No abstract

The direct generation of efficient, tunable, and switchable circularly polarized laser emission (CPLE) would have far-reaching implications in photonics and material sciences. In this paper, we describe the first chiral simple organic molecules (SOMs) capable of simultaneously sustaining significant chemical robustness, high fluorescence quantum yields, and circularly polarized luminescence (CPL) ellipticity levels (|glum|) comparable to those of similar CPL-SOMs. All these parameters altogether enable efficient laser emission and CPLE with ellipticity levels 2 orders of magnitude stronger than the intrinsic CPL ones.

Ethanol was used for the extraction and purification of lipids from the biomass of the microalga Phaeodactylum tricornutum. This microalga is an oil-rich substrate with a high proportion of eicosapentaenoic acid (EPA). The process consisted of two steps. First, ethanol (96% vol/vol) was used to extract the lipids from the lyophilized biomass. Second, a biphasic system was formed by adding water and hexane to the extracted crude oil. In this way, most of the lipids were transferred to the hexanic phase while most impurities remained in the hydroalcoholic phase. The first step was carried out by two consecutive extractions at room temperature, each with 5 mL ethanol per gram of biomass, for 10 and 1.25 h, respectively. Under these conditions, over 90% of the saponifiable lipids in the biomass were extracted. In the second step, the percentage of water in the hydroalcoholic phase, the hexane/hydroalcoholic phase ratio and the number of extraction steps were optimized. A water content of 40% vol/vol in the hydroalcoholic phase provided the highest lipid recovery. A recovery yield of 80% was obtained by four consecutive extractions with a hexane/ hydroalcoholic phase ratio of 0.2 (vol/vol). Equilibrium distribution data of the lipids between the hydroethanolic and the hexanic phases were also obtained in order to predict the lipid recovery yield of the extraction. This process is an alternative to the traditional methods of lipid extraction, which uses less toxic solvents and reduces the total amount of solvents used.

Emission from electronically excited species forms the basis for an important class of light sources-lasers. So far, commercially available solution-processed blue-emitting laser materials are based on organic compounds or semiconductor nanocrystals that have significant limitations: either low solubility, low chemical-and/or photo-stability and/or uncompetitive prices. Here we report a novel and competitive alternative to these existing laser materials that is based on boron hydrides, inorganic cluster compounds with a rich and diverse chemistry. We demonstrate that solutions of the borane anti-B 18 H 22 show, under pulsed excitation, blue laser emission at 406 nm with an efficiency (ratio of output/input energies) of 9.5%, and a photostability superior to many of the commercially available state-of-the-art blue laser dyes. This demonstration opens the doors for the development of a whole new class of laser materials based on a previously untapped resource for laser technology-the boranes.

The developments of the open-source chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes can address, while showing that is an attractive platform for state-of-the-art atomistic computer simulations.

We establish an efficient strategy to optimize the performance of dye-doped host materials consisting of analyzing in a systematic way the dependence of their Amplified Spontaneous Emission (ASE) efficiency and photostability on the composition and structure of the matrices, selected to specifically avoid the thermal and/or chemical (photooxidation) processes, main mechanisms of dye photodegradation. For this study, a number of experimental polyimides have been chosen as a host matrix and their behavior has been compared with that of poly(methyl methacrylate) (PMMA). We correlate the optical properties with the oxygen permeation and thermal properties of the different polymeric hosts doped with perylene dyes to deepen the understanding of the photodegradation mechanism predominant in these dyes and to minimize its influence. We demonstrate high efficiency and photostable ASE from waveguides based on polymeric materials doped with Perylene Orange (PO), Perylene Red (PR), and mixtures of both. This enhancement in the optical properties allows reaching high gain and long-lasting distributed feedback (DFB) laser emission based on PO doped polymer matrices, even when operating in an unoptimised resonator.

Scheme 2 . Synthetic routes of derivatives 6 , 8 , and 15 from parent dye PM597. Scheme 1 . Synthetic routes of derivatives 2 , 7 , and 11 from parent dye PM567.

B18H20(NC5H5)2 is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of B18H20(NC5H5)2 emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a thermochromicity to the fluorescence of B18H20(NC5H5)2. Cooling to 8 K engenders a further shift in the emission wavelength to 585 nm and a twofold increase in intensity. Immobilization in a polystyrene thin‐film matrix results in an efficient absorption of pumping excitation energy at 414 nm and a 609 nm photostable fluorescence. Such fluorescence from polystyrene thin films containing B18H20(NC5H5)2 can also be stimulated by emission from the highly fluorescent borane anti‐B18H22 via energy transfer mechanisms. Polystyrene thin‐film membranes doped with 1:1 mixtures of anti‐B18H22 and B18H20(NC5H5)2 thus emit a 609 nm fluorescence and absorb light across more than 300 nm (250–550 nm); this is a significant spectral coverage possibly useful for luminescent solar concentrators. B18H20(NC5H5)2 is fully structurally characterized using NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction analysis, and its ground‐state and excited‐state photophysics are investigated with UV–vis spectroscopy and quantum‐chemistry computational methods.