Visible light photo catalytic inactivation of bacteria and photo degradation of methylene blue with Ag/TiO2 nanocomposite prepared by a novel method

Analysis of Ag-DP25/PET plasmonic nano-composites as a visible-light photocatalyst for wastewater treatment: Experimental/theoretical studies, and the DFT-MB degradation mechanism

The development of polymeric-composites Agx%DP25-PET (x = 0,1,2,3) may significantly boost the potential application of Agx%DP25 (x = 0,1,2,3) photocatalytic powders. Producing large-scale nano-composites with hybrid-surfaces, that are also flexible materials and easy to employ in a variety of environments. A set of photocatalytic nan-composites embedded with the polymeric binder poly (acrylonitrile-co-butadiene)-dicarboxy terminated (C7H9N) were performed and evaluated for wastewater treatment applications. The results reveal that the flexible polymeric composites (Agx%DP25-PET, x = 0,1,2,3) have photocatalytic activity in aqua media to degrade methylene blue (MB) under visible-light. The addition of C7H9N to immobilize photocatalytic powders on the PET surface reduces photo-generated electron-hole recombination. The materials were characterized by HR-TEM, SEM/EDX, XRD, FT-IR, UV-Vis DRS and PL. The Agx%DP25-PET (x = 0,1,2,3) photocatalytic reactions exhibited productive discoloration/degradation rates, in both aerobic (AE) and anaerobic (AN) environments. The superior photodegradation of Ag2%DP25-PET was attributed to a combination of two effects: LSPR (localized surface plasmon resonance) and Ag-TiO2/environment affinities. The findings of molecular dynamics (MD) simulation and Fukui Function (FF) based on density functional theory (DFT) provide significant insight into the photocatalytic requirements for MB discoloration/degradation. The experimental/theoretical analysis aimed to offer an in-depth understanding of medium/surface interactions on decorated TiO2 materials, as well as how these interactions affect overall degradation behavior.

Phyco-synthesis of silver nanoparticles by environmentally safe approach and their applications

In recent years, there has been an increasing interest in the green synthesis of metallic nanoparticles, mostly because of the evident limitations associated with chemical and physical methods. Green synthesis, commonly referred to as "biogenic synthesis," is seen as an alternative approach to produce AgNPs (silver nanoparticles). The current work focuses on the use of Asterarcys sp. (microalga) for biological reduction of AgNO3 to produce AgNPs. The optimal parameters for the reduction of AgNPs were determined as molarity of 3 mM for AgNO3 and an incubation duration of 24 h at pH 9, using a 20:80 ratio of algal extract to AgNO3. The biosynthesized Ast-AgNPs were characterised using ultraviolet-visible spectroscopy (UV-Vis), zeta potential, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) patterns. The nanoparticles exhibited their highest absorption in the UV-visible spectra at 425 nm. The X-ray diffraction (XRD) investigation indicated the presence of characteristic peaks at certain angles: 38.30° (1 1 1), 44.40° (2 0 0), 64.64° (2 2 0), and 77.59° (3 1 1) according to the JCPDS file No. 04-0783. Based on SEM and TEM, the Ast-AgNPs had an average size of 35 nm and 52 nm, respectively. The zeta potential was determined to be - 20.8 mV, indicating their stability. The highest antibacterial effectiveness is shown against Staphylococcus aureus, with a zone of inhibition of 25.66 ± 1.52 mm at 250 μL/mL conc. of Ast-AgNPs. Likewise, Ast-AgNPs significantly suppressed the growth of Fusarium sp. and Curvularia sp. by 78.22% and 85.05%, respectively, at 150 μL/mL conc. of Ast-AgNPs. In addition, the Ast-AgNPs exhibited significant photocatalytic activity in degrading methylene blue (MB), achieving an 88.59% degradation in 120 min, revealing multiple downstream applications of Ast-AgNPs.

Advanced photocatalytic materials based degradation of micropollutants and their use in hydrogen production - a review

The use of pharmaceuticals, dyes, and pesticides in modern healthcare and agriculture, along with expanding industrialization, heavily contaminates aquatic environments. This leads to severe carcinogenic implications and critical health issues in living organisms. The photocatalytic methods provide an eco-friendly solution to mitigate the energy crisis and environmental pollution. Sunlight-driven photocatalytic wastewater treatment contributes to hydrogen production and valuable product generation. The removal of contaminants from wastewater through photocatalysis is a highly efficient method for enhancing the ecosystem and plays a crucial role in the dual-functional photocatalysis process. In this review, a wide range of catalysts are discussed, including heterojunction photocatalysts and various hybrid semiconductor photocatalysts like metal oxides, semiconductor adsorbents, and dual semiconductor photocatalysts, which are crucial in this dual function of degradation and green fuel production. The effects of micropollutants in the ecosystem, degradation efficacy of multi-component photocatalysts such as single-component, two-component, three-component, and four-component photocatalysts were discussed. Dual-functional photocatalysis stands out as an energy-efficient and cost-effective method. We have explored the challenges and difficulties associated with dual-functional photocatalysts. Multicomponent photocatalysts demonstrate superior efficiency in degrading pollutants and producing hydrogen compared to their single-component counterparts. Dual-functional photocatalysts, incorporating TiO2, g-C3N4, CeO2, metal organic frameworks (MOFs), layered double hydroxides (LDHs), and carbon quantum dots (CQDs)-based composites, exhibit remarkable performance. The future of synergistic photocatalysis envisions large-scale production facilitate integrating advanced 2D and 3D semiconductor photocatalysts, presenting a promising avenue for sustainable and efficient pollutant degradation and hydrogen production from environmental remediation technologies.

TiO2 Nanocomposite Coatings and Inactivation of Carbapenemase-Producing Klebsiella Pneumoniae Biofilm-Opportunities and Challenges

The worldwide increase of multidrug-resistant Gram-negative bacteria is a global threat. The emergence and global spread of Klebsiella pneumoniae carbapenemase- (KPC-) producing Klebsiella pneumoniae represent a particular concern. This pathogen has increased resistance and abilities to persist in human reservoirs, in hospital environments, on medical devices, and to generate biofilms. Mortality related to this microorganism is high among immunosuppressed oncological patients and those with multiple hospitalizations and an extended stay in intensive care. There is a severe threat posed by the ability of biofilms to grow and resist antibiotics. Various nanotechnology-based strategies have been studied and developed to prevent and combat serious health problems caused by biofilm infections. The aim of this review was to evaluate the implications of nanotechnology in eradicating biofilms with KPC-producing Klebsiella pneumoniae, one of the bacteria most frequently associated with nosocomial infections in intensive care units, including in our department, and to highlight studies presenting the potential applicability of TiO2 nanocomposite materials in hospital practice. We also described the frequency of the presence of bacterial biofilms on medical surfaces, devices, and equipment. TiO2 nanocomposite coatings are one of the best long-term options for antimicrobial efficacy due to their biocompatibility, stability, corrosion resistance, and low cost; they find their applicability in hospital practice due to their critical antimicrobial role for surfaces and orthopedic and dental implants. The International Agency for Research on Cancer has recently classified titanium dioxide nanoparticles (TiO2 NPs) as possibly carcinogenic. Currently, there is an interest in the ecological, non-toxic synthesis of TiO2 nanoparticles via biological methods. Biogenic, non-toxic nanoparticles have remarkable properties due to their biocompatibility, stability, and size. Few studies have mentioned the use of nanoparticle-coated surfaces as antibiofilm agents. A literature review was performed to identify publications related to KPC-producing Klebsiella pneumoniae biofilms and antimicrobial TiO2 photocatalytic nanocomposite coatings. There are few reviews on the antibacterial and antibiofilm applications of TiO2 photocatalytic nanocomposite coatings. TiO2 nanoparticles demonstrated marked antibiofilm activity, but being nano in size, these nanoparticles can penetrate cell membranes and may initiate cellular toxicity and genotoxicity. Biogenic TiO2 nanoparticles obtained via green, ecological technology have less applicability but are actively investigated.

The effect of TiO2 nanoparticles on bacterial growth: the effect of particle size and their structure - a systematic review

One of the widely used microbiological methods to determine the toxicity of chemicals, catalysts, and other types of materials is the minimum inhibitory concentration (MIC) test. The present study aims to investigate the influence of composition of composite materials based on TiO2 and their particle size as well as bacterial type and shape based on the MIC values reported in the literature. The results show that among the 36 articles selected, most of the studies used Escherichia coli (E. coli) (26) and Staphylococcus aureus (S. aureus) (19) bacteria to determine MIC values. This study revealed that the MIC in values below 70 µg ml-1 for S. aureus was lower than that for E. coli bacteria (below 200 µg ml-1). Importantly, MIC value decreased from 60.6 to 7.66 µg ml-1 with decrease in the size of nanoparticles. It follows from the increased surface area for smaller-sized particles, thus increased interaction with bacteria during MIC test.

Research status and prospect of nano silver (Ag)-modified photocatalytic materials for degradation of organic pollutants

Nano silver (Ag) was metallic Ag monomers with particle size to the nanoscale. Photocatalyst was a kind of semiconductor material with photocatalytic function. Loading precious metal Ag onto semiconductor surfaces by microwave, laser-induced, solvent-thermal and hydrothermal methods could capture photogenerated electrons, reduced the compounding rate of holes and photogenerated electrons during the photocatalytic process, thereby improving the electron transfer efficiency of photocatalysis and enhancing the absorption of visible light by silver nanoparticles through the plasma resonance effect. The highly reactive free radicals produced by photocatalysts were used in the organic degradation process to degrade organic matter into inorganic matter and was a faster, more efficient and less polluting method of pollutant degradation, which has attracted a lot of attention from researchers. This review discussed the modification of various types of photocatalysts by nano Ag through different methods. The photocatalytic degradation of dyes, antibiotics and persistent organic pollutants by different modified composites was also analyzed. This review covered the several ways and means in which nano Ag has modified diverse photocatalytic materials as well as the photocatalytic degradation of dyes, antibiotics and persistent organic pollutants. This review identified the drawbacks of the existing nano Ag-modified photocatalytic materials, including their low yield and lack of recyclability, and it also offered suggestions for potential future directions for their improvement. The purpose of this review was to further research on the technology of nano Ag-modified photocatalytic materials and to encourage the creation of new modified photocatalytic nanomaterials for the treatment of organic pollutant degradation.

Exploring the bioactivity of reduced graphene oxide and TiO2 nanocomposite for the regenerative medicinal applications

Millions of people globally suffer from issues related to chronic wounds due to infection, burn, obesity, and diabetes. Nanocomposite with antibacterial and anti-inflammatory properties is a promising material to promote wound healing. This investigation primarily aims to synthesize reduced graphene oxide and titanium dioxide (rGO@TiO2) nanocomposite for wound healing applications. The rGO@TiO2 nanocomposite was synthesized by the one-step hydrothermal technique, and the physicochemical characterization of synthesized nanocomposite was performed by X-ray diffraction, Fourier transforms infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, and dynamic light scattering. Further, the nanocomposite antibacterial, cytotoxicity, and wound-healing properties were analyzed by disc diffusion method, MTT assay, and in vitro scratch assay, respectively. Based on the TEM images, the average particle size of TiO2 nanoparticles was around 9.26 ± 1.83 nm. The characteristics peak of Ti-O-Ti bonds was observed between 500 and 850 cm-1 in the Fourier transforms infrared spectrum. The Raman spectrum of graphene oxide (GO) was obtained for bands D and G at 1354 cm-1 and at 1593 cm-1, respectively. This GO peak intensity was reduced in rGO, revealing the oxygen functional group reduction. Moreover, the rGO@TiO2 nanocomposite exhibited dose-dependent antibacterial properties against the positive and negative bacterium. The cytotoxicity for 5-100 µg/mL of rGO@TiO2 nanocomposite was above the half-maximal inhibitory concentration value. The in vitro scratch assay for rGO@TiO2 indicates that the nanocomposite promotes cell proliferation and migration. The nanocomposite recovered the wound within 48 h. The rGO@TiO2 nanocomposite shows potential materials for wound healing applications.

Nanoremediation strategies to address environmental problems

A rapid rise in population, extensive anthropogenic activities including agricultural practices, up-scaled industrialization, massive deforestation, etc. are the leading causes of environmental degradation. Such uncontrolled and unabated practices have affected the quality of environment (water, soil, and air) synergistically by accumulating huge quantities of organic and inorganic pollutants in it. Environmental contamination is posing a threat to the existing life on the Earth, therefore, demands the development of sustainable environmental remediation approaches. The conventional physiochemical remediation approaches are laborious, expensive, and time-consuming. In this regard, nanoremediation has emerged as an innovative, rapid, economical, sustainable, and reliable approach to remediate various environmental pollutants and minimize or attenuate the risks associated with them. Owing to their unique properties such as high surface area to volume ratio, enhanced reactivity, tunable physical parameters, versatility, etc. nanoscale objects have gained attention in environmental clean-up practices. The current review highlights the role of nanoscale objects in the remediation of environmental contaminants to minimize their impact on human, plant, and animal health; and air, water, and soil quality. The aim of the review is to provide information about the applications of nanoscale objects in dye degradation, wastewater management, heavy metal and crude oil remediation, and mitigation of gaseous pollutants including greenhouse gases.

Green synthesis of lead oxide nanoparticles for photo-electrocatalytic and antimicrobial applications

Synthesis of nanoparticles (NPs) for many different uses requires the development of environmentally friendly synthesis protocols. In this article, we present a simple and environmentally friendly method to synthesize lead oxide (PbO) NPs from the plant material of the Mangifera indica. Analytical techniques such as spectroscopy, X-ray diffraction, and microscopy were used to characterize the synthesized PbO NPs, and their photo-electrocatalytic and antifungal properties were also evaluated. H2O2 was used to investigate the efficacy of removing methylene blue dye. At a range of pH values, H2O2 was used to study the role of hydroxyl radicals in the breakdown of methylene blue dye. Methylene blue dyes are more easily eliminated due to increased generation of the *OH radical during removal. Dye degradation was also significantly affected by the aqueous medium's pH. Additionally, the electrocatalytic properties of the PbO NPs adapted electrode were studied in CH3COONa aqueous solution using cyclic voltammetry. Excellent electrocatalytic properties of the PbO NPs are shown by the unity of the anodic and cathodic peaks of the modified electrode in comparison to the stranded electrode. Aspergillus flavus, Aspergillus niger, and Candida glabrata were some fungi tested with the PbO NPs. Against A. flavus (40%) and A. niger (50%), and C. glabrata (75%), the PbO NPs display an excellent inhibition zone. Finally, PbO NPs were used in antioxidant studies with the powerful antioxidant 2, 2 diphenyl-1-picrylhydrazyl (DPPH). This study presents a simple and environmentally friendly method for synthesizing PbO NPs with multiple uses, including photo-electrocatalytic and antimicrobial activity.

Interface Design of 3D Flower-like Ag@ZnSe Composites: SERS and Photocatalytic Performance

In this work, we cosputtered Ag and ZnSe on a polystyrene template to form a three-dimensional (3D) Ag@ZnSe (x) structure. The 3D surface morphology and material composition that provided abundant "hot spots" were controlled by adjusting the sputtering power of the ZnSe, which was confirmed by finite-difference time-domain (FDTD) simulation. The introduction of ZnSe into the noble metal Ag also introduced a charge-transfer (CT) effect into the system, and the CT path was proven with the two-dimensional correlation spectroscopy (2D-COS)-surface-enhanced Raman scattering (SERS) technique. In addition, the substrate exhibited excellent catalytic activity due to the CT effect. The catalyzed degradation of malachite green (MG) was due to the CT effect in the system, and the catalytic process was successfully monitored by in situ SERS. Most importantly, the catalytic degradation by Ag@ZnSe (x) with different parameters was proportional to the degree of CT (ρ_CT). The SERS and catalytic mechanisms were analyzed in depth with the 2D-COS-SERS technique, which was also useful in verifying the CT process. The catalytic sites for MG were successfully monitored with the 2D-COS-SERS technique. This study provides a reference for studies of the synergistic effects of the electromagnetic mechanism and CT, as well as a new perspective on photocatalysis with dye molecules and monitoring of the catalytic processes.

Ultrasonic Preparation of PN for the Photodegradation of 17β-Estradiol in Water and Biotoxicity Assessment of 17β-Estradiol after Degradation

This study prepares a novel phosphorene (PN) and loads it onto TiO2 to fabricate PN-TiO2 and effectively photodegrade the hydrophobic environmental hormone 17β-estradiol in aqueous solutions. The effect of the PN on degradation efficiency is systematically investigated. It is observed that the doping of TiO2 with PN significantly enhances its photocatalytic and adsorption properties compared with that in the absence of PN; that is, the addition improves the adsorption capability of the composite. The optimal PN weight content is found to be 0.5%. The performance of the PN-TiO2 photocatalyst in degrading E2 is around 67.5%. However, its photodegradation efficiency gradually decreases when the PN content is further increased. This optimal PN content directly suggests synergistic interactions affecting the photodegrading efficiency. Compared with other PN-based photocatalysts mentioned in the literature, this PN-based material possesses striking advantages, such as higher energy efficiency, greater removal capacity, and superior cost-effectiveness. Further, the decrease in the biotoxicity of the water after treatment is evident in observing the development of zebrafish embryos. The studies of the catalyst performed on the zebrafish show that it results in a higher mortality rate at 96 h with a superior hatching rate and healthy fish development. In summary, the prepared PN-based materials exhibited promising photocatalytic capabilities for the removal and biotoxicity reduction of 17β-estradiol in aqueous solutions.

A comprehensive review on sustainable greener nanoparticles for efficient dye degradation

The effluents released from textile industries mainly consist of dyes, metals and other pollutants. Dyes often are discharged in wastewater streams causing adverse effect on the environment. To eliminate these harmful dyes, various techniques are emerging out of which nanotechnology is the most reliable and safer. Nanotechnology offers convincing applications in case of environmental and economic concerns. The bio-synthesis of nanoparticles has several advantages over conventional methods and approach towards environment concern as well. Biological method of nanoparticles synthesis is concluded to be the most promising and efficient in action. Bio-synthesised nanoparticles could be used for treatment and decolourisation of dyes in an efficient manner. This review comprises the study of number of bio-synthesised nanoparticles utilised for degradation of various dyes present as pollutants in wastewater. Bio-synthesised nanoparticles such as gold, silver, iron, cobalt, zinc, titanium and molybdenum used for degradation of various dyes have been discussed in this review.

Recent Advancements in Plant-Derived Nanomaterials Research for Biomedical Applications

Engineering, physics, chemistry, and biology are all involved in nanotechnology, which comprises a wide variety of multidisciplinary scientific field devices. The holistic utilization of metallic nanoparticles in the disciplines of bio-engineering and bio-medicine has attracted a great deal of attention. Medical nanotechnology research can offer immense health benefits for humans. While the advantages of developing nanomaterials have been well documented, it is precisely apparent that there are still some major issues that remain unattended to those need to be resolved immediately so as to ensure that they do not adversely affect living organisms in any manner. The existence of nanoparticles gives them particular value in biology and materials science, as an emerging scientific field, with multiple applications in science and technology, especially with numerous frontiers in the development of new materials. Presented here is a review of recent noteworthy developments regarding plant-derived nanomaterials and their use in the development of medicine and biomedical applications around the world.

Uncaria rhynchophylla mediated Ag/NiO nanocomposites: A new insight for the evaluation of cytotoxicity, antibacterial and photocatalytic applications

The increase of microbial resistance poses threat to the human health. Therefore, the efficient treatment of the microbial resistance is a global challenge and highly desired to explore it. During this study, the Ag/NiO nanocomposite was fabricated via simple and ecofriendly method, using Uncaria rhynchophylla extract as a reducing and capping agent to avoid the aggregation of as synthesized nanomaterials. Here, a range of characterization techniques were employed to characterize the sample which includes UV-vis spectroscopy, X-ray diffraction, FTIR spectroscopy, electron diffraction spectroscopy (EDX), scanning electron microscopy (SEM). Furthermore, the resultant nanocomposite demonstrated an efficient ability for the inhibition of both gram-positive and gram negative pathogenic multidrug resistant bacteria. Additionally, the Ag/NiO nanocomposite showed a durable antioxidant effect against DPPH that could still reach 63% at very low concentration, i.e. 0.5 mg/mL. Interestingly, the synthesized nanocomposite is efficient for the production of reactive oxygen species (ROS) and shows no hemolytic activity. Likewise, the Ag/NiO nanocomposite displayed excellent photocatalytic activity to degrade 85% methylene blue (MB) by 4 mg/25 mL and could be used for waste water treatment. It is believed that synthesized nanostructure with desirable morphology and preparation simplicity can be promising material for the antimicrobial, antioxidant and catalytic applications.

Ag/α-Ag2MoO4/h-MoO3 nanoparticle based microspheres: synthesis and photosensitive properties

We report a new and the most simple strategy for the synthesis of silver molybdate functional composite microspheres based on low molecular weight gelators -amino acids, silver salts and heptamolybdate ions. The resulting material shows a high photocatalytic activity with respect to the methylene blue dye degradation at neutral pH.

Development of Multi-concentration Cu:Ag Bimetallic Nanoparticles as a Promising Bactericidal for Antibiotic-Resistant Bacteria as Evaluated with Molecular Docking Study

The present study is concerned with evaluating the influence of various concentrations of Ag within Cu:Ag bimetallic nanoparticles developed for use as a promising anti-bacterial agent against antibiotic-resistant bacteria. Here, Cu:Ag bimetallic nanoparticles with various concentration ratios (2.5, 5.0, 7.5, and 10 wt%) of Ag in fixed amount of Cu labeled as 1:0.025, 1:0.050, 1:0.075, and 1:0.1 were synthesized using co-precipitation method with ammonium hydroxide and deionized water as solvent, polyvinyl pyrrolidone as a capping agent, and sodium borohydride and ascorbic acid as reducing agents. These formulated products were characterized through a variety of techniques. XRD confirmed phase purity and detected the presence of distinct fcc structures belonging to Cu and Ag phases. FTIR spectroscopy confirmed the presence of vibrational modes corresponding to various functional groups and recorded characteristic peak emanating from the bimetallic. UV-visible spectroscopy revealed reduction in band gap with increasing Ag content. SEM and HR-TEM micrographs revealed spherical morphology of Ag-doped Cu bimetallic with small and large scale agglomerations. The samples exhibited varying dimensions and interlayer spacing. Bactericidal action of synthesized Cu:Ag bimetallic NPs depicted statistically significant (P < 0.05) inhibition zones recorded for various concentrations of Ag dopant against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Acinetobacter baumannii (A. baumannii) ranging from (0.85-2.8 mm), (0.55-1.95 mm) and (0.65-1.85 mm), respectively. Broadly, Cu:Ag bimetallic NPs were found to be more potent against gram-positive compared with gram-negative. Molecular docking study of Ag-Cu bimetallic NPs was performed against β-lactamase which is a key enzyme of cell wall biosynthetic pathway from both S. aureus (Binding score: - 4.981 kcal/mol) and A. bauminnii (Binding score: - 4.013 kcal/mol). Similarly, binding interaction analysis against FabI belonging to fatty acid biosynthetic pathway from A. bauminnii (Binding score: - 3.385 kcal/mol) and S. aureus (Binding score: - 3.012 kcal/mol) along with FabH from E. coli (Binding score: - 4.372 kcal/mol) was undertaken. These theoretical computations indicate Cu-Ag bimetallic NPs as possible inhibitor of selected enzymes. It is suggested that exploring in vitro inhibition potential of these materials may open new avenues for antibiotic discovery.

Photocatalytic and biocidal activities of ZnTiO2 oxynitride heterojunction with MOF-5 and g-C3N4: A case study for textile wastewater treatment under direct sunlight

The work aimed to synthesize three heterojunction photocatalysts (E_g = 2.65-2.78 eV) via in-situ encapsulation of 5% zinc doped titanium oxynitride (Zn_0.05TiO_xN_y) catalyst into MOF-5 and bulk (BCN)/sulfur-doped (SCN) g-C₃N₄ supports using a microwave method. The prepared photocatalysts were characterized and utilized to purify textile industrial wastewater from the organic dye (e.g., methylene blue, MB) and microbial (e.g., E. coli, S. aureus, and C. albicans) contaminants under dark, visible, and solar lights. The output data confirmed the higher activity of Zn_0.05TiO_xN_y@SCN and Zn_0.05TiO_xN_y@MOF-5 for photo-induced microbial growth inactivation (> 90%) under visible light, with photo-biocidal efficiency of 0.91-1.69 mCFU/Einstein. Such a phenomenon is ascribed to the synergism between the high antimicrobial capacity of supports and photoactivity of Zn_0.05TiO_xN_y. Also, Zn_0.05TiO_xN_y@SCN exhibited far superiority to mineralize MB dye (K_photo of 2.73 × 10^-2 min^-1) under direct sunlight due to its high photonic (ζ% of 4.4-8.3%)/quantum (QE of 0.56-0.54%) efficiencies for the generation of hydroxyl and superoxide (^-•O₂/•OH) oxidative species. As a practical case study, all heterojunction photocatalysts also demonstrated high-performance stability (5 cycles) for real textile wastewater treatment under sunlight (efficiency = 76.1-84.6%).

Novel Strategy to Combat Antibiotic Resistance: A Sight into the Combination of CRISPR/Cas9 and Nanoparticles

Antibiotic resistance is a significant crisis that threatens human health and safety worldwide. There is an urgent need for new strategies to control multidrug-resistant (MDR) bacterial infections. The latest breakthrough in gene-editing tools based on CRISPR/Cas9 has potential application in combating MDR bacterial infections because of their high targeting ability to specifically disrupt the drug resistance genes that microbes use for infection or to kill the pathogen directly. Despite the potential that CRISPR/Cas9 showed, its further utilization has been hampered by undesirable delivery efficiency in vivo. Nanotechnology offers an alternative way to overcome the shortcomings of traditional delivery methods of therapeutic agents. Advances in nanotechnology can improve the efficacy and safety of CRISPR/Cas9 components by using customized nanoparticle delivery systems. The combination of CRISPR/Cas9 and nanotechnology has the potential to open new avenues in the therapy of MDR bacterial infections. This review describes the recent advances related to CRISPR/Cas9 and nanoparticles for antimicrobial therapy and gene delivery, including the improvement in the packaging and localizing efficiency of the CRISPR/Cas9 components in the NP (nanoparticle)/CRISPR system. We pay particular attention to the strengths and limitations of the nanotechnology-based CRISPR/Cas9 delivery system to fight nosocomial pathogens.We highlight the need for more scientific research to explore the combinatorial efficacy of various nanoparticles and CRISPR technology to control and prevent antimicrobial resistance.

Photo-functionalized TiO2 nanotubes decorated with multifunctional Ag nanoparticles for enhanced vascular biocompatibility

Titanium dioxide (TiO2) has a long history of application in blood contact materials, but it often suffers from insufficient anticoagulant properties. Recently, we have revealed the photocatalytic effect of TiO2 also induces anticoagulant properties. However, for long-term vascular implant devices such as vascular stents, besides anticoagulation, also anti-inflammatory, anti-hyperplastic properties, and the ability to support endothelial repair, are desired. To meet these requirements, here, we immobilized silver nanoparticles (AgNPs) on the surface of TiO2 nanotubes (TiO2-NTs) to obtain a composite material with enhanced photo-induced anticoagulant property and improvement of the other requested properties. The photo-functionalized TiO2-NTs showed protein-fouling resistance, causing the anticoagulant property and the ability to suppress cell adhesion. The immobilized AgNPs increased the photocatalytic activity of TiO2-NTs to enhances its photo-induced anticoagulant property. The AgNP density was optimized to endow the TiO2-NTs with anti-inflammatory property, a strong inhibitory effect on smooth muscle cells (SMCs), and low toxicity to endothelial cells (ECs). The in vivo test indicated that the photofunctionalized composite material achieved outstanding biocompatibility in vasculature via the synergy of photo-functionalized TiO2-NTs and the multifunctional AgNPs, and therefore has enormous potential in the field of cardiovascular implant devices. Our research could be a useful reference for further designing of multifunctional TiO2 materials with high vascular biocompatibility.

Biosynthesis of silver capped magnesium oxide nanocomposite using Olea cuspidata leaf extract and their photocatalytic, antioxidant and antibacterial activity

Green chemistry is a modern area of research which covers synthesis of nanomaterials through useful, environmentally, economically friendly techniques and their use in different fields. The synthesis involves the formation of bimetallic nanomaterials to enhance their synergistic relationship and achieve special modulated properties. That's why bimetallic nanomaterials are extremely important and gaining interest among researchers in the field of medicinal chemistry for the treatment of various diseases. In this particular study, bimetallic nanoparticles synthesis was done by reduction procedure using leaf extract of Olea cuspidata. The phytochemicals in leaf extract act as stabilizing and capping agent in reduction of precursor's salts. The characterization of green synthesized Ag@MgO nanocomposite was done through several analytical techniques such as ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), High resolution transmission electron microscope (HRTEM) and Zeta potential. To explore the biological potential of synthesized nanocomposite, antibacterial activities against gram negative (Escherichia coli) bacteria and gram positive (Staphylococcus aureus) has been evaluated. The photocatalytic activity in contrary to methylene blue (MB) decomposition was seen efficiently. Moreover, the antioxidant nature of green synthesized Ag@MgO nanocomposite was analyzed by destabilizing and scavenging maximum percentage (93 %) of dangerous and harmful 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The best and surprising results provided the information for the presence of essential and vital components in Olea Cuspidata in the form of organic acids (Citrus Acid) aids in stabilizing the entire structure with enhanced properties. Up to the best of our knowledge, the facts and results obtained regarding the structure of Ag@MgO nanocomposite clearly illustrates the uniqueness of green chemistry and also its role in future developing multifunctional nanoparticles in the field of nanobiotechnology.

Facile synthesis and defect optimization of 2D-layered MoS2 on TiO2 heterostructure for industrial effluent, wastewater treatments

Current research is paying much attention to heterojunction nanostructures. Owing to its versatile characteristics such as stimulating morphology, affluent surface-oxygen-vacancies and chemical compositions for enhanced generation of reactive oxygen species. Herein, we report the hydrothermally synthesized TiO₂@MoS₂ heterojunction nanostructure for the effective production of photoinduced charge carriers to enhance the photocatalytic capability. XRD analysis illustrated the crystalline size of CTAB capped TiO₂, MoS₂@TiO₂ and L-Cysteine capped MoS₂@TiO₂ as 12.6, 11.7 and 10.2 nm, respectively. The bandgap of the samples analyzed by UV–Visible spectroscopy are 3.57, 3.66 and 3.94 eV. PL spectra of anatase phase titania shows the peaks present at and above 400 nm are ascribed to the defects in the crystalline structure in the form of oxygen vacancies. HRTEM reveals the existence of hexagonal layered MoS₂ formation on the spherical shaped TiO₂ nanoparticles at the interface. X-ray photoelectron spectroscopy recommends the chemical interactions between MoS₂ and TiO_2, specifically, oxygen vacancies. In addition, the electrochemical impedance spectroscopy studies observed that L-MT sample performed low charge transfer resistance (336.7 Ω cm²) that promotes the migration of electrons and interfacial charge separation. The photocatalytic performance is evaluated by quantifying the rate of Congo red dye degradation under visible light irradiation, and the decomposition efficiency was found to be 97%. The electron trapping recombination and plausible photocatalytic mechanism are also explored, and the reported work could be an excellent complement for industrial wastewater treatment.

Phytomediated Photo-Induced Green Synthesis of Silver Nanoparticles Using Matricaria chamomilla L. and Its Catalytic Activity against Rhodamine B

The bio-fabrication of silver nanoparticles (AgNPs) was carried out through the facile green route, using the aqueous extract of Matricaria chamomilla L. Herein, we have developed a cost-efficient, ecofriendly, and photo-induced method for the biomolecule-assisted synthesis of AgNPs using an aqueous extract of Matricaria chamomilla L. as a bio-reducing and capping/stabilizing agent. The biomolecule-capped AgNPs were confirmed from the surface plasmon resonance (SPR) band at λmax = 450 nm using a UV-visible spectrometer. The stability of the AgNPs was confirmed by recording the UV-visible spectra for a more extended period, and no precipitation was observed in the sol. The morphology and structure of photo-induced biomolecule-capped AgNPs were characterized by different microscopic and spectroscopy techniques such as TEM, SEM, EDX, XRD, and FTIR analysis. The role of phytochemicals as reducing and stabilizing agents was confirmed by comparative FTIR analysis of the AgNPs and pure Matricaria chamomilla L. aqueous extract. The obtained result shows that the AgNPs are mostly spherical morphology with an average size of about 26 nm. Furthermore, the thermal stability of biomolecule-capped AgNPs was examined by TGA-DTG analysis that showed a weight loss of approximately 36.63% up to 800 °C. Moreover, the potential photocatalytic activity of photo-induced AgNPs against Rhodamine B (RB) was examined in the presence of UV light irradiation. The catalyst reusability, the effect of catalyst dosage and initial dye concentration, and the effect of the temperature and pH of the reaction medium were also assessed.

Beyond the Nanomaterials Approach: Influence of Culture Conditions on the Stability and Antimicrobial Activity of Silver Nanoparticles

Silver nanoparticles (AgNPs) as antimicrobial agents have been extensively studied. It is generally assumed that their inhibitory activity heavily depends on their physicochemical features. Yet, other parameters may affect the AgNP traits and activity, such as culture medium composition, pH, and temperature, among others. In this work, we evaluated the effect of the culture medium physicochemical traits on both the stability and antibacterial activity of AgNPs. We found that culture media impact the physicochemical traits of AgNPs, such as hydrodynamic size, surface charge, aggregation, and the availability of ionic silver release rate. As a consequence, culture media play a major role in AgNP stability and antimicrobial potency. The AgNP minimal inhibitory concentration (MIC) values changed up to 2 orders of magnitude by the influence of culture media alone when single-stock AgNPs were tested on the same strain of Escherichia coli. Furthermore, a meta-analysis of the AgNP MIC values confirms that the "chemical complexity" of culture media influences the AgNP activity. Studies that address only the antimicrobial activities of nanoparticles on common bacterial models should be performed by standardized susceptibility assays, thus generating replicable, comparable reports regarding the antimicrobial potency of nanomaterials.

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

Gram-scale synthesis of splat-shaped Ag-TiO2 nanocomposites for enhanced antimicrobial properties

The control over contagious diseases caused by pathogenic organisms has become a serious health issue. The extensive usage of antibiotics has led to the development of multidrug-resistant bacterial strains. In this regard, metal-oxide-based antibacterial nanomaterials have received potential research interest due to the efficient prevention of microorganism growth. In this study, splat-shaped Ag-TiO₂ nanocomposites (NCs) were synthesized on the gram scale and the enhanced antibacterial properties of TiO₂ in the presence of silver were examined. The formation of Ag-TiO₂ NCs was analyzed through various characterization techniques. The cell viability experimental results demonstrated that the Ag-TiO₂ NCs have good biocompatibility. The antibacterial activity of the prepared Ag-TiO₂ NCs was tested against the Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacterial strains. The Ag-TiO₂ NCs exhibited promising and superior antibacterial properties compared to TiO₂ nanospheres as confirmed by the bacterial growth and inhibition zone. The improvement in the antibacterial activity was attributed to the synergistic effect of the hybrid nature of TiO₂ nanoparticles in the presence of Ag.

Antimicrobial Metal Nanomaterials: From Passive to Stimuli-Activated Applications

The development of antimicrobial drug resistance among pathogenic bacteria and fungi is one of the most significant health issues of the 21st century. Recently, advances in nanotechnology have led to the development of nanomaterials, particularly metals that exhibit antimicrobial properties. These metal nanomaterials have emerged as promising alternatives to traditional antimicrobial therapies. In this review, a broad overview of metal nanomaterials, their synthesis, properties, and interactions with pathogenic micro-organisms is first provided. Secondly, the range of nanomaterials that demonstrate passive antimicrobial properties are outlined and in-depth analysis and comparison of stimuli-responsive antimicrobial nanomaterials are provided, which represent the next generation of microbiocidal nanomaterials. The stimulus applied to activate such nanomaterials includes light (including photocatalytic and photothermal) and magnetic fields, which can induce magnetic hyperthermia and kinetically driven magnetic activation. Broadly, this review aims to summarize the currently available research and provide future scope for the development of metal nanomaterial-based antimicrobial technologies, particularly those that can be activated through externally applied stimuli.

Untouchability of natural spa waters: Perspectives for treatments within a personalized water safety plan

Natural SPA waters and their environments were known since ancient times and used for health or recreational purposes in different societies, worldwide. The composition and uses of these spring waters may not allow standard disinfection in pools, representing a challenge for hygiene management. Several safety and quality procedures were proposed, but a systematic approach is still needed. Here, we focus on alternative strategies to provide hints for developing a sustainable Water Safety Plan, based on intrinsic water properties and photocatalytic materials. The antimicrobial activity of four different SPA waters with high mineral content and one drinkable spring water with a low mineral content, was assessed and then tested for the additional bactericidal activity of Titanium Dioxide (TiO₂) nanomaterials and/or light exposure at different wavelengths (200-635 nm). A native antibacterial activity was observed in all high mineral content waters, with a CFU reduction of 75-80%. The bactericidal action of TiO₂ showed an additional incremental effect, with a reduction of over 99% within 2-5 h. Interestingly, the antibacterial photocatalytic effect was detected also in the visible light range, with a possible pick around 450-455 nm, blue-light. Based on observed results, we propose a model for developing a water safety plan, considering water properties and bather exposure. This candidate approach is personalized on water composition and pool use, trying to avoid chemical disinfectants. Photocatalytic nanotechnologies represent one of the promising alternative treatments and can provide novel perspectives for a sustainable managing of natural SPA water hygiene.

A simple sensing of hazardous photo-induced superoxide anion radicals using a molecular probe in ZnO-Nanoparticles aqueous medium

The generation of reactive oxygen species (ROS) during the photolysis of sunscreens and sun blockers poses consumer safety concerns while necessitating proper identification and quantitation of ROS species. Here, a colorimetric sensing approach has been developed based on a molecular probe (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2-H-tetrazolium-5-carboxanilide (XTT) tetrazolium salt) to quantitatively measure the photo-induced superoxide anion radicals (O₂^.) generated from the photocatalysis of zinc oxide nanoparticles (ZnO-NPs) in aqueous solutions. Note that superoxide anion radicals are assumed to be the main reactive oxygen species (ROS) generated from such photocatalysis. The characterisation of ZnO-NPs before and after irradiation showed average particle sizes of 616.5 and 295.3 nm and ζ-potential values of 0 and -24.4 mV, respectively. It is hoped that this proposed protocol can be further developed to efficiently detect other ROS present in inorganic sun blockers and to optimize the utility of various sunscreen formulations.

Antimicrobial Applications of Clay Nanotube-Based Composites

Halloysite nanotubes with different outer surface/inner lumen chemistry (SiO₂/Al₂O₃) are natural objects with a 50 nm diameter hollow cylindrical structure, which are able to carry functional compounds both inside and outside. They are promising for biological applications where their drug loading capacity combined with a low toxicity ensures the safe interaction of these nanomaterials with living cells. In this paper, the antimicrobial properties of the clay nanotube-based composites are reviewed, including applications in microbe-resistant biocidal textile, paints, filters, and medical formulations (wound dressings, drug delivery systems, antiseptic sprays, and tissue engineering scaffolds). Though halloysite-based antimicrobial materials have been widely investigated, their application in medicine needs clinical studies. This review suggests the scalable antimicrobial nano/micro composites based on natural tubule clays and outlines research and development perspectives in the field.

Efficient removal of dyes from dyeing wastewater by powder activated charcoal/titanate nanotube nanocomposites: adsorption and photoregeneration

Effective removal of dyes has been widely investigated by the adsorption of powder activated carbon and photodegradation by titanate nanotubes (TNTs). In this study, a facile one-step alkaline-hydrothermal method was applied to synthesize powder activated charcoal-supported TNTs (TNTs@PAC). Adsorption of three representative dyes, i.e., cationic methylene blue (MB), cationic rhodamine B (RhB), and anionic methyl orange (MO), onto TNTs@PAC was evaluated by the adsorption kinetic experiments and adsorption isotherms. The first 30 min is the main time phase of adsorption, and MB, RhB, and MO obtained the experimental equilibrium uptake of 173.30, 115.06, and 106.85 mg/g, respectively, indicating their final removal efficiencies of 100%, 69.36%, and 64.11%, respectively. The increase of pH value reduced adsorption capacity of MO (from 149.35 mg/g at pH of 2 to 96.99 mg/g at pH of 10), but facilitated MB adsorption, which was attributed to the charge distribution on the surface of TNTs@PAC and the charge of dyes at different pH. Furthermore, good capacity recoveries of MB by TNTs@PAC (> 99%) were observed after UV irradiation treatment, indicating the used TNTs@PAC can be easily recycled for the adsorption of MB by UV irradiation. Overall, TNTs@PAC is an effective process for remediation of dye-contaminated water because of its adsorption performance for all selected dyes and good regeneration capacity for MB.

Greener synthesis of ZnO and Ag-ZnO nanoparticles using Silybum marianum for diverse biomedical applications

AIM

To investigate the physical and biological properties of Silybum marianum inspired ZnO nanoparticles (NPs), Ag-ZnO heterostructures. Experiment: Nanoparticles were characterized using ultraviolet-visible and infrared spectroscopy, x-ray diffraction, high resolution electron microscopy, ζ potential and thermo-gravimetric analysis etc. Results: Ag-ZnO-NPs indicated slightly higher antimicrobial potential then ZnO-NPs. Good antileishmanial (IC50 = 246 μg/ml for Ag-ZnO; 341 μg/ml for ZnO) and antioxidant potential while moderate enzyme inhibition is reported. 2, 2-Diphenyl 1-picrylhydrazyl radical scavenging of Ag-ZnO was higher relative to ZnO-NPs. Nanocosmaceutical formulation of nanoparticles indicated stable antimicrobial performance.

CONCLUSION

Biosynthesized nanoparticles indicated interesting biological properties and should be subjected to further research to establish their pharmacological relevance.

From biotechnology principles to functional and low-cost metallic bionanocatalysts

Chemical, physical and mechanical methods of nanomaterial preparation are still regarded as mainstream methods, and the scientific community continues to search for new ways of nanomaterial preparation. The major objective of this review is to highlight the advantages of using green chemistry and bionanotechnology in the preparation of functional low-cost catalysts. Bionanotechnology employs biological principles and processes connected with bio-phase participation in both design and development of nano-structures and nano-materials, and the biosynthesis of metallic nanoparticles is becoming even more popular due to; (i) economic and ecologic effectiveness, (ii) simple one-step nanoparticle formation, stabilisation and biomass support and (iii) the possibility of bio-waste valorisation. Although it is quite difficult to determine the precise mechanisms in particular biosynthesis and research is performed with some risk in all trial and error experiments, there is also the incentive of understanding the exact mechanisms involved. This enables further optimisation of bionanoparticle preparation and increases their application potential. Moreover, it is very important in bionanotechnological procedures to ensure repeatability of the methods related to the recognised reaction mechanisms. This review, therefore, summarises the current state of nanoparticle biosynthesis. It then demonstrates the application of biosynthesised metallic nanoparticles in heterogeneous catalysis by identifying the many examples where bionanocatalysts have been successfully applied in model reactions. These describe the degradation of organic dyes, the reduction of aromatic nitro compounds, dehalogenation of chlorinated aromatic compounds, reduction of Cr(VI) and the synthesis of important commercial chemicals. To ensure sustainability, it is important to focus on nanomaterials that are capable of maintaining the important green chemistry principles directly from design inception to ultimate application.

Plasmon enhanced photocatalytic and antimicrobial activities of Ag-TiO2 nanocomposites under visible light irradiation prepared by DBD cold plasma treatment

Silver nanoparticles (Ag NPs) have been deposited on powder P25 by a novel two-step method involving a precipitation reaction and atmospheric pressure dielectric barrier discharge (DBD) cold plasma treatment without the use of any environmentally and biologically hazardous reducing agents. The silver precursor is formed in the processing of precipitation reaction and then completely reduced to the metallic state by atmospheric pressure DBD cold plasma treatment as proved by X-ray photoelectron spectroscopy, UV-Visible absorption spectra and HRTEM analyses. TEM images indicate that the Ag NPs with average diameter of 3.7 nm were deposited on powder P25 with high dispersion although no reducing agents, stabilizers or surfactants were used. The prepared products show remarkable improvement for methylene blue (MB) photodegradation and effective inhibition of bacterias against Escherichia coli and Staphylococcus aureus.

A comprehensive review on the use of second generation TiO2 photocatalysts: Microorganism inactivation

Photocatalytic disinfection practices have been applied for decades and attract current interest along with the developments in synthesis of novel photocatalysts. A survey based investigation was performed for elucidation of photocatalytic treatment details as well as disinfection mechanism of microorganisms. The present work brings significant information on the utilization of second generation TiO₂ photocatalysts for inactivation of microorganisms typically using E. coli as the model microorganism. Special interest was devoted to the role of organic matrix either generated during treatment or as a natural component. Studies on photocatalytic disinfection were extensively reviewed and evaluated with respect to basic operational parameters related to photocatalysis, and types and properties of microorganisms investigated. Degradation mechanism and behavior of microorganisms towards reactive oxygen species during disinfection and organic matrix effects were also addressed. For successful utilization and effective assessment of visible light active photocatalysts, standard protocols for disinfection activity testing have to be set. Further improvement of the efficiency of these materials would be promising for future applications in water treatment processes.

Biosynthesis of bimetallic and core-shell nanoparticles: their biomedical applications - a review

Recently, researchers succeeded in designing and manufacturing a new class of nanoparticles (NPs) called hybrid NPs. Among hybrid NPs, bimetallic and core-shell NPs were a revolutionary step in NPs science. A large number of green physiochemical and methods for nanostructures synthesis have been published. Eventually, physiochemical methods are either expensive or require the use of chemical compounds for the synthesis of bimetallic and core-shell nanostructures. The main challenges that scientists are facing are making the process cheaper, facile and eco-friendly efficient synthesis process. Green synthesis (biosynthesis) refers to the use of bio-resources (such as bacteria, fungi, plants or their derivatives) for the synthesis of nanostructures. The popularity of the green synthesis of nanostructures is due to their environmental friendliness and no usage of toxic materials, environmental friendliness for the synthesis or stability of nanostructure. Bimetallic and core-shell NPs have many biomedical applications such as removing heavy metals, parasitology, molecular and microbial sensor, gene carrier, single bacterial detection, oligonucleotide detection and so on. The purpose of this study is to discuss briefly the biosynthesised bimetallic and core-shell NPs, their biomedical applications.

Recent Progress on Titanium Dioxide Nanomaterials for Photocatalytic Applications

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO₂ under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO₂ and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO₂ to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO₂ -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO₂ -based materials further.