Journal of Photochemistry and Photobiology A-chemistry最新文献

Given Cr(VI) is a ubiquitous water pollutant posing significant public health risks, there is a need for an inexpensive and easy-to-use detection tool. Herein, a diatom frustule-supported Fe₃O₄ (DF-Fe₃O₄) with enhanced oxidoreductase mimetic activity is reported for direct colorimetric detection of Cr(VI). Unlike the peroxidase nanozymes which are often reported for colorimetric detection, DF-Fe₃O₄ triggered a chromogenic redox reaction between TMB and Cr(VI) without requiring H₂O_2. This enables direct redox reactions while circumventing potential interferences associated with the use of H₂O_2. DF-Fe₃O₄ was synthesized with a coprecipitation method and subsequently characterized by SEM, XRD, and XPS techniques, revealing the distribution of Fe₃O₄ NPs on the frustule matrix. The frustule obtained from Nitzschia sp. of a sediment sample rendered a robust catalytic support enhancing the oxidoreductase activity of pristine Fe₃O₄ NPs by 20.8 %. Further, the nanozyme maintains 73 % of its activity even at 95 °C while losing only 33 % of its activity after one month of storage. The oxidoreductase mimetic activity was evaluated using the chromogenic redox reaction between TMB and Cr(VI) which rapidly forms a blue color (${\lambda }_{\max }=$ 654 nm), where its intensity forms the basis of the colorimetric detection. With a K_m value of 0.058 mM, the nanozyme was able to selectively detect Cr(VI) down to 0.21 µM with a linear range between 0.1–500 µM. Recoveries from spiked wastewater samples were between 91.14–102.20 %. The obtained analytical figures of merits demonstrated the applicability of the developed sensor for Cr (VI) analysis devoid of complex instrumentation in the established analytical methods.

Efficient ternary BiVO₄/g-C₃N₄/diatomite (BCNDE) composites were prepared using a strategy combining in situ polymerisation and self-assembly. The photocatalytic degradation efficiencies of BCNDE composites for rhodamine B (RhB) and formaldehyde (CH₂O) were investigated. Compared with BiVO₄ (BVO), g-C₃N₄ (CN) and BiVO₄/g-C₃N₄ (BCN), BCNDE showed better photocatalytic performance for RhB and CH₂O degradation. Notably, the 20-BCNDE composite demonstrated superior photocatalytic performance, achieved 99 % degradation of RhB under visible light (λ > 400 nm) within 60 min and 81 % degradation of CH₂O gas (0.16 mg·L⁻¹) within 40 min. Incorporation of porous microdisc-shaped diatomite (DE) significantly mitigated the agglomeration of the BCNDE composites, as confirmed by scanning electron microscopy (SEM). This structural feature enhanced the separation and migration of photogenerated electron-hole pairs, as evidenced by photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy (EIS) analyses. Zeta potential analysis at pH 7 revealed a negatively charged surface with a zeta potential of −8.9 mV, facilitating the attraction of photogenerated holes and inhibiting electron-hole recombination. This effectively inhibited the recombination rate of photogenerated electron-hole pairs, thereby significantly improving the photocatalytic performance of the material. These mechanisms were critical in boosting the photocatalytic degradation activities for RhB and CH₂O. This study highlights the potential of BCNDE composites for environmental remediation applications, offering a promising approach for the development of efficient mineral-based photocatalytic materials.

Here we present a practical, mild, selective, eco-friendly, metal-free, cost-effective, and tunable method for the photoactivation of C-H compounds using an organo photocatalyst without any additives. For this purpose, the organo photocatalyst DDQ was employed as a versatile and highly efficient catalyst for C-H bond functionalization under visible light irradiation in a straightforward reaction setup, free from additives and co-catalysts. Notably, under appropriate solvent conditions, the photooxidation of alkylarenes produced ketones, aldehydes, and carboxylic acids from corresponding starting materials. In CH₃CN solvent, carboxylic acids were obtained. Interestingly over oxidation to carboxylic acid is avoided and aldehydes were produced from methyl arenes via acetal formation in CH₃CN:MeOH. Furthermore, our results demonstrated that the photooxidation of 4-methoxytoluene was more efficient than that of 4-methoxybenzylalcohol. The proposed mechanism for this reaction involved the formation of a charge transfer complex between the starting material and DDQ, as indicated by UV–Vis and fluorescence spectra. Also, this method exhibited promising scalability, with 30 mmol of 4-methoxytoluene being converted to 4-methoxybenzoic acid with a yield of 92 % (TON: 345).

Developing and evaluating advanced antibiotic degradation photocatalysts remains challenging owing to the lack of rational structural designs and molecular oxygen activation. In this study, a nanofluoral-biochar-modified bismuth vanadate (m-BiVO₄) material with a specific structure was prepared via surface-assisted polymerization. The results show that the yeast-derived carbon material significantly broadened the capture range of n–p* visible light and improved the electron delocalization and carrier separation rates. Under visible light irradiation, m-BiVO₄ exhibited a high photocatalytic degradation rate, and the degradation rate of 10 mg/L tetracycline (TC) reached 89.9 % within 180 min, almost three times that of the control group. An EPR test and free radical capture experiment showed that ·OH and ·O₂^– were the main active substances in the TC degradation process. Cyclic experiments also showed that the material had great stability and potential for reuse. The intermediate in the degradation pathway was identified using liquid chromatography-tandem mass spectrometry, the degradation pathway of TC in the composite system was predicted, and a corresponding degradation pathway was proposed. In this study, the synergistic effect of morphology adjustment and component cutting was realized using biomass templates, providing a new method for designing photocatalysts with specific structures.

The Fe²⁺/Fe³⁺ redox cycle is the rate-determining step of hydroxyl radical formation in the photo-Fenton system. In this research, methyl orange (MO) was used which was degraded using Fe₃O₄/g-C₃N₄ in photocatalysis and photo-Fenton systems. The influence of wavelength irradiation on the redox cycle of Fe²⁺/Fe³⁺ ions was investigated. The results showed that the MO degradation rate constant reached 0.152 min⁻¹ in photo-Fenton and 0.090 min⁻¹ in photocatalysis using UV–vis light, which is 50 and 30 times higher than Fenton system. Light irradiation affects iron-leaching process and iron photoreduction. The iron leaching occurs more frequently at high energies and does not occur at λ ≥ 420 nm. In photo-Fenton, interaction between H₂O₂ and Fe₃O₄ surface makes the leaching process easier to occur. The photoreduction results show that the effective conversion of Fe³⁺ to Fe²⁺ occurs at λ ≥ 380 nm with the percentage of Fe²⁺ reaching ∼90 % in both systems.

A novel photo-responsive azobenzene-based amphiphilic small molecule (mAzoNa) with four methoxy groups located at ortho positions on azobenzene unit has been designed and synthesized. The mAzoNa molecules could self-assemble into hydrogel, which was driven mainly by hydrophobic effect and π–π stacking interaction between substituted azobenzene groups. The formed hydrogel was composed of long (∼several micrometers) lamellar ribbon structures with widths of 150 to 500 nm. The hydrogel also showed good self-supporting ability with a storage modulus (G′) higher than 10⁴ Pa. It was more interesting that the hydrogel could undergo reversible gel-to-sol transition under 550 nm green light irradiation and the sol-to-gel transition under 450 nm blue light irradiation. This could be attributed to that the substituted four methoxy groups red-shifted the isomerization wavelengths of mAzoNa. This unique visible-light responsive behavior should make the prepared hydrogel find more potential applications in biomedical systems and smart materials without using ultraviolet light at all.