Johan Grand
University of Paris
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Publication
Featured researches published by Johan Grand.
Nano Letters | 2011
Eric C. Le Ru; Johan Grand; Idrissa Sow; Walter R. C. Somerville; P. G. Etchegoin; Gaëlle Charron; Nordin Félidj; G. Lévi; J. Aubard
Surface-enhanced Raman spectroscopy (SERS) is now a well-established technique for the detection, under appropriate conditions, of single molecules (SM) adsorbed on metallic nanostructures. However, because of the large variations of the SERS enhancement factor on the surface, only molecules located at the positions of highest enhancement, so-called hot-spots, can be detected at the single-molecule level. As a result, in all SM-SERS studies so far only a small fraction, typically less than 1%, of molecules are actually observed. This complicates the analysis of such experiments and means that trace detection via SERS can in principle still be vastly improved. Here we propose a simple scheme, based on selective adsorption of the target analyte at the SERS hot-spots only, that allows in principle detection of every single target molecule in solution. We moreover provide a general experimental methodology, based on the comparison between average and maximum (single molecule) SERS enhancement factors, to verify the efficiency of our approach. The concepts and tools introduced in this work can readily be applied to other SERS systems aiming for detection of every single target molecule.
Advanced Materials | 2012
Delphine Coursault; Johan Grand; Bruno Zappone; Habib Ayeb; G. Lévi; Nordin Félidj; Emmanuelle Lacaze
In the presence of oriented smectic liquid crystal defects, hybrid systems of nanoparticles/liquid crystals form straight chains of nanoparticles of length longer than tens of micrometers and width equal to one single nanoparticle. The interparticle distance in a chain can be varied between a few micrometers and 1.5 nm, highlighting the control of optical absorption by light polarization monitored by gold nanoparticle concentration.
Applied Physics Letters | 2007
C. Hubert; L. Billot; Pierre-Michel Adam; Renaud Bachelot; Pascal Royer; Johan Grand; D. Gindre; Kokou D. Dorkenoo; Alain Fort
The role of surface plasmon in second harmonic generation from arrays of gold nanorod particles excited by femtosecond laser pulses is investigated as a function of incident light polarization and irradiation wavelength. In addition to photoluminescence, a peak of second harmonic is observed and is found to depend on the polarization and wavelength of the fundamental frequency laser beam. In particular, the authors found similarities between extinction spectra of the nanoparticles and spectra of emmitted second harmonic. This behavior can be explained by resonant excitation of localized surface plasmon resonances.
Journal of the American Chemical Society | 2010
Verena Stockhausen; Pascal Martin; Jalal Ghilane; Yann R. Leroux; Hyacinthe Randriamahazaka; Johan Grand; Nordin Félidj; Jean Christophe Lacroix
Herein, we report the variation of localized surface plasmon resonance (LSPR) of gold nanoparticle (NP) arrays covered by poly(3,4-ethylenedioxythiophene) (PEDOT) as a function of the electronic state of the polymer. Giant shifts and fine-tuning of the LSPR of gold NPs surrounded by PEDOT/sodium docecyl sulfate have been achieved. The color variations of plasmonic/conducting polymer (CP) devices are given not only by changes of the optical properties of the CP upon doping but also by a close synergy of the optical properties of CP and NP. Such systems can considerably extend the field of CP-based electrochromic devices.
Synthetic Metals | 2003
Johan Grand; Sergei Kostcheev; Jean-Louis Bijeon; M. Lamy de la Chapelle; Pierre-Michel Adam; Rumyantseva A; Gilles Lerondel; Pascal Royer
As a first step towards near-field Raman, we chose to study surface enhanced Raman scattering (SERS)-active substrates to cope with the weakness of Raman scattering (small cross-section and low concentration). We concentrated our work on localized surface plasmon (LSP) since they turned out to play a great part in SERS and we put forward the relation between LSP resonance and Raman enhancement. Roughness of our samples is controlled either by annealing process or electron-beam lithography (EBL); this latter technique proved to best suit to our study. Substrates are characterized by extinction spectroscopy which determines the LSP resonance and then Raman spectrum of a probe molecule, trans-1,2-bis(4-pyridyl)ethylene (BPE) is recorded. We show that maximum of enhancement is obtained when the LSP resonance is red-shifted (50 nm) compared to the excitation laser line (632.8 nm).
Applied Physics Letters | 2008
M. Zavelani-Rossi; Michele Celebrano; Paolo Biagioni; Dario Polli; Marco Finazzi; L. Duò; Giulio Cerullo; M. Labardi; M. Allegrini; Johan Grand; Pierre-Michel Adam
Second-harmonic generation from single gold elliptical nanoparticles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). The near-field nonlinear response is found to be directly related to local surface plasmon resonances and to particle morphology. The combined analysis of linear and second-harmonic SNOM images provides discrimination among different light extinction particle behaviors, not achievable just with linear techniques. The polarization state of the emitted second harmonic is also investigated, providing experimental evidence of second-harmonic particle emission modes peculiar to near-field excitation.
Chemical Communications | 2011
E. C. Le Ru; Stefan Meyer; Camille G. Artur; P. G. Etchegoin; Johan Grand; P. Lang; François Maurel
We have measured the polarization and incident angle dependence of the Surface-Enhanced Raman Scattering (SERS) signal of a nile blue monolayer adsorbed on a flat gold surface. Comparisons with predictions of electromagnetic (EM) theory indicate that the molecules are predominantly adsorbed flat on the surface. These results provide the most direct demonstration of the concept of surface selection rules in SERS, and further confirm the validity of the SERS-EM model beyond the |E|(4)-approximation.
Journal of Chemical Physics | 2008
Nordin Félidj; Johan Grand; G. Laurent; J. Aubard; G. Lévi; Andreas Hohenau; N. Galler; F. R. Aussenegg; Joachim R. Krenn
In this paper, we report on the observation of multipolar surface plasmon excitation in lithographically designed gold nanotriangles, investigated by means of far-field extinction microspectroscopy in the wavelength range of 400-1000 nm. Several bands are observed in the visible and near infrared regions when increasing the side length of the triangles. The assignment of these peaks to successive in-plane multipolar plasmon modes is supported by calculations using the discrete dipole approximation method. We show that the lowest three multipolar excitations are clearly resolved in the visible and near infrared range. These new spectral features could be very promising in nanooptics or for chemosensing and biosensing applications.
Nano Letters | 2009
Yann R. Leroux; Jean Christophe Lacroix; Claire Fave; Verena Stockhausen; Nordin Félidj; Johan Grand; Andreas Hohenau; Joachim R. Krenn
Control of the optical properties of metallic nanoparticles (NP) is realized using an electrochemical switch consisting of a thin layer of conducting polymer (CP). It is shown that the quenching of localized surface plasmon (LSP) sustained by oblate particles depends of the frequency of the LSP resonance. This effect is attributed to the variation of the CP dielectric function with wavelength. As a consequence, prolate arrays show total quenching of the LSP resonance along the major axis of the particles whereas modulation and moderate damping are observed along the minor axis. Combining electroactive conducting polymer and prolate NP makes it possible to design active plasmonic devices with anisotropic optical response upon CP switching. In the present case, such devices can be used as active filters or polarizers.
Journal of Physical Chemistry C | 2013
I. Sow; Johan Grand; G. Lévi; J. Aubard; Nordin Félidj; Jean-Claude Tinguely; Andreas Hohenau; Joachim R. Krenn
In this article, we investigate the Surface-Enhanced Raman Scattering (SERS) efficiency of methylene blue (MB) molecules deposited on gold nanostripes which, due to their fabrication by electron beam lithography and thermal evaporation, present various degrees of crystallinity and nanoscale surface roughness (NSR). By comparing gold nanostructures with different degrees of roughness and crystallinity, we show that the NSR has a strong effect on the SERS intensity of MB probe molecules. In particular, the NSR features of the lithographic structures significantly enhance the Raman signal of MB molecules, even when the excitation wavelength lies far from the localized surface plasmon resonance (LSPR) of the stripes. These results are in very good agreement with numerical calculations of the SERS gain obtained using the discrete dipole approximation (DDA). The influence of NSR on the optical near-field response of lithographic structures thus appears crucial since they are widely used in the context of nano-optics or/and molecular sensing.