Effects of Functionalization of TiO(2) Nanotube Array Sensors with Pd Nanoparticles on Their Selectivity

This study compared the responses of Pd-functionalized and pristine titanate (TiO(2)) nanotube arrays to ethanol with those to acetone to determine the effects of functionalization of TiO(2) nanotubes with Pd nanoparticles on the sensitivity and selectivity. The responses of pristine and Pd-functionalized TiO(2) nanotube arrays to ethanol gas at 200 °C were ∼2877% and ∼21,253%, respectively. On the other hand, the responses of pristine and Pd-functionalized TiO(2) nanotube arrays to acetone gas at 250 °C were ∼1636% and 8746% respectively. In the case of ethanol sensing, the response and recovery times of Pd-functionalized TiO(2) nanotubes (10.2 and 7.1 s) were obviously shorter than those of pristine TiO(2) nanotubes (14.3 and 8.8 s), respectively. In contrast, in the case of acetone sensing the response and recovery times of Pd-functionalized TiO(2) nanotubes (42.5 and 19.7 s) were almost the same as those of pristine TiO(2) nanotubes (47.2 and 17.9 s). TiO(2) nanotube arrays showed the strongest response to ethanol and Pd functionalization was the most effective in improving the response of TiO(2) nanotubes to ethanol among six different types of gases: ethanol, acetone, CO, H(2), NH(3) and NO(2). The origin of the superior sensing properties of Pd-functionalized TiO(2) nanotubes toward ethanol to acetone is also discussed.