Fabrication, Characterization and Application of ZnO Nanostructure-Based Micro-Preconcentrator for TNT Sensing

Preconcentrator integration with sensors for enhanced detection of target analytes, such as volatiles, explosives, and toxic compounds, has been gaining attention. Although metal oxides (MOX) have been widely used as gas sensors, they have not been employed for analyte preconcentration. In this paper, we have explored ZnO as a plausible trinitrotoluene (TNT) preconcentator material. A detailed study of these nanorods with respect to adsorption-desorption characteristics of TNT using specialized chromatographic techniques, such as gas chromatography-mass spectrometry (GC-MS) and high resolution liquid chromatography and mass spectrometry (HR-LCMS), was performed. A standard low temperature hydrothermal method was employed for the growth of ZnO nanorods. X-ray diffraction and scanning electron microscopy characterization confirmed the wurtzite crystal structure and uniform growth of these nanorods with diameter less than 100 nm and length between 4–5
$\mu \text{m}$
. An HR-LCMS analysis confirmed adsorption of TNT on ZnO nanorods at ambient conditions as a result of its high trapping capability. Our GC-MS analysis confirmed that desorption of TNT from the surface of ZnO nanorods starts beyond 70 °C. A low power micro-hotplate with ZnO nanorods patterned and grown on top of it and having an in-built resistance temperature detector was fabricated. The fabricated micropreconcentrator was integrated with a highly sensitive polymeric piezoresistive microcantilever and a 2x (two times) improvement in its response was demonstrated. [2016-0071]