Ultrasensitive detection of orthophosphate ions with reduced graphene oxide/ferritin field-effect transistor sensorsElectronic supplementary information (ESI) available: Sensing response of another sensor without a probe linker; control sensing test of the sensor without a probe; pH impact study; sensor recycling study. See DOI: 10.1039/c6en00661b

The phosphorus level is one of the major parameters in evaluating water eutrophication and there is an increasing demand for accurate and real-time monitoring technology for phosphorus determination. As a novel ion detection method, field-effect transistor (FET) sensors show a lot of potential in low-concentration and real-time orthophosphate ion detection. Here we report a reduced graphene oxide (rGO)-based FET platform for orthophosphate ion detection. The sensing platform was fabricated with rGO nanosheets as the sensing channel and ferritin as the specific detection probe for orthophosphate ions. The sensors hold great promise in real-time detection of orthophosphate ions with a lower limit of detection down to 26 nM (phosphorus level: 0.806 μg L −1 ), a response time on the order of seconds, and good selectivity in the presence of other interfering anions. Compared with standard optical methods, this electronic sensor could potentially be used for online and real-time monitoring of phosphorus in surface water. The phosphorus level is one of the major parameters in evaluating water eutrophication and there is an increasing demand for accurate and real-time monitoring technology for phosphorus determination.