Colloids and Surfaces A: Physicochemical and Engineering Aspects
Electrophoretic deposition of composite chitosan–halloysite nanotube–hydroxyapatite films
Graphical abstract
.
Highlights
► Halloysite nanotubes were electrosterically dispersed using chitosan. ► Electrophoretic deposition was developed for the fabrication of composite films. ► Chitosan–halloysite–hydroxyapatite films were deposited. ► The method allowed fabrication of monolayer, multilayer of functionally graded films. ► The films provided corrosion protection of stainless steel substrates.
Introduction
Halloysite nanotubes (HNT) are of increasing interest for the nanotechnology of advanced materials in areas as diverse as catalysis, drug delivery, biomedical implants, corrosion protection of metals, biosensors, organic synthesis, flame retardant coatings, specific ion adsorbents, materials for sustained release of herbicides and anti-microbials, energy storage devices and other areas [1], [2], [3], [4], [5]. HNT are natural clay minerals with nanotubular layered structures, containing silica and alumina layers [2], [6]. The chemical formula of HNT can be expressed as Al2Si2O5(OH)4·nH2O (n = 0–2)[2]. The outer layer of the HNT is mainly SiO2 while the inner cylinder core consists of Al2O3. It is known that silica and alumina have isoelectric points of 2 and 9, respectively [7], [8], [9]. Therefore, the electrokinetic behavior of halloysite at pH 7 is defined by the negative surface potential of SiO2, with a small contribution from the positive Al2O3 inner surface [1]. The positive (below pH 9) charge of the inner lumen promoted loading of HNT with anionic molecules or macromolecules, which at the same time repelled from the negatively charged outer surfaces [2].
A wide range of active agents, including drugs, can be entrapped within the inner lumen, as well as within void spaces of the multilayered aluminosilicate shells [2]. This entrapment can be followed by the retention and release of the agents, making halloysite a nanomaterial well suited for macromolecular delivery applications. There is an increasing interest in the use of HNT as biocompatible containers for controlled drug release and other biomedical applications [10], [11], [12]. HNT were loaded with corrosion inhibitors for the fabrication of protective coatings with advanced mechanical properties [13]. HNT were utilized as nanotemplates and nanoscale reaction vessels for the synthesis of nanomaterials [2], [14]. The use of HNT lumens as nanotemplates offers promising possibilities for the synthesis of molecular wires and nanorods [2]. Recently HNT lumens were utilized for enzyme-catalyzed inorganic synthesis [2]. HNT were used as supports for immobilization of inorganic and organic catalysts [15], [16], [17], [18] and magnetic nanoparticles [19]. HNT, loaded with corrosion inhibitors and coated with polyelectrolyte multilayers, were introduced into the silica–zirconia-based hybrid films [20], which showed good corrosion protection. The HNT reinforced composites showed advanced mechanical properties and high flame retardancy [2], [21].
Significant interest has been generated in polymer–HNT composite films and coatings [2]. The incorporation of HNT into the polymer films resulted in advanced mechanical and flame retardant properties [2], [22], [23]. Polymer–HNT composites were utilized for the fabrication of thin film biosensors [24], supercapacitors [3], biomedical implant materials and protective coatings [2]. Recent studies showed that HNT are not toxic for cells [10] and can be used for the fabrication of biocomposites with important functional properties. HNT can be loaded with drugs, antimicrobial agents and other functional materials for the fabrication of advanced polymer–HNT films with controlled release of the materials [2]. The use of HNT for the biopolymer film reinforcement offers advantage of biocompatibility and low cost [6], [10] compared to carbon nanotube reinforced biopolymer films [25], [26]. Various methods have been developed for the fabrication of polymer–HNT composite films and coatings, including solution casting [24], [27], painting [13] and self-assembly [6].
Electrophoretic deposition (EPD) is an attractive method for the deposition of composite films, containing HNT. This method is widely used for the deposition of inorganic materials, polymers and composites [28], [29], [30]. EPD is based on the electrophoretic motion of colloidal particles or polymer macromolecules under the influence of an electric field and deposit formation at the electrode surface [31], [32], [33]. EPD allows the fabrication of uniform films of controlled thickness and offers many processing advantages, such as high deposition rate and the possibility of deposition on substrates of complex shape [34], [35], [36]. Moreover, EPD is well suited for the fabrication of composite films [37], [38]. Therefore, it would be important to apply the EPD method for the fabrication of polymer films, containing HNT.
The goal of this investigation was the EPD of composite films, containing HNT. Chitosan was used for charging and dispersing of HNT in the suspensions for EPD of chitosan–HNT films. The use of chitosan as a charging, dispersing and film forming agent allowed the deposition of composite films, containing HNT and hydroxyapatite (HA) in a chitosan matrix. HA provided improved bioactivity and biocompatibility to the composites. The films were obtained as monolayers, multilayers or functionally graded composites. Experimental data were presented on the microstructure and properties of the composite films. The composite films prepared by EPD are promising materials for biomedical applications. The method developed in this investigation paves the way for the fabrication of other composite films containing HNT in a polymer matrix for various applications.
Section snippets
Experimental procedures
The following chemicals were purchased from Aldrich: chitosan (Mw = 200,000) with a degree of deacetylation of 85%, acetic acid, Ca(NO3)2·4H2O, (NH4)2HPO4, NH4OH and HNT. Chitosan was protonated and dissolved in an acetic acid solution [30]. The procedure for the preparation of stoichiometric HA nanoparticles for EPD was based on that described in a previous work [39]. Precipitation was performed at a temperature of 70 °C by a slow addition of 0.6 M ammonium phosphate solution into 1.0 M calcium
EPD of chitosan–HNT and chitosan–HNT–HA films
Fig. 2 shows a typical TEM image of HNT used in this investigation. The analysis of the TEM images indicated that HNT have relatively uniform inner and outer diameters in the range of 10–20 and 40–80 nm, respectively. SEM studies showed that the lengths of the HNT were typically in the range of 0.5–5 μm.
The suspensions of HNT were unstable and showed fast sedimentation. No EPD was achieved from such suspensions. The addition of chitosan resulted in improved suspension stability and allowed the
Conclusions
EPD method has been developed for the deposition of HNT and fabrication of composite chitosan–HNT and chitosan–HNT–HA films. The use of chitosan as a dispersing and charging agent for both HNT and HA allowed the formation of chitosan–HNT–HA monolayers, films of graded composition and multilayer laminates, containing different layers. The deposition yield and composition of the films and individual layers can be varied. The composite films provided corrosion protection of stainless steel
Acknowledgement
The authors gratefully acknowledge the financial support of the Natural Sciences and Engineering Research Council of Canada.
References (54)
- et al.
Thin film nanofabrication via layer-by-layer adsorption of tubule halloysite, spherical silica, proteins and polycations
Colloids Surf. A: Physicochem. Eng. Aspects
(2002) - et al.
Preparation and characterization of coaxial halloysite/polypyrrole tubular nanocomposites for electrochemical energy storage
Electrochim. Acta
(2010) - et al.
Thermal stability and flame retardant effects of halloysite nanotubes on poly(propylene)
Eur. Polym. J.
(2006) - et al.
Equilibrium and kinetics of 5-aminosalicylic acid adsorption by halloysite
Microporous Mesoporous Mater.
(2008) - et al.
A surface charge characterization device using sedimentation potential for single and mixed particle systems
Colloids Surf. A
(2010) - et al.
A new route to synthesis of surface hydrophobic silica with long-chain alcohols in water phase
Colloids Surf. A
(2010) - et al.
Adsorption behavior of selected monosaccharides onto an alumina interface
J. Colloid Interface Sci.
(2004) - et al.
Investigation of smart nanocapsules containing inhibitors for corrosion protection of copper
Electrochim. Acta
(2010) - et al.
Silver nanoparticle supported on halloysite nanotubes catalyzed reduction of 4-nitrophenol (4-NP)
Appl. Surf. Sci.
(2009) - et al.
Palygorskite- and halloysite–TiO2 nanocomposites: synthesis and photocatalytic activity
Appl. Clay Sci.
(2010)
Biomimetic polymerization of aniline using hematin supported on halloysite nanotubes
Appl. Catal. A: Gen.
Immobilization of enzyme biocatalyst on natural halloysite nanotubes
Catal. Commun.
Simultaneous deposition of Ni nanoparticles and wires on a tubular halloysite template: a novel metallized ceramic microstructure
J. Solid State Chem.
Direct electrochemistry and electrocatalysis of horseradish peroxidase based on halloysite nanotubes/chitosan nanocomposite film
Electrochim. Acta
Electrophoretic deposition of polymer–carbon nanotube-hydroxyapatite composites
Surf. Coat. Technol.
Electrodeposition of composite materials containing functionalized carbon nanotubes
Mater. Chem. Phys.
Cathodic electrophoretic deposition of manganese dioxide films
Colloids Surf. A
Electrodeposition of alginic acid and composite films
Colloids Surf. A
Electrodeposition of composite zinc oxide–chitosan films
Colloids Surf. A
EPD kinetics: a review
J. Eur. Ceram. Soc.
Electrophoretic deposition of carbon nanotube-reinforced hydroxyapatite bioactive layers on Ti–6Al–4V alloys for biomedical applications
Ceram. Int.
Electrophoretic deposition of lithium iron phosphate cathode for thin-film 3D-microbatteries
J. Power Sources
Electrophoretic deposition of graphene, carbon nanotubes and composites using aluminon as charging and film forming agent
Colloids Surf. A: Physicochem. Eng. Aspects
Electrodeposition of composite hydroxyapatite–chitosan films
Mater. Chem. Phys.
Degradation characteristics of hydroxyapatite coatings on orthopaedic TiAlV in simulated physiological media investigated by electrochemical impedance spectroscopy
Biomaterials
Electrophoretic deposition of composite hydroxyapatite–chitosan coatings
Mater. Charact.
Electrophoretic hydroxyapatite coatings and fibers
Mater. Lett.
Cited by (66)
Electrophoretic deposition of collagen/chitosan films with copper-doped phosphate glasses for orthopaedic implants
2022, Journal of Colloid and Interface ScienceDip coating of poly(ethyl methacrylate) and composites from solutions in isopropanol-water co-solvent
2021, Colloids and Surfaces A: Physicochemical and Engineering AspectsInfluence of chemical structure of bile acid dispersants on electrophoretic deposition of poly(vinylidene fluoride) and composites
2021, Colloids and Surfaces A: Physicochemical and Engineering AspectsConducting Polymer-Based Nanocomposites: Fundamentals and Applications
2021, Conducting Polymer-Based Nanocomposites: Fundamentals and ApplicationsInsights into grafting of (3-Mercaptopropyl) trimethoxy silane on halloysite nanotubes surface
2020, Journal of Organometallic Chemistry