Size-dependence enhancement in electrocatalytic activity of NiHCF-gold nanocomposite: potential application in electrochemical sensing

A nanocomposite of nickel hexacyanoferrate (NiHCF) was made with gold nanoparticles (AuNPs) of two different sizes (20 and 80 nm as AuNP(red) and AuNP(blue) respectively), synthesized via 3-glycidoxypropyltrimethoxysilane mediated reduction of 3-aminopropyltrimethoxysilane treated gold chloride and characterized by scanning electron microscopy and UV-VIS spectroscopy. The size of AuNPs was found to influence the two pairs of reversible voltammetric peaks of cation rich and cation deficient NiHCF. Such influence was identified from cyclic voltammetry of nanocomposite modified electrodes and applications during electrochemical sensing of two different analytes hydrazine and glutathione (GSH). Electrochemical sensing of hydrazine was based on cyclic voltammetry and differential pulse voltammetry (DPV) found as a function of sodium deficient NiHCF and was greatly amplified with increasing AuNPs nanogeometry. NiHCF alone is not an efficient electrode material for GSH analysis at the level required, however, the presence of AuNPs introduces size dependent sensitive and selective detection of GSH. GSH sensing based on linear sweep voltammetry (LSV) was found to be mediated by the potassium rich form of NiHCF redox couple in the presence of AuNPs. The results justified electrochemical detection of these analytes based on a mediated mechanism and support the role of AuNPs for facilitated electrochemical activity of NiHCF based systems as a function of nanogeometry.