Advanced Large-Scale Nanofabrication Route for Ultrasensitive SERS Platforms Based on Precisely Shaped Gold Nanostructures

One of the key issues for SERS-based trace applications is engineering structurally uniform substrates with ultrasensitivity, stability, and good reproducibility. A label-free, cost-effective, and reproducible fabrication strategy of ultrasensitive SERS sensors was reported in this work. Herein, we present recent progress in self-assembly-based synthesis to elaborate precisely shaped and abundant gold nanoparticles in a large area. We demonstrated that shape control is driven by the selective adsorption of a cation (Na+, K+, and H+) on a single facet of gold nanocrystal seeds during the growth process. We studied SERS features as a function of morphology. Importantly, we found a correlation between the shape and experimental SERS enhancement factors. We observed a detection threshold of 10−20 M of bipyridine ethylene (BPE), which matches the lowest value determined in literature for BPE until now. Such novel sensing finding could be very promising for diseases and pathogen detection and opens up an avenue toward predicting which other morphologies could offer improved sensitivity

Study of the mechanism of complex coacervation between beta-lactoglobulin and the major fractions of acacia gum - comparaison with the unfractionnated acacia gum

La coacervation complexe, une séparation de phase associative principalement induite par des interactions électrostatiques, entre la B-lactoglobuline (BLG, protéine animale) et la gomme d’Acacia (AG, polysaccharide végétal) a été étudiée dans ce travail. La plus grande difficulté pour comprendre la coacervation complexe au niveau moléculaire entre BLG et AG révèle être la polymolécularité élevée d’AG. A partir de là, la motivation principale de cette thèse était de comprendre et contrôler les interactions entre la BLG et les fractions moléculaires d’AG, FI (~88% d’AG) et FII (~10% d’AG) en utilisant la titration calorimétrique isotherme, la diffusion statique et dynamique de lumière, la mobilité électrophorétique, la Granulo-Polarimétrie et la microscopie optique. Une énergie d’interaction plus forte, une stoechiométrie d’association plus faible et ainsi une complexation favorable ont étés montrées entre la BLG et FII en relation avec l’accessibilité et la densité de charges plus élevées de FII. Les résultats majeurs de cette étude ont ainsi montré des rôles différents des fractions de l’AG dans la coacervation complexe avec la BLGThe complex coacervation mechanism, an associative phase separation mainly induced by electrostatic interactions, between ?-lactoglobulin (BLG, animal protein) and Acacia gum (AG, vegetal polysaccharide) was studied in this work. The most significant difficulty to understand complex coacervation between BLG and AG at the molecular level is the molecular weight polydispersity of AG. From there, the main motivation of this research was to better understand and control the interactions between BLG and the major molecular fractions of AG, FI (~88% of AG) and FII (~10% of AG) using isothermal titration calorimetry, static and dynamic light scattering, electrophoretic mobility, Granulo-Polarimetry and optical microscopy. Higher energy of interaction, lower stoichiometry of association and then favorable complexation were shown between BLG and FII in relation with higher accessibility and density of charges for FII. The major results of this study reveal then different roles of AG fractions in complex coacervation with BL

Etude du mécanisme de coacervation complexe<br />entre les fractions principales de la gomme<br />d'Acacia et la β-lactoglobuline - Comparaison avec<br />la gomme d'Acacia non fractionnée

The complex coacervation mechanism, an associative phase separation mainly induced by electrostatic interactions, between β-lactoglobulin (BLG, animal protein) and Acacia gum (AG, vegetal polysaccharide) was studied in this work.The complex coacervation mechanism, an associative phase separation mainly induced by electrostatic interactions, between ß-lactoglobulin (BLG, animal protein) and Acacia gum (AG, vegetal polysaccharide) was studied in this work. The most significant difficulty to understand complex coacervation between BLG and AG at the molecular level is the molecular weight polydispersity of AG. From there, the main motivation of this research was to better understand and control the interactions between BLG and the major molecular fractions of AG, FI (~88% of AG) and FII(~10% of AG) using isothermal titration calorimetry, static and dynamic light scattering, electrophoretic mobility, Granulo-Polarimetry and optical microscopy. Higher energy of interaction, lower stoichiometry of association and then favorable complexation were shown between BLG and FII in relation with higher accessibility and density of charges for FII. The major results of this study reveal then different roles of AG fractions in complex coacervation with BLG.La coacervation complexe, une séparation de phase associative principalement induite par des interactions électrostatiques, entre la ß-lactoglobuline (BLG, protéine animale) et la gomme d'Acacia (AG, polysaccharide végétal) a été étudiée dans ce travail. La plus grande difficulté pour comprendre la coacervation complexe au niveau moléculaire entre BLG et AG révèle être la polymolécularité élevée d'AG. A partir de là, la motivation principale de cette thèse était de comprendre et contrôler les interactions entre la BLG et les fractions moléculaires d'AG, FI (~88% d'AG) et FII (~10% d'AG) en utilisant la titration calorimétrique isotherme, la diffusion statique et dynamique de lumière, la mobilité électrophorétique, la Granulo- Polarimétrie et la microscopie optique. Une énergie d'interaction plus forte, une stoechiométrie d'association plus faible et ainsi une complexation favorable ont étés montrées entre la BLG et FII en relation avec l'accessibilité et la densité de charges plus élevées de FII. Les résultats majeurs de cette étude ont ainsi montré des rôles différents des fractions de l'AG dans la coacervation complexe avec la BLG

Etude du mécanisme de coacervation complexe entre les fractions principales de la gomme d'Acacia et la [beta]-lactoglobuline - Comparaison avec la gomme d'Acacia non fractionnée

The complex coacervation mechanism, an associative phase separation mainly induced by electrostatic interactions, between - lactoglobulin (BLG, animal protein) and Acacia gum (AG, vegetal polysaccharide) was studied in this work. The most significant difficulty to understand complex coacervation between BLG and AG at the molecular level is the molecular weight polydispersity of AG. From there, the main motivation of this research was to better understand and control the interactions between BLG and the major molecular fractions of AG, FI (~88% of AG) and FII (~10% of AG) using isothermal titration calorimetry, static and dynamic light scattering, electrophoretic mobility, Granulo-Polarimetry and optical microscopy. Higher energy of interaction, lower stoichiometry of association and then favorable complexation were shown between BLG and FII in relation with higher accessibility and density of charges for FII. The major results of this study reveal then different roles of AG fractions in complex coacervation with BLGLa coacervation complexe, une séparation de phase associative principalement induite par des interactions électrostatiques, entre la B-lactoglobuline (BLG, protéine animale) et la gomme d'Acacia (AG, polysaccharide végétal) a été étudiée dans ce travail. La plus grande difficulté pour comprendre la coacervation complexe au niveau moléculaire entre BLG et AG révèle être la polymolécularité élevée d'AG. A partir de là, la motivation principale de cette thèse était de comprendre et contrôler les interactions entre la BLG et les fractions moléculaires d'AG, FI (~88% d'AG) et FII (~10% d'AG) en utilisant la titration calorimétrique isotherme, la diffusion statique et dynamique de lumière, la mobilité électrophorétique, la Granulo-Polarimétrie et la microscopie optique. Une énergie d'interaction plus forte, une stoechiométrie d'association plus faible et ainsi une complexation favorable ont étés montrées entre la BLG et FII en relation avec l'accessibilité et la densité de charges plus élevées de FII. Les résultats majeurs de cette étude ont ainsi montré des rôles différents des fractions de l'AG dans la coacervation complexe avec la BL

3D structuring of polymers at sub-wavelength scales by direct laser writing

International audienc

3D structuring of polymers and metals at sub-wavelength scales by direct laser writing for photonic and sensing applications

International audienc

Fabrication of true 3D polymer nanostructures with sub-100 nm feature sizes via femtosecond direct laser writing based on two-photon polymerization

International audienceIn this work, we demonstrate the capability to fabricate three-dimensional (3D) structures with 75 nm resolution using direct laser writing (DLW) based on two-photon polymerization. The composition of the photopolymerizable solution was tuned in order to show a strong chemical non-linearity effect by adding free radical inhibitors. The influence of the inhibitor concentration, laser power and scan speed on the resolution of as-prepared structures is also investigated. It is observed that, with the optimized inhibitor-containing formulation, the resolution is significantly improved as the scan speed increased (400 µm/s)

Highly sensitive plasmonic nanosensors for biomedical applications

International audienceMetallic nanomaterials exhibiting distinct surface-plasmon-resonance effects have gained increasing attention over the past few years due to their broad applications in photonics, biological imaging, drug delivery, sensing and surface enhanced Raman spectroscopy (SERS). One of the main drivers for the development of plasmonic materials is the desire to improve the sensitivity of SERS for exploring structure and reaction pathways at surfaces as well as for sensing. The development of nanofabrication methodologies for tailoring both particle shape and size has been intensified recently, giving special attention to the preparation of noble metal nanoparticles (Cu, Ag, Pt, Pd, and Au). Over a wide range of studies, the challenge is to develop metallic substrates combining high sensitivity, reproducibility, stability and easy of preparation. The sensing feature of MNPs results from their collective charge density oscillations and is known as localized surface plasmon resonance (LSPR). In recent studies, we reported a new method of fabrication of MNPS based on the self-assembly of metallic precursor-loaded homopolymer dispersion. Then, the deposition of this dispersion on a given substrate (glass, silicon, functionalized surface, etc.) allows the formation of highly sensitive nano-objects particularly relevant for sensing and SERS. Herein we report a facile way to detect few biomolecules (picomol) using highly sensitive silver nanoparticles. In the present communication, we investigate the physico-chemical mechanism of formation of MNPs in order to tune their physical and optical properties, which is essential for sensing applications. We particularly highlight the possibility to measure few molecules of bacteria

Nouvelle approche d'étude des propriétés thermiques de nanoparticules métalliques

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3D structuring of polymers and metals at sub-wavelength scales by direct laser writing for photonic and sensing applications

International audienceFabrication of three-dimensional (3D) nanostructures has received increasing attention due to their potential application in many exemplified areas of research such as Photonics (photonic crystals, metamaterials, photonic ring resonators, diffractive optics), Micro Optics (micro optical devices, integrated optics), Micro Fluidics (lab-on-a-chip systems, development of substances, analysis), Life Sciences (extra cellular matrices, stem cell differentiation, cell growth studies, tissue engineering) and Nano- and Microtechnology. So far, the fabrication of three-dimensional structures with feature sizes far beyond the diffraction limit of the applied laser wavelength is a great challenge in photolithography and associated fields. In that context, we investigate physical approaches (near field illumination, Two Photon Absorption,…) coupled to chemical non-linearity effects in order to confine the matter/light interaction volume. In this paper, we show that nanostructures (polymers, metals or hybrid materials) could be fabricated by laser assisted photochemical routes with sub-100 nm feature sizes (lambda/18)