Abstract
A thin film prepared from trimethylmethoxysilane by means of microwave plasma chemical vapor deposition have been applied to chemical sensors for organic substances. The film with a proper nanotexture and a hydrophobic surface terminated with methyl groups, and which consequently showed ultra water-repellency, was deposited on a quartz crystal microbalance (QCM) sensor. We evaluated changes in resonance frequency, that is, mass changes, of the QCM sensor due to adsorption of organic molecules. Organic substances, for example, formaldehyde, methanol, ethanol, acetone, toluene and hexane, preferentially adsorbed on the film, while the adsorption of water vapor was restricted due to the hydrophobic nature of the film. The amount of the adsorbed organic molecules seemed to depend on the polarity of each organic molecule. That is a less polar organic molecule adsorbed more preferentially to the film surface. The nanotexture of the film was crucial in order to enhance sensitivity of the chemical sensors through the increase in effective surface areas for the adsorption of organic molecules. Our chemical sensor is expected find applications in environmental sensors. This sensor selectively detects toxic organic substances that are not easily influenced.
