Rapid and Scalable Synthesis of Zeolitic Imidazole Framework (ZIF-8) and its Use for the Detection of Trace Levels of Nitroaromatic Explosives

A facile and inexpensive approach for scalable synthesis of highly porous zeolite imidazolate framework nanoparticles (ZIF-8) is described. The synthesis, done in an aqueous solution at room temperature, takes just 2 min compared to hours or days in nonaqueous conditions. The structural integrity and phase purity of ZIF-8 are studied through X-ray powder diffraction and are of sodalite topology, and its surface nature and composition are determined with X-ray photoelectron spectroscopy. ZIF-8 has high crystallinity, large Brunauer-Emmett-Teller surface area (1398.7 m(2) g(-1)) and pore volume (0.62 cm(3) g(-1)). Images of ZIF-8 show hexagonal nanocrystals, whose growth is observed with atomic force microscopy (AFM). Thermogravimetric analysis data testify the thermal stability of the material (490 degrees C in air). Zeta potential measurement confirms that trinitrotoluene (TNT) molecules adsorb onto ZIF-8. The interaction between the electron-deficient aromatic core of TNT and the electron-rich ZIF-8 is considered to favor the formation of donor-acceptor electron-transfer mechanism, and the electron conductivity of ZIF-8 facilitates the effective reduction of TNT. Using the prepared ZIF-8, an electrochemical sensor is fabricated to detect TNT and other nitroaromatic explosives in aqueous phase. The sensor performance is highly linear, with very low limit of detection (346 x 10(-12)m), and is unaffected by the presence of various interferents.