Photocatalytic Bacterial Inactivation Research Articles

Photocatalytic degradation of biological contaminant (E. coli) in drinking water under direct natural sunlight irradiation using incorporation of green synthesized TiO2, Fe2O3 nanoparticles

AbstractGlobally, there is a severe problem of widespread water contamination. Adsorption and photocatalytic degradation are considered the most suitable methods for removing these water pollutants because of their simplicity, environmental friendliness, and capacity to generate high-quality water. By a completely green route, in this recent study, the fungus Aspergillus tubingensis was able to synthesize TiO2 and Fe2O3 NPs with an average diameter of 28.0 and 65 nm, respectively. The smallest NPs diameters were produced when the precursor salt concentrations were 10−3 M and 10−2 M for TiO2 and Fe2O3, respectively, at pH 3 and an incubation time of 72 h. The biosynthesized NPs were characterized using DLS, TEM, EDX, and VSM. They were then applied in the preparation of titanium-iron nanocomposites with different ratios (1:1, 1:2, and 2:1 (w/w)) and characterized by FTIR and XRD. In this study, Escherichia coli (E. coli) was photo-catalytically inactivated using a TiO2–Fe2O3 nanocomposite as a photocatalyst in the presence of direct sunlight. This material’s photocatalytic performance was evaluated in comparison to that of TiO2 and Fe2O3 NPs. After 60 min of exposure to direct sunlight, the cell death was estimated as 97.97%, 99.32%, 89.06%, 30.96%, and 25.14% in the presence of TF-1, TF-2, TF-3, TiO2, and Fe2O3, respectively. Under direct natural sunlight irradiation for 60 min, TiO2 and Fe2O3 nanoparticles alone have the least impact on E. coli, whereas TF-2 nanocomposite has a higher level of photocatalytic bacterial inactivation competency than TF-1 and TF-3 nanocomposites. No significant toxicity has been observed for TF-2-treated water samples in the toxicity assessment.

Highly dispersed Pd icosahedra and Ag nanocubes on ultrathin g-C3N4 nanosheet for boosting photocatalytic bacterial inactivation and organic pollutants degradation

Engineering surface facet of metallic nanoparticles that decorated on certain substants is an intriguing strategy to modulate photocatalytic capacity. Herein, a novel photocatalyst by doping g-C3N4 nanosheet with Pd icosahedra with {111} facets and Ag nanocubes with {100} facets were firstly synthesized through facile wet-chemical route. The successfully constructed g-C3N4/Pd/Ag composites were employed as a visible-light-driven dual-functional photocatalyst for bacterial inactivation and organic contaminant degradation. Result suggested that 1 × 108 CFU/mL E. coli strains can be totally inactivated by g-C3N4/Pd/Ag within 60 min, outperformed that of {100} faceted enclosed Pd nanocubes functioned g-C3N4/Ag. Also, the optimized g-C3N4/Pd/Ag exhibited ideal photocatalytic performance toward tetracycline and methylene blue degradation. The rate constant was found to be 8.74 × 10−3 and 7.08 × 10−3 min−1, respectively, which was higher than those of bare g-C3N4 and g-C3N4/Pd. Quenching experiment and electron paramagnetic resonance analysis suggested that hole (h+), electron (e−), and superoxide radical (O2−) exerted a key role in the improved capacity. Furthermore, the more positive Fermi level of Pd icosahedra and Ag nanocubes relative to that of g-C3N4 also contributed to the enhanced photocatalytic performance. Collectively, our work can provide in-depth insight into fabricate novel facet-engineering photocatalyst for environmental applications.

Rose petal patterns with “Lotus Effect”, corrosion resistance and photocatalytic bacterial inactivation

The study proposes a simple method that can easily transform the surface from the “rose petal effect” to the “lotus effect” and impart superhydrophobic and photocatalytic properties. The approach involves integrating hydrophobic TiO2 nanoparticles into a polystyrene (PS) matrix, employing a soft imprinting process to create intricate rose petal patterns. SEM and TEM images demonstrate the uniform distribution of TiO2 nanoparticles across the coated surface, providing roughness and elevating the static water contact angle to 163°, while reducing the hysteresis angle to below 5°. This approach effortlessly transitions the surface from the rose petal effect to the lotus effect. Furthermore, the highly superhydrophobic PS/TiO2 pattern coating demonstrates excellent corrosion resistance, with up to 99.98 % efficiency in Tafel experiments. Additionally, the PS/TiO2 pattern coating exhibits photocatalytic properties, effectively decomposing methylene blue and bacteria (S. aureus and E. coli). Through the integration of nanoparticles, this method not only enables precise control of surface properties, but also brings new applications to coatings.

Sulphated TiO2 Reduced by Ammonia and Hydrogen as an Excellent Photocatalyst for Bacteria Inactivation.

This study presents a relatively low-cost method for modifying TiO2-based materials for photocatalytic bacterial inactivation. The photocatalytic inactivation of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria using modified sulphated TiO2 was studied. The modification focused on the reduction of TiO2 by ammonia agents and hydrogen at 400-450 °C. The results showed a high impact of sulphate species on the inactivation of E. coli. The presence of these species generated acid sites on TiO2, which shifted the pH of the reacted titania slurry solution to lower values, around 4.6. At such a low pH, TiO2 was positively charged. The ammonia solution caused the removal of sulphate species from TiO2. On the other hand, hydrogen and ammonia molecules accelerated the removal of sulphur species from TiO2, as did heating it to 450 °C. Total inactivation of E. coli was obtained within 30 min of simulated solar light irradiation on TiO2 heat-treated at 400 °C in an atmosphere of Ar or NH3. The S. epidermidis strain was more resistant to photocatalytic oxidation. The contact of these bacteria with the active titania surface is important, but a higher oxidation force is necessary to destroy their cell membrane walls because of their thicker cell wall than E. coli. Therefore, the ability of a photocatalyst to produce ROS (reactive oxidative species) will determine its ability to inactivate S. epidermidis. An additional advantage of the studies presented is the inactivation of bacteria after a relatively short irradiation time (30 min), which does not often happen with photocatalysts not modified with noble metals. The modification methods presented represent a robust and inexpensive alternative to photocatalytic inactivation of bacteria.

Photocatalytic inactivation mechanism of nano-BiPO4 against Vibrio parahaemolyticus and its application in abalone

Vibrio parahaemolyticus (V. parahaemolyticus) is the main pathogenic bacteria in seafood that can cause serious food-borne illness. The annual incidence of V. parahaemolyticus infection in the United States exceeds 45,000 cases, indicating there are potential shortcomings in seafood sterilization techniques. Meanwhile, the ongoing emergence of antibiotic-resistant strains highlights the urgent need for novel bacteriostatic strategies to eliminate V. parahaemolyticus. Nano-BiPO4 is a semiconductor with high H2O2 production efficiency and has potential for photocatalytic bacterial inactivation. But the effectiveness and mechanism of BiPO4 photocatalytic inactivation of V. parahaemolyticus has not been reported. In this study, nano-BiPO4 synthesized in pure water (P1) was found to exhibit optimal H2O2 production efficiency (1203 μmol h-1g−1) and antibacterial activity (in 0.8 g/L). Under UV light irradiation, P1 induced alterations in bacterial cell morphology, elevation in intracellular levels of ROS, H2O2, O2–, GSSG and MDA, and reduction in GSH level. Meanwhile, metabolomic analysis revealed that P1 stimulates the arginine biosynthesis, TCA cycle and alanine, aspartate and glutamate metabolism. These abnormal changes in the oxidative stress indicators and metabolic pathways proved that the bacterial damage was related to the H2O2 produced by nano-BiPO4 photocatalysis. Moreover, sliced abalone and hemolysis assay were used to demonstrate the applicability and biosafety of P1. This study provides theoretical support for exploring nano-BiPO4 as a bacterial inhibitor against V. parahaemolyticus.

Copper-doped bismuth oxychloride nanosheets assembled into sphere-like morphology for improved photocatalytic inactivation of drug-resistant bacteria

The devastating microbiological contamination as well as emerging drug-resistant bacteria has posed severe threats to the ecosystem and public health, which propels the continuous exploitation of safe yet efficient disinfection products and technology. Here, copper doping engineered bismuth oxychloride (Cu-BiOCl) nanocomposite with a hierarchical spherical structure was successfully prepared. It was found that due to the exposure of abundant active sites for the adsorption of both bacteria cells and molecular oxygen in the structure, the obtained Cu-BiOCl with nanosheets assembled into sphere-like morphology exhibited remarkable photocatalytic antibacterial effects. In particular, compared to the pure BiOCl, composite Cu-BiOCl possessed improved antibacterial effects against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Methicillin-resistant Staphylococcus aureus (MRSA). The combination of physicochemical characterizations and theoretical calculations has revealed that copper doping significantly promoted the light absorbance, inhibited the recombination of electron-hole pairs, and enhanced molecular oxygen adsorption, which resulted in more generation of active species including reactive oxygen species (ROS) and h+ to achieve superior photocatalytic bacterial inactivation. Finally, transcriptome analysis on MRSA pinpointed photocatalytic inactivation induced by Cu-BiOCl may retard largely the development of drug-resistance. Therefore, the built spherical Cu-BiOCl nanocomposite has provided an ecofriendly, economical and robust strategy for the efficient removal of drug-resistant bacteria with promising potentials for environmental and healthcare utilizations.

Modulation of ultrathin nanosheet structure and nitrogen defects in graphitic carbon nitride for efficient photocatalytic bacterial inactivation

The efficient generation and utilization of ROSs is a key step in determining the achievement of safe drinking water by photocatalytic bacterial inactivation technology. Although graphitic carbon nitride (g-C3N4) serves as a green and promising photocatalyst for water disinfection, insufficient bacterial capturing capacity and serious charge recombination of pristine g-C3N4 extremely restrict its bactericidal activity. Herein, we develop a facile thermal exfoliation and thermal polymerization method to prepare the nitrogen-defective ultrathin g-C3N4 nanosheets (DUCN-500). Our results showed that ultrathin nanosheet structure greatly enhanced bacterial capturing capacity of g-C3N4 to increase the utilization efficiency of ROS, which contributed to the performance of DUCN-500 greatly outperforming bulk g-C3N4. The nitrogen defects increased ROS generation (·O2− and H2O2) by approximately 4.6 times, which was attributed to negative shift of the conduction band potential and rapid separation of charge carriers. The DUCN-500 could rapidly and completely inactivate Escherichia coli and Bacillus subtilis in real sewage under simulated solar irradiation, accompanied by good anti-interference capability and stability. Additionally, bacterial morphology destruction, the loss of antioxidant enzyme activity and the leakage of protein were proven to be the main mechanisms of photocatalytic sterilization. This study offers new insight into the rational design of efficient g-C3N4-based photocatalysts for water disinfection.

Visible light-driven photocatalytic bacterial inactivation on PPE, supported by the DFT and bactericidal study.

A novel ZnO-MoO3-ZnMoO3@graphene GZM composite catalyst prepared by microwave hydrothermal process for personal protective equipment textiles (PPE) is presented in this study. The results indicated that the GZM with defect vacancy sites of two types as observed by EPR showed significantly superior inactivation of the E. coli bacteria compared to GZM without the lower defect vacancy sites and concomitant lower electron densities. Photocatalytic activated oxidation by the GZM composites coatings was observed to proceed in acceptable times as well as the bacterial inactivation (log bact. C/Co > 107 within 3h). Defect sites in the GZM seem to be important leading to the bacterial inactivation process. DFT calculations on the GZM with and without catalyst defect sites were carried out. The electron densities were estimated by the Fourier mapping. The results found in this study showed the potential of GZM-PPE for practical applications.

In situ confined growth of g-C3N4/pigment compound catalyst in porous diatomite for enhancing photocatalytic nicotine elimination and bacterial inactivation

Humans spend at least 70% of their time indoors, but indoor air pollution has received very little attention compared to outdoor pollution. Indoor air pollutants include inhalable particulate matter, volatile organic pollutants, and biological pollutants. In particular, nicotine in second-hand smoke and pathogenic microorganisms in the air are the most overlooked pollutants, which pose serious threats to human health. Here, low-cost inorganic pigments and diatomite have been selected to modify g-C3N4 to obtain five novel g-C3N4-based photocatalysts, which are intensely colored and show excellent nicotine degradation performance under both simulated sunlight and white LED illumination. Five g-C3N4-based photocatalytic textiles obtained by supporting the colored photocatalysts on low-melting-point skin–core composite polyester (LMPET) still exhibited outstanding photocatalytic degradation performance and cyclability in removing nicotine. Some of the photocatalytic textiles also displayed highly efficient bacterial inactivation towards E. coli and S. aureus under white LED illumination. Mechanistic research has revealed that the combination of inorganic pigments and diatomite effectively promotes the separation of photogenerated electrons and holes. Moreover, •O2-, 1O2, and •OH have been identified as the main active species in the colored photocatalyst systems. Notably, the colored photocatalysts may be used as dyes to make wall coverings, sofa covers, and so on, which could conceivably purify indoor air while playing a decorative role.

Visible-light-responsive hydrogen-reduced CoOx loaded Rh/Sb:SrTiO3 nanocubic photocatalyst for degradation of organic pollutants and inactivation of bacteria

In this work, we synthesized cobalt oxide loaded Rh/Sb:SrTiO3-nanocube (NC) photocatalysts for organic dye degradation and bacterial inactivation. Firstly, we synthesized Rh/Sb-doped SrTiO3 NC nanocomposite and further loaded cobalt oxide (2 wt%) via wet impregnation and followed by hydrogen-reduction treatments. Interestingly, after hydrogen heat treatment cobalt oxide-loaded photocatalysts convert into metallic Co/CoOx-Rh/Sb:SrTiO3 NCs. The hydrogen-treated Co/CoOx-Rh/Sb:SrTiO3 NCs (red) photocatalyst shows significantly high degradation efficiencies and good recyclability for Orange II dye (90.1%) and bisphenol A (99.1%) under visible-light irradiation (λ ≥ 420 nm) within 30 min. Additionally, the bacterial inactivation efficiency of Co/CoOx-Rh/Sb:SrTiO3 NCs (red) photocatalyst reaches about ∼97% for both Staphylococcus aureus and Escherichia coli under visible light. The enhanced photocatalytic dye degradation and bacterial inactivation activity of Co/CoOx-Rh/Sb:SrTiO3 NCs (red) photocatalyst was due to the delayed photogenerated charge-recombination process, generation of oxygen vacancies, and the synergistic effect of a metallic Co/CoOx phase. Further, radical trapping experiments confirmed that the degradation of Orange II was governed by the major species, •O−2 and h+. In last, the possible charge-transfer mechanisms of the photocatalytic degradation of organic pollutants, as well as the inactivation of bacteria over the Co-Rh/Sb: SrTiO3 (red) NC photocatalyst, are presented in detail.

Unraveling the role of defect types in Fe3O4 for efficient NIR-driven photocatalytic inactivation

Defect engineering is of great importance to tailor photocatalytic activity, which is uncertain in determining the antibacterial performance relationship with defect types. In this study, Fe3O4 nanoparticles with different vacancies were successfully prepared to investigate their distinct effects on the near-infrared (NIR) driven photocatalytic bacterial inactivation activity. Compared to the Fe3O4-1 with Fe-O vacancies, Fe3O4-2 with Fe-O–Fe vacancies contained improved photogenerated electron-hole separation efficiency and stronger adsorption ability to O2, and thus greatly facilitated the generation of reactive oxygen species (O2− and OH). Meanwhile, Fe3O4-2 with a narrow band gap can enhance NIR light absorption and the generation of heat. Moreover, Fe3O4-2 with Fe-O–Fe vacancies possessed enhanced bacteria-binding ability, thereby decreasing the diffusion distance of the released reactive oxygen species and heat, which could significantly accelerate bacterial killing. Owing to these tendencies, Fe3O4-2 fully inactivated 99% Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) within 10 min NIR irradiation, displaying better inactivation efficiency than Fe3O4-1. This study reveals the defect type-dependent photocatalytic behaviors, providing new insights into the antibacterial mechanisms of Fe3O4.

Deciphering the photoactive species-directed antibacterial mechanism of bismuth oxychloride with modulated nanoscale thickness

As an environmentally benign disinfection strategy, photocatalytic bacterial inactivation using nanoparticles involves photogenerated reactive species that cause cellular oxidative stress. Rationalising the structural performance of photocatalysts for the practical uses such as wastewater treatment has attracted significant attention; however, the contribution of reactive species to their photocatalytic antibacterial activities at the molecular and transcriptomic levels remains unclear. In this study, nontoxic bismuth oxychloride (BiOCl) photocatalysts with different nanoscale thicknesses, including nanosheets (Ns, ∼5.4 nm), nanoplates (Np, ∼1.8 nm), and ultra-nanosheets (Uns, ∼1.1 nm), were synthesised under hydrothermal conditions. Among the three samples, BiOCl Uns exhibited the most effective photocatalytic degradation efficiency with the calculated apparent rate constant of 0.0294 min−1, ∼4 times faster than that of Ns, whereas BiOCl Ns possessed the most pronounced bactericidal effect (5.4 log inactivation). Such findings indicate the distinct role of the photoactive species responsible for photocatalytic bacterial inactivation. Moreover, transcriptome analysis of Escherichia coli after photocatalytic treatment revealed that the underlying photocatalytic antibacterial mechanism at the genetic expression level involves cellular component biosynthesis, energy metabolism, and material transportation. Notably, the differences between BiOCl Ns and BiOCl Uns were significantly enriched in purine metabolism. Therefore, the cost-effective preparation of BiOCl nanosheets with nanoscale thickness-modulated photocatalytic antibacterial activity has remarkable potential for sustainable environmental and biomedical applications.

Dynamics of VOCs degradation and bacterial inactivation at the interface of AgxO/Ag/TiO2 prepared by HiPIMS under indoor light

• Indoor/outdoor air pollution and bacteria were degraded on sputtered Ag x O/Ag/TiO 2 on textile. • Photocatalytic kinetics are carried out in the dark and under visible light. • Ag/AgxO nanoparticles show a significant effect on the activity of TiO 2 . • A possible mechanism of photocatalytic processes is suggested. Ag x O/Ag/TiO 2 photoactive thin films were produced by different modes of magnetron sputtering (namely, DCMS and HiPIMS). The spectral and microstructural properties of the Ag-Ag x O/TiO 2 thin films were studied by Diffuse Reflection Spectroscopy (DRS) and X-Ray Photoemission Spectroscopy (XPS). The atomic deposition of TiO2 and Ag in the thin sputtered film were studied by TEM. Ag x O/Ag/TiO 2 exhibited fast photocatalytic volatile organic compounds (VOCs) degradation and bacterial inactivation under low visible light intensity. The Langmuir Hinshelwood model was applied to highlight the photocatalytic performance of the Ag x O/Ag/TiO 2 catalyst. The oxidative states of Ag-Ag x O/TiO 2 were studied by XPS. Deconvolution of the Ag3d peak of the Ag x O/Ag/TiO 2 thin films showed the presence of AgO and metallic Ag. It is suggested that the mechanism involving the degradation of VOCs on AgO/Ag/TiO 2 catalysts is due to the transfer of holes from AgO to TiO 2 via the AgO/Ag/TiO 2 heterojunction. The electrostatic interaction between both semiconductors allows this charge transfer. In addition, the contribution of reactive oxygen species (ROS) in bacterial inactivation at the interface of AgO/Ag/TiO 2 thin film was also examined. Light-induced interfacial charge transfer (IFCT) between AgO and TiO 2 leading to pollutants oxidation appears to require low photons’ energy and can oxidize pollutants even at high concentrations. The sputtered coatings have also been studied for repetitive reuse, showing the sustainable activity of the prepared materials.

Surface anchoring of nickel sulfide clusters as active sites and cocatalysts for photocatalytic antibiotic degradation and bacterial inactivation

Achieving photocatalytic antibiotic degradation and bacterial inactivation with high efficiency remains a challenging mission to originate a clean environment. In this work, ultra-small NiS clusters were in-situ grew on photoactive ZnIn2S4 nanoflower supports to form a NiS/ZnIn2S4 heterojunction, in which a strong and surface-limited binding was formed between the NiS clusters and ZnIn2S4 supports. The in-situ formed NiS clusters not only appeased interfacial charge transfer resistance of the heterojunction but also eventuated a strong built-in electric field, resulting a fast electron migration from ZnIn2S4 to NiS clusters functioned as cocatalyst and active sites to boost the separation efficiency of photogenerated carriers. As a result, the optimal 2NiS/ZnIn2S4 heterojunction expressed a higher photocatalytic Escherichia inactivation activity (99.23 % for 3 h) and a raised antibiotic degradation performance, including tetracycline (60 % for 20 min), ofloxacin (62 % for 20 min), oxytetracycline (63 % for 20 min) compared to that of pure ZnIn2S4 (39.14 % for Escherichia inactivation and 44 % for tetracycline degradation). This work furnishes a great promise to develop inorganic clusters coupled photocatalysts for light-driven environmental application.

CaIn2S4–In2O3 hybrid nanofibers with expedited photocarrier separation for fast photocatalytic bacterial inactivation under visible light

CaIn2S4–In2O3 hybrid fibers deliver exceptionally high photocatalytic activity for bacterial inactivation due to a strong interplay between CaIn2S4 and In2O3.

Tocopherol-assisted magnetic Ag-Fe3O4-TiO2 nanocomposite for photocatalytic bacterial-inactivation with elucidation of mechanism and its hazardous level assessment with zebrafish model.

In recent years, many endeavours have been prompted with photocatalytic nanomaterials by the need to eradicate pathogenic microorganisms from water bodies. Herein, a tocopherol-assisted Ag-Fe3O4-TiO2 nanocomposite (TAFTN) was synthesized for photocatalytic bacterial inactivation. The prepared TAFTN became active under sunlight due to its narrowed bandgap, inactivating the bacterial contaminants via photo-induced ROS stress. The ROS radicals destroy bacteria by creating oxidative stress, which damages the cell membrane and cellular components such as nucleic acids and proteins. For the first time, the nano-LC-MS/MS-based quantitative proteomics reveals that the disrupted proteins are involved in a variety of cellular functions; the most of these are involved in the metabolic pathway, eventually leading to bacterial death during TAFTN-photocatalysis under sunlight. Furthermore, the toxicity analysis confirmed that the inactivated bacteria seemed to have no detrimental impact on zebrafish model, showing that the disinfected water via TAFTN-photocatalysis is enormously safe. Furthermore, the TAFTN-photocatalysis successfully killed the bacterial cells in natural seawater, indicating the consistent photocatalytic efficacy when recycled repeatedly. The results of this work demonstrate that the produced nanocomposite might be a powerful recyclable and sunlight-active photocatalyst for environmental water treatment.

The construction of high efficient visible-light-driven 3D porous g-C3N4/Fe3O4 photocatalyst: A new photo-induced bacterial inactivation material enhanced by cascade photo-Fenton reaction

Photocatalytic disinfection is considered a promising method for eliminating the hazards of pathogenic bacteria. Graphitic carbon nitride (g-C3N4) is an ideal photocatalytic bacterial inactivation material for its advantage of tunable band structure, good stability and easy preparation. This work has constructed a novel defective 3D porous g-C3N4 by cyanamide carbonation using dendritic mesoporous silica template. The direct loading of Fe3O4 nanoparticles provided an excellent pg–C3N4–Fe3O4 photocatalyst suitable for water disinfection. Compared to pristine g-C3N4, the prepared 3D porous defective g–C3N4–Fe3O4 exhibited the enhanced visible light absorbance as indicated by the band gap decreasing of 0.66 eV, and about 3 and 10 fold increase of photo-induced current response and O2 adsorption respectively. The pg–C3N4–Fe3O4 showed excellent visible-light-driven photocatalytic bactericidal activity. It could kill 1 × 107 cfu mL−1Escherichia coli completely within 1 h under visible-light illumination (100 mW cm−2) with good reusability, its logarithmic bacterial inactivation efficiency was about 2.5 fold higher than pg-C3N4. The enhanced bactericidal performance is mainly ascribed to the Fe3O4 involved cascade photo-Fenton reaction.

Efficient Photocatalytic Dye Degradation and Bacterial Inactivation by Graphitic Carbon Nitride and Starch-Doped Magnesium Hydroxide Nanostructures.

The removal of hazardous pollutants from water is becoming an increasingly interesting topic of research considering their impact on the environment and the ecosystem. This work was carried out to synthesize graphitic carbon nitride (g-C3N4) and starch-doped magnesium hydroxide (g-C3N4/St-Mg(OH)2) nanostructures via a facile co-precipitation process. The focus of this study is to treat polluted water and bactericidal behavior with a ternary system (doping-dependent Mg(OH)2). Different concentrations (2 and 4 wt %) of g-C3N4 were doped in a fixed amount of starch and Mg(OH)2 to degrade methylene blue dye from an aqueous solution with bactericidal potential against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) pathogens. The textural structures, morphological evolutions, and optical characteristics of the as-prepared samples were analyzed using advanced characterization techniques. X-ray diffraction confirmed the hexagonal phase of Mg(OH)2 with improved crystallinity upon doping. Fourier transform infrared spectroscopy revealed Mg(OH)2 stretching vibrations and other functional groups. UV-visible spectroscopy exhibited a red shift (bathochromic effect) in absorption spectra representing the decrease in energy band gap (E g). Photoluminescence patterns were recorded to study recombination of charge carriers (e- and h+). A significant enhancement in photodegradation efficiency (97.62%) and efficient bactericidal actions against E. coli (14.10 mm inhibition zone) and S. aureus (7.45 mm inhibition zone) were observed for higher doped specimen 4% g-C3N4/St-Mg(OH)2.

Photocatalytic Bacterial Inactivation of Acinetobacter baumannli on Cu/TiO2/Diatomite

Cu4Ti2O/TiO2/diatomite with double interface Cu4Ti2O/TiO2 and rutile/anatase heterojunction were fabricated, which demonstrated good antibacterial activity (100%) against Acinetobacter baumannii. Cu/TiO2/diatomite prepared under optimum preparation conditions (added diatomite, 0.005 g; Cu, 0.005 g; reaction temperature, 180 °C; reaction time, 8 h) exhibited high antibacterial activity (100%) against A. baumannii. For the Cu/TiO2/diatomite powders, their structural, compositional, optical and morphological traits were characterized by XRD, SEM, TEM, XPS, BET, FTIR, Mapping, and DRS. It was shown that Cu/TiO2/diatomite under optimum conditions consisted of the double interface Cu4Ti2O/TiO2 and rutile/anatase heterojunction with the narrowest band gap and largest BET surface area, pore size, and pore volume. Then, it could exhibit the best photocatalytic activity.

Synergistic role of in-situ Zr-doping and cobalt oxide cocatalysts on photocatalytic bacterial inactivation and organic pollutants removal over template-free Fe2O3 nanorods

Herein, we synthesized in-situ Zr-doped Fe2O3 NRs photocatalyst by successive simple hydrothermal and air quenching methods. The synergistic roles of CoOx (1 wt%) and Zr-doping on bacteria inactivation and model organic pollutants over Fe2O3 NRs photocatalyst were studied in detail. Initially, rod-like Zr ((0–8) %)-doped Fe2O3 NRs were produced via a hydrothermal method. CoOx was loaded onto the Zr ((0–8) %)-doped Fe2O3 NRs) surface by a wet impregnation approach. The Zr-doping conditions and CoOx loadings were judiciously optimized, and a highly photoactive CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst was developed. The CoOx(1 wt%) loaded Zr(6%)-doped Fe2O3 NRs photocatalyst revealed 99.4% inactivation efficiency compared with (0, 4 and 8)% Zr-doped Fe2O3 NRs, respectively. After CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst treatment, Bio-TEM images of bacterial cells showed extensive morphological deviations in cell membranes, compared with the non-treated ones. Additionally, the optimum CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst exhibited 99.2% BPA and 98.3% orange II dye degradation after light radiation for 3 h. This work will provide a rapid method for the development of photostable catalyst materials for bacterial disinfection and organic degradation.