Silver nanoparticle anchored carbon dots for improved sensing, catalytic and intriguing antimicrobial activity

Abstract

Fluorescent carbon dots (NSCDs) with a size of ∼5 nm (λ_ex = 320 nm and λ_em = 386 nm) have been synthesized under reflux from an alkaline mixture of dopamine and cysteine. The synthesized NSCDs are hybridized with in situ generated silver nanoparticles (AgNPs) obtained by mixing AgNO₃ at room temperature. NSCDs enrich the plasmonic bands of AgNPs due to the localized surface plasmon resonance (LSPR) effect. Further enrichment of plasmon band, depending on the acetone concentration, enables acetone sensing down to 8 × 10⁻⁵ M admixed in 1 M water. Thus, acetone induced hybrid particles with a sharp plasmon band (λ_ex = 410 nm) become a sulfide sensing platform. Furthermore, vacuum dried stable particles (with or without acetone) have been proven to be an excellent catalyst for selective reduction of cationic dyes and they exhibit intriguing antimicrobial activity. These two types of dry particle act differently, which enables us to distinguish their altered surface functionalization in terms of catalysis and bacterial growth.