Visible-Light-Enhanced Antibacterial Activity of Silver and Copper Co-Doped Titania Formed on Titanium via Chemical and Thermal Treatments

Dental implants made of titanium (Ti) are used in dentistry, but peri-implantitis is a serious associated problem. Antibacterial and osteoconductive Ti dental implants may decrease the risk of peri-implantitis. In this study, titania (TiO₂) co-doped with silver (Ag) at 2.5 at.% and copper (Cu) at 4.9 at.% was formed on Ti substrates via chemical and thermal treatments. The Ag and Cu co-doped TiO₂ formed apatite in a simulated body fluid, which suggests osteoconductivity. It also showed antibacterial activity against Escherichia coli, which was enhanced by visible-light irradiation. This enhancement might be caused by the synergistic effect of the release of Ag and Cu and the generation of •OH from the sample. Dental implants with such a Ag and Cu co-doped TiO₂ formed on their surface may reduce the risk of peri-implantitis.

Recent Advances in Plasmonic Photocatalysis Based on TiO2 and Noble Metal Nanoparticles for Energy Conversion, Environmental Remediation, and Organic Synthesis

Plasmonic photocatalysis has emerged as a prominent and growing field. It enables the efficient use of sunlight as an abundant and renewable energy source to drive a myriad of chemical reactions. For instance, plasmonic photocatalysis in materials comprising TiO₂ and plasmonic nanoparticles (NPs) enables effective charge carrier separation and the tuning of optical response to longer wavelength regions (visible and near infrared). In fact, TiO₂ -based materials and plasmonic effects are at the forefront of heterogeneous photocatalysis, having applications in energy conversion, production of liquid fuels, wastewater treatment, nitrogen fixation, and organic synthesis. This review aims to comprehensively summarize the fundamentals and to provide the guidelines for future work in the field of TiO₂ -based plasmonic photocatalysis comprising the above-mentioned applications. The concepts and state-of-the-art description of important parameters including the formation of Schottky junctions, hot electron generation and transfer, near field electromagnetic enhancement, plasmon resonance energy transfer, scattering, and photothermal heating effects have been covered in this review. Synthetic approaches and the effect of various physicochemical parameters in plasmon-mediated TiO₂ -based materials on performances are discussed. It is envisioned that this review may inspire and provide insights into the rational development of the next generation of TiO₂ -based plasmonic photocatalysts with target performances and enhanced selectivities.

Synthesis of catalyst composed of palygorskita-TiO2 and silver nanoparticles for the development of assays antioxidant based on the generation of reactive oxygen species

The great interest in compounds that present antioxidant capacity has generating the urgent need for analytical methods that could determine the antioxidant potential of these sources. A method based on generation of reactive oxygen species in water from catalyst composed of palygorskita-TiO₂ and silver nanoparticles (AgNPs/TiO₂-PAL) was developed and applied to antioxidant assays. Silver nanoparticles were synthesized using silver nitrate solution, sodium borohydride reducing agent and Caraia gum as stabilizing agent. Incorporation of AgNPs into the previously synthesized TiO₂-PAL was performed. The catalyst AgNPs/TiO₂-PAL was characterized by UV-vis spectroscopy, X-ray diffractometry and scanning electron microscopy. The catalyst AgNPs/TiO₂-PAL were used to perform an antioxidant activity method which consisted in monitoring the discoloration of acid yellow 73 dye (AY73) in the presence of gallic acid antioxidant comparing to the dye discoloration in the absence of the antioxidant. A microplate reader was used to measure the discoloration of the aqueous solutions of AY73, irradiated by UV light for 60 min. The effect of reactive oxygen species generated by AgNPs/TiO₂-PAL based in photocatalytic kinetics of AY73 dye was investigated. The oxidation of AY73 dye by photocatalysis in the system with AgNPs/TiO₂-PAL catalysts was carried out mainly by the participation of O₂ ^·-, HO^· and ¹O₂ species, in this order of importance. The results showed that the synthesis of the AgNPs/TiO₂-PAL catalyst was successfully carried out and the application of this material in the development of an innovative methodology for the determination of antioxidant activity was extremely promising.

Enhancement of Rhodamine B Degradation by Ag Nanoclusters-Loaded g-C₃N₄ Nanosheets

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C₃N₄ nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C₃N₄. The sharp decrease of photoluminescence intensity indicates that g-C₃N₄/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⁺ in the starting solution. The g-C₃N₄/Ag heterojunctions prepared from 0.01 M of Ag⁺ starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C₃N₄ nanosheets.

Enhanced photocatalytic and antibacterial activity of plasma-reduced silver nanoparticles

A non-thermal atmospheric pressure plasma jet has been used for the green synthesis of highly dispersed colloidal silver nanoparticles. The reducing species such as hydrogen radicals and hydrated electrons are identified, and the change in the solution pH is studied during AgNP formation. The structural properties and size of the plasma-reduced silver nanoparticles are characterized via X-ray diffraction, ultraviolet-visible spectroscopy, fluorescence spectroscopy and transmission electron microscopy. The size of the colloidal AgNPs is tuned by adjusting the initial concentration of AgNO₃. The effect of terephthalic acid, a hydroxyl radical scavenger, on the reduction of Ag⁺ ion is studied. The typical catalytic activity data indicate the better performance of the plasma-reduced colloidal Ag nanoparticles than that obtained from the chemical reduction method. The antibacterial activity of the plasma-reduced Ag nanoparticles also shows a better performance than that of the chemically reduced AgNPs, highlighting the potential of the plasma reduction approach for the synthesis of metal nanoparticles, which are stable even after 30 days without a stabilizing agent. Additionally, the effects of hydroxyl scavengers (isopropyl alcohol) and Fenton's reagent (Fe²⁺ salt) on CV degradation are studied.

A non-thermal atmospheric pressure plasma jet has been used for the green synthesis of highly dispersed colloidal silver nanoparticles.

Photocatalytic decomposition behavior and reaction pathways of organic compounds using Cu nanoparticles synthesized via a green route

Green, facile and environmentally friendly biosynthetic methodology for the fabrication of Cu nanoparticles using an aqueous extract ofAnas platyrhynchosegg shells.

Fabrication of pristine Mn2O3and Ag–Mn2O3composite thin films by AACVD for photoelectrochemical water splitting

Pristine Mn₂O₃and Ag–Mn₂O₃nanocomposite thin films deposited by AACVD on FTO showed photocurrent densities of 1.8 and 3 mA cm⁻²respectively.