English: Schematic diagram of (a) amperometric/voltammetric, (b) potentiometric, (c) conductometric biosensors, and (d) equivalent circuit of the impedimetric biosensor (Cdl = double-layer capacitance of the electrodes, Rsol = resistance of the solution, Cde = capacitance of the electrode, Zcell = impedance introduced by the bound nanoparticles, and Rcell and Ccell are the resistance and capacitance in parallel).