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/WO
₃
) 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 O
₂
, H
₂
O
₂
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 O
₂
and H
₂
O
₂
detection while IrO
_x
were more sensitive compared to W/WO
₃
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 O
₂
production by algae.