Nano Channels Research Articles

Thermal Resistance for Au–Water and Ag–Water Interfaces: Molecular Dynamics Simulations

Thermal Resistance for gold (Au)–water and silver (Ag)–water interfaces are calculated using a reversed non-equilibrium molecular dynamics simulation. Temperature and heat flow dependence of Interfacial thermal resistance (ITR) based on a solid–liquid–solid nano channel system are explained. The results are compared with existing literature to investigate the effect of different force fields for both metal atoms and water molecules, and also to demonstrate the application of the molecular dynamics (MD) simulation to different systems.

Formulation and Evaluation of Ketoconazole Nanosponge gel

Ketoconazole Nanosponges were prepared by using Hyper cross linked β-cyclodextrin method by using different concentration of cross-linker. Diphenyl carbonate was used as the cross linking polymer. Nanosponge formulations were prepared by using β-CD: cross linker ratios of 1:15, 1:10, 1:5 and 1:3.Thepreparednanosponges were evaluated for percentage yield, incorporation efficiency, particle size, drug polymer compatibility, scanning electron microscopy andin-vitrodrugrelease.SEM studies confirmed their porous structure with number of nano channels. The FTIR spectra showed stable character of Ketoconazole in mixture of polymers and revealed the absence of drug polymer interactions. DSC study revealed that drug was involved in complexation with nanosponges. The average particle size of Ketoconazole nanoparticles was found to be in the range of 78.81± 0.20 nm to336.02 ± 0.124nm.The drug release from nanosponges was found to extended upto 8hr. 82 to 92%.The nano sponges were formulated into gel using Carbopol 940Batches G1 to G4 were prepared by incorporating nanosponges equivalent to 6%w/w of ketoconazole in different polymer concentrations respectively and evaluated for Percent drug content, Viscosity study, Spreadability study, In vitro diffusion studies. Nanosponge gel G1 showed the optimum pH, viscosity, Spread ability and In vitro release. Drug diffusion from the nanosponge loaded gel formulations was show sustained rate. A sustained release topical drug delivery of Ketoconazole developed as a nanosponge loaded gel offers solubilizing matrix for the drug, served as a local depot for sustained drug release and provided a rate limiting matrix barrier for modulation of drug release.

Single Molecule Experiments Define the Role of Nbs1 and Xrs2 in DNA Tethering by MRN and MRX in DSB Repair

To ensure genome stability and hinder introduction of disease-causing changes, DNA double-strand breaks (DSB) need to be repaired. Homologous recombination (HR) is a key DSB repair pathway. At the start of HR, the MRE11-RAD50-NBS1 (MRN) complex finds the broken ends and upon stimulation of its nuclease activity by CtIP performs the DSB processing for repair. The repair process involves DNA tethering, which is poorly understood. in this study, we use single-molecule analysis to investigate how MRN interacts with long DNA. The method is based on confining long DNA molecules in nanochannels. in contrast to tethering one or both ends to a substrate, as in most common single DNA molecule methods, the DNA is completely free in the nano channels, meaning that reaction on the DNA ends can be studied. Single molecule experiments with MRN and DNA in nanochannels show direct evidence of a strong DNA interaction and tethering of distant DNA fragments by MRN. When comparing MRN and the yeast homologue Mre11-Rad50-Xrs2 (MRX), we observed key similarities. in both systems, the absence of NBS1/Xrs2, lowers the concatemer and circle formation dramatically. Data from single molecule experiments and EMSA show that NBS1 and Xrs2 alone have a strong DNA interaction. These findings strengthen the theory of Nbs1/Xrs2 playing a role in the localization of the MRN/X complex to DNA ends and mediate DNA annealing. Finally, the addition of the MRN/X co-factor CtIP and Sae2, respectively, shows little to no effect on the bridging by MRN/X, although both CtIP and Sae2 exhibit strong DNA bridging on their own. Thus the interaction between MRN/X and the co-factor that is crucial for the nuclease activity is potentially not important for DNA bridging.

Effects of Total Dose Radiation on Single Event Effect of the Uniaxial Strained Si Nano NMOSFET

The effect of total dose radiation on the single event effect of uniaxial strained Si Nano channel metal oxide semiconductor field effect transistor (NMOSFET) was studied by TCAD simulation. By comparing the experimental results, the TCAD simulation model of the 50 nm strained Si NMOS device is established. The model is used to simulate the off-state single event effect (V ds = 0.05) of NMOSFET under the total dose radiation. The results show that total dose radiation increases the body potential of NMOSFET devices and intensifies the single event transient process of NMOSFET devices. The transient current increases by 4.88% and the drain charge increases by 29.15% under the total dose of 2KGy, which indicates that the effect of total dose radiation on the single event effect is the main factor affecting the collection of drain charge. Therefore, the experimental results and the established model provide good reference for the study of irradiation reliability of the uniaxial strained Si Nano NMOSFET and the application of strained integrated circuits.

Process simulation of nano-channel forming by thin film deposition

In the traditional fabrication process of micro/nano-fluidic chips, thermal bonding is usually used for channel sealing, but it is easy to cause channel blockage, especially when the channel size is nanometer. The film deposition is a better way to seal the nano channel, and by controlling the deposition angle, the shape and size of the sealed channel can also be controlled. In order to understand the channel formation process of thin film deposition more intuitively, based on the COMSOL software, a free molecular flow module is used to simulate the film deposition process. The growth of the film is characterized by the post-processing of geometric deformation, so as to predict the channel shape. By comparing the simulation results with the experimental results, it can be seen that this simulation can explain the process of forming channels by angle-deposited films to a certain extent, and predict the channel size. In addition, the simulation results, in turn, can guide the film deposition process, so as to control the size of nano channel.

Spatial conformation measurement of gold nanorods translocated through a solid-state nanopore

The solid-state nanopore has been developed as a powerful biosensor to detect individual molecules and nanoparticles. The operational principle of the technique was to determine the volume, concentration, and zeta potential of the particles from the electrical signals as nanoparticles passing through the pore. Here, gold nanorod samples were used to measure the dynamic translocation process though a nano channel. Gold nanorods have a high throughput in silicon nitride nanopore sensing because of their positive charge characteristics. Meanwhile, a set of varied shapes of nanorods was modeled in nanopore transport. Rod-like nanoparticles were found to adjust partial conformation to enter and pass the pore, and it was found that the dynamic process of nanorod translocation is the result of a combination of electrophoresis and electroosmotic action between nanopores and nanoparticles. These results improve our understanding of the dynamics of rod-shaped biopolymers and viruses translocating through biomembranes. They provide a new way of depicting biomolecule transport in the life system.

Computer Simulation Based Optimization of Aspect Ratio for Micro and Nanochannels

For Computational Fluidic Dynamics (CFD) analysis, different types of software are available such as ANSYS, COMSOL, GAMBIT and ABAQUS. ANSYS FLUENT is a very influential CFD software that enables the researchers to execute advanced and fast simulation as the performance of product is optimized. In this research work, the capabilities of ANSYS FLUENT have been investigated through the fluidic simulation of nano scale channels. Here, the simulation of three straight shaped and one curvilinear nano channel has been performed to analyze the precision of simulation with the aspect ratio of smaller dimensions (radius, length). The accurate dimensions have been determined for various shapes of channels. For straight circular channel, the radius of 124.9 µm and length of 900 µm are the dimensions found for error free simulations with 7.20 aspect ratio. While for straight crossed channel, the radius of 5.1 mm and length of 100 mm are the accurate dimensions for error free simulations with 19.60 aspect ratio. Width and depth are determined as 180 µm with 180 µm length in case of straight square channel for error free simulations with 1.0 aspect ratio. Finally, in case of curvilinear channel for error free simulations, the radius and length are found 22 and 209.1 µm respectively with 9.50 aspect ratio. None of the channels is found fit for simulation in nanometer range. Even in micrometer range, the simulations of these channels have acquired errors. Moreover, it has been observed that the aspect ratio is different for different geometries of microchannels for error free simulation.

Nanotechnology for bioactives delivery systems

The properties of functional foods depend largely on their micro- and/or nano-scale structure. Conventionally, the preparation of functional foods is based on large-scale processing. As a consequence, the structure of the products cannot be precisely controlled. Recently, micro-/nano-technology have been developing and increasingly applied to the formulation of functional foods. This paper summarizes some applications of micro-/nano-processing of food materials into dispersions, foreseeing their application as bioactives delivery systems. Nanodispersions containing antioxidant food materials were formulated and evaluated using various top-down techniques or a bottom-up method, particularly the performance of various polyglycerol esters (PGE) of fatty acid in the preparation and characterization of β-carotene nanodispersions during in vitro gastric digestion. MicroChannel (MC) and nanochannel (NC) emulsification for producing monodisperse emulsions were investigated. The development of NC emulsification devices for monodisperse fine emulsions is also presented.

Ultra-small interlayer spacing and nano channels in anionic layered perovskite Cs2Pb(SCN)2I2 enable efficient photoelectric conversion

Due to distinctive lattice and electronic properties, the thiocyanate anion (SCN−) perovskite as an alluring two-dimensional (2D) material system, can be applied in optoelectronic devices. Herein, both photovoltaic and photodetection performances of the 2D Cs2Pb(SCN)2I2 have been investigated. Compared with the conventional cationic 2D perovskites, Cs2Pb(SCN)2I2 possesses ultra-small interlayer spacing, additional interlayer nano channels, which is thus beneficial for charge transport ability. The planar heterojunction solar cell based on Cs2Pb(SCN)2I2 as the light absorber, has presented the highest power conversion efficiency among long-chain-cation-based 2D perovskite devices. Besides, the Cs2Pb(SCN)2I2-based photodetector also exhibits much higher photodetection performance (i.e. quantum efficiency, on/off ratio, responsivity, detectivity, response speed, polarization sensitivity and detection stability). It is thus suggested that these outstanding photoelectric characteristics of Cs2Pb(SCN)2I2 could bring huge opportunities for its more abundant optoelectronic applications, such as field-effect transistor and light-emitting diodes.

Modelling of fin width dependent threshold voltage in fin shaped nano channel AlGaN/GaN HEMT

Abstract A systematic theoretical model of threshold voltage (VT) for AlGaN/GaN fin shaped nano channel HEMT (FinHEMT) structure has been proposed. This device can achieve enhancement mode operation with decreased fin width (Wfin). This proposed model captures the decreased two dimensional electron gas (2DEG) density due to combined effect of built-in partial strain relaxation and partial side wall depletion (Wdepl) of nano channel due to surface potential of sidewalls. This leads to positive VT which varies inversely with Wfin. This influence indicates that narrower fin width below 60 nm contributes to a stable positive threshold voltage.

Ag as Cocatalyst and Electron-Hole Medium in CeO2 QDs/Ag/Ag2Se Z-scheme Heterojunction Enhanced the Photo-Electrocatalytic Properties of the Photoelectrode.

A recyclable photoelectrode with high degradation capability for organic pollutants is crucial for environmental protection and, in this work, a novel CeO2 quantum dot (QDs)/Ag2Se Z-scheme photoelectrode boasting increased visible light absorption and fast separation and transfer of photo-induced carriers is prepared and demonstrated. A higher voltage increases the photocurrent and 95.8% of tetracycline (TC) is degraded by 10% CeO2 QDs/Ag2Se in 75 minutes. The degradation rate is superior to that achieved by photocatalysis (92.3% of TC in 90 min) or electrocatalysis (27.7% of TC in 90 min). Oxygen vacancies on the CeO2 QDs advance the separation and transfer of photogenerated carriers at the interfacial region. Free radical capture tests demonstrate that •O2−, •OH, and h+ are the principal active substances and, by also considering the bandgaps of CeO2 QDs and Ag2Se, the photocatalytic mechanism of CeO2 QDs/Ag2Se abides by the Z-scheme rather than the traditional heterojunction scheme. A small amount of metallic Ag formed in the photocatalysis process can form a high-speed charge transfer nano channel, which can greatly inhibit the photogenerated carrier recombination, improve the photocatalytic performance, and help form a steady Z-scheme photocatalysis system. This study would lay a foundation for the design of a Z-scheme solar photocatalytic system.

Reaction mechanism during hydrothermal alteration of K-feldspar under alkaline conditions and nanostructures of the producted tobermorite

钾长石在碱性流体蚀变过程中会形成层状铝硅酸盐等矿物，前人对其反应机制和反应产物进行了研究，但缺乏微观尺度尤其是纳米尺度的探讨。因此，作者对钾长石在极端碱性条件下（190℃，24h，初始pH=12.4）的蚀变机制及其蚀变产物层状硅酸盐托贝莫来石的显微结构开展了纳米尺度的研究。X射线粉末衍射、扫描电子显微镜、能量色散光谱等观测结果显示，钾长石在碱性条件下水热蚀变所得到的产物主要为托贝莫来石、水钙铝榴石和方解石。高分辨率的透射电镜结果表明，在钾长石与次生矿物相的界面形成了纳米级的多孔非晶质层，且在空间上表现出结构的不连续性。界面溶解-再沉淀（CIDR）机制很好地解释了钾长石与次生矿物相界面的空间不连续性和非晶质层的形成。对蚀变产物中纤维状的托贝莫来石晶体进行显微结构表征，结果表明托贝莫来石的孔隙直径为0~160nm，平均孔径约为40nm；其构成的纳米孔隙和通道有利于增加周围流体中离子和气体的溶解度，并可能会影响局部化学平衡。这为层状铝硅酸盐作为自然界以及工业吸附材料和催化剂的更广泛应用提供了重要依据。;K-feldspar alteration in alkaline fluid generally generates layered aluminosilicate and other minerals. Previous studies mainly focused on the reaction mechanism and alteration products, however, little is known on the mechanisms of alteration and the secondary products at nano-scale. We studied the alternation mechanism of K-feldspar under extreme alkaline conditions (190℃, 24h, initial pH=12.4) and the microstructure of tobermorite as one of the alternation products. Characterizations of X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopy reveal that the secondary phases resulting from alternation of K-feldspar are mainly a mixture of tobermorite, hydrogrossular and calcite. Novel nanometer-scale measurements by high resolution analytical transmission electron microscope reveal the formation of an alteration rim of porous amorphous material nanometer thick at the interface of the K-feldspar and secondary phase, and the interface shows spatial and structural discontinuity. Coupled interfacial dissolution reprecipitation (CIDR) explains the sharp interface and the formation of the amorphous layer. The nanostructure measurements of the fibrous tobermorite crystals in the alteration products show that the pore diameter of tobermorite has a range of 0~160nm, and the average pore diameter is about 40nm. The nano pores and nano channels in tobermorite may promote the solubility of ions and gases and affect the chemical balance of the surrounding fluid. This provides an important basis for the application of layered aluminosilicate as natural and industrial adsorption materials and catalysts.

Method of Approximate Particular Solutions of Electro-Kinetic Fluids in Micro and Nano channels

Method of Approximate Particular Solutions of Electro-Kinetic Fluids in Micro and Nano channels

Glycerol molecules in nano channels of NaY and USY zeolites

Rich nano channels of zeolites give themselves excellent adsorption capacity, which have been widely used in environmental protection and catalysis. The adsorption process and existential form of the molecules in the nano channels are affected by the spatial confinement and regularity of the nanoporous channels. In this work, the adsorption of glycerol molecules in NaY and USY zeolites nano channels were studied. The results showed that adsorption quantity of glycerol molecules in nano channels and formation of glycerol molecular clusters were significantly affected by the static adsorption time. Due to the spatial confinement of the nanoporous channel, the H⋯O bond length and the HO⋯O angle were reduced. TEM scanning results indicated that the size of glycerol molecular cluster in nano channel was smaller than that of the bulk ones outside nano channel. 1H NMR results suggested that the spin motion of the hydroxyl hydrogen bond was enhanced. Computer simulation results showed that intermolecular hydrogen bonds were formed between the glycerol molecular cluster and oxygen atoms on the channel wall. This work may show new light on the study of molecular immobilization in spatial confinement.

Enhanced teeth whitening by nanofluidic transport of hydrogen peroxide into enamel with electrokinetic flows

Tooth whitening, a routine procedure in dentistry, is one of the examples of medical procedures that are limited by the challenge of delivering molecules into various types of nanoporous tissues. Current bleaching methods rely on simple diffusion of peroxides into enamel nano channels, therefore requires sufficient contact time with peroxides. In-office treatments often involve enamel etching or light activation which often results in patient sensitivity and potential soft tissue damage. ObjectiveTo demonstrate a robust method to transport hydrogen peroxide to greater depths into enamel nanopores through nanofluidic flows driven by electrokinetics, with the intention to increase efficacy while reducing treatment time. MethodsFreshly extracted human teeth were subjected to electrokinetic flow treatment with hydrogen peroxide under different electric fields with varying operation times. Pre- and post-operative shade matching was done using a photospectrometer. ResultsIt is demonstrated that the operation time for the same concentration of hydrogen peroxide can be shortened by 10 times. The proposed method showed significant improvements in whitening effects over control groups and thus offers promising clinically-viable chairside applications with efficacy. SignificanceThe demonstrated nanofluidic transport of hydrogen peroxide into enamel has a potential to be applied for enhancing tooth whitening, compared to simple diffusion, without heating the hard dental tissues.

Inertia of liquid microthermometer readings

Currently the need for micro thermometers with low inertia and accordingly with the small diameter of the capillary is increasing, and information about their inertia, which is necessary, in particular, for medicine, becomes insufficient. Micro thermometers with liquid-phase sensitive elements are made on the basis of capillaries filled with liquid. Important is the type of liquid (water, alcohol, mercury, etc.), the angle of inclination of the thermometer capillary, and its internal diameter. The time of their thermal inertia is rather small, since the thermal equilibrium of the thermometer and the controlled object is set extremely fast. However, in reality, the movement of a liquid in a capillary of a thermometer, which determines the readout of the temperature value, due to the change in the thermodynamic conditions during the measurement, is not so rapid to satisfy the metrology. The experience of studying the spontaneous penetration of liquids in porous micro and nano channels of natural structures is limited mainly by works that capture the significance of the influence of initial conditions. The features of filling capillaries of different internal diameters at different angles of inclination are considered in the paper. It enables us to work out the technology of manufacturing and application of these thermometers, and thus to predict the duration of setting the micro thermometers’ indications not limited by thermal inertia. For this purpose, the Washburn’s and Bosanquet equations are considered. Rate of filling the capillary is affected by fluid viscosity, surface tension, length of the filled capillary, and its diameter. Since the viscosity of the liquid increases slightly with pressure and decreases exponentially with temperature, it is inversely proportional to the rate of liquid penetration or to the rate of moving meniscus. We have analyzed the impact of these factors on the micro thermometers’ performance that promotes their efficient production and application.

Constructing micro-nano Na3V2(PO4)3/C architecture for practical high-loading electrode fabrication as superior-rate and ultralong-life sodium ion battery cathode

NASICON-structure Na3V2(PO4)3 (NVP) is a potential cathode for sodium ion battery, which however needs nano-crystallization to improve its rate performance. On the other hand, most practical electrodes are fabricated through slurry printing process, which needs to control the particle size to avoid the falling of the composite. Herein, for practical high-loading electrode fabrication, the micro-nano architecture, i.e. the micro particle plus nano channels inside, is suggested in this paper. The micro-nano information about NVP is obtained through Ga+ focused ion beam-scanning electron microscopy to reconstruct the 3D model of a single NVP particle, fully exhibiting the continuous nano channels inside the micro sphere. The as-obtained NVP/C sample in the micro size exhibits remarkable enhanced rate performance of 106, 104, 101, 96, 89, 70 and 44 mAh g−1 at rates of 2, 5, 10, 20, 50, 100 and 200 C respectively, compared to the control sample in the nano size with the capacity of 106, 103, 85, 77 and 60 mAh g−1 at 2, 5, 10, 20 and 50 C respectively, meanwhile maintaining good adhesion towards Al foil and electrochemical performance at the areal loading of 10 mg cm−2.

Ferroelectric Extended Nanofluidic Channels for Room‐Temperature Microfuel Cells

AbstractIntegration of fuel cells into microfluidic devices requires development of innovative proton conductors. Conventional Nafion membranes are incompatible with planar‐type microfluidic devices and require a high operation temperature of over 100 °C to achieve rapid proton transfer. In contrast, glass nanochannels (NCs) work as proton conductors even at room temperature and can be seamlessly integrated into microfluidic devices, which in turn makes microfuel cells (µFCs) attractive for a wide range of practical applications, such as power sources for ultrasmall autonomous electronics and chemo‐ or biosensors. However, the conductivity of NCs is limited by their small cross‐sectional area. It is revealed that spontaneous polarization of lithium niobite (LiNbO3) used as the NC material enhances a surface charge of a SiO2 layer formed on LiNbO3 and induces a fast proton transfer in water in the NCs. It is demonstrated that a µFC containing the LiNbO3 NCs demonstrates a proton diffusion coefficient that is 1.8 times higher than that of a reference device with bare glass NCs. In addition, such a µFC achieves a remarkable power output of up to ≈54 mW cm−2 at room temperature, which is 1.4 times higher than that of the similar device with bare glass NCs.

Organic Dye Solution Nanofiltration by 2D Zn-TCPP(Fe) Membrane – leverage of chemical and fluid dynamic effects

This study investigates organic solvent nanofiltration (OSN) using the membranes composed of 2D Zn-TCPP(Fe) nanosheets. A group of organic dyes with different molecular weights, hydrophilic properties and functional groups was selected as probe solutes in ethanol, isopropanol and ethyl acetate, respectively, to examine their OSN characteristics through the Zn-TCPP(Fe) membrane. The intermolecular interactions of organic solvent, dye and Zn-TCPP(Fe) nanosheets profoundly influence the mass transfer in the nano channels of the lamellar membrane. Representatively, the isopropanol solution of Brilliant Blue G dye turns out to have a favorable OSN performance (>90 % rejection with an average permenance of 175 L∙m-2∙h-1∙bar-1) over 4h, whereas replacement of isopropanol by ethanol results in incipient loss of rejection. However, for this ethanol solution feed, incorporating an optimal dose of ZIF-8nanograins into the nanosheets via co-deposition, a particle-over-lamellae structure formed unveils a significant improvement on OSN. Such boost is attributed to a combinative effect, i.e., alleviating dye-nanosheet complexation so as to reduce disturbing the lamellar structure as well as to assist desolvation of the dye over the feed side. To comprehend how solvent-slolute-nanosheet interactions dominate OSN, besides the experimental characterizations, both visco-molar volume and Stokes-Einstein diameter that describe fluid dynamic properties of solute molecule in a solvent are employed to assist the analysis. Possessing hydrophilic characteristic, Zn-TCPP(Fe) nanosheet engages strong hydrophilic association with hydrophilic dye and solvent, leading to weak OSN performance. Fundamentally, there are mutual interactions among solvent, solute and nanosheets in this membrane system, in which the prevailed pair of them impacts OSN performance.

Catalytic cyclohexene oxidation in the nano channels of a copper silicate material

Herein we examined the catalytic activity of the copper silicate material SGU-29 for the aerobic partial oxidation of cyclohexene under mild conditions (1 bar of O2 at 70 °C). In particular, the catalytic properties of the active sites provided by [CuO4] square planar units in SGU-29 were investigated for cyclohexene oxidation to generate three main oxidation products (i.e., 2-cyclohexene-1-ol, 2-cyclohexene-1-one, and cyclohexene hydroperoxide). Based on the molecular sieving effect of SGU-29, we especially investigated the intrazeolitic reaction, a catalytic cyclohexene oxidation occurring only in nanochannels of SGU-29. A conversion yield of 42% was obtained for the aerobic cyclohexene oxidation occurring only in SGU-29 nanochannels under 1 bar of O2 at 70 °C for 12 h. We demonstrated unequivocally that catalysis occurred only within the inner channels of SGU-29, rather than on its external surface or within the solvent, and we highlighted the special role of [CuO4] square planar units in catalysis.