Efficient removal of tetracycline hydrochloride through novel Fe/BiOBr/Bi2WO6 photocatalyst prepared by dual-strategy under visible-light irradiation

It is important to investigate whether combining two modification strategies has a synergistic effect on the activity of photocatalysts. In this manuscript, Fe-doped BiOBr/Bi2WO6 heterojunctions were synthesized by a one-pot solvothermal method, and excellent photocatalytic performance was obtained for the degradation of tetracycline hydrochloride (TCH) in water without the addition of surfactant. Combining experiments and characterization, the synergistic effect between Fe ion doping and the BiOBr/Bi2WO6 heterojunction was elucidated. The Fe/BiOBr/Bi2WO6 composite photocatalyst had a beneficial void structure, enhanced visible light response, and could inhibit the recombination of photogenerated support well, which improved the photocatalytic activity. The presented experiments demonstrate that Fe/BiOBr/Bi2WO6 removes 97% of TCH from aqueous solution, while pure BiOBr and Bi2WO6 only remove 56% and 65% of TCH, respectively. Finally, the separation and transfer mechanisms of photoexcited carriers were determined in conjunction with the experimental results. This study provides a new direction for the design of efficient photocatalysts through the use of a dual co-modification strategy.

A facile synthesis of palladium nanoparticles decorated bismuth oxybromide nanostructures with exceptional photo-antimicrobial activities

Assessing the interaction between microbes and nanocatalysts for finding an inclusive, proactive and deep understanding of nanoparticles-based toxicity is vital for discovering their broad range of applications. Palladium based photocatalysts owing to their unique fundamental characteristics and brilliant physicochemical potential have gained immense interest in environment remediation as disinfection system. In the present study, we report synthesis of a novel palladium nanoparticles decorated bismuth oxybromide (Pd/BiOBr) nanostructures using an energy efficient solution-based method, having excellent photocatalytic antibacterial action. The synthesized nanomaterials was thoroughly characterized using various analytical techniques. The photocatalytic antibacterial efficiency of Pd/BiOBr was evaluated against some common pathogenic strains of Gram-positive and Gram-negative bacteria (Pseudomonas fluorescens, Pseudomonas aeruginosa, Escherichia coli, Aeromonas salmonicida, Salmonella typhimurium, Klebsiella pneumoniae, Bacillus subtilis). In our results Pd/BiOBr showed excellent photocatalytic disinfection efficacy with > 99.9% bacterial inactivation. A very low concentration of Pd/BiOBr (0.5 µg/mL) effectively inhibited the bacterial growth in response to just 2 h of visible light irradiation, while 1 µg/mL of Pd/BiOBr completely killed all the tested bacterial strains proving their magnificent bactericidal potential. The developed materials with exceptional antibacterial broad range efficiency can be used in different photocatalytic disinfection systems including water purification systems, biofilm exclusion and combating differential antibiotic resistance.

The room temperature synthesis of a CuO-Bi-BiOBr ternary Z-scheme photocatalyst for enhanced sunlight driven alcohol oxidation

The room temperature synthesis of an all-solid-state Z-scheme CuO-doped BiOBr (CuO-Bi-BiOBr) photocatalyst has been described. These CuO-Bi-BiOBr ternary heterojunctions exhibit efficient photocatalytic activities for selective alcohol oxidation. The structures, morphologies, and compositions of the nanostructures were well characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic absorption spectroscopy (AAS). The X-ray diffraction (XRD) pattern of the as-synthesized nanostructures confirms the formation of phase-segregated CuO and BiOBr nanocrystals, whereas X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) analyses clearly indicate the formation of metallic bismuth nanoparticles (NPs). Next, the developed CuO-Bi-BiOBr ternary heterojunctions were applied as an efficient photocatalyst for the oxidation of alcohols into their corresponding aldehydes/ketones with high selectivity (>99%) and high conversion ratios (>99%). Herein, Bi metal NPs act as an electron mediator and bridge the connectivity between the two semiconductors, BiOBr and CuO, and, thus, a Z-scheme heterojunction is established. As expected, CuO-Bi-BiOBr has shown significantly superior activities compared to those of pure BiOBr. A possible mechanism for the photocatalytic oxidation process has been proposed. Radical scavenging experiments suggest that the active species, h⁺, ˙OH, e^-, and ˙O₂^-, are dominant in the alcohol oxidation process. The as-synthesized CuO-Bi-BiOBr was reused several times without any significant deterioration in the original activities and it thus possesses relatively high stability for practical applications.

Development of novel BiOBr0.75I0.25 nanostructures with remarkably High dark phase bactericidal activities

Semiconductor materials with promising photocatalytic activities are being developed for numerous applications including their use in the development of antibacterial products. However, the light may not be available everywhere, which restrict the use of semiconductor photocatalytic materials in real applications. In this area, we report a novel nanostructure of BiOBr_0.75I_0.25 to show enormously high bactericidal activities even at dark. We used a solution based single step method at room temperature to produce highly porous and crystalline BiOBr_xI_1-x (x = 0-1) nanostructures. Next, the developed materials were thoroughly characterized by different analytical techniques, such as FESEM, XRD, XPS, etc. To evaluate the bactericidal activities Escherichia coli (gram-negative bacteria) and Bacillus subtilis (gram-positive bacteria) were selected. Interestingly we found that the solid solutions exhibited high potential towards both the bacteria and among them, BiOBr_0.75I_0.25 showed extremely high efficiencies even at dark. Due to their semiconductor behavior, the materials have shown higher activities in the presence of any light source. The knowledge about the behavior of these unique materials revels a new area of research and would certainly help to find out the solution for ever-increasing environmental issues.

Selectivity control of organic chemical synthesis over plasmonic metal-based photocatalysts

The factors, issues, and design of plasmonic metal-based photocatalysts for selective photosynthesis of organic chemicals have been discussed.

Room-temperature synthesized In-BiOBr1-xIx nanosheets with visible-light-driven superior photocatalytic activity: Degradation of dye/non-dye organic pollutants for environmental remediation

Photocatalysis is extensively investigated as a green, efficient and promising technique for environmental remediation. In this study, a series of template free In-doped BiOBr_xI_1-x photocatalysts have been successfully prepared at room temperature and characterized by various methods. Complete degradation of negatively charged methyl Orange, positively charged Rhodamine B and Methylene Blue organic dyes, and neutral and colorless non-dye organic compound of furfural was attained. The flat band potential offered the possibility of reduction of dissolved O₂ to O₂^.- in the conduction band while the trapping experiment identified the (O₂^.-)is the main radical species followed by h⁺ for the photodegradation. In-BiOBrI-0.4 had an excellent photocatalytic degradation activity which could be due to the synergetic effect between metal ion doping and solid solution formation. It further promotes visible light-harvesting ability and photoinduced charge carrier separation efficiency. The order of the reaction rate was determined and the mechanism was proposed. This work can lay a base for the design of effective photocatalyst toward environmental remediation.

Water-soluble titanium-polyoxomolybdate with external μ3 bridging oxygen coordination on a lacunary Keggin structure

The first water-soluble titanium-containing polyoxomolybdate was synthesized and structurally characterized, showing photocatalytic activity in benzaldehyde oxidation.