Flexible sensor with electrophoretic polymerized graphene oxide/PEDOT:PSS composite for voltammetric determination of dopamine concentration

Abstract

We demonstrate a novel, flexible sensor with graphene oxide/PEDOT:PSS (GO/PEDOT:PSS) composite for voltammetric determination of selective low levels of dopamine. The well-distributed GO and EDOT:PSS suspension in water were deposited simply and polymerized. Consequently, the EDOT:PSS provided a strong interaction between GO and PEDOT:PSS, and it also had well-tailored interfacial properties that allowed the highly selective and sensitive determination of DA. Since the interfacial net charge is well-constructed, the sensor satisfies both the requirements of selectivity and the highly sensitive detection of low amounts of DA. In the results, the sensor with the GO/PEDOT:PSS composite exhibited a low interfacial impedance of about 281.46 ± 30.95 Ω at 100 Hz and a high charge storage capacity (53.94 ± 1.08 µC/cm²) for the detection of dopamine. In addition, the interference from ascorbic acid was reduced effectively to a minimum by electrostatic charge repelling of the AA and the distinct difference for the oxidation peak of the UA. Due to the fact that the GO/PEDOT:PSS composite had a net negative charge and, enhanced interfacial properties, the sensor showed a dopamine detection limit of 0.008 μM and a sensitivity of 69.3 µA/µMcm².

Figure 1

(a) Schematic drawing of the electropolymerization process of the GO/PEDOT:PSS composite on an Au working electrode and the configuration of the flexible sensor with the GO/PEDOT:PSS composite as a working electrode; (b) the comparison of the impedance and (c) cyclic voltammogram of Au, PEDOT:PSS, GO and GO/PEDOT:PSS composite in a 0.1 M PBS solution (pH 7.4). The scan rate was 100 mVs⁻¹.

Figure 2

Scanning electron microscopy images of the fabricated (a) Au, (b) GO, (c) PEDOT:PSS, and (d) GO/PEDOT:PSS (mixture ratio of 5:1, polymerization time of 300 s) composite. All images display a 10,000 × magnification of the electrode surfaces. The scale bars represent 5 µm.

Figure 3

Comparison of the (a) C1s peaks of XPS spectra for GO, PEDOT:PSS, and GO/PEDOT:PSS composite; (b) Comparison of the S2p peaks for PEDOT:PSS and the GO/PEDOT:PSS composite.

Figure 4

(a) Cyclic voltammograms of the sensor with GO/PEDOT:PSS composite to 1 mM DA concentration by various scan rates (10–100 mVs⁻¹); (b) Linear fitting of the oxidation peak currents to the various scanning rates (n = 3); (c) cyclic voltammograms of the sensor with GO/PEDOT:PSS composite to the 1 mM AA, 5 μM DA, and 50 μM UA by various scan rates (10–100 mVs⁻¹); (d) Linear fitting of the peak oxidation currents to 5 μM DA (n = 3).

Figure 5

(a) DPV curve of the sensor with the GO/PEDOT:PSS composite to various DA concentrations (0, 0.008, 0.01, 0.1, 0.5, 1, 5, 10, 30, and 50 μM) in 0.1 M PBS (pH 7.4); (b) A linear fitting for the DPV oxidation peak currents to the various DA concentrations (n = 3); (c) DPV curve of the sensor with GO/PEDOT:PSS composite to the different DA concentrations (0, 0.01, 0.1, 1, 5, 10, 30, 50, and 100 μM) in 0.1 M PBS (pH 7.4) that contained 1 mM AA and 50 μM UA; (d) A linear fitting of the DPV oxidation peak currents to the various DA concentrations (n = 3).