Manipulation and control of a single molecular rotor on Au(111) surface

Three different methods are used to manipulate and control phthalocyanine based single molecular rotors on Au （111） surface： （1） changing the molecular structure to alter the rotation potential; （2） using the tunnelling current of the scanning tunnelling microscope （STM） to change the thermal equilibrium of the molecular rotor; （3） artificial manipulation of the molecular rotor to switch the rotation on or off by an STM tip. Furthermore, a molecular ＇gear wheel＇ is successfully achieved with two neighbouring molecules.

Hierarchical Self-assembly of Atomically Precise Au Nanoclusters with Molecular Rotor-based Ligands

The hierarchical assemblies of precise nanoparticles(NPs)have created materials with emergent properties and functionalities.However,the complex assemblies remain unclear at a precise scale.Here,we show the hierarchical self-assembly of atomically precise gold nanoclusters(Au NCs)with molecular rotor-based ligands(MRL),featuring a double-layer surface.Compared to two other types of monolayer-protected(MLP)Au NCs,the significantly reduced surface density for MRL Au NCs profoundly influences their assembly behavior within the lattice.Furthermore,the long length of rotor-based ligands and the rotational freedom of the phenyl-rings of rotor-based ligands also facilitate the assembly of NCs.Our works elucidate the hierarchical assembly on a precise scale,suggesting that the rotor-based ligand’s strategy offers promising potential for designing well-defined and more complex structures in supercrystals.

Thermal-induced reversible ferroelastic phase transition in a new bromethyl-substituted molecular rotor

A new bromethyl-substituted molecular rotor, [Cu（dabcoCH2Br）（H2O）Br3] （dabcoCH2Br＋=1-（2-bromethyl）-1,4-diazoniabi- cyclo[2.2.2]octane cation）, which belongs to a family of balomethyl-substituted molecular rotors, was synthesized and struc- turally characterized. The reversible phase transition at ca. 250 K was well established for this molecular rotor by thermal analyses, variable-temperature X-ray diffraction, and variable temperature dielectric measurements. The order-disorder trans- formation of the rotator part （dabco moiety） causes ferroelastic phase transition with an Aizu notation of mmmF2/m from high- temperature orthorhombic phase （Pbnm） to low-temperature monoclinic phase （P21/n）. More important, in reference to the density functional theory calculations and structural analyses, the key factors to tune the phase transition behaviors were dis- cussed in detail for this family of halomethyl-substituted molecular rotors.

A Crystalline Supramolecular Rotor Functioned by Dual Ultrasmall Polar Rotators

As an extended model of conventional molecular rotors,a conceived construction of novel crystalline molecular rotor that simultaneously contains two discrete polar rotators is presented here.The supramolecular self-assembly of 18-crown-6 host and two rotator-containing ion-pair guests affords a three-in-one cocrystal,(2-NH_(3)-iBuOH)(18-crown-6)[ZnBr_(3)(H_(2)O)],in which the hydroxyl group and aqua ligand both function as ultrasmall polar rotators.On the basis of the variable-temperature single-crystal X-ray diffraction,variable-temperature/frequency dielectric response,density functional theory calculations,and molecular dynamics simulations,it is found that such dual polar rotators experience a gradually enhanced rotation with increasing temperature,and more importantly,could be controlled by a reversible polar-to-polar structural phase transition,i.e.,from a“single-(polar rotator)”state at low-temperature phase to a“mixed-dual-(polar rotator)”state in the vicinity of transition,and to an unusual“synchronized-dual-(polar rotator)”state at high-temperature phase.

Molecular rotors as a class of generally highly active ion transporters

We describe here a class of unconventional ion transporters,molecular rotors that transport ions through a rotating function rather than via traditional carrier or channel mechanisms.Mimicking macroscopic rotors,these molecular rotors consist of three modularly tunable components,i.e.,a membrane-anchoring stator,a crown ether-containing rotator for ion binding and transport,and a triple bond-based axle that allows the rotator to freely rotate around the stator in the lipid membrane.Lipid bilayer experiments reveal the generally high ability of all molecular rotors in promoting the highly efficient transmembrane K^(+)flux(EC50 values=0.49-1.37 mol%relative to lipid).While molecular rotors differing only in the ion-binding unit exhibit similar ion transport activities,those differing in the rotator’s length display activity differences by up to 174%.

Fluorescence lifetime imaging of molecular rotors to map microviscosity in cells

Fluorescence liftime imaging （FLIM） of modified hydrophobic bodipy dyes that act as fluorescent molecular rotors shows that the fluorescence lifetime of these probes is a function of the microviscosity of their environment. Incubating cells with these dyes, we find a punctate and continuous distribution of the dye in cells. The viscosity value obtained in what appears to be endocytotic vesicles in living cells is around 100 times higher than that of water and of cellular cytoplasm.Time-resolved fluorescence anisotropy measurements also yield rotational correlation times consistent with large microviscosity values. In this way, we successfully develop a practical and versatile approach to map the microviscosity in cells based on imaging fluorescent molecular rotors.

分子筛转轮与转筒在废气治理工程中的应用分析

大部分挥发性工业有机废气呈大风量、低浓度的特点,需要经过分子筛转轮或转筒吸附浓缩才能达到降低设备投资和节约能耗的目的。文章分析了市面上常见的分子筛转轮与转筒,分别从设备结构、投资、运行特点、能耗、安全性、吸附材料性能等方面进行了对比,并对吸附浓缩装置的选择给出了合理的建议。

基于有限元方法的涡轮分子泵转子系统模态分析

以FB-一1500型涡轮分子泵为分析原型，依据分子泵转子系统形状、尺寸、材料、支承形式以及质量分布，建立了分子泵转子系统几何模型．采用有限元方法对转子系统进行模态分析，获得了转子系统的临界转速和振型．模态分析结果表明：泵运行在5～6阶固有频率之间，但未完全满足柔性转子安全设计要求，仍然存在安全隐患．提出改进转轴惯性矩、轴承支撑位置来提高转子系统的固有频率，以确保分子泵的安全运行．获得的转子系统模态，对涡轮分子泵启动加速和停车减速过程控制策略制定、减弱或回避共振带来的安全隐患、提高分子泵使用寿命具有参考价值．

分子泵转子多学科设计优化技术

转子是分子泵的关键部件,其结构参数的设计需要从抽气性能、转子动力学和强度等方面综合考虑,经过多次迭代才能满足要求,设计过程很复杂。本文采用多学科设计优化理念,基于优化总控软件平台,开发了应用接口软件,集成UG NX、ANSYS、MATLAB等软件,实现抽气性能计算、参数化几何建模、转子动态特性分析、应力与应变计算等功能模块的数据共享和优化迭代,对转子的结构参数进行自动优化,得到了优化的转子结构参数,为高质量、高效率开发系列化分子泵产品提供了技术支撑。

自抽真空飞轮储能装置的数值模拟与实验研究

针对盘式电机型飞轮储能装置的飞轮风损情况,采用自抽真空飞轮储能装置来减少飞轮风损,设计了飞轮储能装置的内置分子泵,再用计算流体动力学法模拟内置分子泵转子螺旋槽内的气体粘滞流、滑移流,分析其抽真空性能,最后进行自抽真空方式与普通外置真空系统对飞轮储能装置抽真空时间对比。结果表明:自抽真空飞轮储能装置的内置分子泵螺旋槽入口与出口总存在压力差,在12 000 r/min～60 000 r/min范围内抽真空性能较好,达到0.01 Pa所需时间仅为外置真空系统抽气时间的1/20左右,表明此装置抽气时间短并切实可行。

分子泵叶轮装配过盈量设计与应力分析

动叶轮作为分子泵的关键部件,与芯轴过盈装配,要求在高速状态下仍保持一定的过盈量。本文计算了动叶轮在高速转动时的径向变形、过盈装配时的初始应力状态和转动时应力状态,根据径向变形量的差异和应力优化了装配过盈量,既保证了动叶轮转子强度又使过盈联接可靠。

涡轮转子叶片对称加工用双主轴铣削机床

为了提高磁悬浮分子泵中硬铝合金整体涡轮转子叶片的加工效率,提出了一种新型的双主轴卧式铣削机床结构。通过介绍其他典型类型机床加工整体涡轮转子叶片的特点,阐述了这种新型机床加工硬铝合金整体涡轮转子叶片的特性及对称加工的实现方法。新型双主轴卧式铣削机床使硬铝合金整体涡轮转子叶片的加工效率理论上可提高近一倍,并且由于分度误差累积的减小使其加工精度相对提高。同时,与购买两台传统机床相比能够降低设备成本。

复杂支承条件下分子泵转子动力学特性数值模拟与实验研究

为了有效提高复合分子泵转子系统的振动抑制效果,围绕与其密切相关的支承结构刚度特性展开研究。首先针对分子泵两端复杂支承条件,采用实验方法研究永磁轴承和橡胶减振垫的刚度特性;然后基于支承刚度特性建立分子泵转子系统数值模拟模型,采用模态分析法求解转子系统的特征频率及对应振型,采用谐频响应分析法求解转子系统在最大不平衡响应;最后搭建实验平台测试分子泵系统的振动特性。实验结果表明:所建立的数值模拟模型能够较好地预测分子泵转子系统的振动特性,合理设计分子泵支承结构能够有效提高分子泵转子系统的振动抑制效果。

分子蒸馏装置中刮膜器对液膜流动状况的影响研究

分子蒸馏是一种高效的液体分离技术,在工业生产领域具有广泛的应用前景。为了探究设备中液膜的流动状况,今使用计算流体力学软件FLUENT 6.3对刮膜式分子蒸馏过程进行模拟,分别考察了刮膜器的形状、转子转速、转子半径、转子与壁面间的缝隙等因素对不同黏度流体的液膜均匀程度和湍流程度的影响。结果表明圆形转子和倾斜刮板有助于液体在蒸发壁面上形成均匀分布的薄膜,因此更适用于分子蒸馏过程;转子的结构参数对高黏度物料的流动状况的影响更为显著,在一定范围内高黏度物料的均匀度和湍流度都随转子半径和缝隙的增大而增大。研究的模拟结果对分子蒸馏过程具有深刻的理论意义和实际指导意义,为刮膜式分子蒸馏装置的设计提供了参考。

Adsorption and rotational barrier for a single azobenzene molecule on Au(111)surface

The orientation switching of a single azobenzene molecule on Au(111)surface excited by tunneling electrons and/or photons has been demonstrated in recent experiments.Here we investigate the rotation behavior of this molecular rotor by first-principles density functional theory(DFT)calculation.The anchor phenyl ring prefers adsorption on top of the fcc hollow site,simulated by a benzene molecule on close packed atomic surface.The adsorption energy for an azobenzene molecule on Au(111)surface is calculated to be about 1.76 eV.The rotational energy profile has been mapped with one of the phenyl rings pivots around the fcc hollow site,illustrating a potential barrier about 50 meV.The results are consistent with experimental observations and valuable for exploring a broad spectrum of molecules on this noble metal surface.

飞秒激光结合啁啾太赫兹脉冲控制CO分子取向

为了研究啁啾太赫兹脉冲诱导后的CO分子取向,采用刚性转子近似求解含时薛定谔方程的方法,进行了理论分析和数值仿真。为了在较低太赫兹场强时获得较好的取向效果,采用了飞秒激光结合啁啾太赫兹脉冲的方案。结果表明,分子取向程度可增强81%。在有限温度条件下,飞秒激光结合啁啾太赫兹脉冲诱导分子取向的效率随温度的升高而降低;相对于少周期太赫兹脉冲,啁啾太赫兹脉冲有诱导分子取向的优越性。这一结果对提高CO分子取向程度是有意义的。

光驱动单向分子转子的研究进展

分子转子是分子马达设计的要件,有关分子转子的讨论已经引起广泛的关注.主要介绍2003年以来单向转动型分子转子的研究状况,重点讨论其构效关系和应用方面的最新进展,展望了分子转子的发展前景并指出其面临的挑战.

红光发射分子转子的设计与合成

粘度对细胞微环境的维持非常重要。检测细胞内的粘度一般采用分子转子,而目前大多数的分子转子发射波长较短,不利于生物成像,为此我们设计了基于扭转分子内电荷转移(TICT)机理,通过共轭双键连接吸电子基和给电子基的红光发射的分子转子2-(2-(4-氨基苯乙烯基)-4-H-吡喃-4-亚基)-丙二腈(DCM-NH_2)。DCM-NH_2的最大发射波长为631 nm,属于远红光,能有效减少生物背景,提高成像信噪比。该探针对粘度有很好的响应,具有非常宽的线性响应范围(0.6~458.6 c P),同时也具有较高的灵敏度。

挤压改性对菠萝蜜种子淀粉精细结构的影响

以菠萝蜜种子为原料提取淀粉,利用双螺杆挤压机通过控制挤压操作参数对淀粉进行改性,并对挤出物进行分子量分布和链长分布实验。结果表明:挤压改性后的菠萝蜜种子淀粉对比原淀粉重均分子量和数均分子量均降低,平均回旋半径减少,链长分布中A链和B1链的比例变大,B2链和B3+链比例变小;随着机筒温度和螺杆转速的增加,重均分子量和数均分子量显著降低,A链比例显著增加,B1、B2和B3+链比例显著减少,表明挤压改性菠萝蜜种子淀粉精细结构受挤压操作参数影响显著。

径向微型分子泵结构设计及抽气性能仿真

微型分子泵用于航天器上微小型探测仪器的高真空环境获得。着眼于简化结构,减小体积与装配难度,面向径向微型分子泵,针对其核心部件——定转子进行结构设计,并利用ANSYS、COMSOL软件作仿真分析,探究定转子径向结构、叶片角度、节弦比等对泵抽气性能的影响;比较径向与轴向分子泵的抽气效果。结果表明,在同等抽气系统体积下,径向微型分子泵在获得高压缩比方面更具优势。