A New Core@Shell Silica-Coated Magnetic Molecular

Imprinted Nanoparticles for Selective Detection of Sunset

Yellow in Food Samples

Majid Arvand*. Zahra Erfanifar . Masoomeh Sayyar Ardaki

Electroanalytical Chemistry Laboratory, Faculty of Science, University of Guilan, Namjoo

Street, P.O. Box: 1914–41335, Rasht, Iran

*Corresponding author. Tel.: +98131 33233262, fax: +98 131 33233262

E-mail address: arvand@guilan.ac.ir (M. Arvand)

The Effect of Gr and MIP Quantity

In our investigations, we intended to study the amount of Gr powder and MIP nanoparticles

on the sensor efficiency. Results showed that the peak current of SY increased with increasing

the concentration of Gr suspension up to 10 mg/mL; then it decreased gradually. This might be

attributed to the low mechanical stability of the composite film when it contained proportionally

more Gr compared to the Nafion. Therefore, 10 mg/mL Gr suspension was used for casting onto

the GCE surface.

It is well-known that the sensitivity of the MIP sensor is controlled by the amount of effective

imprinted sites on its surface. The amount of the imprinted sites increases with the increase in the

thickness of MIP layer. The thickness of MIP layer can easily be controlled by adjustment of

concentration of MIP nanoparticles suspension. The CV response to SY obviously rose and

reached a maximum when the MIP nanoparticles amount was less than 6.0 mg/mL and then

decreases with a further increase in its concentration. This result indicated that by increasing of

the MIP nanoparticles content in the sensing film up to 6 mg/mL, the amount of imprinted

sites increased. When the amount of MIP nanoparticles was too much (higher than 6

mg/mL), the thick film of MIP nanoparticles hindered the mass transport and the electron

transfer. In fact, thick MIP nanoparticles layer would lead to low binding capacity, poor site

accessibility and slow binding kinetics.

Effect of Incubation Time and Potential

In order to explore the influence of incubation time to the response of the sensor and find the

optimal incubation time, the electrode was incubated in a stirring 0.1 mol/L ABS (pH 4.4)

containing 100 μmol/L SY for different incubation time (from 5 to 50 min). The plot of anodic

peak current as a function of incubation time indicated that the current response of SY

significantly increased with an increase of incubation time from 5 to 30 min. This remarkable

signal enhancement indicated that incubation was feasible to improve the detection sensitivity.

Longer incubation time than 30 min did not enhanced the oxidation peak current of SY,

indicating the saturated rebinding of SY took place onto the MIP sensor surface. Thus, the

optimum incubation time should be 30 min for the electrochemical determination of SY.

The effect of incubation potential on the peak intensity was also investigated over the range of

-0.1 – 0.5 V. With the change of incubation potential, the peak current varied slightly. Therefore,

the incubation potential had no such effect on the peak intensity and the incubation was carried

out at open-circuit conditions.

Fig. S1 (A) Cyclic voltammograms of (a) bare GCE, (b) Fe3O4@SiO2-NPs@NIP/Gr/GCE, (c)

Fe3O4-NPs/Gr/GCE, (d) Fe3O4@SiO2-NPs/Gr/GCE and (e)

Fe3O4@SiO2-NPs@MIP/Gr/GCE in 5 mmol/L K3[Fe(CN)6] containing 0.1 mol/L KCl

(scan rate: 0.1 V/s). (B) Nyquist plots of EIS in the solution containing 5 mmol/L

[Fe(CN)6]3−/4− solution as probe and 0.1 mol/L KCl as supporting electrolyte

Fig. S2 (A) Cyclic voltammograms of SY (100 µmol/L) in 0.1 MPBS (pH 8) at different scan

rates (V/s) with Fe3O4@SiO2-NPs@MIP/Gr/GCE. (B) Linear relationship of anodic and

cathodic peak currents (Ip) vs. scan rate (ν). (C) Relationship between the logarithmic

peak current and the logarithmic scan rate for the anodic peak

Fig. S3 (A) Variations of redox peak current (Ip) with respect to pH of the electrolyte. (B) Linear

relationship of the anodic peak potential (Epa) vs. pH

Fig. S4 DPVs obtained for orange flavored jelly powder sample in PBS (0.1 mol/L, pH 8.0) before

(dashed line) and after spiking with different SY concentrations