Microplotter-Printed Graphene-Based Electrochemical Sensor for Detecting Phosphates

The fundamental understanding of the electrochemical transport of ions at the interface of nanoscale materials and its immediate environment lays the foundation to build electrochemical sensors for a wide variety of chemical, biological, and environmental problems. Therefore, enabling an efficient electron transfer from the environment to an atomically thin, two-dimensional material such as graphene and vice versa provides a route to building graphene-based electrochemical sensors. Although many graphene-based electrochemical sensors have been reported in recent years, there have been limitations in designing and manufacturing them to monitor phosphate ions in the environment. This limitation primarily arises from the lack of high-performance printable graphene nanoinks (in terms of their combined electrical conductivity and electrochemical charge transfer properties) as well as complexity in the detection of phosphate ions. Herein, we report the manufacturing of a high-quality graphene nanoink and its use for the first time in fabricating stable and reliable printed phosphate ion electrochemical sensors using a microplotter. These sensors demonstrate a sensitivity of 0.3223 ± 0.025 μA μM–1 cm–2, with a limit of detection (LOD) of 2.2 μM and linear sensing range of 1–600 μM. Moreover, they exhibit high selectivity toward phosphates when tested in the presence of NO3 –, CO3 –, Cl–, and SO4 2– interfering ions, affirming their reliability as a sensing platform. Phosphate electrochemical sensing using the proposed printed graphene sensors will pave the way for future development of point-of-care and continuous phosphate monitoring in environmental sensing.