Carboxylic-acid functionalized molecules can be immobilized into the surface of a glassy carbon electrode through a multi-step surface modification procedure in which nitrobenzene diazonium tetrafluoroborate is electrochemically grafted to the electrode surface and the NO2terminus subsequently converted to an NH2group that can readily be coupled via carbodiimide crosslinking. This surface modification has potential applications in the development of new electrochemical DNA biosensors when modification attest to be attainable and readily managed. The aim of this study was to investigate the effects of changing the concentration of nitrobenzene diazonium tetra fluoroborate for the duration of the initial electrochemical grafting step on the surface density of the surface modification. To achieve aim, the diazonium modified glassy carbon surface was exposed to carboxylic-acid functionalized anthraquinone, the presence of which at the electrode is established by cyclic voltammetry and the magnitude of the signal record employed for the estimation the surface density of grafted molecules. Results from the study revealed that diazonium reduction can be used to prepare surface densities of anthraquinone on a glassy carbon electrode at circa1×1012molecules per cm2, a value that is comparable to the surface densities of DNA probes used in current state-of the art electrochemical DNA biosensors on gold electrodes
