High selectivity in water soluble MoS₂ quantum dots for sensing nitro explosives

Rapid and selective detection of nitro explosives is one of the most promising issues concerning global security. Intensive research has already been carried out, however, the selectivity is still lacking. In the present work, water soluble MoS₂ quantum dots (QDs) are synthesized through a bottom-up approach using (NH₄)₆Mo₇O₂₄·4H₂O and Na₂S as molybdenum and sulfur sources, respectively, and 1,4-diaminobutane as the capping agent. The as-synthesized QDs detect 2,4,6-trinitrophenol (TNP) selectively up to 2.04 ppm and the selectivity reaches >90% which is remarkably higher than the earlier results. In addition to predominant electron transfer (ET) that occurs mostly in fluorescence quenching processes, Forster resonance energy transfer (FRET) also occurs here. As a result of the occurrence of both these ET and FRET processes, high selectivity is achieved for the present samples. The unique advantage of using QDs is the tuning of photoluminescence as a function of dot size to become comparable with the absorption spectra of the TNP to perform the FRET mechanism.