Construction of PDIsa/BiOBr type-I scheme heterojunction for efficient ciprofloxacin photocatalytic degradation

Fabrication of heterojunction photocatalysts is a promising strategy for enhancing photocatalytic activity. However, the study about traditional type-I heterojunction still remains to be developed. Herein, a PDIsa/BiOBr traditional type-I heterojunction was constructed by electrostatic self-assembly method, which owned improved light absorption capacity and photogenerated charge separation efficiency. The interfacial electric field and the polarization electric field of PDIsa impelled the separation of excitons. The degradation rate of ciprofloxacin (CIP) was improved by 3.2 times over the optimal PDIsa/BiOBr composite than pure BiOBr. In addition, the TOC removal efficiency reached 67.34% within 120 min. Trapping experiments and electron spin resonance (ESR) tests showed that superoxide radical (•O₂^-) was the most active species, and singlet oxygen (¹O₂) and hole (h⁺) played a secondary role. The work may furnish a new reference for designing BiOBr-based type-I heterojunction.

Keggin Cluster Modulated Photocatalytic Activity of Aryl Sulfonium Polyoxometalate Hybrids toward Dichromate Reduction

Dichromate (Cr₂O₇^2-) ion having chromium in its +6 oxidation state is a carcinogen and a potential threat to humans and aquatic life. The photocatalytic reduction of toxic Cr(VI) species into less toxic Cr(III) is an important target in heterogeneous catalysis. In this work, the catalytic activities of a series of Keggin cluster-based aryl sulfonium polyoxometalate hybrids, (FPDS)₃[PMo₁₂O₄₀] (1), (FPDS)₃[PW₁₂O₄₀] (2), (FPDS)₄[SiMo₁₂O₄₀] (3), and (FPDS)₄[SiW₁₂O₄₀] (4), toward the photocatalytic reduction of Cr(VI) have been analyzed and compared. Here, we used the aryl sulfonium counterions to modulate the POM cluster's solubility in water and stabilize the photogenerated e^--h⁺ pair on the cluster. All of the hybrids 1-4 catalyzed the reduction of Cr(VI) to Cr(III) under ultraviolet (UV) irradiation, and their photocatalytic efficiencies followed the order hybrid 1 > hybrid 3 > hybrid 2 > hybrid 4, with the rate-constant values of 0.048, 0.0056, 0.0035, and 0.0028 min^-1, respectively. Hybrid 1 with [PMo₁₂O₄₀]^3- Keggin cluster exhibited the best photocatalytic activity in the series yielding a 99% reduction in 120 min. The reasons behind the best photocatalytic activity of hybrid 1 are identified as its low band gap, less charge recombination, and fast photoresponse. The electron-trapping analyses performed using AgNO₃ revealed electrons as the main reactive species responsible for the photocatalytic reduction of Cr(VI). A plausible photocatalytic mechanism has also been proposed based on electron-trapping experiments. The present study shows that aryl sulfonium Keggin hybrids can function as efficient photocatalysts for Cr(VI) reduction, and their catalytic efficiency varies with the nature of the Keggin cluster.

Bimetal (Fe/Zn) doped BiOI photocatalyst: An effective photodegradation of tetracycline and bacteria

Tetracycline (TC) is one of the most commonly used broad-spectrum antibiotics to treat the bacterial infection. TC antibiotics enter into the environment because of partial metabolism in the humans and animals, thereby increasing the environmental toxicity. Therefore, it is highly needed to treat TC antibiotics from the water system. In this aspect, the present work focus on the synthesis of Fe and Zn (bimetal) incorporated with different concentrations into the bismuth-oxy-iodide (Fe/Zn-BiOI) based photocatalyst materials. The synthesized Fe/Zn-BiOI was tested against photocatalytic degradation of TC antibiotics and bacteria. The band gap value of the synthesized Fe/Zn-BiOI was calculated ~2.19 eV. The incorporation of the Fe and Zn metals within the BiOI aided advantages that increased the reactive sites, oxygen defects, photon adsorption, production of hydroxyl radicals, and decrease the recombination rate, thereby high photo-degradation ability. The maximum degradation of ~83% was observed using Fe/Zn-BiOI-1-1 at 10 mg/L of TC antibiotics concentration. Moreover, ~98% of degradation was observed at pH~10 of the TC antibiotics. The photo-activity against bacteria of the Fe/Zn-BiOI was also determined. The data suggested that the synthesized Fe/Zn-BiOI based photocatalyst materials effectively inhibited the bacterial strains. Therefore, Fe/Zn-BiOI based photocatalyst materials might be promising materials that effectively degrade TC antibiotics as well as bacteria.

Synergistic Effects of Carbon Dots and Palladium Nanoparticles Enhance the Sonocatalytic Performance for Rhodamine B Degradation in the Absence of Light

Carbon dot (CD) and palladium nanoparticle (Pd NP) composites are semiconducting materials having tremendous applications in catalysis with suitable band gaps. However, their combination with a suitable polymer matrix in sonophotocatalysis has not been explored. Herein, we have synthesized and characterized a new nanohybrid catalyst from a polyamide cross-linked CD-polymer and subsequent deposition of Pd NPs. A sonocatalytic activity of 99% rhodamine B dye degradation was achieved in mere 5 min in the dark. A model catalyst replacing CDs with benzene and other control studies revealed that the synergistic effects of CDs and Pd NPs enhance the sonocatalytic activity of the nanohybrid catalyst. Interestingly, visible light did not influence the activity significantly. Mechanistic investigations suggest that generation of reactive oxygen species on the surface of the CD-polymer initiated by ultrasound, which is further facilitated by Pd NPs, is the key for remarkable catalytic activity (a rate constant of 0.99 min-1). Recyclable heterogeneous catalysts under ambient conditions are promising for exploring sono-assisted dark catalysis for several avenues.

Fabrication of nanohybrids assisted by protein-based materials for catalytic applications

Protein units and architectures were applied as supports in the synthesis of metal and metal oxide nanoparticles for environmentally benign catalytic applications.

Double charge carrier mechanism through 2D/2D interface-assisted ultrafast water reduction and antibiotic degradation over architectural S,P co-doped g-C3N4/ZnCr LDH photocatalyst

S,P co-doped g-C₃N₄/ZnCr LDH 2D/2D heterostructure for photocatalytic ciprofloxacin degradation and H₂ evolution under the visible light irradiation.