The Effect of Surface Microstructure on The Response of Titanium Dioxide Coated with Cobalt-Porphyrin Thin Films Towards Gases in Quartz Crystal Microbalance Sensor

A single-layer and multi-layer titanium dioxide (TiO₂) coated with dye porphyrin thin films were prepared on Quartz Crystal Microbalance (QCM) using sol-gel dip coating method and were tested for sensing of volatile organic compounds (VOCs). The porphyrin was 2,3,7,8,12,13,17,18-octaethyl- 21H,23H-porphine cobalt (II). The sensing sensitivity was based on the change in the fundamental frequency of the QCM upon exposure towards three vapor samples, namely ethanol, acetone and 2-propanol. It was found that the thin films were sensitive towards all vapors and the sensing sensitivity was affected by the number of film layers. Although the three-layer film exhibited higher frequency response compared with the other films that have small number of layers, the sensing properties of this film are not repeatable and less selective. The performance of the QCM sensor was depended on microstructure of the thin film which was varied through the number layers.