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Uklanjanje šestovalentnog hroma, Cr(VI), iz otpadnih voda postupkom foto- katalitičke redukcije može da bude efikasan i ekonomičan postupak ukoliko se koristi odgovarajući fotokatalizator, koji je aktivan pod dejstvom vidljivog zra- čenja, stabilan u kiseloj sredini, koji bi mogao da se regeneriše i koristi više puta. Grafitni ugljenik(IV)-nitrid koji je sastavljen isključivo od nemetala, pre- dstavlja netoksičan i pristupačan fotokatalizator koji u teoriji ispunjava navedene kriterijume i ima potencijala da se koristi za redukciju Cr(VI). U ovom radu je grafitni ugljenik(IV)-nitrid sintetisan metodom termičke polime- rizacije uree, koja prema literaturnim podacima, omogućava dobijanje g-C3N4 sa najvećom specifičnom površinom. Dobijen fotokatalizator je pokazao veliki poten- cijal za fotokatalitičku redukciju Cr(VI), pod dejstvom vidljivog zračenja pri pH = 3, u prisustvu limunske kiseline kao „hvatača“ šupljina, bez smanjenja efikasnosti u ponovljenom ciklusu, što je od velikog značaja za razvoj fotokatalize kao metode za uklanjanje toksičnog šestovalentnog hroma iz otpadnih voda., The removal of hexavalent chromium from wastewater by photocatalytic reduction can be an efficient and economical method if a suitable photocatalyst is used, which is active under the visible irradiation, stable in an acidic environment and which could be regenerated and used more than once. Graphitic carbon nitride, which is composed exclusively of non-metals, is a non-toxic and affordable photocatalyst that in theory meets the above criteria and has the potential to be used for the reduction of Cr(VI). In this work, graphitic carbon nitride was synthesized by the thermal polymerization of urea. which, according to literature data, allows obtaining g-C;N with the highest specific surface area. The obtained photocatalyst showed great potential for the photocatalytic reduction of Cr(VI), under the visible irradiation at pH-3, in the presence of citric acid as a hole scavenger. and the efficiency was not decreased in the second cycle, which is significant for the development of photocatalysis as a method for removing toxie hexavalent chromium from wastewater.

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Catalytic carbon dioxide transformation to low valence carbon molecules such as carbon monoxide, formic acid, methanol and methane is a sustainable way to produce fuels and chemicals. Molecular catalysts can be designed to selectively transform CO2 at mild conditions, but a solvent medium is required. Instead, the molecular catalysts can be immobilized on solid supports to facilitate the continuous flow procedure and the separation of the products to recycle the catalytic systems for a more sustainable process. Photosensitive supports may also favor the light-absorbing steps and electron transfer processes. In this article, the recent results obtained in the photocatalytic CO2 reduction using catalytic systems formed by molecular compounds anchored on solids are reviewed.

Oligonucleotide templated reactions can be used to control the activity of functional molecules based on the presence of a specific trigger sequence. We report an RNA‐controlled reaction system to conditionally restore the N‐terminal amino group and thus binding affinity of azide‐modified Smac mimetic compounds (SMCs) for their target protein X‐linked Inhibitor of Apoptosis Protein (XIAP). Two templated reactions were compared: Staudinger reduction with phosphines and a photocatalytic reaction with Ru(bpy)2(mcbpy). The latter proved faster and more efficient, especially for the activation of a bivalent SMC, which requires two consecutive reduction steps. The templated reaction proceeds with turnover when 2′‐OMe‐RNA probes are used, but is significantly more efficient with PNA, catalyzing a reaction in the presence of low, substoichiometric amounts (1%‐3%, 10 nM) of target RNA., European Research Council, Horizon 2020 Programme, Peer Reviewed

Copper-nickel bimetallic nanoparticles (Cu-Ni BNPs) were fabricated using an eco-friendly green method of synthesis. An extract of synthesized Gazania rigens was used for the synthesis of BNPs followed by characterization employing different techniques including UV/Vis spectrophotometer, FTIR, XRD, and SEM. Spectrophotometric studies (UV-Vis and FTIR) confirmed the formation of bimetallic nanoparticles. The SEM studies indicated that the particle size ranged from 50 to 100 nm. Analysis of the BNPs by the XRD technique confirmed the presence of both Cu and Ni crystal structure. The synthesized nanoparticles were then tested for their catalytic potential for photoreduction of methylene blue dye in an aqueous medium and DPPH radical scavenging in a methanol medium. The BNPs were found to be efficient in the reduction of methylene blue dye as well as the scavenging of DPPH free radicals such that the MB dye was completely degraded in just 17 min at the maximum absorption of 660 nm. Therefore, it is concluded that Cu-Ni BNPs can be successfully synthesized using Gazania rigens extract with suitable size and potent catalytic and radical scavenging activities., Validerad;2021;Nivå 2;2021-09-27 (alebob);Funder: King Saud University, Riyadh, Saudi Arabia (RSP-2021/243)

This paper describes the photocatalytic reduction of aqueous hexavalent chromium (Cr(VI)), a potential human carcinogen and genotoxin, by copper doped TiO2 (Cu-TiO2) prepared by the simple-evaporation and calcination of CuCl2 and TiO2, under UV-A irradiation in the absence of hole scavengers. The Cu-TiO2 prepared at a Cu to TiO2 mass ratio of 1.5:100 and a calcination temperature of 300 °C showed the fastest photocatalytic reduction of Cr(VI). The reduction by the Cu-TiO2 followed pseudo-first order reaction kinetics, and its rate was twice as fast as that of unmodified TiO2 at pH 3. The Cu-TiO2 reached its maximum Cr(VI) reduction rate at pH 5, producing steady state hydrated electron concentrations ([e−]ss) 3.3 times higher than those by unmodified TiO2. The optimum working pH of the Cu-TiO2 is higher than that of many other photocatalysts. The XPS, XRD, TEM and SEM spectra all confirmed the incorporation of Cu into TiO2, and the BET analysis showed the similar surface areas of the Cu-TiO2 and unmodified TiO2. The enhanced reduction rate by the Cu-TiO2 was thus attributed to the reduced electron-hole recombination rate. More importantly, the Cr(VI) reduction rate by the Cu-TiO2 was only reduced by 20% with increasing alkalinity from 0 to 200 mg/L at pH 7, and it was not affected by the presence of NOM at concentrations up to 1 ppm. Lastly, the Cr(VI) reduction rate by the Cu-TiO2 was faster in tap water than in double deionized water. The wider working pH (optimum at pH 5), without addition of hole scavengers, and the faster reduction in tap water suggest the superior performance of the Cu-TiO2 photocatalyst in real water matrices.

In this work we report a highly efficient photocatalytic reduction of Cr(VI) based on PAN-CNT/TiO2-NH2 composite nanofibers fabricated by using electrospinning technique followed by chemical crosslinking of surface modified TiO2 NPs functionalized with amino group. The structure and morphology of the fabricated composite nanofibers were characterized by FTIR, SEM, TEM, TGA, and XPS. The results indicate that the composite nanofibers possess excellent photoreduction performance for Cr(VI) under visible light (125 W) after 30 min, which is much faster than previous reports. The effects of various experimental parameters such as catalyst dose, irradiation time, initial concentration of Cr(VI), and pH on the photoreduction efficiency of Cr(VI) were investigated. The highest photoreduction efficiency of Cr (VI) was obtained at low acidity and low amount of TiO2/CNT photocatalyst. The kinetic experimental data was attained and fitted well with a pseudo-first-order model. The UV–vis spectrophotometer and XPS analyses proved that chromate Cr(VI) was reduced to Cr(III). In addition, it can be concluded that the addition of the phenol enhances the photocatalytic reduction of Cr(VI). Furthermore, the photoreduction mechanism has also been discussed. Finally, the fabricated composite nanofibers were found to be stable after at least five regeneration cycles., QC 20161118

Nanocrystalline C-doped TiO2 hybrid hollow spheres were prepared by solvothermal synthesis by controlling calcinations of mixtures of furfural, chitosan or saccharose with titanium isopropoxide. The origin of the carbon influences the texture, the crystalline framework, and the optical and photoelectrochemistry properties of the TiO2. The results indicate that the carbon–TiO2 hybrid hollow spheres may be used as TiO2-based film electrodes for use in solar cells.

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The solar radiation can be collected and employed in different passive and active technological processes, which include the thermochemical, electrochemical, and photochemical/photobiological routes for production of storable and transportable fuels. Today, the conversion of solar radiation into electric and thermal energy is a reality. Meanwhile, CO2 photocatalytic reduction and the production of solar fuels remain the big challenges for the forthcoming years.

[EN] The shortage of fossil fuels and the need to find alternative renewable and sustainable fuels for transportation are triggering an increasing interest in the photocatalytic reduction of CO 2. In this review, we have focused on titanium containing photocatalysts that effect the reduction of CO 2 to fuels. The various products that are more generally formed are CH 4, CH 3OH, CO as well as HCOOH. This review has been organized primarily depending on the type of titanium material used as the photocatalyst. The list includes pure TiO 2 as well as metal- and non metal-doped titania, noble metals supported on titania and micro-/mesoporous titanosilicates or porous matrices containing titania clusters. In a general introduction we comment on the limitations of the current approaches and the various possibilities and conditions for performing the irradiation. In a final section, we also give our view on future developments and open issues to be addressed in this field. © 2012 The Royal Society of Chemistry.

Photolysis of CO2 at 185 nm using a Hg lamp in the presence of H-2 or H2O leads to the formation of CH4 (after an induction period) and a lesser amount of CO. Using H-2 gas as reducing agent, up to 40% conversion was achieved with almost complete selectivity to methane and energy consumption of 1.55 Gcal/mol. When CO2 irradiation is carried out in the gas phase in the presence of H2O, both reagents can undergo photolysis, and H-2 generation from water is a competing process accompanying the formation of CO and CH4 (CO2 conversion 0.67% at 14 h). For the irradiation of CO2 using H2O as reducing agent, basic solids (K+-exchanged Y zeolite or hydrotalcites) can increase CO2 conversion up to 2.21% with total selectivity toward CH4 and an energy consumption of 4.5 Gcal/mol. This result opens a door in the quest for efficient photocatalysts that could further increase the apparent quantum yield of the process, particularly at longer wavelengths.

Wang, S., Zhang, Z., Huo, W., Zhu, K., Zhang, X., Zhou, X., ... & Jiang, J. (2020). Preferentially oriented Ag-TiO2 nanotube array film: An efficient visible-light-driven photocatalyst. Journal of Hazardous Materials, 399, article 123016. https://doi.org/10.1016/j.jhazmat.2020.123016

Wang, S., Zhang, Z., Huo, W., Zhang, X., Fang, F., Xie, Z., & Jiang, J. (2021). Single-crystal-like black Zr-TiO2 nanotube array film: An efficient photocatalyst for fast reduction of Cr (VI). Chemical Engineering Journal, 403, article 126331. https://doi.org/10.1016/j.cej.2020.126331