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Long range self-organisations of small metallic nanocrystals for SERS detection of electrochemical reactions

Abstract : Gold electrodes were modified by silver and gold nanocrystals (NCs) that self-organize onto the surface. Their optical properties were explored by measuring electroreflectance spectra as a function of electrode potential. Below their oxidation potential, no shift of the reflectance maximum was observed for Ag NCs. This can be explained by a low inter-facial capacitance resulting from the impossibility for the electrolyte to penetrate into the hydrophobic layer created by the NCs dodecanethiol ligands. Conversely, a non-monotonous evolution was observed with the electrode potential for oleylamine capped Au NCs. This behavior is suggesting a less dense hydrophobic layer, allowing significant electrolyte penetration. Next, electroactive compounds were adsorbed on the the Au NCs assemblies and characterized by Raman spectroelectrochemistry. In the first system displaying a single electron transfer with no coupled chemical reaction, only the spectrum intensity changed, because oxidation generated a Raman resonant radical cation. The second study considered 4-nitrothiophenol, for which up to 6 electrons and 6 protons may be transferred. In this case, the nitro band disappeared upon reduction, and the spectrum displayed typical features of the formed 4-aminothiophenol.
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Submitted on : Wednesday, September 30, 2020 - 6:09:35 PM
Last modification on : Monday, October 5, 2020 - 5:42:58 PM

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Sihem Groni, Claire Fave, Bernd Schöllhorn, Lionel Chapus, Pierre Aubertin, et al.. Long range self-organisations of small metallic nanocrystals for SERS detection of electrochemical reactions. Journal of Electroanalytical Chemistry, Elsevier 2020, 872, pp., 114322. ⟨10.1016/j.jelechem.2020.114322⟩. ⟨hal-02954128⟩

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