Porphyrin Functionalized Graphene Based Nanosensors for Electrochemical Analysis of 1,3-Dinitrobenzene and Picric Acid

Abstract

In recent years, terrorism has become a serious threat to public security throughout the world. Due to heightened level of public security due to increased terrorist attacks, highly sensitive, portable and miniaturized devices for explosives are of upmost importance. Nitroaromatic compounds are widely used for military munitions especially as major component of explosive materials. A number of approaches have been adopted to detect nitroaromatic compounds. These approaches include electrochemical method, reverse-phase HPLC, chemiluminescence, spectrophotometry, surface enhanced Raman scattering and immunosensing. One method that offers a possible route for the development of sensing system is the use of functionalized graphene based sensor. In this research, graphene oxide and reduced graphene oxide and pristine graphene is synthesized by Hummers‘ method, chemical reduction and liquid phase exfoliation of graphite while tetraphenylporpyrin (TPP) is prepared by Adler-Longo‘s method and copper tetraphenylporphyrin (Cu-TPP) by simple metallation. The graphene based nanomaterials are functionalized with tetraphenylporphyrin and copper tetraphenylporphyrin PGr/TPP, PGr/Cu- TPP, rGO/TPP, rGO/Cu-TPP hybrids are prepared to detect 1,3- dinitrobenzene (1,3-DNB) and picric acid (PA) analytes. The GO, rGO, pristine graphene, DNB, TPP and CuTPP were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), IR and UV-Vis spectroscopy. After functionalization, reduced graphene oxide based sensor shows high sensitivity, reproducibility and selectivity for nitroaromatic compounds. Cyclic voltammetery and electrochemical impedance spectroscopic techniques are used for the analysis of electrochemical behavior of structures. rGO-Cu-TPP is found to exhibits the higher current response, least charge transfer resistance and sensitivity of 1.50μA/μMcm2.towards 1,3-DNB and rGO-TPP exhibits sensitivity of 1.007μA/μMcm2 towards picric acid. The improved sensitivity of sensor can be attributed to the best adsorptive properties and rich electronic system of tetraphenylporphyrin structure, large electronically active surface area and rapid charge transfer of reduced graphene oxide.