Nathalie Lidgi-Guigui

Soft UV nanoimprint lithography-designed highly sensitive substrates for SERS detection

AbstractWe 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.

Highly sensitive detection of paclitaxel by surface-enhanced Raman scattering

The surface-enhanced Raman scattering (SERS) technique was shown to be an effective molecular analytical tool due to its high sensitivity. Here, we propose to exploit soft UV assisted nanoimprint lithography (UV-NIL) for the development of a reproducible and highly-sensitive SERS biosensor. Soft lithography is known to be advantageous for biological applications since it is compatible with insulating supports and large-area samples. In the present investigations, soft UV-NIL is used for the fabrication of large-sized arrays of gold nanocylinders on glass which were shown to be highly sensitive and highly specific sensing surfaces, with a limit of detection measured down to 1 nM. Employing the UV-NIL SERS substrate enable working ranges of nanomolar to micromolar concentrations in regards to our model paclitaxel analyte.

Diazonium Salt-Based Surface-Enhanced Raman Spectroscopy Nanosensor: Detection and Quantitation of Aromatic Hydrocarbons in Water Samples

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.

Phosphorylation impact on Spleen Tyrosine kinase conformation by Surface Enhanced Raman Spectroscopy.

Spleen Tyrosine Kinase (Syk) plays a crucial role in immune cell signalling and its altered expression or activation are involved in several cancers. Syk activity relies on its phosphorylation status and its multiple phosphorylation sites predict several Syk conformations. In this report, we characterized Syk structural changes according to its phosphorylation/activation status by Surface Enhanced Raman Spectroscopy (SERS). Unphosphorylated/inactive and phosphorylated/active Syk forms were produced into two expression systems with different phosphorylation capability. Syk forms were then analysed by SERS that was carried out in liquid condition on a lithographically designed gold nanocylinders array. Our study demonstrated that SERS signatures of the two Syk forms were drastically distinct, indicating structural modifications related to their phosphorylation status. By comparison with the atomic structure of the unphosphorylated Syk, the SERS peak assignments of the phosphorylated Syk nearest gold nanostructures revealed a differential interaction with the gold surface. We finally described a model for Syk conformational variations according to its phosphorylation status. In conclusion, SERS is an efficient technical approach for studying in vitro protein conformational changes and might be a powerful tool to determine protein functions in tumour cells.

Multi-functionalization of lithographically designed gold nanodisks by plasmon-mediated reduction of aryl diazonium salts

Plasmon-driven surface functionalization of nanoparticles is receiving increasing attention as it allows locally tailored chemical reactivity to be generated on the nanoparticle surface. The extension to surface multi-functionalization still represents a major breakthrough in chemistry. We address this issue by triggering regiospecific surface double-functionalization under plasmon excitation, using diazonium salts as surface functionalization agents.

Tunable Multilayers of Self-Organized Silica Nanospheres by Spin Coating

The coating of fused silica by an organized layer of silica nanospheres (NS) is an important issue for the design of optical and topographic properties especially for lithography techniques such as nanosphere lithography (NSL) or nanosphere photolithography (NSPL). Here, the spin coating of NS dispersed in N,N-dimethylformamide (DMF) is studied. The role of the NS diameter, the spin-coating acceleration, and the volume fraction are the parameters to take into account for the formation and organization of NS in single or double closely packed layers. We propose an explanation for this behavior based on the transition between sedimentation and a viscous regime on the basis of the silica NS organization.