Development of an electrochemical microsensor based on algal metabolism for the detection of water pollutants

An autonomous electrochemical microsystem with three electrodes integrated on the same silicon chip was developed by means of silicon based microfabrication technology. Platinum (Pt), platinum black (Pt), tungsten/tungsten oxide (W/WO₃) and iridium oxide (IrO_x) working electrodes were developed. Ag/AgCl and Pt were used as reference and counter integrated electrodes respectively. The electrodes were employed for the detection of O₂, H₂O₂ and OH^-, species taking part in photosynthetic and metabolic activities of algae. By measuring the variations in consumption-production rates of these species, the quantity of herbicides present in the solution can be estimated. Fabricated microelectrodes were characterized and calibrated. Pt Black microelectrodes exhibited the greatest sensitivity regarding the O₂ and H₂O₂ detection while IrO_x were more sensitive compared to W/WO₃ microelectrodes for pH measurement. Bioassays were then conducted in algal solutions for the detection of Diuron herbicide, the presence of which is indicated by a variation in O₂ production by algae.