On-chip electrochemical microsystems for measurements of copper and conductivity in artificial seawater.

The fabrication and characterisation of microelectrochemical sensors for Cu(2+) and conductivity suitable for operation in the marine environment are presented. The impact of the designs on sensor performance and their adequacy to operate in real conditions are discussed. The sensors, tailored to voltammetric and impedimetric measurements, are fabricated on silicon using photolithographic and thin film deposition techniques. The impedimetric sensor is made of Pt interdigitated electrodes which are used for the measurement of conductivity. The voltammetric sensors are based on a three electrode electrochemical cell with on-chip Ag|AgCl reference and Pt counter and working electrodes, used for detection of copper by underpotential deposition-stripping voltammetry at microelectrode array. The sensors operated in the Cu(2+) concentrations ranging from 0.48 to 3.97 µM with a limit of detection of 0.115 µM. The impact of the temperature, the pH and the salinity of the artificial seawater on the sensitivity for Cu(2+) detection are also considered. Measurements of copper concentration and conductivity are validated using certified reference materials and standard solutions.

Synthesis of conducting transparent few-layer graphene directly on glass at 450 °C.

Post-growth transfer and high growth temperature are two major hurdles that research has to overcome to get graphene out of research laboratories. Here, using a plasma-enhanced chemical vapour deposition process, we demonstrate the large-area formation of continuous transparent graphene layers at temperatures as low as 450 °C. Our few-layer graphene grows at the interface between a pre-deposited 200 nm Ni catalytic film and an insulating glass substrate. After nickel etching, we are able to measure the optical transmittance of the layers without any transfer. We also measure their sheet resistance directly and after inkjet printing of electrical contacts: sheet resistance is locally as low as 500 Ω sq⁻¹. Finally the samples equipped with printed contacts appear to be efficient humidity sensors.

Interactions of proteins with small ionised molecules: electrochemical adsorption and facilitated ion transfer voltammetry of haemoglobin at the liquid/liquid interface.

The interaction of proteins with interfaces and surfaces provides a basis for studying their behaviour and methods to detect them. This paper is concerned with elucidation of the mechanism of electrochemical detection of haemoglobin (Hb) at the interface between aqueous and organic electrolyte solutions. The adsorption of Hb at the interface was investigated by alternating current (AC) voltammetry. It was found that addition of Hb to the aqueous phase induced a shift of the potential of zero charge at the liquid/liquid interface, due to interfacial adsorption of Hb. The influence of the nature and the concentration of the organic phase electrolyte on the electrochemical signal was investigated by cyclic voltammetry (CV). It was found that the electrochemical signal, in the presence of aqueous phase Hb, was due to the facilitated transfer of the anion of the organic phase electrolyte to the aqueous phase. The transfer current was dependent on both the nature and concentration of the organic phase electrolyte anion. These results confirm that adsorbed Hb molecules at the liquid/liquid interface interact with small ionised molecules and facilitate their transfer across the interface. The results will provide a basis for both biomolecular detection methods and for the study of protein-small ionised molecule interactions.