Quasi-1D MnO2 nanocomposites as gas sensors for hazardous chemicals

Quasi-1D MnO2 nanocomposite materials (A/MnO2 with A = CuO, SnO2) were developed by a two-step plasma-assisted process, involving the plasma enhanced-chemical vapor deposition (PE-CVD) of MnO2 nanomaterials and their functionalization with copper or tin oxides by radio frequency (RF)-sputtering. A thorough characterization by means of specific surface analytical techniques highlighted the formation of high purity nanocomposites, endowed with a controlled morphology and a tailored spatial dispersion of the functionalizing agents. The target materials were tested as gas sensors for the recognition of hazardous gases [H2 and di(propyleneglycol) monomethyl ether (DPGME) / dimethyl methyl phosphonate (DMMP), the latter used as simulants for chemical warfare agents]. Functional data evidenced the obtainment of low detection limits and promising gas responses, whose improvement with respect to the pristine MnO2 was traced back to the formation of built-in p-n and n-n junctions for CuO/MnO2 and SnO2/MnO2 systems, respectively. The possibility of discriminating between the target analytes depending on the functionalizing species already at moderate working temperatures demonstrates the potential of the developed materials for eventual gas sensing applications under real-world conditions.