Comparative study of Pd-, Au-, and Cu-based nanostructured electrodes synthesized in deep eutectic solvents: linking nucleation mechanisms to electrochemical DNA sensing performance.

This work presents a systematic comparison of the nucleation mechanisms of Pd, Au, and Cu in deep eutectic solvents and their direct effect on electrochemical DNA sensing performance. Chronoamperometric analysis revealed progressive nucleation for Cu, mixed nucleation for Au, and instantaneous nucleation for Pd. The distinct nucleation behaviors significantly influenced the surface morphology and electrochemical characteristics of the deposited electrodes. Accordingly, the sensitivities of Cu-, Au-, and Pd-based sensors were determined to be 80.48, 163.35, and 318.54 µA nM-1 cm-2, respectively, and the corresponding limits of detection (LOD) were 1.97 × 10-12 M, 1.17 × 10-12 M, and 0.73 × 10-12 M. All sensors exhibited a wide linear detection range from 1.0 × 10-12 to 3.0 × 10-10 M, excellent reproducibility (RSD < 3.2%), good stability, and high selectivity toward complementary DNA sequences. Practical applicability was validated through the detection of PCR-amplified DNA extracted from the sputum samples of patients with tuberculosis, showing satisfactory recovery and reliability in complex biological matrices.