# Metal-Free Electrochemical Dopamine Sensing Using a g-C3N4/Polymethyl Thymol Blue Nanohybrid

## TL;DR

A new metal-free sensor detects dopamine accurately in complex biological samples using a nanohybrid material.

## Contribution

A novel g-C3N4/PM TB nanohybrid enables selective and sensitive dopamine sensing without metal catalysts.

## Key findings

- The sensor achieved interference-free detection of dopamine in the presence of uric acid and ascorbic acid.
- The sensor showed a wide linear range and high sensitivity with an ultralow detection limit.
- The sensor's accuracy was validated in artificial biofluids and matched HPLC results.

## Abstract

We report a highly sensitive and interference-free electrochemical sensor for dopamine (DA) detection in the presence of uric acid (UA) and ascorbic acid (AA), based on an in situ deposited graphitic carbon nitride (g-C3N4) and polymethyl thymol blue (PMTB) nanohybrid modified screen-printed carbon electrode (SPCE). The as-fabricated g-C3N4/PMTB/SPCE was thoroughly characterized using various physicochemical techniques. The electrochemical behavior of the modified electrode was systematically investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The g-C3N4/PMTB/SPCE exhibited excellent electrocatalytic activity toward the selective oxidation of DA under optimized experimental conditions, including pH and scan rate. Interference-free detection of DA in the presence of AA and UA was achieved using DPV and chronoamperometric methods, revealing a wide linear concentration range, an ultralow limit of detection, and high sensitivity. Furthermore, the practical applicability of the proposed sensor was validated by determining DA in artificial biofluid samples, including blood serum, and urine. The recovery results obtained good agreement with those obtained using high-performance liquid chromatography (HPLC), confirming the reliability and accuracy of the developed sensing platform.