Visible light responsive flower-like ZnO in photocatalytic antibacterial mechanism towards Enterococcus faecalis and Micrococcus luteus

A 2D nanoflower-like ordered mesoporous Bi12ZnO20 catalyst with excellent photocatalytic antibacterial properties

The ordered mesoporous ZnO was successfully synthesized using the template method in this article, and Bi ions were etched into ZnO to form two-dimensional nanoflower structures of Bi12ZnO20 with NA3SSA as a guiding agent. The crystal structure, morphology, and optical properties of the photocatalyst were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer(EDS), and ultraviolet-visible diffuse reflectance spectrum (UV-vis DRS). Under illumination conditions, the obtained materials exhibited excellent bactericidal ability against both gram-positive and gram-negative bacteria, as well as effective inhibition against fungi. Among them, the bactericidal effect of Pseudomonas aeruginosa was found to be the most rapid, achieving a sterilization rate of 100% within 30 min of light irradiation. Even after three cycles of antibacterial activity testing, the Bi12ZnO20 material still demonstrated good photocatalytic performance. The nanoflower-shaped materials provide an enhanced fluid adsorption capacity and more active centers for photocatalytic reactions while also improving light absorption capacity, photogenerated electron-hole separation efficiency, and electron transport efficiency. The cytotoxicity assessment of Bi12ZnO20 revealed no significant toxic effects. Therefore, this study presents a nanoflower-shaped material with highly efficient photocatalytic antibacterial properties for applications in production and daily life; it holds significant importance in eliminating harmful bacteria and plays a crucial role in environmental protection.

IMPORTANCE

The flower-shaped photocatalytic material Bi12ZnO20, consisting of nanoparticles, was successfully synthesized in this study. Rigorous antibacterial experiments were conducted on various fungi using the material, yielding excellent results. Furthermore, the application of this material for antibacterial treatment of livestock and poultry manure sewage in real-life scenarios demonstrated remarkable efficacy.

New Hydrogels Nanocomposites Based on Chitosan, 2-Formylphenylboronic Acid, and ZnO Nanoparticles as Promising Disinfectants for Duodenoscopes Reprocessing

New hydrogels nanocomposites, based on iminoboronate hydrogels and ZnO nanoparticles (ZnO-NPs), were obtained and characterised in order to develop a new class of disinfectants able to fight the nosocomial infections produced by duodenoscopes investigation procedures. The formation of the imine linkages between chitosan and the aldehyde was demonstrated using NMR and FTIR spectroscopy, while the supramolecular architecture of the developed systems was evaluated via wide-angle X-ray diffraction and polarised optical microscopy. The morphological characterisation of the systems via scanning electron microscopy revealed the highly porous structure of the materials, in which no ZnO agglomeration could be observed, indicating the very fine and homogenous encapsulation of the nanoparticles into the hydrogels. The newly synthetised hydrogels nanocomposites was proven to have synergistic antimicrobial properties, being very efficient as disinfectants against reference strains as: Enterococcus faecalis, Klebsiella pneumoniae, and Candida albicans.

Antibacterial Activity of ZnSe, ZnSe-TiO2 and TiO2 Particles Tailored by Lysozyme Loading and Visible Light Irradiation

ZnSe, ZnSe-TiO2 microspheres and nanostructured TiO2 obtained by hydrothermal and sol–gel methods were tested against Staphylococcus aureus ATCC 25923 and Micrococcus lysodeikticus ATCC 4698 before and after lysozyme (Lys) loading. Morphological characterization of inorganic matrices and hybrid organic–inorganic complexes were performed by microscopy techniques (SEM, AFM and Dark Field Hyperspectral Microscopy). Light absorption properties of ZnSe, ZnSe-TiO2 and TiO2 powders were assessed by UV–visible spectroscopy and their ability to generate reactive oxygen species (•OH and O2•−) under visible light irradiation was investigated. Antibacterial activity of ZnSe, ZnSe-TiO2, TiO2, Lys/ZnSe, Lys/ZnSe-TiO2 and Lys/TiO2 samples under exposure to visible light irradiation (λ > 420 nm) was tested against Staphylococcus aureus and Micrococcus lysodeikticus and correlated with ROS photogeneration.

Enhanced synchronous photocatalytic 4-chlorophenol degradation and Cr(VI) reduction by novel magnetic separable visible-light-driven Z-scheme CoFe2O4/P-doped BiOBr heterojunction nanocomposites

The co-existence of organic contaminants and heavy metals including 4-chlorophenol (4-CP) and Cr(VI) in aquatic system have become a challenging task in the wastewater treatment. Herein, the synchronous photocatalytic decomposition of 4-CP and Cr(VI) over new Z-scheme CoFe₂O₄/P-BiOBr heterojunction nanocomposites were revealed. In this work, the nanocomposites were successfully developed via a surfactant-free hydrothermal method. The heterojunction interface was created by decorating magnetic CoFe₂O₄ nanoparticles onto P-BiOBr nanosheets. The as-fabricated CoFe₂O₄/P-BiOBr nanocomposites substantially improved the synchronous decomposition of 4-CP and Cr(VI) compared to the single-phase component samples under visible light irradiation. Particularly, the 30-CoFe₂O₄/P-BiOBr nanocomposite displayed the best photocatalytic performance, which decomposed 95.6% 4-CP and 100% Cr(VI) within 75 min. The photocatalytic improvement was assigned to the Z-scheme heterojunction assisted charge migration between CoFe₂O₄ and P-BiOBr, and the acceleration of charge carrier separation was validated by the findings of charge dynamics measurements. The harmful 4-CP was photodegraded into smaller organics whereas the Cr(VI) was photoreduced into Cr(III) after 30-CoFe₂O₄/P-BiOBr photocatalysis, and the good recyclability of fabricated nanocomposite in photocatalytic reaction also showed promising potential for practical applications in environmental remediation. Finally, the radical quenching tests confirmed that there existed the Z-scheme path of charge migration in CoFe₂O₄/P-BiOBr nanocomposite, which was the mechanism responsible for its high photoactivity.

Mechanistic insight into the photocatalytic degradation of organic pollutants and electrochemical behavior of modified MWCNTs/Cu–Co3O4 nanocomposites

The present work reported the physical, chemical and electrical properties of Cu doped Co3O4.

Ameliorating Cu2+ reduction in microbial fuel cell with Z-scheme BiFeO3 decorated on flower-like ZnO composite photocathode

BiFeO₃ nanoparticle decorated on flower-like ZnO (BiFeO₃/ZnO) was fabricated through a facile hydrothermal-reflux combined method. This material was utilized as a composite photocathode for the first time in microbial fuel cell (MFC) to reduce the copper ion (Cu²⁺) and power generation concomitantly. The resultant BiFeO₃/ZnO-based MFC displayed distinct photoelectrocatalytic activities when different weight percentages (wt%) BiFeO₃ were used. The 3 wt% BiFeO₃/ZnO MFC achieved the maximum power density of 1.301 W m^-2 in the catholyte contained 200 mg L^-1 of Cu²⁺ and the power density was greatly higher than those pure ZnO and pure BiFeO₃ photocathodes. Meanwhile, the MFC exhibited 90.7% removal of Cu²⁺ within 6 h under sunlight exposure at catholyte pH 4. The addition of BiFeO₃ nanoparticles not only manifested outstanding capability in harvesting visible light, but also facilitated the formation of Z-scheme BiFeO₃/ZnO heterojunction structure to induce the charge carrier transfer along with enhanced redox abilities for the cathodic reduction. The pronounced electrical output and Cu²⁺ reduction efficiencies can be realized through the synergistic cooperation between the bioanode and BiFeO₃/ZnO photocathode in the MFC. Furthermore, the developed BiFeO₃/ZnO composite presented a good stability and reusability of photoelectrocatalytic activity up to five cyclic runs.

Super-hydrophobic and photocatalytic antimicrobial activity of iodine-doped ZnO nanoarray films

Iodine(i) doped ZnO nanoarray films (ZnO/I-X) were prepared on a silicon wafer by the in itu growth method.

Fabrication, characterization and high photocatalytic activity of Ag-ZnO heterojunctions under UV-visible light

Pure ZnO and Ag–ZnO nanocomposites were fabricated via a sol–gel route, and the obtained photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL and DRS. The results showed that Ag⁰ nanoparticles deposit on the ZnO surface and Ag modification has negligible impact on the crystal structure, surface hydroxyl group content and surface area of ZnO. However, the recombination of photogenerated electrons and holes was suppressed effectively by Ag loading. The photocatalytic activity was investigated by evaluating the degradation of MB under xenon lamp irradiation as the UV-visible light source, and the results show that the photocatalytic activity of ZnO significantly improved after Ag modification. Ag–ZnO photocatalysts exhibit higher photocatalytic activity than commercial photocatalyst P25. The degradation degree of MB for 1%Ag–ZnO was 97.1% after 15 min. ˙O₂⁻ radicals are the main active species responsible for the photodegradation process, and Ag–ZnO heterojunctions generate more ˙O₂⁻ radicals, which is the primary reason for the improved photocatalytic performance.

Ag–ZnO heterojunction promotes the separation of photogenerated pairs and thus exhibits high catalytic activity under UV-visible light.

Antimicrobial Activity of Zinc Oxide Nano/Microparticles and Their Combinations against Pathogenic Microorganisms for Biomedical Applications: From Physicochemical Characteristics to Pharmacological Aspects

Zinc oxide (ZnO) nano/microparticles (NPs/MPs) have been studied as antibiotics to enhance antimicrobial activity against pathogenic bacteria and viruses with or without antibiotic resistance. They have unique physicochemical characteristics that can affect biological and toxicological responses in microorganisms. Metal ion release, particle adsorption, and reactive oxygen species generation are the main mechanisms underlying their antimicrobial action. In this review, we describe the physicochemical characteristics of ZnO NPs/MPs related to biological and toxicological effects and discuss the recent findings of the antimicrobial activity of ZnO NPs/MPs and their combinations with other materials against pathogenic microorganisms. Current biomedical applications of ZnO NPs/MPs and combinations with other materials are also presented. This review will provide the better understanding of ZnO NPs/MPs as antibiotic alternatives and aid in further development of antibiotic agents for industrial and clinical applications.

A novel application of In2S3 for visible-light-driven photocatalytic inactivation of bacteria: Kinetics, stability, toxicity and mechanism

Photocatalytic bacterial inactivation under visible light emerges as a new alternative to control microbial contamination by utilizing free and renewable sunlight. However, the exploration of highly effective and safe visible-light-driven (VLD) photocatalysts remains an important step toward accessing this new technology. Herein, an eco-friendly photocatalyst, namely Indium Sulfide (In₂S₃), was fabricated through a facile hydrothermal method for VLD photocatalytic inactivation of bacteria. The energy band gap of the as-prepared In₂S₃ was measured as 2.25 eV. As expected, the obtained In₂S₃ photocatalyst showed remarkable inactivation efficiency toward E. coli under fluorescent tubes irradiation. The photocatalytic inactivation kinetic was perfectly fitted by a mathematical model for bacteria inactivation. In addition, In₂S₃ exhibited high stability and could be reused. The leakage of In³⁺ was not significant and showed no toxic effect to the bacteria. Based on the results of scavenger study and ESR technology, the dominant reactive species causing In₂S₃ VLD photocatalytic bacterial inactivation were proposed as O₂^-, h⁺, H₂O₂ and e^-, rather than OH. The SEM study suggested that the damages to the intracellular components occurred prior to the destruction of cell wall. This study provides novel application of In₂S₃ for VLD photocatalytic inactivation of bacteria as well as comprehensive insight into the inactivation mechanism.

Synthesis, Characterization, and Anti-Algal Activity of Molybdenum-Doped Metal Oxides

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl5)2 as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy data confirmed the presence of M-O-Mo linkage (M = Zn, Zr, W, and SrTi) in all the molybdenum-doped metal oxides (MoMOs), but only MoZnO inhibited the growth of the bloom-forming Microcystis aeruginosa under visible light in a concentration-dependent manner up to 10 mg/L. Further, structural characterization of MoZnO using FESEM and XRD exhibited the formation of typical hexagonal wurtzite nanocrystals of approximately 4 nm. Hydroxyl radical (·OH), reactive oxygen species (ROS), and lipid peroxidation assays revealed ·OH generated by MoZnO under the visible light seemed to cause peroxidation of the lipid membrane of M. aeruginosa, which led to an upsurge of intracellular ROS and consequently introduced the agglomeration of cyanobacteria. These results demonstrated that nano-sized MoZnO photocatalyst can be easily synthesized in a cost-effective ball-mill method and utilized for biological applications such as the reduction of harmful algal blooms. Further, our study implies that a simple ball-milling method can provide an easy, green, and scalable route for the synthesis of visible light active doped metal oxides.