A simple electrochemical pH sensor based on black phosphorus nanosheets

In this work, black phosphorus nanosheets (BPNSs) were prepared by liquid exfoliation in N-methyl-2-pyrrolidone (NMP) and characterized by TEM, AFM, Raman spectroscopy and UV-vis absorption spectroscopy. A novel electrochemical sensor was constructed based on the BPNSs and used to measure pH. As the pH of the solution increases, the oxidation current of the BPNSs decreases. The oxidation degree of the BPNSs may be responsible for their different electrochemical responses to pH. The zeta potentials of the BPNSs also appear to be more negative at higher pH values. The results show that the sensor has a linear response in the pH range 1.0-8.0. The resulting electrochemical sensor could thus be used for accurate pH measurement and was successfully applied to the determination of pH in blood and food samples. The proposed method is simple but is shown to have high accuracy, versatility and applicability.