Carboxymethyl cellulose gels immobilized Ag/AgCl-ZnO nanoparticles for improving sunlight-catalyzed antibacterial performance

Superabsorbent ZnO/rubber-based hydrogel composite for removal and photocatalytic degradation of methylene blue

A superabsorbent hydrogel was prepared by the free-radical copolymerization of natural rubber (NR) latex with poly(acrylic acid) (PAA) at NR loadings up to 50 wt%. An NR/PAA hydrogel containing 40 wt% of NR (NR-40) had a water absorption capacity of 214 g/g (21,400 %) of its dry weight. The compressive modulus increased 512 % and sample integrity was improved due to the physical entanglement of NR chains. NR-40 hydrogel removed 97 % of methylene blue (MB) from the aqueous solution in 1 h (at initial concentrations of 10-1000 mg/L) and produced a maximum removal of 1191 mg MB/g of hydrogel at an initial MB concentration of 4500 mg/L. The adsorption of MB was an endothermic process. Fourier transform infrared spectroscopy indicated that hydrogen bonding and electrostatic interaction drove the process. After the in-situ incorporation of ZnO into NR-40, absorbed energy from sunlight generated active species that could photocatalytically degrade adsorbed MB in the hydrogel matrix. The scavenger tests indicated that superoxide radical anions and hydroxyl radicals were the main species for this process. The hydrogel composite material showed good stability and could be regenerated and reused over 10 cycles, degrading >80 % of the adsorbed dye. This novel natural-based hydrogel provides double functions of adsorption and photodegradation of toxic dyes without the requirement of chemicals and a separation process.

Exploiting the advantages of cationic copolymers and AgBr nanoparticles to optimize the antibacterial activity of chitosan

Recently, the chitosan (CS)-based composites have attracted increasing attention for controlling and preventing the spread of pathogenic microorganisms. Herein, an amphiphilic copolymer containing epoxy and quaternary ammonium groups (PBGDBr) was synthesized via three common acrylate monomers. The epoxy groups of this copolymer were then crosslinked with the amino groups of CS to synthesize a natural/synthetic (PBGDBr-C) composite to increase the water solubility of CS under alkaline conditions and enhance its antibacterial activity based on chemical contact-type modes. Moreover, silver bromide nanoparticles (AgBr NPs)-decorated PBGDBr-C (AgBr@PBGDBr-C) composite was prepared, which aimed to endow the final AgBr@PBGDBr-C composite with a photodynamic antibacterial mode relying on the formation of Ag/AgBr nanostructures catalyzed by visible light on AgBr NPs. The results showed that the final composite possessed satisfactory bactericidal effects at concentrations higher than 64 and 128 μg/mL against Escherichia coli and Staphylococcus aureus, respectively. Additionally, The L929 cells treated with the final composite retained high cell viability (>80 %) at a concentration of 128 μg/mL, indicating its low toxicity to L929 cells. Overall, our synthetic strategy exploits a multi-modal system that enables chemical-photodynamic synergies to treat infections caused by pathogenic bacteria while delaying the development of bacterial resistance.

Chitosan synergizes with bismuth-based metal-organic frameworks to construct double S-type heterojunctions for enhancing photocatalytic antimicrobial activity

In recent years, photocatalytic technology has been introduced to develop a new kind antimicrobial agents fighting antibiotic abusing and related drug resistance. The efforts have focused on non-precious metal photocatalysts along with green additives. In the present work, a novel bis-S heterojunctions based on the coupling of polysaccharide (CS) and bismuth-based MOF (CAU-17) s synthesized through a two-step method involving amidation reaction under mild conditions. The as prepared photocatalyst literally extended the light response to the near-infrared region. Owing to its double S-type heterostructure, the lifetime of the photocarriers is significantly prolonged and the redox capacity are enhanced. As a result, the as prepared photocatalyst indicated inhibition up to 99.9 % under 20 min of light exposure against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria as well as drug-resistant bacteria (MRSA). The outstanding photocatalytic performance is attributed to the effective charge separation and migration due to the unique double S heterostructure. Such a double S heterostructure was confirmed through transient photocurrent response, electrochemical impedance spectroscopy tests and electron spin resonance measurements. The present work provides a basis for the simple synthesis of high-performance heterojunction photocatalytic inhibitors, which extends the application of CAU-17 in environmental disinfection and wastewater purification.

Water resistant, biodegradable and flexible corn starch/carboxymethyl cellulose composite film for slow-release fertilizer coating materials

The inherent limitations of Cornstarch (CS) and Carboxymethyl Cellulose (CMC) membranes, such as brittleness, fragility, and water solubility, limit their use in controlled-release fertilizers. This study reports on the synthesis of crosslinked CMC/CS-20-E composite membranes using the casting technique, with epichlorohydrin (ECH) as the crosslinking agent in an acidic environment to crosslink CS and CMC. The synthesized composite film demonstrates remarkable water resistance, as evidenced by the insignificant alteration in its morphology and structure post 72 h of water immersion. Its flexibility is reflected in its capacity to endure knotting and bending, with an elongation at break reaching 78.1 %. Moreover, the degradation rate surpasses 90 % within a span of seven days. The CMC/CS-20-E-x-urea controlled-release fertilizer was subsequently produced using a layer-by-layer self-assembly technique, where urea particles were incorporated into the crosslinked composite solution. This CMC/CS-20-E-x-urea controlled-release fertilizer displayed superior controlled-release performance over a duration of seven days when juxtaposed with pure urea. In particular, the CMC/CS-20-E-3 %-urea controlled-release fertilizer showed a cumulative release rate of 84 % by the seventh day. The controlled-release fertilizers developed in this study offer a promising strategy for creating eco-friendly options that are crucial for fertilizing crops with short growth cycles.