Mercury ion sensing by film-bulk-acoustic-resonator mass sensor

This paper describes an FBAR (film bulk acoustic resonator) mass sensor for detecting Hg2+ in liquid. With a thin Au film deposited on the Surface of an FBAR, the FBAR's resonant frequency shifts as Hg2+ amalgamates on the Au Surface. The FBAR,sensor is measured to be capable of detecting a concentration of 10(-9) M Hg2+ (i.e., 0.2 ppb Hg2+). Other cations such as K+, Ca2+, Mg2+, Zn2+, Ni2+ have shown to have little or no effect on the resonant frequency of the FBAR. Responses of the FBAR sensors coated with various thicknesses of Au film to a same concentration of Hg2+ have been compared. Finally, an FBAR with a thiol compound-modified Au film is shown to have a smaller frequency shift than that with a pure Au film.