Photocatalytic antibacterial performance of Sn(4+)-doped TiO(2) thin films on glass substrate

Review of research advances in microbial sterilization technologies and applications in the built environment

As globalization accelerates, microbial contamination in the built environment poses a major public health challenge. Especially since Corona Virus Disease 2019 (COVID-19), microbial sterilization technology has become a crucial research area for indoor air pollution control in order to create a hygienic and safe built environment. Based on this, the study reviews sterilization technologies in the built environment, focusing on the principles, efficiency and applicability, revealing advantages and limitations, and summarizing current research advances. Despite the efficacy of single sterilization technologies in specific environments, the corresponding side effects still exist. Thus, this review highlights the efficiency of hybrid sterilization technologies, providing an in-depth understanding of the practical application in the built environment. Also, it presents an outlook on the future direction of sterilization technology, including the development of new methods that are more efficient, energy-saving, and targeted to better address microbial contamination in the complex and changing built environment. Overall, this study provides a clear guide for selecting technologies to handle microbial contamination in different building environments in the future, as well as a scientific basis for developing more effective air quality control strategies.

Efficient and sustainable photocatalytic inactivation of E. coli by an innovative immobilized Ag/TiO2 photocatalyst with peroxymonosulfate (PMS) under visible light

A novel catalytic system for effective photocatalytic inactivation of Escherichia coli (E. coli) was constructed by anchoring Ag nanoparticles (AgNPs) on silane coupling agent (SCA) pretreated TiO2 nano-tube arrays (Ag/SCA/TiO2NTAs). Morphology and structural analyses revealed that SCA could disperse AgNPs evenly on TiO2NTAs, thus inducing a superior surface plasmon resonance (SPR) effect. Ag/SCA/TiO2NTAs catalyst exhibited excellent inactivation performance when in the presence of peroxymonosulfate (PMS) and visible light (VL), with 6-log E. coli was completely inactivated within 60 min, which was 5.3, 12.5 and 13.2 times higher than that of Ag/SCA/TiO2NTAs/VL, PMS/VL and Ag/SCA/TiO2NTAs/PMS/dark systems, respectively. Additionally, the photocatalyst exhibited a highly reusable property, with the inactivation performance almost unchanged after ten cycles of uses with minimal Ag leaching. The inactivation mechanism analysis demonstrated that both radical (SO4•-, OH) and non-radical (h+, 1O2) pathways involved in E. coli inactivation, and SCA played a pivotal role in the production of reactive species. Chloride ions (Cl-) greatly enhanced the inactivation efficiency, while bicarbonate (HCO3-) and phosphate (H2PO4-) showed an inhibitory effect. Humic acid (HA) displayed a dual effect on inactivation performance, where the low concentration of HA facilitated the bacteria inactivation, while the higher dose suppressed bacteria inactivation. Moreover, the system exhibited excellent inactivation performance in tap water. This work first used SCA as the binder to fix AgNPs on TiO2NTAs for VL photocatalytic inactivation of bacteria with the assistance of PMS, which was expected to provide some insights into the practical treatment of drinking water.

ZrO2/ZnO/TiO2 Nanocomposite Coatings on Stainless Steel for Improved Corrosion Resistance, Biocompatibility, and Antimicrobial Activity

The ultrathin nanocomposite coatings made of zirconium oxide (ZrO₂), zinc oxide (ZnO), and titanium oxide (TiO₂) on stainless steel (SS) were prepared by the radio frequency sputtering method, and the effects of the nanocomposite coating on corrosion protection and antibacterial activities of nanocomposite coated SS were investigated. Scanning electron microscopy was conducted to observe surface morphology of nanocomposite coatings with distinct distribution of grains with the formation on SS substrate. From the electrochemical impedance spectroscopy results, ZrO₂/ZnO/TiO₂ nanocomposite coating showed excellent corrosion protection performance at 37 °C during immersion in simulated body fluid and saliva solution for 12 and 4 weeks, respectively. The impedance of ZrO₂/ZnO/TiO₂ (40/10/50) nanocomposite coated SS exhibited values about 5 orders of magnitude higher than that of uncoated SS with polarization at the low-frequency region. Cell viability of ZrO₂/ZnO/TiO₂ nanocomposite coated SS was examined under mouse fibroblasts culture (L929), and it was observed that the nanocomposite coating improves proliferation through effective cellular attachment compared to uncoated SS. From the antimicrobial activity results, ZrO₂/ZnO/TiO₂ nanocomposite-coated SS showed killing efficiency of 81.2% and 72.4% against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, respectively.

Photocatalytic nanoparticles - From membrane interactions to antimicrobial and antiviral effects

As a result of increasing resistance among pathogens against antibiotics and anti-viral therapeutics, nanomaterials are attracting current interest as antimicrobial agents. Such materials offer triggered functionalities to combat challenging infections, based on either direct membrane action, effects of released ions, thermal shock induced by either light or magnetic fields, or oxidative photocatalysis. In the present overview, we focus on photocatalytic antimicrobial effects, in which light exposure triggers generation of reactive oxygen species. These, in turn, cause oxidative damage to key components in bacteria and viruses, including lipid membranes, lipopolysaccharides, proteins, and DNA/RNA. While an increasing body of studies demonstrate that potent antimicrobial effects can be achieved by photocatalytic nanomaterials, understanding of the mechanistic foundation underlying such effects is still in its infancy. Addressing this, we here provide an overview of the current understanding of the interaction of photocatalytic nanomaterials with pathogen membranes and membrane components, and how this translates into antibacterial and antiviral effects.

Cetylpyridinium Trichlorostannate: Synthesis, Antimicrobial Properties, and Controlled-Release Properties via Electrical Resistance Tomography

Cetylpyridinium trichlorostannate (CPC-Sn), comprising cetylpyridinium chloride (CPC) and stannous chloride, was synthesized and characterized via single-crystal X-ray diffraction measurements indicating stoichiometry of C₂₁H₃₈NSnCl₃ where the molecules are arranged in a 1:1 ratio with a cetylpyridinium cation and a [SnCl₃]^- anion. CPC-Sn has shown potential for application as a broad-spectrum antimicrobial agent, to reduce bacteria-generated volatile sulfur compounds and to produce advanced functional materials. In order to investigate its controlled-release properties, electrical resistance tomography was implemented. The results demonstrate that CPC-Sn exhibits extended-release properties in an aqueous environment as opposed to the CPC counterpart.

Alternatives to Conventional Antibiotic Therapy: Potential Therapeutic Strategies of Combating Antimicrobial-Resistance and Biofilm-Related Infections

Antibiotics have been denoted as the orthodox therapeutic agents for fighting bacteria-related infections in clinical practices for decades. Nevertheless, overuse of antibiotics has led to the upsurge of species with antimicrobial resistance (AMR) or multi-drug resistance. Bacteria can also grow into the biofilm, which accounts for at least two-thirds of infections. Distinct gene expression and self-produced heterogeneous hydrated extracellular polymeric substance matrix architecture of biofilm contribute to their tolerance and externally manifest as antibiotic resistance. In this review, the difficulties in combating biofilm formation and AMR are introduced, and novel alternatives to antibiotics such as metal nanoparticles and quaternary ammonium compounds, chitosan and its derivatives, antimicrobial peptides, stimuli-responsive materials, phage therapy and other therapeutic strategies, from compounds to hydrogel, from inorganic to biological, are discussed. We expect to provide useful information for the readers who are seeking for solutions to the problem of AMR and biofilm-related infections.

Influence of terbium (III) ions on the photocatalytic activity of TiO2 and CeO2 for the degradation of methylene blue in industrial effluents

This study reports the preparation of TiO₂ and CeO₂ doped with different quantities of terbium and discusses the influence of this dopant on the photocatalytic activity of the semiconductors, with respect to the degradation of methylene blue, under ultraviolet and solar radiations. The oxides obtained were characterized by X-ray diffraction, infrared vibrational spectroscopy, diffuse reflectance spectroscopy, scanning electron microscopy, and dispersive energy spectroscopy. The results indicate that the presence of the dopant in TiO₂ favored the formation of the anatase crystalline phase to the detriment of rutile, increased the band gap energy, and decreased the size of the nanoparticles. Doping CeO₂ with Tb resulted in a fluorite-type crystalline structure, reduced band gap, and smaller particle size. The photocatalytic activity decreases as the concentration of terbium increases regardless of the radiation source and nature of the oxide. Furthermore, a better performance was observed for all semiconductors excited by solar radiation in comparison to ultraviolet light. The samples of pure TiO₂ and TiO₂ doped with 0.5 and 1% terbium showed total removal of the dye after less than 120 min of reaction, while the samples of pure CeO₂ and CeO₂ doped with 0.5% terbium showed approximately 80% and 57% of dye removal after 120 min, suggesting that these materials can be promising for the treatment of industrial effluents.

Lipid peroxidation metabolites associated with biomarkers of inflammation and oxidation stress in workers handling carbon nanotubes and metal oxide nanoparticles

The purpose of this study was to assess the effects of lipid peroxidation with occupational exposure to different types of nanomaterials (NMs). In this cross-sectional study, urine and exhaled breath condensate (EBC) samples were collected from 80 NM-handling workers [30 workers handling nano-titanium oxide (nano-TiO₂), 28 handling nano-silicon dioxide (nano-SiO₂), 22 handling carbon nanotubes (CNTs)], and 69 controls (office workers) from 2010 to 2012. Urinary 8-isoPGF_2α, 2,3 dinor-8-isoPGF_2α, PGF_2α, and EBC 8-iso PGF_2α were measured as lipid peroxidation biomarkers in 2013. A significant positive correlation was found between 8-isoPGF_2α, 2,3 dinor-8-isoPGF_2α, PGF_2α, and total isoprostane in urine. Furthermore, significant positive correlations were noted between EBC 8-iso PGF_2α and urinary 2,3 dinor-8-isoPGF_2α (Spearman correlation r = 0.173, p = 0.035). Exposure to nano-TiO₂ resulted in significantly higher levels of urinary 8-isoPGF_2α, 2,3 dinor-8-isoPGF_2α and PGF_2α, even after controlling for confounding factors. Moreover, significant associations and exposure intensity-response relationships between EBC 8-iso PGF_2α and NMs were observed in workers, whether handling nano-TiO₂, nano-SiO₂, or CNTs. Among them, the significant trends were identified based on the intensity of risk levels. These results provided evidence that exposure to nano-TiO₂, nano-SiO₂, and CNTs may lead to lipid peroxidation in EBC. For routine biomonitoring purposes, this finding, which came through noninvasive methods, may be useful for workers exposed to NMs.HighlightsData regarding the effects of nano-titanium oxide (nano-TiO₂), nano-silicon dioxide (nano-SiO₂), and carbon nanotubes (CNTs) on lipid peroxidation in workers are limited.8-Iso PGF_2α in exhaled breath condensate of workers exposed to nanoparticles was higher than that of office workers.Exposure to titanium oxide (TiO₂) and silica (SiO₂) may lead to lipid peroxidation, as indicated by 8-isoPGF_2α, 2,3 dinor-8-isoPGF_2α, and PGF_2α.Examination of lipid peroxidation in EBC has seems to be a useful technique for noninvasive monitoring of workers exposed to nanoparticles.

Enhanced Photocatalytic and Antibacterial Activities of K2Ti6O13 Nanowires Induced by Copper Doping

Cu-doped K2Ti6O13 (Cu–KTO) nanowires were prepared using a combination of sol–gel and hydrothermal methods to improve the photocatalytic and antibacterial performance of K2Ti6O13 (KTO) nanowires. The Cu–KTO nanowires maintained the monoclinic structure of KTO. The Cu2+ ions could enter into the lattice of KTO by substituting for certain Ti4+ ions and cause the formation of defects and oxygen vacancies. The UV–Visible absorption spectra showed that after Cu doping, the absorption edge of KTO moved to the visible region, indicating that the band gap decreased and the ability to absorb visible light was acquired. The photocatalytic properties of the Cu–KTO nanowires with different doping amounts were assessed by simulating the photodegradation of rhodamine B (RhB) under simulated sunlight irradiation. The 1.0 mol% Cu–KTO nanowires showed the best photocatalytic performance, and 91% of RhB was decomposed by these nanowires (the catalyst dose was only 0.3 g/L) within 5 h. The performance of the Cu–KTO nanowires was much better than that of the KTO nanowires. The Cu–KTO nanowires also showed high antibacterial activity for Escherichia coli (ATCC 25922) of up to 99.9%, which was higher than that of the pure KTO samples. Results proved that Cu doping is an effective means to develop multifunctional KTO nanomaterials. It can be used to degrade organic pollutants and remove harmful bacteria simultaneously in water environments.

Toxicity and mechanisms of action of titanium dioxide nanoparticles in living organisms

Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will inevitably cause damage to organisms and ecosystems. A better understanding of TiO₂ NP toxicity in living organisms may promote risk assessment and safe use practices of these nanomaterials. This review summarizes the toxic effects of TiO₂ NPs on multiple taxa of microorganisms, algae, plants, invertebrates, and vertebrates. The mechanism of TiO₂ NP toxicity to organisms can be outlined in three aspects: The Reactive Oxygen Species (ROS) produced by TiO₂ NPs following the induction of electron-hole pairs; cell wall damage and lipid peroxidation of the cell membrane caused by NP-cell attachment by electrostatic force owing to the large surface area of TiO₂ NPs; and TiO₂ NP attachment to intracellular organelles and biological macromolecules following damage to the cell membranes.

Research progress of photocatalytic sterilization over semiconductors

With increasingly serious environmental issues, practical applications of semiconductor photocatalysts for environmental purification have attracted broad attention. Semiconductor photocatalysts for the disinfection of soil surfaces, air and water are of great interest.

Bacteriostatic Activity of LLDPE Nanocomposite Embedded with Sol⁻Gel Synthesized TiO₂/ZnO Coupled Oxides at Various Ratios

Metal oxide-polymer nanocomposite has been proven to have selective bactericidal effects against the main and common pathogens (Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli)) that can cause harmful infectious diseases. As such, this study looked into the prospect of using TiO₂/ZnO with linear low-density polyethylene (LLDPE) to inactivate S. aureus and E. coli. The physical, structural, chemical, mechanical, and antibacterial properties of the nanocomposite were investigated in detail in this paper. The production of reactive species, such as hydroxyl radicals (•OH), holes (h⁺), superoxide anion radicals (O₂•¯), and zinc ion (Zn2+), released from the nanocomposite were quantified to elucidate the underlying antibacterial mechanisms. LLDPE/25T75Z with TiO₂/ZnO (1:3) nanocomposite displayed the best performance that inactivated S. aureus and E. coli by 95% and 100%, respectively. The dominant reactive active species and the zinc ion release toward the superior antibacterial effect of nanocomposite are discussed. This work does not only offer depiction of the effective element required for antimicrobial biomedical appliances, but also the essential structural characteristics to enhance water uptake to expedite photocatalytic activity of LLDPE/metal oxide nanocomposite for long term application.

pH-Induced Switchable Superwettability of Efficient Antibacterial Fabrics for Durable Selective Oil/Water Separation

The superhydrophobic antibacterial fabrics with intelligent switchable wettability were fabricated by the cross-link reaction among pH-responsive antibacterial copolymer tethered hydroxyl groups, methylol-contained poly(ureaformaldehyde) nanoparticles (PUF NPs), and hexamethylene diisocyanate. It was found that the surface concentration of N⁺ were heavily influenced by acid solutions, resulting in the rapid wettability conversion from superhydrophobicity/superoleophilicity to superhydrophilicity/underwater superoleophobicity in a remarkably short time. The above responsiveness feature of coated cotton fabric contributes a prominent selective oil/water separation property, and the separation efficiency invariably remained at greater than 95% even after 20 reuse cycles, which exhibited brilliant durability. More importantly, the coated cotton fabric possessed excellent self-cleaning performance after contamination by oil and held high bactericidal rate (more than 80%) regardless of pH treatment, and thus could abate the surface biological pollution caused by bacteria proliferation. The attractive properties of the prepared smart superwetting materials shows great promise for potential application in oil/water separation from an environmental-protection perspective.

Copper doping enhanced the oxidative stress-mediated cytotoxicity of TiO2 nanoparticles in A549 cells

Physicochemical properties of titanium dioxide nanoparticles (TiO₂ NPs) can be tuned by doping with metals or nonmetals. Copper (Cu) doping improved the photocatalytic behavior of TiO₂ NPs that can be applied in various fields such as environmental remediation and nanomedicine. However, interaction of Cu-doped TiO₂ NPs with human cells is scarce. This study was designed to explore the role of Cu doping in cytotoxic response of TiO₂ NPs in human lung epithelial (A549) cells. Characterization data demonstrated the presence of both TiO₂ and Cu in Cu-doped TiO₂ NPs with high-quality lattice fringes without any distortion. The size of Cu-doped TiO₂ NPs (24 nm) was lower than pure TiO₂ NPs (30 nm). Biological results showed that both pure and Cu-doped TiO₂ NPs induced cytotoxicity and oxidative stress in a dose-dependent manner. Low mitochondrial membrane potential and higher caspase-3 enzyme (apoptotic markers) activity were also observed in A549 cells exposed to pure and Cu-doped TiO₂ NPs. We further observed that cytotoxicity caused by Cu-doped TiO₂ NPs was higher than pure TiO₂ NPs. Moreover, antioxidant N-acetyl cysteine effectively prevented the reactive oxygen species generation, glutathione depletion, and cell viability reduction caused by Cu-doped TiO₂ NPs. This is the first report showing that Cu-doped TiO₂ NPs induced cytotoxicity and oxidative stress in A549 cells. This study warranted further research to explore the role of Cu doping in toxicity mechanisms of TiO₂ NPs.

Improved corrosion resistance and antibacterial properties of composite arch-wires by N-doped TiO2coating

In this paper, composite arch-wires (CAWs) coated with TiO₂and N-doped TiO₂nanocrystal thin films were fabricated.

Preparation and antimicrobial assay of ceramic brackets coated with TiO2 thin films

Objective

Different methods have been utilized to prevent enamel demineralization and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO₂ on organic compounds, we hoped to synthesize a novel bracket with a TiO₂ thin film to develop a photocatalytic antimicrobial effect.

Methods

The sol-gel dip coating method was used to prepare TiO₂ thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against Lactobacillus acidophilus and Candida albicans.

Results

Films with 5 coating layers annealed at 700℃ showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO₂ thin films with 5 coating layers annealed at 700℃ exhibited the greatest antimicrobial activity under UV-A light irradiation.

Conclusions

These results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets.

Enhanced photocatalytic inactivation of bacteria on Fe-containing TiO2 nanoparticles under fluorescent light

In this paper, the photocatalytic activity of Fe-TiO2 nanoparticles (NPs) under fluorescent light was studied using Escherichia coli and Staphylococcus aureus. Fe-TiO2 NPs were synthesized using a sol-gel method and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and transmission electron microscopy. The efficiency of photocatalytic inactivation towards E. coli was studied under different physicochemical parameters. The photocatalytic inactivation rate increased with increasing Fe content in TiO2 NPs and the highest inactivation was achieved for 3.0 mol% Fe-TiO2 NPs under fluorescent light. These results demonstrate that the presence of an optimum concentration of Fe in TiO2 matrix enhances the photocatalytic inactivation of TiO2 NPs under fluorescent light.

Effects of coating with different ceromers on the impact strength, transverse strength and elastic modulus of polymethyl methacrylate

The aim of this study was to evaluate the mechanical properties of polymethyl methacrylate (PMMA) after coating with different ceromers. For transverse strength and modulus of elasticity tests, specimens of 65×10×2.5 mm dimensions were prepared (5 groups, n=10). For impact strength test, specimens of 60×7.5×4 mm dimensions were prepared (5 groups, n=10). Test group specimens were coated with one of four different types of ceromers, and specimens in the control group were not coated. After specimens were tested for transverse and impact strengths, the data were analyzed with Kruskal-Wallis and Conover post hoc tests (p<0.05). GLYMOTEOS-TiO2 and A174-TEOS significantly increased the transverse strength of PMMA. All ceromers caused a statistically significant increase in the elastic modulus of PMMA. While GLYMO-TEOS-ZrO2 significantly decreased the impact strength, the other ceromers did not cause any statistically significant difference in impact strength. Coating with ceromers substantially improved the mechanical properties of PMMA.

Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO2 under UV and visible light

Commercially available microcrystalline TiO2 was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe(2+) doped TiO2 and Fe(3+) doped TiO2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag(+) doped TiO2 was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe(3+) doped TiO2 was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir-Hinshelwood pseudo-first-order kinetic model. Kinetic measurements confirmed that, Ag(+) doped TiO2 was most efficient in the UV range, while Fe(3+) doped TiO2 was most efficient in the visible range.

Sn doping induced enhancement in the activity of ZnO nanostructures against antibiotic resistant S. aureus bacteria

Highly ionic metal oxide nanostructures are attractive, not only for their physiochemical properties but also for antibacterial activity. Zinc oxide (ZnO) nanostructures are known to have inhibitory activity against many pathogens but very little is known about doping effects on it. The antibacterial activity of undoped ZnO and tin (Sn) doped ZnO nanostructures synthesized by a simple, versatile, and wet chemical technique have been investigated against Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa bacterial strains. It has been interestingly observed that Sn doping enhanced the inhibitory activity of ZnO against S. aureus more efficiently than the other two bacterial strains. From cytotoxicity and reactive oxygen species (ROS) production studies it is found that Sn doping concentration in ZnO does not alter the cytotoxicity and ROS production very much. It has also been observed that undoped and Sn doped ZnO nanostructures are biosafe and biocompatible materials towards SH-SY5Y Cells. The observed behavior of ZnO nanostructures with Sn doping is a new way to prevent bacterial infections of S. aureus, especially on skin, when using these nanostructures in creams or lotions in addition to their sunscreen property as an ultraviolet filter. Structural investigations have confirmed the formation of a single phase wurtzite structure of ZnO. The morphology of ZnO nanostructures is found to vary from spherical to rod shaped as a function of Sn doping. The excitation absorption peak of ZnO is observed to have a blue shift, with Sn doping leading toward a significant tuning in band gap.

Progress of TiO2 Photocatalytic Oxidation Technology in Algae Removal

In this paper, the development in the degradation of microcystic toxins and algae removal by TiO2photocatalysts is reviewed, analyzing the prospect and pinpointing the key factor of the technology. TiO2, which is insoluble, nontoxic, inexpensive and catalyst-efficient, shows good chemical inertness. For the degradation of microcystic toxins and algae removal, TiO2 photocatalysts is superior to the traditional processing technology and method, contributing a lot to environmental protection.

Photo-induced self-cleaning and sterilizing activity of Sm3+ doped ZnO nanomaterials

Highly active samarium doped zinc oxide self-cleaning and biocidal surfaces (x mol% Sm(3+)/ZnO where x=0, 1, 2 and 4 mol%) with crystalline porous structures were synthesized by hydrothermal method. Sm(3+)/ZnO thin films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopic (EDS), UV-visible diffuse reflectance and fluorescence (FL) spectroscopy. The combination between doping and hydrothermal treatments significantly altered the morphology of ZnO into rod and plate-like nanoshapes structure and enhanced its absorption and emission of ultraviolet radiation. The photo-activity in term of quantitative determination of the active oxidative species (()OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results showed that, the hydrothermally treated 2.0 mol% Sm(3+)/ZnO film (S2) is the highly active one. The optical, structural, morphology and photo-activity properties of the highly active thin film (S2) make it promising surface for self-cleaning and sterilizing applications.

Understanding bactericidal performance on ambient light activated TiO2-InVO4 nanostructured films

TiO(2)-InVO(4) nanostructured films were coated onto glass substrates and systematically investigated for their bactericidal activities using Escherichia coli (E. coli) as the model bacterium under ambient light illumination. The uniform TiO(2)-InVO(4) nanostructured films were prepared using titanium isopropoxide (TTIP) as the precursor via a simple sol-gel approach. Polyethylenimine (PEI) was used as a surfactant to ensure uniform dispersion of InVO(4) and a sacrificial pore-inducing agent, generating nanostructured films. Compared to unmodified TiO(2) film, the current TiO(2)-InVO(4) films exhibited enhanced bactericidal activities under ambient light illumination. Bacterial cell "photo-fixation" was demonstrated to be crucial in enhancing the bactericidal activity. A bacterial-nanostructured surface interaction mechanism was proposed for the current ambient-light activated nanostructured film.

Vancomycin-functionalised Ag@TiO2 phototoxicity for bacteria

This study reports on the synthesis of vancomycin (Van)-functionalised Ag@TiO(2) nanoparticles and their enhanced bactericidal activities. Van-Ag@TiO(2) nanoparticles were prepared by nanoparticle deposition and chemical cross-linking reactions. The catalysts showed high efficiency for the degradation of methylene blue under ultraviolet (UV) illumination. The photocatalytic inactivation of the sulphate-reducing bacteria, Desulfotomaculum, was also studied under UV light irradiation and in the dark using aqueous mixtures of Ag, Ag@SiO(2), Ag@TiO(2), and Van-Ag@TiO(2). The Van-Ag@TiO(2) nanoparticles showed a capacity to target Van-sensitive bacteria. They also effectively prevented bacterial cell growth through the functionalised nanoparticles under UV irradiation for 1h. To investigate the specificity of the catalyst phototoxicity, a Van-resistant bacteria, Vibrio anguillarum, was used as the negative control. The results indicated that Van-Ag@TiO(2) nanoparticles had a higher selective phototoxicity for Van-sensitive bacteria. Therefore, the antibiotic molecule-functionalised core-shell nanoparticles allow for selective photokilling of pathogenic bacteria.

Photocatalytic decomposition on nano-TiO₂: destruction of chloroaromatic compounds

Photocatalysis is applied increasingly in addressing and solving environmental and energy-related problems. Especially the TiO₂-derived catalysts attract attention because of their catalytic efficiency, wide range of applications, ease in use, and low cost (it costs about 150 Yuan a kilogram in China). This review first describes the principles of photocatalytic destruction by semiconductors and then focuses on degradation rates and reaction mechanisms in a variety of photocatalytic uses of modified TiO(2). Finally, these concepts are illustrated by selected examples relating to the photocatalytic degradation of organic persistent pollutants, such as polychlorinated benzenes (PCBz), biphenyls (PCB) and dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). And some approaches towards industrial application are analyzed.

Facile design and nanostructural evaluation of silver-modified titania used as disinfectant

Fundamental research has been carried out to define optimal "green" synthesis conditions for the production of titania (TiO(2)) and silver (Ag) nanocomposites (TANCs) ranging from 12.7-22.8 nm in diameter. A bottom-up colloidal approach was employed to accurately control TANC monodispersity and composition. TANCs were found to be effective at inactivating Escherichia coli (E. coli) in water. The presence of Ag in the nanocomposites induced a decrease in TiO(2) band gap energy, which favoured valence to conduction band electron transfer and allowed for electron excitation using visible light. Aggregation of ultra-fine particles was prevented through the use of a long-chain polymer as evidenced by electrophoretic mobility studies. The TANCs catalyzed oxidation of bacterial membranes and cell death or disinfection. Theoretically, the TANC mode of E. coli disinfection is via water photolysis, which results in production of hydroxyl radicals and hydrogen peroxide. These interact with the outer membrane polysaccharides and lipids, leading to lipid peroxidation, membrane weakening and resulted in cell death. Our overarching goals were to optimize the variables involved in TANC "green" synthesis and to characterize its nanostructure. High resolution (HR) transmission and scanning electron microscopic (TEM and SEM) studies demonstrated that TANCs were highly crystalline and mono-dispersive. Elemental composition of Ag and Ti, as measured by X-ray energy dispersive (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed sample purity. Ultraviolet-visible (UV-VIS) spectroscopy showed that the energy band-gap of Ag modified TiO(2) was in the visible range.

Nanocharacterization and bactericidal performance of silver modified titania photocatalyst

An environmental-friendly procedure for manufacturing silver (Ag) and titania (TiO(2)) nanocomposites in an aqueous solution is presented. This green synthetic approach results in the successful production of nanomaterials with high dispersion and crystallinity. The colloidal suspensions of the nanocomposites composed of metal and ceramic (Ag-TiO(2)) were found to be extremely stable over a prolonged time period. Morphologically, nanocomposites were found to be composed of near-spherical particles that were highly crystalline. The nanocomposites were mono-dispersed with particles varying in size from 20 to 50nm, depending upon nanocomposite solution pH. Indexed metallic nanoscale silver exhibited a face-centered cubic (fcc) crystalline phase structure. Nanocomposite elemental composition studies indicated that the molar ratio of Ag and Ti was approximately 1-20. The binding energies and energy differences of Ag, Ti and O were well-indexed with their associated standard spectra. Nanocomposite optical absorption properties were consistent with noble metal nanoparticles. The zetapotential for the nanocomposites was higher at acidic pH and exhibited an absolute negative charge that apparently inhibited particle agglomeration. Escherichia coli (E. coli), a Gram-negative model microorganism was effectively inactivated using the nanocomposites under visible light at ambient temperature and pressure. The 'green chemistry' derived Ag-TiO(2) composites are applicable for the removal of biological impurities from drinking and underground water supplies. The results of the study indicated that nanocomposites could be specifically designed to prevent growth of bacteria in water.