Van Thanh P.Nhu L.T.Q.Mai H.H.Tuyen N.V.Nguyen Canh, VietVietNguyen CanhDoanh S.C.Kien D.T.2025-08-122025-08-12201710.1007/s11664-017-5369-0https://scholar.vnu.edu.vn/handle/123456789/6446Zinc oxide (ZnO) nanorods (NRs) were grown directly on printed circuit boards with a 35-μm-thick copper layer using a seedless galvanic-cell hydrothermal process. The hexagonal structure of the synthesized ZnO NRs was observed by scanning electron microscopy. The microstructural characteristics of the as-grown ZnO NRs were investigated by x-ray diffraction analysis, revealing preferred (002) growth direction. Raman and photoluminescence spectra confirmed the high crystalline quality of the ZnO NRs. As-grown ZnO NRs were then grown for 7 h using the galvanic effect for use as the pH membrane of an extended-gate field-effect transistor pH sensor (pH-EGFET). The current–voltage characteristics showed sensitivity of 15.4 mV/pH and 0.26 (μA)1/2/pH in the linear and saturated region, respectively. Due to their cost effectiveness, low-temperature processing, and ease of fabrication, such devices are potential candidates for use as flexible, low-cost, disposable biosensors. © 2017, The Minerals, Metals & Materials Society.Englishextended-gate field-effect transistor (EGFET)ion-sensitive field-effect transistor (ISFET)pH sensorprinted circuit boardZnO nanorodsArticle