Nanochannel Formation Research Articles

Wafer Scale Gallium Nitride Integrated Electrode Toward Robust High Temperature Energy Storage.

Gallium Nitride (GaN), as the representative of wide bandgap semiconductors, has great prospects in accomplishing rapid charge delivery under high-temperature environments thanks to excellent structural stability and electron mobility. However, there is still a gap in wafer-scale GaN single-crystal integrated electrodes applied in the energy storage field. Herein, Si-doped GaN nanochannel with gallium oxynitride (GaON) layer on a centimeter scale (denoted by GaN NC) is reported. The Si atoms modulate electronic redistribution to improve conductivity and drive nanochannel formation. Apart from that, the distinctive nanochannel configuration with a GaON layer provides adequate active sites and extraordinary structural stability. The GaN-based supercapacitors are assembled and deliver outstanding charge storage capabilities at 140°C. Surprisingly, 90% retention is maintained after 50000 cycles. This study opens the pathway toward wafer-scale GaN single-crystal integrated electrodes with self-powered characteristics that are compatible with various (opto)-electronic devices.

Spike-time dependent plasticity of tailored ZnO nanorod-based resistive memory for synaptic learning

Metal oxide resistive memory is a potential device that can substantially influence the current roadmap for nonvolatile memory and neuromorphic computing. However, common amorphous oxide-based resistive random-access memory suffers from high forming voltages that complicate circuit design and abrupt SET behavior incompatible with analog weight updates. To overcome such limitations, wurtzite ZnO nanorods were synthesized on a fluorine-doped tin oxide (FTO) substrate and a bipolar resistive memory with the Ag/w-ZnO/FTO stacking sequence was fabricated. The hexagonal NR morphology of w-ZnO with controlled vertical growth and nanochannel formation between the NRs were produced by in situ crystalline growth. This morphology enabled a forming-free switching and an analog switching effect that emulated neuromorphic functionalities such as potentiation–depression and complex spike-time dependent plasticity-based Hebbian learning rules. Importantly, the device exhibited nonabrupt switching behavior suitable for analog weight updates in neuromorphic computing in contrast to conventional resistive memory.

Nanoscale confinement of energy deposition in glass by double ultrafast Bessel pulses

Abstract Ultrafast laser pulses spatially shaped as Bessel beams in dielectrics create high aspect ratio plasma channels whose relaxation can lead to the formation of nanochannels. We report a strong enhancement of the nanochannel drilling efficiency with illumination by double pulses separated by a delay between 10 and 500 ps. This enables the formation of nanochannels with diameters down to 100 nm. Experimental absorption measurements demonstrate that the increase of drilling efficiency is due to an increase of the confinement of the energy deposition. Nanochannel formation corresponds to a drastic change in absorption of the second pulse, demonstrating the occurrence of a phase change produced by the first pulse. This creates a highly absorbing, long-living state. Our measurements show that it is compatible with the semi-metallization of warm dense glass which takes place within a timescale of <10 ps after the first laser pulse illumination.

Covalent Triazine Frameworks Incorporating Charged Polypyrrole Channels for High-Performance Lithium-Sulfur Batteries

Covalent triazine frameworks (CTFs) have emerged as promising electrode materials for lithium-sulfur (Li-S) batteries owing to their pristine pyrdinic sites, conjugated backbone and ability to stabilize remarkable sulfur contents. Following the first synthesis of sulfur-CTFs under catalyst and solvent-free reaction conditions[1], new synthetic strategies have been extensively investigated to improve CTFs properties for Li-S batteries applications. Further upgrading for CTFs was introduced to achieve extremely high sulfur contents CTFs via employing nucleophilic aromatic substitution reaction (SNAr) between perfluoroaryl units and elemental sulfur.[2] However, the previous (SNAr) approach possessed immense sulfur conent up to 82%, it is challenging to endure high ionic and electronic conductivity with mitigation of Li-polysulfide (Li-PS) shuttling. These fatal problems limit their cycling performance at high active mass loadings. In an effort to tackle the previously mentioned problems, a new approach incorporates the integration of one-dimensional charged conducting polymers with a two-dimensional covalent triazine framework in the presence of elemental sulfur.[3] Noticeably, the addition of charged conducting polymers triggers a 3D nanochannel formation in the CTF framework with high-affinity anchoring sites towards Li-PS while achieving decent ionic and electronic conductivity. The resulting polymers showed significantly improved ionic , electronic conductivities and high sulfur loadings. Because of these remarkable properties, we are able to obtain exceptional electrochemical performance at high mass loading of 3 mg sulfur per cm2 with a specific capacity of 1275.2 mAh g−1 at 0.05C.

Functional Ionic Liquid Crystals.

Ionic liquid crystals have emerged as a new class of functional soft materials in the last two decades, and they exhibit synergistic characteristics of ionic liquids and liquid crystals such as macroscopic orientability, miscibility with various species, phase stability, nanostructural tunability, and polar nanochannel formation. Owing to these characteristics, the structures, properties, and functions of ionic liquid crystals have been a hot topic in materials chemistry, finding various applications including host frameworks for guest binding, separation membranes, ion-/proton-conducting membranes, reaction media, and optoelectronic materials. Although several excellent review articles of ionic liquid crystals have been published recently, they mainly focused on the fundamental aspects, structures, and specific properties of ionic liquid crystals, while these applications of ionic liquid crystals have not yet been discussed at one time. The aim of this feature article is to provide an overview of the applications of ionic liquid crystals in a comprehensive manner.

Hydrophilic Silver Nanoparticles Induce Selective Nanochannels in Thin Film Nanocomposite Polyamide Membranes.

Thin-film nanocomposite (TFN) membranes have been widely studied over the past decade for their desalination applications. For some cases, the incorporation of nonporous hydrophilic nanofillers has been reported to greatly enhance membrane separation performance, yet the underlying mechanism is poorly understood. The current study systematically investigates TFN membranes incorporated with silver nanoparticles (AgNPs). For the first time, we reveal the formation of nanochannels of approximately 2.5 nm in size around the AgNPs, which can be attributed to the hydrolysis of trimesoyl chloride monomers and thus the termination of interfacial polymerization by the water layer around each hydrophilic nanoparticle. These nanochannels nearly tripled the membrane water permeability for the optimal membrane. In addition, this membrane showed increased rejection against NaCl, boron, and a set of small-molecular organic compounds (e.g., propylparaben, norfloxacin, and ofloxacin), thanks to its combined effects of improved size exclusion, enhanced Donnan exclusion, and suppressed hydrophobic interaction. Our work provides fundamental insights into the formation and transport mechanisms involved in solid-filler incorporated TFN membranes. Future studies should take advantage of this spontaneous nanochannel formation in the design of TFN to overcome the classical membrane permeability-selectivity trade-off.

The effects of conductive nano fillers alignment on the dielectric properties of copolymer matrix

This research focuses on the improvement of the dielectric and energy harvesting properties of piezoelectric P(VDF-TrFE) copolymer matrix by the alignment of conductive reduced graphene oxide nano fillers. The dispersion and the morphology of the conductive nano fillers on the co-polymer matrix were characterized by scanning electron microscopy which showed a configurational phase transition due to highly conductive nano channel formation, steric hindrance, excluded volume interaction van-der-walls forces between adjacent reduced graphene oxide sheets. Five different piezoelectric nanocomposites were prepared by varying the reduced graphene oxide contents in P(VDF-TrFE) matrix to realize its optimum concentration in the matrix. From our analysis, we observed that, an optimized morphological structure plays a vital role in the formation of polar electroactive β phase on the co-polymer matrix through the good dispersion, filler alignment and interfacial interaction of reduced graphene oxide nano fillers. The as prepared nanocomposite film showed an enhanced crystallinity (50 ∼ 52%), dielectric constant (72 at 1 kHz), piezoelectric charge constant (−23 pC/N) with an output power of 3.2 µW at 1.8 MΩ load for 2 N mechanical force. All the outputs were observed without applying poling process. We expect that our synthesized self-poled nanocomposite can be a useful candidate for energy harvesting applications.

Full-field thickness measurement of ultrathin liquid film in receding contact-induced nano-channel using surface plasmon resonance.

This research demonstrates that a surface plasmon resonance (SPR) imaging technique can effectively measure full-field nanoscale thickness of a liquid water film filled in the receding contact-induced nano-channel. To the authors' knowledge this has not been demonstrated previously. Experimental calibration has been conducted by measuring surface plasmon resonance reflectance depending on the piezometer-controlled water nano-film thickness and comparing the experimental results with the theoretical calculations to show very good agreement. The measured full-field thickness profiles significantly visualize the three-dimensional nano-channel formation filled with liquid water film. It shows that the sensitivity and the resolution in thickness measurement are estimated as 1.21 pixel gray level/nm and 2.5 nm, respectively. The experimentally observed resolution is around 10 nm given the uncertainty in the demonstrated full-field mapping of thickness. From this research, it is demonstrated that SPR imaging successfully measures the thickness of ultrathin liquid film especially below 85 nm in full-field under normal conditions and can effectively characterize the three-dimensional nano-channel formation during the receding contact process.

Formation of Porous Anodic Alumina under Unstable Electroconvection Flow Regimes: A Case Study of Tartronic Acid Electrolyte

This work focuses on the systematic study of porous anodic alumina films grown in novel moderately concentrated tartronic (2-hydroxymalonic) acid electrolyte. The morphological analysis enabled us to reveal new details of the alumina pore formation mechanism and to discover the processes responsible for such frequently occurring defects as branched pores and multiple pore openings within a single cell. The qualitatively new model developed herein explains satellite nanochannel formation from a colloidal electroconvection standpoint—namely, by the temporary change of the existing nanoconvective flows, which give rise to the cooperative cell pattern in porous alumina, from laminar to turbulent mode (such flow regimes are generally termed “transitional” or in some recent literature also “laminar unstable”). Our theoretical discussion demonstrates that the morphological parameters of self-organized layers are strongly related to such properties of the liquid phase as the dielectric constant and the Debye leng...

Tunable Nanochannels along Graphene Oxide/Polymer Core–Shell Nanosheets to Enhance Proton Conductivity

Simultaneous manipulation of topological and chemical structures to induce ionic nanochannel formation within solid electrolytes is a crucial but challenging task for the rational design of high‐performance electrochemical devices including proton exchange membrane fuel cell. Herein, a novel generic approach is presented for the construction of tunable ion‐conducting nanochannels via direct assembly of graphene oxide (GO)/poly(phosphonic acid) core–shell nanosheets prepared by surface‐initiated precipitation polymerization. Using this simple and rapid approach to engineer GO/polymer nanosheets at the molecular‐level, ordered and continuous nanochannels with interconnected hydrogen‐bonded networks having a favorable water environment can be created. The resulting membranes exhibit proton conductivities up to 32 mS cm−1 at 51% relative humidity, surpassing state‐of‐the‐art Nafion membrane and all previously reported GO‐based materials.

Influence of magnetic nanoparticle arrangement in ferrogels for tunable biomolecule diffusion

We developed a novel method to control nanochannel formation in a magnetic nanohybrid membrane using an applied magnetic field. The direction of the nanochannels could be manipulated by magnetic nanoparticle self-assembly under different field directions.

Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers

The search for the next generation of highly ion-conducting polymer electrolyte membranes has been a subject of intense research because of their potential applications in energy storage and transformation devices, such as fuel cells, vanadium flow batteries, membrane-based artificial photosynthesis, water electrolysis, or water treatment processes such as electrodialysis desalination. Nanochannels that contain ionic groups, through which “hydrated” ions can pass, are believed to be of key importance for efficient ion transport in polymer electrolytes membranes. In this Perspective, we present an overview of the approaches to induce ion-conducting nanochannel formation by self-assembly, using polymer architecture such as block or comb-shaped copolymers. The transport properties of ion-containing aromatic copolymers are examined to obtain an insight into the fundamental behavior of these materials, which are targeted toward applications in fuel cells and other electrochemical devices. Challenges in obtaini...

Tuneable nanochannel formation for sample-in/answer-out devices

Control of the dielectric breakdown of PDMS was achieved by limiting the current during the breakdown process. This enabled tuning of the nanochannel pore size and hence their permeability for molecules of different molecular weights. This method enabled the analysis of the drug quinine from whole blood in 3 min using a simple, disposable microfluidic device.

Earliest Stage of the Tetrahedral Nanochannel Formation in Cubosome Particles from Unilamellar Nanovesicles

Studies of nonequilibrium lipid polymorphism at the nanoscale contribute to the in-depth understanding of the structural pathways for formation of aqueous channels and emerging of channels-network ordering in liquid-crystalline (LC) nanovehicles. We present experimental structural evidence for the smallest tetrahedral-type lipid membrane aggregate, which involves completely formed nanochannels and occurs as an early intermediate state during the bilayer vesicle-to-cubosome particle transition. Nanovehicles are generated from a self-assembled lipid mixture and studied by means of high-resolution cryogenic transmission electron microscopy (cryo-TEM) and synchrotron radiation small-angle X-ray scattering (SAXS). The investigated lipid membrane composition allows for the stabilization of long-lived intermediates throughout the unilamellar vesicle-to-cubosome nanoparticle (NP) transformation at ambient temperature. The observed small cubosomic particles, with well-defined water channels, appear to be precursors of larger cubic membrane structures, thus confirming the theoretical modeling of nanochannel-network growth in diamond-type cubic lipid particles. The reported structural findings, highlighting that bilayer vesicle membrane packing and fusion are required for nanochanneled cubosome particle formation, are anticipated to advance the engineering of small lipid NPs with controllable channels for biomolecular loading and release.

Solvent-assisted thermal annealing of disulfonated poly(arylene ether sulfone) random copolymers for low humidity polymer electrolyte membrane fuel cells

Fundamental studies of a new thermal annealing strategy for maximizing proton conductivity and single cell performance of glassy sulfonated hydrocarbon fuel cell membrane materials under both fully and partially hydrated conditions are reported. Directly copolymerized disulfonated poly(arylene ether sulfone) random copolymers (BisA-XX, XX is the mole percent of hydrophilic moieties, XX = 20 to 40) with 2,2′-isopropylidene diphenol swivel ((CH3)2–C) units in their polymer backbone were cast from N,N-dimethylacetamide (DMAc) and dried under two different protocols; one set was dried at 60 °C (BisA-XX_60 °C), and the other at 150 °C under vacuum immediately after the initial drying (BisA-XX_150 °C). Small amounts of DMAc solvent remained during the second drying step which depressed the glass transition temperatures (Tg) of the BisA copolymers lower than 150 °C. BisA-XX_150 °C samples were essentially thermally annealed when dried at 150 °C. This increased the density of BisA copolymer chains; their Tg values were increased. Moreover, T1 values of the protons in BisA-XX aromatic phenylene rings measured via solid-state NMR technique were lower as a result of the improved 1H–1H dipolar interaction. Interestingly, proton conductivity was improved after thermal annealing, possibly because the sulfonic acid density in the fully hydrated state (i.e., IECv(wet)) was enhanced. The synergistic effect of reduced water uptake and more developed hydrophilic–hydrophobic nanochannel formation may be important. The thermal annealing significantly influenced proton conductivity particularly at a low humidity (30 to 80% relative humidity (RH)). As a result, BisA-XX_150 °C samples derived from identical materials exhibited electrochemical polymer electrolyte membrane fuel cell (PEMFC) performances similar and superior to Nafion® 112 and BisA-XX_60 °C samples measured at 65% RH at 80 °C, respectively.

Self-organizing nanochannel networks in periodically perforated semiconductor films

In this paper we theoretically analyze the mechanism of nanochannel formation by an evolutionary etching process in periodically perforated semiconductor films. The compressive stresses due to lattice mismatch of the epitaxially grown nanoscale films are gradually relaxed; leading to an evolutionary buckling process. We quantitatively analyze the mechanics of wrinkle evolution around an isolated etch-pit, and a predictive tool to determine the edge-to-corner channel transition is developed. The buckling wavelength increases with increasing etch depth until the etch fronts of neighboring etch-pits merge and multiple channels coalesce. The effect of various system parameters such as etch-pit size, periodicity, and film thickness on the channel morphology has been studied and compared with experimental results. The good agreement provides insight into the physical mechanisms that govern the complex interplay during evolutionary etching and channel formation.

Nanochannel Formation of Hydrocarbon Membranes via Post- Fluorination

not Available.

Tuning nanopatterns on fused silica substrates: a theoretical and experimental approach

In this study we develop a novel approach to tune nanopatterns on fused silica substrates exploiting the polarization dependence of the strongly localized near field of highly ordered triangular nanoparticle arrays. For this purpose such arrays were prepared by nanosphere lithography on fused silica substrates and subsequently irradiated with single 35 fs long laser pulses. The irradiation leads to the excitation of localized surface plasmon polariton resonances, followed by ablation of the nanoparticles and partially of the substrate. By this means, nanostructures were generated on the substrate surface, reflecting the local fields in the vicinity of the triangular nanoparticles. Depending on the applied fluence, small holes as well as extended nanostructures with dimensions well below the diffraction limit have been created. Furthermore, by rotating the linear polarization of the laser light by 90° with respect to the orientation of triangular nanoparticles, different plasmon modes have been excited, which in turn, alter the local field distribution. As a result, either nanochannels or bone like shaped nanogrooves in a chequered structure were generated on the fused silica substrates. Finite-difference time-domain simulations demonstrate, that the results can, in fact, be explained by the enhanced near field distribution, which is dominated by the excitation of localized surface plasmon polariton resonances in the triangular nanoparticles. It is shown, that the fluence and the polarization of the laser light are the key parameters in nanogroove and nanochannel formation.

Nano-channel formation using a low-temperature glass-to-glass bonding process

A low-temperature glass-to-glass bonding process is demonstrated that creates uniform channels with a channel depth of 80 nm. The bond strength was characterized as a function of temperature and glass surface treatment. A significant increase in bond strength was found by rinsing the two glass surfaces with a calcium (II) acetate hydrate solution prior to bonding.

Electric Field Effect on Nanochannel Formation in Electrochemical Porous Structures of Alumina

The authors investigated the anodization mechanism of aluminum in an oxalic acid solution, and the electrochemical reaction is very unique for pore formation via the dissolution process, which is very dependent on the surface geometry in nanoporous alumina templates. The cross-sectional nanochannels showed that the geometrical curvature of the initial surface can cause the branching of nanochannels to be adjusted in volume occupancy to be direct to the electric field normal to the surface. The nanoporous alumina with the crystalline γ-Al2O3 phase showed hexagonal ordering at a voltage of 40 V, with a nanohole distance of 102 nm from the charge density oscillation of the oxalic acid solution.