Schematic representation of the effect on ML/AOT/water and IPM/AOT/water at different pH values.

Background/Objectives: In the race to develop new antibiotics to combat multidrug-resistant bacteria, particularly the ESKAPE pathogens which pose a significant threat to public health, silver nanoclusters (AgNCs) have emerged as a promising alternative. This article focuses on the potential of novel silver nanoclusters as an antimicrobial agent against Staphylococcus aureus, a high-priority pathogen known for its ability to cause persistent nosocomial infections and develop protective biofilms. Methods: In this study, we successfully synthesized AgNCs at pH 7 using an eco-friendly photoreduction method with poly acrylic acid (PAA) and poly methacrylic acid (PMAA) as stabilizers. This methodology produced fluorescent AgNCs, demonstrating their stability in aqueous solutions for at least three months and highlighting the effectiveness of PAA and PMAA as stabilizing agents. The AgNCs were incubated with S. aureus suspension, and the antimicrobial capability at different concentrations and times of incubation were determined. Also, the AgNCs hemocompatibility was studied by exposing the clusters to rat blood cells. Results: The in vitro assays revealed that AgNCs capping with PAA or PMAA has antimicrobial activity in low doses (the determination of minimum inhibitory concentration (MIC): 0.2 µg/mL, and the determination of minimum bactericidal concentration (MBC): 2 µg/mL) and without cytotoxicity (hemolysis less than 10%) to rat blood cells until 1 µg/mL. In the presence of both AgNCs (5 µg/mL), bacterial growth was completely inhibited within just 3 h. Conclusions: The findings of this study highlight the potential of silver nanoclusters as effective antimicrobial agents against S. aureus. Their stability, low toxicity, and rapid bactericidal activity make them promising candidates for further development in antimicrobial applications.

The present work describes the synthesis of new nanomaterials based on gold nanoclusters (AuNCs) supported on poly(N-isopropylacrylamide) (PNIPAM) and polyacrylamide (PAAM) hydrogels, as well as their characterization in terms of structure and physicochemical properties. AuNCs were synthesized by incorporating the metallic precursor (Au³⁺) into the polymeric matrices and subsequently reducing it with UV-vis light (λ = 365 nm). The materials were characterized by UV-vis, FT-IR, fluorescence spectroscopy, TEM and SEM. Likewise, the thermal properties and the swelling capacity of the different polymer matrices were determined. In addition, we present a comparative study with two nanomaterials regarding their behavior for the selective detection of Hg²⁺ in water. Furthermore, it is demonstrated that the polymer matrices influence the nanomaterials' selectivity to mercury. As the AuNCs fluorescence incorporated in both matrices is quenched by Hg²⁺, the materials can be used to sense sensitively and selectively Hg²⁺ in water with a detection limit of 4.1 nM and 1.3 nM for Au-PNIPAM and Au-PAAM NCs, respectively. Summarizing, our study presents a novel, easy and straightforward route to synthesized nanomaterials with unique optical and chemical properties, which could be used for the construction of a portable Hg²⁺ detection device.

Polypyrrole (PPy) nanofilms were deposited by in situ chemical oxidative polymerization on polyethylene or polypropylene. The thickness is determined by SEM of the cross-section. Thin thickness nanofilms (180 ± 5 nm) are deposited. The nanofilms are then modified by nucleophilic addition to attach functional groups to the nanofilms. Strong nucleophiles (e.g., thiols) react by conventional heating. Weak nucleophiles (e.g., nitroanilines) only react when applying microwaves. The spectroscopic (UV–visible, FTIR, XPS and XANES) characterization shows the attachment of functional groups and the change in electronic properties upon the reaction. The conductivity of the functionalized PPy nanofilms are lower than unmodified PPy nanofilms, likely due to steric effects on the extended conjugation and disturbance of the electron hopping between chains. While reaction with some nucleophiles (e.g., bisulfite ion) makes nanofilms more hydrophilic, modification with long alkyl chains or fluorinated long chains produces highly hydrophobic nanofilms. No noticeable effect of the reaction on the film thickness is observed, suggesting little or no loss of polymer due to dissolution.