Laser-Patterned Porous Carbon/ZnO Nanostructure Composites for Selective Room-Temperature Sensing of Volatile Organic Compounds

Abstract

The development of mobile, noninvasive, and portable sensor technologies for diagnostics and emission control is highly demanded. For that purpose, laser carbonization is studied as a tool to produce responsive carbon materials from inexpensive organic precursors for the room-temperature selective detection of volatile organic compounds (VOCs) applicable in future sensor array-based devices. To increase the response of intrinsically low-responsive laser-patterned carbons (LP-C) to analytes in the gas phase, we tested carbonization in the presence of nanoscale ZnO precursors in primary inks. Following the addition of a zinc salt, Zn(NO3)2, a noticeable 43-fold increase in the sensor response (ΔR/R0 = -21.5% toward 2.5% acetone) was achieved. This effect is explained by a significant increase in the measurable surface area up to ∼700 m2·g-1 due to the carbothermic reduction supported by the in situ formation of ZnO nanoparticles. Varying Zn concentrations or the addition of as-prepared ZnO nanorods lead to different surface properties like the surface area, porosity, and polarity of LP-C. A predominant effect of the surface polarity on the selectivity toward different analytes of the sensors during physisorption, e.g., acetone vs toluene, was identified and tested. The best-performing LP-C sensors were finely characterized by transmission/scanning electron microscopies and X-ray photoelectron/energy-dispersive X-ray/Raman spectroscopies.