Latest ArticlesWith the development of single-molecule detection and super-resolution fluorescence imaging, rhodamine dyes gain new life. Through the modification of the N-substituents and the replacement of the oxygen atom in xanthene, the wavelength and brightness can be effectively changed. However, the spectra of rhodamine, especially due to the balance between ring-closed non-fluorescent lactone and ring-opened fluorescent zwitterion/cation, are sensitive to interference from various environmental factors. In this way, the spectral data of various rhodamines reported by different research groups under different test conditions lacked comparability, sometimes even lacked accuracy. In order to meet the requirements for the accuracy and uniformity of spectral data in the research of single molecule imaging and dye structure-fluorescence relationship study, we have tested the spectra of fifteen rhodamine dyes that cover the visible and near-infrared regions under exactly the same conditions. By studying the dependence of the spectra on dye concentrations, it was confirmed that 1 μmol/L was ideal for detection less from the interference of dye molecule aggregation. We provide comprehensive and reliable spectral data of these fifteen dyes, which are expected to be used as references for future research. And the direct comparison of different rhodamine spectra would help to understand the structure-fluorescence relationship of rhodamines.
A convergent approach to 1,5-hydroxy ketones, the general precursors for constructing the C ring of bryostatins, has been developed via a Zn/Cu-promoted conjugate addition of α-hydroxy iodides with enones. The reaction leads to direct formation of the C21-C22 bond and tolerates diverse functionalities at the C17-, C18- and C24-positions. The approach also enables a more concise synthesis of the known C ring intermediate (10 longest linear steps and 14 total steps), in contrast to its previous synthesis (17 longest linear steps and 22 total steps) in our total synthesis of bryostatin 8.
The necessity to explore high-efficiency and high-value utilization strategy for biomass-waste is desirable. Herein, the strategy for direct conversion biomass-waste (rice husks) to Si/C composite structure anode was built. The Si/C composite materials were successfully obtained via the typical thermal reduction with magnesium, and the Si nanoparticle was uniformly embedded in carbon frame, as revealed by Raman, X-ray diffraction (XRD) and transmission electron microscope (TEM) measurement. The carbon structure among rice husks was effectively used as a protective layer to accommodate the volume variation of Si anode during the repeated lithiation/delithiation process. Benefitting from the structure design, the batteries show a superior electrochemical stability with the capacity retention rate above 90% after 150 cycles at the charge/discharge rate of 0.5 C (1 C = 600 mAh/g), and hold a high charge capacity of 420.7 mAh/g at the rate of 3 C. Therefore, our finding not only provides a promising design strategy for directly conversion biomass-waste to electrochemical storage materials but broadens the high-efficiency utilization method for other biomass by-products.
Density functional theory calculations have been performed to investigate the copper-catalyzed borocyanation of 1-aryl-1,3-butadienes. The computations show that the regio- and enantioselectivity is determined by the borocupration step. The π-electron withdrawing aryl group at the C1 atom makes the C4 atom more electrophilic than the other carbon atoms, which together with the steric repulsion around the forming C—B bond, results in the experimentally observed exclusive 4,3-regioselectivity. The origins of the enantioselectivity were attributed to the steric effect and π-π stacking interaction between the butadiene moiety and the ligand.
g-C3N4 have been widely used in the fields of photocatalytic hydrogen production, photocatalytic degradation of dyes and oxidative degradation of toxic gases due to their excellent performance. It has attracted extensive attention in recent years due to its highly efficient photocatalytic capacity of hydrogen generation, water oxidation, carbon dioxide reduction and degradation of organic pollutants. Because of the abundant carbon and nitrogen composition of the earth, large-scale production and industrial applications of this material are possible. The modification of this material makes its performance more excellent so that this new material can obtain a steady stream of vitality. These outstanding works have become important materials and milestones on the road to mankind's photocatalytic hydrogen production. This review will begin with the basic idea of designing, synthesizing and improving g-C3N4 based photocatalytic materials, and introduce the latest development of g-C3N4 photocatalysts in hydrogen production from four aspects of controlling the carbon/nitrogen ratio, morphology, element doping and heterojunction structure of g-C3N4 materials.
A hierarchically structured MnOx-NiCo2O4 monolithic catalyst with rich phase interfaces was designed by a simple, eco-friendly and time-saving in-situ electro-deposition method. The abundance of active oxygen species due to this rich phase interfaces contributed to the excellent benzene combustion performance of MnOx-NiCo2O4-2:2 sample, oxidizing about 90% of benzene (T90) at 198 ℃ under 12000 h-1 gaseous hourly space velocity. This work shed new light on the design of excellent monolithic catalysts, which might pave the way for the industrialization of benzene combustion.
Colorimetric sensing strategies as a powerful point-of-care testing (POCT) tool have attracted significant interest in various chem/biosensing applications. Taking the excellent bare-eye-detectable signaling feature, nanozymes-based colorimetric sensors enable more potential applications and have been a new forefront in the colorimetric POCT analysis toward different target analytes. However, the low catalytic activity of nanozymes in most cases limits their practical application. Recent efforts demonstrate that the aggregation-induced nanozymes provide a general means to modulate nanozymes activity and enhance colorimetric sensing performances of some nanozymes-based colorimetric sensors. But there are few reports are explored to discuss and review such aggregation-induced nanozymes and their colorimetric sensing applications. To highlight the advances and progress in aggregation-induced nanozymes based colorimetric assays, we herein summary the fundamentals, classify and applications of this newly-developing field, focusing on the aggregation-induced activity enhancement of nanozymes (AIAE-nanozymes) with a significant "signal-on" feature and aggregation-induced activity inhibition of nanozymes (AIAI-nanozymes) with a dramatical "signal-off" characteristics. Finally, we also propose the current challenges and the future prospects on both AIAE-nanozymes and AIAI-nanozymes.
Two sulfonated seco C20-diterpenoid alkaloids, aconapelsulfonines A (1) and B (2), were isolated from an aqueous extract of the raw material of "Fu Zi" (the Aconitum carmichaelii lateral roots), of which the structures were elucidated by various spectroscopic data, combined with X-ray crystallographic analysis. The unprecedented skeletons are biogenetically proposed to be derived via Criegee rearrangements of the napelline-type architecture. The two compounds exhibited dose-depended analgesic activities on an acetic acid-induced mice writhing test.
Generation of multi-substituted pyrroles is accomplished through an unexpected iron(Ⅱ)-promoted reaction of N-arylprop-2-yn-1-imines with water. This transformation proceeds smoothly with excellent chemoselectivity and regioselectivity. A stoichiometric amount of Fe(OTf)2 is necessary for the successful conversion. A Lewis acid-promoted tandem reaction pathway is proposed.
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