Electrochemical Sensing of Vanillin Based on Fluorine-Doped Reduced Graphene Oxide Decorated with Gold Nanoparticles

Abstract

4-hydroxy-3-methoxybenzaldehyde (vanillin) is a biophenol compound that is relatively abundant in the world's most popular flavoring ingredient, natural vanilla. As a powerful antioxidant chemical with beneficial antimicrobial properties, vanillin is not only used as a flavoring agent in food, beverages, perfumery, and pharmaceutical products, it may also be employed as a food-preserving agent, and to fight against yeast and molds. The widespread use of vanilla in major industries warrants the need to develop simple and cost-effective strategies for the quantitative determination of its major component, vanillin. Herein, we explore the applications of a selective and sensitive electrochemical sensor (Au electrodeposited on a fluorine-doped reduced-graphene-oxide-modified glassy-carbon electrode (Au/F-rGO/GCE)) for the detection of vanillin. The electrochemical performance and analytical capabilities of this novel electrochemical sensor were investigated using electrochemical techniques including cyclic voltammetry and differential pulse voltammetry. The excellent sensitivity, selectivity, and reproducibility of the proposed electrochemical sensor may be attributed to the high conductivity and surface area of the formed nanocomposite. The high performance of the sensor developed in the present study was further demonstrated with real-sample analysis.

Keywords: Au nanoparticles; differential pulse voltammetry; electrochemical sensor; reduced graphene oxide; vanillin.

Figure 1

SEM images of (A) F-rGO, and (B) Au/F-rGO.

Figure 2

(A) Cyclic voltammograms of the response of bare GCE (black), Au/GCE (red curve), F-rGO/GCE (blue curve) and Au/F-rGO/GCE (pink curve) in 0.1 M KCl solution containing 5.0 mM [Fe(CN)₆]^3−/4− at the scan rate of 50 mV/s. (B) Cyclic voltammograms of the response of Au/F-rGO/GCE at various scan rates (10–200 mV/s¹). (C) Plots of redox peak current response against the square root of the scan rate.

Figure 3

(A) Cyclic voltammograms of the bare GCE (black curve), Au/GCE (red curve), and Au/F-rGO/GCE (blue curve) recorded in a 0.1 M PBS solution (pH 7.0) containing 500.0 µM vanillin at a scan rate of 50 mV/s. (B) Cyclic voltammograms and (C) differential pulse voltammograms of the Au/F-rGO/GCE in a 0.1M PBS solution in the absence (black curve) and in the presence of 500.0 µM vanillin (blue curve).

Figure 4

(A) Linear sweep voltammogram and (B) differential pulse voltammogram of the response of various Au/F-rGO/GCE electrodes (with different Au-deposition times: 125, 250, 500, and 750 s) in 0.1 M PBS solution (pH 7.0) containing 500.0 µM vanillin. (C) Relationship of Au-NP-deposition time with respect to the anodic peak current.

Figure 5

(A) Linear sweep voltammogram of the response of Au/F-rGO/GCE in 0.1 M PBS solution (pH 7.0) containing various vanillin concentrations (300.0 to 1500.0 μM). (B) Linear relationship between the oxidation of vanillin (anodic peak current) with respect to various concentrations. Scan rate: 50 mV/s.

Figure 6

(A) Differential pulse voltammograms of Au/F-rGO/GCE in 0.1 M PBS solution (pH 7.0) containing various vanillin concentrations (1.0 to 150.0 μM). (B) Linear relationship between the oxidation of vanillin (anodic peak current) with respect to various concentrations. Scan rate: 50 mV s⁻¹.