In this paper, we present the development of a highly sensitive, specific and reproducible nanobiosensor to detect one specific liver cancer biomarker, the manganese super oxide dismutase (MnSOD). The high sensitivity and reproducibility was reached by using SERS on gold nanostructures (nanocylinders and coupled nanorods) produced by electron-beam lithography (EBL). The specificity of the detection was provided by the use of a specific aptamer with high affinity to the targeted protein as a recognition element. With such a sensor, we have been able to observe the SERS signal of the MnSOD at concentrations down to the nM level and to show with negative control that this detection is specific due to the use of the aptamer. This latter issue has allowed us to detect the MnSOD in different body fluids (serum and saliva) at concentrations in the nM range. We have then demonstrated the effectiveness of our SERS nanobiosensor using aptamer as a bioreceptor for the detection of disease biomarker at low concentration and in complex fluids.

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

We report on the use of soft UV nanoimprint lithography (UV-NIL) for the development of reproducible, millimeter-sized, and sensitive substrates for SERS detection. The used geometry for plasmonic nanostructures is the cylinder. Gold nanocylinders (GNCs) showed to be very sensitive and specific sensing surfaces. Indeed, we demonstrated that less than 4 ×106 avidin molecules were detected and contributed to the surface-enhanced Raman scattering (SERS) signal. Thus, the soft UV-NIL technique allows to obtain quickly very sensitive substrates for SERS biosensing on surfaces of 1 mm 2.

International audienceOptimum amplification in surface enhanced Raman scattering (SERS) from individual nanoantennas is expected when the excitation is slightly blue-shifted with respect to the localized surface plasmon resonance (LSPR), so that the LSPR peak falls in the middle between the laser and the Stokes Raman emission. Recent experiments have shown when moving the excitation from the visible to the near-infrared that this rule of thumb is no more valid. The excitation has to be red-shifted with respect to the LSPR peak, up to 80 nm, to obtain highest SERS. Such discrepancy is usually attributed to a near-field (NF) to far-field (FF) spectral shift. Here we critically discuss this hypothesis for the case of gold nanocylinders. By combining multiwavelength-excitation SERS experiments with numerical calculations, we show that the red-shift of the excitation energy does not originate from a spectral shift between the extinction (FF) and the near-field distribution (NF), which is found to be not larger than 10 nm. Rather, it can be accounted for by looking at the peculiar spectral dependence of the near-field intensity on the cylinders diameter, characterized by an initial increase, up to 180 nm diameter, followed by a decrease and a pronounced skewness

Plasmon-mediated multi-functionalization of nanoparticles is presented, in order to achieve the grafting of various chemical groups in distinct nanoscale regions.

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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.

Here, we present a surface-enhanced Raman spectroscopy (SERS) nanosensor for environmental pollutants detection. This study was conducted on three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BaP), fluoranthene (FL), and naphthalene (NAP). SERS substrates were chemically functionalized using 4-dodecyl benzenediazonium-tetrafluoroborate and SERS analyses were conducted to detect the pollutants alone and in mixtures. Compounds were first measured in water-methanol (9:1 volume ratio) samples. Investigation on solutions containing concentrations ranging from 10−6 g L−1 to 10−3 g L−1 provided data to plot calibration curves and to determine the performance of the sensor. The calculated limit of detection (LOD) was 0.026 mg L−1 (10−7 mol L−1) for BaP, 0.064 mg L−1 (3.2 × 10−7 mol L−1) for FL, and 3.94 mg L−1 (3.1 × 10−5 mol L−1) for NAP, respectively. The correlation between the calculated LOD values and the octanol-water partition coefficient (Kow) of the investigated PAHs suggests that the developed nanosensor is particularly suitable for detecting highly non-polar PAH compounds. Measurements conducted on a mixture of the three analytes (i) demonstrated the ability of the developed technology to detect and identify the three analytes in the mixture; (ii) provided the exact quantitation of pollutants in a mixture. Moreover, we optimized the surface regeneration step for the nanosensor.