Surface characterization of thin-film platinum electrodes for biosensors by means of cyclic voltammetry and laser SNMS

Gold foil-based biosensor for the determination of hydrogen peroxide

Hydrogen peroxide ($\text{H}_{\mathbf {2}} \mathbf {O} _{\mathbf {2}}$) plays a critical role in the regulation of multifarious physiological processes. We developed a sensor containing a mercaptopropionic acid (MPA) monolayer covalently immobilized with Horseradish peroxidase (HRP) enzyme for the electrochemical detection of hydrogen peroxide ($\textbf{H}_{\mathbf {2}} \mathbf {O} _{\mathbf {2}}$). A gold foil substrate was chemically treated with nitric acid and were used as working electrode. Platinum wire and Ag-Ag/Cl were used as counter and reference electrodes, respectively. The acid treated gold electrode with the immobilized enzyme shown to have improved catalytic activity in the reduction of $\textbf{H}_{\mathbf {2}} \mathbf {O} _{\mathbf {2}}$. The steady-state current response increases linearly with $\textbf{H}_{\mathbf {2}} \mathbf {O} _{\mathbf {2}}$ concentration from 10 $\mu \textbf{M}$ to 9 mM with a low detection limit of 60 $\mu \textbf{M}$ and showed a sensitivity of 0.4 mA/ mM cm$^{\mathbf {2}}$. This electrochemical sensor is demonstrated to be highly selective and sensitive in the presence of interfering analytes. The improved activity and simple preparation method of the electrode makes the MPAHRP modified gold electrode promising for being developed as an attractive robust material for electrochemical $\textbf{H}_{\mathbf {2}} \mathbf {O} _{\mathbf {2}}$ sensing.

Silver nanoparticle assemblies supported on glassy-carbon electrodes for the electro-analytical detection of hydrogen peroxide

Electrochemical detection of hydrogen peroxide using an edge-plane pyrolytic-graphite electrode (EPPG), a glassy carbon (GC) electrode, and a silver nanoparticle-modified GC electrode is reported. It is shown, in phosphate buffer (0.05 mol L(-1), pH 7.4), that hydrogen peroxide cannot be detected directly on either the EPPG or GC electrodes. However, reduction can be facilitated by modification of the glassy-carbon surface with nanosized silver assemblies. The optimum conditions for modification of the GC electrode with silver nanoparticles were found to be deposition for 1 min at -0.5 V vs. Ag from 5 mmol L(-1) AgNO3/0.1 mol L(-1) TBAP/MeCN, followed by stripping for 2 min at +0.5 V vs. Ag in the same solution. A wave, due to the reduction of hydrogen peroxide on the silver nanoparticles is observed at -0.68 V vs. SCE. The limit of detection for this modified nanosilver electrode was 2.0 x 10(-6) mol L(-1) for hydrogen peroxide in phosphate buffer (0.05 mol L(-1), pH 7.4) with a sensitivity which is five times higher than that observed at a silver macro-electrode. Also observed is a shoulder on the voltammetric wave corresponding to the reduction of oxygen, which is produced by silver-catalysed chemical decomposition of hydrogen peroxide to water and oxygen then oxygen reduction at the surface of the glassy-carbon electrode.