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The aim of this study is to clarify the effect of doped metal type on CO2 reduction characteristics of TiO2 with NH3 and H2O. Cu and Pd have been selected as dopants for TiO2. In addition, the impact of molar ratio of CO2 to reductants NH3 and H2O has been investigated. A TiO2 photocatalyst was prepared by a sol-gel and dip-coating process, and then doped with Cu or Pd fine particles by using the pulse arc plasma gun method. The prepared Cu/TiO2 film and Pd/TiO2 film were characterized by SEM, EPMA, TEM, STEM, EDX, EDS and EELS. This study also has investigated the performance of CO2 reduction under the illumination condition of Xe lamp with or without ultraviolet (UV) light. As a result, it is revealed that the CO2 reduction performance with Cu/TiO2 under the illumination condition of Xe lamp with UV light is the highest when the molar ratio of CO2/NH3/H2O = 1:1:1 while that without UV light is the highest when the molar ratio of CO2/NH3/H2O = 1:0.5:0.5. It is revealed that the CO2 reduction performance of Pd/TiO2 is the highest for the molar ratio of CO2/NH3/H2O = 1:1:1 no matter the used Xe lamp was with or without UV light. The molar quantity of CO per unit weight of photocatalyst for Cu/TiO2 produced under the illumination condition of Xe lamp with UV light was 10.2 μmol/g, while that for Pd/TiO2 was 5.5 μmol/g. Meanwhile, the molar quantity of CO per unit weight of photocatalyst for Cu/TiO2 produced under the illumination condition of Xe lamp without UV light was 2.5 μmol/g, while that for Pd/TiO2 was 3.5 μmol/g. This study has concluded that Cu/TiO2 is superior to Pd/TiO2 from the viewpoint of the molar quantity of CO per unit weight of photocatalyst as well as the quantum efficiency.

Legionella pneumophila (L. pneumophila) is the causative agent of Legionnaires’ disease and Pontiac fever, collectively known as legionellosis. L. pneumophila infection occurs through inhalation of contaminated aerosols from water systems in workplaces and institutions. The development of disinfectants that can eliminate L. pneumophila in such water systems without evacuating people is needed to prevent the spread of L. pneumophila. Photocatalysts are attractive disinfectants that do not harm human health. In particular, the TiO2 photocatalyst kills L. pneumophila under various conditions, but its mode of action is unknown. Here, we confirmed the high performance of TiO2 photocatalyst containing PtO2 via the degradation of methylene blue (half-value period: 19.2 min) and bactericidal activity against Escherichia coli (half-value period: 15.1 min) in water. Using transmission electron microscopy, we demonstrate that the disinfection of L. pneumophila (half-value period: 6.7 min) by TiO2 photocatalyst in water is accompanied by remarkable cellular membrane and internal damage to L. pneumophila. Assays with limulus amebocyte lysate and silver staining showed the release of endotoxin from L. pneumophila due to membrane damage and photocatalytic degradation of this endotoxin. This is the first study to demonstrate the disinfection mechanisms of TiO2 photocatalyst, namely, via morphological changes and membrane damage of L. pneumophila. Our results suggest that TiO2 photocatalyst might be effective in controlling the spread of L. pneumophila.

SARS-CoV-2 is the causative agent of COVID-19, which is a global pandemic. SARS-CoV-2 is transmitted rapidly via contaminated surfaces and aerosols, emphasizing the importance of environmental disinfection to block the spread of virus. Ultraviolet C radiation and chemical compounds are effective for SARS-CoV-2 disinfection, but can only be applied in the absence of humans due to their toxicities. Therefore, development of disinfectants that can be applied in working spaces without evacuating people is needed. Here we showed that TiO2-mediated photocatalytic reaction inactivates SARS-CoV-2 in a time-dependent manner and decreases its infectivity by 99.9% after 20 min and 120 min of treatment in aerosol and liquid, respectively. The mechanistic effects of TiO2 photocatalyst on SARS-CoV-2 virion included decreased total observed virion count, increased virion size, and reduced particle surface spike structure, as determined by transmission electron microscopy. Damage to viral proteins and genome was further confirmed by western blotting and RT-qPCR, respectively. The multi-antiviral effects of TiO2-mediated photocatalytic reaction implies universal disinfection potential for different infectious agents. Notably, TiO2 has no adverse effects on human health, and therefore, TiO2-induced photocatalytic reaction is suitable for disinfection of SARS-CoV-2 and other emerging infectious disease-causing agents in human habitation.

Contamination of water resources by organic pollutants is a major environmental issue. Utilizing photocatalytic materials for the degradation of these pollutants presents a viable strategy for environmental clean-up. This study introduces the synthesis of an organic/inorganic hybrid photocatalyst of β-cyclodextrin (β-CD)/reduced graphene oxide (rGO) and titanium oxide (TiO2) nanoparticles. The nanocomposite was characterized by using FT-IR, XRD, SEM, and EDAX, and the photocatalytic activity was studied by measuring the photodegradation of methylene blue (MB) under simulated solar radiation. The synthesized nanocomposite showed excellent stability and performance, with up to 92% photodegradation of MB. To further enhance the photocatalytic activity, the synthesized nanocomposite underwent modification with Ag and Pt nanoparticles. Within 90 min, photodegradation rates of 100% and 97% for MB were attained with Pt and Ag nanoparticles that were loaded at 5 wt.%, respectively. The photocatalyst’s reusability was evaluated through multiple usage cycles. Additionally, the impact of functionalization on the band gap alteration of TiO2 is reported.

Water decontamination still remains a major challenge to some developing countries not having centralized wastewater systems. Therefore, this study presents the optimization of photocatalytic degradation of Basic Blue 41 dye in an aqueous medium by an activated carbon (AC)-TiO2 photocatalyst under UV irradiation. The mesoporous AC-TiO2 synthesized by a sonication method was characterized by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy for crystal phase identification and molecular bond structures, respectively. The efficiency of the AC-TiO2 was evaluated as a function of three input variables viz. catalyst load (2–4 g), reaction time (15–45 min) and pH (6–9) by using Box-Behnken design (BBD) adapted from response surface methodology. Using color and turbidity removal as responses, a 17 run experiment matrix was generated by the BBD to investigate the interaction effects of the three aforementioned input factors. From the results, a reduced quadratic model was generated, which showed good predictability of results agreeable to the experimental data. The analysis of variance (ANOVA), signposted the selected models for color and turbidity, was highly significant (p < 0.05) with coefficients of determination (R2) values of 0.972 and 0.988, respectively. The catalyst load was found as the most significant factor with a high antagonistic impact on the process, whereas the interactive effect of reaction time and pH affected the process positively. At optimal conditions of catalyst load (2.6 g), reaction time (45 min), and pH (6); the desirability of 96% was obtained by a numerical optimization approach representing turbidity removal of 93% and color of 96%.

This article presents an integrated strategy that couples high-efficiency photocatalytic degradation with low-cost, rapid detection to overcome the main drawbacks of conventional TiO2-based photocatalysts, including a weak visible-light response, rapid charge–carrier recombination, and reliance on expensive instrumentation for dye concentration detection. Platinum-decorated TiO2 (Pt/TiO2) was prepared by photoreduction deposition, and systematic characterization confirmed the successful loading of zero-valent Pt nanoparticles onto the TiO2 surface, significantly improving charge separation and extending absorption into the visible region. Methylene blue degradation was quantified under ultraviolet (UV) and simulated sunlight; radical-scavenging tests clarified the reaction pathway. In parallel, smartphone images of the reaction mixture were processed in ImageJto extract red–green–blue (RGB) values, which were related to dye concentration through a partial least-squares (PLS) model validated against reference UV–Vis data. Pt/TiO2 removed 95.0% of methylene blue within 20 min of UV irradiation and 90.2% within 160 min of simulated sunlight—31.8% and 19.1% faster, respectively, than pristine TiO2. The RGB-based PLS model achieved a coefficient of determination (R2) of 0.961 for the prediction set. By integrating photocatalysis with smartphone-based colorimetry, the proposed method enables rapid monitoring of organic dyes concentration, providing an intelligent and economical platform for industrial wastewater treatment.

Recently, there has been a growing interest in rare sugars due to their potential applications in functional foods and pharmaceuticals. However, sustainable production methods for these compounds remain challenging due to their high cost, lengthy production times, and environmentally harmful reagents. Herein, we report a novel photocatalytic approach for synthesizing rare disaccharides from maltose, an abundant and renewable natural resource, under mild conditions at room temperature and atmospheric pressure using light as the energy source. The photocatalytic treatment of maltose using platinum compound-supported titanium oxide (PtCl/TiO₂) resulted in the formation of rare disaccharides, primarily 3- O -α- d -glucopyranosyl- d -arabinose and glucosyl-erythrose, which were characterized by HPLC, LC/MS, 13 C NMR spectroscopy, and optical rotation measurements. Notably, biological evaluation of 3- O -α- d -glucopyranosyl- d -arabinose using HeLa and HEK293 cells demonstrated no cytotoxicity and negligible cellular uptake. Furthermore, enzymatic degradation studies using mouse intestinal α-glucosidase revealed significantly lower degradability compared to maltose, with minimal glucose production observed. These findings suggest that 3- O -α- d -glucopyranosyl- d -arabinose exhibits resistance to digestion and absorption in mammalian systems, highlighting its potential application as a low-calorie sweetener and a functional food ingredient. This study presents an environmentally benign synthetic route to rare disaccharides and demonstrates their promising biological properties.

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO2/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm2 and an air flow rate of 55 m3/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology.

The biochar treated through several processes can be modified and utilized as catalyst or catalyst support due to specific properties with various available functional groups on the surface. The functional groups attached to the biochar surface can initiate active radical species to play an important role, which lead to the destruction of contaminants as a catalyst and the removal of adsorbent by involving electron transfer or redox processes. Centering on the high potential to be developed in field applications, this paper reviews more feasible and sustainable biochar-based materials resulting in efficient removals of environmental pollutants as catalyst or support rather than describing them according to the technology category. This review addresses biochar-based materials for utilization as catalysts, metal catalyst supports of iron/iron oxides, and titanium dioxide because the advanced oxidation process using iron/iron oxides or titanium dioxides is more effective for the removal of contaminants. Biochar-based materials can be used for the removal of inorganic contaminants such as heavy meals and nitrate or phosphate to cause eutrophication of water. The biochar-based materials available for the remediation of eutrophic water by the release of N- or P-containing compounds is also reviewed.

This study investigated the impact of molar ratio of CO2 to reductants H2O and H2, as well as Pd loading weight on CO2 reduction performance with Pd/TiO2 as the photocatalyst. The Pd/TiO2 film photocatalyst is prepared by the sol-gel and dip-coating process to prepare TiO2 film and the pulse arc plasma method is used to dope Pd on TiO2 film. The prepared Pd/TiO2 film was characterized by SEM, EPMA, STEM, EDS, and EELS. This study also investigated the performance of CO2 reduction under the illumination condition of Xe lamp with or without ultraviolet (UV) light. As a result, it is revealed that when the molar ratio of CO2/H2/H2O is set at 1:0.5:0.5, the best CO2 reduction performance has been obtained under the illumination condition of Xe lamp with and without UV light. In addition, it is found that the optimum Pd loading weight is 3.90 wt%. The maximum molar quantities of CO and CH4 produced per unit weight of photocatalyst are 30.3 μmol/g and 22.1 μmol/g, respectively, for the molar ratio of CO2/H2/H2O = 1:0.5:0.5 under the condition of Xe lamp illumination with UV light. With UV light, C2H4 and C2H6, as well as CO and CH4 are also produced by the Pd/TiO2 film photocatalyst prepared in this study.