Dual-Mode Solution Plasma Processing for the Production of Chitosan/Ag Composites with the Antibacterial Effect

The development of novel biocompatible and biodegradable materials for medical applications has been drawing significant interest in the scientific community for years. Particularly, chitosan loaded with silver nanoparticles (Ag NPs) has a strong antimicrobial potential and could be applied, for example, as wound dressing material. In this work, chitosan/Ag NP composites were produced utilizing a single-step plasma-solution process, which is simple and environmentally friendly. An acetic solution of chitosan containing AgNO3 was treated by the direct current (DC) atmospheric pressure glow discharge, with the liquid serving as either cathode or anode. The plasma-solution system with liquid anode is more useful for the production of Ag NPs. Nevertheless, the NP size is comparable for both cases. The plasma treatment with both polarities led to chitosan degradation. The cleavage of glucosidic chains mostly occurred in the system with the liquid cathode, whereas the side oxidation reactions took place when the solution served as the anode. The oxidation processes were possibly induced by the hydrogen peroxide H2O2 efficiently formed in the last case. The composite materials produced with both polarities of liquid electrode demonstrated the bactericidal action against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and Gram-positive Bacillus subtilis.

Bactericidal Silver Nanoparticles by Atmospheric Pressure Solution Plasma Processing

Silver nanoparticles have applications in plasmonics, medicine, catalysis and electronics. We report a simple, cost-effective, facile and reproducible technique to synthesise silver nanoparticles via plasma-induced non-equilibrium liquid chemistry with the absence of a chemical reducing agent. Silver nanoparticles with tuneable sizes from 5.4 to 17.8 nm are synthesised and characterised using Transmission Electron Microscopy (TEM) and other analytic techniques. A mechanism for silver nanoparticle formation is also proposed. The antibacterial activity of the silver nanoparticles was investigated with gram-positive and gram-negative bacteria. The inhibition of both bacteria types was observed. This is a promising alternative method for the instant synthesis of silver nanoparticles, instead of the conventional chemical reduction route, for numerous applications.

SOLUTION PLASMA PROCESSING OF NATURAL POLYMER-BASED MATERIALS

Non-equilibrium low-temperature atmospheric pressure plasma is a highly reactive medium that allows for the ecofriendly modification of nature-derived materials. This work reviews the field of liquid phase plasma modification of polymer-based materials derived from natural sources. Types of solution plasma systems are considered with respect to the efficiency of the generation of active species, their transport to and interaction with macromolecules. Tunable modification of plants (birch, willow, bamboo and vine shoots; barley, rice and rapeseed straw; perennial grasses), algae, plant-derived by-products and wastes (sawdust, bast fibers, nutshells, seeds, peels, press-cake and pomace), plant-derived polymers (cellulose, hemicellulose, lignin, starch, sodium alginate) and animal-derived polymer-based materials (chitosan, collagen, gelatin) by solution plasma treatment is compared to conventional wet chemistry methods. Synthesis of nano-biocomposites with advanced functionalities is also considered. <span style="opacity: 0;"> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </span><span style="opacity: 0;"> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </span>

Synthesis of heteroatom-carbon nanosheets by solution plasma processing using N-methyl-2-pyrrolidone as precursor

Heteroatom-carbon nanosheets, composed of multi-layer graphene with turbostratic stacking, were successfully synthesized through a solution plasma processing (SPP) with N-methyl-2-pyrrolidone at room temperature and an atmospheric pressure.

Cellulose Conversion to Sugar Alcohol by Solution Plasma Processing

ABSTRACTCellulose was selectively converted to sugar alcohols (sorbitol and mannitol) over a supported-metal catalyst ruthenium on carbon (Ru/C) by the application of plasma in cellulose aqueous suspension. Generally, conversion of cellulose to sugar alcohol should be done under H2 pressure and high temperature. The goal of using solution plasma process (SPP) in this study is to initiate “self-hydrogenation” by reactive hydrogen species generated from the plasma due to dissociation of water medium. The sugar alcohols were produced at room temperature and atmospheric pressure. Electrospray ionization mass spectrometric analysis indicates that the SPP is a potent tool to promote the conversion of cellulose to sugar alcohols.