Electrochemical nanosensors are based on detecting a resistance change in the nanomaterial upon binding of an analyte, due to changes in scattering or to the depletion or accumulation of charge carriers. One possibility is to use nanowires such as carbon nanotubes, conductive polymers, or metal oxide nanowires as gates in field-effect transistors, although as of 2009 they had not yet been demonstrated in real-world conditions. Chemical nanosensors contain a chemical recognition system (receptor) and a physiochemical transducer, in which the receptor interacts with analyte to produce electrical signals. In one case, upon interaction of the analyte with the receptor, the nanoporous transducer had a change in impedance which was determined as the sensor signal. Other examples include electromagnetic or plasmonic nanosensors, spectroscopic nanosensors such as surface-enhanced Raman spectroscopy, magnetoelectronic or spintronic nanosensors, and mechanical nanosensors.