University of Delhi researchers have developed an environmentally friendly method to synthesize graphene oxide quantum dots (GO QDs) for use in ultrasensitive biosensors capable of detecting key neurological biomarkers such as dopamine and serotonin. The team’s novel approach employs citric acid as a green, biodegradable precursor, successfully producing uniform, negatively charged GO QDs with an average diameter of 23.4 nm.
The synthesized GO QDs were thoroughly characterized using UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), high-resolution X-ray diffraction (HR-XRD), and dynamic light scattering (DLS). The data confirmed the formation of pure, spherical QDs with well-defined structural integrity and optical stability, indicating precise control over quantum confinement and surface functionality.
To assess their biosensing performance, the GO QDs were tested using UV-Visible titration, fluorescence spectroscopy, and cyclic voltammetry (CV). These analyses revealed strong and specific interactions between the QDs and the analytes. For dopamine, a high binding constant of 2.077 × 10³ M⁻¹ was observed, while serotonin exhibited a value of 1.053 × 10³ M⁻¹. The fluorescence quenching behavior followed a clear resonance energy transfer (RET) mechanism, producing detection limits (LOD) as low as 0.7 nM for dopamine and 1.10 nM for serotonin.
Electrochemical measurements reinforced these findings. Cyclic voltammetry showed distinct oxidation peaks corresponding to dopamine and serotonin, further confirming the strong electron-transfer dynamics at the GO QD interface. The electrochemical limits of detection were 0.6 nM and 1.03 nM for dopamine and serotonin, respectively - both indicating remarkable sensitivity and selectivity for neurotransmitter detection.
This work not only advances the development of dual-mode (optical and electrochemical) biosensors but also demonstrates the potential of GO QDs as a next-generation nanomaterial for neurological diagnostics. By combining the quantum efficiency of traditional QDs with the high functional surface area of graphene oxide, the University of Delhi team achieved a robust, sustainable sensing platform that could pave the way for rapid, non-invasive biomarker detection in clinical and research applications.
