Next generation TNT sensor systems: Hollow silica gel structures with encapsulated pyrene

Bomb-attacks are considered as one of the most-used terrorist act in the world and domestic. The main ingredients of the explosives that are used in these terrorist-acts are trinitrotoluene (TNT), dinitrotoluene (DNT) and nitro-aromatic compounds. Therefore, their rapid-detection of these compounds is very important to prevent the terrorist acts. In this context, florescence based quenching system emerges as a rapid, repetable and pratic method. Pyrene and its derivatives are frequently used in these systems owing to their florescence properties and high quantum yields, although pyrene based florescence sensors exhibit high performance in polar organic solvents, they can not be used in water based analysis. The limited solubility of polyaromatic hydroccarbon based pyrene and its derivatives in water and aqueous medium prevents their usage in water-based analysis. In this study, a novel sensor system was developed through encapsulation of 1-pyrenemethanol in hydrophilic hollow silica gels through pore-size reduction. The hollow mesoporous SiO2 structure was obtained by coating the magnetic γ-Fe2O3 as the hard-template and then the core was removed by acid treatment. SiO2 based synthesized materials were characterized by means of FTIR, N2 adsorption/desorption analysis, X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM). The photophysical properties of 1-pyrenemethanol based compounds were carried out using Visible-ultraviolet and Florescence spectroscopy. Explosive detection studies based on florescence queching analysis were carried out using TNT and DNT compounds. The sensor system found to be very sensitive to TNT and showed a limit of detection (LOD) value of 7.03 x 10-8 M. The florescence quenching experiments that were carried out in the presence of various nitroaromatic compounds confirmed the selectivity of the sensor towards TNT.