Surface Tailoring for Controlled Photoelectrochemical Properties: Effect of Patterned TiO2 Microarrays

Abstract

In efforts to make use of unprecedented physical and chemical characteristics of titania (TiO2) nanomaterials and investigate their innovative developments in microsystem applications, it is essential to affix them on surfaces or arrange them in an organized network. In this work, a simple, fast, and cheap patterning technique for the fabrication of patterned TiO2 microarrays with different features is presented. As an alternative to typical pattern transfer techniques for microfabrication, this work employed a standard microcontact printing (μCP) process for the fabrication of patterned titania microarrays onto F-doping SnO2 (FTO) conductive glass substrates. During the μCP process, the titania precursor was used as the “ink” and transferred from a pattern-featured poly(dimethylsiloxane) “stamp” onto the pretreated FTO substrate. Following the subsequent thermal oxidation, patterned TiO2 microarrays with different features (100, 200, and 400 μm) were successfully achieved. The surface properties and the photoelectrochemical properties of as-prepared patterned TiO2 microarrays were investigated by scanning electron microscopy, X-ray diffraction, UV−vis absorption spectroscopy, electrochemical impedance spectroscopy, Mott−Schottky spectroscopy, photocurrent action spectroscopy, and photocatalytic degradation. It was demonstrated that these properties were dependent on the feature size of the TiO2 patterns. For the patterned TiO2 thin film photoelectrodes with 100, 200, and 400 μm patterns, the generated peak photocurrent was ca. 5, 2, and 1 nA, and the photodegradation rate constant of methylene blue was found to be 1.747%, 1.415%, and 0.96% min-1, respectively. Clearly, with the decrease of the feature size, the photocurrent action and photocatalytic ability of the patterned TiO2 thin film increased, which was due to the increased TiO2 surface area as well as the increased optical path length within the patterned TiO2 thin film, resulting from multiple reflection of incident light. This work indicates that patterned TiO2 thin films are attractive systems for surface tailoring and also provide a novel method to effectively control the photoelectrochemical properties of nanostructured TiO2 thin films with promising applications in microsystem devices for solar energy conversion, photocatalysis, sensing, and so on.