Theoretical Investigations Of Explosives-Detection-Mechanism Based On Fluorescence Quenching

Along with the increasing use of nitro-explosives and explosive-like, the associated terrorist attacks have caused countless casualties and serious economic losses, leaving many innocent people into panic and poverty. Therefore, accurate detection of explosives exhibits great importance. Commonly used detection methods include police dog detection, modern sophisticated analytical instruments and other imaging techniques.The promising optical detection with the advantages of high-speed, cost effective, and portability has attracted increasing attention in recent years.Thanks to its unique constructional features and optical properties, luminescent metal-organic frameworks (LMOFs) crystalline materials were reported to detect explosives in 2009, More and more researches have being reported later on. However, a clear understanding of this guest-molecule-based luminescent mechanism is lacked. Thus, a clear understanding of the detecting mechanism of LMOFs should be the precondition and transplantable rules are needed to govern the selection of those building blocks. Herein, This paper investigates the luminescent properties of luminescent metal-organic framework (LMOF) [Zn2(oba)2(bpy)], and its selectivity for the detection of nitro-explosives via fluorescence quenching, using the density functional and time-dependent density functional theories. The luminescent mechanism of the LMOF follows the electron transfer from ligand to ZnO quantum dot. The hydrogen bondings formed between LMOF and electron-withdrawing nitro-explosives as well as electron-donating aromatic compounds have different influences on the luminescent mechanism of the LMOF. The hydrogen bonding in the excited state was investigated to display the relationship between hydrogen bonding and fluorescence.It presents an idea for analyzing the mechanism of the explosives detection by LMOFs and provides a theoretical guidance for designing LMOF for detecting explosives.The quasi-zero dimensional nano-material graphene quantum dots (GQDs), has excellent electronical and optical properties and can be used as a carbon material due to its low toxicity, good biocompatibility, which has immeasurable prospects and advantages in the application of optical sensors to detect explosives. Wang et al in 2012 had reported that GQDs can be utilized sensitively and selectively for the detection of trinitrotoluene (TNT) and two possible detection mechanism was.given. We mainly used the DFT and TDDFT methods to analyse the detection mechanism deeply. Frontier orbitals and electron configuration reveals the luminescence mechanism of GQDs before and after combined with TNT. And analysis of the geometric configuration and charge analysis shows that the luminescence quenching phenomenon is because of the formation of hydrogen bonds and ?-? interactions between the two which produce the electron transfer process. All of the above work provides theoretical guidance for more efficient and accurate synthesis of fluorescence sensors selectively and sensitively for the detection of explosives.