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Graphical abstract Highlights • Novel chemically mixed sol gel TiO 2 and graphene composite catalyst. • Catalyst with dual NO 2 sensing and abatement capabilities. • Conductometric sensing of NO 2 in the range 70–1750 ppb. • Photocatalytic abatement of NO 2 under simulated sunlight radiation 280–780 nm. Abstract Human exposure to volatile organic compounds and NO 2 can lead to health problems, therefore strategies to mitigate against the risks are required. Abatement and sensing are approaches which could both neutralise and monitor these species thus providing a safer environment and warning occupants of harmful levels. This paper presents pure TiO 2 and TiO 2 /graphene hybrids synthesized through a sol-gel route. Electron optical, helium ion microscopy, X-ray diffraction and spectroscopic methods have been applied to elucidate the physical and chemical behaviour. NO 2 sensing properties of TiO 2 /graphene hybrids formed by the addition of graphene to the reaction vessel prior to initiating the sol gel reaction followed by annealing (GTiO 2 S), and an alternative manufacturing method involving the addition of graphene to TiO 2 nanoparticles which had already been annealed (GTiO 2 M) were compared and evaluated. A conductometric sensor based on TiO 2 /graphene prepared using material GTiO 2 S showed a higher response to NO 2 compared to sensors based on pure TiO 2 and TiO 2 /graphene prepared with material GTiO 2 M. Under UV irradiation generated by a low power LED, the sensor showed a remarkably enhanced response to 1750 ppb NO 2 , about double the response in the dark, and a limit of detection of about 50 ppb of NO 2 (Signal/Noise = 3). Photocatalytic tests to assess the degradation of NO x showed that TiO 2 /graphene hybrids using material GTiO 2 S were the most active amongst the whole series of TiO 2 -based materials. Our data highlights the unique characteristics of material GTiO 2 S TiO 2 /graphene and the suitability for multi-purpose applications in the field of environmental monitoring and remediation. The capability of the material for both sensing and abatement of NO x could be exploited to offer a safer environment through providing a warning of the presence of NO x whilst also reducing levels. [ABSTRACT FROM AUTHOR]

Tungsten, silver, and tungsten/silver co-doped titaniananopowders were synthesised via an aqueous sol-gel method. The dried gels were thermally treated at 2 different temperatures, and the occurrence of the amorphous phase was assessed, using the combined Rietveld-RIR method, on the X-ray powder diffraction data. Systematic studies of the crystal structure and of the optical properties of the powders - made with diffuse reflectance spectroscopy (DRS) - were performed. The energy band gap was calculated using the differential reflectance method; their morphology was investigated using field emission scanning electron microscopy and transmission electron microscopy analyses (FE-SEM and TEM, respectively). The photocatalytic activity of the samples was assessed in liquid-solid phase, under UVA-light and visible-light irradiation, monitoring the degradation of an organic dye. The influence of the phase composition, optical properties, dimensions, and specific surface area of the powders on the photocatalytic activity was thoroughly discussed. [ABSTRACT FROM AUTHOR]

Abstract: A series of TiO2–SiO2 mixtures – having the following stoichiometry Ti1−x Si x O2, with x =0, 0.1, 0.3 and 0.5 atoms per formula unit – were prepared by using precursor oxides and fired at three temperatures (900, 1000 and 1200°C). The modifications in the structure and, consequently, on the photocatalytic activity, induced by the addition of SiO2 into the TiO2 powder, were thoroughly investigated by using various analytical techniques: X-ray powder diffraction, electron microscopy (FE-SEM and TEM), XPS, FT-IR, DRS and BET analysis. The results underlined as essentially no solid solution occurs between the two crystalline end-members. Nevertheless, silica addition caused a retarding effect on anatase-to-rutile phase transformation and on the crystallite growth. The photocatalytic activity of the powders was assessed in gas phase and the results were explained by taking into account the anatase and rutile relative amounts in the samples, their crystallite size, the surface hydroxyl groups adsorbed on the photocatalysts and the surface area of the mixtures. [Copyright &y& Elsevier]

A new and original method, based on a non-aqueous sol–gel process, has been successfully established to produce quasi-spherical monodispersed TiO 2 nanoparticles (NPs) and also noble metals (NM) @TiO 2 heterostructures (NM = Au, Pt, Ag, 2 wt%), in one-pot and at low temperature. This has been achieved by using titanium oxyacetylacetonate as new single source precursors. This system has been deeply investigated by advanced characterization techniques. By using NMR, we have demonstrated the relatively complex mechanism behind this apparently simple synthesis, mediated by the reaction of the solvent and generated species, with many separate organic and organometallic molecules identified as being involved in the mechanism. The morphology and structure of the NM@TiO 2 heterostructures were investigated by advanced scanning transmission electron microscopy while the chemical state of the noble metal nanoparticles was check by X-ray photoelectron spectroscopy (XPS). Undoped and noble metal (Au, Pt, Ag) decorated quasi/spherical TiO 2 nanoparticles worked also as sensing interfaces, leading to the development of a highly sensitive conductometric NO gas sensor under both dark and UV–vis light irradiation, in the first result of its kind. Furthermore, the photocatalytic activity (PCA) was also evaluated, in the gas–solid phase, by monitoring the degradation of NO x under solar-light irradiation. Au-modified TiO 2 showed improved photocatalytic efficiencies, compared to unmodified TiO 2 . [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphene nanoplatelets were included into the TiO 2 /WO 3 system. • Examined in the removal of gaseous benzene, and generation of H 2. • Position of the conduction bands played indeed a key-role. • Specimen with 15 mol% WO 3 and 1 wt% graphene – a five-fold increase in yield. Clean energy, as well as air and water pollution, have emerged as significant challenges in today's society. Photocatalysis offers a potential solution to address these issues. It is an advanced oxidation process that utilises light to activate a semiconductor. Among photocatalytically active materials, titanium dioxide (TiO 2) semiconductors are widely recognised. However, the performance of TiO 2 is hindered by its wide band gap (∼3.2 eV) and high recombination rate of photo-generated electron-hole (e−−h+) pairs. To overcome these limitations, TiO 2 in heterojunction with tungsten trioxide (WO3) has gained substantial attention for various photocatalytic applications. However, the literature reports contradictory behaviours due to variations in synthesis techniques and photocatalytic applications. In this study, we extensively investigated the photocatalytic properties of the TiO 2 /WO 3 system for the removal of gaseous benzene, and H 2 generation. To enhance the transport and lifetime of photo-generated excitons, graphene nanoplatelets were incorporated into the TiO 2 /WO 3 system. We examined several parameters that influenced the photocatalytic activity of the synthesised materials, including the WO 3 to TiO 2 ratio, the presence of graphene, and the specific photocatalytic application. Interestingly, the position of the conduction bands played a crucial role in hydrogen generation. The TiO 2 /WO 3 system exhibited a type-II heterojunction. While the hybridisation of TiO 2 with WO 3 was found to be detrimental to light-induced benzene removal and H 2 generation, the modification of TiO 2 /WO 3 with graphene nanoplatelets significantly improved the photocatalytic hydrogen generation. Notably, the specimen with 15 mol% WO 3 and 1 wt% graphene demonstrated a five-fold increase in yield compared to its counterpart without graphene. These findings provide valuable insights for data-driven catalysis research. [ABSTRACT FROM AUTHOR]

Abstract: Anatase-structured TiO2 films were deposited on a commercial fluorinated polymer (FEP) with a treated surface, by means of a sol–gel dip-coating technique. Two different curing temperatures were investigated and the film microstructures were characterized by X-ray diffraction, atomic force microscopy and scanning electron microscopy analyses. The prepared samples presented very high performances in terms of photocatalytic activities, analyzed by the degradation of an organic dye in a liquid medium, and of bactericidal activities, tested on Staphylococcus aureus (S. aureus, a Gram positive bacterium) and Escherichia coli (E. coli, a Gram negative bacterium). [Copyright &y& Elsevier]