Photoluminescent MoS2 and MoSe2 Quantum Dots for the Detection of Nitro-Organic Explosives

Transition metal dichalcogenide quantum dots (QDs, e.g., MoX2, X = S, Se) have drawn tremendous research attention due to their intriguing optoelectronic properties with many potential applications. In the present work, we have synthesized MoX2 (X = S, Se) QDs through hustle-free hydrothermal techniques, followed by their purification and detailed characterization using various spectroscopic and imaging techniques. Both QDs showed strong blue emission at similar to 450 nm through excitation at similar to 375 nm with average excited-state lifetime values of 3.97 and 7.75 ns, respectively, for MoS2 and MoSe2 QDs. Excitation wavelength-dependent photoemission was observed for both of them with tunable emission wavelengths of 410 to 470 nm for MoS2 and 420 to 480 nm for MoSe2, and this may arise due to the polydispersity of the synthesized samples. Their comparative solution-phase sensing performance for various nitro-organic explosive molecules was evaluated; while all nitroaromatic compounds trinitrophenol (TNP), trinitrotoluene (TNT), dinitrotoluene (DNT), and nitrotoluene (NT) resulted in fluorescence quenching, the nonaromatic explosives royal demolition explosive (RDX), pentaerythritol tetranitrate (PETN) caused fluorescence enhancement. The fluorescence lifetime measurements of MoX2 QDs showed almost no change with gradual addition of these explosives, implying a static interaction mechanism.