Thiazole-resorcinol azo dye platform: electrochemical sensing of dopamine, paracetamol, and tryptophan, fluorescence studies and luminescent visualization of latent fingerprints

Herein, we report the synthesis of a dual-function azo dye, i.e. thiazole-resorcinol azo (TRA) dye. The synthesized dye, whose structure was confirmed by spectroscopic analysis, was used to modify a carbon paste electrode (thiazole-resorcinol azo dye modified carbon paste electrode, TRA/MCPE) for the simultaneous electrochemical detection of Dopamine (DA), Paracetamol (PA), and Tryptophan (TR). Electrochemical studies revealed a diffusion-controlled oxidation mechanism and good analytical performance. The TRA/MCPE exhibited a linear response from 10 to 80 µM for each analyte, achieving limits of detection (LOD) of 11.05 µM for DA, 9.97 µM for PA, and 4.89 µM for TR. The sensor demonstrated high selectivity, with clear separation of oxidation peaks, alongside satisfactory reproducibility and long-term stability. Furthermore, both UV-Vis absorption and fluorescence emission spectra of TRA were measured in a series of six different solvents to assess the impact of solvent polarity. Fluorescence quantum yields were calculated using the comparative method with Rhodamine B in ethanol as the reference standard. In addition to this, the inherent luminescence of the TRA was successfully employed for forensic applications, enabling the clear visualization of Level I and II ridge details of latent fingerprints via a powder dusting technique. This work showcases a versatile material with significant potential in both electroanalytical sensing and forensic science.