Stable free radicals TEMPO (2,2,6,6-tetramethyl-1-piperidine-1-oxyl) and its derivatives have been widely employed as spin labels [1], spin traps [2] and antioxidants [3] in the biomedical field, as mediator in „living” free radical polymerization [4], and as catalysts in aerobic oxidation processes [5]. The TEMPO radicals can also interact with gold electrode surface or gold nanoparticles and create the Au-NO bonding[6, 7].     

Nanoparticles modified with single–component TEMPO-Thiol monolayer and mixed monolayers composed of bis[2-(4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl)ethyl] disulfide (TEMPO-DiSS) and alkanethiols (with four or twelve methylene groups) were synthesized[8]. Electrochemical behavior of the three types of NPs was studied, and their diffusion coefficients in solution and surfaces coverages were determined. We found that the interaction between gold and TEMPO nitroxyl radicals may be useful as a method of binding gold nanoparticles to gold electrode surfaces.The nanoparticles were adsorbed on bare gold electrodes, and on the TEMPO-Thiol (Rys. A), or 1,9-nonanedithiol (Fig. B) modified gold electrode. Using cyclic voltammetry (CV), scanning tunneling microscopy (STM) and infrared spectroscopy (IR), we could compare the properties of the gold nitroxyl radical interaction with the well known gold- sulfur bonding.

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