Common mechanism for helical nanotube formation by anodic polymerization and by cathodic deposition using helical pores on silicon electrodes

We report that platinum-assisted chemical etching formed self-organized helical pores in silicon substrates can be utilized as platforms for the electrochemical production of nanohelices of conducting polymers (polypyrrole) and metals (gold). Surprisingly, the nanohelices thus created are tubes although the polymerization and deposition were carried out by anodic and cathodic reactions, respectively. Based on our results, we propose a common mechanism for the formation of tubular nanohelices by both anodic polymerization and cathodic deposition through the accumulation of reactants in microporous silicon which covers the wall surface of the helical pores

Narcissistic self-sorting of n-acene nano-ribbons yielding energy-transfer and electroluminescence at p-n junctions

The 2,3-didecyloxy derivative of an n-type anthracene (n-BG) and a p-type tetracene (p-R) have been synthesized and their self-assembly into nano-ribbons studied. Hyperspectral fluorescence imaging revealed their narcissistic self-sorting, leading to separated nanoribbons emitting with very different colors (blue or green for n-BG, depending on the growth solvent, and red for p-R). It is unique that the usual origins of self-sorting, such as specific H-bonding, different growth kinetics, or incompatible steric hindrance can be ruled out. Hence, the narcissistic behaviour is herein proposed to originate from a sofar unconsidered cause: the discrepancy between the quadrupolar character of n-BG and dipolar character of p-R. At the p-n junctions of these nanoribbons, inter-ribbon FRET and electro-luminescence switch-on were observed by fluorescence/luminescence microscopy.The authors acknowledge the financial support of the European Research Council Marie Curie Actions (FP7-PEOPLE-2012-ITN SMARTNET Grant agreement Nr 316656); the CNRS; the French Ministry of Education and Research; the Region Aquitaine; the ANR-06-JCJC-0030; the Department of Education, Science and Universities of the Basque Country Government (postdoctoral grant and project IT1639-22); the "Arina" informatic cluster of UPV/EHU; the facilities ELORGA of UB; and the ANR-17-CE24-0033-01 RESOLVE. The authors thank Dr A. Mendez-Ardoy for the CV measurements and CESAMO for structural analyses (ISM, Univ. Bordeaux)

Narcissistic Self-Sorting of n-Acene Nano-Ribbons yielding Energy-Transfer and Electroluminescence at p-n Junctions

The 2,3-didecyloxy-derivative of an n-type anthracene (n-BG) and a p-type tetracene (p-R) have been synthesized and their self-assembly into nano-ribbons studied. Hyperspectral fluorescence imaging revealed their narcissistic self-sorting, leading to separated nanoribbons emitting with very different colors (blue or green for n-BG, depending on the growth solvent, and red for p-R). It is unique that the usual origins of self-sorting, such as specific H-bonding, different growth kinetics, or incompatible steric hindrance can be ruled out. Hence, the narcissistic behaviour is herein proposed to originate from a sofar unconsidered cause: the discrepancy between the quadrupolar character of n-BG and dipolar character of p-R. At the pn-junctions of these nanoribbons, inter-ribbon FRET and electro-luminescence switch-on were observed by fluorescence microscopy.Modulation of Organic Optic Information InterfacesFabrication Supramoléculaire de Dispositifs OLED Haute Résolution par voie ImprimableSoft Materials Advanced Research Training Networ

Narcissistic self-sorting of n-acene nano-ribbons yielding energy-transfer and electroluminescence at p–n junctions

The 2,3-didecyloxy derivative of an n-type anthracene (n-BG) and a p-type tetracene (p-R) have been synthesized and their self-assembly into nano-ribbons studied. Hyperspectral fluorescence imaging revealed their narcissistic self-sorting, leading to separated nanoribbons emitting with very different colors (blue or green for n-BG, depending on the growth solvent, and red for p-R). It is unique that the usual origins of self-sorting, such as specific H-bonding, different growth kinetics, or incompatible steric hindrance can be ruled out. Hence, the narcissistic behaviour is herein proposed to originate from a so-far unconsidered cause: the discrepancy between the quadrupolar character of n-BG and dipolar character of p-R. At the p–n junctions of these nanoribbons, inter-ribbon FRET and electro-luminescence switch-on were observed by fluorescence/luminescence microscopy.Fabrication Supramoléculaire de Dispositifs OLED Haute Résolution par voie ImprimableModulation of Organic Optic Information Interface

Exploiting Direct and Cascade Energy Transfer for Color-Tunable and White-Light Emission in Three-Component Self-Assembled Nanofibers

The co-self-assembly of a blue-light emitting organogelator and specifically designed green and red emitting hosts yields light-harvesting nanofibers with tunable emissive properties. In particular, under near-UV excitation white-light emission is achieved in organogels and their constituting nanofibers as demonstrated by confocal fluorescence microspectroscopy. Steady-state and time-resolved emission spectroscopies reveal that color tuning in three component nanofibers is achieved exploiting excitation energy transfers occurring between the blue-emitting anthracene derivative and the green- and red-emitting tetracenes, whereas the latter emission is further sensitized through a cascade blue-to-green-to-red transfer sequence. Moreover, excitation energy migrates through the blue-emitting components by exciton hopping before being transferred to the acceptors, thus contributing to the light-harvesting process

Formation and growth of labyrinthine drying patterns in 2-D porous media

International audienceEvaporation of binary solutions confined in a 2D porous medium leads to the formation of labyrinthine patterns. We here demonstrate that the formation of these unusual out of equilibrium patterns occurs through a regular succession of bursts of individual meniscii. We identify the elementary mechanisms leading to the formation of crystal deposits at the pore scale and then establish a pore-network model that well captures the topology of the labyrinthine structures observed in our experiments as well as their dynamics. Using simple arguments, we predict topological changesin the drying pattern at the scale of an individual pore as the geometrical parameters of the problem and the contact angle are varied. Experiments confirm these predictions

Collisional excitation of NH by H2: Potential energy surface and scattering calculations

International audienceCollisional data for the excitation of NH by H2 are key to accurately derive the NH abundance in astrophysical media. We present a new four-dimensional potential energy surface (PES) for the NH-H2 van der Waals complex. The ab initio calculations of the PES were carried out using the explicitly correlated partially spin-restricted coupled cluster method with single, double, and perturbative triple excitations [RCCSD(T)-F12a] with the augmented correlation-consistent polarized valence triple zeta basis set. The PES was represented by an angular expansion in terms of coupled spherical harmonics. The global minimum corresponds to the linear structure with a well depth De = 149.10 cm−1. The calculated dissociation energy D0 is found to be 30.55 and 22.11 cm−1 for ortho-H2 and para-H2 complexes, respectively. These results are in agreement with the experimental values. Then, we perform quantum close-coupling calculations of the fine structure resolved excitation cross sections of NH induced by collisions with ortho-H2 and para-H2 for collisional energies up to 500 cm−1. We find strong differences between collisions induced by ortho-H2 and para-H2. Propensity rules are discussed. The cross sections are larger for fine structure conserving transitions than for fine structure changing ones, as predicted by theory. These new results should help in interpreting NH interstellar spectra and better constrain the abundance of NH in interstellar molecular clouds. © 2021 Author(s)

Order-Disorder Structural Transitions in Mazes Built by Evaporating Drops

International audienceWe show that the evaporation of surfactant solutions confined in quasi-two-dimensional porous media creates micron-sized labyrinthine patterns composing the walls of a centimeter-sized maze. These walls are made of solid deposits formed during drying via a sequence of individual Haines jumps occurring at the pore scale. We rationalize this process driven by simple iterative rules with a cellular automaton that acts as a maze generator. This model well describes the formation dynamics and final structure of an experimental maze as functions of the wettability heterogeneities of a porous medium and its geometry. Also, our findings unveil the crucial role of two geometric dimensionless quantities that control the structural order of a maze

Facile functionalization of a fully fluorescent perfluorophenyl BODIPY: photostable thiol and amine conjugates

Selective nucleophilic substitution on a perfluorophenyl unit comprising a BODIPY fluorophore using an alkanethiol or a primary amine offers a quantitative fluorophore labelling strategy, while retaining high photostability and emission quantum yields approaching unity.Communication between Functional Molecules using Photocontrolled Ion

Étude théorique des collisions entre NH et H2 dans le milieu interstellaire

National audienc