Tunable electrochemistry of gold-silver alloy nanoshells
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The widespread and increasing interest in enhancing biosensing technologies by increasing their sensitivities and lowering their costs has led to the exploration and application of complex nanomaterials as signal transducers and enhancers. In this work, the electrochemical properties of monodispersed AuAg alloy nanoshells (NSs) with finely tunable morphology, composition, and size are studied to assess their potential as electroactive labels. The controlled corrosion of their silver content, caused by the oxidizing character of dissolved oxygen and chlorides of the electrolyte, allows the generation of a reproducible electrochemical signal that is easily measurable through voltammetric techniques. Remarkably, the underpotential deposition of dissolved Ag+ catalyzed on AuAg NS surfaces is observed and its dependence on the nanoparticle morphology, size, and elemental composition is studied, revealing a strong correlation between the relative amounts of the two metals. The highest catalytic activity is found at Au/Ag ratios higher than ≈ 10, showing how the synergy between both metals is necessary to trigger the enhancement of Ag+ reduction. The ability of AuAg NSs to generate an electrocatalytic current without the need for any strong acid makes them an extremely promising material for biosensing applications.
KeywordsAu nanoshells nanoparticles surface chemistry underpotential deposition
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This work was carried out within the “Doctorat en Quìmica” PhD programme of Universitat Autònoma de Barcelona, supported by the Spanish MINECO (No. MAT2015-70725-R) and from the Catalan Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) (No. 2017-SGR-143). Financial support from the HISENTS (685817) Project financed by the European Community under H20202 Capacities Programme is gratefully acknowledged. It was also funded by the CERCA Program/Generalitat de Catalunya. ICN2 acknowledges the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV2201320295.
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