聚苯乙烯-聚4-乙烯基吡啶两亲嵌段共聚物在CO2膨胀液体中的组装行为

嵌段共聚物的自组装行为和其组装形成的胶束聚集体的形貌因在生物医学、药物传输和催化等方面的潜在应用而引起了科学家们的极大兴趣。本工作报道了利用二氧化碳膨胀液体(CXLs)对嵌段共聚物聚苯乙烯-聚4-乙烯基吡啶(PS-b-P4VP)的自组装聚集体(SAA)进行组装结构调控的初步探索。研究发现利用CXLs的抗溶剂效应可以成功调节共聚物PS-b-P4VP的自组装行为。研究结果表明,CXLs的压力及共聚物的组成是影响SAA结构的主要外部因素,CXLs的抗溶剂效应及其对共聚物溶剂化构型的影响是控制SAA形貌转变的主要内在因素。不同组成的共聚物,在CXLs中其SAA的结构形貌均表现出了对压力的显著响应特性。共聚物PS₁₆₈-b-P4VP₄₂₀的自组装聚集体的结构由常压(0.1 MPa)下以球形胶束为主转变为高压下(6.35 MPa)以互联棒状胶束结构为主,而PS₇₉₀-b-P4VP₂₆₃的SAA结构则由常压下的小型囊泡过渡到6.35 MPa下的大复合囊泡(LCVs)。但是对于PS₁₅₃-b-P4VP₁₅₃₀,随着压力的调节,其SAA的结构由常压(0.1 MPa)下的大复合胶束(LCMs)转变为6.35 MPa下的大复合囊泡(LCVs)。特别是,我们发现在本工作考察的实验条件下,在常规溶剂甲苯中控制SAA结构的主要因素是共聚物的组成;而在CXLs条件下,PS壳链与溶剂CXLs间的接触面积随压力调节而发生的改变,可能是控制SAA形貌转变的主要因素。此外,随着CXLs压力升高而引起的PS与P4VP嵌段间双亲性差别的减小,会引起P4VP核-PS壳的界面间的表面张力发生改变,这也是触发SAA形貌转变的诱因之一。本工作充分显示了CXLs方法有助于可控调节自组装聚集体(SAA)的形貌和组装行为,为研发复合纳米材料开辟了一条崭新的绿色途径。     

Ultrathin Planar Microlens Arrays Based on Geometric Metasurface

Ascribing to the properties of two dimensional parallel focusing and imaging, low propagation loss, integration and miniaturization, microlens array has been widely used in imaging, optical communication, organic light emitting devices, adaptive optics, photolithography, biomedical and other applications. However, the existing traditional microlens array suffers from difficulty in fabrication, large‐thickness, curved surface, non‐uniformity of light spots, or requirement of additional discrete components to control the microlens. Herein, a planar microlens array is experimentally demonstrated based on the geometric metasurface. The single microlens is composed of space‐variant subwavelength metallic gratings with high polarization conversion efficiency and thus exhibits gradient phase distribution. The focused spot diameter of 22.5 μm with radius of 350 μm, focal length of 1 cm and the light spots intensity uniformity of 0.9885 (standard deviation 0.0115) at the focal plane are obtained. Moreover, the broadband property of microlens array is also confirmed. The novel design strategy for microlens array would facilitate the miniaturization of optical devices and be easily integrated in the optical interconnected devices.     

A Novel Fluorescence Sensor Towards Hydrazine in Living Cells

By a simple one-step reaction, a new fluorescein-based probe, 3'-hydroxy-3-oxo-3H-spiro[isobenzofuran-l,9'-xanthen]-6-yl-4-bromobutanoate(FLB), was designed and synthesized. Relative to other cations, anions or amines, the probe exhibited high sensitivity and specificity towards hydrazine with approximate 40-fold fluorescence enliancement at 515 nm. The detection limit(DL) was calculated to be 2.87×10^-8 mol/L, which was about 10 times lower than maximum allowable level of hydraziiie(3.12 ×1mol/L) in drinking water pennitted by the US Environment and Protection Association(EPA). Simultaneously, tlirough mass spectroscopy and proton nuclear magnetic resonance titration, the detection mechanism was further confirmed. Eventually, due to the low cytotoxicity and excellent water solubility, FLB could be employed to detect hydrazine in living cells.     

Paracompact locally Lindelöf spaces and <Emphasis Type=”Italic”>L</Emphasis>-systems

Summary We establish relationships between paracompact locally Lindel&ouml;f spaces and all kinds of spaces with L-systems by means of closed mappings, weakly perfect mappings and quotient mappings. In particular, we obtain some characterizations of paracompact locally Lindel&ouml;f spaces. Interestingly, they are also characterized as weakly perfect inverse images of locally separable metric spaces.     

Multifunctional nanoprobe for cancer cell targeting and simultaneous fluorescence/magnetic resonance imaging

Multifunctional nanoprobes with distinctive magnetic and fluorescent properties are highly useful in accurate and early cancer diagnosis. In this study, nanoparticles of Fe₃O₄ core with fluorescent SiO₂ shell (MFS) are synthesized by a facile improved Stöber method. These nanoparticles owning a significant core-shell structure exhibit good dispersion, stable fluorescence, low cytotoxicity and excellent biocompatibility. TLS11a aptamer (Apt1), a specific membrane protein for human liver cancer cells which could be internalized into cells, is conjugated to the MFS nanoparticles through the formation of amide bond working as a target-specific moiety. The attached TLS11a aptamers on nanoparticles are very stable and can't be hydrolyzed by DNA hydrolytic enzyme in vivo. Both fluorescence and magnetic resonance imaging show significant uptake of aptamer conjugated nanoprobe by HepG2 cells compared to 4T1, SGC-7901 and MCF-7 cells. In addition, with the increasing concentration of the nanoprobe, T₂-weighted MRI images of the as-treated HepG2 cells are significantly negatively enhanced, indicating that a high magnetic field gradient is generated by MFS-Apt1 which has been specifically captured by HepG2 cells. The relaxivity of nanoprobe is calculated to be 11.5 mg⁻¹s⁻¹. The MR imaging of tumor-bearing nude mouse is also confirmed. The proposed multifunctional nanoprobe with the size of sub-100 nm has the potential to provide real-time imaging in early liver cancer cell diagnosis.     

A new type of minimal thinness with respect to the stationary Schrödinger operator and its applications

In this paper we define a new type of minimal thinness with respect to the stationary Schrödinger operator at a fixed Martin–Sch boundary point of a cylinder. We also discuss some criteria for it.     

Morphology mediation of MoS_2 nanosheets with organic cations for fast sodium ion storage

Ion diffusion kinetics,depending on the size,tortuosity,connectivity of the channels,greatly affects the rate performance of the electrodes.Two-dimensional materials(2DMs) has emerged as promising electrode materials in the past decades.Howeve r,the applications of 2DMs electrodes are limited by the strong restacking problem,which leads to a poor rate capability.In this work,we for the first time mediated the mo rphology of molybdenum disulfide(MoS_2) nanosheets via a facile coagulation method;abundant sheet crumples were induced,which greatly enhance their surface accessibility and thus benefit the ion diffusion kinetics.Consequently,the crumpled-MoS_2 electrodes follow a capacitive Na-ion charge-storage mechanism to a large extent.Importantly,we demonstrate the special role of organic cations in the inter-sheet assembly configuration,in sharp contrast with that of alkali/alkaline-earth ones.We propose that organic cations cause edge/face contact of the sheets,instead of the face/face contact,thus affording a house-of-cards structure.     

半导体纳晶能级结构与电子性质的电化学研究

了解半导体纳晶能级结构特征和电子特性是其在光电子器件中应用的基础,电化学循环伏安技术提供了一种获取上述关键信息的有效途径。本文系统介绍了利用循环伏安技术探测纳晶能级结构与电子性质的原理、方法以及局限;在此基础上,着重从纳晶能级结构与电子性质的影响因素及规律、纳晶电荷输运性质、纳晶电化学反应机理等方面,综述了该方向近年来取得的研究进展;最后指出了目前研究中存在的问题,并预测了今后的发展方向。     

关于局部可数网与ss映射

本文建立了度量空间在几类序列覆盖ss映射下象空间的特征,讨论了局部可数集族与局部可数基（弱基）之间的相互关系,特别地证明了几类具有特定性质的局部可数网的正则空间与度量空间的几类序列覆盖ss映象之间相互等价,回答了Tanaka提出的一个问题．     

低温热泵蒸发器结霜特性实验的研究

实验研究了不同的空气参数如空气相对湿度、温度以及空气流速对低温热泵室外侧蒸发器结霜特性的影响。研究发现空气入口相对湿度等参数对蒸发器结霜以及换热性能有很大的影响。实验结果可以为热泵除霜以及翅片管式蒸发器优化设计提供可靠的实验依据。