One-pot thermal and photochemical syntheses of lignin-doped silver and gold nanoparticles were developed and their antimicrobial properties were studied against Escherichia coli and Staphylococcus aureus. The nature of the lignin as well as the metal are directly involved in the antimicrobial activity observed in these nanocomposites. Whereas one of the nanocomposites is innocuous under dark conditions and shows photoinduced activity only against Staphylococcus aureus, the rest of the lignin-coated silver nanoparticles studied show antimicrobial activity under dark and light conditions for both bacteria strains. Additionally, only photoinduced activity is observed for lignin-coated gold nanoparticles. Importantly, the particles are non-cytotoxic towards human cells at the bactericidal concentrations. Preliminary assays show these silver nanoparticles as potential antimicrobial agents towards S. aureus biofilm eradication.

We report a rapid aqueous method for synthesizing monodisperse gold nanoparticles (AuNPs), employing 2-propynylamine as both an intrinsic reducing agent and a surface-stabilizing ligand. This self-mediated process—achieved in a single step—yields spherical AuNPs with an average diameter of 4.0 ± 1.0 nm and a well-defined localized surface plasmon resonance band centered at 520 nm. Acting as a bifunctional molecule, 2-propynylamine simultaneously reduces HAuCl₄·3H₂O to elemental gold and passivates the nanoparticle surface through coordination via the amine group, while preserving a terminal alkyne (–C≡CH) functionality. This reactive moiety remains exposed and chemically accessible, enabling post-synthetic modification through Cu(I)-catalyzed azide–alkyne cycloaddition. Control experiments using alternate milling times and vial composition confirmed the essential role of 2-propynylamine in mediating both reduction and surface functionalization. The resulting alkyne-functionalized AuNPs serve as versatile “click-ready” platforms for bioconjugation, sensing, and advanced material assembly. Overall, this scalable, green approach eliminates the need for external reducing or capping agents and provides a modular route to chemically addressable nanomaterials with tunable surface reactivity.

The molecular identities of nanoparticle surface coronas remain underexplored despite their influence on interfacial function. Biogenic gold nanoparticles (AuNPs) provide a tunable platform for linking phytochemical corona composition to colloidal, antioxidant, catalytic, and biological behavior. Leaf extracts from four medicinal plants simultaneously reduced and capped AuNPs, producing four spectroscopically distinct corona signatures: polyphenol-rich, terpenoid/sterol-dominated, protein–polysaccharide, and betaine-rich. FTIR and ¹H NMR indicated functional-group differences and combined with TEM-calibrated geometric models, generated surface-normalized phenolic and flavonoid indices. Across systems, putative corona composition was associated with differences in colloidal stability, radical scavenging, and normalized p-nitrophenol reduction activity. Protein–polysaccharide coronas were compatible with hydrogen-atom transfer and low acute cytotoxicity, whereas betaine-rich coronas were consistent with electron transfer but narrower stability windows. Gas-phase density functional theory of model constituents supplied intrinsic thermodynamic reference values supporting these assignments. Phytochemical profiling may therefore offer a design strategy for sustainable, bio-inspired nanointerfaces for future engineered nanomaterials applications.

We develop a surfactant-free synthesis method for gold nanoparticles (AuNPs) using 2 propynylamine-functionalized silicon nanoparticles as integrated redox-active supports. Surface-anchored amine groups act as built-in reducing sites for Au³⁺ precursors...