Effect of CTAB on the surface resonance plasmon intensity of silver nanoparticles: Stability and oxidative dissolution

PEGylation of silver nanoparticles by physisorption of cyclic poly(ethylene glycol) for enhanced dispersion stability, antimicrobial activity, and cytotoxicity

Silver nanoparticles (AgNPs) are practically valuable in biological applications. However, no steady PEGylation has been established, which is essential for internal use in humans or animals. In this study, cyclic PEG (c-PEG) without any chemical inhomogeneity is physisorbed onto AgNPs to successfully PEGylate and drastically enhance the dispersion stability against physiological conditions, white light, and high temperature. In contrast, linear HO-PEG-OH and MeO-PEG-OMe do not confer stability to AgNPs, and HS-PEG-OMe, which is often used for gold nanoparticles, sulfidates the surface to considerably degrade the properties. TEM shows an essentially intact nanostructure of c-PEG-physisorbed AgNPs even after heating at 95 °C, while complete disturbance is observed for other AgNPs. Molecular weight- and concentration-dependent stabilization by c-PEG is investigated, and DLS and ζ-potential measurements prove the formation of a c-PEG layer on the surface of AgNPs. Furthermore, c-PEG-physisorbed AgNPs exhibit persistent antimicrobial activity and cytotoxicity.

Biobased composites from agro-industrial wastes and by-products

The greater awareness of non-renewable natural resources preservation needs has led to the development of more ecological high-performance polymeric materials with new functionalities. In this regard, biobased composites are considered interesting options, especially those obtained from agro-industrial wastes and by-products. These are low-cost raw materials derived from renewable sources, which are mostly biodegradable and would otherwise typically be discarded. In this review, recent and innovative academic studies on composites obtained from biopolymers, natural fillers and active agents, as well as green-synthesized nanoparticles are presented. An in-depth discussion of biobased composites structures, properties, manufacture, and life-cycle assessment (LCA) is provided along with a wide up-to-date overview of the most recent works in the field with appropriate references. Potential uses of biobased composites from agri-food residues such as active and intelligent food packaging, agricultural inputs, tissue engineering, among others are described, considering that the specific characteristics of these materials should match the proposed application.

Photo-oxidative Decolorization of Brilliant Blue with AgNPs as an Activator in the Presence of K2S2O8 and NaBH4

The decolorization of brilliant blue (E133) in aqueous solution by K2S2O8 and NaBH4 with AgNPs as an activator was studied spectrophotometrically under normal laboratory conditions. Batch experiments were performed to investigate the effects of reaction time, initial dye concentration, activator concentration, solution pH, and temperature on the decolorization of E133. K2S2O8 and NaBH4 did not decolorize the dye E133 in the absence of AgNPs. The optimum dosage of AgNPs was 0.01 g/L, and 98% dye E133 degradation was observed with 3.75 mM K2S2O8 at 30 °C in ca. 60 min of reaction time. In the NaBH4/AgNPs system, only 60% dye degradation was observed for an identical reaction condition. The decolorization rate constant increases with the increase in concentrations of AgNPs, K2S2O8, NaBH4, and reaction temperature. The decolorization degree of the E133 responded linearly with K2S2O8 and NaBH4 concentrations. The existence of sulfate radicals (SO4 · -) and hydroxyl radicals (HO·) generated during the decolorization of E133 was identified by using ethanol and tertiary butyl alcohol as scavengers. Based on the E133 solution absorbance changes at 628 nm, the decolorization mechanism was proposed and discussed.

Nanocomposite starch-based films containing silver nanoparticles synthesized with lemon juice as reducing and stabilizing agent

Silver nanoparticles (AgNP L) synthesis using the active compounds of lemon juice was optimized. The obtained nanoparticles were included in starch-based film formulations, studying the relevant properties that condition their application in the packaging area. The optimized conditions for AgNP L' synthesis were 30 min at 90 °C, which led to the lowest nanoparticle size (5.5 nm) with the highest associated stability (ζ= -29.5 mV) up to 90 days. Nanocomposite films resulted with an orange tone that increased with AgNP L concentration (14.3-143 ppm). Water vapor permeability decreased while tensile mechanical resistance increased up to an aggregate of 71.5 ppm of AgNP L, indicating the nanoparticles' reinforcement of the polymer matrix. Besides, the citric acid content provided by lemon juice also affected the starch-based relevant film properties. Regarding antimicrobial capacity, a synergic effect between active compounds of lemon juice and silver nanoparticles was evidenced, being Salmonella spp. the most sensitive bacteria.