ZnO NR applications in nonoptical modes of biodetection. (a) A typical three-electrode amperometric electrochemical measurement setup. (b) MOSFET-based potentiometric electrochemical sensor utilizing extended-gate functionalized ZnO NRs as WEs. In both sensing approaches, conventional electrode surfaces of silver, gold, glassy carbon, or glass capillary are modified with a dense layer of ZnO NRs and exploited as a sensing electrode. (c) A single ZnO NR-based FET biosensor is shown. Figure adapted from Reference 60 with permission. Copyright 2010 Elsevier. Abbreviations: CE, counter electrode; FET, field-effect transistor; MOSFET, metal-oxide-semiconductor field-effect transistor; NR, nanorod; PMMA, polymethylmethacrylate; RE, reference electrode; WE, working electrode.