一些层状纳米复合材料的制备和应用

无机层状化合物因其层间离子的可交换性而受到人们广泛的关注,通过功能性客体分子的插层,所得层状纳米复合材料具有独特的物理与化学性质,在催化、医药、电化学和生物传感、离子交换和吸附以及光学等方面具有广泛而重要的应用,已成为当前材料研究领域中的前沿和热点。本文主要综述了近年来有关层状纳米复合材料的制备和应用的最新研究进展。     

The closures of (U+K)-orbits of essentially normal triangular operator models

The (U + K)-orbit of a bounded linear operator T acting on a Hilbert space H is defined as (U + K)(T)={R-1 T R:R is invertible of the form unitary plus compact on H}.In this paper,we first characterize the closure of the (U + K)-orbit of an essentially normal triangular operator T satisfying H={ker(T-λI):λ∈ρ F (T)} and σ p (T*)=ф.After that,we establish certain essentially normal triangular operator models with the form of the direct sums of triangular operators,adjoint of triangular operators and normal operators,show that such operator models generate the same closed (U + K)-orbit if they have the same spectral picture,and describe the closures of the (U + K)-orbits of these operator models.These generalize some known results on the closures of (U + K)-orbits of essentially normal operators,and provide more positive cases to an open conjecture raised by Marcoux as Question 2 in his article "A survey of (U + K)-orbits".     

Approximation of functions on the Sobolev space with a Gaussian measure

We discuss the best approximation of periodic functions by trigonometric polynomials and the approximation by Fourier partial summation operators, Valle-Poussin operators, Ces`aro operators, Abel opera-tors, and Jackson operators, respectively, on the Sobolev space with a Gaussian measure and obtain the average error estimations. We show that, in the average case setting, the trigonometric polynomial subspaces are the asymptotically optimal subspaces in the L q space for 1≤q ∞, and the Fourier partial summation operators and the Valle-Poussin operators are the asymptotically optimal linear operators and are as good as optimal nonlinear operators in the L q space for 1≤q ∞.     

Graphene-Gold Nanoparticle-modified Electrochemical Sensor for Detection of Kanamycin Based on Target-induced Aptamer Displacement

A highly sensitive and selective label-free electrochemical sensor was developed for the determination of kanamycin. To improve the sensitivity of the electrochemical sensor, graphene-gold nanoparticles were prepared by a one-step electrochemical coreduction process and were modified on the surface of a glassy carbon electrode. The double-stranded DNA(ds-DNA) duplex probe was immobilized onto the graphene-gold nanoparticle-modified electrode. The introduction of target kanamycin induced the displacement of aptamer from the ds-DNA duplex into the solution. Methylene blue(MB) as a redox indicator monitored the current change using differential pulse voltammetry. Under optimal conditions, the designed electrochemical aptasensor exhibited a wide linear range from 0.1 pmol/L to 10 pmol/L with a detection limit of 0.03 pmol/L for kanamycin. The experimental strategy enabled the direct analysis of milk samples, and the results showed high sensitivity and good selectivity.     

树状桥联半受阻酚类抗氧剂的合成与抗氧化性能

从端基为胺基树状大分子出发, 合成了一种具有多个半受阻酚抗氧化基团、 结构对称的树状桥联半受阻酚类抗氧剂. 元素分析、 傅里叶变换红外光谱(FTIR)、 氢核磁共振波谱(¹H NMR)、 质谱(MS)和冰点降低法证实合成的树状桥联半受阻酚类抗氧剂的化学结构与理论结构一致, 纯度较高. 采用1,1-二苯基-2-苦基肼(DPPH)法和差热扫描量热(DSC)法研究了树状桥联半受阻酚类抗氧剂的抗氧化性能, 并与相应的树状桥联全受阻酚类抗氧剂进行了对比. 研究结果表明, 树状桥联半受阻酚类抗氧剂清除DPPH自由基的活性不仅与清除体系中抗氧剂的浓度有关, 而且与清除时间有关; 清除时间为30 min时的抗氧化能力是清除时间为400 min时抗氧化能力的近2倍. 树状桥联半受阻酚类抗氧剂的半受阻效应使其在DPPH体系和HDPE树脂中的抗氧化能力均优于其相应的树状桥联全受阻酚类抗氧剂.     

Preparative separation of isoquinoline alkaloids from Corydalis impatiens using a middle‐pressure chromatogram isolated gel column coupled with two‐dimensional liquid chromatography

We established a two‐dimensional strong cation exchange/reversed‐phase liquid chromatography protocol to isolate and purify isoquinoline alkaloids from Corydalis impatiens. Isoquinoline alkaloids were first enriched from a C. impatiens extract in which liposoluble components were removed using a medium‐pressure chromatographic tower containing middle chromatogram isolated gel. A strong cation exchange column was employed to separate and obtain 30 fractions. We chose fractions 22–29 for reversed‐phase liquid chromatography purification using characteristic isoquinoline alkaloid ultraviolet absorption spectra. Several isoquinoline alkaloid fractions (22–29) were further separated, and those of low resolution were isolated via two‐dimensional liquid chromatography in the orthogonal plane. A total of eight novel isoquinoline alkaloids with characteristic ultraviolet spectra were obtained from C. impatiens. We thus demonstrate the benefits of off‐line two‐dimensional strong cation exchange/reversed‐phase liquid chromatography to isolate isoquinoline alkaloids from C. impatiens.     

Supramolecular gelator based on a [c2]daisy chain rotaxane: efficient gel-solution transition by ring-sliding motion

A supramolecular gelator based on the bistable [c2]daisy chain rotaxane is designed and synthesized. The reversible actuation of the [c2]daisy chain renders the formed supramolecular gel with acid/base-responsive switching between gel and monomer solution. The efficient switching process is attributed to the ring-sliding effect of the rotaxane in response to acid/base stimuli.The ring-inhibited hydrogen bonding stacking results in a nearly quantitatively disassembly of the gel network after addition of base which is hard to be realized by traditional heating strategy in hydrogen-bonding-supported gel.     

浙江西北部山地暴雨特征

利用2005-2017年14个自动气象站和2015-2017年66个自动气象站的降水资料,对浙西北暴雨的时空分布特征进行了分析,发现浙西北雨量分布呈西南、东北多,中部、东部少的特征,有2个暴雨中心,一个是位于清凉峰到大明山一带的梅汛期暴雨中心,另一个为天目山北部市岭一带的台风暴雨中心;暴雨存在明显的月、日变化特征,7-8月暴雨最多,春雨期暴雨主要出现在日落后,梅雨期主要出现在早晨前后,其次是午后,盛夏时主要出现在午后;6月前暴雨集中在西部、南部,7月出现明显转折,西南暴雨迅速减少,东北部天目山市岭一带暴雨明显增多。市岭地形为东北-西南河谷型,受狭管效应和地形抬升的影响,当台风位于天目山东南部时,天目山一带吹东北风对降水增幅最明显。     

蛋氨酸衍生物的合成及其缓蚀性能研究

本文合成了一种新型蛋氨酸衍生物酸洗缓蚀剂,运用红外光谱及核磁共振氢谱对其结构进行了鉴定。采用失重法和电化学法研究了在0. 5mol·L~(-1)硫酸介质中其对碳钢试片的缓蚀性能,并通过吸附等温模型对缓蚀机理进行初步的探讨。结果表明,蛋氨酸衍生物的缓蚀效率约为90%,整体用量适中,是一种有望得到良好应用的绿色缓蚀剂。电化学分析表明,蛋氨酸衍生物为混合型缓蚀剂,其通过增大金属表面的电荷转移电阻而降低电化学腐蚀速率。     

表面覆膜波导光栅共振光谱特性及传感机理分析

基于波导光栅共振原理和古斯-汉欣(Goos-Hänchen)位移理论,提出一种表面覆膜波导光栅传感结构,并研究其共振光谱特性。通过在光栅表面涂覆低折射率聚合物功能膜层优化其共振光谱特性,选用多孔硅作为待测物承载单元,可以使光学探针更充分地接触待测样本,从而提高其检测性能。根据波导光栅共振相位条件,建立了共振波长和样本折射率之间的数学模型,通过检测共振位置的改变进而对样本浓度进行检测。研究表明,该表面覆膜波导光栅传感结构具有线型对称和窄线宽的共振光谱特性,可实现高品质因数(Q值)和高灵敏度的传感特性,其Q值为1 488,对折射率的检测极限可达5×10-4 RIU(RIU为折射率单位)。通过检测不同浓度的葡萄糖溶液对其传感特性进行验证分析,结果表明,共振波长与葡萄糖溶液浓度之间具有良好的线性关系,对葡萄糖溶液的检测灵敏度为1.12nm/1%,证明了该表面覆膜波导光栅传感结构的有效性,可以用于对低浓度样本溶液的实时动态监测,并为波长调制型光学折射率传感器的研究提供理论指导。