as well as photocatalytic activity for H2 evolution are closely related to the size of the Cu2O nanocrystals depending on the Cu content in the as-prepared composites. The 0.9 mol% Cu2O/TiO2 composite with ca. 4 nm Cu2O nanocrystals exhibits the highest photocatalytic H2 evolution rate of 318 μmol h−1 under the illumination of simulant solar light and an apparent quantum efficiency of 28.6% at 365 nm, 397 times higher than that of P25. This enhancement is mainly attributed to the quantum confinement effect of quantum-sized Cu2O nanocrystals (q-Cu2O), which can upgrade the conduction band bottom of q-Cu2O, and thus facilitates the effective separation of photogenerated charge carriers to enhance the photocatalytic activity. The results provided here not only offers a green and simple way for depositing q-Cu2O on the surfaces of P25 to get the photocatalyst with an excellent photocatalytic activity for H2 evolution, but also sheds a new insight for the fabrication of efficient p–n heterojunctions for the separation of electron-hole pairs by quantum confinement effect. [Copyright &y& Elsevier]

Abstract: The present paper describes a new type of composite photo-anode of SiO2/TiO2 that was prepared by adding nano-sized SiO2 into the TiO2 (P25) paste during the fabrication of dye-sensitized solar cells (DSSCs). The effects of the added SiO2 on the performance of DSSCs were investigated and the preparative procedures of DSSCs were optimized. It was found that certain amount of SiO2 added in the P25 powder was crucial to reduce the agglomeration and enhance the dispersion of P25 powders, which helps to achieve a better connection and thus higher electron transfer efficiency not only between the TiO2 particles but also between the TiO2 particles and the FTO substrate. Under the same standard air mass 1.5 illumination (100mWcm−2), the DSSCs constructed by SiO2/P25 composite photo-anodes show higher solar energy-to-electricity conversion efficiency (e.g., η =8.4%) compared to those by bare P25 electrodes (typically η =5.8%). The higher η mainly results from its higher short-circuit photocurrent density (J sc =18.7mAcm−2) while the open-circuit voltage (V oc) remains unchanged and was found to be ∼780mV. The fill factor (FF) was 0.57. The great enhancement in J sc of DSSCs is ascribed to the SiO2 energy barrier layer which increases the separation of injected electrons and oxidized dyes/redox couple as well as retards the recombination reactions in the resulting DSSCs. [Copyright &y& Elsevier]

Photocatalytic nitrate reduction was examined in a model water and in groundwater by using three commercially available titanium dioxide photocatalysts (Evonik P25, Evonik P90, and Sachtleben Hombikat UV100). The photocatalysts were characterized using uniform methods (TEM, XRD, surface area, UV-VIS, surface charge) and their photocatalytic activity was differentiated using these results. Under all experimental conditions, P25 and P90 were superior to UV100, and P90 outperformed P25 with nitrate reductions as high as 77% at the maximum irradiance level used (). The photocatalytic nitrate reduction activity was found to be dependent on the rate of recombination, pH, and the total photocatalyst surface area, with the recombination rate being the limiting variable. Nitrate reduction was more efficient in model water than in groundwater that contained constituents capable of occupying photocatalyst surface sorption sites or scavenging conduction band electrons. The greater efficiencies of P25 and P90 compared with UV100 were attributed primarily to the mixed-phase nature of the photocatalysts, which allow for better charge separation, and the greater activity of P90 over P25 was attributed to a larger surface area. The results should be helpful in the selection of these commercially available photocatalysts to treat a wide range of pollutants other than nitrate. [ABSTRACT FROM AUTHOR]

Abstract: In this investigation, in order to develop photocatalyst materials with improved photo-efficiency and visible light response compared to the state of the art materials, the role of Evonik Aeroxide® P25-TiO2 (P25) nanoparticles incorporated in a modified sol–gel process to yield composite nitrogen and fluorine doped TiO2-P25 (NF-TiO2-P25) films was investigated. The addition of P25 nanoparticles in the sol leads to higher BET surface area, pore volume, porosity and total TiO2 mass, as well as larger thickness and roughness of the films after heat treatment. Microscopy techniques confirmed partial sintering of NF-TiO2 sol–gel formed and P25 nanoparticles having different average size. The existence of well defined regions of only anatase from NF-TiO2 and anatase–rutile mix from P25 was verified in the micro-Raman spectra. The photocatalytic degradation of four microcystins (microcystin-LR, -RR, -LA and -YR) and cylindrospermopsin was evaluated with NF-TiO2 and NF-TiO2-P25 films under visible and UV–vis light. The general reactivity for the microcystins under acidic conditions (pH 3.0) was: MC-LA>MC-LR≥MC-YR>MC-RR where the highest initial degradation rate was achieved with the NF-TiO2-P25 films (5gL−1 of P25 in sol when irradiated with visible light and 15gL−1 of P25 in sol when irradiated with UV–vis light). Cylindrospermopsin showed negligible adsorption at pH 3.0 for all films. Nevertheless, significant photocatalytic removal was found under UV–vis light with maximum P25 loaded films indicating that the degradation was mediated by the involvement of photogenerated reactive oxygen species and not by the trapping reaction of the positive hole. [Copyright &y& Elsevier]

Abstract: Photocatalytic process that uses traditional low pressure mercury lamp and TiO2 as catalyst has attracted numerous attentions recently for the degradation of organic pollutants in water environment. However, there are several important drawbacks to this mercury lamp such as high energy cost and the production of toxic mercury waste. Compared to traditional mercury lamp, the newly emerging UVA/LED is more efficient in converting electricity into light. It has longer lifetime and no toxic waste generation problem exists. Therefore, the purpose of this research was to study the ability of high power ultraviolet A light-emitting diode (UVA/LED) as a light source in the degradation of organic pollutants. The optimal operational conditions were also determined. In this study, a new device equipped with high-energy 365nm UVA/LED using TiO2-P25 as the catalyst was developed and evaluated for photolytic/photocatalytic oxidation of acetaminophen (Ace). The results showed that the chosen UVA/LED alone degraded negligible amount of Ace, while in the presence of TiO2, the concentration of Ace decreased substantially. In most experiments of this study, Ace could be degraded to non-detectable level within 20min. The degradation rate was found to be related to the dosage of TiO2, initial Ace concentration and light intensity. Based on the experimental data, the following kinetic equation was achieved by kinetic modeling: , which was also in agreement with the Langmuir–Hinshelwood (L–H) law. [Copyright &y& Elsevier]

Abstract: We investigated the adsorption capacity and photocatalytic removal efficiency of formaldehyde using a hectorite-TiO2 composite in a bench flow reactor. The same experimental conditions were applied to pure TiO2 (Degussa P25) as a reference. The catalysts were irradiated with either a UVA lamp (365nm) or with one of two UVC lamps of 254nm and 254+185nm, respectively. Formaldehyde was introduced upstream at concentrations of 100–500ppb, with relative humidity (RH) in the range 0–66% and residence times between 50 and 500ms. Under dry air and without illumination, saturation of catalyst surfaces was achieved after ∼200min for P25 and ∼1000min for hectorite-TiO2. The formaldehyde uptake capacity by hectorite-TiO2 was 4.1 times higher than that of P25, almost twice the BET surface area ratio. In the presence of humidity, the difference in uptake efficiency between both materials disappeared, and saturation was achieved faster (after ∼200min at 10% RH and ∼60min at 65% RH). Under irradiation with each of the three UV sources, removal efficiencies were proportional to the Ti content and increased with contact time. The removal efficiency decreased at high RH. A more complete elimination of formaldehyde was observed with the 254+185nm UV source. [Copyright &y& Elsevier]

Abstract: The optimal photocatalyst concentration for industrial wastewater treatment in current photoreactor designs is several hundreds of milligrams per liter. However, the elimination of emerging contaminants (ECs), which are present at extremely low concentrations in waste water treatment plants (WWTP) effluents might be accomplished at much lower catalyst (TiO2) concentrations. One of the main drawbacks of reducing catalyst loading below the optimum is the loss of useful photons which instead are transmitted through the TiO2 suspension without being absorbed by the catalyst. Accordingly, in this work, laboratory and solar pilot-scale experiments were performed with real WWTP effluents to evaluate the kinetics of photocatalytic degradation of 52 emerging contaminants under realistic (ppb) concentrations. The analysis of the samples was accomplished by solid phase extraction (SPE) followed by liquid chromatography–mass spectrometry (LC–MS). In view of the results, low concentrations of TiO2 of the order of tens of milligrams per liter were found to be insufficient for the degradation of the ECs in photoreactors with a short light-path length (29cm). However, it was established that solar reactors of diameters of several hundreds of millimetres could be used for the efficient removal of ECs from WWTP effluents. The results presented show a general methodology for selecting the most efficient reactor diameter on the basis of the desired catalyst concentration. [Copyright &y& Elsevier]

Abstract: Iron (III)-doped TiO2 powder photocatalysts were prepared by modified uneven doping method using ammonium oleate in order to promote the formation of p–n junction composite structure, and were characterized by X-ray diffraction (XRD), TEM, BET, UV–vis and PL spectroscopy. The photocatalytic activities of TiO2-based nanoparticles were evaluated by the photocatalytic rate of methyl orange oxidation. These iron (III)-doped TiO2 photocatalysts are the composite powders having the p–n junction of n-type undoped TiO2 with p-type TiO2 doped by Fe evenly, were shown to have a much higher photocatalytic destruction rate than that of undoped TiO2. The n–n junctions may be responsible for the high photocatalytic activity of P25 and other mix-phase crystalline titania. [Copyright &y& Elsevier]

Abstract: Oxidation of dichloracetic acid (DCA) by two titanium dioxide catalysts (P25 and a nanoparticulate rutile (NR)) was measured at pH 3 and the results compared with parallel measurements on the same TiO2s modified by deposition of platinum. Although the platinum loading corresponded to less than one platinum crystallite for each TiO2 crystal, platinization significantly increased photocatalytic activity – 30-fold in the case of NR, high area rutile. This has been attributed, by ourselves and others, e.g. , to the increased efficiency of hole-generation as a consequence of electron trapping by the platinum. Each catalyst was then milled, and UV–vis transmission spectra were used to show that milling improved the catalyst dispersion. Milling unplatinized TiO2 caused either insignificant decreases (P25) or increased activity (NR). This contrasts with the previously reported significant decrease in activity for propan-2-ol oxidation. The difference is attributed to a different dependence on UV intensity of DCA degradation and propan-2-ol oxidation. DCA oxidation rate increased linearly with UV intensity, I, whereas propan-2-ol oxidation varies as I 0.5. However, milling did decrease significantly the rate of DCA oxidation by both of the platinized catalysts, especially by the platinized rutile. It is suggested that most of the UV is absorbed by TiO2 crystals that have no platinum, but that in poorly dispersed TiO2, UV-generated electrons may be transported along a chain of TiO2 crystals to a platinized TiO2 at which they are trapped. This is analogous to the antenna model postulated by Bahnemann and co-workers . It is proposed that milling breaks down the antennae. Consequently electron transport is disrupted and the effectiveness of electron trapping by platinum is reduced and the measured photoactivity decreases. [Copyright &y& Elsevier]

Abstract: In the solution state, photocatalysis of micro- and nano-sized anatases can be optimized at flat band and in a high pH solution, respectively. Furthermore, a remarkable photocatalyst that can be adopted over a wide range of pH values was produced by mixing commercial micro- and nano-sized anatases. Mixing causes the electron transfer between the identical phase but different-sized TiO2 particles, subsequently separating the electrons and holes, as well as greatly facilitating photocatalysis. As is well known, the commercially available photocatalyst P25, a mixture of anatase and rutile, achieves a superior photocatalytic performance from pH 3 to 10, owing to the electron transfer between the various phases. This study elucidates these mixed photocatalysts, P25 and mixture of micro and nano-sized anatases. [Copyright &y& Elsevier]

Abstract: Gas-phase photocatalysis experiments may benefit from the high sensitivity and good time response in product detection offered by μ-reactors. We demonstrate this by carrying out CO oxidation and methanol oxidation over commercial TiO2 photocatalysts in our recently developed high-sensitivity reactors. We demonstrate that the system exhibits great versatility in terms of photocatalyst, illumination source and target reaction. [Copyright &y& Elsevier]

Abstract: The present work studies the effect of the components of a photocatalytic paint towards the photooxidation of NO. It was used a vinyl high quality exterior paint, modified with photocatalyst P25. NO conversion and selectivity towards nitrate and nitrite were obtained in an experimental photocatalytic reactor that implements essentially the standard ISO 22197-1:2007(E). It is concluded that the paint matrix plays an important role on the photocatalytic activity: pigmentary TiO2 absorbs competitively the UV light, being the most critical component affecting the photocatalytic activity; extenders, such as CaCO3, impair the photoactivity, especially when water is involved in mixing the paint components; organic components mostly affect the performance of the paint during a transient period time of ca. 100–250h. [Copyright &y& Elsevier]

Abstract: Fundamental photocatalytic behaviors were investigated for mechanical mixtures of TiO2 crystalline particles (P25) and MFI type zeolite (silicalite) in the decomposition reaction of 2-propanol vapor in air for the first time. Mechanical mixing enables reliable comparisons to be made between photocatalysts because the contents of TiO2 and the adsorbent can be widely varied (51 times in this study) while keeping the particle size and crystallinity of TiO2 unchanged. That is, the use of mechanical mixture highlights the behavior of molecules adsorbed in the microporous crystals, keeping the TiO2 unchanged. In the case of the mixed photocatalysts, the initial 2-propanol concentration in the gas phase was significantly reduced because of adsorption into the zeolite. After photo-irradiation started, 2-propanol was decomposed to CO2 with no (or trace amount of) acetone detected in the gas phase. The analysis of final amount of CO2 formed by the decomposition demonstrated that just by the mechanical mixing of TiO2 and zeolite, the TiO2 photocatalyst decomposed completely the reactant and intermediate molecules strongly adsorbed into the zeolite. On the other hand, in reference experiments in which TiO2 and zeolite were not mixed and were separately placed in a photoreactor, the organic compounds strongly adsorbed in the zeolite could not be decomposed to CO2 by the photocatalyst. It is notable that the CO2 formation rates for the mixed photocatalysts were mostly constant for those comprising 40 wt% or larger amounts of zeolite, while being slower than for pure TiO2. The rate-determining step was discussed based on these data. The present study showed that the mixed photocatalyst could remove organic vapors by adsorption in the dark and decompose completely to CO2 at moderate reaction rates under photo-irradiation with minimized evolution of intermediate molecules into the gas phase. [Copyright &y& Elsevier]

Fiber-shaped dye-sensitized solar cell (FDSC) is one of efficient energy generation devices for soft electronics, owing to low-cost and dim-light operable features. The key component of FDSC is photoanode, which is responsible for absorbing incident light and generating charges. Designing TiO 2 structure is significant for fabricating efficient photoanode of FDSC. In this study, it is the first time to fabricate TiO 2 nanoparticle-decorated TiO 2 microcone array (TMC) with holes using simple two-step anodization and dip-coating processes as semiconductor on photoanode of FDSC. Different H 2 SO 4 concentrations is used to creating holes on TMC. Holes are generated on TMC in anodization process, but TMC are detached from Ti wire more seriously when higher H 2 SO 4 concentration is used. The optimized photoanode of FDSC is prepared using 30 mM H 2 SO 4. The optimized FDSC shows solar-to-electricity conversion efficiency (η) of 2.52%, while the FDSC with the pure TMC photoanode only shows η of 1.68%. The better photovoltaic performance of FDSC comprising TiO 2 nanoparticle-decorated TMC with holes photoanode is owing to abundant contacts between TMC and TiO 2 nanoparticles and high surface area of TiO 2 nanoparticles for dye adsorption. The highest collection efficiency of 92.21% is also achieved for the FDSC with the optimized photoanode, analyzed using intensity modulated photocurrent/voltage spectroscopy spectra. [Display omitted] [ABSTRACT FROM AUTHOR]

Heterogeneous photocatalysis of TiO2 is one of the most efficient advanced oxidation processes for water and air purification. Here, we prepared hierarchical TiO2 layers (Spikelets) by hollow-cathode discharge sputtering and tested their photocatalytic performance in the abatement of inorganic (NO, NO2) and organic (4-chlorophenol) pollutant dispersed in air and water, respectively. The structural-textural properties of the photocatalysts were determined via variety of physico-chemical techniques (XRD, Raman spectroscopy, SEM, FE-SEM. DF-TEM, EDAX and DC measurements). The photocatalysis was carried out under conditions similar to real environment conditions. Although the abatement of NO and NO2 was comparable with that of industrial benchmark Aeroxide® TiO2 P25, the formation of harmful nitrous acid (HONO) product on the Spikelet TiO2 layers was suppressed. Similarly, in the decontamination of water by organics, the mineralization of 4-chlorophenol on Spikelet layers was interestingly the same, although their reaction rate constant was three-times lower. The possible explanation may be the more than half-magnitude order higher external quantum efficacy (EQE) compared to that of the reference TiO2 P25 layer. Therefore, such favorable kinetics and reaction selectivity, together with feasible scale-up, make the hierarchical TiO2 layers very promising photocatalyst which can be used for environmental remediation. [ABSTRACT FROM AUTHOR]