Quantum dots for detection of trace amount of nonvolatile explosives: the effect of TNT in the fluorescence of CdSe quantum dots

We report on the effect of trinitrotoluene (TNT) in the fluroescence emission of CdSe quantum dots covered with a ZnS core shell. Pulses of 100 femtoseconds are employed to excite the fluorescence of the dots off resonance. We found evidence for a strong quenching by TNT on the fluorescence emission of the quantum dots. The fluorescence emission of the QD experiences a blue or red shift that depends on the CdSe particle size and amount of TNT. The results are explained in terms of a charge transfer mechanism or a modification of the traps involved in electron relaxation in QD. The results show that QD are a promising tool for TNT sensing.