Jilin University

About: Jilin University is a education organization based out in Changchun, China. It is known for research contribution in the topics: Catalysis & Apoptosis. The organization has 101453 authors who have published 88966 publications receiving 1444456 citations. The organization is also known as: Jílín Dàxué.

Simultaneously Enhancing the Thermal Stability, Mechanical Modulus, and Electrochemical Performance of Solid Polymer Electrolytes by Incorporating 2D Sheets

Abstract: Lithium ion batteries are now the dominant power for electronics and will change the power supply for vehicles and help to smoothly integrate renewable energy sources such as solar and wind to grid. In lithium ion batteries with liquid electrolytes, the organic solvents are flammable and unstable at high voltage. Especially in lithium metal batteries (LMB) where lithium dendrites can grow, the solvents can be ignited once the dendrites shortcircuit with the cathodes. To meet the high energy density and safety requirement, it is desirable to develop solid state electrolytes with high stability and mechanical strength. The solid state electrolytes can be classified into two categories: inorganic electrolytes and solid polymer electrolytes (SPE). Inorganic electrolytes typically have ionic conductivity at room temperature (10−2–10−4 S cm−1) close to or even higher than liquid electrolyte. However, their stiffness and friability result in poor film processability and high interface resistance with electrodes.[1–7] SPE are composed of lithium salts dissociated in the polymer matrix in which Li+ is allowed to transport along with the segment motion of the polymer chains. As a result, SPE are stretchable and flexible, and thus compatible with the current film-based battery technology. However, the low ionic conductivity (<10−6 S cm−1) of SPE at ambient temperature and high-temperature instability restrict their wide utilization.[8–15] Great efforts have been devoted to improving the performance of SPE. Increasing the content of Li salts or decreasing the crystallinity of polymers with composite polymers or block copolymers were able to increase the ionic conductivity by orders of magnitude.[16–18] However, other properties of SPE such as the film forming property were decreased, leading to poor mechanical strength and thermal resistance. A successful strategy was rigid-flexible coupling that applied cellulose nonwoven to support the softened SPE.[11] Another widely employed approach is to add ceramic fillers which can interact with both the salt anions and the polymer segments to promote local amorphization and enhance Li+ transport.[19–24] Accordingly, the interaction can be tailored by screening fillers with Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film-forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few-layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)-based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.

Protein-directed synthesis of pH-responsive red fluorescent copper nanoclusters and their applications in cellular imaging and catalysis

Abstract: The development of functional copper nanoclusters (Cu NCs) is becoming increasingly widespread in consumer technologies due to their applications in cellular imaging and catalysis. Herein, we report a simple protein-directed synthesis of stable, water-soluble and fluorescent Cu NCs, using BSA as the stabilising agent. Meanwhile, in this study, hydrazine hydrate (N2H4·2H2O) was used as the reducing agent. N2H4·2H2O was a mild reducing agent suggesting that all processes could be operated at room temperature. The as-prepared Cu NCs showed red fluorescence with a peaking center at 620 nm (quantum yield 4.1%). The fluorescence of the as-prepared BSA–Cu NCs was responsive to pH in that the intensity of fluorescence increased rapidly by decreasing the pH from 12 to 6. Besides, with an arresting set of features including water-dispersibility, red fluorescence, good biocompatibility, surface-bioactivity and small size, the resultant BSA–Cu NCs could be used as probes for cellular imaging and catalysis. In this study, CAL-27 cells and the reaction of oxidation of styrene are used as models to achieve fluorescence imaging and elucidate the catalytic activity of the as-prepared BSA–Cu NCs.

A negative binomial integer-valued GARCH model

Abstract: This article discusses the modelling of integer-valued time series with overdispersion and potential extreme observations. For the problem, a negative binomial INGARCH model, a generalization of the Poisson INGARCH model, is proposed and stationarity conditions are given as well as the autocorrelation function. For estimation, we present three approaches with the focus on the maximum likelihood approach. Some results from numerical studies are presented and indicate that the proposed methodology performs better than the Poisson and double Poisson model-based methods.

Pyrene-substituted ethenes: aggregation-enhanced excimer emission and highly efficient electroluminescence

Abstract: Pyrene-substituted ethenes, 1,2,2-tripheny-1-pyrenylethene (TPPyE) and 1,2-diphenyl-1,2-dipyrenylethene (DPDPyE), are synthesized and characterized. Whereas they are weakly emissive in solution they become strong emitters when aggregated in the condensed phase. In contrast to the general observation that excimer formation quenches the light emission of fluorophores, TPPyE and DPDPyE exhibit efficient excimer emissions in the solid state with high fluorescence quantum yields up to 100%. The π–π intermolecular interactions between the pyrene rings, coupled with multiple C–H⋯π hydrogen bonds, efficiently restrict intramolecular rotations, which block the nonradiative energy decay channel, and hence make the dye molecules highly emissive in the solid state. Non-doped organic light-emitting diodes using TPPyE and DPDPyE as emitters are fabricated, which give green light at low turn-on voltages (down to 3.2 V) with maximum luminance and power, current, and external quantum efficiencies of 49830 cd m−2, 9.2 lm W−1, 10.2 cd A−1 and 3.3%, respectively.