Improve the signal-to-noise ratio of a quartz crystal microbalance in an impedance analysis method.

A new data treatment method for the improvement of the signal-to-noise ratio of a quartz crystal microbalance (QCM) was proposed, where an averaged resonant frequency was calculated according to its conductance peak in an impedance analysis method. The relationship between the averaged resonant frequency and the medians of the conductance peak at different sampling heights was derived. It was shown that the signal-to-noise ratio of the averaged resonant frequency was about eight times of that of the resonant frequency calculated directly from its equivalent circuit parameters. The averaged resonant frequency of the QCM was applied to monitor the self-assembled process of a 6-O-(2'-(alpha-thiohydroxyacetamide)-ethyl)-diethoxylsilyl-beta-cyclodextrin (OTED-beta-CD), on gold surface as well as the adsorption of nitrophenol isomers onto the OTED-beta-CD self-assembled monolayer film.