Highly selective and sensitive detection of carcinogenic benzene using a raisin bread-structured film comprising catalytic Pd-Co₃O₄ and gas-sensing SnO₂ hollow spheres

The facile and affordable fabrication of sensors that can detect carcinogenic benzene has remained a long-standing challenge, as sophisticated nano-architectures and/or sensing films are essential to ensure benzene selectivity. Herein, we report a raisin bread-structured film fabricated by mixing two different types of oxide hollow spheres, as a novel, cost-effective platform for the highly selective and sensitive detection of benzene. The film comprises catalytic Pd-Co₃O₄ (i.e., raisins) and gas-sensing SnO₂ hollow spheres (i.e., bread), prepared by ultrasonic spray pyrolysis. In contrast to films of pure SnO₂ or Pd-Co₃O₄ hollow spheres, which are partially selective to reactive gases such as xylene/toluene/ethanol, raisin bread films are highly selective to less reactive benzene. Thus, an array of the SnO₂, Pd-Co₃O₄, and raisin bread sensors enables exclusive benzene identification with principal component analysis. The superior benzene-sensing properties of raisin bread sensors are attributed to the oxidative consumption of reactive gases by the catalytic raisins, whereas less-consumed benzene sensitively reacts with the gas-sensing bread. This is supported by proton transfer reaction-quadrupole mass spectrometry analysis. This work provides a simple, rational strategy to attain gas selectivity to chemically stable benzene and is expected to trigger the development of ubiquitous portable devices to monitor airborne benzene.