Interfacial Functionalization of TiO2 with Smart Polymers: pH-Controlled Switching of Photocurrent Direction

TiO2/P(NIPAM-AA) nanocomposites were successfully obtained by the incorporation of TiO2 nanoparticles (P25, commercial TiO2 nanoparticles from Degussa) with pH-stimuli responsive smart polymer [poly(N-isopropylacrylamide-co-acrylic acid), P(NIPAM-AA)]. Compared with the pure TiO2 nanoparticles, the incorporation of TiO2 nanoparticles with smart polymer P(NIPAM-AA) produced a significant effect on its photocurrent activities. The photocurrent behavior of TiO2/P(NIPAM) nanocomposites photoelectrode was tunable in response to pH stimuli. It was found that the nanocomposites photoelectrode produced an anodic photocurrent at pH 3.0, whereas it generated a relatively small cathodic photocurrent at pH 10.0. The pH-dependent swelling behavior of smart polymer played an important role in the pH-induced photocurrent switching, which actually was an intrinsic feature resulting from a specific electronic structure of the surface-modified semiconductor with smart polymer. The combination of the photoelectrochemical properties of inorganic semiconductor nanoparticles with external stimuli-responsive properties of organic smart polymers provides a new opportunity for controllable photocurrent switching.