Zirconium Phosphate Nanoplatelets Research Articles

Earth-Abundant Electrocatalysts for the Oxygen Evolution Reaction Supported on Layered Zirconium Phosphate Nanomaterials

Recently, we have demonstrated improved electrocatalytic activity of layered zirconium phosphate (ZrP) nanomaterials loaded with earth-abundant metal ions suitable as catalysts for the oxygen evolution reaction (OER). We compared the catalytic efficiency of ZrP nanoparticles ion-exchanged with transition metals (Fe, Ni, Co) in the interior of the layers as well as in the external surface to a system in which the metal catalysts are confined exclusively on the external ZrP surface. Linear sweep voltammetry revealed that the electrocatalytic systems with metal catalysts on the external ZrP nanomaterials’ surface had improved OER activity compared to systems with metals intercalated in the ZrP interlayers. This result prompted us to study a system of exfoliated ZrP particles which provide only external surfaces to the electrocatalytic metal ions. A comparison between adsorbed Co or Ni catalysts on ZrP nanoparticles and those same catalysts on exfoliated ZrP nanoplatelets proved that the later systems were more active, with diminished overpotentials and reduced Tafel plot slopes. Comparison between Co and Ni catalyst on ZrP particles with different morphologies (hexagonal platelets, rods, cubes, and spheres) revealed that the more active Co catalysts are those on hexagonal ZrP platelets, whereas the best Ni catalysts are those on ZrP spheres. More recently, efficient OER catalysts were obtained with cobalt porphyrin molecular electrocatalysts both intercalated in ZrP and adsorbed on exfoliated ZrP nanoplatelets. Mixed metal NiFe-intercalated ZrP electrocatalysts at 90% Fe metal content proved to have superior OER electrocatalytic performance (decreased overpotentials, increased mass activities, reduced Tafel slopes) compared to adsorbed counterparts. We are exploring OER activities of other mixed-metal catalysts on ZrP, bifunctional catalysts, and operando synchrotron X-ray absorption spectroscopy studies to elucidate the nature of the active species.

Immobilization of Alendronate on Zirconium Phosphate Nanoplatelets

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.

Design of Poly(cyclotriphosphazene)-Functionalized Zirconium Phosphate Nanoplatelets To Simultaneously Enhance the Dynamic Mechanical and Flame Retardancy Properties of Polyamide 6.

To obtain polyamide 6 (PA6) composites with improved flame retardancy and thermomechanical properties, highly cross-linked supramolecular poly(cyclotriphosphazene)-functionalized α-zirconium phosphate (f-ZrP) nanoplatelets were synthesized and melt-blended with PA6 in a twin-screw extruder. The performance enhancements of composites were investigated through measuring the dynamic mechanical property and observing cone calorimeter data, toxic gas evolution, and UL-94 rating. The thermomechanical performance of PA6 was increased by 37.2% after composite formation with f-ZrP. As for the fire retardancy performance, compared to neat PA6, the composite containing 10 wt % f-ZrP showed 41.7 and 30.4% decrease in the peak heat and total heat release rates, respectively, and the UL-94 rating of the composite was V-0. Moreover, the thermogravimetric analysis combined with infrared spectroscopy revealed that the addition of f-ZrP to the PA6 led to decrease in the evolution of the volatile compounds and toxic gases, with the formation of highly cross-linked P–N-containing dense char with microspheres, providing a strong barrier to the inhibition of the heat and flammable volatile components transferring between the flame zone area and substrate during the combustion test. Finally, based on the obtained results, the possible mechanisms for improved mechanical and fire retardancy properties of the composites were proposed.

Modification of chiral liquid crystal polymers by charged 2D nanoplatelets towards colorful nanocomposites with tunable wetability

Chiral liquid crystal polymers (CLCPs) with spontaneous ordered structure, unique optical properties and high flexibility are promising smart materials. However, their broad application is inevitably limited by the single attribute of chiral mesophase in the cases of fabricating functional materials with multiple attributes. In this work, a novel and effective method of modifying CLCPs by charged two-dimensional (2D) zirconium phosphate (ZrP) nanoplatelets is established. ZrP nanoplatelets can be incorporated into the matrix of CLCPs by the host-guest effect. The dispersed ZrP nanoplatelets can increase the glass transition temperature due to the steric hindrance. The incorporation of ZrP nanoplatelets can increase the thermal decomposition temperature of CLCPs from 274.2 °C to 316.9 °C when the ZrP content ranging from 0 wt% to 20 wt%. The CLCP-ZrP nanocomposites exhibit typical thermochromism in the visible light region in response to temperature. The intercalation of ZrP nanoplatelets can tune the wettability of CLCPs from hydrophobicity to hydrophilicity, the contact angles are within the range from 26.25° to 110.0°. We believe the modification of CLCPs by ZrP nanoplatelets paves the way to functionalize polymer matrix by a variety of novel 2D materials, such as black phosphorus, MXenes and transition-metal dichalcogenides, and to fabricate multifunctional nanocomposites.

Hierarchical, Self-Healing and Superhydrophobic Zirconium Phosphate Hybrid Membrane Based on the Interfacial Crystal Growth of Lyotropic Two-Dimensional Nanoplatelets.

We demonstrate a facile route to in situ growth of lyotropic zirconium phosphate (ZrP) nanoplates on textiles via an interfacial crystal growing process. The as-prepared hybrid membrane shows a hierarchical architecture of textile fibers (porous platform for fluid transport), ZrP nanoplatelets (layered scaffolds for chemical barriers), and octadecylamine (organic species for superhydrophobic functionalization). Interestingly, such a hybrid membrane is able to separate the oily wastewater with a high separation efficiency of 99.9%, even at in harsh environments. After being chemically etched, the hybrid membrane is able to restore its hydrophobicity autonomously and repeatedly, owing to the hierarchical structure that enables facile loading of healing agent. We anticipate that the concept of implanting superhydrophobic self-healing features in anisotropic structure of lyotropic nanoparticles will open up new opportunities for developing advanced multifunctional materials for wastewater treatment, fuel purification, and oil spill mitigation.

Effect of Nanoplatelet Size on the Colloidal Stability of Coupled Nanocomposite of TiO2 and Zirconium Phosphate Nanoplatelets

The aggregation and sedimentation of nanoparticles affect the dispersion stability and application of nanosuspension. TiO2 nanoparticles were coupled on zirconium phosphate (ZrP) disks with different diameters to study the effect of ZrP size on the dispersion stability of nanocomposite suspensions. Four suspensions, namely, TiO2 nanosuspensions and three exfoliated TiO2 ‒ ZrP nanocomposite suspensions with diameters of 729.6, 1004.5 and 1168.5 nm were prepared. Dispersion stability was compared among the suspensions. The zeta potential, viscosity, particle morphology and particle size distribution of the suspensions were also tested to analyze the stability mechanism of the nanocomposite suspensions. Results of the stability tests within 100 days show that the TiO2 ‒ ZrP nanocomposite suspensions exhibited slower sedimentation, higher ultraviolet-visible absorbance, smaller light transmission and backscattering variation and lower Turbiscan Stability Index than those of the pure TiO2 suspension. Among the samples, the smallest TiO2 ‒ ZrP nanocomposites exhibited improved stability. The absolute zeta potential and viscosity of each nanocomposite suspension were comparable with one another, but higher than those of the TiO2 suspension. The transmission electron microscope images and particle size distribution suggest that TiO2 ‒ ZrP can better control the aggregation of small TiO2 nanoparticle clusters. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.18154

Improving the Supercooling Degree of TiO2 Suspensions by Coupling With Zirconium Phosphate Nanoplatelets

Phase-change materials (PCM) with low supercooling degree (SD) are important in cold thermal energy storage (CTES) applications. The SD of nanosuspension PCM usually decreases with increasing nanoparticle concentration. However, the performance variation of nanosuspension PCM at high concentrations has been rarely studied, though it is important because nanoparticles tend to aggregate. In this paper, the SD and dispersion stability of nanosuspensions of TiO2, zirconium phosphate (ZrP), and TiO2 coupled with zirconium phosphate (TiO2-ZrP) were investigated at nanoparticle concentrations up to 5.0 wt %. Results show that the SD of TiO2 suspension did not remarkably varied with mass concentrations above 2.0 wt %. In contrast, the SD of TiO2-ZrP and ZrP were low and continuously decreased with increasing mass concentration of nanoparticles. The dispersion stability of TiO2-ZrP suspension improved compared with that of TiO2 suspension. Hence, TiO2-ZrP suspension provided more nucleation sites than TiO2 suspension to induce heterogeneous in water.

Exfoliation of layered zirconium phosphate nanoplatelets by melt compounding

A melt compounding method to achieve the exfoliation of layered zirconium phosphate (ZrP) nanoplatelets was presented in this work. ZrP nanoplatelets were first intercalated by diglycolamine (DGA) to increase the interlayer distance and functionality. In the next melt compounding process, the cyclic anhydrides of maleic anhydride grafted polyolefin elastomers (POE-g-MA) reacted with the hydroxyls in DGA-ZrP. Subsequently, the long polyolefin chains of POE-g-MA intercalated into the interlayer of ZrP smoothly and exfoliated the nanoplatelets successfully. ZrP nanoplatelets with various sizes were fully exfoliated in POE-g-MA matrices. The modulus of elasticity of POE-g-MA was improved by the incorporation of ZrP nanoplatelets and further increased if the nanoplatelets are exfoliated. The ductility of ZrP/POE-g-MA compounds also became better, if ZrP nanoplatelets were first intercalated by DGA and then exfoliated, especially for the smaller nanoplatelets. Our work provides a general method to prepare polymer nanocomposites containing exfoliated ZrP nanoplatelets in a large scale.

Small Molecule-Assisted Exfoliation of Layered Zirconium Phosphate Nanoplatelets by Ionic Liquids.

Exfoliation of layered inorganic nanomaterials into single-layered sheets has been widely interested in materials chemistry and composite fabrication. Here, we report the exfoliation of layered zirconium phosphate nanoplatelets by using small molecule intercalating agents in ionic liquids, which opens a new platform for fabricating single-layered inorganic materials from synthetic layered compounds.

Zirconium Phosphate Nanoplatelet Potential for Anticancer Drug Delivery Applications.

Zirconium phosphate (ZrP) nanoplatelets can intercalate anticancer agents via an ion exchange reaction creating an inorganic delivery system with potential for cancer treatment. ZrP delivery of anticancer agents inside tumor cells was explored in vitro. Internalization and cytotoxicity of ZrP nanoplatelets were studied in MCF-7 and MCF-10A cells. DOX-loaded ZrP nanoplatelets (DOX@ZrP) uptake was assessed by confocal (CLSM) and transmission electron microscopy (TEM). Cytotoxicity to MCF-7 and MCF-10A cells was determined by the MTT assay. Reactive Oxy- gen Species (ROS) production was analyzed by fluorometric assay, and cell cycle alterations and induction of apoptosis were analyzed by flow cytometry. ZrP nanoplatelets were localized in the endosomes of MCF-7 cells. DOX and ZrP nanoplatelets were co-internalized into MCF-7 cells as detected by CLSM. While ZrP showed limited toxicity to MCF-7 cells, DOX@ZrP was cytotoxic at an IC₅₀ similar to that of free DOX. Meanwhile, DOX lC₅₀ was significantly lower than the equivalent concentration of DOX@ZrP in MCF-10A cells. ZrP did not induce apoptosis in both cell lines. DOX and DOX@ZrP induced significant oxidative stress in both cell models. Results suggest that ZrP nanoplatelets are promising as carriers of anticancer agents into cancer cells.

Stability of TiO2 Nanoparticles in Deionized Water with ZrP Nanoplatelets.

The stability of nanofluid is an important property that needs to be researched. In our study, a novel method using Zirconium phosphate (ZrP) discotic colloid to disperse nanoparticles was proposed for improving stability. TiO2 nanofluid was prepared by dispersing TiO2 nanoparticles into exfoliated a-ZrP suspensions at different concentrations. Scanning electron microscopy and X-ray diffraction were used to characterize the shape, average size, and components of primary ZrP nanoplatelets. The absorbance of the suspensions was measured by a UV-VIS spectrophotometer. The results show that the stability first increased, and then decreased with increasing ZrP concentration at 1 wt.% TiO2. The effect was optimal at 2 wt.% ZrP. Thus, the hindrance of nanoplatelets in the aggregation and sedimentation of nanoparticles is the main reason for improving the stability of nanofluids.

PH-responsive drug delivery system based on AIE luminogen functionalized layered zirconium phosphate nano-platelets

Aggregation-induced emission (AIE) luminogen, quaternary tetraphenylethene cation (TPEN), was successfully incorporated into layered α-zirconium phosphate (α-ZrP) by using co-precipitation method to form inorganic–organic hybrid materials. The obtained materials show the characteristic hexagonal platelet shape with the interlayer distance did not reveal significant difference compared with pure α-ZrP. In addition, the obtained hybrid materials emit strong blue emission centered at 476nm in aqueous media due to the electrostatic interactions of TPEN with the anionic framework of α-ZrP, which largely restrict their intramolecular rotation. More importantly, the materials provide a pH dependent release of doxorubicin (DOX), suggesting that AIE luminogen functionalized α-ZrP may be used as an imaging guided and pH-responsive delivery system for targeting therapy.

Dynamic Release of Antibiotic Drug Gentamicin Sulfate from Novel Zirconium Phosphate Nano-Platelets

Dynamic Release of Antibiotic Drug Gentamicin Sulfate from Novel Zirconium Phosphate Nano-Platelets

Wilkinson-type hydrogenation catalysts immobilized on zirconium phosphate nanoplatelets

Immobilized catalysts can be obtained by using a linker to bind a homogeneous catalyst to a solid support. Ideally, immobilized catalysts combine the advantages of homogeneous and heterogeneous catalysts. Porous supports such as silica result in optimal recyclability, however, the catalytic reactions are slowed down by pore diffusion. Here, non-porous zirconium phosphate nanoplatelets (ZrP) are used as support material to bridge the gap between homogeneous and immobilized catalysts. ZrP nanoplatelets provide sufficient outside surface area, while still being easily separable from the reaction mixtures. First, a phosphine linker containing an ethoxysilyl group, (EtO)3Si(CH2)3PPh2 (1), is reacted with ZrP to give the phosphine-modified 1i. Addition of Wilkinson's catalyst ClRh(PPh3)3 to 1i gives, via ligand exchange, the immobilized catalyst 1i–Rh. In the absence of pore diffusion the catalytic hydrogenation of 1-dodecene using 1i–Rh proceeds with unprecedented speed and the catalyst can be recovered and recycled 15 times. In the course of the catalytic reaction the mononuclear species forms catalytically active Rh nanoparticles on the surface. Finally it is demonstrated that ClRh(PPh3)3 can be bound to ZrP directly without linker. However, the catalytic activity of the resulting material ZrP–Rh does not quite match the favorable characteristics of 1i–Rh.

Large-scale self-assembled zirconium phosphate smectic layers via a simple spray-coating process

The large-scale assembly of asymmetric colloidal particles is used in creating high-performance fibres. A similar concept is extended to the manufacturing of thin films of self-assembled two-dimensional crystal-type materials with enhanced and tunable properties. Here we present a spray-coating method to manufacture thin, flexible and transparent epoxy films containing zirconium phosphate nanoplatelets self-assembled into a lamellar arrangement aligned parallel to the substrate. The self-assembled mesophase of zirconium phosphate nanoplatelets is stabilized by epoxy pre-polymer and exhibits rheology favourable towards large-scale manufacturing. The thermally cured film forms a mechanically robust coating and shows excellent gas barrier properties at both low- and high humidity levels as a result of the highly aligned and overlapping arrangement of nanoplatelets. This work shows that the large-scale ordering of high aspect ratio nanoplatelets is easier to achieve than previously thought and may have implications in the technological applications for similar materials.

Designable Architectures on Nanoparticle Surfaces: Zirconium Phosphate Nanoplatelets as a Platform for Tetravalent Metal and Phosphonic Acid Assemblies

Surface-functionalized zirconium phosphate (ZrP) nanoparticles were synthesized using a combination of ion exchange and self-assembly techniques. The surface of ZrP was used as a platform to deposit tetravalent metal ions by direct ion exchange with the protons of the surface phosphate groups. Subsequently, phosphonic acids were attached to the metal ion layer, effectively functionalizing the ZrP nanoparticles. Use of axially oriented bisphosphonic acids led to the ability to build layer-by-layer assemblies from the nanoparticle surface. Varying the metal ion and ligand used allowed designable architectures to be synthesized on the nanoparticle surface. X-ray powder diffraction, XPS, electron microprobe, solid-state NMR, FTIR, and TGA were used to characterize the synthesized materials.

Surface Functionalization of Zirconium Phosphate Nanoplatelets for the Design of Polymer Fillers

Inorganic-organic hybrid materials were synthesized by covalent attachment of epoxides to the surface of zirconium phosphate (ZrP) nanoplatelets. X-ray powder diffraction, FTIR, and TGA were utilized to confirm the presence of the modifiers and exclusive functionalization of the ZrP surface. NMR experiments were conducted to confirm the formation of P-O-C bonds between surface phosphate groups and epoxide rings. The applicability of the organically modified products was demonstrated by their use as fillers in a polymer matrix. Subsequently, a two step intercalation and surface modification procedure was utilized to prepare polymer nanocomposites that were imparted with functionality through the encapsulation of molecules within the interlayer of surface modified ZrP.

Zirconium phosphate nanoplatelets: a biocompatible nanomaterial for drug delivery to cancer

The objective of this study was to evaluate the biocompatibility of zirconium phosphate (ZrP) nanoplatelets (NPs), and their use in drug delivery. ZrP and doxorubicin-intercalated ZrP (DOX:ZrP) NPs were characterized by using X-Ray Powder Diffraction (XRPD), Thermogravimetric Analysis (TGA), Transmission Electron Micrography (TEM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Biocompatibility of ZrP NPs was evaluated in human embryonic kidney (HEK-293), breast cancer (MCF-7), metastatic breast cancer (MDA-MB-231), ovarian cancer (OVCAR-3), resistant cancer (NCI-RES/ADR) cells and mouse macrophage (RAW 264.7) cell lines. Hemocompatibility of ZrP NPs was evaluated with human red blood cells. Simulated body fluid (SBF) of pH 7.4 was used to determine the in vitro release of doxorubicin from DOX:ZrP NPs. Cellular uptake and in vitro cytotoxicity studies of DOX:ZrP NPs were determined in MDA-MB-231. The ZrP nanomaterial can be prepared in the 100-200 nm size range with a platelet-like shape. The ZrP NPs themselves are biocompatible, hemocompatible and showed no toxicity to the macrophage cells. ZrP NPs can intercalate high loads (35% w/w) of doxorubicin between their layers. The release of DOX was sustained for about 2 weeks. DOX:ZrP NPs showed higher cellular uptake and increased cytotoxicity than free DOX in MDA-MB-231 cells. ZrP NPs are highly biocompatible, can intercalate large amounts of drugs and sustain the release of drugs. ZrP NPs improved the cellular uptake and cytotoxicity of DOX to MDA-MB-231 cells. ZrP NPs are promising nanocarriers for drug delivery in cancer therapy.

Direct intercalation of cisplatin into zirconium phosphate nanoplatelets for potential cancer nanotherapy

We report the use of zirconium phosphate (ZrP) nanoplatelets for the encapsulation of the anticancer drug cisplatin and its delivery to tumor cells. Cisplatin was intercalated into ZrP by direct ion exchange and was tested in vitro for cytotoxicity in the human breast cancer (MCF-7) cell line. The structural characterization of the intercalated cisplatin in ZrP suggests that during the intercalation process, the chloride ligands of the cisplatin complex were substituted by phosphate groups within the layers. Consequently, a new phosphate phase with the platinum complex directly bound to ZrP (cisPt@ZrP) is produced with an interlayer distance of 9.3 Å. The in vitro release profile of the intercalated drug upon a pH stimulus shows that at low pH under lysosomal conditions the platinum complex is released with simultaneous hydrolysis of the zirconium phosphate material, while at higher pH the complex is not released. Experiments with the MCF-7 cell line show that cisPt@ZrP reduced the cell viability up to 40%. The cisPt@ZrP intercalation product is envisioned as a future nanotherapy agent against cancer. Taking advantage of the shape and sizes of the ZrP particles and controlled release of the drug at low pH, it is intended to exploit the enhanced permeability and retention effect of tumors, as well as their intrinsic acidity, for the destruction of malignant cells.

AIE cation functionalized layered zirconium phosphate nanoplatelets: ion-exchange intercalation and cell imaging

An aggregation-induced emission (AIE) probe, possessing a quaternary tetraphenylethene (TPEN) cation, was successfully intercalated into layered α-zirconium phosphate (α-ZrP) nanosheets by ion-exchange. The hybrid materials emit strong blue emissions in aqueous solution which can be used as an effective fluorescence label for HeLa cells.