Fabrice Charra

Bio: Fabrice Charra is an academic researcher from Université Paris-Saclay. The author has contributed to research in topics: Scanning tunneling microscope & Plasmon. The author has an hindex of 33, co-authored 179 publications receiving 3785 citations. Previous affiliations of Fabrice Charra include University of Paris-Sud & French Alternative Energies and Atomic Energy Commission.

Light-induced second-harmonic generation in azo-dye polymers.

Abstract: The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry. The microscopic mechanism involves an orientational hole burning followed by orientational redistribution caused by trans-to-cis isomerization of the azo-dye chromophores. The characteristic kinetics of growth and decay of the noncentrosymmetry grating is monitored by second-harmonic generation.

Selective excitation of individual plasmonic hotspots at the tips of single gold nanostars.

Abstract: Plasmonic hotspots in single gold nanostars are located at the tips and can be excited selectively by laser light as evidenced by photoelectron emission microscopy. Selectivity is achieved through wavelength and polarization of the excitation light. Comparing photoelectron emission intensity and dark-field scattering spectra of the same individual nanostars reveals differences in terms of observable plasmon resonance wavelengths and field enhancements. Differences are explained with the underlying near- and far-field processes of the two techniques.

Single-molecule dynamics in a self-assembled 2D molecular sieve.

Abstract: A two-dimensional molecular sieve has been realized. It consists of a host matrix of molecularly engineered building blocks self-assembled at the liquid-solid interface. The simultaneous size- and shape-dependent dynamics of different guest molecules is observed in situ, in real time with submolecular resolution using a scanning tunneling microscope both at the liquid-solid interface and under vacuum. The temperature-dependent dynamics reveals that the diffusion proceeds through thermally activated channeling between single-molecule surface cavities.

Quasi-permanent all-optical encoding of noncentrosymmetry in azo-dye polymers

Abstract: We present an original poling technique that uses a purely optical excitation process. The experiment consists of a seeding-type process. Writing and probing periods are alternated. Writing periods correspond to simultaneous irradiation of the sample by the coherent superposition of the 1064-nm fundamental and the 532-nm second-harmonic light of a picosecond-pulsed Nd:YAG laser. The sample is a spin-coated film of a poly(methyl methacrylate) copolymer onto which the azo-dye molecule Disperse Red 1 is grafted. We demonstrate efficient and quasi-permanent poling of the molecules with a spatial period that satisfies the phase-matching condition for second-harmonic generation. The influence of seeding parameters such as the relative phase and the relative intensities between the writing beams is studied both theoretically and experimentally. Tensorial properties and the spatial profile of the photoinduced χ(2) are analyzed from a microscopic point of view. Dark and photostimulated relaxation processes are investigated from a chemical-physics point of view. The physical origin of the photoinduced molecular orientation process is discussed. A minimal model involving the relevant experimental parameters is developed. Numerical simulations are in agreement with the experiment.

Short range plasmon resonators probed by photoemission electron microscopy.

Abstract: Short range surface plasmon resonators are investigated at the nanometer scale. Gold nanorods (30 nm in diameter) were microfabricated and probed by photoemission electron microscopy under direct laser light excitation. Resonances presenting various numbers of lobes occur for specific rod lengths. A simple analytical model shows that the successive resonant lengths differ by a multiple of one-half of the wavelength of the supported short-range surface plasmon polariton.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

The golden age: gold nanoparticles for biomedicine

Abstract: Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of ‘gilding the (nanomedicinal) lily’, but that a new ‘Golden Age’ of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references).