A Green and Wide-Scope Approach for Chiroptical Sensing of Organic Molecules through Biomimetic Recognition in Water

Optical chirality sensing has attracted a lot of interest due to its potential in high-throughput screening in chirality analysis. A molecular sensor is required to convert the chirality of analytes into optical signals. Although many molecular sensors have been reported, sensors with wide substrate scope remain to be developed. Herein, we report that the amide naphthotube-based chirality sensors have an unprecedented wide scope for chiroptical sensing of organic molecules. The substrates include, but are not limited to common organic products in asymmetric catalysis, chiral molecules with inert groups or remote functional groups from their chiral centers, natural products and their derivatives, and chiral drugs. The effective chirality sensing is based on biomimetic recognition in water and on effective chirality transfer through guest-induced formation of a chiral conformation of the sensors. Furthermore, the sensors can be used in real-time monitoring on reaction kinetics in water and in determining absolute configurations and ee values of the products in asymmetric catalysis.     

Ultrathin films of functionalised single-walled carbon nanotubes: a potential bio-sensing platform

ABSTRACT

The Langmuir monolayer is a special class of lyotropic liquid crystalline system wherein phase transition essentially depends on surface density, temperature and ion-content in the aqueous medium. The variety of surface phases can be transferred onto devices by the Langmuir–Blodgett (LB) technique. The Langmuir monolayer of pristine single-walled carbon nanotubes (SWCNTs) exhibited gas and liquid-like phases. The LB film of SWCNTs shows target surface pressure dependent interesting morphologies. The methane gas sensing using parallel alignment of SWCNTs was found to be better than that of randomly oriented SWCNTs. The SWCNTs can be functionalised chemically to enhance the ease of film processability and affinity towards analytes. These are essential parameters for the development of a sensor. In this article, we present our work on Langmuir monolayer and LB films of octadecylamine functionalised SWCNTs (ODACNTs) and its sensing application towards bio-analytes, e.g. L-aspartic acid and bovine serum albumin. The sensing performance of LB film of ODACNTs was compared with that of spin-coated films of ODACNTs. The sensing performance of LB films of ODACNTs indicated a potential platform for bio-sensing application.     

Ratiometric Detection of ATP by Fluorescent Cyclophanes with Bellows-Type Sensing Mechanism

Pyrene-based cyclophanes have been synthesized with the aim to realize a bellows-type sensing mechanism for the ratiometric detection of nucleotide concentrations in a buffered aqueous solution. The sensing mechanism involves the encapsulation of a nucleobase between two pyrene rings, which affects the monomer-excimer equilibrium of the receptor in the excited state. The nature of the spacer and its connection pattern to pyrene rings have been varied to achieve high selectivity for ATP. The 1,8-substituted pyrene-based cyclophane with the 2,2’-diaminodiethylamine spacer demonstrates the best selectivity for ATP showing a 50-fold increase in the monomer-excimer emission ratio upon saturation with the nucleotide. The receptor can detect ATP within the biological concentrations range over a wide pH range. NMR and spectroscopic studies have revealed the importance of hydrogen bonding and stacking interactions for achieving a required receptor selectivity. The probe has been successfully applied for the real-time monitoring of creatine kinase activity.     

纳通道的物质传输特性及应用

近年来,随着材料科学、微纳加工技术和微纳尺度物质传输理论的发展,纳通道技术得到了越来越多的研究和关注。纳通道包括生物纳通道和人工纳通道,其孔径通常为1~100 nm。在这一尺度下,通道表面与通道内物质之间的作用概率大大增强,使得纳通道表现出许多与宏观体系不同的物质传输特性,例如通道表面电荷与通道内离子之间的静电作用产生了离子选择性,通道内电化学势的不对称分布产生了离子整流特性,物质传输过程中占据通道产生了阻塞脉冲特性等。纳通道中的这些物质传输特性在传感、分离、能源等领域具有广泛应用,例如通过对纳通道进行功能化修饰可以实现门控离子传输;利用亚纳米尺度的通道可以实现单分子传感;利用通道与传输物质之间的相互作用可以实现离子、分子、纳米粒子的分离;利用纳通道的离子选择性可以在通道内实现电荷分离,将不同形式的能量（如光、热、压力、盐差等）高效转化为电能。纳通道技术是化学、材料科学、纳米技术等多学科的交叉集合,在解决生物、环境、能源等基本问题方面具有良好的前景。该文综述了近10年来与纳通道物质传输理论以及纳通道技术应用相关的前沿研究,梳理了纳通道技术的发展过程,并对其在各个领域的应用进行了总结与展望。     

Single‐Molecule Sensing of Environmental pH—an STM Break Junction and NEGF‐DFT Approach

Sensors play a significant role in the detection of toxic species and explosives, and in the remote control of chemical processes. In this work, we report a single‐molecule‐based pH switch/sensor that exploits the sensitivity of dye molecules to environmental pH to build metal–molecule–metal (m‐M‐m) devices using the scanning tunneling microscopy (STM) break junction technique. Dyes undergo pH‐induced electronic modulation due to reversible structural transformation between a conjugated and a nonconjugated form, resulting in a change in the HOMO–LUMO gap. The dye‐mediated m‐M‐m devices react to environmental pH with a high on/off ratio (≈100:1) of device conductivity. Density functional theory (DFT) calculations, carried out under the non‐equilibrium Green’s function (NEGF) framework, model charge transport through these molecules in the two possible forms and confirm that the HOMO–LUMO gap of dyes is nearly twice as large in the nonconjugated form as in the conjugated form.     

Supramolecular Luminescent Lanthanide Dimers for Fluoride Sequestering and Sensing

Lanthanide complexes (Ln=Eu, Tb, and Yb) that are based on a C₂‐symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/Vis absorption, luminescence, and NMR spectroscopy and high‐resolution mass spectrometry. The X‐ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the Eu? F? Eu bridging motive, π stacking interactions, and a four‐component hydrogen‐bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nM .     

基于特征结构相似度的遥感影像融合质量评价指标

在分析现有影像融合评价指标的基础上,根据人眼视觉特性,提出一种基于特征结构相似度的遥感影像融合评价指标.首先从原始影像和融合影像中提取空间特征和光谱特征,然后综合计算空间特征和光谱特征的结构相似度作为评价指标,达到评价影像质量的目的.通过对多种传感器获取的遥感影像进行融合实验,结果表明该客观评价方法与主观评价结果一致,...     

基于小波域马尔可夫随机场模型的压缩传感图像重构

目前在压缩传感重构算法中利用图像的可稀疏性表示先验知识,从比奈奎斯特采样少得多的观测值中恢复原始图像。除了稀疏性之外,邻域系数的相关性也可以作为先验知识加速重构算法收敛。为了克服目前算法中没有利用邻域系数相关性的缺点,提出了基于小波域马尔可夫随机场模型的压缩传感图像重构算法,根据显著性度量对变换系数进行分类得到具有马尔可夫性的初始掩模,利用ICM算法完成掩模优化,实现系数更新,并将算法与未考虑邻域相关性的算法进行了比较。实验结果证明了算法的有效性。     

Adsorption-controlled transition of the electrical properties realized in Hematite（alpha-Fe2O3） nanorods ethanol sensing

Alpha-Fe2O3 nanorods are synthesized through a hydrothermal method with no surfactant introduced and ethanol sensors are fabricated from these nanorods.The device can respond to ethanol vapour in a concentration range from 1 to 1500 parts per million and shows both p-type and n-type responding characteristics during the investigation of the ethanol sensing.The sensor displays a p-type characteristic when the ethanol concentration is low and converted into an n-type characteristic as the concentration exceeds a certain value.Such a phenomenon is attributed to the chemisorbed oxygen,which leads to different modifications of the energy band at the surface,namely,depletion layer or inversion layer.     

条形码技术在方志馆典藏工作中的应用

条形码技术是一种应用广泛的光电数据输入技术,具有编码、数据识别、数据采集、条码印刷等多项功能。本文简述了条形码技术的原理及其在方志馆编录、典藏、流通环节中的作用。论述了二维码技术的应用对方志馆在馆藏资料自动化管理和方志馆数字化建设方面产生的革命性影响。