Nankai University

About: Nankai University is a education organization based out in Tianjin, China. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 42964 authors who have published 51866 publications receiving 1127896 citations. The organization is also known as: Nánkāi Dàxué.

Advances in intense femtosecond laser filamentation in air

Abstract: This is a review of some recent development in femtosecond filamentation science with emphasis on our collective work. Previously reviewed work in the field will not be discussed. We thus start with a very brief description of the fundamental physics of single filamentation of powerful femtosecond laser pulses in air. Intensity clamping is emphasized. One consequence is that the peak intensity inside one or more filaments would not increase significantly even if one focuses the pulse at very high peak power even up to the peta-watt level. Another is that the clamped intensity is independent of pressure. One interesting outcome of the high intensity inside a filament is filament fusion which comes from the nonlinear change of index of refraction inside the filament leading to cross beam focusing. Because of the high intensity inside the filament, one can envisage nonlinear phenomena taking place inside a filament such as a new type of Raman red shift and the generation of very broad band supercontinuum into the infrared through four-wave-mixing. This is what we call by filamentation nonlinear optics. It includes also terahertz generation from inside the filament. The latter is discussed separately because of its special importance to those working in the field of safety and security in recent years. When the filamenting pulse is linearly polarized, the isotropic nature of air becomes birefringent both electronically (instantaneous) and through molecular wave packet rotation and revival (delayed). Such birefringence is discussed in detailed. Because, in principle, a filament can be projected to a long distance in air, applications to pollution measurement as well as other atmospheric science could be earned out. We call this filamentation atmospheric science. Thus, the following subjects are discussed briefly, namely, lightning control, rain making, remote measurement of electric field, microwave guidance and remote sensing of pollutants. A discussion on the higher order Kerr effect on the physics of filamentation is also given. This is a new hot subject of current debate. This review ends on giving our view of the prospect of progress of this field of filamentation in the future. We believe it hinges upon the development of the laser technology based upon the physical understanding of filamentation and on the reduction in price of the laser system.

Exfoliated-SnS2 restacked on graphene as a high-capacity, high-rate, and long-cycle life anode for sodium ion batteries

Abstract: Designed as a high-capacity, high-rate, and long-cycle life anode for sodium ion batteries, exfoliated-SnS2 restacked on graphene is prepared by the hydrolysis of lithiated SnS2 followed by a facile hydrothermal method. Structural and morphological characterizations demonstrate that ultrasmall SnS2 nanoplates (with a typical size of 20–50 nm) composed of 2–5 layers are homogeneously decorated on the surface of graphene, while the hybrid structure self-assembles into a three-dimensional (3D) network architecture. The obtained SnS2/graphene nanocomposite delivers a remarkable capacity as high as 650 mA h g−1 at a current density of 200 mA g−1. More impressively, the capacity can reach 326 mA h g−1 even at 4000 mA g−1 and remains stable at ∼610 mA h g−1 without fading up to 300 cycles when the rate is brought back to 200 mA g−1. The excellent electrochemical performance is attributed to the synergetic effects between the ultrasmall SnS2 and the highly conductive graphene network. The unique structure can simultaneously facilitate Na+ ion diffusion, provide more reaction sites, and suppress aggregation and volume fluctuation of the active materials during prolonged cycling.

Sulfuration of an Fe-N-C Catalyst Containing Fe x C/Fe Species to Enhance the Catalysis of Oxygen Reduction in Acidic Media and for Use in Flexible Zn-Air Batteries

Abstract: During the preparation of atomically dispersed Fe-N-C catalysts, it is difficult to avoid the formation of iron-carbide-containing iron clusters ("Fex C/Fe"), along with the desired carbon matrix containing dispersed FeNx sites. As a result, an uncertain amount of the oxygen reduction reaction (ORR) occurs, making it difficult to maximize the catalytic efficiency. Herein, sulfuration is used to boost the activity of Fex C/Fe, forming an improved system, "FeNC-S-Fex C/Fe", for catalysis involving oxygen. Various spectroscopic techniques are used to define the composition of the active sites, which include Fe-S bonds at the interface of the now-S-doped carbon matrix and the Fex C/Fe clusters. In addition to outstanding activity in basic media, FeNC-S-Fex C/Fe exhibits improved ORR activity and durability in acidic media; its half-wave potential of 0.821 V outperforms the commercial Pt/C catalyst (20%), and its activity does not decay even after 10 000 cycles. Interestingly, the catalytic activity for the oxygen evolution reaction (OER) simultaneously improves. Thus, FeNC-S-Fex C/Fe can be used as a high-performance bifunctional catalyst in Zn-air batteries. Theoretical calculations and control experiments show that the original FeNx active centers are enhanced by the Fex C/Fe clusters and the Fe-S and C-S-C bonds.

Amine-Functionalized Magnetic Nanoparticles for Rapid Capture and Removal of Bacterial Pathogens

Abstract: Interest in magnetic nanoparticles for capturing bacteria arises from a variety of attributes, including the similar size of nanoparticles, magnetic behavior, and attached biomolecules such as proteins and nucleotide probes. Here we report the application of amine-functionalized magnetic nanoparticles (AF-MNPs) for rapid and efficient capture and removal of bacterial pathogens. The AF-MNPs are used without the need for any further modifications with affinity biomolecules. The positive charges on the surface of AF-MNPs can promote strong electrostatic interaction with negatively charged sites on the surface of bacterial pathogens to exhibit efficient adsorptive ability. The hydrophobic interaction between the pendant propyl group of the amine functionality and the bacteria also plays a supplementary role. The amine groups on the surface of the magnetic nanoparticle are robust and inexpensive ligands to ensure a high binding affinity to at least eight different species of Gram-positive and Gram-negative bacteria. The amount of AF-MNPs, pH of phosphate buffer solution, and ionic strength are crucial in mediating fast and effective interactions between AF-MNPs and bacteria. The AF-MNPs allow rapid removal of bacteria from water samples, food matrixes, and a urine sample with efficiency from 88.5% to 99.1%. Though amino group offers less specificity/selectivity than biomolecules such as antibodies, AF-MNPs are attractive for capturing a wide range of bacteria.

Mitophagy, Mitochondrial Homeostasis, and Cell Fate.

Abstract: Mitochondria are highly plastic and dynamic organelles that have graded responses to the changing cellular, environmental, and developmental cues. Mitochondria undergo constant mitochondrial fission and fusion, mitochondrial biogenesis, and mitophagy, which coordinately control mitochondrial morphology, quantity, quality, turnover, and inheritance. Mitophagy is a cellular process that selectively removes the aged and damaged mitochondria via the specific sequestration and engulfment of mitochondria for subsequent lysosomal degradation. It plays a pivotal role in reinstating cellular homeostasis in normal physiology and conditions of stress. Damaged mitochondria may either instigate innate immunity through the overproduction of ROS or the release of mtDNA, or trigger cell death through the release of cytochrome c and other apoptogenic factors when mitochondria damage is beyond repair. Distinct molecular machineries and signaling pathways are found to regulate these mitochondrial dynamics and behaviors. It is less clear how mitochondrial behaviors are coordinated at molecular levels. BCL2 family proteins interact within family members to regulate mitochondrial outer membrane permeabilization and apoptosis. They were also described as global regulators of mitochondrial homeostasis and mitochondrial fate through their interaction with distinct partners including Drp1, mitofusins, PGAM5, and even LC3 that involved mitochondrial dynamics and behaviors. In this review, we summarize recent findings on molecular pathways governing mitophagy and its coordination with other mitochondrial behaviors, which together determine cellular fate.