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Polymeric carbon nitride (C 3 N 4 ) is a semiconductor material which is a very promising green photocatalyst with good physico-chemical properties and stability. It is a metal-free carbon based non-toxic material which can be easily obtained from earth-abundant components. The robustness and versatility of C 3 N 4 as a photo-redox catalyst allows its use for selective oxidations by heterogeneous photocatalysis. This paper reviews the state of art in the application of C 3 N 4 as heterogeneous photocatalyst for selective oxidation of alcohols to the corresponding aldehydes. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas–solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs. [Copyright &y& Elsevier]

Abstract: Both commercial and home prepared TiO2 samples impregnated with tungstophosphoric acid (H3PW12O40) were prepared and used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of both types of TiO2 samples along with a marginal effect of the presence of ethanol or HCl during the POM impregnation step on the specific surface area, porosity, morphology, crystallinity and acidity of the samples. Propene was the main intermediate product found in 2-propanol photocatalytic degradation by using the samples containing POM as the photocatalyst, whereas propanone was mainly obtained when the photocatalyst was bare TiO2. Acetaldehyde was also an intermediate product and its amount was always significantly smaller with respect to propanone and propene (when formed). Carbon dioxide and water were the ultimate oxidation products. The selectivity to propene has been attributed to the acidity of the POM supported samples. [Copyright &y& Elsevier]

Abstract: Commercial and home prepared TiO2 samples impregnated with tungstophosphoric acid (H3PW12O40) were used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of TiO2 along with a marginal effect of the presence of the POM on the specific surface area, morphology and cristallinity of the samples. Propene was the main intermediate product revealed in 2-propanol photocatalytic degradation by using as photocatalysts the samples containing the POM, whereas propanone was mainly obtained when the photocatalysts was bare TiO2, both commercial or home prepared. Acetaldehyde was also found as an intermediate product along with traces of isopropyl ether, mesityl oxide and isobutyl-methyl-ketone that were also detected as gaseous products in all the runs. Carbon dioxide and water were the ultimate oxidation products. [Copyright &y& Elsevier]

Abstract: Photocatalytic degradation of 2-propanol was carried out as a probe reaction both in gas–solid and in liquid–solid systems in the presence of TiO2 both bare and impregnated with lanthanide (Sm, Gd, Ho) bis-phthalocyanines (LnPc2) used as sensitizers. Continuous and batch photo-reactors, irradiated with an equal flux of photons, were used in gas–solid and in liquid–solid systems, respectively. Propanone and acetaldehyde were the main intermediates found in both systems during 2-propanol oxidation, whereas carbon dioxide and water were the final oxidation products exclusively in the gas–solid regime. The photocatalysts exhibited significantly higher activity in the liquid–solid system than in the gas–solid one. Samples impregnated with the sensitizers were apparently more photoactive than bare TiO2. The highest photoactivity was shown by the 1.85 HoPc2–TiO2 sample. [Copyright &y& Elsevier]

This work reports on the characterisation and determination of the photocatalytic activity of some TiO2 catalysts prepared using TiCl4 as precursor. The samples, consisting of suspensions, dispersions or powders of nanostructured anatase or rutile phases, were obtained in very mild conditions, i.e., by boiling the solution obtained after hydrolysis of TiCl4 at atmospheric pressure; it is worth noting that no calcination was necessary to obtain photoactive phases. The samples were characterised by X-ray diffraction (XRD), determination of the BET specific surface area (SSA), scanning electron microscopy (SEM) observations and diffuse reflectance spectroscopy (DRS). FT-IR spectroscopy was used to study the surface acidity of the solids. Photodegradation of 4-nitrophenol and gemfibrozil (5-(2,5-dimethylphenoxy)-2,2-dimethyl-pentanoic acid) was used as probe reactions to evaluate the photoactivity and the obtained results showed that the home prepared samples are effective to degrade both substrates. The photoreactivity results were compared to those obtained using commercial photocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: Pure and Sm-loaded brookite nanoparticles and thin films were prepared using TiCl4 as precursor of TiO2. The samples were characterized by X-ray diffraction (XRD), specific surface area (SSA) determination, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements. The photocatalytic activity of the powders was investigated by employing the photodegradation of 4-nitrophenol in a liquid–solid system whilst the photoreactivity of the films was tested by evaluating the rate of degradation of 2-propanol in a gas–solid system. Loading with Sm resulted in a significant improvement of the photoreactivity of brookite and the beneficial effect was attributed to an increased separation efficiency of the photogenerated electron–hole pairs. The content of samarium was an important factor affecting the photocatalytic activity. The optimum amount of samarium was 1% for the powders and 0.1% for the films. There is a relationship between PL spectra and photoactivity, namely, the lower the PL intensity, the higher the photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Silica-supported TiO2 powders were synthesized by a wet method under mild conditions. The aim of the work was the preparation of TiO2/SiO2 additives for photocatalytic cements. Three types of commercial SiO2 were used as supports: Cabot, Axim and Fly Ash. Cabot silica was ultra-pure whereas the other two silica contained different percentages of various oxides. The TiO2/SiO2 samples, denoted TiO2/Cabot, TiO2/Axim and TiO2/Fly Ash, were prepared by boiling suspensions obtained by addition of silica to a solution of TiCl4 in water (volume ratio 1:10). The photocatalytic activity was evaluated in a gas–solid system both in batch and in continuous reactors using 2-propanol as probe molecule. SEM-EDX analysis revealed that titanium dioxide was quantitatively deposited on silica. TiO2/Axim and TiO2/Fly Ash were scarcely active whereas a good photoactivity was exhibited by the TiO2/Cabot sample both in the batch and in the continuous system. Consequently only the last sample was tested for both NO x abatement and for 4-nitrophenol photodegradation in a liquid–solid system. [Copyright &y& Elsevier]

Abstract: Thin TiO2 films were prepared with the dip-coating technique by using sols deriving from titanium tetraisopropoxide. TiO2 films were formed on glass substrates previously covered by a SiO2 layer obtained from a tetraethylortosilicate sol. The films, after a thermal treatment at 673 K, mainly consisted of TiO2 anatase. The samples were characterised by X-ray diffraction, UV–Vis spectroscopy, scanning electron microscopy and atomic force microscopy. The photoactivity of the various films was tested by using as probe reaction the photo-oxidation of 2-propanol in gas-solid regime. The photoreactivity results indicated that the TiO2 films were efficient for degrading 2-propanol under UV illumination, propanone being the only compound detected as intermediate product. Films prepared by using Degussa P25 appeared to be more photoactive, but the coating was easily detached by wiping. [Copyright &y& Elsevier]

The photocatalytic oxidation of acetonitrile (CH3CN) was carried out in aqueous suspensions of polycrystalline TiO2 P25 Degussa irradiated by sunlight. A plug flow photoreactor in a total recycle loop was used for carrying out reactivity experiments in which the concentrations of acetonitrile, of its intermediate oxidation products and of not-purgeable organic carbon (NPOC) were monitored. The influence of the presence of strong oxidant species (H2O2, S2O82−, ClO−) on the process rate was studied. The dependence of acetonitrile photo-oxidation rate on the substrate concentration and on the catalyst amount was also investigated. The photodegradation rate of substrate and NPOC followed first order kinetics with respect to acetonitrile and NPOC concentrations, respectively. The presence of S2O82− and solar irradiation determined the occurrence of homogeneous degradation of acetonitrile and NPOC. In the presence of irradiated catalyst, a significant synergetic effect was observed for NPOC degradation while for the acetonitrile oxidation this effect was not evident. H2O2 did not affect the process while ClO− affected negatively the acetonitrile oxidation rate and it inhibited the NPOC degradation. [Copyright &y& Elsevier]