Highly porous chitosan beads embedded with silver-graphene oxide nanocomposites for antibacterial application

Incorporation of silver nanomaterial into polymer matrix can further accomplished their potential usage in real life applications. In our previous study, silver nanoparticles (AgNPs) and silver-graphene oxide nanocomposites (AgGO) were prepared via a rapid microwave-assisted method. Hereby, the as-synthesized AgNPs or AgGO was dispersed in a chitosan solution. Subsequently, the resultant mixture solution was further coagulated in a coagulation bath containing sodium hydroxide via a neutralization process. This resulted in the formation of spherical-shaped chitosan beads. The structure of the beads showed that the chitosan beads embedded with AgGO exhibited a more porous structure as compared to the plain chitosan beads. Furthermore, the chitosan beads containing AgNPs or AgGO were tested for their antibacterial activity against Escherichia coli and Staphylococcus aureus. The antibacterial results indicated that the silver nanomaterial contained chitosan beads could effectively inhibit the growth of both E. coli and S. aureus as compared to the bare chitosan beads. The produced chitosan nanocomposite envisioned that can be potentially employed for water disinfection purpose

Silver nanowires as flexible transparent electrode: role of PVP chain length

In this project, crystalline silver nanowires (AgNWs) are successfully grown using a continuous segmented flow process. The robust relationship among the structural, electrical and optical properties of the AgNWs in the function of the polyvinylpyrrolidone (PVP) chain length is elaborated. A concise carrier transport and a density mechanism are also discussed using a localized conductive atomic force microscopy analysis. The obtained results proved that the AgNWs synthesized using PVP with a chain length of 1.3 M exhibit excellent electrical and optical properties in the form of flexible transparent film with a sheet resistance of 90% at various bending angles. These findings present an alternative approach for production of AgNWs and fabrication of a high flexible transparent electrode

Mechanical and antibacterial properties of paper coated with chitosan

Recent developments have found the viability of chitosan as a new alternative additive in the pulp and paper technology. This study was carried out to investigate the effect of chitosan as a paper coating which were prepared by dissolution in acetic acid solution. The mechanical properties of coated paper were improved significantly compared with non-coated paper. The FT-IR spectra showed peak evolution at 1558 cm-1 for coated paper due to the existence of amine group. Since FT-IR spectra for the coated paper was almost identical to the chitosan spectrum, it is assumed that there is an obvious physical interaction rather than the chemical interaction. The SEM micrographs showed that some of the chitosan has occupied the pores and some of them adhered only on the surface. This may be due to the chemical similarities between cellulose and chitosan which enhanced the strength of fiber matrixes via hydrogen bonding. The antibacterial property of coated paper showed that chitosan in dried form has no significant effect but effective when applied as wet solution

Conversion of glucose into lactic acid using silica-supported zinc oxide as solid acid catalyst

Zinc oxide (ZnO) has been proven to be highly effective in converting biomass into fine chemicals. It possesses several limitations, such as leaching in hydrothermal reactions and difficulty with regard to its recovery. Supporting ZnO on silica improves its recovery, stability and recyclability. In this study, we produced silica-supported ZnO by incipient wetness impregnation (IWI) method for the conversion of glucose into lactic acid. The presence of the ZnO provided active sites for isomerization to occur. The highest yield of lactic acid was 39.2 % at 180 °C for 60 min. Prolonged reaction time and higher reaction temperature promoted further degradation of lactic acid into acetic acid. The yield of lactic acid decreased after the first cycle and decreased slightly for the nine consecutive cycles

Effective photoreduction of graphene oxide for photodegradation of volatile organic compounds

Nowadays, humans spend most of their time indoors and are frequently exposed to volatile organic compounds (VOCs) from various sources. The photocatalytic oxidation (PCO) method is a relatively more efficient method than the adsorption method for removing VOCs from the environment. In this work, graphene oxide (GO) was partially reduced via photoreduction under ultraviolet light (UV-A) irradiation and then used as a photocatalyst to degrade VOCs. After photoreduction, the band gap of the partially reduced graphene oxide (PRGO) decreased from 3.5-4.5 eV to 3.1-4.0 eV. Methanol vapour, which acts as a model VOC, was photodegraded using the PRGO. The effectiveness of the PRGO was mainly due to the removal of oxygen functional groups and restoration of the sp2 domain. This lowered the band gap and slowed down the electron recombination rate, which resulted in a higher photocatalytic activity. The photocatalytic activity of PRGO followed pseudo-first order kinetics, with a rate constant of 0.0025 min-1, and it could be reused for five cycles without any significant loss in the photocatalytic activity. This study demonstrates the potential of PRGO as a versatile and stable metal-free photocatalyst to remove indoor pollutants. © The Royal Society of Chemistry

Catalytic Conversion of Empty Fruit Bunch (EFB) Fibres into Lactic Acid by Lead (II) ions

Lactic acid (LA) is a potential platform chemical that can be produced from lignocellulosic biomass. The development of a cost-competitive, catalytic-based LA production system is gaining significant attention in modern biorefineries. A series of experimental study was carried out to investigate the chemocatalytic effect of the conversion of oil palm empty fruit bunch (EFB) fibers into lactic acid under hydrothermal conditions. Synthesis of chemicals from lignocellulosic biomass involves complex mechanisms because of the complex composition of the biomass. Therefore, experimental parameters, i.e., temperature, Pb(II) concentration, and reaction time were studied. It was found that production of LA is highly dependent on the experimental conditions. In this study, the highest LA yield obtained from EFB fibers was > 46% (230 °C, 2 mM Pb(II) after 4 h of reaction). However, a similar yield can be achieved either using higher Pb(II) and shorter reactions time or vice versa. The selective production of chemical compounds (glucose, 5-hydroxymethyl furfural (5-HMF), furfural, levulinic acid, and lactic acid) from EFB fibers is highly dependent on the availability of Pb(II) ions