Lumen Of Nanotubes Research Articles

Encapsulation of Uranium Oxide in Multiwall WS2 Nanotubes.

Uranium is a high-value energy element, yet also poses an appreciable environmental burden. The demand for a straightforward, low energy, and environmentally friendly method for encapsulating uranium species can be beneficial for long-term storage of spent uranium fuel and a host of other applications. Leveraging on the low melting point (60°C) of uranyl nitrate hexahydrate and nanocapillary effect, a uranium compound is entrapped in the hollow core of WS2 nanotubes. Followingly, the product is reduced at elevated temperatures in a hydrogen atmosphere. Nanocrystalline UO2 nanoparticles anchor within the WS2 nanotube lumen are obtained through this procedure. Such methodology can find utilization in the processing of spent nuclear fuel or other highly active radionuclides as well as a fuel for deep space missions. Moreover, the low melting temperatures of different heavy metal-nitrate hydrates, pave the way for their encapsulation within the hollow core of the WS2 nanotubes, as demonstrated herein.

A ferroptosis-targeting ceria anchored halloysite as orally drug delivery system for radiation colitis therapy

Radiation colitis is the leading cause of diarrhea and hematochezia in pelvic radiotherapy patients. This work advances the pathogenesis of radiation colitis from the perspective of ferroptosis. An oral Pickering emulsion is stabilized with halloysite clay nanotubes to alleviate radiation colitis by inhibiting ferroptosis. Ceria nanozyme grown in situ on nanotubes can scavenge reactive oxygen species, and deferiprone was loaded into the lumen of nanotubes to relieve iron stress. These two strategies effectively inhibit lipid peroxidation and rescue ferroptosis in the intestinal microenvironment. The clay nanotubes play a critical role as either a medicine to alleviate colitis, a nanocarrier that targets the inflamed colon by electrostatic adsorption, or an interfacial stabilizer for emulsions. This ferroptosis-based strategy was effective in vitro and in vivo, providing a prospective candidate for radiotherapy protection via rational regulation of specific oxidative stress.

Manipulation of the halloysite clay nanotube lumen for environmental remediation: a review

The halloysite clay nanotube lumen has shown great application potential in the field of environmental remediation. This relies on delicate manipulation of the clay nanotube lumen and benefits from the unique functionality of the nanotube lumen.

Structural, textural and thermal characterization of a confined nanoreactor with phosphorylated catalytic sites grafted onto a halloysite nanotube lumen

Mesoporous materials are very attractive solids for the fabrication of confined nanoreactors since they overcome the problems of diffusion/deactivation shown by microporous structures. In this work, we present the fabrication of a confined nanoreactor obtained by functionalization with phosphoric acid of the empty lumen (diameter 10–15 nm) of halloysite nanotubes (Hal).Two different halloysite nanoreactors with phosphorylated catalytic sites were prepared by the wet impregnation method followed by thermal activation: 1) phosphate modified Hal (starting with pristine Hal), and 2) phosphate-modified etched Hal (starting with etched Hal obtained by soft-etching pristine Hal using sulphuric acid). The selective grafting of hydrogen phosphate groups onto the aluminol active sites was characterized by solid-state nuclear magnetic resonance (1H, 27Al, 29Si HPDEC and 31P) and Fourier transform-infrared spectroscopies, and thermogravimetric and nitrogen physisorption analyses.Two different aluminum phosphate (AlOP) binding modes, monodentate (AlOPO(OH)2) and bidentate (AlO)2P(OH)2, with different distributions were observed in both phosphorylated-Hal nanoreactors. The selective functionalization of the internal lumen was confirmed because no interaction (due to SiOP binding mode) was detected between the outer surface of Hal and phosphoric acid.The confined nanoreactors prepared here preserved the main chemical structure and textural properties of Hal. The analysis of the specific surface area and mesopore size showed that, depending on the starting material, grafting the phosphate groups led to the formation of a monolayer or a polycondensation of phosphate moieties inside the tubular mesopore. However, in both prepared nanoreactors, phosphorylation did not result in saturating the material or pore blocking.These mesoporous materials could be used in catalysis and in situ nanoparticle synthesis.

Confining sulfur particles in clay nanotubes with improved cathode performance of lithium–sulfur batteries

Lithium–Sulfur batteries have high energy storage capacity while their sulfur cathode suffers large volume change, polysulfides dissolution and shuttle effect, and capacity fading during long-term cycling. To help lock sulfur and mitigate these problems, we introduce halloysites, a natural clay material with nanotube format, to disperse and confine sulfur nanoparticles as well as to suppress the dissolution and migration of polysulfides. Halloysites are firstly made conductive by covering with a glucose-derived carbon skin. Sulfur nanoparticles are then trapped in both lumen and outside surface of individual nanotubes with a loading dosage up to 80 wt%. In this new halloysite/sulfur composites cathode, the hollow nanostructure of halloysites provides space to allow dimension changes of encapsulated sulfur nanoparticles during repeated lithiation while limit their size up to the diameter of nanotube lumen (i.e., 25 nm or less). The stacked halloysite clusters further create many nanoscale voids to divide the sulfur-electrolyte interface into isolated domains and increase the migration tortuosity in electrolytes to suppress the dissolution and shuttle effect of polysulfides. These features together contribute to improved cycling stability, retaining nearly ~84% of the starting capacity over 250 cycles, though the diffusion of lithium ions into and out of nanotubes show some differences.

Electrophysiological Methods for Detection of Membrane Leakage and Hemifission by Dynamin 1.

Membrane fusion and fission are indispensable parts of intracellular membrane recycling and transport. Electrophysiological techniques have been instrumental in discovering and studying fusion and fission pores, the key intermediates shared by both processes. In cells, electrical admittance measurements are used to assess in real time the dynamics of the pore conductance, reflecting the nanoscale transformations of the pore, simultaneously with membrane leakage. Here, we described how this technique is adapted to in vitro mechanistic analyses of membrane fission by dynamin 1 (Dyn1), the protein orchestrating membrane fission in endocytosis. We reconstitute the fission reaction using purified Dyn1 and biomimetic lipid membrane nanotubes of defined geometry. We provide a comprehensive protocol describing simultaneous measurements of the ionic conductance through the nanotube lumen and across the nanotube wall, enabling spatiotemporal correlation between the nanotube constriction by Dyn1, leading to fission and membrane leakage. We present examples of "leaky" and "tight" fission reactions, specify the resolution limits of our method, and discuss how our results support the hemi-fission conjecture.

Microemulsion Encapsulated into Halloysite Nanotubes and their Applications for Cleaning of a Marble Surface

Halloysite nanotubes were used to incorporate anionic surfactant micelles and an organic solvent to generate a cleaning system to be applied in Cultural Heritage restoration. The targeted adsorption is driven by electrostatic interactions based on the nanotubes peculiar charge separation. Namely anionic species are driven to the positively charged inner surface while being prevented from interacting with the halloysite outer surface that possesses a positive charge density. The hybrid organic/inorganic emulsion was characterized by dynamic light scattering. Analysis of the autocorrelation function allowed us to define the presence of surfactant aggregates inside/outside the nanotube lumen as a function of the nanotube/surfactant ratio in an aqueous mixture. The application of this prepared emulsion for the controlled cleaning of a marble artifact is demonstrated. To this purpose, a membrane of nanofibrous polyacrylonitrile was prepared by electrospinning and was applied between the work of art and the cleaning agent to avoid the release of residues on the marble surface. This work represents a further step toward the opportunity to extend the use of emulsions for cleaning protocols for stone-based artifacts or in technological applications where surfactant separation is required by a simple centrifugation/sedimentation method.

Surface-Engineered Nanocontainers Based on Molecular Self-Assembly and Their Release of Methenamine.

The mixing of polymers and nanoparticles is opening pathways for engineering flexible composites that exhibit advantageous functional properties. To fabricate controllable assembling nanocomposites for efficiently encapsulating methenamine and releasing them on demand, we functionalized the surface of natural halloysite nanotubes (HNTs) selectively with polymerizable gemini surfactant which has peculiar aggregation behavior, aiming at endowing the nanomaterials with self-assembly and stimulative responsiveness characteristics. The micromorphology, grafted components and functional groups were identified using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The created nanocomposites presented various characteristics of methenamine release with differences in the surface composition. It is particularly worth mentioning that the controlled release was more efficient with the increase of geminized monomer proportion, which is reasonably attributed to the fact that the amphiphilic geminized moieties with positive charge and obvious hydrophobic interactions interact with the outer and inner surface in different ways through fabricating polymeric shell as release stoppers at nanotube ends and forming polymer brush into the nanotube lumen for guest immobilization. Meanwhile, the nanocomposites present temperature and salinity responsive characteristics for the release of methenamine. The combination of HNTs with conjugated functional polymers will open pathways for engineering flexible composites which are promising for application in controlled release fields.

Halloysite Nanotubes: Controlled Access and Release by Smart Gates.

Hollow halloysite nanotubes have been used as nanocontainers for loading and for the triggered release of calcium hydroxide for paper preservation. A strategy for placing end-stoppers into the tubular nanocontainer is proposed and the sustained release from the cavity is reported. The incorporation of Ca(OH)2 into the nanotube lumen, as demonstrated using transmission electron microscopy (TEM) imaging and Energy Dispersive X-ray (EDX) mapping, retards the carbonatation, delaying the reaction with CO2 gas. This effect can be further controlled by placing the end-stoppers. The obtained material is tested for paper deacidification. We prove that adding halloysite filled with Ca(OH)2 to paper can reduce the impact of acid exposure on both the mechanical performance and pH alteration. The end-stoppers have a double effect: they preserve the calcium hydroxide from carbonation, and they prevent from the formation of highly basic pH and trigger the response to acid exposure minimizing the pH drop-down. These features are promising for a composite nanoadditive in the smart protection of cellulose-based materials.

Gating-like Motions and Wall Porosity in a DNA Nanopore Scaffold Revealed by Molecular Simulations.

Recently developed synthetic membrane pores composed of folded DNA enrich the current range of natural and engineered protein pores and of nonbiogenic channels. Here we report all-atom molecular dynamics simulations of a DNA nanotube (DNT) pore scaffold to gain fundamental insight into its atomic structure, dynamics, and interactions with ions and water. Our multiple simulations of models of DNTs that are composed of a six-duplex bundle lead to a coherent description. The central tube lumen adopts a cylindrical shape while the mouth regions at the two DNT openings undergo gating-like motions which provide a possible molecular explanation of a lower conductance state observed in our previous experimental study on a membrane-spanning version of the DNT (ACS Nano 2015, 9, 1117-26). Similarly, the central nanotube lumen is filled with water and ions characterized by bulk diffusion coefficients while the gating regions exhibit temporal fluctuations in their aqueous volume. We furthermore observe that the porous nature of the walls allows lateral leakage of ions and water. This study will benefit rational design of DNA nanopores of enhanced stability of relevance for sensing applications, of nanodevices with tunable gating properties that mimic gated ion channels, or of nanopores featuring defined permeation behavior.

Capillarity-induced selective ex-situ synthesis of metal–organic framework inside mesoporous nanotubes

A general synthetic strategy to confine metal–organic frameworks (MOFs) selectively and evenly inside lumen of mesoporous nanotubes is presented. This process includes even loading of a precursor for MOF among the nanotubes in a solution phase, and following ex-situ solvothermal reaction while the precursor is suspended exclusively inside the lumen of the nanotube by capillary action, where the nanotube acts as a template as well as an ultra-small vial. The hybrid exhibits unique gas adsorption behavior, in which both microporosity and mesoporosity exist simultaneously. Confining environment of the nanotube results in a preference of the growing MOF to a specific growth direction. Enhanced water stability of inner MOF is also observed.

Regulating Ion Transport in Peptide Nanotubes by Tailoring the Nanotube Lumen Chemistry.

We use atomistic nonequilibrium molecular dynamics simulations to demonstrate how specific ionic flux in peptide nanotubes can be regulated by tailoring the lumen chemistry through single amino acid substitutions. By varying the size and polarity of the functional group inserted into the nanotube interior, we are able to adjust the Na(+) flux by over an order of magnitude. Cl(-) is consistently denied passage. Bulky, nonpolar groups encourage interactions between the Na(+) and the peptide backbone carbonyl groups, disrupting the Na(+) solvation shell and slowing the transport of Na(+). Small groups have the opposite effect and accelerate flow. These results suggest that relative ion flux and selectivity can be precisely regulated in subnanometer pores by molecularly defining the lumen according to biological principles.

Synthesis of pH-sensitive poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes for adsorption and controlled release of DPH and DS drugs

Halloysite nanotube (HNT) was functionalized with (3-Aminopropyl)triethoxysilane (APTES), alpha-bromoisobutyryl bromide (BiBB), and poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) chains. Successful grafting of PDMAEMA by SI-ATRP method was evaluated by XPS, FTIR, TEM, and TGA. Pore volume studies were accomplished by BET, and XRD was used to study crystalline structure of nanotubes. PDMAEMA coverage is formed on the outer and inner surface and also lumen of nanotubes. Sensitivity of PDMAEMA-grafted HNTs to pH was confirmed with its solution stability evaluation and also different hydrodynamic diameters in various pH values. Finally, two samples of the neat and PDMAEMA-grafted HNTs were used as diphenhydramine hydrochloride (DPH) and diclofenac sodium salt (DS) drugs carriers and their release was investigated by varying pH using UV-spectrophotometer. Grafting of PDMAEMA chains on HNT leads to controlled release of DPH molecules. Retarded release of DS molecules from PDMAEMA-grafted HNTs at lower pH values was also observed.

Tailoring the water structure and transport in nanotubes with tunable interiors.

Self-assembly of cyclic peptide nanotubes (CPNs) in polymer thin films has opened up the possibility of creating separation membranes with tunable nanopores that can differentiate molecules at the sub-nanometer level. While it has been demonstrated that the interior chemistry of the CPNs can be tailored by inserting functional groups in the nanopore lumen (mCPNs), a design strategy for picking the chemical modifications that lead to particular transport properties has not been established. Drawing from the knowledgebase of functional groups in natural amino acids, here we use molecular dynamics simulations to elucidate how bioinspired mutations influence the transport of water through mCPNs. We show that, at the nanoscale, factors besides the pore size, such as electrostatic interactions and steric effects, can dramatically change the transport properties. We recognize a novel asymmetric structure of water under nanoconfinement inside the chemically functionalized nanotubes and identify that the small non-polar glycine-mimic groups that minimize the steric constraints and confer a hydrophobic character to the nanotube interior are the fastest transporters of water. Our computationally developed experiments on a realistic material system circumvent synthetic challenges, and lay the foundation for bioinspired principles to tailor artificial nanochannels for separation applications such as desalination, ion-exchange and carbon capture.

Core-shell composite metal catalysts incased into natural ceramic nanotubes

The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface.

Enlargement of Halloysite Clay Nanotube Lumen by Selective Etching of Aluminum Oxide

Halloysite clay tubes have 50 nm diameter and chemically different inner and outer walls (inner surface of aluminum oxide and outer surface of silica). Due to this different chemistry, the selective etching of alumina from inside the tube was realized, while preserving their external diameter (lumen diameter changed from 15 to 25 nm). This increases 2-3 times the tube lumen capacity for loading and further sustained release of active chemical agents such as metals, corrosion inhibitors, and drugs. In particular, halloysite loading efficiency for the benzotriazole increased 4 times by selective etching of 60% alumina within the tubes' lumens. Specific surface area of the tubes increased over 6 times, from 40 to 250 m(2)/g, upon acid treatment.

Biomimetic Dopamine Derivative for Selective Polymer Modification of Halloysite Nanotube Lumen

We demonstrate the use of a catecholic anchor (Dopa) for selective modification of the inner surface of an halloysite clay nanotube. Aqueous Dopa binds to alumina at the tube lumen and does not bind the silica surface under the same conditions. Selectivity of surface modification was evidenced using X-ray photoelectron spectroscopy (XPS) and (13)C solid state NMR spectroscopy. Surface-initiated atom transfer radical polymerization (SI-ATRP) was performed through selectively adsorbed Dopa to graft a layer of polymer brush into the nanotube lumen.

Active Anticorrosion Coatings with Halloysite Nanocontainers

This work contributes to the development of a new generation of active corrosion protection coatings composed of hybrid sol−gel films doped with halloysite nanotubes able to release entrapped corrosion inhibitors in a controllable way. A silica-zirconia-based hybrid film was used in this work as an anticorrosion coating deposited on 2024 aluminum alloy. Halloysite nanotubes with inner voids loaded by corrosion inhibitors (2-mercaptobenzothiazole) and outer surfaces layer-by-layer covered with polyelectrolyte multilayers were introduced into the hybrid films. The sol−gel film with the nanocontainers reveals enhanced long-term corrosion protection in comparison with the undoped sol−gel film. This effect is obtained because of the self-controlled release of the corrosion inhibitor triggered by the corrosion processes. Utilization of the inner halloysite nanotube lumen as a storage medium for the corrosion inhibitor offers a novel way of fabricating composite core−shell type nanomaterials with their further a...

Halloysite Nanotubes as Biomimetic Nanoreactors

Halloysite, a naturally occurring, 50-nm-diameter tubular material, has been utilized as a new biomineralization nanoreactor to form urease-catalyzed CaCO3. The CaCO3 synthesis occurs exclusively inside the halloysite nanotubes, with no carbonate found on the outer surface of the nanotubes or in solution. Precipitated CaCO3 completely fills the inner nanotube lumen (see picture) and exhibits the metastable vaterite phase structure.