Structure and dynamics of a dl-homocysteine functionalized fullerene-C<inf>60</inf>-gold nanocomposite: A femtomolar l-histidine sensor

A functionalized fullerene-C60-thiol mediated gold nanocomposite was realized using dl-homocysteine as a bifunctional ligand. The nanocomposite was designed by following electronic structure calculations via the DFT formalism. The computed electrostatic potential profile and the electronic HOMO-LUMO energy gap implied enhanced electron transport across the nanocomposite skeleton. Accordingly, synthesis of the nanocomposite proceeded with the hydrophilic fullerene-C60 thiol derivative via in situ reduction of gold(iii), resulting in sterically full gold clusters bound to the fullerene-C60 core. Molecular dynamics simulations with the MM+ force field provided insight into the mode of interaction and direction of electron transfer in the nanocomposite-histidine ensemble. Subsequently, an electrochemical strategy for l-histidine sensing was proposed; the nanocomposite-modified glassy carbon electrode exhibited electrocatalytic activity towards l-histidine sensing, studied via cyclic and square wave voltammetry and impedance spectroscopy. A femtomolar l-histidine sensor, the first of its kind with orders of magnitude enhanced performance in its detection limit, linear range, sensitivity, stability and specificity, and free of interference, thus emerged.