In this work, a novel sandwiched film of cadmium sulphide/reduced graphene oxide (CdS/r-GO) was synthesized and the modified electrodes were successfully used to simultaneously determine hydroquinone (HQ), catechol (CC) and resorcinol (RC).

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This paper presents a novel architecture for annular and circular electrode piezoelectric micromachined ultrasound transducers (AC-PMUTs) with mechanical grooves. The mechanical grooves reduce stress and increase the vibration area of the membrane, resulting in enhanced vibrational deformation amplitude, transmission sensitivity, mechanical coupling coefficient (), quality factor (Q), and emission sound pressure level (SPL). Compared with conventional AC-PMUTs without mechanical grooves, the transmitting displacement sensitivity was measured as 419.4 NM V−1, which increased by 128.73%; the mechanical coupling coefficient () was measured as 6.09%, which increased by 116.43%; and the quality factor (Q) was measured as 90.68, which is an increase of 241.3%. The mechanical grooves also increased the emission SPL of PMUT at the same operating frequency. In the range of 10 kHz–70 kHz, the emission SPL of the optimum AC-PMUT with mechanical grooves can be improved in the range of 2.8 dB–28.8 dB. In general, AC-PMUTs with mechanical grooves have great potential in various emission ultrasound applications, such as distance measurement and object detection.