VOC gas sensor based on hollow cubic assembled nanocrystal Zn₂SnO₄ for breath analysis

Hollow cubic assembled nanocrystal Zn₂SnO₄ was synthesized via one-step hydrothermal method for VOC gas sensing applications. The obtained Zn₂SnO₄ materials had a uniformly hollow cubic structure with an average size of approximately 1 μm and a wall thickness of about 150 nm formed from nanocrystals of around 14 nm. The X-ray absorption near-edge structure results showed no structural disorder and/or lattice damage around the Zn-absorbing atoms and the Zn oxidation state of 2+ in the host lattice of the hollow cubic Zn₂SnO₄. The gas sensing characteristics of the prepared Zn₂SnO₄ material were tested to C₃H₆O, C₂H₅OH, CH₃OH, NH₃, H₂, and CO at 350 °C–450 °C and results showed that the sensors exhibited a good response to acetone and ethanol gases. The highest response values were 47.80 for 125 ppm of acetone and 7.52 for 10 ppm of ethanol at 450 °C. The Zn₂SnO₄ hollow cubic sensor demonstrated high sensitivity and selectivity to acetone with good stability and a detection limit of 175 ppb. The VOC sensing mechanism of the hollow cubic Zn₂SnO₄-based sensor was also discussed. The findings indicated that hollow cubic Zn₂SnO₄ is a promising material for use in excellent VOC gas sensing application towards breath analysis.