Reduced graphene oxide-mediated electron-hole separation using titanium dioxide increases the photocatalytic antibacterial activity of bone scaffolds

Photocatalytic activity and biodegradation of polyhydroxybutyrate films containing titanium dioxide

Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity

Nanocomposite polyacrylonitrile filaments containing titanium dioxide and silver nanoparticles were produced by wet-spinning method with the aim of developing multifunctional filaments showing antibacterial activity, photocatalytic activity, and electrical conductivity. The nanocomposite filaments were characterized regarding their morphology, composition, nanoparticle dispersion, tensile properties, crystallinity, conductivity, thermal properties, photocatalytic, and antibacterial activity. The nanoparticles were observed to be well dispersed. The composite filaments with 3 wt% silver nitrate showed improved crystallinity. The highest breaking tenacity of 8.72 cN/tex was observed for the filament with 1 wt% TiO2 and 3 wt% AgNO3. The conductivity of the nanocomposite filaments were on the order of 10−4 S/cm, which is in the semiconductive range. The nanocomposite filaments displayed both antibacterial and photocatalytic activity. This study showed the possibility of producing multifunctional filaments with the simultaneous addition of different types of nanoparticles into the filament structure.

Novel magnetic CoFe2O4/Ag/Ag3VO4 composites: Highly efficient visible light photocatalytic and antibacterial activity

Constructing MnO2/single crystalline ZnO nanorod hybrids with enhanced photocatalytic and antibacterial activity

Antibacterial photocatalytic activity of different crystalline TiO2 phases in oral multispecies biofilm

Effect of various capping agents on photocatalytic, antibacterial and antibiofilm activities of ZnO nanoparticles

This study aims to improve the photocatalytic activity of zinc oxide thin films by simultaneously doping with a higher oxidation state transition element and another element with localized plasmon resonance. To achieve this hypothesis, tungsten (W) and copper (Cu) were added to ZnO and the effects of W + Cu co-doping on the photocatalytic activity have been investigated. In addition, the influence of W + Cu co-doping on the structural, optical and surface morphological properties of ZnO has been studied and the obtained results have been correlated with the enhancement in the photocatalytic activity. The concentration of W was kept as 3 wt% and that of Cu was varied as 1, 3 and 5 wt%. The films were deposited on stainless steel mesh substrates. Antibacterial activity test was carried out for all the prepared film samples. The co-doped film with W + Cu doping concentrations 3 + 3 wt% exhibits superior photocatalytic and antibacterial activities when compared with other samples. The reasons and the mechanism behind this enhancement in the photocatalytic and antibacterial activities have been addressed in this paper.

We report the efficient biogenic synthesis of silver nanoparticles (Ag NPs) using silver nitrate and extracts of different parts of Theobroma cacao: the husk (h-Ag NPs), pulp (p-Ag NPs), and seed (s-Ag NPs). In addition, we have tested the antibacterial and photocatalytic activities of the Ag-NPs. The Ag NPs obtained from husk, pulp, and seed extracts show variation in the particle size, dispersion, and morphology. UV–visible absorbance measurements reveal surface plasmon resonance bands at 425, 438, and 462 nm for the s-Ag, h-Ag, and p-Ag NPs, respectively. Transmission electron microscopy studies revealed the formation of monodisperse spherical Ag NPs with diameter ranging from 6 to 18 nm. Fourier transform infrared measurements of the as-synthesized Ag NPs indicate differences in the phytochemicals decorating the NP surfaces, which led to differences in the zeta potential, hydrodynamic radius, and polydispersity index. The p-Ag, h-Ag, and s-Ag NPs exhibited photocatalytic activity on exposure to sunlight from sun, achieving 35%, 29%, and 24% degradation of methylene blue (MB) within 60 min, respectively. Further, the p-Ag NPs showed 98.3% MB photodegradation after 180 min. The photocatalytic rate constants for the degradation of MB were also calculated. Finally, we found that the biogenic nanoparticles affect bacterial growth, possibly by causing protein leakage and cell death. The p-Ag NPs showed better antibacterial activity against Bacillus subtilis and Escherichia coli than h-Ag and s-Ag. The photocatalytic and antibacterial activities of the Ag NPs synthesized with T. cacao mainly depend on the particle size and the biomolecules on the surface of the NPs.

Enhanced photocatalytic and antibacterial activity of ZnO with rice field crab chitosan and plectranthus amboinicus extract

Mechanistic investigation of visible light driven novel La2CuO4/CeO2/rGO ternary hybrid nanocomposites for enhanced photocatalytic performance and antibacterial activity

Heterogeneous photocatalysis over TiO2 using the sunlight seems to be a promising technology for waste-water treatment and drinking water production. However, the overall efficiency of TiO2 under natural sunlight is limited to the UV-driven activity (λ < 400 nm), accounting only to 4% of the incoming solar energy on the Earth's surface. The increase of the TiO2 absorption towards wavelengths more abundant on the planet's surface has, thus become recently an interesting challenge. In this framework, the main objective of this work was to study the modification of TiO2 by non metallic doping (N and S) in order to increase its light absorption in the visible region (45% of the light hitting the terrestrial surface). Commercial TiO2 powders were doped by a simple preparation method consisting of manual grinding them with a N or S precursor (thiourea) and then annealing at 400 and 500 °C. At both temperatures N, S co-doped commercial TiO2 powders with visible response were obtained. However, the annealing step produced a reduction on the specific surface area and dehydroxylation causing a detrimental effect on the photocatalytic UV-driven activity principally on photocatalyst annealed at 500 °C. E. coli bacteria inactivation, phenol and di-chloroacetate (DCA) oxidation was achieved when the co-doped photocatalyst annealed at 400 °C was illuminated upon UV light the •OH radical being the main oxidative species, that was detected by Electronic Spin Resonance (ESR) spin-trapping with DMPO. In contrast, upon visible light irradiation, N, S co-doped TiO2 powders showed a diminished oxidation power since phenol and DCA were not oxidized. On the other hand, it was possible to inactivate E. coli cells demonstrating that under these conditions, the photocatalytic mechanism was different. In order to elucidate this mechanism, characterization by Diffuse Reflectance Time Resolved Spectroscopy (DRTRS), Low Temperature-ESR and ESR-spin trapping measurements were done. By DRTRS measurement, it was found that under visible light excitation, electrons would be promoted from N, S localized states within the band gap to the conduction band. These electrons were probably trapped on shallow traps such as oxygen vacancies (Vo) allowing them to reach lifetimes of ms. LT-ESR data revealed that N, S co-doping probably could benefit the formation of Vo. ESR spin trapping with TMP-OH as a singlet oxygen quencher, revealed the formation of singlet oxygen as the main oxidative species instead of the •OH radical. Thus, it was suggested that a photo-promoted electron, instead of the localized hole on N, S states, would be the carrier charge playing the main role in photocatalytic reactions on N, S co-doped commercial TiO2 powders. When the electron is trapped on Vo, it could react with molecular oxygen previously adsorbed producing superoxide radical (•O2-). Finally, the oxidation of •O2- by localized holes seems to be thermodynamically favored leading the singlet oxygen (1O2) production. It is well known that singlet oxygen is a Reactive Oxygen Species with a lower oxidative power than the hydroxyl radical. Singlet oxygen is not able to oxidize organic substances such as phenol and DCA but this species is very toxic to microorganism producing lipid peroxidation reaction on biological membranes. It was also concluded that N, S co-doped TKP 102 annealed at 400 °C did not present an enhancement on their photocatalytic activity towards phenol oxidation and E. coli inactivation when simulated solar light was used. Undoped Degussa P-25 was the commercial powder with highest photocatalytic activity. Evidences are reported about the classical photocatalytic process where •OH radicals are produced mainly by oxidation of water or hydroxyl ions with photo-induced valence band holes prevails upon simulated solar light exposition. Localized states induced by N or S-doping and responsible of visible light absorption did not play an important role on the photocatalytic activity of these novel materials under the experimental conditions used.

A new type of poly(methyl methacrylate) (PMMA)/TiO2 nanocomposite film sensitized by ionic liquids with a low dosage of TiO2 nanoparticles was prepared based on a microemulsion method. The photocatalytic activity, via the photoreduction of 4-nitrophenole (4-NP) to 4-aminophenole (4-AP) by NaBH4, and the photocatalytic-based antibacterial activity, for the destruction of Escherichia coli and Staphylococcus aureus, of the prepared nanocomposite film were investigated. The conditions for the maximum efficiency in the presence of visible light irradiation have been evaluated. The rate constant of the photoreduction of 4-NP to 4-AP was calculated and the maximum rate constant was found with the 0.01 wt% of TiO2 dosage in the photocatalyst and a solution pH of 7.5. The photocatalytic antibacterial maximum activity against Gram-negative bacteria was also obtained for the 0.01 wt% of TiO2 concentration of the photocatalyst. A notable result of this work is that PMMA/TiO2 nanocomposite films show efficient photocatalytic activity at very low loadings of TiO2, in contrast to other previous reports.

The green synthesis of transition metal oxide nanocomposites using plant extracts is a new and effective method that avoids the involvement of hazardous chemicals. Nondegradable organic pollutants and antibiotic drug resistance have become serious public health issues worldwide. Hence, the main objective of this study is to synthesize Co3O4-ZnO nanocomposites using Calpurnia aurea leaf extract and evaluate its photocatalytic and antibacterial activities. The green synthesized particles were characterized using UV-vis spectra, Fourier transform infrared spectroscopy, X-ray diffraction techniques, and scanning electron microscopy combined with energy-dispersive X-ray studies. The synthesized particles were found to be crystalline in nature with average crystallite sizes of 23.82, 14.79, 15.99, 16.46, and 21.73 nm. Scanning electron microscopy shows the spherical morphology of Co3O4-ZnO NCs, and energy-dispersive X-ray analysis confirms the formation of highly pure ZnO NPs and Co3O4-ZnO NCs. The photocatalytic activity was performed under natural sunlight using malachite green as an organic dye pollutant. The green synthesized ZnO NPs, Co3O4 NPs, 1:4, 1:3, and 1:2 Co3O4-ZnO NCs showed high degradation efficiency after 60 min of irradiation. The synthetic material showed good potential against Staphylococcus aureus and Escherichia coli, with the highest growth inhibition recorded by 1:2 Co3O4-ZnO NCs. The kinetics study of the photocatalytic degradation was confirmed as pseudo first order, and the possible mechanisms for both photocatalytic and antibacterial activities were clearly determined.

Semiconductor nanostructures with photocatalytic activity have the potential for many applications including remediation of environmental pollutants and use in antibacterial products. An effective way for promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor. In this paper, we demonstrated the successful deposition of Au NPs, having sizes smaller than 3 nm, onto ZnO NPs. ZnO/Au hybrid nanostructures having different molar ratios of Au to ZnO were synthesized. It was found that Au nanocomponents even at a very low Au/ZnO molar ratio of 0.2% can greatly enhance the photocatalytic and antibacterial activity of ZnO. Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au NPs on the generation of reactive oxygen species and photoinduced charge carriers. Deposition of Au NPs onto ZnO resulted in a dramatic increase in light-induced generation of hydroxyl radical, superoxide and singlet oxygen, and production of holes and electrons. The enhancing effect of Au was dependent on the molar ratio of Au present in the ZnO/Au nanostructures. Consistent with these results from ESR measurements, ZnO/Au nanostructures also exhibited enhanced photocatalytic and antibacterial activity. These results unveiled the enhanced mechanism of Au on ZnO and these materials have great potential for use in water purification and antibacterial products.