Semiconductor metal-substituted tin oxide (SnO₂) has drawn a great deal of attention due to its excellent properties. This study focuses on the photocatalytic properties of 3d transition metals, specifically manganese (Mn) and iron (Fe), emphasizing the role of unpaired electrons in enhancing photocatalytic activity. A Sn_0.99-Mn_0.05-Fe_0.05O₂ sample was synthesized by the sol–gel wet chemical precipitation method. The crystallite size and structure of doped SnO₂ were determined usinga modified Debye Scherer’s formula. Lattice constants were evaluated from peaks obtained by the X-ray diffraction (XRD) technique. The value of crystallite size estimated by Debye Scherer’s formula lies in the range 3–5 nm, indicating the nano-crystalline nature of the sample. Using transmission electron microscopy (TEM), the obtained average diameter was 3.75 nm, calculated with the help of ImageJ, which is in good agreement with the crystallite size obtained via XRD. The irregular morphology of the sample was analyzed by field emission scanning electron microscopy (FESEM). An energy dispersive X-ray (EDX) analysis confirmed the presence of elements such as tin, oxygen, manganese and iron. Fourier transform infrared (FT-IR) spectrum displayed Sn-O characteristic bands as well as inculcated metal elements. The optical and photocatalytic results were characterized using UV-Visible spectroscopy. The absorbance for pristine and intercalated samples was observed at 217 nm and 218 nm, respectively. Their optical band gaps were 3.10 eV and 2.69 eV, respectively, indicating that the band gaps narrow upon intercalation. Photoluminescence spectra were obtained in the visible spectrum range (300–600 nm) and confirmed the defects and impurity states formed due to the intercalation of Mn and Fe transition elements. The photocatalytic activity results revealed that Mn-Fe/SnO₂ has a better photocatalytic performance of methylene blue (MB) dye solutioncompared to pristine SnO₂.

This study is concerned with the photocatalytic degradation of rose bengal dye using modified titanium dioxide, specifically using different metal ions, like manganese (Mn) and cobalt (Co). The TiO₂/Mn/Co composites were prepared via a sol–gel route since it favors the homogenous introduction of metal ions into the TiO₂ matrix. For the preparation of the composites, titanium dioxide (0.89 mol) was mixed with manganese (II) chloride (0.05 mol) and cobalt chloride hexahydrate (0.06 mol). The structural and morphological properties of the synthesized photocatalysts were assessed by characterization techniques such as X-ray diffraction (XRD) and transmission electron microscopy (TEM), Fourier-Transform Infrared (FT-IR) and UV-VIS spectroscopy. The average particle size was found to be 74.8 nm, which was calculated using image J software, and the interplanar d-spacing was 0.3567 nm, as calculated from HR-TEM images. The TEM images also revealed the spherical morphology of the composite. Optical studies have revealed the narrowed band gap of the TiO₂/Mn/Co nanocomposite. Photocatalytic performance under sunlight was evaluated, indicating enhancement in the efficiency of rose bengal degradation compared to pure TiO₂ through the incorporation of manganese and cobalt. The degradation efficiency was 92% in the case of TiO₂ and increased to 94% with the TiO₂/Mn/Co nanocomposite. The suggested mechanism for the degradation process, through the generation of reactive oxygen species during sunlight irradiation, elucidates an essential role of the latter in breaking down the molecular structure of the dye. Overall, these results prove that TiO₂/Mn/Co composites may have the potential to offer an effective solution for dye removal from wastewater, thereby making a positive contribution towards environmental sustainability.

Rapid industrial growth has led to a serious pollution problem, primarily due to the discharge of wastewater containing significant amounts of organic pollutants, such as dyes, oils, and solvents. Among these, water pollution caused by dye-contaminated wastewater is particularly concerning. Conventional treatment methods have proven inadequate for the effective removal of dyes from wastewater. Sunlight-assisted photocatalysis has emerged as a promising approach for eliminating toxic organic substances from aqueous media. In this study, we report the development of ZnO-decorated graphene oxide (ZnO-GO) as a photocatalyst for the degradation of Sandalfix Orange P3R and Sandalfix Turquoise Blue PG dyes under sunlight irradiation. Graphene oxide was synthesized using the Hammer and Offeman method, and ZnO-GO composites were prepared via chemical reduction in a 1:1 ratio. The synthesized ZnO-GO was characterized using XRD, TEM, DR-UV-Vis, FTIR, and surface area analysis. Its photocatalytic performance was evaluated for the degradation of the two dyes. More than 95% of 100 mg/L (50 mL) of each dye was successfully degraded within 120 minutes of reaction time. ZnO-GO exhibited 2.2- and 1.9-fold higher catalytic activity in degrading Sandalfix Orange P3R and Sandalfix Turquoise Blue PG dyes, respectively, compared to graphene oxide and ZnO alone. This enhanced activity is attributed to the efficient transfer of photo-induced electrons through the graphene sheets, which play a crucial role in preventing the recombination of positive holes and electrons, thereby significantly improving photocatalytic performance.

Titanium dioxide (TiO₂) nanoparticles have become an exceptionally effective photocatalyst for the degradation of organic dyes in wastewater treatment. This breakthrough has been related to the distinctive physicochemical features inherent to these nanoparticles. These characteristics include a substantial surface area, remarkable chemical stability, and a potent oxidative capacity upon exposure to ultraviolet (UV) radiation, making TiO₂ a great photocatalyst. This work examines processes involving photocatalytic activity in TiO₂, focusing on the production of reactive oxygen species (ROS) via the formation of electron–hole pairs via photoinduced reactions. This research focuses on significant parameters that affect photocatalytic performance. These factors include particle size, crystal phase (anatase, rutile, or brookite), surface changes, and doping with metals or non-metals to enhance visible light absorption. This paper examines current improvements in TiO₂ nanoparticle production methods and their effects on the effectiveness of photocatalytic processes. An examination of the applications of TiO₂ for the degradation of synthetic dyes, including methylene blue, rhodamine B, and azo dyes, is conducted to highlight its potential to mitigate environmental issues caused by industrial dye pollution. Ultimately, challenges such as the fast recombination of charge carriers and the diminished efficacy of visible light are acknowledged, with several solutions suggested to mitigate these issues. This study seeks to elucidate the function of TiO₂ nanoparticles in dye degradation and to provide a foundation for future research aimed at producing more efficient and ecologically sustainable photocatalytic systems.

Photocatalysts are vital for tackling environmental crises; however, their poor solar-energy utilization is a bottleneck. Herein, N-doped titania (N/TiO₂) nanomaterials were successfully synthesized using a facile sol–gel technique. The importance of the annealing gases' environment on physicochemical properties and photocatalytic efficiency under sunlight was examined. Spectroscopy data revealed that the spheroidal N/TiO₂ crystals were transformed from monophase anatase with less crystallinity to dual-phase anatase/rutile (A/R) with higher crystallinity in argon/nitrogen and air, respectively. Moreover, XPS confirmed the incorporation of interstitial nitrogen in the bare titania structure; this introduction not only led to a red shift towards visible light but also lowered the bandgap energy (2.35 eV) and suppressed charge-carrier recombination according to DRS and PL results. Furthermore, they showed a typical IV isotherm of mesoporous nanomaterials with a high surface area, up to 103 m²/g. Particularly, their rhodamine B photodegradation and thermal stability were dictated by the annealing gas type. Notably, the N/TiO₂ prepared in air demonstrated the highest degradation performance of 99% with the fastest rate of 0.0158 min^-1, which is twice faster than the control TiO₂. This improved performance is mostly attributed to its higher crystallinity, A/R mixed phase, aqueous-dispersion character, and lower charge recombination. Such a gas-driven synthesis of catalysts has practical applications in designing other solar-energy conversion systems.

Merging photoredox and catalysis by transition metals, coined as metallaphotoredox catalysis, has proven to be an excellent new platform for the development of new synthetic strategies for the formation of carbon–carbon and carbon–heteroatom bonds [1]. In this presentation, we will present a dual catalytic system that has been successfully developed for the ligation of azides with alkynes to yield 1,4-disubstituted-1,2,3-triazoles in a resgioselective manner. Our strategy consists of merging decatungstate anion [W₁₀O₃₂]^4- photocatalysis in the presence of a hydrogen donor solvent to reduce the Cu(II) precursor into the catalytically active species Cu(I), consequently starting a copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC).

The resulting bifunctional H⁺[W₁₀O₃₂]⁵⁻/Cu(I) catalytic system operates efficiently in an environmentally benign water–ethanol solvent mixture as a reaction medium, producing only 1,4-disubstituted-1,2,3-triazole derivatives with high yields of up to 99% under mild conditions. This metallaphotoredox approach can be applied to a large range of substrates and large-scale reactions. To prove the sustainability of this dual catalytic process, CuAAC was performed under sunlight exposure too [2].

References

[1] P. J. Sarver, V. Bacauanu, D. M. Schultz, D. A. DiRocco, Y. Lam, E. C. Sherer, D. W. C. MacMillan, Nat. Chem. 2020, 12, 459.

[2] S.-E. Stiriba, N. Aflak, E. M. El Mouchtari, H. Ben El Ayouchia, S. rafqah, H. Anane, M. Julve, Appl Organomet Chem. 2023; 37:e7175.

This study explores the development of cost-effective photocatalysts based on Prussian Blue (Iron(III) Hexacyanoferrate(II)) and its analogues (Cobalt(II) Hexacyanoferrate(II), Iron(III) Hexacyanocobaltate(III), and Cobalt(II) Hexacyanocobaltate(III)) combined with commercial anatase nanoparticles (particle size <25 nm, purity 99.7%) for UV-driven degradation of aqueous methylene blue (MB) solutions. The materials were characterized using XRF, FTIR, SEM, and XRD, confirming the successful formation of side-by-side composites without core@shell morphology. The formation of heterojunctions remains inconclusive.

Photocatalytic experiments demonstrated that the composites achieved high decolorization efficiencies (80–90%), significantly outperforming pure anatase (<25%). However, total organic carbon (TOC) analysis revealed only partial mineralization, with MB content reducing minimally (64.5 mg/L to 62.12 mg/L) under irradiation with a xenon and mercury UV lamp. Importantly, no bleaching of MB solutions occurred with pure Prussian Blue or its analogues alone.

Ecotoxicological assays using Scaptotrigona postica bees revealed that the photodegraded dye solution exhibited reduced toxicity compared to untreated MB, as evidenced by lower mortality risks (HR = 0.8973) and longer median lethal times (TL50 = 12 days vs. 11 days for untreated dye). Stingless bees exposed to untreated MB faced higher mortality risks (HR = 0.6161), emphasizing the ecological risks of untreated dyes.

Therefore, it is imperative to continue studying the development of innovative and sustainable photocatalytic systems, focusing on Prussian Blue composites, their efficient reuse, and their coupling with hydrogen peroxide and/or persulfate, to advance water treatment and the remediation of dyes in an economically viable and environmentally friendly manner.

Hydrosilation, a reaction between silane (Si-H) and vinyl groups, is leveraged in the manufacture of release coatings. However, cross-linking requires high temperatures, leading to this process being generally regarded as time- and energy-intensive. In recent decades, photopolymerization has emerged as an environmentally conscious alternative and is actively being explored due to the advantage that it is a low-temperature cross-linking process. The performance of UV-activated Pt hydrosilation catalysts can be assessed relative to industry-standard MeCpPtMe₃ (Pt-99) by monitoring the cross-linking of model silanes as ultra-thin (2-3 µm thick) films via an industrially relevant novel ATR-FTIR strategy. This strategy improves upon previous methods, in which ≥100 µm thick films are monitored via transmission mode FTIR. The percentage of the hydride consumed after the initial LED excitation (? = 365, 400 nm) was determined by monitoring the bending mode of the Si-H bond relative to an unchanging Si-C stretching mode present in both silicone fluids. This allowed for the generation of percent conversion versus dark cure reaction time plots, as well as the calculation of kinetic parameters including the initial rate, rate constant, and final percent conversion. Eco-inspired innovations inthe curing process will produce novel Pt(IV) photocatalysts that can be evaluated against the current benchmark, with the potential to create UV-cured release coatings on a cost-competitive scale to those cured thermally.

Numbering-up is a strategy used to scale up microchemical processes by distributing fluids in microchannels, used as microreactors, which allows efficient mass transport under laminar flow conditions. Due to the reduced diffusion path from the aqueous solution of the contaminant to the catalyst layer, mass transport limitations are reduced, which easuky overcomes one of the main drawbacks of catalyst immobilization.
In this work, the efficiency of a continuous-flow photo-microreactor with TiO2 supported on a silicone column and irradiated by UVA-LED was evaluated, considering the effects of its operating conditions on the degradation of two endocrine disruptors, BPA and DBP.
The experimental design was 2k and considered pH, temperature, H2O2 concentration, and volumetric flow rate as the process variables. The controlled reaction included equipment, such as injection pumps, peltier, pressure control, and online sensors (pH, ORP, NMR 1H). The output variables were the photocatalytic efficiency of the reactor, assessed through reaction monitoring by NMR-1H, IR, UV-Vis, and TOC. Variations in Reynolds numbers were measured from the viscosity of the solutions at the set up and end of the reactions.
The optimal operational parameters for BPA degradation were pH = 4, T = 20 ° C, Q = 1 mL/min, and [H2O2] = 2 ppm, while, with a reaction time of 0.25 h, a higher degradation efficiency of BPA (99.3%) was achieved. For the same reaction conditions, the highest degradation efficiency of DBP was 78%.
The use of a continuous-flow microreactor supported by TiO2 is a potential method for the treatment of wastewater contaminated by endocrine disruptors.

To address environmental concerns, solar-driven photocatalytic processes are proposed for the removal of anthropogenic pollutants. The textile industry's wastewater, rich in emerging organic pollutants, including dyes, is a primary target for this approach.

Carbon nitride (C₃N₄) is a low-cost semiconductor material that can absorb light in the visible solar spectrum, in addition to being easy to manufacture, non-toxic, and biodegradable. The nanoparticles of this material possess optical and electronic properties associated with their nanoscale structure. To overcome its own limitations, strategies have been designed that consider modification with metals, such as iron. In this context, carbon nitride particles (CN) were synthesized from the calcination of urea. Then, the CN were modified by applying the calcination and impregnation methods with the Fe (II) salt (CNFe (II)c and (CNFe (II)i, respectively).

The synthesized catalysts were characterized by IR-ATR. UV–vis absorption spectra and the zeta potential of the aqueous suspensions were determined. Time-resolved as well as steady-state photoluminescence measurements were measured. Total organic carbon (TOC) and some other characterization techniques were applied to obtain more information on the material.

The photocatalytic properties of each material were evaluated using methyl orange (MO) as a model contaminant and 350 nm monochromatic light. In all cases, samples were taken periodically, and UV–visible spectroscopy was used to monitor the concentration of MO. The MO removal percentages indicate that CNFe (II)i exhibits a significantly higher MO removal efficiency compared to unmodified CN and CNFe (II)c under identical experimental conditions.

Based on the obtained results, a future study is proposed to investigate the mechanisms involved in MO degradation. This will provide a deeper understanding of the results and lay the groundwork for future studies related to the toxicity of the reaction mixture after each treatment of the treated samples, as well as the implementation of other contaminants.