A novel porous anodic alumina based capacitive sensor towards trace detection of PCBs

To detect polychlorinated biphenyls (PCBs), a novel porous anodic alumina (PAA) based capacitive sensor working at room temperature has been developed. The parallel nanopores of PAA not only provide large surface area for PCB adsorption, but also benefit for the enhancement of capacitive response. By dropping the PCB methanol solution on the surface of PAA, it is convenient to load PCB into the nanopores by solvent evaporation. 3,3′,4,4′-tetrachlorobiphenyl (PCB77) was chosen as a typical sample of PCBs to investigate the sensing properties of the capacitive sensor. The capacitance of the PAA membrane shows remarkable enhancement after PCB77 solution was loaded while no significant change can be seen after the pure solvent was loaded. The capacitive sensor also shows good response to PCB77 even in the presence of the interferent of benzene. The sensing mechanism has been qualitatively discussed based on a parallel plate capacitor model. The detection limit is down to 8 × 10−8 M towards PCB77. The novel PAA based capacitive sensor exhibits great potential for practical application in trace detection of PCBs.