A voltammetric sensor based on reduced graphene oxide-hemin-Ag nanocomposites for sensitive determination of tyrosine

Abstract

A novel voltammetric sensor was designed and used for the determination of l-tyrosine (l-Tyr) by surface modification of a glassy carbon electrode with reduced graphene oxide-hemin-Ag (rGO-H-Ag) nanocomposites. The nanocomposites were synthesized by a facile one-pot hydrothermal method and characterized by means of transmission electron microscopy and Raman spectroscopy. The determination of l-Tyr was investigated by cyclic voltammetry and further quantified using differential pulse voltammetry. The results revealed a significant enhanced electrochemical oxidation effect for l-Tyr at the nanocomposites modified electrode. Two linear ranges from 0.1 to 100 μM and 100 to 1000 μM as well as a low detection limit of 30 nM (S/N = 3) were obtained. In addition, the sensor also demonstrated good selectivity, reproducibility and stability.

Scheme 1. Schematic of the preparation of rGO-H-Ag nanocomposites for the voltammetric determination of l-Tyr.

Fig. 1. Typical TEM images of GO (A), rGO-H (B), low (C) and high (D) magnification images of rGO-H-Ag nanocomposites; the EDX spectra of different sized particles (E and F) over the rGO surface.

Fig. 2. Raman spectra of GO (a), hemin (b) and rGO-H-Ag nanocomposites (c).

Fig. 3. CVs of rGO-H/GCE (a) and rGO-H-Ag/GCE (b) in N₂-saturated 0.2 M pH 7.0 PB (A); CVs of rGO-H-Ag/GCE in N₂-saturated 0.2 M pH 7.0 PB (B). Scan rate: 100 mV s⁻¹.

Fig. 4. CVs of rGO-H-Ag/GCE in N₂-saturated 0.2 M pH 7.0 PB at different scan rates (inner to outer) 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 mV s⁻¹ (A); plots of oxidation and reduction peak currents vs. scan rate (B).

Fig. 5. CVs of rGO-H-Ag/GCE in the absence (a) and presence (b) of 0.2 mM l-Tyr in N₂-saturated 0.2 M pH 7.0 PB, and CV of rGO-H/GCE in the presence of 0.2 mM l-Tyr in N₂-saturated 0.2 M pH 7.0 PB (c). Scan rate: 100 mV s⁻¹.

Fig. 6. DPVs of various concentration of l-Tyr (from bottom to top, 0.1–1000 μM) at rGO-H-Ag/GCE in N₂-saturated 0.2 M pH 7.0 PB (A), the calibration plots of oxidation peak current vs.l-Tyr concentration (B). Inset: DPVs (A) and calibration plots (B) for l-Tyr with low concentrations (0.1–20 μM).