Electrochemical Characterization of Gold-Nanostructured Platinum Substrates and Application to Determination of Hg(II) at Trace Levels

Objectives: To develop gold nanostructure on Pt substrate for detection of Hg(II) in environment by DPASV technique. Its structure was characterized by SEM and electrochemical performance was evaluated. The fabricated electrodes were used to measure Hg(II) samples in a concentration range from 2 to 100 ppb. Method: Gold nanoparticles (AuNPs) and AuNDs were deposited on platinum substrates by applying potential of +0.50 V for AuNPs deposition and galvanostatic of -50 mA for AuNDs/Pt in a solution 20 mM HAuCl4, 10 mM KI, 5 mM NH4Cl and 0.5 M H2SO4.The electrochemical behaviors of AuNPs/Pt and AuNDs/Pt were examined using CV in 5 mM K3[Fe(CN)6]/0.1 M PBS solution, pH = 7 and the detection of Hg(II) was performed by DPASV. Results: The SEM images show that largest surface area was obtained at 120 s depositing time. Effective surface areas (ESA) of AuNPs and AuNDs are about 1.39 and 5.19 times higher than electrode geometric area. Calibration curves achieved with R2= 0.9978; 0.9975; 0.9973 and LOD= 0.55; 0.105 and 0.042 ppb for Au disk, AuNPs/Pt and AuNDs/Pt respectively. Reproducibility with ten measurements of 10, 40 and 80 ppb of Hg(II), RSD (%) were 3.5, 2.8 and 1.5 respectively. No significant effect on Hg(II) signals was found except CCu(II) with 100 times higher than CHg(II). Comparison with AAS, data difference between the two techniques is acceptable, at only 4.34%. Conclusion: LOD for Hg(II) detection by AuNDs/Pt achieved 0.042 ppb with linear range of 2.0–100 ppb. Combining with a laboratory constructed galvano-potentiostat, it can be used in on-site measurement.