Detection of gunshot residue and explosives using hybrid graphene/quantum dot based sensors

Sammanfattning: This master thesis investigates the use of chemically exfoliated graphene, CdSe/CdS/ZnS quantum dots and graphene quantum dots for fluorescence based detection of gunshot residue and explosives. Specifically, nitroglycerine is chosen as the target substance in gunshot residue and the nitroaromatic compounds trinitrotoluene and dinitrotoluene are chosen as target explosives. The experimental work is divided into three part were the first one is an investigation of the quenching of semiconductor quantum dot fluorescence by graphene. The results show that graphene is an efficient quencher, and it is probable that quenching takes place without the fluorescing and quenching agents being in contacts, through either Förster resonance energy transfer or nanometal surface energy transfer. The second part is a study of how nitroaromatic molecules quench the fluorescence from graphene quantum dots. The results indicate that the solvent of the nitroaromatics passivates the functional groups which reduces the quenching efficiency. Nevertheless, it is concluded that the nitroaromatics quench the fluorescence. It is possible that the quenching mechanism is photoinduced charge transfer. The last part of the experimental work investigates the influence of nitroaromatics on the graphene and semiconductor quantum dot hybrid from the first part. It is shown that nitroaromatics further quench the fluorescence of the quantum dots in the hybrid structure, possibly by photoinduced charge transfer or by reacting with the surface coating of the quantum dots and thereby introducing de-excitation through surface states.