Synthesis, Characterization and X-Ray Structure of a Ba(II)/Ag(I)/Cr(III)-Oxalate Salt with Water-Filled Nanochannels

A novel mixed barium(II)/silver(I)/chromium(III) oxalate salt, Ba0.5Ag2[Cr(C2O4)3]·5H2O (1), with open architecture has been synthesized in water and characterized by elemental analysis, vibrational and electronic spectra, and single crystal X-ray structure determination. Compound 1 crystallizes in a monoclinic space group C2/c, with unit cell parameters a = 18.179(3), b = 14.743(2), c = 12.278(2)Å, β = 113.821(3), V = 3010.34(90) Å3, Z = 8. The structure is characterized by a network of anionic [Cr(C2O4)3]3- units connected through the O atoms of the oxalates to Ba2+ and Ag+ sites, forming a three-dimensional coordination polymer with one-dimensional isolated nanochannels parallel to the c axis, and encapsulating hydrogen-bonded guest water molecules. The bulk structure is consolidated by O–H···O bridgings within the nanochannels and by coulombic interactions.

Biomimetic MXene membranes with negatively thermo-responsive switchable 2D nanochannels for graded molecular sieving

Negatively thermo-responsive 2D membranes,which mimic the stomatal opening/closing of plants,have drawn substantial interest for tunable molecular separation processes.However,these membranes are still restricted significantly on account of low water permeability and poor dynamic tunability of 2D nanochannels under temperature stimulation.Here,we present a biomimetic negatively thermo-responsive MXene membrane by covalently grafting poly(N-isopropylacrylamide)(PNIPAm)onto MXene nanosheets.The uniformly grafted PNIPAm polymer chains can enlarge the interlayer spacings for increasing water permeability while also allowing more tunability of 2D nanochannels for enhancing the capability of gradually separating multiple molecules of different sizes.As expected,the constructed membrane exhibits ultrahigh water permeance of 95.6 L m^(-2) h^(-1) bar^(-1) at 25℃,which is eight-fold higher than the state-of-the-art negatively thermoresponsive 2D membranes.Moreover,the highly temperature-tunable 2D nanochannels enable the constructed membrane to perform excellent graded molecular sieving for dye-and antibiotic-based ternary mixtures.This strategy provides new perspectives in engineering smart 2D membrane and expands the scope of temperature-responsive membranes,showing promising applications in micro/nanofluidics and molecular separation.

On flow characteristics of liquid-solid mixed-phase nanofluid inside nanochannels

The atomic behavior of liquid-solid mixed-phase nanofluid flows inside nanochannels is investigated by a molecular dynamics simulation （MDS）. The results of visual observation and statistic analysis show that when the nanoparticles reach near each other, the strong interatomic force will make them attach together. This aggrega- tion continues until all nanoparticles make a continuous cluster. The effect of altering the external force magnitude causes changes in the agglomeration rate and system enthalpy. The density and velocity profiles are shown for two systems, i.e., argon （Ar）-copper （Cu） nanofluid and simple Ar fluid between two Cu walls. The results show that using nanopar- ticles changes the base fluid particles ordering along the nanochannel and increases the velocity. Moreover, using nanoparticles in simple fluids can increase the slip length and push the near-wall fluid particles into the main flow in the middle of the nanochannel.

Electrokinetic flow in the U-shaped micro-nanochannels

U-shaped micro-nanochannels can generate significant flow disturbance as well as locally amplified electric field, which gives itself potential to be microfluidic mixers, electrokinetic pumps,and even cell lysis process. Numerical simulation is utilized in this work to study the hidden characteristics of the U-shaped micro-nanochannel system, and the effects of key controlling parameters(the external voltage and pressure) on the device output metrics(current, maximum values of electric field, shear stress and flow velocity) were evaluated. A large portion of current flowing through the whole system goes through the nanochannels, rather than the middle part of the microchannel, with its value increasing linearly with the increase of voltage. Due to the local ion depletion near micro-nanofluidic junction, significantly enhanced electric field(as much as 15 fold at V=1 V and P_0=0) as well as strong shear stress(leading to electrokinetic flow) is generated.With increasing external pressure, both electric field and shear stress can be increased initially(due to shortening of depletion region length), but are suppressed eventually at higher pressure due to the destruction of ion depletion layer. Insights gained from this study could be useful for designing nonlinear electrokinetic pumps and other systems.

A Design Method of the Rotor Auxiliary Slot for the Water-filled Submersible Induction Motors

Aiming at the problem of electromagnetic vibration of the water-filled submersible induction motor(WSIM),a method of opening auxiliary slots on the rotor side is proposed to weaken the air-gap field harmonics caused by the rotor slot permeance harmonics.By analyzing the research status of electromagnetic vibration of the WSIM and the composition of the air-gap magnetic field of the motor,the idea that the auxiliary slots mainly affect the air-gap field harmonics by changing the air-gap permeance of the motor is put forward.The mathematical model of air-gap permeance of WSIM is established to simulate the influence of auxiliary slots on the air-gap permeance.Through the parametric analysis of the mathematical model,the change of auxiliary slot size is simulated.The air-gap permeance waveform is decomposed by the two-dimensional Fourier transform,and then the variation of the air-gap permeance harmonics with the size of the auxiliary slot is analyzed.Finally,the finite element simulation model of the WSIM with the auxiliary slots is established,and the waveform of the air-gap flux density of the motor is analyzed to verify the effectiveness of the mathematical model.Meanwhile,the results show that after opening the auxiliary slot,the radial electromagnetic force of the motor was reduced by 28.4%.

AN EXPERIMENTAL INVESTIGATION ON THE IMPACT PERFORATION FAILURE OF WATER-FILLED-PRESSURIZED PIPELINES

Some experimental data recorded from impact tests on empty and water-filled pressurized mild steel pipes are presented. The pipes were supported as a three-span continuous beam and impacted laterally by a rigid indenter at the mid-span of middle span. Three kinds of indenter nose shapes were used: blunt-nose, hemisphere-nose and 90?conical-nose. The internal pressure ranged up to 20 MPa. The perforation failure modes and corresponding critical impact energies were obtained under different test conditions. The time-history curves of the internal pressure and impact force were given. The experiments show that the media filled in the tube greatly decreased the ballistic limit energy.

不凝性气体对纳米通道内水分子流动传热影响的分子动力学模拟

随着电子元件高性能化和小型化的发展,纳米通道内工质的流动传热问题受到了更多的关注.本文采用分子动力学模拟方法,模拟了300,325,350 K的纳米通道中流体的流动传热情况,工质为水,水中不凝性气体用氩气代替.结果表明:流动过程中,氩原子形成高势能团簇,随着温度升高,流体势能上升,团簇逐渐减小或消失;少量气体原子能够促进流动,而较多氩气会导致通道中心区域形成较大气体团簇而阻碍流动,同时,被加热的工质能显著减小流动阻力系数;近壁面区域流体温度高于中心区域,团簇内部原子活动更加剧烈,平均分子动能更大,温度更高;水的氢键结构可以促进纳米通道内的传热,氩原子会影响氢键数量,高温会破坏水分子形成的氢键网络,使努塞尔数下降.本研究分析了不凝性气体影响下微通道内水分子流动传热的机理,为电子设备的强化传热提供了理论指导.

石英纳米孔中氦气与甲烷竞争扩散的分子模拟

氦气具有尺寸小、扩散和渗透能力强等特点,其独特的物理性质严重制约了氦气的聚集成藏。因此,深入揭示地质条件下氦气与甲烷的竞争扩散规律,是系统认识富氦天然气成藏机制的重要途径。首次采用分子模拟技术,构建了石英纳米狭缝-通道孔复合模型,探索了甲烷与氦气的混合气体在模型中的竞争扩散规律。分子模拟结果表明,甲烷对氦气的扩散有抑制作用,并且甲烷对吸附态氦气有较强的驱替能力;当氦气在混合气体中摩尔分数达90%时,游离态的氦分子可聚合形成直径更大的氦团簇,氦团簇的出现对氦气存储以及储氦库建设具有一定的启示。此外,当扩散通道孔的直径小于甲烷和氦气的动力学直径2倍时,甲烷和氦气无法从石英纳米通道扩散出去,此时分子间的排斥力很强,将阻止气体分子的进一步逸散,有利于氦气保存。研究结果提供了在原子分子水平下氦气与甲烷在石英纳米孔中的竞争逸散规律,为氦气的富集和保存机制研究提供了有用信息,并为氦气资源的勘探与开发提供了参考依据。

Outer-surface Covering of Nanochannels with Hydrogel for Highly Sensitive and Specific Cr(VI)Detection Through Analyte-caused Charge Change in Hydrogel

Nanochannels have made great progress and are a promising platform for detecting a series of targets.However,most nanochannels are modified on the inner wall,while ignoring the outer surface.Here,we modified the outer surface of nanochannels with hydrogel.Different from other reported outer-surface modification methods,we directly cover nanochannels with hydrogel to form heterogeneous membrane.The selected hydrogel hardly adsorbs other ions and shows specific adsorption for Cr(VI).The adsorption sites in hydrogel are homogeneous,and Cr(VI)adsorption onto hydrogel is endothermic and spontaneous.The charge in hydrogel changes after Cr(VI)adsorption,and the resulting current changes can be used for the detection of Cr(VI)with the detection limit of 10−11 mol/L.Our platform is expected to be used for Cr(VI)detection in living organisms,especially within cells.This work provides a new approach for outer-surface modification of nanochannels and offers a new choice for nanochannel detection platforms.

Impacts of multi-foulings on salinity gradient energy conversion process in negatively charged conical nanochannels

Membrane fouling inevitably occurs during nanofluidic reverse electrodialysis.Herein,the impact of multi-fouling on the energy conversion performance of negatively charged conical nanochannels under asymmetrical configurations is systematically investigated.The results reveal that in Configuration I,where a high-concentration solution is applied at the tip side,at small concentration ratios,multiple foulings reduce the electric power.In Configuration II,where a low-concentration solution is applied at the tip side,multiple foulings near the base side contribute to the electric power.Any fouling that formed near the lowconcentration entrance diminished the electric power and energy conversion efficiency.Multi-fouling lowered the electrical power consumption by 69.27%and 99.94%in Configurations I and II,respectively.In Configuration I,the electric power first increased with increasing fouling surface charge density,reached its maximum value,and thereafter decreased.In Configuration II,the electric power first decreased with increasing fouling surface charge density,reached its minimum value,and thereafter increased.Large negative or positive charge densities of fouling contribute to the electric power and energy conversion efficiency.

基于外表面修饰的固态纳米通道用于生物标志物分析的研究进展

生物标志物,如离子、小分子、蛋白质、多糖、核酸和细胞,参与生物体的构建,在生命过程中发挥重要作用。准确检测这些生物标志物对于疾病研究、早期诊断、药物评估和人类健康监测具有重要意义。外表面功能化固态纳米通道在纳米通道的外表面进行修饰,消除了对靶标分子的限制,通过基于离子信号的变化,提升了检测的速度和灵敏度。本文从外表面修饰的固态纳米通道在生物标志物检测方面进行综述,简要介绍了固态纳米通道外表面功能化的方法,重点总结了外表面修饰的固态纳米通道在生物标志物分析上的研究进展,简要展望外表面修饰的固态纳米通道所面临的挑战与发展机遇。

电场方向对一维断裂纳米通道连接处水桥结构的影响

电场影响纳米通道内的水分子的电偶极矩取向,进而影响纳米通道内的水分子的传输.为了有效发掘水分子在纳米通道内的传输特点,必须研究更复杂的纳米通道结构.最新一种构造复杂纳米通道的方式是构造断裂纳米通道.在研究断裂纳米通道内的水分子的动力学特点时,通常是在零电场或单一电场方向下进行的,电场方向对断裂纳米通道内的水分子的影响机理尚不明确,这制约了部分场控分子器件的设计.为了探究该问题,本文采用分子动力学模拟方法,系统研究了电场方向从0°变化到180°的过程中,电场方向对完整纳米通道以及断裂长度分别为0.2和0.4 nm的断裂纳米通道内的水分子的占据数、传输、水桥、电偶极矩偏向等性质的影响.结果表明,在1 V/nm的电场强度作用下,这三种纳米通道内的水分子的占据数、传输等差别主要集中在电场方向与管轴夹角为90°时,此时完整纳米通道内能形成稳定的水链,断裂长度为0.2 nm的纳米通道的连接处能形成不稳定的水桥,而断裂长度为0.4 nm的纳米通道的连接处不能形成水桥.此外,模拟发现当电场极化方向与管轴夹角为90°时,增大电场的强度,断裂纳米通道连接处的水桥更容易断裂.

棱形石墨烯纳米孔道内离子传输性能的分子动力学模拟

纳米通道的尺寸、结构和表面化学对其内部溶液的分布结构和输运性质有着重大影响.本文研究了一种全新的菱形石墨烯纳米通道.这种理想的通道与最近被广泛研究的金属有机框架材料(MOF)的内部结构类似,有着与传统的碳纳米管截然不同的内部结构.本文使用分子动力学模拟的方法研究在不同尺寸的菱形石墨烯纳米通道内的KCl溶液的性质,并将其与同尺寸的单壁碳纳米管进行了比较.研究结果表明在小孔道内(<20)其内部的溶液结构呈现若干个密度极高的聚集区域,即出现了结晶化的趋势.这一研究结果,将为MOF的结构设计提供思路,从而有望实现类似于生物离子通道的高选择性和高传输能力.

WORST SUBCARRIER AVOIDING WATER-FILLING SUBCARRIER ALLOCATION SCHEME FOR OFDM-BASED CRN

Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.

Electrokinetic pumping system based on nanochannel membrane for liquid delivery

Nonmechanical pumping of liquids is of key importance for applications from the biomedical microfluidic chip to drug delivery systems. In this paper, a new electrokinetic pump （EOP） system with polycarbonate nanoehannel membrane sandwiched between two membrane holders was constructed. The pump was tested with water and phosphate buffer at 1-6 V applied voltage, the maximum pressure and flow rate are 0.32 MPa （3.2 atm） and 4.2 μL/min for phosphate buffer, respectively. This proof-of-concept pump shows its potential use for drugs or chemical agents delivery by the usage of different membrane materials.

Anionic Nanochanneled Silver-Deficient Oxalatochromate(III) Complex with Hydroxonium as Counter Ion: Synthesis, Characterization and Crystal Structure

Reaction of Ba0.50[Ag2Cr(C2O4)3]·5H2O with Ag2SO4 in an aqueous solution of sulfuric acid (pH ≈ 3) yielded the silver(I)/chromium(III) oxalate salt H0.50[Ag2.50Cr(C2O4)3]·5H2O (1). Compound 1 can be best described as an anionic silver-deficient oxalatochromate(III) complex [Ag2.50Cr(C2O4)3]0.5- with nanochannels containing hydrogen-bonded water molecules and protons. Thermal analyses show significant weight losses corresponding to the elimination of water molecules of crystallization followed by the decomposition of the network.

Research on Water-Filling Patterns and Countermeasures──A case study of Xiaotun Coal Mine

There are many water-filling factors in Xiaotun Coal Mine, such as effective precipitation, goaf water, mining-induced fissure zone, surface water system, aquifers and tectonics. For different mining levels, the relative importance of these factors is different, and the water-filling condition is changed accordingly. So it is urgent to make it clear for mining. To ensure the safety of mining, we build a system of preventing mine water-filling using detailed AHP (analytical hierarchy process) calculation. This system is based on the analysis of mine water-filling factors in order to define the relative importance of the factors. Decision-makers use it as a strong scientific basis for Xiaotun Coal Mine.The method offered in this paper has been proved to be very applicable.

Temperature Fluctuations in a Rectangular Nanochannel

We consider an incompressible fluid in a rectangular nanochannel. We solve numerically the three dimensional Fourier heat equation to get the steady solution for the temperature. Then we set and solve the Langevin equation for the temperature. We have developed equations in order to determine relaxation time of the temperature fluctuations, τT = 4.62 × 10-10s. We have performed a spectral analysis of the thermal fluctuations, with the result that temporal correlations are in the one-digit ps range, and the thermal noise excites the thermal modes in the two-digit GHz range. Also we observe long-range spatial correlation up to more than half the size of the cell, 600 nm;the wave number, q, is in the 106 m-1 range. We have also determined two thermal relaxation lengths in the z direction: l1 = 1.18 nm and l2 = 9.86 nm.

Nanopores/Nanochannels Based on Electrical and Optical Dual Signal Response for Application in Biological Detection

Cancers and chronic diseases have always been global health problems. The occurrence and development of such diseases are closely related to the abnormalities of proteins, nucleic acids, ions or small molecules in the body. Nowadays, nanopores/nanochannels have emerged as a powerful platform for detecting these biomolecules based on the electrical signal variation caused by biomolecules passing. However, detection relied on the electrical signal easily suffered from the clogging defects, low throughput, and strong background signals. Fortunately, the emergence of designing nanopores/nanochannels based on electrical and optical dual signal response has brought innovative impetus to biological detection, which can also identify the chemical compositions and conformations of the biomolecules. In this review, we summarize the reasonable preparation of nanopores/nanochannels with electrical and optical dual signal response and their application in biological detection. According to different biomolecules, we divide the targets into four types, including nucleic acids, small molecules, ions and proteins. In each section, the design of representative examples and the principle of dual signal generation are introduced and discussed. Finally, the prospects and challenges of nanopores/nanochannels based on electrical and optical dual signal response are also discussed.

先进CO_(2)分离膜中纳米通道的构建及调控进展

从不同维度的CO_(2)传递纳米通道出发,综述了先进CO_(2)分离膜中纳米通道的构建与调控策略,讨论了纳米通道对CO_(2)分离性能的影响。最后,对CO_(2)分离膜中纳米通道的发展方向进行了总结与展望。