1 Electronic Supplementary Material

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3 Sensing Lorazepam with a glassy carbon electrode coated with an

4 electropolymerized-imprinted polymer modified with multiwalled

5 carbon nanotubes and gold nanoparticles

6 Behzad Rezaei*,1 • Omid Rahmanian • Ali Asghar Ensafi

7 Department of Chemistry, Isfahan University of Technology, Isfahan 84156−83111 8 I.R. Iran

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11 Electrochemical impedance spectroscopy measurements

12 Electrochemical impedance spectroscopy is a useful procedure for probing the 13 features of surface modified electrodes. The impedance spectra including a semicircle 14 part at high frequencies, corresponding to the electron transfer limited process and a 15 linear part at lower frequencies, demonstrating the diffusion-limiting step of the 16 electrochemical process. The semicircle diameter equals to the electron transfer 17 resistance at the electrode surface. Fig. S1 shows the electrochemical impedance 18 spectroscopy for the f−MWCNT/GCE, MIP/f-MWCNT/GCE and 19 AuNP/MIP/f−MWCNT/GCE. In this Figure shows a straight line for 20 f−MWCNT/GCE, which was characteristic of a diffusion-limiting step of the 21 electrochemical process. As predictable, by electropolymerization of ortho- 22 phenylenediamine onto f−MWCNT/GCE, electron transfer resistance was 23 significantly expanded which indicated the polymeric film performs as a definite 24 kinetic barrier for the electron transfer. By formation of Au nanoparticles, electron 25 transfer resistance was decreased that may be due to nanometer-sized gold particles

1 1*Corresponding author.Tel: +98-3113912351, Fax:+98-3113912350; 2 E-mail: [email protected]; [email protected] 3

1 26 participate a key role similarly to a conducting wire or electron-conducting tunnel and 27 therefore promoting electron-transfer reactions of probe.

16 f-MWCNT/GCE 14 MIP/f-MWCNT/GCE AuNP/MIP/f-MWCNT/GCE 12 10 Ω K

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Z 6 4 2 0 0 2 4 6 8 10 Z' / KΩ 28 29 Fig. S1. Impedance spectra of 5.0 mM hexacyanoferrate (III) and 0.1 M KCl at: 30 f−MWCNT/GCE; MIP/f−MWCNT/GCE and the AuNP/MIP/f−MWCNT/GCE 31 electrode. Conditions: Potential, 0.20 V; frequency range, 5.0 mHz to 100 kHz; and 32 AC voltage amplitude, 5.0 mV.

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34 Effect of pH

35 The pH of the solution in adsorption step has important effect on the Lorazepam 36 oxidation at the surface of the sensor. To make the best conformation of Lorazepam, 37 the pH of the sample should be adjusted. For this purpose, a series of phosphate buffer 38 solution were selected in the pH range of 5.0 to 8.0 containing 1.0 µM Lorazepam, 39 using 120 s as an incubation times. As can be seen in Fig. 5, the net current intensity 40 reaches maximum at a pH value of 7.5and decreased as the pH increases further. The 41 reason may be that the Lorazepam was protonated in acidic environment and cannot 42 be fitting into cavities. While, the stability of the imprinted film will be diminished in

2 43 high alkalinity and the Lorazepam was formed in anionic form. Therefore, pH 7.5 was 44 chosen as the proper pH for further researches.

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A 9 µ

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∆ 7 6 5 4 3 4 5 6 7 8 9 pH 45

46 Fig. S2. Effect of pH of working solution on Lorazepam adsorption in MIP cavities.

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50 (a) (b) 51 (c)

52 Fig. S3. The chemical structures of (a) Lorazepam, (b) Phenazopyridine and (c) 53 Hydrochlorothiazide.

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