Quartz crystal microbalance sensor based on nanostructured IrO sub(2)

Nanostructured IrO sub(2) crystals are grown on a gold-coated quartz substrate by metal organic chemical vapor deposition (MOCVD), and their gas sensing properties are studied by quartz crystal microbalance (QCM) technique. Several morphologies, such as nanoblade, layered-column, incomplete-nanotube and square-nanorod, are observed at various combinations of substrate temperature and precursor reservoir temperature. Propionic acid is found to be adsorbed and desorbed reversibly on the IrO sub(2) surface at room temperature, and the adsorption property depends on the nanostructure of the IrO sub(2). IrO sub(2) crystals with nanoblade and layered-column morphologies show higher sensitivities to propionic acid than those with incomplete-nanotube and square-nanorod morphologies. An IrO sub(2) QCM sensor sensitive to ppm-level propionic acid vapor at room temperature is demonstrated.