A highly sensitive electrochemical sensor by growing Ag nanoparticles on the surface of PPy@PEDOT:PSS film for detecting sodium hydroxymethanesulfinate molecules

Abstract

A high-sensitivity electrochemical sensor was fabricated via in situ growth of Ag nanoparticles (AgNPs) on the surface of a polypyrrole@poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PPy@PEDOT:PSS) film for detecting sodium hydroxymethanesulfinate (SHF) molecules in milk and rice flour samples. The sensor fabrication process involved randomly decorating Ag seed points on the porous PPy@PEDOT:PSS film via a chemical reduction process using a AgNO₃ solution. Next, AgNPs were anchored on the PPy@PEDOT:PSS film surface using an electrochemical deposition method to prepare a sensor electrode. Under optimal conditions, the sensor exhibits a good linear relation within a range of 1-130 ng/mL for real milk and rice flour samples and its limit-of-detection values were up to 0.58 and 0.29 ng/mL, respectively. Additionally, Raman spectroscopy was used to identify the byproducts of the chemical reaction, such as formaldehyde. This AgNP/PPy@PEDOT:PSS film-based electrochemical sensor offers a simple and rapid method for detecting SHF molecules in food products.

Keywords: Ag nanoparticles (AgNPs); Differential pulse voltammetry; Electrochemical sensor; Milk matrix; Polypyrrole@Poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate); Raman spectroscopy; Sodium hydroxymethanesulfinate.

Fig. 1

Schematic map of in situ electrochemical Raman signal measurement system.

Fig. 2

Scanning electron microscopy images of (A) PPy@PEDOT:PSS/SLT film surface and (B) AgNPs/PPy@PEDOT: PSS/SLT electrode.

Fig. 3

(A) Energy-dispersive X-ray spectroscopy map of AgNPs; (B) X-ray diffraction pattern of AgNPs; (C) Fourier transform infrared spectra of PEDOT:PSS and PPy@PEDOT:PSS.

Fig. 4

(A) Cyclic voltammograms curves and (B) EIS spectra of SLT, PPy@PEDOT: PSS/SLT, AgNPs/SLT, AgNPs/PPy@PEDOT: PSS/SLT in a mixture solution of 1.0 mM K₃Fe(CN)₆/K₄Fe(CN)₆ and 0.1 M KCl.

Fig. 5

(A) Cyclic voltammetry (CV) curves of 20-ng/mL SHF in the 0.2-M PBS support electrolytes (pH = 7.6) on AgNPs/PPy@PEDOT: PSS/SLT; (B) Raman signal during the CV measurement; (C) CV curves of 20-ng/mL SHF in 0.2-M PBS (pH = 7.6) at bare SLT, PPy@PEDOT: PSS/SLT, AgNPs/SLT, AgNPs/PPy@PEDOT: PSS/SLT; (D) DPVs of 20 ng/mL SHF in the pH range of 4.0–10.0 at AgNPs/PPy@PEDOT: PSS/SLT.

Fig. 6

(A) Differential pulse voltammetry (DPV) curves of SHF at different concentrations (1, 10, 20, 40, 60, 80, 100, 110, 120, and 130 ng/mL). (B) Curve Fitting curve between DPV response peak values and different concentrations of SHF.

Fig. 7

(A) Cyclic voltammetry (CV) curves of the PBS electrolyte solution, and the CV curves of SHF in PBS solution and in milk and rice flour samples; (B) Raman spectra of the PBS electrolyte solution and SHF in PBS solution and and milk and rice flour samples obtained during CV measurement.

Fig. 8

(A) Differential pulse voltammetry (DPV) curves for SHF in the PBS solution and milk and rice flour samples; (B) DPV curves for different concentrations of SHF in milk samples; (C) DPV curves for different concentrations of SHF in rice flour samples; (D) Linear fitting curves between the DPV response peak currents and different concentrations of SHF in milk ((black line) and rice flour (red line) samples. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)