NIR light and enzyme dual stimuli‐responsive amphiphilic diblock copolymer assemblies

Using atom transfer radical polymerization (ATRP) and macromolecular azo coupling reaction, both o‐nitrobenzyl (ONB) group and azobenzene group were efficiently incorporated into the center of the amphiphilic diblock copolymer chain. The prepared diblock copolymer was well characterized by UV–vis, ¹H NMR, and GPC methods. Self‐assembly of the amphiphilic copolymer in selected solvents can result in uniform self‐assembly aggregates. In the presence of external stimuli [upconversion nanoparticles (UCNPs)/NIR light or enzyme], the amphiphilic diblock copolymer chain could be broken by the cleavage of ONB or azobenzene group, which would lead to the disruption of the self‐assembly aggregates. This photo‐ and enzyme‐triggered disruption process was proved by using transmission electron microscopy (TEM) and GPC method. Fluorescence emission spectra measurements indicated that the release of Nile red, a hydrophobic dye, encapsulated by the self‐assembly aggregates, could be successfully realized under the NIR light and enzyme stimuli. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2450–2457     

Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine

A new, convenient and efficient AgNO₃‐catalyzed strategy for the preparation of 2‐(benzo[d]azol‐2‐yl)phenol derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO₃ as a readily available and low‐cost benign oxidant at low catalyst loadings with excellent functional group tolerance.     

An Atomically Precise Au10Ag2 Nanocluster with Red–Near‐IR Dual Emission

A red–near‐IR dual‐emissive nanocluster with the composition [Au₁₀Ag₂(2‐py?C≡C)₃(dppy)₆](BF₄)₅ ( 1 ; 2‐py?C≡C is 2‐pyridylethynyl, dppy=2‐pyridyldiphenylphosphine) has been synthesized. Single‐crystal X‐ray structural analysis reveals that 1 has a trigonal bipyramidal Au₁₀Ag₂ core that contains a planar Au₄(2‐py?C≡C)₃ unit sandwiched by two Au₃Ag(dppy)₃ motifs. Cluster 1 shows intense red–NIR dual emission in solution. The visible emission originates from metal‐to‐ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au₃Ag(dppy)₃ motifs, and the intense NIR emission is associated with the participation of 2‐pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time‐dependent density functional theory (TD‐DFT) calculation.     

Morphology–luminescence correlations in europium-doped ZnO nanomaterials

In order to investigate the correlations of morphologies and optical properties, different morphologies of Eu-doped ZnO were synthesized by different methods. Specifically, the structure of SiO₂/ZnO:Eu nanoflower was synthesized for the first time and has not been reported previously. One percent was chosen as the Eu doping concentration. The relations of the morphology, diameter, and uniformity with the PL intensity were examined. The PL intensity of ZOE samples has a close relationship with the morphology. The PL intensity order of the different morphologies of ZnO:Eu is as follows: nanorod arrays > thin film > nanospheres > nanoparticles > nanoflowers > nanorods. The PL intensity of nanomaterials is larger, if the diameter of the nanomaterials is larger. However, the size of diameter is not the most important reason. It was found that the sample uniformity plays a key role on ZnO:Eu PL intensity. ZnO:Eu with small particle diameters may have strong photoluminescence intensity, if the nanoparticles are uniform.     

一类带有非线性阻尼项和源项的四阶波动方程整体解的存在性与不存在性

考虑一类带有非线性阻尼项和源项的四阶波动方程的初边值问题.通过结合Galerkin逼近,势井方法和单调紧致方法,在最少的先验估计下获得了整体解的存在性.此外,在初始能量为负的情况下,证明了存在有限时间内爆破的解.     

一类非光滑对称三次系统的全局分支

该文对一类对称三次Hamilton系统在非光滑对称摄动下产生的极限环数目进行研究.通过多参数摄动理论和定性分析方法,得到这类在非光滑摄动下的三次系统可以存在至少19个极限环.     

Pesticide‐conjugated polyacrylate nanoparticles: novel opportunities for improving the photostability of emamectin benzoate

Emamectin benzoate, a macrocyclic lactone, can be used in low quantities to control arthropod pests, effectively. However, its poor photostability prevents its further use. To delay its photodegradation, novel acrylate‐type polymeric nanoparticles were synthesized and tested as materials for improving pesticide photostability. N‐acylated emamectin benzoate was synthesized via bonding emamectin benzoate to acrylamide. The resulting pesticide, containing the double bond linkage –C=C–N–, was copolymerized with butyl acrylate and methyl methacrylate by the emulsion polymerization method. The refined polymers were characterized by Fourier transform infrared spectroscopy spectroscopy, and result illustrated the pesticide was conjugated to the polymers. Atomic force microscope and dynamic light scattering analyses were also used for determining the average particle diameters of pesticide–polymer conjugates. Photostability tests showed that the nanoparticles obtained exhibited greatly improved photostability. Additionally, the laboratory toxicity tests demonstrated that the insecticidal effects of the novel emamectin benzoate formulation were better than those of the control pesticide formulation (emamectin benzoate EC). Copyright © 2012 John Wiley & Sons, Ltd.