Surface-modified Halloysite Nanotubes Research Articles

Development of corrosion-resistant epoxy coating by hydrophobically surface-modified halloysite nanotubes using trimethylchlorosilane and 1,1,1,3,3,3-hexamethyldisilazane

Development of corrosion-resistant epoxy coating by hydrophobically surface-modified halloysite nanotubes using trimethylchlorosilane and 1,1,1,3,3,3-hexamethyldisilazane

(Invited, Digital Presentation) Maximizing the Layered Structure and Interlayer Anion Exchange Characteristics of Nico-Based Layered Double Hydroxides for Battery-Type Supercapacitors

The transition metal-based layered double hydroxides (LDHs) have been extensively studied as promising electrode materials for battery-type supercapacitors owing to their excellent electrochemical activity and tunable chemical composition. In our work, we firstly built a novel three-dimensional composite with a core-shell structure by self-assembling NiCo-LDHs nanosheets on dual surface-modified halloysite nanotubes (D-HNTs) via in-situ electrodeposition and hydrothermal method (NiCo-LDH/D-HNTs). HNTs were pretreated by a dual surface modification for the first time including a carbonization process and cobalt doping to enhance electrical conductivity and chemical stability. This multicomponent hierarchical nanocomposite, NiCo-LDH/D-HNTs, has a specific capacity of 1401.4 C g-1 at 1 A g-1, a rate capability of 52.9% increasing the current density to 30 A g-1, and cycling stability of 80.8% after 2000 cycles. Moreover, using acetate anions (Ac-) as intercalating element, the NiCo-LDH nanosheets arraying on Ni Foam were prepared with the optimized amount of Ac- anions expanding the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g-1 at 1 A g-1 (690 C g-1 without Ac- anions), outstanding rate capability of 72.5% at 30 A g-1 and cycle stability of 79.90% after 4500 cycles were achieved. The enlarged interlayer spacing was beneficial for stabilizing the α-phase of LDH and accelerating the electron transport and electrolyte penetration in the electrochemical reaction. In addition, ionic surfactants like sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) were introduced to regulate the morphology of LDHs and alter the electrochemical performance. The original NiCo-LDHs shows microspheres formed by nanorods, and NiCo-LDHs-CTAB is similar, yet more tangled, while NiCo-LDHs-SDS is like microflowers consisting of interwoven nanosheets. NiCo-LDHs-SDS achieved better electrochemical performance (1003.6 C g-1 at 1 A g-1 and 73.84% after 3500 cycles) than NiCo-LDHs-CTAB (430.54 C g-1, 57.3%), and both higher than original NiCo-LDHs (278.5 C g-1, 54.3%), clearly showing the importance of morphology regulation in the synthesis of nanomaterials. Our work offers a promising strategy to synthesize functional nanomaterials with excellent electrochemical performance via integrating its unique layered structure and interlayer anion exchange characteristics.

Halloysite nanotubes-decorated electrospun biobased polyamide scaffolds for tissue engineering applications

As a versatile and scalable technology, electrospinning is capable of fabricating polymer composite nanofibers, which have a wide range of applications in bioengineering, filtration, textiles, and other fields. In this study, dopamine was used to modify the surface of halloysite nanotubes (HNT), and the polydopamine (PDA) layer was used to promote the grafting of silane coupling agent on the surface of HNT. The surface of HNT was successfully modified by PDA coating and grafted with the silane coupling agent. Modified HNT (PDA@HNT-V) reinforced polyamide 56 (PA56) nanofibers were successfully synthesized through facile electrospinning method. Compared with the unmodified PA56 nanofibers, the tensile strength of the PA56/PDA@HNT-V composite fibers is increased by 67%, and the thermal stability is improved. Surface functional modification of PDA@HNT-V effectively improves the dispersion and compatibility with the PA56 matrix. Surface-modified HNT have a positive effect on the morphology and mechanical properties of electrospun PA56 nanofibers. Biological characterization confirmed the biocompatibility and low toxicity of PA56/PDA@HNT-V nanofiber scaffolds. In summary, the results obtained from this study demonstrated the potential of PA56/PDA@HNT-V nanofiber scaffolds for bone tissue engineering applications.

A Hierarchical Nico-LDH/Hnt Nanocomposite with a Core-Shell Structure for High-Performance Battery-Type Supercapacitor

Nickel cobalt layered double hydroxides (NiCo-LDHs) show great potential as electrode materials of battery-type supercapacitors, while the intrinsic low conductivity and possible agglomeration limit its wider application. In this work, a hierarchical composite material with a core-shell structure was prepared by self-assembling NiCo-LDHs nanosheets on dual surface-modified halloysite nanotubes (D-HNTs) via in-situ electrodeposition and hydrothermal method. HNTs were pretreated by a dual surface modification for the first time including a carbonization process and cobalt doping to enhance electrical conductivity and chemical stability. This multicomponent nanocomposite, NiCo-LDH/D-HNTs, shows a three-dimensional construction and has a specific capacity of 1401.4 C g-1 at 1 A g-1, a rate capability of 52.9% increasing the current density to 30 A g-1, and cycling stability of 80.8% after 2000 cycles. With the tubular support, the electrochemical properties of NiCo-LDHs can be extended in addition with the pseudocapacitance of HNTs. Besides the excellent electrochemical performance and the green preparation process, NiCo-LDH/D-HNTs nanocomposites possess many advantages of abundance in nature, hydrophilicity, low cost and scalability. This nanocomposite can be considered as a promising, environmentally friendly, and cost-effective electrode material for supercapacitors and other energy storage devices.

A three-dimensional NiCo-LDH array modified halloysite nanotube composite for high-performance battery-type supercapacitor

Battery-type supercapacitors have aroused great interest in the field of energy storage devices and nickel cobalt layered double hydroxides (NiCo-LDHs) show great potential as electrode materials. However, the intrinsic low conductivity and possible agglomeration limit a wider application. In this work, a novel three-dimensional composite material (NiCo-LDH/D-HNTs) with a core-shell structure was prepared by self-assembling NiCo-LDHs nanosheets on dual surface-modified halloysite nanotubes (D-HNTs) via in-situ electrodeposition and hydrothermal method. HNTs were pretreated by a dual surface modification for the first time including a carbonization process and cobalt doping to enhance electrical conductivity and chemical stability. This multicomponent hierarchical nanocomposite, NiCo-LDH/D-HNTs, has a specific capacity of 1401.4 C g-1 at 1 A g-1, a rate capability of 52.9% increasing the current density to 30 A g-1, and cycling stability of 80.8% after 2000 cycles. With the tubular support, the electrochemical properties of NiCo-LDHs were extended in addition with the pseudocapacitance of HNTs. Besides the excellent electrochemical performance, NiCo-LDH/D-HNTs nanocomposites possess many advantages of abundance in nature, hydrophilicity, low cost and scalability. NiCo-LDH/D-HNTs nanocomposite can be considered as a promising, environmentally friendly, and cost-effective electrode material for supercapacitors and other energy storage devices.

Mechanical and thermal performance of PEEK/PEI blend matrix reinforced with surface modified halloysite nanotubes

The present research work investigates the effect of modified halloysite nanotubes (mHNTs) on the mechanical, thermal, and morphological properties of polyether ether ketone (PEEK) and polyetherimide (PEI). The developed PEEK/PEI blend matrix with 1 wt% of mHNTs shows a significant enhancement in mechanical properties like tensile, flexural, hardness, and impact. The developed blend matrix of PEEK/PEI matrix with mHNTs shows a significant enhancement of 25% in storage modulus (E′) and 13°C in glass transition temperature (Tg). In addition, an appreciable improvement of 26°C observed in maximum degradation temperature (Tmax). The effectiveness of the dispersion of mHNTs in the PEEK/PEI blend matrix was investigated by using SEM and TEM micrographs. The micrographs revealed that the mHNTs are uniformly dispersed in the PEEK/PEI matrix. The possible interaction of HNTs with PEEK/PEI and mHNTs with PEEK/PEI matrix were analyzed by Fourier Transform Infrared Spectroscopy (FTIR).

Surface-Modified Halloysite Nanotubes as Electrochemical CO2 Sensors

The outer surface of halloysite nanotubes (HNTs) was selectively modified using (3-aminopropyl)triethoxysilane (APTES) via a self-assembled monolayer (SAM) method. The product of this reaction, ami...

Surface modified halloysite nanotubes with different lumen diameters as drug carriers for cancer therapy.

Paclitaxel (PTX) is successfully loaded by surface modification of distearoyl phosphoethanolamine (DSPE) on halloysite nanotubes (HNTs) with different inner lumen diameters. Drug loading of DSPE-HNTs-PTX attains 18.44% of DSPE content with a nearly complete release (near 100%) achieved. The anticancer efficacy (cell viability less than 52%) of DSPE-HNTs15-PTX increased and is attributed to the lower interfacial energy both inside and outside the tubes that improves tube loading.

Rational Design of Halloysite Surface Chemistry for High Performance Nanotube-Thin Film Nanocomposite Gas Separation Membranes.

The interfacial region has a critical role in determining the gas separation properties of nanofiller-containing membranes. However, the effects of surface chemistry of nanofillers on gas separation performance of thin film nanocomposite (TFN) membranes, prepared by the interfacial polymerization method, have been rarely studied in depth. In this work, pristine and three differently surface-modified halloysite nanotubes (HNTs), by non- (SHNT), moderately (ASHNT), or highly CO2-philic (SFHNT) agents, are embedded in the polyamide top layer of thin film nanocomposite (TFN) membranes for CO2/N2 and CO2/CH4 separations. Trimethoxyoctyl silane, 3-(2-aminoethylaminopropyl)trimethoxysilane, and poly(styrenesulfonic acid) are used as modifying agents to quantitatively investigate the effects of interfacial interactions between the polyamide and HNTs on the gas permeation of TFNs. This allows us to provide an interfacial design strategy to fabricate high-performance gas separation membranes. Pure gas permeations conducted on the TFNs at the feed gas pressure of 10 bar showed that CO2 permeance and CO2/N2 and CO2/CH4 selectivities were increased by 145%, 130%, and 108%, respectively, after addition of 0.05 w/v% of sulfonated HNTs. The experimental gas permeations through all TFNs/HNTs, except TFNs/SFHNTs, agree well with predictions of a recently developed model, which suggests the importance of considering the neglected role of CO2 interactions with the HNT/polyamide interface in the model. These results unambiguously proved that designing the interfacial layer thickness in the nanotube-containing membranes is an effective approach to tuning the gas separation properties. The results show that the dispersion of HNTs in the polyamide top layer and the experimental CO2/gas selectivity was increased with increasing interfacial thickness, aint, upon surface modification. Moreover, it is quantitatively demonstrated that the thickness of the interfacial layer between the filler and polymer matrix is a function of gas pressure applied on the membrane.

Characterization of Surface-Modified Halloysite Nanotubes by Thermal Treatment Under Reducing Atmosphere.

In recent years, the halloysite (Al₂Si₂O5(OH)₄ · 2H₂O) has been highlighted owing to its naturally occurring one-dimensionalmicrostructure that enables versatile applications. Due to the demand for enhancing surface interaction, several types of research such as acid/base treatments have been conducted on the halloysite nanotubes. The objective of this study is to investigate the structural and surface properties of thermally treated halloysites under reducing atmosphere. The heat treatment is carried out in a gas-flow furnace at 400-800 °C under various atmosphere, e.g., ambient air, 4% H₂-balanced Ar, and 99.99% H₂. The thermal treatment of halloysites under reducing atmosphere show a similar phase transition around 500 °C as the heating under air. However, the halloysite reduced in pure hydrogen shows a significant increase of the zeta-potential, -36.7 mV for a 600 °C-treated sample, compared to the other samples. The mechanisms of the zeta-potential increase for the halloysite was also explored.

Cytocompatibility and cellular uptake of alkylsilane-modified hydrophobic halloysite nanotubes

The extensive increase of application of surface-modified halloysite nanotubes in industry and biomedicine suggests that their biocompatibility and cellular uptake should be thoroughly investigated. Here we report the fabrication and cytocompatibility study of hydrophobic halloysite nanotubes coated with octadecyltrimethoxysilane (ODTMS). The interaction of ODTMS-modified halloysite nanotubes with human lung carcinoma alveolar epithelial cell A549 was investigated using dark field and atomic force microscopies, colorimetric viability tests and flow cytometry. Halloysite with different degrees of hydrophobicity penetrates into the human lung cells without membrane damage promising for efficient drug delivery. This formulation did not have an apoptosis-inducing effect on the cells, did not increase the activity of NO-synthase and can be employed for intracellular delivery of drugs, proteins and DNA without any toxic side effects.

Surface-modified halloysite nanotubes as fillers applied in reinforcing the performance of polytetrafluoroethylene

ABSTRACTIn order to improve the dispersibility of halloysite nanotubes (HNTs) in polytetrafluoroethylene (PTFE), the modification of HNT surfaces was studied with three types of modifiers (polymethyl methacrylate [PMMA], sodium dodecyl sulfate [SDS] and carboxylic acid). The modified HNTs were characterized by Fourier-transform infrared (FTIR) spectrometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and contact angle measurements. The HNTs were used to reinforce the mechanical properties of PTFE. The mechanical results indicated that the tensile strength of the modified HNT-filled PTFE nanocomposites (F-HNT/PTFE) improved to an acceptable degree and Young's modulus increased significantly. The tribological results showed that the wear rate of F-HNT/PTFE decreased by 21–82 and 9–40 times compared to pure PTFE and the pristine F-HNT/PTFE, respectively.

Improvement of mechanical and thermal properties of poly(3-hydroxybutyrate) (PHB) blends with surface-modified halloysite nanotubes (HNT)

Abstract The effect of two hydrophobic treatments on the hydrophilic nature of halloysite nanotubes (HNT) was studied in this research work: a silanization with (3-glycidyloxypropyl) trimethoxysilane (GLYMO) and a surface treatment with a natural aromatic compound, i.e. caffeic acid (CA). In addition, the effect of 3 wt% of unmodified HNT, silanized HNT (HNTSIL) and caffeic acid-modified HNT (HNTCA) on mechanical, thermal and morphological properties of a binary blend of poly(3-hydroxybutyrate) (PHB) and poly(e-caprolactone) (PCL) with a weight ratio of 75/25, respectively was evaluated. These blends and their corresponding composites with HNT were partially compatibilized by reactive extrusion with dicumyl peroxide (DCP) and further processed by injection molding. The effectiveness of the surface treatments on HNT was followed by Fourier transformed infrared spectroscopy (FTIT), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and contact angle measurements. The obtained results suggested a clear hydrophobizing effect of both surface treatments on HNT but the hydrophobic nature the caffeic acid treatment can provide to HNT is greater than silanization. FESEM study on HNT-loaded PHB/PCL blends showed increased compatibility between modified-HNT and the polymeric matrix, as well as a better particle dispersion. In particular, 3 wt% HNTCA lead to an increase in tensile strength and elongation at break of 11.4% and 74%, respectively, with regard to composites with unmodified HNT. In addition, thermal analysis, evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), revealed a decrease in the melt peak temperature of 6.5 °C for composites with 3 wt% HNTCA as well a delay in the onset degradation temperature, thus leading to a broader processing window which enhances PHB processing by conventional techniques.

Polyurethane Nanocomposites Reinforced with Surface Modified Halloysite Nanotubes

Polyurethane Nanocomposites Reinforced with Surface Modified Halloysite Nanotubes

Epoxidation of alkenes efficiently catalyzed by Mo salen supported on surface-modified halloysite nanotubes

Halloysite-nanotube-supported Mo salen (HNTs-Mo-SL) catalysts were successfully prepared using a facile chemical surface modification and self-assembly method. The morphologies, sizes, structure, and dispersion of the as-prepared catalysts were investigated by transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared, inductively coupled plasma, and X-ray photoelectron spectroscopy, which confirmed the existence of the Mo salen structure and successful synthesis of the HNTs-Mo-SL catalyst. The immobilized catalyst was found to be highly reactive in the epoxidation of a wide range of alkenes, including linear, cyclic, and aromatic alkenes. The immobilized catalyst exhibited a higher catalytic activity for alkene epoxidation than homogeneous Mo. In contrast experiments, it was determined that the salen structure played an important role in immobilizing MoO(O2)2(DMF)2 and improving the conversion and efficiency of alkene epoxidation, which could not be obtained using other ligands, such as the N atom as a single ligand. Furthermore, the bonding between Mo and the salen ligands and the possible mechanism of alkene epoxidation catalyzed by the catalyst were determined. The catalyst could be reused several times without significant loss of catalytic activity. Given that halloysite nanotubes are cheap and easy to obtain, this catalyst offers a novel alternative for the rational design of catalysts with desired features.

Preparation and characterization of polycarbonate nanocomposites based on surface-modified halloysite nanotubes

Halloysite nanotubes (HNTs) modified by a chemical vapor adsorption (CVA) process remarkably improve the thermal stability of polycarbonate nanocomposites. HNTs were modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS) and n-octadecyltrimethoxysilane (OTMS) using a CVA process. Both Fourier-transform infrared spectroscopy and thermogravimetric analysis showed that the modifiers were immobilized on the HNT surfaces. Polycarbonate (PC)/HNT nanocomposites were prepared with the modified HNTs by a combination of solution mixing, precipitating and compression molding. The dispersion states of modified HNTs in PC nanocomposites were observed by optical microscopy, scanning electron microscopy and transmission electron microscopy. The storage modulus (E′) and thermal stability of the PC nanocomposites were enhanced by the modified HNTs. OTMS-modified HNT/PC nanocomposites showed higher performance than AEAPS-modified HNT/PC nanocomposites due to the stronger affinity of the hydrophobic alkyl groups of OTMS for the polymer matrix.

How aphids lose their marbles.

Insects provide examples of many cunning stratagems to cope with the challenges of living in a world dominated by surface forces. Despite being the current masters of the land environment, they are at constant risk of being entrapped in liquids, which they prevent by having waxy and hairy surfaces. The problem is particularly acute in an enclosed space, such as a plant gall. Using secreted wax to efficiently parcel and transport their own excrement, aphids were able to solve this problem 200 Myr ago. Here, we report on the physical and physiological significance of this ingenious solution. The secreted powdery wax has three distinct roles: (i) it is hydrophobic, (ii) it creates a microscopically rough inner gall surface made of weakly compacted wax needles making the gall ultra-hydrophobic, and (iii) it coats the honeydew droplets converting them into liquid marbles, that can be rapidly and efficiently moved.