Rational Design of Push–Pull Fluorene Dyes: Synthesis and Structure–Photophysics Relationship

Our work surveyed experimental and theoretical investigations to construct highly emissive D –π–A (D=donor, A=acceptor) fluorenes. The synthetic routes were optimised to be concise and gram‐scalable. The molecular design was first rationalised by varying the electron‐withdrawing group from an aldehyde, ketotriazole or succinyl to methylenemalonitrile or benzothiadiazole. The electron‐donating group was next varied from aliphatic or aromatic amines to saturated cyclic amines ranging from aziridine to azepane. Spectroscopic studies correlated with TD‐DFT calculations provided the optimised structures. The selected push–pull dyes exhibited visible absorptions, significant brightness, important solvatofluorochromism, mega‐Stokes shifts (>250 nm) and dramatic shifts in emission to the near‐infrared. The current library includes the comprehensive characterization of 16 prospective dyes for fluorescence applications. Among them, several fluorene derivatives bearing different conjugation anchors were tested for coupling and demonstrated to preserve the photophysical responses once further bound.     

Columnar Liquid‐Crystalline Dibenzopentacenodithiophenes by Photocyclization

The twofold glyoxylic Perkin reaction of perylene‐3,9‐diglyoxylic acid with thiophene‐diacetic acid followed by oxidative photocylization and reaction with α‐branched primary alkylamines yields columnar liquid‐crystalline diimides with two sulfur atoms in the condensed arene system. A broad temperature range of the hexagonal columnar mesophase is induced by racemic doubly branched alkyl chains. The HOMO and LUMO energy levels of these thiophene‐derived diimides qualify them as electron donors with respect to perylene diimides.     

Engineered inorganic core/shell nanoparticles

It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed.     

Calculations of fine-structure resolved collisional rate coefficients for the NH(X3Σ-)-He system

We present fine-structure-resolved collisional rate coefficients for the NH(X(3)Σ(-))-He van der Waals complex. The calculations are based on the state-of-the-art potential energy surface [Cybulski et al., J. Chem. Phys. 122, 094307 (2005)]. Close-coupling calculations of the collisional excitation cross sections of the fine-structure levels of NH by He are calculated for total energies up to 3500 cm(-1), which yield, after thermal average, rate coefficients up to 350 K. The fine-structure splitting of rotational levels is taken into account rigorously. The propensity rules between fine-structure levels are reported, and it is found that F-conserving cross sections are much larger than F-changing cross sections, as expected from theoretical considerations. The calculated rate coefficients are compared with available experimental measurements at room temperature and a fairly good agreement is found between experimental and theoretical data. The agreement confirms the relatively good quality of the scattering calculations and also the accuracy of the potential energy surface used in this work. The new set of thermal rate coefficients for this system may be used for improvements in astrophysical and atmospherical modeling.     

Statistical approaches to forcefield calibration and prediction uncertainty in molecular simulation

Calibration of forcefields for molecular simulation should account for the measurement uncertainty of the reference dataset and for the model inadequacy, i.e., the inability of the force-field/simulation pair to reproduce experimental data within their uncertainty range. In all rigour, the resulting uncertainty of calibrated force-field parameters is a source of uncertainty for simulation predictions. Various calibration strategies and calibration models within the Bayesian calibration/prediction framework are explored in the present article. In the case of Lennard-Jones potential for Argon, we show that prediction uncertainty for thermodynamical and transport properties, albeit very small, is larger than statistical simulation uncertainty.     

Round-robins in the area of uranium and plutonium bulk analysis of environmental samples

In the framework of a collaboration between laboratories involved in bulk U and Pu analysis of environmental samples (DIF centre of the French Commissariat à l’Energie Atomique, US National Laboratories of New Brunswick, Lawrence Livermore, Pacific Northwest, Oak Ridge, and Los Alamos), two round-robins were organised, each one consisting of the complete analysis (chemical preparation and isotope measurement) of three Quality Control samples. The samples were 10 × 10 cm cotton tissues (“swipe samples”) containing low amounts of U (from ~20 to ~150 ng) and Pu (from ~0.15 to ~10 pg). Despite using different spikes, different methods of sample preparation and different analytical instrumentation, the results for U and Pu contents and isotopic compositions reported by all laboratories are globally in good agreement. All laboratories are able to measure sub-pg amounts of U and Pu isotopes with acceptable accuracy and reproducibility, even if limited discrepancies are observed affecting one or other measurement and/or laboratory. General and laboratory specific recommendations were discussed and adopted to continue to improve the accuracy and precision of the measurements.