Piezoelectric microsensor for selective detection of low concentrations of ammonia

Abstract

This study developed an ammonia (NH3) sensor based on an electrode-width-controlled/single-phase unidirectional transducer surface acoustic wave (SAW) resonator coated with poly(diketopyrrolopyrrolethiophene-thieno[3,2-b]thiophene-thiophene) (DPP2T-TT) film. This sensor can be operated at room temperature and can detect NH3 at concentrations of the order of parts per billion (ppb). DPP2T-TT films were deposited on the surface of SAW devices using the drop-casting method and were characterized using X-ray diffraction, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Our developed sensor could linearly detect NH3 at concentrations of 50–1000 ppb in a dry air environment. This sensor exhibited a sensitivity of 48 Hz for 400 ppb NH3 in dry air, and the average response and recovery times were typically <45 s. The sensor also exhibited repeatability, reversibility, and long-term stability. Its sensitivity toward NH3 was 13 times higher than that toward other interfering gases, indicating its excellent selectivity.