Search

Condensation product of salicylaldehyde and 1,3 propylenediamine becomes a diiminic Schiff base, which is oxidized by AgNO3 in alkaline solution, and in turn, stable Ag(0) is produced at room temperature. Under this condition, the solution exhibits intense silver nanoparticle enhanced fluorescence (SEF) with the λ(em) at 412 nm. Dopamine is selectively detected down to the nanomolar level via exclusive fluorescence quenching of the SEF. Dopamine-infested solution regains the fluorescence [i.e., SEF in the presence of Hg(II) ions]. Thus dopamine and Hg(II) in succession demonstrate "turn off/on" fluorescence due to the change in the scattering cross section of Ag(0) and gives a quantitative measure of dopamine in real samples. The proposed method is free from interferences of common biocompetitors.

Fluorescent carbon dots (NSCDs) with a size of ∼5 nm (λex = 320 nm and λem = 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 (λex = 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. [ABSTRACT FROM AUTHOR]