GNPs-QDs core-satellites assembly: trimodal platform for on-site identification and detection of TNT in complex media

Accurate, sensitive, and selective on-site screening of explosives are of crucial importance in antiterrorism and homeland security. Here, we proposed a first tri-mode method capable of on-site discrimination and detection of trinitrotoluene (TNT) by utilizing the colorimetric, fluorescence and surface-enhanced Raman scattering (SERS) response of Au nanoparticles (GNPs)@quantum dots (GNPs-QDs) core-satellite assemblies. The cysteamine-modified GNPs and mercaptopropionic acid-capped CdTe QDs directly assemble each other due to electrostatic interaction, leading to significant photoluminescence quenching because of a high-effective (>95%) energy transfer from QDs to GNPs. However, the addition of TNT into GNPs-QDs assemblies induces formation of Meisenheimer complex (cysteamine-TNT complex) and destroys core-satellite structures, causing increment in colorimetric and fluorescent signals of hybrid system, which facilitates visualization of TNT by the naked-eyes. Importantly, the superior affinity of TNT toward cysteamine triggers self-aggregation of GNPs and enhancement of Raman signals of TNT, allowing for distinguishing of TNT from its analogues. The GNPs-QDs based trimodal strategy exhibits good linearity between 10 fM and 200 mu M with a detection limit of 3.2 fM. Moreover, the proposed sensing system validates a reliable quantitative analysis of TNT from environmental specimens including soil, clothing, fruit, and liquor in a portable and rapid feature. The excellent performance makes the sensing platform ideal for point-of-care applications in forensic arena and homeland defense.