The response of QCM sensor coated with polystyrene in contact with potassium chloride solution

Quartz Crystals Microbalance responds to the coating film physical property change which is affected by the contacting liquid on the film surface. One of the liquid effects of the film is the film swelling effect. The swelling of the film changes the density of the film and could also be the modulus elasticity. Potassium chloride in water has ionic strength which makes the polystyrene swell. This work shows the effect of the potassium chloride (KCl) solved in distilled water to the polystyrene film which results in a frequency change of the QCM sensor coated with polystyrene. KCl solution with varying concentrations is used to observe the effect of ionic strength on the resonance frequency and minimum impedance of the QCM sensor coated with polystyrene. The resonance frequency of the QCM sensor in contact with the KCl solution changes continuously. It shows a continuous additional mass to the sensor surface. The frequency change was much higher than calculated frequency change caused by the deposition of the KCl on the sensor surface. The effect of the swelling is also indicated by the significant change of the minimum impedance of the sensor in contact with the KCl solution. The minimum impedance is than the minimum impedance in contact with water. It shows that the modulus elasticity of the film changed caused by swelling effect.