Ag Decoration and SnO2 Coupling Modified Anatase/Rutile Mixed Crystal TiO2 Composite Photocatalyst for Enhancement of Photocatalytic Degradation towards Tetracycline Hydrochloride

The anatase/rutile mixed crystal TiO₂ was prepared and modified with Ag decoration and SnO₂ coupling to construct a Ag@SnO₂/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO₂ coupling on the structure and photocatalytic properties of TiO₂ were studied. Ag decoration and SnO₂ coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO₂/TiO₂ exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO₂ increased from 63.3% to 83.1% with Ag@SnO₂/TiO₂.

Antimicrobial Nanostructured Coatings: A Gas Phase Deposition and Magnetron Sputtering Perspective

Counteracting the spreading of multi-drug-resistant pathogens, taking place through surface-mediated cross-contamination, is amongst the higher priorities in public health policies. For these reason an appropriate design of antimicrobial nanostructured coatings may allow to exploit different antimicrobial mechanisms pathways, to be specifically activated by tailoring the coatings composition and morphology. Furthermore, their mechanical properties are of the utmost importance in view of the antimicrobial surface durability. Indeed, the coating properties might be tuned differently according to the specific synthesis method. The present review focuses on nanoparticle based bactericidal coatings obtained via magneton-spattering and supersonic cluster beam deposition. The bacteria–NP interaction mechanisms are first reviewed, thus making clear the requirements that a nanoparticle-based film should meet in order to serve as a bactericidal coating. Paradigmatic examples of coatings, obtained by magnetron sputtering and supersonic cluster beam deposition, are discussed. The emphasis is on widening the bactericidal spectrum so as to be effective both against gram-positive and gram-negative bacteria, while ensuring a good adhesion to a variety of substrates and mechanical durability. It is discussed how this goal may be achieved combining different elements into the coating.

Optimizing the synthesis of SnO2/TiO2/RGO nanocomposites with excellent visible light photocatalytic and antibacterial activities

Multifunctional SnO₂/TiO₂/RGO nanocomposites with enhanced photocatalytic degradation and antibacterial activity have been successfully synthesized by a facile one-pot environmentally friendly green hydrothermal route using titanium tetrabutoxide (TBOT), Na₂SnO₃ and graphene oxide (GO) without reducing agents and any structure-directing agents. The results demonstrate that the reaction pH conditions play important roles in the control of the crystallographic phases of TiO₂ and SnO₂. In addition, the visible-light-active photocatalytic and antibacterial activities of the synthesized composites were measured for the degradation of rhodamine B (RhB) and the growth inhibition of the Gram-negative bacteria Escherichia coli (E. coli), which are strongly affected by the SnO₂ loading content, the crystal structure of TiO₂ and the appropriate addition of graphene. The superior photocatalytic and antibacterial activities of the nanocomposites were attributed to their great optical adsorption capability and excellent charge separation and transfer efficiency. This study may provide new insights into the fabrication of efficient visible-light-active SnO₂/TiO₂/RGO nanocomposites and expand their applications in the environmental remediation and water disinfection fields.

Copper(ii)-based coordination polymer nanofibers as a highly effective antibacterial material with a synergistic mechanism

Nanofibers of a copper(ii)-based coordination polymer [Cu(HBTC)(H₂O)₃] were synthesized via a microwave-assisted hydrothermal process, while macroparticles and bulk crystals were prepared via a hydrothermal method. X-ray analysis revealed that this compound possesses one-dimensional zig-zag chains, in which the coordination polyhedron of the copper(ii) center is a five-coordinate distorted square-pyramid. The width of the as-prepared nanofibers was about 150 nm, while the size of the macroparticles was about 200 μm. The antibacterial activities of the nanofibers and macroparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated by determining the minimal inhibitory concentration (MIC), the growth curve of the bacteria and the bacterial reduction assay. The nanofibers showed higher antibacterial performance as compared with macroparticles, commercial copper nanoparticles, and pure ligands alone. The bacteriostatic rates of nanofibers and macroparticles were up to 99.9% and 96.7% against E. coli, while 99.1% and 96.2% against S. aureus, respectively, when the concentration was 250 μg mL^-1. The synergistic antibacterial mechanism was also proposed based on the generation of reactive oxygen species (ROS) and the release of Cu²⁺ ions.

In vitro performance of Ag-incorporated hydroxyapatite and its adhesive porous coatings deposited by electrostatic spraying

Bacterial infection of implanted materials is a significant complication that might require additional surgical operations for implant retrieval. As an antibacterial biomaterial, Ag-containing hydroxyapatite (HA) may be a solution to reduce the incidences of implant associated infections. In this study, pure, 0.2mol% and 0.3mol% Ag incorporated HA powders were synthesized via a precipitation method. Colloidal precursor dispersions prepared from these powders were used to deposit porous coatings onto titanium and stainless steel substrates via electrostatic spraying. The porous coating layers obtained with various deposition times and heat treatment conditions were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Scratch tests were conducted to assess the adhesion strength of the coating. Antibacterial activity of Ag-incorporated HA was tested towards Escherichia coli (E. coli) at various incubation times. Osteoblast adhesion on Ag-incorporated HA was evaluated to assess biocompatibility. Improvement in adhesion strength of the coating layer was observed after the heat treatment process due to mutual ionic diffusion at the interface. The Ag-incorporated HA killed all viable E. coli after 24h of incubation, whereas no antibacterial activity was detected with pure HA. In addition, in vitro cell culture tests demonstrated osteoblast adhesion similar to pure HA, which indicated good cytocompatibility. In summary, results of this study provided significant promise for the future study of Ag-incorporated HA for numerous medical applications.