Insights into the Control of Optoelectronic Properties in Mixed-Stacking Charge-Transfer Complexes

Although cocrystallization has provided a promising platform to develop new organic optoelectronic materials, it is still a big challenge to purposely design and achieve specific optoelectronic properties. Herein, a series of mixed-stacking cocrystals (TMFA, TMCA, and TMTQ) were designed and synthesized, and the regulatory effects of the acceptors on the co-assembly behavior, charge-transfer nature, energy-level structures, and optoelectronic characteristics were systematically investigated. The results demonstrate that it is feasible to achieve effective charge-transport tuning and photoresponse switching by carefully regulating the intermolecular charge transfer and energy orbitals. The inherent mechanisms underlying the change in these optoelectronic behaviors were analyzed in depth and elucidated to provide clear guidelines for future development of new optoelectronic materials. In addition, due to the excellent photoresponsive characteristics of TMCA, TMCA-based phototransistors were investigated with varying light wavelength and optical power, and TMCA shows the best performance among all reported cocrystals under UV illumination.     

Recent Advances in Iodine-Promoted C−S/N−S Bonds Formation

Sulfur-containing scaffold, as a ubiquitous structural motif, has been frequently used in natural products, bioactive chemicals and pharmaceuticals, particularly C−S/N−S bonds are indispensable in many biological important compounds and pharmaceuticals. Development of mild and general methods for C−S/N−S bonds formation has great significance in modern research. Iodine and its derivatives have been recognized as inexpensive, environmentally benign and easy-handled catalysts or reagents to promote the construction of C−S/N−S bonds under mild reaction conditions, with good regioselectivities and broad substrate scope. Especially based on this, several new strategies, such as oxidation relay strategy, have been greatly developed and accelerated the advancement of this field. This review focuses on recent advances in iodine and its derivatives promoted hybridized C−S/N−S bonds formation. The features and mechanisms of corresponding reactions are summarized and the results of some cases are compared with those of previous reports. In addition, the future of this domain is discussed.     

High throughput online sequential extraction of natural rare earth elements and determination by mass spectrometry

At the beginning of rare earth industry,several days are normally required for characterization of rare earth elements(REEs)fractionation in ore samples.Herein,rapid fractionation analysis of 15 REEs and accompanied metal(Fe,Mn,etc.)in ore samples has been achieved within 1 h using ICP-MS with a homemade device for online sequential solvent extraction.As a result,five fractionations for REEs occurrences,i.e.,water soluble,exchangeable,reducible,oxidizable and crystalline,have been identified,offering chemical insights which not only reveal the formation mechanism of REEs ores but also show great implications for guiding the exploitation and separation of REEs.In comparison with conventional methods,the present approach significantly shortened the analysis time(1 h vs.~80 h)and reduced the sample consumption(1.0 mg vs.5.0 g)with high recovery(>95%),providing a useful platform for the rapid quantitative fractionation analysis of REEs in complexed samples such as ore and fossils.     

Ratiometric Detection of microRNA Using Hybridization Chain Reaction and Fluorogenic Silver Nanoclusters

miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application.     

Multistable dynamics in a Hopfield neural network under electromagnetic radiation and dual bias currents

Nonlinear Dynamics - This paper investigates a Hopfield neural network under the simulation of external electromagnetic radiation and dual bias currents, in which the fluctuation of magnetic flux...     

The effect of scintillator materials on the fast neutron multiplicity measurement

Journal of Radioanalytical and Nuclear Chemistry - To analyze the effect of scintillator detectors on the fast neutron multiplicity, this paper uses Geant4 and Matlab to simulate and study three...     

Lewis酸催化纤维素制乳酸机理研究

Because fossil fuels are continuously depleted, valorization of biomass into valuable liquid products and chemicals is of great significance yet it remains challenging. Among many biomass-derived products, lactic acid is one of the most important renewable monomers for preparing the degradable polymer polylactic acid. The use of raw biomass to produce lactic acid through catalytic conversion is an attractive approach. In this work, the catalytic reaction performance and mechanism of different Lewis acids (Y³⁺, Sc³⁺, and Al³⁺) for the production of lactic acid from cellulose were investigated in detail by isotopic nuclear magnetic resonance (NMR) and mass spectrometry. The production of lactic acid from cellulose includes tandem and competing reactions. The order of catalytic activity for the one-pot conversion of cellulose into lactic acid is as follows: Y³⁺ > Al³⁺ > Sc³⁺. The main tandem reactions involve the hydrolysis of cellulose into glucose, the isomerization of glucose into fructose (the order of catalytic activity, the same below: Y³⁺ > Al³⁺, Y³⁺ > Sc³⁺), the cleavage of fructose via a retro-aldol reaction to glyceraldehyde (GLY) and 1, 3-dihydroxyacetone (DHA) (Sc³⁺ > Y³⁺ > Al³⁺), and the conversion of DHA or GLY to the final product lactic acid (Al³⁺ > Y³⁺ > Sc³⁺). It was found that the process of glucose isomerization to fructose was the key step to the final selectivity of the tandem reaction of cellulose conversion to lactic acid, and it was clarified that the production of lactic acid from DHA underwent a keto-enol (K-E) tautomerization process rather than a classical 1, 2-shift process. First, DHA was transformed into GLY via the isomerization process, then the adjacent hydroxyl group of GLY was removed in the form of water to produce an α, β-unsaturated species. After that, the α, β-unsaturated species underwent K-E tautomerization to generate unsaturated aldehyde-ketone intermediates. Meanwhile, a molecule of water was added to aldehyde-ketone intermediates to obtain a diol product, the hydrogen atom at the methine position was transferred and the lactic acid was finally obtained through the K-E tautomerization process. The in-depth understanding of the reaction mechanism presented in this work will help to design more selective catalysts for cellulose conversion into value-added oxygen-containing small molecule chemicals.      

Two-dimensional Supramolecular Polymers Based on Selectively Recognized Aromatic Cation-π and Donor-Acceptor Motifs for Photocatalytic Hydrogen Evolution

Two-dimensional (2D) organic polymers have recently received considerable interest, especially those whose architectures are held together via supramolecular engineering. However, current approaches toward supramolecular 2D structures usually suffer from mutual interference of noncovalent interactions and lack of intrinsic functions. Herein, we report well-regulated 2D supramolecular polymers (2DSPs) through an aromatics-selective recognition strategy of cation-π and donor-acceptor (D-A) motifs, which are derived from C₄-symmetric cationic monomers and electron-withdrawing molecules. By subtly designing the strength and direction of noncovalent driving forces, the mutual interference between cation-π and D-A interactions is effectively avoided, enabling the construction of 2DSPs in aqueous solution. On this basis, the resultant 2DSPs possess boosted photocatalytic hydrogen evolution activity at a rate of 600 μmol g⁻¹ h⁻¹, which is mainly ascribed to the specific stacking mode of cation-π/D-A motifs and the ordered 2D structures.