Sensitive detection of gallic acid in food by electrochemical sensor fabricated by integrating nanochannel film with nanocarbon nanocomposite

Abstract

Sensitive detection of gallic acid (GA) in foods is of great significance for assessing the antioxidant properties of products and ensuring consumer health. In this work, a simple electrochemical sensor was conveniently fabricated by integrating vertically-ordered mesoporous silica film (VMSF) with electrochemically reduced graphene oxide (ErGO) and nitrogen graphene quantum dots (NGQDs) nanocomposite, enabling sensitive detection of GA in food sample. A water-soluble mixture of graphene oxide (GO) and NGQDs was drop-cast onto the common carbon electrode, glassy carbon electrode (GCE), followed by rapid growth of VMSF using an electrochemically assisted self-assembly method (EASA). The negative voltage applied during VMSF growth facilitated the in situ reduction of GO to ErGO. The synergistic effects of ErGO, NGQDs, and the nanochannels of VMSF led to nearly a tenfold enhancement of the GA signal compared to that obtained on electrodes modified with either ErGO or NGQDs alone. Sensitive detection of GA was realized with a linear concentration range from 0.1 to 10 μM, and from 10 to 100 μM. The limit of detection (LOD), determined based on a signal-to-noise ratio of three (S/N = 3), was found to be 81 nM. Combined with the size-exclusion property of VMSF, the fabricated sensor demonstrated high selectivity, making it suitable for the sensitive electrochemical detection of gallic acid in food samples.

Keywords: electrochemical reduced graphene; electrochemical sensor; gallic acid; graphene quantum dots; vertically-ordered mesoporous silica film.

Figure 1

Illustration for the fabrication of VMSF/NGQDs-ErGO/GCE sensor for electrochemical detection of GA by integrating VMSF with in situ formed ErGO and NGQDs nanocomposite.

Figure 2

(A) UV–Vis absorption spectra of NGQDs (0.3 mg/mL) and GO (0.1 mg/mL). (B–D) TEM image of GO (B), NGQDs (C), and NGQDs-GO nanocomposite (D) at high resolution.

Figure 3

(A) Top-view TEM image of VMSF. (B) Top-view HRTEM image of VMSF.

Figure 4

Cyclic voltammetry (CV) (A) and Nyquist plots (B) obtained on different electrodes in 0.1 M KCl solution containing 2.5 mM [Fe(CN)₆]^3−/4−. (C) The DPV curves obtained on different electrodes in GA solution. (D) The DPV currents obtained on VMSF/NGQDs-ErGO/GCE fabricated using different ratio of NGQDs and GO.

Figure 5

(A) DPV curves obtained on VMSF/NGQDs-ErGO/GCE in GA solution at different pH. The inset shows the relationship between peak potential and pH. Inset is the linear relationship between the peak current and pH. (B) CV curves obtained on VMSF/NGQDs-ErGO/GCE at different scan rate. Inset shows the linear relationship between the oxidation potential and scan rate. (C) DPV curves obtained at different enrichment times.

Figure 6

(A) DPV response to different GA concentrations. (B) The linear relationship between I_pa and GA concentration. (C) The rate of change of DPV signal in the absence (_I0) and presence (I) of different substance or their mixture. (D) DPV response obtained on five independent electrodes for GA detection (50 μM).