Spirally oriented Au microelectrode array sensor for detection of Hg (II)

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.

Graphene FET Array Biosensor Based on ssDNA Aptamer for Ultrasensitive Hg2+ Detection in Environmental Pollutants

Invisible mercury ion is an extremely poisonous environmental pollutant, therefore, a fast and highly sensitive detection method is of significant importance. In this study, a liquid-gated graphene field-effect transistor (GFET) array biosensor (6 × 6 GFETs on the chip) was fabricated and applied for Hg²⁺ quantitate detection based on single-stranded DNA (ssDNA) aptamer. The biosensor showed outstanding selectivity to Hg²⁺ in mixed solutions containing various metal ions. Moreover, the sensing capability of the biosensor was demonstrated by real-time responses and showed a fairly low detection limit of 40 pM, a wide detection ranged from 100 pM to 100 nM and rapid response time below one second. These results suggest that the GFET array biosensor based on ssDNA aptamer offers a simple fabrication procedure and quite fast method for mercury ion contaminant detection and are promising for various analytical applications.

Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection

The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.