Dew condensation sensor based on surface plasmon resonance of periodic silver nanostructure on AT-cut quartz crystal

摘要

We propose a dew condensation sensor which combines surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) to measure both refractive index change and mass loading caused by dew condensation simultaneously. In order to excite SPR and enhance water vapor sorption, a periodic silver nanostructure is fabricated on an AT-cut quartz crystal oscillator by template deposition. A self-assembled membrane (SAM) which consists of polystyrene spheres with the diameter of 202 nm was used as the template, and silver thin film with the thickness of 45 nm was deposited on the SAM by vacuum evaporation. Sensitivities of the sensor for detection of dew condensation were evaluated as the shifts of the SPR extinction peak wavelength and the resonant frequency of quartz crystal. The sensor is cooled down with the chilling rate of-0.5 deg C/min in the environment-controlled chamber with relative humidity and the temperature of 43.2(percent)RH and 25.0 deg C, respectively. The proposed hybrid sensor was able to measure both the wavelength shifts of SPR and the additional mass caused by dew condensation simultaneously. Furthermore, the QCM response of the sensor achieved the sensitivity higher than the under detection limit (3 (mu)g/cm~(2)) of conventional optical detection method such as chilled mirror surface dew point hygrometer.