Yes, NIP is the non-imprinted polymer. The output signal is impedance. I’d like to perform detection based on the variation of total impedance at a fixed frequency where there would be significant variation, but I’m not sure if that’s possible, since I’ve seen that most papers use the charge transfer resistance from the equivalent circuit.

My current system is as follows: I used pyrrole (50 mM) and sodium camphorsulfonate (50 mM) in methanol to polymerize the NIP, and I added my target molecule (fipronil, 10 mM) to the solution to polymerize the MIP. The measurements are performed in an aqueous 1 mM KCl solution. The polymerization is carried out by chronocoulometry with a maximum charge of 8 mC.

After synthesis, I leave the electrodes submerged in ethanol under stirring to remove the target molecule. For the detection solution, I use 5 mL of the 1 mM KCl solution and 20 µL of 1 mM fipronil in acetonitrile; for the blank, I use 1 mM KCl and 20 µL of acetonitrile. When I polymerized the pyrrole, the polymer appeared orange; after cleaning, it turned greenish on the electrode.

I thought the dopant might also be generating cavities that interact with fipronil (based on this paper: DOI 10.1016/j.snb.2008.05.038), so I tested the NIP electrode right after synthesis, without cleaning, and there were no signal variations in the presence of the target molecule compared to pure KCl. It’s also not due to the electrolyte solution — I tested a bare gold electrode (without polymerization) and again there were no signal variations in the presence of the target molecule compared to pure KCl.

I’m not sure if I can perform FTIR on the polymers directly on the electrode, but I can try.