Photochemiresistor sensor development based on a bismuth vanadate type semiconductor for determination of chemical oxygen demand.

The present paper describes the development of a novel photochemiresistor sensor for the determination of chemical oxygen demand (COD). A chemiresistive circuit element is fashioned from a thin film of a monoclinic phase of bismuth vanadate deposited on an FTO glass surface. Electrochemical impedance spectroscopy shows that the resistive properties of the sensor platform depend on the presence of the organic material in aqueous solution and the incidence of light. The decrease in resistance can be explained by considering that by increasing the amount of organic material, the amount of charge transferred to BiVO4 increases, as does the amount of the photogenerated conduction band on the film. This behavior is not observed when carrying out the same measurements in the absence of light. Under the optimal experimental conditions, the linear response of the chemiresistor sensor is between 0.20 mg L(-1) and 19.9 mg L(-1) COD at a fixed AC frequency of 0.1 Hz. There is a good correlation between the charge transfer resistance and COD concentration in the electrolyte solution. The sensor was successfully applied for the determination of COD in waste and lake waters. The results obtained using the sensor method are in good agreement with those obtained using the conventional COD method.