International audienceGold nanostructures (GNS) were chemically functionalized using four different diazonium salts: benzene-diazonium-tetrafluoroborate (DS), 4-decylbenzene-diazonium-tetrafluoroborate (DS-C10H21), 4-carboxybenzene-diazonium-tetrafluoroborate (DS-COOH), and 4-(aminoethyl)-benzene-diazonium-tetrafluoroborate (DS-(CH2)2NH2). Effective chemical grafting on GNS was shown by surface-enhanced Raman spectroscopy (SERS); aromatic ring deformations in the range of 1570–1591 cm–1 are of particular interest. The very strong band observed around 1075 cm–1, related to CH in-plane bending for mono- and para-substituted benzenes (coupled with ring-N stretching mode), provided further irrefutable evidence of the grafting. SERS enhancement of these two bands ascertains the perpendicular orientation of the aromatic rings on the GNS. X-ray photoelectron spectroscopy (XPS) analyses of chemically grafted flat gold surfaces suggest azophenyl radical pathways when using DS, DS-(CH2)2-NH2, or DS-C10H21. It was shown that coating at the interface is the result of a Au–N covalent bond; growth of the layers is via N═N. These XPS results agree with those provided by SERS without excluding the aryl radical pathways. For DS-COOH, the results provided by SERS, XPS, and density functional theory calculations show (i) effective chemical grafting of the GNS via a covalent bond between gold and carboxylate forms and (ii) growth via multilayers in the meta position between aromatic rings through either N═N or C–C bonds

Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised "click" reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the "click" chemistry.

The aim of this work is to measure the temperature variations by analyzing the plasmon signature on a metallic surface that is periodically structured and immersed in a liquid. A change in the temperature of the sample surface induces a modification of the local refractive index leading to a shift of the surface plasmon resonance (SPR) frequency due to the strong interaction between the evanescent electric field and the metallic surface. The experimental set-up used in this study to detect the refractive index changes is based on a metallic grating permitting a direct excitation of a plasmon wave, leading to a high sensibility, high-temperature range and contactless sensor within a very compact and simple device. The experimental set-up demonstrated that SPR could be used as a non-invasive, high-resolution temperature measurement method for metallic surfaces.