Ultrafast continuum mid-infrared spectroscopy: probing the entire vibrational spectrum in a single laser shot with femtosecond time resolution

Until now, ultrafast IR spectroscopy has been limited by the bandwidth of optical parametric amplifiers, typically 100-400 cm(-1). Here we present the first example of transient IR spectroscopy using a continuum laser source to probe the entire mid-IR region with ultrafast time resolution. The continuum source is based on focusing the fundamental, second harmonic, and third harmonic of 1 mJ, 25 fs, 800 nm pulses in air, generating ～150 fs continuum mid-IR pulses that span the frequency range of <400 to >5000 cm(-1) or, conversely, <2 to >25 μm. We characterize the spectral and temporal properties of dicarbonylacetonato rhodium(I) in hexane. We further demonstrate the versatility of the method by measuring the very fast and broad (>1500 cm(-1)) spectral changes following IR excitation associated with the 7-azaindole-acetic acid heterodimer in carbon tetrachloride.     

Three-dimensional photoprecipitation of oriented LiNbO3-like crystals in silica-based glass with femtosecond laser irradiation

We demonstrate crystals (LiNbO(3)-like) that were space-selectively nucleated and grown in the bulk of silica-based glass by femtosecond laser irradiation at a high repetition rate (typ. 300 kHz). Oriented crystals with their polar axis mostly aligned with or perpendicular to the laser scanning direction have been fabricated by manipulation of the temperature gradient in adjusting the laser parameters. The mechanism for the orientation of femtosecond laser-induced crystallization is briefly discussed.     

Influence of polymorphism on charge transport properties in isomers of fluorenone-based liquid crystalline semiconductors

We measured the charge carrier mobilities for two isomers of fluorenone-based liquid crystalline organic semiconductors from their isotropic down to crystalline states through one or two mesophases. Improved charge transport properties of melt-processed crystalline films were obtained for the isomer exhibiting a highly ordered mesophase below its disordered smectic phase.     

Efficient quantum-state estimation by continuous weak measurement and dynamical control

We demonstrate a fast, robust, and nondestructive protocol for quantum-state estimation based on continuous weak measurement in the presence of a controlled dynamical evolution. Our experiment uses optically probed atomic spins as a test bed and successfully reconstructs a range of trial states with fidelities of approximately 90%. The procedure holds promise as a practical diagnostic tool for the study of complex quantum dynamics, the testing of quantum hardware, and as a starting point for new types of quantum feedback control.     

Investigating Acrylic Acid Polymerization by Using a Droplet-Based Millifluidics Approach

We present herein the basic concept of droplet-based millifluidics as an original tool to monitor polymerization kinetics. As a proof of concept, we use aqueous droplets of acrylic acid mixed with sodium persulfate at various pH as polymerization microreactor models. According to the pH and the temperature, completion could be obtained within a minute. Despite the fact that this reaction is quite fast and exothermic, we were able to acquire data in order to obtain valuable information about the polymerization kinetics. We were also able to estimate the overall activation energy for polymerization rate. Furthermore, offline analyses by Size Exclusion Chromatography show high molecular weights and high polydispersities. These results set the stage for further studies of polymerization reactions where detailed basic kinetic data must be acquired in conditions which cannot be investigated by using conventional batch glassware (i.e. high temperatures or concentrations). This new approach can also be used as an efficient High Throughput Screening tool.     

Surface treatment and characterization: perspectives to electrophoresis and lab-on-chips

The control and modification of surface state is a major challenge in bioanalytical sciences, and in particular in electrokinetic separation methods, due to the importance of electroosmosis. This topic has gained recently a renewed interest, associated with the development of "lab-on-chips" systems that extend the range of materials in which separation channels are fabricated. The surface science community has developed through the years a large toolbox of characterization tools and surface modification protocols, which is not yet fully exploited in the bioanalytical world. In this paper, we try and present an overview of these tools, in order to stimulate new ideas for improved and more controlled surface treatment strategies for separations in capillaries and microchannels. We briefly describe some physical and chemical aspects of electroosmosis (global and spatially resolved), streaming current, and streaming potential. We also review the main strategies for surface coating, and compare the advantages of physisorption, well-organized thin self-assembled monolayers, or conversely thick polymer "brushes". Examples of existing applications to electrophoresis in microchannel are also given.     

Catalytic enantioselective three-component hetero-[4+2] cycloaddition/allylboration approach to alpha-hydroxyalkyl pyrans: scope, limitations, and mechanistic proposal

This article describes the design and optimization of a catalytic enantioselective three-component hetero-[4+2] cycloaddition/allylboration reaction between 3-boronoacrolein, enol ethers, and aldehydes to afford alpha-hydroxyalkyl dihydropyrans. The key substrate, 3-boronoacrolein pinacolate (2) was found to be an exceptionally reactive heterodiene in the hetero-[4+2] cycloaddition catalyzed by Jacobsen's chiral Cr(III) catalyst 1. The scope and limitations of this process were thoroughly examined. The adduct of 3-boronoacrolein pinacolate and ethyl vinyl ether was obtained in high yield and with over 95 % enantioselectivity. This cyclic alpha-chiral allylboronate adds to a very wide variety of aldehyde substrates, including unsaturated aldehydes and alpha-chiral aldehydes to give diastereomerically pure products. Acyclic 2-substituted enol ethers can be employed, in which case the catalyst promotes a kinetically selective reaction that favors Z enol ethers over the E isomers. Surprisingly, 3-boronoacrolein pinacolate was found to be a superior heterodiene than ethyl (E)-4-oxobutenoate, and a mechanistic interpretation based on a possible [5+2] transition state is proposed.     

Silver coordination complexes as room-temperature multifunctional materials

A series of bischelate ionic silver complexes [Ag(L*)(2)][X] was prepared by complexation of a newly synthesized 2,2'-bipyridine containing chiral alkoxy chains in the 4,4' positions. The appropriate choice of the construction motifs allows the preparation of new materials in which several functionalities can be introduced. Indeed, when the anion X(-) is a triflate or a dodecylsulfate group, the right combination of intermolecular interactions promotes the production of liquid crystalline mesophases. Therefore, the presence of coordinating anions, which drives the supramolecular assembly, is essential to generate, at the same time, room-temperature columnar hexagonal mesomorphism, the columnar helical supramolecular structure, and excimeric emission.     

Biotransformation of the triketone herbicide mesotrione by a Bacillus strain. Metabolite profiling using liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry

The metabolic pathway involved in the biotransformation of the herbicide mesotrione by the bacterial strain Bacillus sp. 3B6 was investigated by a reliable liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOF-MS) method. The LC/ESI-MS method, both in positive and negative mode, with the assistance of MS(2) fragments and isotopic pattern analyses, allowed us to identify five metabolites. This work constitutes the first complete monitoring of mesotrione degradation kinetics. Among the transformation products found by both techniques, one was formed by intramolecular cyclization between a hydroxylamine and a keto function, which is quite a rare biological reactivity process. For each identified metabolite, a fragmentation pathway is proposed for negative and positive mode.