Publications

2018

• Fabrication and study of solar cell modules based on silicon nanowire based radial junction solar cells
  
  • Al Ghzaiwat Mutaz
  , 2018. In this thesis, we have used a low-temperature plasma-enhanced chemical vapor deposition (PECVD) reactor to fabricate Si nanowire radial junction solar mini-modules on 5x5 cm2 glass substrates with the assistance of the laser scribing technique for the series connection of the cells.We have used fluorine-doped tin oxide (FTO) deposited on soda-lime glass substrates (SLG) as a back contact as well as the source of the Sn catalyst which was formed by a direct reduction of FTO using a H2 plasma. Subsequently, p-type SiNWs were grown using plasma-assisted vapor liquid solid (VLS) process, followed by the deposition of intrinsic a-Si:H and n-type µc-SiOx:H layers to achieve pin radial junction solar cells. We have obtained an energy conversion efficiency of 6.3 % with an active area of solar cells of 0.126 cm2, which is to our knowledge, the highest efficiency obtained based on FTO layers as a source of Sn catalyst.Laser scribing was used to perform a selective removal of thin-film materials in order to fabricate minimodules. With laser scribing, a monolithic series connection between adjacent RJ SiNW solar cells on the same glass substrate was achieved. In particular, the laser scribing system has been used to perform selective removal of FTO thin-film and RJ SiNWs, which are commonly known as step P1 and P2, respectively, and to perform a final scribe to isolate the active region from the rest of the substrate. The transparent top ITO contact was sputtered and cell stripes were defined using the lift-off technique (step P3).We have carried out a detailed study of the P2 laser scribe obtained with either green (532 nm) or IR (1064 nm) laser setups. The power of the laser has to be controlled as it has a direct impact on the removal of SiNW RJs and it can damage the underneath FTO contact. We have found that the scribing using a green laser produces a partial melting outside the scribed spots, unlike the IR laser which provides a cleaner scribing and less crystallized material at the edges of scribed spots. Mapping of the scribed spots using Raman spectroscopy allowed analyzing the material composition within the scanned area inside the craters left by the laser pulses. We have demonstrated that the use of the IR laser is preferable for P2 scribing because it can provide a high-quality series connection between cells.Finally, the optimized 10 cm2 SiNW RJ mini-module has reached an energy conversion efficiency of 4.37 % with power generation of 44 mW, thanks to the improved P2 laser scribing and the dense Ag grid printed using the ink-jet method. This performance represents, to the best of our knowledge, the highest reported power generation for silicon nanowire-based solar modules on glass substrates.
• Shape selection through epitaxy of supported platinum nanocrystals
  
  • Peres Laurent
  • Yi Deliang
  • Bustos-Rodriguez Susana
  • Marcelot Cécile
  • Pierrot Alexandre
  • Fazzini Pier-Francesco
  • Florea Ileana
  • Arenal Raul
  • Lacroix Lise-Marie
  • Warot-Fonrose Bénédicte
  • Blon Thomas
  • Soulantika Aikaterini
  Nanoscale, Royal Society of Chemistry, 2018, 10 (48), pp.22730-22736. Supported nanocrystals of original shapes are highly desirable for the development of optimized catalysts; however, conventional methods for the preparation of supported catalysts do not allow shape control. In this work, we have synthesized concave platinum nanocubes exposing {110} crystallographic facets at 20 °C. In the presence of a crystallographically oriented Pt(111) support in the reaction medium, the concave nanocubes grow epitaxially on the support, producing macroscopic nanostructured surfaces. Higher reaction temperature produces a mixture of different nanostructures in solution; however, only the nanostructures growing along the 〈111〉 direction are obtained on the Pt(111) support. Therefore, the oriented surface acts as a template for a selective immobilization of specific nanostructures out of a mixture, which can be regarded as an “epitaxial resolution” of an inhomogeneous mixture of nanocrystals. Thus, a judicious choice of the support crystallographic orientation may allow the isolation of original nanostructures that cannot be obtained in a pure form. (10.1039/x0xx00000x)
  DOI : 10.1039/x0xx00000x
• In situ Photoluminescence Study of Plasma Effects on Passivation of Crystalline Silicon Coated with Aluminum Oxide
  
  • Sreng Mengkoing
  • Silva François
  • Roca I Cabarrocas Pere
  Physica Status Solidi A (applications and materials science), Wiley, 2018, 216 (10), pp.1800612. (10.1002/pssa.201800612)
  DOI : 10.1002/pssa.201800612
• Application d'un imageur polarimétrique multimodal pour l'étude de la réponse optique de milieux et de microstructures diffusantes
  
  • Yoo Thomas
  , 2018. The work carried out during this thesis was aimed to study the interaction of polarized light from the scattering media and particles. This work is part of a strong collaborative context between the LPICM and various private and public laboratories. A wide variety of aspects have been treated deeply, including instrumental development, advanced numerical simulation and the creation of measurement protocols for the interpretation of complex data.The instrumental part of the thesis was devoted to the development of an innovative instrument, suitable for taking polarimetric images at different scales (from millimeters to microns) that can be quickly reconfigured to offer different imaging modes of the same sample. The two main aspects that characterize the instrument are i) the possibility of obtaining real polarimetric images of the sample and the angular distribution of light scattered by an illuminated zone whose size and position can be controlled, ii) the total control of the polarization state, size and divergence of the beams. These two aspects are not united on any other commercial or experimental apparatus today.The first object of the study using the multimodal imaging polarimeter was to study the effect of the thickness from a scattering medium on its optical response. In medical imaging, there is a broad consensus on the benefits of using different polarimetric properties to improve the effectiveness of optical screening techniques for different diseases. Despite these advantages, the interpretation of the polarimetric responses in terms of the physiological properties of tissues has been obscured by the influence of the unknown thickness of the sample.The objective of the work was, therefore, to better understand the dependence of the polarimetric properties of different scattering materials with the known thickness. In conclusion, it is possible to show that the polarimetric properties of the scattering media vary proportionally with the optical path that the light has traveled inside the medium, whereas the degree of polarization depends quadratically on the optical path. This discovery could be used to develop a method of data analysis that overcomes the effect of thickness variations, thus making the measurements very robust and related only to the intrinsic properties of the samples studied.The second object of study was to study the polarimetric responses from particles of micrometric size. The selection of the particles studied by analogy to the size of the cells that form the biological tissues, and which are responsible for the dispersion of light. By means of the polarimetric measurements, it has been discovered that when the microparticles are illuminated with an oblique incidence with respect to the optical axis of the microscope, they appear to behave as if they were optically active. Moreover, it has been found that the value of this apparent optical activity depends on the shape of the particles. The explanation of this phenomenon is based on the appearance of a topological phase of the beam. This topological phase depends on the path of the light scattered inside the microscope. The unprecedented observation of this topological phase has been done by the fact that the multimodal polarimetric imager allows illumination of the samples at the oblique incidence. This discovery can significantly improve the efficiency of optical methods for determining the shape of micro-objects.
• Heteroepitaxial growth of Silicon on GaAs via low temperature plasma-enhanced chemical vapor deposition
  
  • Hamon Guénaëlle
  • Vaissière Nicolas Vaissiere
  • Cariou Romain
  • Chen Wanghua
  • Alvarez J
  • Maurice Jean-Luc
  • Decobert Jean
  • Kleider Jean-Paul
  • Roca I Cabarrocas Pere Roca I Cabarrocas
  , 2018.
• Caractérisation du potentiel de circuit-ouvert d’une cellule solaire Si à jonction radiale PIN en couche mince par la technique de Kelvin Probe Force Microscopy
  
  • Marchat Clément
  • Dai Letian
  • Misra Soumyadeep
  • Jaffré Alexandre
  • Alvarez J
  • Levtchenko Alexandra
  • Le Gall Sylvain
  • Connolly J.P.
  • Foldyna Martin
  • Roca I Cabarrocas Pere Roca I Cabarrocas
  • Kleider Jean-Paul
  , 2018.
• Effects of pulsed electrodeposition parameters on the properties of zinc oxide thin films to improve the photoelectrochemical and photoelectrodegradation efficiency
  
  • Lakhdari Meriem
  • Habelhames Farid
  • Nessark Belkacem
  • Girtan Mihaela
  • Derbal-Habak Hassina
  • Bonnassieux Yvan
  • Tondelier Denis
  • Nunzi Jean Michel
  European Physical Journal: Applied Physics, EDP Sciences, 2018, 84 (3), pp.30102. Zinc oxide (ZnO) thin films were synthesized on ITO glass substrates by electrochemical deposition from a nitrate solution. The deposition potential, bath temperature and annealing temperature were fixed at -1.1 V versus SCE, 80 and 400 degrees C, respectively. Firstly, we prepared the ZnO thin films by two different electrochemical methods: direct (DE) and pulsed electrodeposition (PE). The results indicate that pulse electrodeposition improves the properties of ZnO thin films compared to direct electrodeposition technique. Secondly, we chose the PE method for the elaboration of ZnO thin films and we varied the time-On (t(on)) from 7 to 1 s. Deposited ZnO thin films were characterized using XRD, SEM, optical and photocurrent measurement. X-ray diffraction results indicate that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along the (002) plane perpendicular to the substrate. SEM analysis reveals that the electrodeposited nanosheets at time-On of 7 s are only hexagonal. A remarkable change in ZnO morphology from nanosheets to nanosheets/nanorods and decrease in gap energy is observed with the decrease in electrodeposition time-On. After optimization in electrodeposition time (t(on)), a significant improvement in photocurrent and Methylene Blue (MB) photoelectrocatalytical degradation were observed. (10.1051/epjap/2018180227)
  DOI : 10.1051/epjap/2018180227
• Complementary analysis of Mueller-matrix images of optically anisotropic highly scattering biological tissues
  
  • Borovkova Mariia
  • Peyvasteh Motahareh
  • Dubolazov Olexander
  • Ushenko Yurii
  • Ushenko Volodymyr
  • Bykov Alexander
  • Deby Stanislas
  • Rehbinder Jean
  • Novikova Tatiana
  • Meglinski Igor
  Journal of the European Optical Society : Rapid publications, European Optical Society, 2018, 14 (1).
• Structure and Morphology Control in Thin Films of Conjugated Polymers Prepared by Convective self-Assembly Method
  
  • Yassar Abderrahim
  , 2018. In the past few decades, functional conjugated materials, small-molecules and polymers have emerged as a novel class of materials with useful optoelectronic properties in combination with low-cost solution processing and high flexibility in tailoring their optoelectronic properties to match specific application demands. The morphology and the optoelectronic properties of these materials are influenced by the method of processing. Among the available processing methods, convective self-assembly also known as evaporation-induced self-assembly method, is now an emergent method for the deposition of organic semiconductors. In this talk, we will discuss how the fact that by precisely controlling the deposition parameters mainly, temperature of the substrate, blading speed, surface tension of the solvent, and the surface energy of the substrate, etc., the forces acting at the triple air–substrate–solution interface can be manipulated to create a variety of structured films with different morphologies.
• Plasma Nanotexturing of Silicon for Photovoltaic Applications : Tailoring Plasma-Surface Interactions for Improved Light Management
  
  • Fischer Guillaume
  , 2018. This thesis is dedicated to the study of crystalline silicon (c-Si) surface texturing at the nanoscale (nanotexturing) using capacitively coupled plasma reactive ion etching (CCP-RIE). The general objective consists in tuning the nanotextured surface properties to improve light-management in c-Si solar cells through front surface texturing. To this aim, plasma-surface interactions during etching in a SF6/O2 discharge are investigated using both single-frequency excitation and Tailored Voltage Waveforms (TVWs), i.e. a multifrequency approach triggering electrical asymmetries in the plasma.To gain a full picture of the achievable processing range, the electron heating mechanisms and ion bombardment energy on the surface are first studied. An identification of the dominant electron heating mechanisms in low pressure SF6/O2 plasma is demonstrated using TVWs as an innovative probing tool. Different electrical asymmetry effects are shown to arise depending on the dominant heating mode, which therefore affects both the ion flux and bombardment energy on the etched surface. Although a complete decoupling between ion energy and flux cannot be achieved in the investigated discharge conditions, TVWs do lead to an extended playground for SF6/O2 plasma etching of c-Si surfaces in CCP-RIE.The plasma-surface interaction mechanisms during SF6/O2 plasma etching and texturing of c-Si surfaces are then investigated. A processing window to achieve nanotextured anti-reflective c-Si surfaces (“black silicon”) at room temperature is delimited. Building on the work from the first section, the ion flux and bombardment energy on the c-Si surface are varied independently in this process window. A phenomenological model (etching yield varying with the square root of the ion energy above a threshold around 13 eV) is proposed. From this model, a direct (positive) link between the energy weighted ion fluence and the nanostructure height is identified. Importantly, the final nanostructure average width is shown to also weakly depend on the instantaneous ion flux during the process.Subsequently, anti-reflection and light scattering properties of plasma nanotextured c-Si surfaces are studied. Regarding anti-reflection, when the nanostructure average width is small compared to the wavelength (in c-Si), the nanotextured surface acts as an anti-reflective graded refractive index layer and a direct link between the nanostructure average height and the reflectance can be derived. Very low reflectance (in the order of 2% at normal incidence) on a broad wavelength range (approximately [250, 1000nm]) can be achieved, and the improved anti-reflective properties extend to high angles of incidence. Additionally, strong light scattering is shown to arise when the nanostructure average width overcomes a given threshold determined experimentally. Consequently, light is more efficiently trapped in the c-Si substrate, leading to superior absorption in the range [1000, 1200nm].The aforementioned optical properties of nanotextured c-Si surfaces are of practical interest for improved light management in c-Si photovoltaic devices. However, plasma induced damages (during plasma nanotexturing), as well as enlarged surface area, are responsible for increased carrier recombination. The contribution to recombination from plasma induced defects is shown to be mitigated when ion bombardment energy is kept low. Design rules are consequently proposed: optimized conditions for c-Si nanotexturing in SF6/O2 plasma can be achieved by maximizing the ion flux while keeping ion energy low (but above the etching threshold). These requirements are conflicting in the case of a single frequency CCP discharge, but the trade-off may be (at least partly) resolved using TVWs.
• Mueller polarimetric imaging of biological tissues: classification in a decision-theoretic framework
  
  • Heinrich Christian
  • Rehbinder Jean
  • Nazac André
  • Teig Benjamin
  • Pierangelo Angelo
  • Zallat Jihad
  Journal of the Optical Society of America. A Optics, Image Science, and Vision, Optical Society of America, 2018, 35 (12). Mueller polarimetry is increasingly recognized as a powerful modality in biomedical imaging. Nevertheless, principled statistical analysis procedures are still lacking in this field. This paper presents a complete pipeline for polarimetric bioimages, with an application to ex vivo cervical precancer detection. In the preprocessing stage, we evaluate the replacement of pixels by superpixels. In the analysis stage, we resort to decision theory to select and tune a classifier. Performances of the retained classifier are evaluated. Decision theory provides a rigorous and versatile framework, allowing generalization to other pathologies, to other imaging procedures, and to classification problems involving more than two classes. (10.1364/JOSAA.35.002046)
  DOI : 10.1364/JOSAA.35.002046
• Application of Tip-Enhanced Raman Spectroscopy for the nanoscale characterization of flooded chalk
  
  • Borromeo Laura
  • Toccafondi Chiara
  • Minde Mona Wetrhus
  • Zimmermann Udo
  • Andò Sergio
  • Madland Merete Vadla
  • Korsnes Reidar Inge
  • Ossikovski Razvigor
  Journal of Applied Physics, American Institute of Physics, 2018, 124 (17). One of the most challenging goals of flooded chalk analyses used in Enhanced Oil Recovery (EOR) is to reach high-resolution mineralogical data, in order to detect the composition of new crystals grown after brine injections, with ≤1 μm grain size. Understanding how flooding affects chemical induced compaction, mechanical strength permeability, and porosity is paramount in EOR related investigations. Magnesite formation is the most pervasive process when MgCl2 is injected into chalk, and the submicrometric grain size of the new minerals requires a high performing imaging technique and a new methodological approach: in our study, we present the first attempt of applying Tip-Enhanced Raman Spectroscopy (TERS) to rock and mineral samples. It is a new frontier technique that couples Raman Spectroscopy with Atomic Force Microscopy, allowing impressively high-resolution topography and mineralogical maps. Two long term experiments have been analyzed, where chalk cores were flooded for 718 days and 1072 days, at reservoir conditions comparable to hydrocarbon reservoirs in chalk at the Norwegian continental shelf. Few microns squared areas have been imaged by Atomic Force Microscopy using ultra-polished thin sections. First analyses identified a less pervasive secondary growth of magnesite in the 718 days test and an almost pure magnesite composition in the 1072 days test. Transmission Electron Microscopy (TEM) has been employed to confirm the results of TERS and add dark and bright field grain imaging to the investigations. This confirms the need for high-resolution methodologies such as TERS and TEM to fully understand the EOR effects at submicron-scale. (10.1063/1.5049823)
  DOI : 10.1063/1.5049823
• Impact of aligned carbon nanotubes array on the magnetostatic isolation of closely packed ferromagnetic nanoparticles
  
  • Danilyuk A.L. L
  • Kukharev A.V. V
  • Cojocaru Costel Sorin
  • Le Normand F.
  • Prischepa S.L. L
  Carbon, Elsevier, 2018, 139, pp.1104-1116. We investigate the influence of carbon nanotubes (CNT) aligned array on the magnetic properties of ensemble of densely packed Co nanoparticles (NPs) embedded inside CNT. Each CNT contains only one nanosized Co. Such a special structure was formed by catalyst chemical vapor deposition (CCVD) activated by current discharge plasma and hot filament. The Co NPs, previously deposited onto SiO 2 /Si substrate, acted as a catalyst. By varying the parameters of the CCVD process, we were able to also sputter the substrate instead of CNT growth. Co NPs were used as a mask and the structure of Si-based nano-cones with Co NPs on the top of each cone was formed. Exhaustive investigation of the structural, morphology and crystalline properties of Co nanoparticles were performed. The magnetic properties of two kinds of samples, Co on the Si-based nanocone and Co inside CNT, were differ drastically. In the former case, the magnetic anisotropy of thin-film-type has been observed with large magnetic domains. Whereas for the Co-CNT samples ferromagnetic NPs were magnetically isolated. It was established that the magnetic anisotropy of nanosized Co plays more dominant role than the dipole interaction between Co NPs. The role of the CNT container in this is discussed. (10.1016/j.carbon.2018.08.024)
  DOI : 10.1016/j.carbon.2018.08.024
• Polarimetric measurement utility for pre-cancer detection from uterine cervix specimens
  
  • Kupinski Meredith
  • Boffety Matthieu
  • Goudail François
  • Ossikovski Razvigor
  • Pierangelo Angelo
  • Rehbinder Jean
  • Vizet Jeremy
  • Novikova Tatiana
  Biomedical optics express, Optical Society of America - OSA Publishing, 2018, 9 (11), pp.5691-5702. (10.1364/BOE.9.005691)
  DOI : 10.1364/BOE.9.005691
• Black Phases of CsPbI3: Structural and Theoretical Studies
  
  • Pedesseau Laurent
  • Marronnier Arthur
  • Roma Guido
  • Boyer-Richard Soline
  • Jancu Jean-Marc
  • Bonnassieux Yvan
  • Katan Claudine
  • Stoumpos Constantinos C
  • Kanatzidis Mercouri G
  • Even Jacky
  , 2018. In less than 10 years, hybrid organic-inorganic perovskites have emerged as a new generation of absorber materials for high-efficiency and low-cost solar cells [1], [2]. More recently, fully inorganic perovskite quantum dots (QD) also led to promising efficiencies [3], [4] and then become a serious alternative to hybrid organic-inorganic perovskites. Currently, the record efficiency for QD solar cells is obtained with CsPbI 3. High resolution in-situ synchrotron XRD measurements have been performed on CsPbI 3 as a function of the temperature and revealed a highly anisotropic variation of the lattice parameters. Moreover, CsPbI 3 can be temporarily maintained in a perovskite-like structure down to room temperature, stabilizing a metastable perovskite polytype (black-phase) crucial for photovoltaic applications. Structural, vibrational and electronic properties of the three experimentally observed black phases are further scrutinized using theoretical approaches [5], [6]. A symmetry-based tight-binding model, calibrated with self-consistent GW calculations including spin-orbit coupling, affords further insight into their electronic properties. A Rashba effect is thus predicted for both cubic and tetragonal phases when using the symmetry breaking structures obtained through frozen phonon calculations. (10.29363/nanoge.fallmeeting.2018.218)
  DOI : 10.29363/nanoge.fallmeeting.2018.218
• TADF OLEDs with Circularly Polarized Luminescence
  
  • Feuillastre Sophie
  • Pauton Mathilde
  • Gao L.
  • Desmarchelier Alaric
  • Riives Adrian J.
  • Muller G.
  • Clavier Gilles
  • Tondelier Denis
  • Geffroy Bernard
  • Pieters Grégory
  , 2018. Organic Light-Emitting Diodes (OLEDs) based displays have already entered the mass production market thank to their outstanding properties such as light weight, fast response time, low power consumption and wide color gamut. However, the request in the market continues to grow for lower cost and more efficient devices. Direct emission of circularly polarized light from OLEDs can improve the contrast of the OLED display [1] and simplify device architecture [2]. Circularly polarized luminescence (CPL) emitters represent an important family of molecule, where high syntheses yield, efficient CPL and dissymmetry factors are key challenges [3]. The development of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications is an active area of recent research [4]. TADF emitters are a class of fluorophore that enable harvesting triplet states for fluorescent emission by a reverse intersystem-crossing phenomenon. This allows maximal emission efficiencies, especially in organic electroluminescent devices (OLEDs) that generate 75% triplet exciton. We have recently developed a class of purely organic luminophore that combines CPL with TADF in a simple modular design [5]. This presentation will discuss the concept, preparation, and properties of this new class of molecules and present their application in OLED devices. The importance of the structure-property relationships will be also discussed.
• Conjugated polymers for the elaboration of optical and ohmic sensors for water monitoring
  
  • Wang Xinyang
  , 2018. Different pollutants can be found in water, inorganic material (chloride, chlorine, heavy metal ions…) and organic material (trace of medicament…). Among them, heavy metal ions are of among the most toxic for human and the environment. Analysis of water contaminants that are toxic for human being and aquatic life is of primary importance. Especially, the measurements of the quality of drinking water delivered in private dwelling is a significant public health concern. A family of undesired contaminants is heavy metals. An elevated concentration of metal ions in water is mostly due to an intensive human activity (industry, farming, and housing). In small quantities, certain heavy metals (e.g., iron, copper, manganese, and zinc) are nutritionally essential for a healthy life. However, heavy metals show a great trend to form complexes, especially with ligands of biological matter containing nitrogen, sulfur, and oxygen. As a result, changes in the molecular structure of proteins, breaking of hydrogen bonds, or inhibition of enzymes can occur[1]. These interactions, among others, may explain the toxicological and carcinogenic effects of heavy metals. These ions can cause damages to many organs and are responsible of diseases, including Parkinson’s and Alzheimer’s diseases[2-6]{Liu, 2015 #101;Liu, 2015 #101;Kim, 2012 #102;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101}. Respiratory and cardiac problems can be caused by nickel ingestion[7], and accumulation of the Ni2+ ion in the body leads to oxidative stress[8]; Ni2+ and Cu2+ are also noxious to teeth and bones. These negative effects result from the formation of coordination complexes between the metal ions and biological matter.Heavy metals are not biodegradable and therefore they remain in ecological systems and in the food chain indefinitely, exposing top-level predators to very high levels of pollution.Different methods are used to determine their quantity concentration in aqueous phase such as anodic stripping voltammetry (ASV) [4, 6], solid phase extraction combined with inductively coupled plasma optical emission spectrometry ICP-OES[4, 6] and cold-vapor atomic absorption spectroscopy (AAS) method[9]. These methods are well established, but are costly, time consuming, lack portability, and rely on trained personnel because of their complexity[10].Therefore, cheap, portable and real-time response real-time sensors for the determination of heavy metals in aqueous solutions are needed, particularly in sensitive environments, such as drinking water and industrial wastewater effluents. Here we design and elaborate The aim of the project is to develop these kinds of sensors to satisfy the current need. Two kinds of sensors have been elaborated in the project: the first one is optical sensors based on functionalized conjugated polymers (CPs). The second one is a communicating resistive sensors based on conjugated polymers (CPs)/carbon nanotubes (CNTs) nanohybride for the quick detection of pollutants in aqueous water. To our knowledge, no this kind of resistive of sensors has been developed yet. The start of the project focuses onWe start the project for the detection of metal ions, however, it can later be extended to other kinds of pollutants (such as nitrate, chloride, even drugs) using different polymers with the same working mechanism.
• Growth of In-Plane Ge 1– x Sn x Nanowires with 22 at. % Sn Using a Solid–Liquid–Solid Mechanism
  
  • Azrak Edy
  • Chen Wanghua
  • Moldovan Simona
  • Gao Shiwen
  • Duguay Sébastien
  • Pareige Philippe
  • Roca I Cabarrocas Pere
  Journal of Physical Chemistry C, American Chemical Society, 2018, 122 (45), pp.26236-26242. (10.1021/acs.jpcc.8b07142)
  DOI : 10.1021/acs.jpcc.8b07142
• Atomic Step Flow on a Nanofacet
  
  • Harmand Jean-Christophe
  • Patriarche Gilles
  • Glas Frank
  • Panciera Federico
  • Florea Ileana
  • Maurice Jean-Luc
  • Travers Laurent
  • Ollivier Yannick
  Physical Review Letters, American Physical Society, 2018, 121 (16). (10.1103/PhysRevLett.121.166101)
  DOI : 10.1103/PhysRevLett.121.166101
• Novel Fluorophores based on Regioselective Intramolecular Friedel–Crafts Acylation of the Pyrene Ring Using Triflic Acid
  
  • Jousselin-Oba Tanguy
  • Sbargoud Kamal
  • Vaccaro Giannaro
  • Meinardi Francesco
  • Yassar A.
  • Frigoli Michel
  , 2018.
• Radicals-assisted CVD implemented in a modified HR environmental TEM for in-situ real-time SWCNTs growth with a given chirality
  
  • Florea I.
  • Forel S.
  • Castan A.
  • Catala L.
  • Fossard Frédéric
  • Huc V.
  • Mallah T.
  • Loiseau Annick
  • Cojocaru C.S.
  , 2018. Materials science of carbon nanotubes (CNT) lies at the intersection of various paradigms from fundamental to applied physics and chemistry. Recognizing how the different concepts can be combined together to understand CNT formation still remains a challenge. The synthesis of CNTs with desired chirality and diameter is one of the most important challenges for the nanotubes science and achieving such selectivity requires a good understanding of their growth mechanism. There is an overwhelming body of evidence that catalytic growth is the most promising method for the CNTs synthesis, especially for reaching a chiral selectivity synthesis.[1,2] Although knowledge of the different stages of growth has advanced considerably[3] a full picture is still elusive. Mastering chirality control, however, requires a deeper understanding of the very early stage of CNT nucleation, when the symmetry type is set. A well-controlled synthesis of catalyst nanoparticles (composition, morphology, size) appears to be a mandatory condition for controlling the characteristics of the as-synthesized nanotubes.[4] Recent researches focused especially on the growth of multiwalled CNT[5,6] have shown that the catalyst (re)shaping is correlated with surface energy modification due to C adsorption. To the best of our knowledge previous works have been devoted to the understanding of the relationship between changes in catalyst particle morphology and CNT nucleation [7-11] but more quantitative description is greatly needed for the elaboration of SWCNTs with defined chirality. The aim of the present study is to complement the well-established ex-situ observation of SWCNTs growth [12, 13] with real-time, in-situ TEM observations of the real CVD growth reactions without losing significant resolution. The study presents the development of a unique approach that combines the HRTEM technique, with the implementation of radical-assisted CVD gas sources in a modified environmental transmission electron microscope (ETEM) equipped with a Cs image aberration-corrector. The new set-up, well adapted for carrying out real-time in-situ observations, allows one to keep a higher vacuum within the TEM chamber while bringing gas molecules to the sample, was used to analyze catalyst reshaping and its morphology dynamics during CNT nucleation/growth under controlled conditions. As applied to different new and controlled bimetallic nanoalloy catalysts types, such as CoRu, FeRu and NiRu catalyst [11], the emphasis is to understand the role played by the catalyst and put forward a growth mechanism essential to realized SWCNTs with specific and targeted chirality. In particular, we will discuss the role of the growth temperature and the chemical composition of the catalyst on the final SWCNTs structure.
• Circularly polarized images with contrast reversal using pseudo-chiral metasurfaces
  
  • Yoo Thomas Sang Hyuk
  • Berthelot Johann
  • Guida Géraldine
  • Demaille Dominique
  • Garcia-Caurel Enric
  • Bonod Nicolas
  • Gallas Bruno
  ACS photonics, American Chemical Society, 2018, 5 (10), pp.4068 - 4073. Anticounterfeiting technologies rely on visual effects that are specific to particular structures and concealed to the unwary observer. Plasmonic nanostructures are one solution to these two requirements, and besides colored effects, the possibility to design covert images in a particular polarization state of light is particularly appealing. The generation of circular polarization provides a new degree of freedom, and the use of pseudochiral plasmonic resonators hosting magnetoelectric resonances allows tailoring opposite handedness of circular polarization within the same nanostructure. In this work, we have defined a palette of luminance observable only in circular dichroism by engineering the shapes and positions of the resonators. The spatial control of the polarization state of light is highlighted by realizing a micrometer-scale image revealed only in circular polarization with an additional contrast reversal associated with circular dichroism reversal. (10.1021/acsphotonics.8b00730)
  DOI : 10.1021/acsphotonics.8b00730
• TEM/STEM characterizations of NixPt1-x nano-alloys
  
  • Moreira da Silva Cora
  • Girard Armelle
  • Fossard Frederic
  • Huc Vincent
  • Florea Ileana
  • Loiseau Annick
  , 2009, 131. A wide-range of potential applications uses nanoparticles (NPs) as catalysts and requires precise control of their structure and composition. Therefore, in order to obtain NPs with well-defined structural parameters, we did a colloid chemistry synthesis. This technique is a robust method for preparing monodisperse alloyed NPs with control over size and shape and homogeneous compositions. NixPt1-x NPs were synthesized using platinum (II) acetylacetonate and nickel (II) acetylacetonate reduced by 1,2-hexadecandiol in organic solvent with surfactants (oleylamine and oleic acid). Generally, this method gives core-shell structures 1-3 NPs as shown on Figure 1a to 1c because of the significant difference between Ni2+/Ni (-0.253 V) and Pt2+/Pt (+1.18 V) reduction potentials. Nonetheless, this problem was solved by strict control of the synthesis temperature. Reaction was modulated to obtain Ni3Pt, NiPt and NiPt3 uniformly alloyed NPs. This synthesis gave spherical or icosahedral crystalline nanoparticles with a narrow distribution size (Table 1). Conventional and HRSTEM images (CM20 - FEI, Libra 200 FE-Zeiss, Titan G2 Cs-corrected - FEI operating at 200kV) of the NPs show lattice fringes with inter-fringe measured corresponding to {111} or {200} planes of Ni-Pt alloy in a disordered face-centered cubic (FCC) structure. Lattice parameters (obtained by electron diffraction) plot as a function of the concentration of atoms in NixPt1-x NPs, presents a Vegard's law like bulk alloys (Figure 2). Local Energy Dispersive X-ray (EDX) measurements with STEM in chemical mapping mode, operating at 200kV, (Table1), determined NixPt1-x nanoparticles composition. EDX cartographies confirm a homogeneous repartition of nickel and platinum concentration into nanoparticles (Figure 1). In order to carry out NPs behavior for high temperature catalytic applications, we have also performed in-situ transmission electron microscopy techniques (modified FEI - TITAN Cs-corrected ETEM), operating at 300kV, with atomic-resolution. We investigated the nanostructure - diameter and crystalline - evolution in a [25 °C - 900 °C] temperature range. The particles remain crystalline up to 800°C. When the temperature increases up to 900°C, only the core of NPs is still ordered. A statistical study was performed on the NPs size. A 1 nm fluctuation was detected on the projected diameters during temperature increase, easily lighten by drift and/or rotation of icosahedral shaped particles (Figure 3). Furthermore, from 150°C, small, close, spherical particles can coalesce. To conclude, Ni3Pt, NiPt, NiPt3 alloyed nanoparticles with a similar diameter were synthesized by colloidal route with a very good reproducibility. An analysis of sizes, aggregation states, the chemical compositions, the lattice parameters and temperature behaviors were performed thanks to the wide range of possible techniques offered by Transmission Electron Microscopy.
• Comparing TEM and resonant Raman spectroscopy for diameter distribution assessment of single wall carbon nanotubes
  
  • Castan Alice
  • Forel S.
  • Fossard Frederic
  • Ghedjatti A.
  • Cojocaru Costel Sorin
  • Huc Vincent
  • Loiseau Annick
  , 2006, 677. Characterization of single wall carbon nanotube (SWCNT) population plays a key role to study the influence of growth parameters during their formation. Despite this crucial step, statistical data extracted from more than one characterization technique are rarely compared in publications claiming for SWCNT growth selectivity. Transmission Electron Microscopy and Raman spectroscopy are widely used to obtain an accurate measurement of the SWCNT diameters [1]. We used both techniques and observed a systematic shift between the diameter distributions assessed by Raman spectroscopy and TEM imaging in our typical SWCNT samples, CVD grown on SiO2/Si wafers (Figure 1)[2]. TEM image analyses were performed on samples transferred on TEM grids using the methodology we proposed in [3] whereas Raman spectra are recorded on the as grown samples and tube diameters were deduced from their radial breathing mode by following a procedure widely used in the literature [4]. Observed shift can be as high as 0.4 nm, which represents 20 to 30 % of the diameter values while measurement accuracy is estimated to be equal to 0.05 nm for both techniques. Furthermore, small tube diameters below 1.2 nm seem to be under-detected by TEM with respect to Raman whereas the opposite trend is observed for tube diameters larger than 1.5 nm. In this work, we explore the comparison between TEM imaging and Raman spectroscopy capabilities for determining the diameter distribution of a CVD grown sample, in an effort to validate, or invalidate, currently used methodologies.
• Optimization of the optical coupling in nanowire-based integrated photonic platforms by FDTD simulation
  
  • Guan Nan
  • Babichev Andrey
  • Foldyna Martin
  • Denisov Dmitry
  • Julien François
  • Tchernycheva Maria
  Beilstein Journal of Nanotechnology, Karlsruhe Institute of Technology., 2018, 9, pp.2248 - 2254. (10.3762/bjnano.9.209)
  DOI : 10.3762/bjnano.9.209