Hybrid Metal-Dielectric Plasmonic Zero Mode Waveguide for Enhanced Single Molecule Detection

We fabricated hybrid metal-dielectric nanoantennas and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence measurements. We characterized the fluorescence enhancement, as well as the lifetime and detection volume reduction for each wavelength. We observe that the hybrid metal-dielectric nanoantennas behave as enhanced Zero Mode Waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of microM. However, a wavelength blue-shift of 40 nm dramatically decreases the performance of the nanoantennas. We compared their behavior with that of a golden ZMW, and we verified that the dielectric silicon layer improves the design. We interpreted the experimental observations with the help of numerical simulations. In addition, the simulations showed that the field enhancement of the structure highly depends on the incoming beam: tightly focused beams yield lower field enhancements than plane-waves

E-Beam Patterned Gold Nanodot Arrays on Optical Fiber Tips for Localized Surface Plasmon Resonance Biochemical Sensing

Electron beam lithography (EBL) was used to directly pattern periodic gold nanodot arrays on optical fiber tips. Localized surface plasmon resonance of the E-beam patterned gold nanodot arrays on optical fiber tips was utilized for biochemical sensing. The advantage of the optical fiber based localized surface plasmon resonance (LSPR) sensors is the convenience to work with and work in harsh environments. An optical fiber tip LSPR refractive index sensor of 196 nm per refractive index unit (RIU) sensitivity has been demonstrated. The affinity sensing property of the fiber tip sensor was demonstrated using biotin/streptavidin as the receptor/analyte. The detection limit for streptavidin was determined to be 6 pM

A graphical method for performance mapping of machines and milling tools

Optimal design of the machining setup in terms of installed machines, cutting tools and process parameters is of paramount importance for every manufacturing company. In most of the metal cutting companies, all choices related to machine eligibility and cutting parameters selection typically come from heuristic approaches and follow supplier indications or base on the skill of experienced machine operators. More advanced solutions, such as model-based and virtual approaches, are adopted less frequently mainly due to the lack of these techniques in grasping the underlying knowledge successfully. Aim of this work is to introduce a synthetic graphical representation of machining centers and cutting tools capabilities, to provide an accessible way to evaluate the feasibility and close-to-limit conditions of the cutting process. Taking inspiration from previous scientific works from the measurement engineering field, a set of 2D and 3D graphs are presented to map machine, tools and process capabilities, as well as their obtainable manufacturing performances and expectable tool life. This approach synthesizes the nominal data coming from different sources (catalogues, database, tool model geometries etc.) and the real cutting tools parameters used during the production phase. Some examples are provided to show the potential of this graphical evaluation in supporting process planning and decision-making and in formalizing the machining setup knowledge. Further developments are devoted to extend the method to other manufacturing processes, including hybrid processes. At the same time, an in-process data gathering software will be integrated for building a solid database that can be used by an autonomous multi-technological process selector, as well as by a pre-process condition advisor in an Industry 4.0 oriented way

Localised detection of thiophenol with gold nanotriangles highly structured as honeycombs by nonlinear sum frequency generation spectroscopy

International audienceGold nanotriangles structured as honeycombs and fabricated by nanosphere lithography on a gold film are functionalized by thiophenol molecules in order to be used as plasmonic sensors in nonlinear optical sum-frequency generation (SFG) spectroscopy. The monitoring and the characterization of the surface optical properties are performed by UV-Visible differential reflectance spectroscopy showing an absorbance maximum located at 540 nm for p-and s-polarisation beams. SFG spectroscopy proves to be effective for thiophenol detection in ssp-polarisation scheme while the molecular SFG signal disappears in ppp-configuration due to the strong s-d interband contribution of gold. However, in ssp-configuration, the vibration modes of thiophe-nol molecules at 3050 and 3071 cm −1 are yet observed thanks to the excitation of a transversal plasmon mode by the incident visible laser beam, whereas they are usually very difficult to distinguish by Surface Enhanced Raman Scattering (SERS) and other vibrational optical probes

Localised detection of thiophenol with gold nanotriangles highly structured as honeycombs by nonlinear sum frequency generation spectroscopy

International audienceGold nanotriangles structured as honeycombs and fabricated by nanosphere lithography on a gold film are functionalised by thiophenol molecules in order to be used as plasmonic sensors in nonlinear optical sum frequency generation (SFG) spectroscopy. The monitoring and the characterisation of the surface optical properties are performed by UV-visible differential reflectance spec-troscopy showing an absorbance maximum located at 540 nm for p-and s-polarisation beams. SFG spectroscopy proves to be effective for thiophenol detection in ssp-polarisation scheme, while the molecular SFG signal disappears in ppp-configuration due to the strong s-d interband contribution of gold. However, in ssp-configuration, the vibration modes of thiophenol molecules at 3050 and 3071 cm À1 are yet observed thanks to the excitation of a transversal plasmon mode by the incident visible laser beam, whereas they are usually very difficult to distinguish by surface-enhanced Raman scattering and other vibra-tional optical probes

Two examples of nanostructured gold surfaces as biosensors. Surface-enhanced chemiluminescence and double detection by surface plasmon resonance and luminescence

International audienceIn this paper, we present a review of our activities in the field of gold biosensors. Nanostructured gold surfaces can be used in biology for their plasmonic and/or catalytic properties. In a first part, we show how the gold plasmonic properties allow the detection of the biotin-streptavidin binding by two types of techniques: extinction spectroscopy and also luminescence spectroscopy when the probe (here the streptavidin) is labelled by polysiloxane particles encapsulating fluorophores. In a second part, we demonstrate that the catalytical properties of gold corrugated surfaces can significantly enhance the chemiluminescence of luminol brought at vicinity. We found that the surface-enhancement induced by gold is two times of magnitude greater than that induced by silver

Detection in near-field domain of biomolecules adsorbed on a single metallic nanoparticle

In this paper, we study the performances of nanosensors based on Localized Surface Plasmon Resonance in the context of biological sensing. We demonstrate the sensitivity and the selectivity of our designed nanosensors by studying the influence of the concentration of Streptavidin on the shift of Localized Surface Plasmon Resonance wavelength. In addition, to study the detection of biomolecules on a single Au nanoparticle, we used a Scanning Near‐field Optical Microscope. These results represent new steps for applications in biological research and medical diagnostics