Beyond common analytical limits of radicals detection using the functional SERS substrates

In this work, we present the novel analytical procedure for the detection of the radicals in the analytical solutions with an unprecedented detection limit and versatility. The proposed procedure is based on the grafting of stable 2,2,6,6-Tetramethylpiperidin-1-yeoxyl (TEMPO) radical to the surface of the SERS-active gold grating. The presence of radicals in the analytical solution induces the conversion of grafted TEMPO to N-oxoammonium salt accompanied by the appropriate peak shifts in SERS spectra. Observed changes of SERS spectra makes possible to detect the presence of radicals down to 10(-10) M concentration, far exceeding the sensitivity of common analytical methods. Proposed highly regular plasmonic background providing homogeneous distribution of electric field enhancement together with used surface decoration procedure ensuring uniform distribution of grafted TEMPO molecules, result in perfect SERS results reproducibility. Finally, the regeneration of SERS substrate was also demonstrated which is essential for repeated use of created SERS chips in radical's detection.