MPA-capped CdSe QD/mercaptoethylamine-capped AuNP nanocomposite-based sensor for instant detection of trinitrotoluene

CdSe quantum dots capped with mercaptopropionic acid (CdSe@MPA QDs) were synthesized by chemical route method. The developed CdSe@MPA QDs were pH optimized for higher emission. Gold nanoparticles in aqueous dispersion medium were synthesized by using sodium citrate as reduction agent and capped with mercaptoethylamine (MEA). Further, AuNP-MEA nanoparticles were conjugated with CdSe@MPAQDs. The “as-synthesized” nanomaterials and their composites were characterized by different analytical techniques like TEM, DLS, FTIR, UV-Vis, and PL spectroscopy. Upon excitation at λex = 400 nm, CdSe@MPA QDs show emission at 540 nm (λem) leading in a good spectral overlap with absorption spectra of AuNPs (λmax = 521 nm). Trinitrotoluene (TNT), being an electron deficient species can easily bind with electron-rich amine group. The amine functionalized GNPs (AuNP@MEA) were used as quenchers for FRET between QDs and GNPs to detect TNT. Using this assay, TNT has been selectively detected up to 21.9 nmol L−1 (LOD). Schematic diagram showing TNT detection based on FRET between gold nanoparticles and quantum dots is also suggested