Synthesis and characterization of exfoliated graphite-polypyrrole composites as active electrode materials for the detection of dopamine

Abstract

In this study, exfoliated graphite-polypyrrole (GPPy) composites were synthesized using three distinct graphite precursors featuring grain sizes of <50 µm, ≥149 – ≤840 μm, and 2000 µm. Graphite precursors underwent intercalation using sulfuric acid and potassium periodate oxidizer and were annealed at 800 °C to obtain exfoliated graphite (EG). During the wet-synthesis procedure, EG was further modified with the conductive polymer polypyrrole (PPy) to achieve GPPy samples. While GPPy composites have been widely studied for their application in energy storage devices due to their advantageous properties, their potential in electrochemical sensors has received limited attention. This lack of investigation represents a significant gap in current research, especially considering the growing need for sensitive and selective detection devices in medical diagnostics. In this work, the prepared GPPy samples were studied as active electrode materials for the detection of dopamine. Raman spectroscopy, FTIR, and XPS confirmed successful nitrogen incorporation into the graphitic structure after PPy modification. In addition, the sample obtained from the medium-size graphite grains (GPPy_2) had the highest elemental nitrogen content (5.12 at.%), with 15.16 % as graphitic-N, known to improve electrocatalytic activity. Electrochemical investigations revealed that the GPPy_2/GCE sensor demonstrated the most promising analytical parameters, including high sensitivity (2468 µA mM⁻¹ cm⁻²) and a low limit of detection value of 34 nM for the dopamine analyte. Therefore, our study suggests that GPPy-modified sensors offer a simple and cost-effective manufacturing approach, making them promising candidates as a highly sensitive tool for the detection of the neurotransmitter dopamine.