Facile Preparation of Fe3O4/C Nanocomposite and Its Application for Cost-Effective and Sensitive Detection of Tryptophan

Abstract

In this study, we reported facile synthesis of Fe₃O₄/C composite and its application for the cost-effective and sensitive determination of tryptophan (Trp) in human serum samples. Fe₃O₄/C composites were prepared by a simple one-pot hydrothermal method followed by a mild calcination procedure, using FeCl₃∙6H₂O as Fe₃O₄ precursor, and glucose as reducing agent and carbon source simultaneously. The Fe₃O₄/C composite modified glassy carbon electrode (Fe₃O₄/C/GCE) was prepared by drop-casting method. The microstructure and morphology of Fe₃O₄/C composite was characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Due to large specific surface area and synergistic effect from Fe₃O₄ nanoparticles and carbon coating, Fe₃O₄/C composite showed excellent electrocatalytic activity toward the oxidation of Trp. As a result, the proposed Fe₃O₄/C/GCE displayed superior analytical performances toward Trp determination, with two wide detection ranges (1.0-80 μM and 80-800 μM) and a low detection limit (0.26 μM, S/N = 3). Moreover, successful detection of Trp in human serum samples further validate the practicability of the proposed sensor.

Keywords: Fe3O4/C composite; second derivative linear scan voltammetry; tryptophan; voltammetric detection.

Figure 1

XRD patterns of pure Fe₃O₄ NPs (curve a) and Fe₃O₄/C composite (curve b).

Figure 2

SEM images of pure Fe₃O₄ nanoparticles (a,b) and Fe₃O₄/C composite nanoparticles (c,d).

Figure 3

Electrochemical active areas of different electrodes were investigated by CV in 0.1 M PBS containing 0.5 mM of K₃[Fe(CN)₆].

Figure 4

CV (a) and second derivative linear scan voltammetry (SDLSV) (b) responses of 10 μM Trp on bare GCE, Fe₃O₄/GCE, and Fe₃O₄/C/GCE. Supporting electrolyte: 0.1 M PBS (pH 6.5); Scanning rate: 0.1 V/s.

Figure 5

Effect of solution pH on the electrochemical responses of 10 μM Trp. (a) CV curves in different pH PBS. (b) Effect of solution pH on the anodic peak currents (black line) and the anodic peak potentials (blue line). Supporting electrolyte: 0.1M PBS; Scanning rate: 0.1 V/s; Accumulation potential: 0.2 V; Accumulation time: 210 s.

Figure 6

Effect of scanning rate (v) on the electrochemical responses of 10 μM Trp. (a) CVs curves of 10 μM Trp on Fe₃O₄/C/GCE recorded at various scanning rates (v); (b) Linear relationship between the anodic peak currents (i_pa) and scanning rates (v); (c) Linear relationship between the anodic peak potentials (E_pa) and Napierian logarithm of scanning rates (lnv).

Scheme 1

Schematic diagram of the electrochemical mechanism of Trp oxidation.

Figure 7

Effect of accumulation potential (a) and accumulation time (b) on the anodic peak currents of 10 μM Trp.

Figure 8

curves of Trp with the concentrations ranging from 1 μM to 80 μM (a) and from 80 μM to 800 μM (b); Calibration curves between the anodic peak currents (i_pa) and Trp concentrations (c_Trp) in the range of 1–80 μM (c) and 80–800 μM (d). Supporting electrolyte: 0.1M PBS (pH 6.5); Scanning rate: 0.1 V/s; Accumulation potential: 0.2 V; Accumulation time: 210 s.

Figure 9

Response anodic peak currents of 10 μM Trp for ten successive measurements (n = 10).