Probe Sensor Using Nanostructured Multi-Walled Carbon Nanotube Yarn for Selective and Sensitive Detection of Dopamine

Abstract

The demands for electrochemical sensor materials with high strength and durability in physiological conditions continue to grow and novel approaches are being enabled by the advent of new electromaterials and novel fabrication technologies. Herein, we demonstrate a probe-style electrochemical sensor using highly flexible and conductive multi-walled carbon nanotubes (MWNT) yarns. The MWNT yarn-based sensors can be fabricated onto micro Pt-wire with a controlled diameter varying from 100 to 300 µm, and then further modified with Nafion via a dip-coating approach. The fabricated micro-sized sensors were characterized by electron microscopy, Raman, FTIR, electrical, and electrochemical measurements. For the first time, the MWNT/Nafion yarn-based probe sensors have been assembled and assessed for high-performance dopamine sensing, showing a significant improvement in both sensitivity and selectivity in dopamine detection in presence of ascorbic acid and uric acid. It offers the potential to be further developed as implantable probe sensors.

Keywords: Nafion coating; dopamine detection; multi-walled carbon nanotubes; nano yarn; probe sensor.

Figure 1

Schematic illustration of the preparation method of Nafion/MWNT Yarn (A–E); SEM images of MWNT yarn without/ with Nafion coating (F,G).

Figure 2

(A,B) High resolution SEM images of MWNT bundles without/ with Nafion coating respectively; (C) Raman spectra of pristine and Nafion-coated MWNT yarn; (D) FTIR spectra of uncoated and Nafion-coated MWNT yarn; (E) DPV of different thickness of Nafion layer (10 μM DA with 200 μM UA & AA ); (F) DPV of MWNT without and with Nafion coating (10 μM DA + 200 μM AA & UA each).

Figure 3

Electrochemical investigation of Nafion-coated MWNT yarn (A) CVs of 10 μM DA with 200 μM AA & UA (each) at scan rates: 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, and 200 mV/s; (B) DPV of thick layer Nafion in 200 μM UA & AA each with a range of DA: (0.2, 0.4, 0.6, 0.8, and 1) μM in PBS electrolyte with Calibration curve plot between DA concentrations and current response; (C) DPV of thin layer Nafion in 200 μM UA & AA with DA range: (0.2, 0.4, 0.6, 0.8, and 1) μM in PBS electrolyte with the calibration curve plot between DA concentrations and current responses; (D) DPV of thin layer Nafion in 200 μM UA & AA with a range of DA: (0.01, 0.02, 0.04, 0.06, 0.08, and 0.1) μM in PBS electrolyte with the calibration curve plot between DA concentrations and current response.

Figure 4

(A) Amperometric test of DA (0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 3, 4, and 5) µM in the presence of 10 µM of AA & UA each; (B) Calibration curve of corresponding DA concentrations plot vs. current response.