Humic Polyelectrolytes Facilitate Rapid Microwave Synthesis of Silver Nanoparticles Suitable for Wound-Healing Applications

This article describes the one-pot microwave synthesis of silver nanoparticles (AgNPs) assisted with natural polyelectrolytes-humic substances (HS). The humic polyelectrolytes served both as chemical reductants for silver ions and as end-capping agents for AgNPs. Three commercially available sodium humates extracted from lignites and leonardite and one sodium fulvate isolated from natural brown water seeped through peat deposits were used in this study. The dynamics of the growth rate of AgNPs was characterised by UV-VIS spectroscopy by measuring the intensity of surface plasmon resonance at 420 nm. Transmission electron microscopy was used to characterise the size and morphology of AgNPs. Dynamic light scattering was used to determine size distributions of the synthesised AgNPs in the solutions. It was established that both conventional and microwave syntheses assisted with the coal humates produced small-size AgNPs in the range from 4 to 14 nm, with the maximum share of particles with sizes of (6 ± 2) nm by TEM estimates. The peat fulvate yielded much larger NPs with sizes from 10 to 50 nm by TEM estimates. DLS measurements revealed multimodal distributions of AgNPs stabilised with HS, which included both single NPs with the sizes from 5 to 15 nm, as well as their dominating aggregates with sizes from 20 to 200 nm and a smaller portion of extra-large aggregates up to 1000 nm. The given aggregates were loosely bound by humic polyelectrolyte, which prevented the coalescence of AgNPs into larger particles, as can be seen in the TEM images. The significant acceleration in the reaction time-a factor of 60 to 70-was achieved with the use of MW irradiation: from 240 min down to 210-240 s. The coal humate stabilised AgNPs showed antimicrobial properties in relation to S. aureus. A conclusion was made regarding the substantial advantages of microwave synthesis in the context of time and scaling up for the large-scale production of AgNP-HS preparations with antimicrobial properties suitable for external wound-healing applications.

Multifunctional Architectures of Cyclic Dipeptide Copolymers and Composites, and Modulation of Multifaceted Amyloid-β Toxicity

Alzheimer's disease (AD) is a major neurodegenerative disorder primarily characterized by the β-amyloid (Aβ42) misfolding and aggregation-associated multifaceted amyloid toxicity encompassing oxidative stress, neuronal death, and severe cognitive impairment. Modulation of Aβ42 aggregation via various structurally anisotropic macromolecular systems is considered effective in protecting neuronal cells. In this regard, we have developed a cyclic dipeptide (CDP)-based copolymer (CP) and explored its material and biomedical properties. Owing to the structural versatility, CDP-CP forms solvent-dependent anisotropic architectures ranging from dense fibers and mesosheets to vesicles, which are shown to interact with dyes and nanoparticles and mimic synthetic protocells, providing a conceptually new approach to achieve advanced functional materials with the hierarchical organization. CP upon interaction with gold nanoparticles (GNP) and polyoxometalate (POM) generated faceted architectures (CP-GNP) and the nanocomposite (CP-POM), respectively. CP-GNP and CP-POM have shown remarkable ability to inhibit Aβ42 aggregation, dissolve the preformed aggregates, and scavenge reactive oxygen species (ROS) to ameliorate multifaceted amyloid toxicity. In cellulo studies show that CP-GNP and CP-POM protect neuronal cells from Aβ42-induced toxicity and reduce lipopolysaccharide (LPS)-activated neuroinflammation at sub-micromolar concentration. To our knowledge, this is the first report on the hierarchical organization of CDP-CP into 1D-to-2D architectures and their organic-inorganic hybrid nanocomposites to combat the multifaceted amyloid toxicity.

New Dual-Functional and Reusable Bimetallic Y2ZnO4 Nanocatalyst for Organic Transformation under Microwave/Green Conditions

A novel bimetallic and reusable Y₂ZnO₄ nanocatalyst was synthesized by a simple coprecipitation method. The prepared nanocatalyst exhibited dual catalytic activity and was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The average crystallite and grain sizes were found to be 17 ± 1 and 10 ± 2 nm, respectively. On the one hand, the catalytic activity of the nanocatalyst was studied for the Knoevenagel condensation reaction of aromatic aldehydes with active methylene compounds, such as ethyl cyanoacetate and malononitrile, under microwave irradiation and solvent-free conditions. On the other hand, the nanoparticles also showed faster photocatalytic activity against methyl orange (MO) compared to other dyes. The nanocatalyst was easily recoverable by a simple filtration method and was recycled without any significant loss of catalytic activity. The advantages of this nanocatalyst were a simple workup procedure, high reaction yields, solvent-free conditions, reusability, and a short reaction time under green reaction conditions.

Clay-supported anisotropic Au-modified N,S-doped TiO2 nanoparticles for enhanced photocatalytic dye degradation and esterification reactions

Kaolinite clay supported doped TiO₂ and anisotropic gold deposited visible light induced plasmonic nanocatalysts for dye degradation and esterification reactions.

Enhanced catalytic and SERS performance of shape/size controlled anisotropic gold nanostructures

Au nanostars of different sizes and shapes prepared using a simple method and their applications.