Structural and electrochemical characterization of novel leucine–gold nanoparticles modified electrode

Abstract

A novel modified electrode was designed and fabricated by linking l-Leucine capped gold nanoparticles to 1,3-propanedithiol self-assembled monolayer (SAM), on gold substrate. Using UV-Vis and FT-IR spectroscopy, we have shown that l-Leucine molecules functionalize the gold nanoparticles. Morphological characteristics of capped nanoparticles before and after linking to SAM were evidenced by TEM and tapping™ mode AFM. The properties of the nanostructured assembly were tested for detection of Cu(II) ions, by employing cyclic voltammetry as investigation techniques. A detection limit of 5.4×10−7M was obtained in this case. The results were compared with those obtained for bare gold electrode or modified by citrate-capped gold nanoparticles.Additionally, Electrochemical Impedance Spectroscopy was used to further characterize the electrode modified with l-Leucine capped gold nanoparticles. An equivalent electrical circuit was developed to interpret and fit the experimental EIS data. The circuit contains the solution resistance (Rs), the charge-transfer resistance (Rct), the Warburg impedance (ZWt – transmissive boundary) and a constant phase element (CPE) that models the behavior of the double-layer capacitance. The charge-transfer resistance was found to vary with Cu(II) concentration within 10−5 to 10−3M concentration range; a saturation tendency was observed at higher concentrations.