Antimicrobial TiO2 nanocomposite coatings for surfaces, dental and orthopaedic implants.

Engineering of self-disinfecting surfaces to constrain the spread of SARS-CoV-2 is a challenging task for the scientific community because the human coronavirus spreads through respiratory droplets. Titania (TiO2) nanocomposite antimicrobial coatings is one of the ideal remedies to disinfect pathogens (virus, bacteria, fungi) from common surfaces under light illumination. The photocatalytic disinfection efficiency of recent TiO2 nanocomposite antimicrobial coatings for surfaces, dental and orthopaedic implants are emphasized in this review. Mostly, inorganic metals (e.g. copper (Cu), silver (Ag), manganese (Mn), etc), non-metals (e.g. fluorine (F), calcium (Ca), phosphorus (P)) and two-dimensional materials (e.g. MXenes, MOF, graphdiyne) were incorporated with TiO2 to regulate the charge transfer mechanism, surface porosity, crystallinity, and the microbial disinfection efficiency. The antimicrobial activity of TiO2 coatings was evaluated against the most crucial pathogenic microbes such as Escherichia coli, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Legionella pneumophila, Staphylococcus aureus, Streptococcus mutans, T2 bacteriophage, H1N1, HCoV-NL63, vesicular stomatitis virus, bovine coronavirus. Silane functionalizing agents and polymers were used to coat the titanium (Ti) metal implants to introduce superhydrophobic features to avoid microbial adhesion. TiO2 nanocomposite coatings in dental and orthopaedic metal implants disclosed exceptional bio-corrosion resistance, durability, biocompatibility, bone-formation capability, and long-term antimicrobial efficiency. Moreover, the commercial trend, techno-economics, challenges, and prospects of antimicrobial nanocomposite coatings are also discussed briefly.

Carbonaceous cathode materials for electro-Fenton technology: Mechanism, kinetics, recent advances, opportunities and challenges.

Electro-Fenton (EF) technique has gained significant attention in recent years owing to its high efficiency and environmental compatibility for the degradation of organic pollutants and contaminants of emerging concern (CECs). The efficiency of an EF reaction relies primarily on the formation of hydrogen peroxide (H2O2) via 2e─ oxygen reduction reaction (ORR) and the generation of hydroxyl radicals (●OH). This could be achieved through an efficient cathode material which operates over a wide pH range (pH 3-9). Herein, the current progresses on the advancements of carbonaceous cathode materials for EF reactions are comprehensively reviewed. The insights of various materials such as, activated carbon fibres (ACFs), carbon/graphite felt (CF/GF), carbon nanotubes (CNTs), graphene, carbon aerogels (CAs), ordered mesoporous carbon (OMCs), etc. are discussed inclusively. Transition metals and hetero atoms were used as dopants to enhance the efficiency of homogeneous and heterogeneous EF reactions. Iron-functionalized cathodes widened the working pH window (pH 1-9) and limited the energy consumption. The mechanism, reactor configuration, and kinetic models, are explained. Techno economic analysis of the EF reaction revealed that the anode and the raw materials contributed significantly to the overall cost. It is concluded that most reactions follow pseudo-first order kinetics and rotating cathodes provide the best H2O2 production efficiency in lab scale. The challenges, future prospects and commercialization of EF reaction for wastewater treatment are also discussed.

Face Masks and Respirators in the Fight against the COVID-19 Pandemic: A Review of Current Materials, Advances and Future Perspectives.

The outbreak of COVID-19 has spread rapidly across the globe, greatly affecting how humans as a whole interact, work and go about their daily life. One of the key pieces of personal protective equipment (PPE) that is being utilised to return to the norm is the face mask or respirator. In this review we aim to examine face masks and respirators, looking at the current materials in use and possible future innovations that will enhance their protection against SARS-CoV-2. Previous studies concluded that cotton, natural silk and chiffon could provide above 50% efficiency. In addition, it was found that cotton quilt with a highly tangled fibrous nature provides efficient filtration in the small particle size range. Novel designs by employing various filter materials such as nanofibres, silver nanoparticles, and nano-webs on the filter surfaces to induce antimicrobial properties are also discussed in detail. Modification of N95/N99 masks to provide additional filtration of air and to deactivate the pathogens using various technologies such as low- temperature plasma is reviewed. Legislative guidelines for selecting and wearing facial protection are also discussed. The feasibility of reusing these masks will be examined as well as a discussion on the modelling of mask use and the impact wearing them can have. The use of Artificial Intelligence (AI) models and its applications to minimise or prevent the spread of the virus using face masks and respirators is also addressed. It is concluded that a significant amount of research is required for the development of highly efficient, reusable, anti-viral and thermally regulated face masks and respirators.

Is kinetic polymer arrest very specific to multiwalled carbon nanotubes?

In this study we have assessed, using dielectric relaxation spectroscopy (DRS), the confinement effects of the more mobile chain in partially miscible polymeric blends of PS/PVME (polystyrene/poly(vinyl methyl ether)) in the presence of anisotropically shaped MWCNTs (multiwalled carbon nanotubes). To understand if this confinement effect is very specific to MWCNTs, the characteristic dimensions of which are often close to the radius of gyration of the polymeric chains, a few other particles like spherical silver, stacked clay tactoids and platy graphene sheets at similar weight fractions were also incorporated and systematically studied. The DRS studies reveal that the more mobile chain (here PVME) experiences possibly two different environments in the presence of frozen PS and more importantly in the presence of MWCNTs at temperatures close to and not so far from the blend Tg. The presence of bimodal relaxations with a weak temperature independent faster relaxation in the blends is composition dependent (PS rich blends). Assuming that there are no chemical interactions of PVME with the particles, these confinement effects seem to be very specific to MWCNTs as the bimodal relaxations were completely absent in the case of other nanoparticles. In the case of polymer blends, when two different chains are brought together, a loss in the deformational entropy is expected due to the excluded volume interaction and chain connectivity effects. In the presence of nanoparticles, especially MWCNTs, the polymer coils are subjected to perturbation leading to entropic loss in the system, which determine the miscibility in the blends. The configurational entropy near glass transition was assessed to understand the improved miscibility due to MWCNTs in this particular blend. The length of cooperativity suggests a cooperative motion of PS and PVME over shorter length scales in the case of MWCNTs as compared to other particles. This also hints at perturbed PVME motion in the network of MWCNTs. Taken together, our study reveals that the kinetic PVME arrest results in two different environments and is dependent on the effective concentration of MWCNTs in the blends.