Review—Graphene-Based Water Quality Sensors

Water is fundamental to most aspects of human civilization and terrestrial life in general. The problem of deteriorating water quality is very real, but often hard to quantify for lack of data. Hence the development of water quality sensors has become an urgently important area of research. Here we summarize an emerging class of water quality sensors based on field effect or chemiresistive geometries, which work completely in the solid state and can operate without reference electrodes. Such devices are candidates for continuous online monitoring applications of surface, ground, drinking, process, and wastewater streams. Single layer and few layer graphenes are suitable materials for the sensing channels in these devices due to their chemical and mechanical robustness and favorable electronic properties. While single layer graphene devices are more sensitive, few layer graphene sensors are easier to manufacture at a lower cost and offer a wider dynamic range. Detection of pH, disinfectants, mercury, lead, chromium, arsenic, potassium, calcium, some anions, as well as organic and biological species has all been demonstrated at the proof of concept stage, with much more work in progress. One can anticipate the commercial availability of such devices in the near future.