Electrodeposited Ni-Fe onto Glassy Carbon for the Detection of Methylene Blue

A composite electrode composed of electrodeposited, nickel-iron nanostructured clusters onto a glassy carbon (GC) disk electrode was used as a working electrode to detect methylene blue at concentrations below 10 μM. The Ni-Fe clusters were prepared by pulse electrodeposition and a lateral composition variation was observed reflective of a local pH change across the Ni-Fe feature. The applied potential for the detection of MB at a pH of 4 was determined through voltammetry and demonstrated using chronoamperometry and electrochemical impedance spectroscopy (EIS) where the adsorption of MB influenced both the capacitance, C, and ohmic resistance, Rs. A peak present in it1/2 vs t chronoamperometry plots decreased with lower MB bulk concentration, while in contrast, the RsC parameters determined from equivalent circuit models of EIS had the opposite behavior having a larger signal with lower MB concentration, and hence providing a way to increase the detection signal at lower MB concentration.

Influence of Bath Hydrodynamics on the Micromechanical Properties of Electrodeposited Nickel-Cobalt Alloys

The influence of bath hydrodynamics on the resultant micromechanical properties of electrodeposited nickel-cobalt alloy system is investigated. The bath hydrodynamics realized by magnetic stirring is simulated using COMSOL Multiphysics and a region of minimum variation in velocity within the electrolytic cell is determined and validated experimentally. Nickel-cobalt alloy and nickel coating samples are deposited galvanostatically (50 mA/cm2) with varying bath velocity (0 to 42 cm/s). The surface morphology of samples gradually changed from granular (fractal dimension 2.97) to more planar (fractal dimension 2.15) growth type, and the according average roughness decreased from 207.5 nm to 11 nm on increasing the electrolyte velocity from 0 to 42 cm/s for nickel-cobalt alloys; a similar trend was also found in the case of nickel coatings. The calculated grain size from the X-ray diffractograms decreased from 31 nm to 12 nm and from 69 nm to 26 nm as function of increasing velocity (up to 42 cm/s) for nickel-cobalt and nickel coatings, respectively. Consecutively, the measured Vickers microhardness values increased by 43% (i.e., from 393 HV0.01 to 692 HV0.01) and by 33% (i.e., from 255 HV0.01 to 381 HV0.01) for nickel-cobalt and nickel coatings, respectively, which fits well with the Hall–Petch relation.