摘要：
A novel catalyst of FeCo nanoparticles (FeCo NPs) incorporated porous nanocages (FeCo NPs@PNC) was first synthesized by encapsulating of FeCo alloy into ZIF-8 and further carbonation of the composite. The FeCo NPs@PNC displays enhanced intrinsic oxidase-like activity compared to the individual FeCo NPs and porous nanocages (PNC). The FeCo NPs@PNC can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) without H2O2, producing a blue color with a maximum absorption peak at 652nm. The catalytic mechanism was investigated and it found that the intermediate (O2(.-)) produced from the catalytic process in the system of TMB-O2-FeCo NPs@PNC can accelerate the oxidation of TMB to oxTMB. However, ascorbic acid (AA) can reduce the oxTMB and result in a conspicuous blue color fading. Therefore, a novel colorimetric platform was constructed to quantify AA with the linear range of 0.5-28muM and detection limit of 0.38muM (at 3sigma/m). Owing to the alkaline phosphatase (ALP) can catalyze the hydrolysis of AA 2-phosphate (AAP) into AA, ALP can also be quantified by the above method. And the linear range for ALP is 0.6-10 U L(-1) and the limit of detection is 0.49 U L(-1). The FeCo NPs@PNC also shows excellent stability and reproducibility. This study provides a new alternative oxidase mimetic on the basis of easily obtained metal-organic frameworks derivatives to replace the expensive natural enzymes and noble metal based nanoenzymes, which will show great potential in biological assays.
摘要：
The plasticity and α→ω transformation are important for the toughness and ductility of hcp titanium under shock loading. However, three questions remain outstanding: (i) what mechanisms govern the plasticity and transformation, (ii) how does the microstructure, i.e., grain boundaries (GBs) and crystallographic orientations, affect them, and (iii) does the transformation take place dependent on the plasticity, such as dislocation slips? We conduct large-scale nonequilibrium molecular dynamics simulations to study shock-induced plasticity and phase transformation in hexagonal columnar nanocrystalline Ti. Significant anisotropy and strong dependence on crystallographic orientation are presented during shock-induced plasticity and phase transformation. The shock first prompts “heterogeneous” dislocation slips and 90∘ lattice reorientation, via coupling deformation twinning and slips. Then, the on-going plastic deformation induces a “heterogeneous” α→ω phase transformation at lower impact velocities or a “homogeneous” solid-state disordering at higher impact velocities. The phase transformation mostly obeys the TAO-1 pathways originated from GBs, while a few of them are governed by Silcock mechanisms within the grains. The TAO-1 and Silcock-governed transformations stem from the emission and propagation of basal-prismatic and prismatic stacking faults, respectively. At the release/tension stage, a ω→α transformation occurs, acting as the reversed process of the α→ω transformation at the compression stage. Meanwhile, structural recovery and spallation initiate in the extending tension area induced by the release fans. Serving as the nucleation of the plasticity, phase transformation, and spallation, GBs play the key role during the loading.
作者机构：
[Zhang, Youyu; Wu, Tengteng; Ma, Zhangyan; Liu, Meiling; Hou, Wenli; Yao, Shouzhuo] Hunan Normal Univ, Coll Chem & Chem Engn, Minist Educ, Key Lab Chem Biol & Tradit Chinese Med Res, Changsha 410081, Hunan, Peoples R China.;[Liu, Xiaoying] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Liu, Meiling; Liu, Xiaoying] H;Hunan Normal Univ, Coll Chem & Chem Engn, Minist Educ, Key Lab Chem Biol & Tradit Chinese Med Res, Changsha 410081, Hunan, Peoples R China.;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
*3,3,5,5-Tetramethylbenzidine;*Colorimetric assay;*Enzyme mimic;*Inhibition;*Nanocubes;*Peroxidase mimetic;*Prussian White
摘要：
Colorimetric methods are described for the determination of ascorbic acid (AA) and alkaline phosphatase (ALP). Both assays are based on the inhibition of the peroxidase (POx)-like activity of Prussian Blue nanocubes (PB NCs) capped with citric acid. They catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to produce a blue color with an absorption maximum at 652 nm. On addition of AA, the PB NCs are reduced to Prussian White (PW) which does not act as a POx mimic. This results in a decreased rate of the formation of the blue coloration whose intensity decreases with increasing concentration of AA. The assay allows AA to be quantified with a 35 nM detection limit (at 3sigma/m). The hydrolysis of AA phosphate by ALP leads to the formation of AA which can be quantified by the above method. Based on this, the activity of ALP can be determined by measurement of the intensity of the blue coloration thus formed. The method can be used to determine the activity of ALP with a detection limit as low as 0.23 U.L(-1). Graphical abstract Schematic presentation of a method for colorimetric determination of ALP activity. AA obtained by ALP-catalyzed hydrolysis of ascorbic acid phosphate (AAP) inhibits the intrinsic peroxidase-like activity of PB NCs by reducing Prussian Blue nanocrystals (PB NCs) to form inactive Prussian White (PW).
通讯机构：
[Yang, Luo] X;Xiangtan Univ, Key Lab Green Organ Synth & Applicat Hunan Prov, Key Lab Environmentally Friendly Chem & Applicat, Coll Chem,Minist Educ, Xiangtan 411105, Hunan, Peoples R China.
摘要：
A convenient Cu-promoted three-component decarbonylative alkylative arylation of terminal alkynes with aliphatic aldehydes and arenes is developed to provide chain elongated tri-substituted olefins with good chemo-, regio- and stereo-selectivities, and is applied to the radical-type decarbonylative coupling of sugar analogs. Readily available aliphatic aldehydes are readily decarbonylated into 1˙, 2˙ and 3˙ alkyl radicals for the construction of a C(sp3)–C(sp2) bond via radical addition, followed by HAS-arylation to form the C(sp2)–C(sp2) bond.
摘要：
An efficient synthetic route to chiral allylic amines has been developed by nickel/(S,S)-Ph-BPE complex catalyzed chemoselective asymmetric hydrogenation of alpha,beta-unsaturated ketoimines. Varieties of alpha,beta-unsaturated ketoimines have been well tolerated in this transformation to give chiral allylic amines with high yields and excellent ee values (up to 99% yield, up to 99% ee). A gram-scale reaction with 0.2 mol % catalyst loading has also been achieved.
通讯机构：
[Deng, GJ; Huang, HW] X;Xiangtan Univ, Minist Educ, Key Lab Environmentally Friendly Chem & Applicat, Coll Chem,Key Lab Green Organ Synth & Applicat Hu, Xiangtan 411105, Peoples R China.
摘要：
A three-component cascade bis-heteroannulation reaction is described that provides access to a variety of benzo[4,5]thieno[3,2-c]isoquinoline and thieno[3,2-c]isoquinoline compounds from easily available methylketoximes, o-halobenzaldehydes, and elemental sulfur. Mechanistic studies reveal a two-step process involving a sequential copper and sulfur catalysis relay.
关键词：
Cobalt oxide;Hexagonal prisms;Pure phase;Anode;Lithium ion battery
摘要：
In this research, we use a modified sol-gel method to obtain a pure phase new hexagonal CoO on reduced graphene oxide by leading of polar solvent. In the electrochemical test, the CoO/rGO composite shows a remarkable performance of capacity as an anode of a lithium ion battery. The electrochemistry performance shows that the capacity of the composite can remain at 1300 mAh/g in 100 cycles without damping. The pure phase of CoO and its hexagonal morphology have been characterized by XRD, SEM and TEM. (C) 2018 Elsevier B.V. All rights reserved.
关键词：
integral equations;Lane-Emden system;conformal invariance;positive solutions;existence
摘要：
This paper is devoted to studying the existence of positive solutions for the following integral system
$$\left\{ {\begin{array}{*{20}{c}}
{u\left( x \right) = \int_{{\mathbb{R}^n}} {{{\left| {x - y} \right|}^\lambda }{v^{ - q}}\left( y \right)dy,} } \\
{v\left( x \right) = \int_{{\mathbb{R}^n}} {{{\left| {x - y} \right|}^\lambda }{u^{ - p}}\left( y \right)dy,} }
\end{array}} \right.p,q > 0,\lambda \in \left( {0,\infty } \right),n \geqslant 1$$
. It is shown that if (u, v) is a pair of positive Lebesgue measurable solutions of this integral system, then
$$\frac{1}{{p - 1}} + \frac{1}{{q - 1}} = \frac{\lambda }{n}$$
, which is different from the well-known case of the Lane-Emden system and its natural extension, the Hardy-Littlewood-Sobolev type integral equations.
期刊：
Journal of Physical Chemistry Letters,2019年10(20):6219-6226 ISSN：1948-7185
通讯作者：
Tang, Jianfeng;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Vasenko, Andrey S.] Natl Res Univ Higher Sch Econ, Moscow 101000, Russia.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Tang, Jianfeng] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
摘要：
Lead halide perovskites constitute a very promising class of materials for a broad range of solar and optoelectronic applications. Perovskites exhibit many unusual properties, and recent experiments demonstrate an unusual temperature dependence of charge carrier lifetimes. Focusing on the all-inorganic CsPbBr3, and using a combination of ab initio nonadiabatic molecular dynamics and time-domain density functional theory, we demonstrate that the unconventional behavior arises because of a highly anharmonic nature of atomic motions in perovskites. As temperature increases, perovskite structure undergoes a notable deformation, reflected in tilting of octahedral units, and experiences large-scale anharmonic movements away from the equilibrium geometry. As a result, the electronic energy gap increases, and phonon-induced loss of coherence within the electronic subsystem accelerates. These two factors slow down nonradiative electron-hole recombination, which constitutes the main limitation on efficiencies of perovskite solar, optical, and electronic devices. The increase of charge carrier lifetimes with temperature is particularly beneficial in applications, because materials heat up, for instance, from sunlight during solar energy harvesting. The behavior of the all-inorganic halide perovskite investigated here is different from that of hybrid organic-inorganic perovskites, which exhibit additional disorder associated with reorientations of the asymmetric organic cations. The reported simulations generate an in-depth understanding of the unusual properties of inorganic perovskites, relevant for photocatalytic, photovoltaic, electronic, and optical applications.
