nInP flat band potential: A pH probe in nonaqueous and mixed solvents?

The interface structure of the semiconductor/electrolyte junctions in nonaqueous solvents is an open question, and as in water, the study of the influence of pH on the flat band potential can lead to an important part of its knowledge and to applications such as pH measurements. In water, the flat band potential shifts of many semiconducting materials can be connected with pH shifts. In this paper we show it is the case for nInP electrodes in acetonitrile and methanol (96% in weight in water) at room temperature, and in liquid ammonia at low temperature, −55°C. Therefore this material can be used as a probe of pH. Using this property we were able to find again, for example, the values of the self-ionization constants of the studied solvents and the acidity constants of water in liquid ammonia and of acetic acid in methanol.