Layered Α-zirconium Phosphate Research Articles

Hydrothermal synthesis of layered zirconium phosphates and their intercalation properties

ABSTRACT Layered inorganic materials are widely used as fillers in nanocomposites due to their unique properties such as mechanical performance, thermal properties, flame resistance, barrier properties, corrosion resistance, catalytic activity, and multifunctionality. Among them, layered α-zirconium phosphate (α-ZrP: Zr(HPO4)2H2O) is one of the representative inorganic materials and unique properties with P–O–H groups that can exchange inorganic and organic cations and intercalate basic molecules. This paper deals with the use of this compound as an adsorbent for heavy metal cations in wastewater. Samples were prepared by hydrothermal treatment at various Zr/P ratio, water amounts, and temperatures. Furthermore, an attempt was made to widen the interlayer distance of the sample using n-butylamine. The α- zirconium phosphate prepared at 160°C for 20 h with Zr/P = 1/2 adsorbed the most amount of metal ions. Furthermore, interlayer amine modification was effective. Then, the behaviour of the adsorption process was observed by varying the time of adsorption from 1 h to 50 h, in order to clarify the change in adsorption of the samples over time.

Stabilization of α-ZrP ceramic nanosheets adsorbing quaternary ammonium ions in organic solvents and their application as a stable solid support for lipase catalyzing stereospecific synthetic reactions

ABSTRACT Herein, the effect of immobilizing lipase onto layered α-zirconium phosphate ceramic nanosheets (α-ZrP NS) on the enzymatic transesterification of allylic alcohols was investigated in organic solvents. α-ZrP NS modified with quaternary ammonium ions show a excellent dispersion stability in n-hexane. Lipase immobilized on α-ZrP NS enables the improved synthesis of chiral allylic alcohols and esters, with significantly reduced reaction times compared to reactions performed in the absence of α-ZrP NS. The coexistence of α-ZrP NS also results in more efficient steric inversion of the resulting allyl ester, suggesting the utility of α-ZrP NS as a support for lipase-induced stereospecific reactions. The present manuscript discusses on mechanisms of high dispersion stability of α-ZrP NS and their preferable immobilizing effect for the lipase inducing the steric inversion in detail.

A new challenge for nanocrystalline α-zirconium phosphate: reaction with a diepoxyalkane.

New organic derivatives of α-zirconium phosphate (ZrP) were prepared by reaction of a gel of nanocrystalline ZrP with 1,2,7,8-diepoxyoctane (diepoxide), leading to the formation of P-O-C bonds. A series of compounds having composition Zr(O3POH)2-2x(O3POCH2CH(OH)(CH2)4CH(OH)CH2OPO3)x (hereafter indicated as ZrP(dep)x) were obtained by varying the diepoxide/Zr molar ratio in the range 0.25-1. The samples were characterized by elemental, thermal and X-ray powder diffraction analysis. The reaction turned out to be nearly quantitative, the x values of ZrP(dep)x being in the range 0.16 to 1.0. The interlayer distance slightly increased with increasing x, going from 12.7 to 13.2 Å. Interestingly, the materials easily intercalated alkanols at room temperature, both from liquid and vapor phases; it is noteworthy that ZrP(dep)0.30 was able to reversibly take up 42 wt% ethanol from the vapor phase, in agreement with the presence of available free space both in the interlayer and in the intercrystal region. Geometrical structural models in which the α-ZrP layers are connected by the dep chains were proposed to support the obtained results.

Unique protonation behavior of cationic free-base porphyrins in the interlayer space of transparent solid films comprising layered α-zirconium phosphate

The protonation behavior of α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin (H2TMPyP) in the interlayer space of transparent solid films comprising layered α-zirconium phosphate was investigated. It was found that the exposure of H2TMPyP-impregnated films to aqueous HCl resulted in pyrrole group protonation and induced a color change from yellow to greenish yellow. The two pKa values of H2TMPyP, determined as 2.4 and 2.6, exceeded those determined in aqueous solution (0.80 and 2.06), which was attributed to the condensation of H+ in the interlayer space caused by the cation exchange reaction between H+ in the aqueous solution and n-butylamine intercalated in the interlayer space.

Enhanced mechanical and tribological performance of PA66 nanocomposites containing 2D layered α-zirconium phosphate nanoplatelets with different sizes

Two-dimensional layered α-zirconium phosphate (ZrP) nanoplatelets with two distinguished sizes but similar aspect ratio were directly incorporated into polyamide 66 (PA66) by simple melt processing without using any surfactants. Through the electron microscopy analysis, the large ZrP nanoplatelets with ~ 1.33 μm in size and ~ 5.8 in aspect ratio exhibit a uniform dispersion in PA66 matrices at the filler loading up to 3 wt%, while the small ZrP nanoplatelets with an average size of ~ 230 nm and aspect ratio of ~ 6.2 tend to form large-scale aggregates in PA66 even at 1 wt% loading. Tensile testing results illustrate that the large ZrP nanoplatelets exhibit a better reinforcement effect in PA66 than the small ones. With the incorporation of 3 wt% large ZrP nanoplatelets, the PA66 nanocomposites exhibit an increase of ~ 10% in tensile modulus and ~ 14% in tensile strength as compared with the pure PA66. Pin-on-disc wear tests illustrate that the nanocomposites containing large ZrP nanoplatelets have better anti-wear properties than those prepared with small ZrP nanoplatelets. In specific, the PA66 nanocomposites containing 1 wt% large ZrP nanoplatelets show a ~ 43% decrease in friction coefficient and a ~ 59% reduction in the wear rate under the test condition of 40 N in load and 0.6 m/s in velocity. The mechanisms that are responsible for the mechanical and tribological enhancements in the PA66/ZrP nanocomposites have also been discussed.

Layered α-zirconium phosphate: An efficient catalyst for the synthesis of solketal from glycerol

α-zirconium phosphate is widely used as a solid acid catalyst or a catalyst support. In this work, layered crystalline α-zirconium phosphates were synthesized via a facile hydrothermal method and applied in the synthesis of solketal from acetalization of glycerol with acetone. It was found that ZrP-200 (layered α-zirconium phosphate that calcined at 200 °C) is highly active and selective among the tested catalysts. ZrP-200 exhibits both high catalytic efficiency (with an 85.7% conversion of glycerol and a 98.6% selectivity of solketal at 50 °C and 3.0 h) and excellent stability even under mild condition. A series of characterizations results disclose that the performance of ZrP catalysts depends mainly on its surface density of acid sites.

Nano-Brick Wall Architectures Account for Super Oxygen Barrier PET Film by Quadlayer Assembly of Polyelectrolytes and α-ZrP Nanoplatelets.

Nanobrick wall hybrid coating with super oxygen barrier properties were fabricated on polyethylene terephthalate (PET) film using a quadlayer (QL) assembly of polyelectrolytes and nanoplateles. A quadlayer assembly consists of three repeat units of polyacrylic acid (PAA), poly (dimethyl diallyl ammonium chloride) (PDDA) and layered α-zirconium phosphate (α-ZrP). PDDA with positive charges can assemble alternatively with both α-ZrP and PAA with negative charges to form nanobrick wall architectures on the surface of PET film via the electrostatic interaction. The lamellar structure of α-ZrP platelets and the dense QL assembly coating can greatly reduce the oxygen transmission rate (OTR) of PET film. Compared to pristine PET film, the OTR of PET (QL)19 is reduced from 57 to 0.87 cc/m2/day. Moreover, even with 19 QLs coating, PET (QL)19 composite film is still with an optical transparency higher than 90% and a haze lower than 10%. Therefore, the transparent PET (QL)n composite films with super oxygen barrier properties show great potential application in food packaging and flexible electronic packaging.

CsxH3-xPW12O40 nanoparticles dispersed in the porous network of Zr-pillared α-zirconium phosphate as efficient heterogeneous catalyst for synthesis of spirooxindoles

Layered α-zirconium phosphate (α-ZrP) was prepared by reflux method using ZrOCl2.8H2O and H3PO4 as precursor. The α-ZrP material was pillared with Zr-oxyhydroxy nanoclusters to prepare Zr-pillared α-zirconium phosphate (ZZP). An enhancement in interlayer spacing, surface area and porosity was noticed as a result of Zr-pillaring. The cesium exchanged phosphotungstic acid (CsxH3-xPW12O40) nanoparticles were dispersed in the porous matrix of ZZP material to prepare CsxH3-xPW12O40-ZZP nanocomposite systems. The nanocomposites were characterized using XRD, FTIR, UV–vis-DRS, TGA-DTA, XPS, N2 sorption, TPD, FESEM and HRTEM techniques. The expansion in layer structure of α-ZrP upon pillaring and its subsequent retention in the composite material was noticed from XRD. UV–vis and FTIR study indicated structural integrity of the CsxH3-xPW12O40 nanoclusters in the ZZP interlayer. The surface area of the composite materials was in the range of 80–130 m2 g−1. The composite materials contained significantly higher amount of medium and strong acidic sites compared to the ZP and ZZP materials. Microscopic study suggested the presence of hierarchical nanospheres with diameter between 150 and 200 nm. The presence of well dispersed CsxH3-xPW12O40 nanoparticles with size between 8 and 15 nm was confirmed from HRTEM study. The nanocomposite materials were used as efficient heterogeneous catalyst for synthesis of spirooxindoles by multicomponent one pot condensation of isatin, malononitrile, naphthol/1,3-diketones. Structurally diverse spirooxindole derivatives were synthesized in high yield and purity in short span of time using the CsxH3-xPW12O40-ZZP nanocomposites as catalyst under mild conditions.

Luminescent hybrid composites based on the intercalation of Eu(iii) complexes into α-zirconium phosphate nanoplatelets: preparation, characterization and amine sensing

A direct ion-exchange approach was adopted to intercalate ionic lanthanide complexes into layered α-zirconium phosphate.

Enhanced mechanical properties of Nylon6 nanocomposites containing pristine α-zirconium phosphate nanoplatelets of various sizes by melt-compounding

Nylon6 nanocomposites containing pristine layered α-zirconium phosphate (ZrP) nanoplatelets of various sizes have been fabricated by a simple and direct melt-compounding method without adding intercalation or exfoliation agents.

Preparation of luminescent layered zirconium phosphate nanocomposites by the layer-by-layer technique

In the present work, photoactive cation N, N′-Dimenthyl-9, 9’-bisacridinium nitrate (BNMA) was assembled with exfoliated layered α-zirconium phosphate (α-ZrP) via an electrostatic layer-by-layer (LBL) assembly method. As a result, the luminescent films which were well-aligned and periodical had been successfully fabricated. Surprisingly, the lifetimes of (BNMA/ZrP)n were found to be prolonged by 16-fold for the first time, due to the isolation effect of inorganic nanosheets and hydrogen ion migration between the interlayers. Therefore, it is testified that α-ZrP can be used as the laminate and has remarkable influences on enhancing the lifetimes of chromophores. We expect that this new discovered effect can enable α-ZrP a kind of new potential material to develop novel light-emitting materials and optical devices.

Small is beautiful: the unusual transformation of nanocrystalline layered α-zirconium phosphate into a new 3D structure.

Nanosized α-zirconium phosphate, α-ZrP, undergoes a phase transition at 120 °C, which is not observed with microcrystalline α-ZrP in the same conditions, and which leads to a new 3D phase. The new compound, with formula Zr(HPO4)2 (τ'-ZrP), consists of cubelike nanoparticles and has a tetragonal unit cell (space group P43212, a = 7.955 Å, c = 10.744 Å). The structure of τ'-ZrP is in close relationship with that of the already known τ-ZrP. Both structures are made of packed chains of eight-membered rings, composed of Zr atoms connected to bridging HPO4 groups. The main difference between the two structures concerns the different orientation of the uncoordinated P-OH groups, pointing into the channels. The in situ XRPD analysis on nanosized α-ZrP, performed at 120 °C as a function of time, provided information about the kinetics of the formation of τ'-ZrP, showing that the α-ZrP phase is directly transformed into τ'-ZrP. Moreover, τ'-ZrP is converted into α-ZrP at room temperature in the presence of water vapor. It was proved that the free phosphoric acid, which is originally present in small amounts in nanosized α-ZrP and τ'-ZrP, is necessary for the interconversion between the two phases. As a matter of fact, the removal of phosphoric acid, by washing α-ZrP and τ'-ZrP with anhydrous ethanol, inhibits the above conversion.

Study on the antibacterial mechanism of copper ion- and neodymium ion-modified α-zirconium phosphate with better antibacterial activity and lower cytotoxicity

To improve the antibacterial activity of Cu2+, a series of Cu2+ and/or Nd3+-modified layered α-zirconium phosphate (ZrP) was prepared and characterized, and the antibacterial activities of the prepared Cu2+ and/or Nd3+-modified ZrP on Gram-negative Escherichia coli were investigated. The results showed that the basal spacing of ZrP was not obviously affected by the incorporation of Cu2+, but the basal spacing of the modified ZrP changed into an amorphous state with increasing additions of Nd3+. An antibacterial mechanism showed that Cu2+ and Nd3+ could enter into E. coli cells, leading to changes in ion concentrations and leakage of DNA, RNA and protein. The Cu2+- and Nd3+-modified ZrP, combining the advantages of Cu2+ and Nd3+, displayed excellent additive antibacterial activity and lower cytotoxicity, suggesting the great potential application as an antibacterial powder for microbial control.

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.

Sulfonic Acid-Functionalized α-Zirconium Phosphate Single-Layer Nanosheets as a Strong Solid Acid for Heterogeneous Catalysis Applications

Solid acids have received considerable attention as alternatives to traditional corrosive and hazardous homogeneous acids because of their advantages in practical applications, including their low corrosion of equipment and high catalytic activity and recyclability. In this work, a strong solid acid was prepared by anchoring thiol group terminated chains on layered α-zirconium phosphate (ZrP) single-layer nanosheets, followed by oxidation of thiol groups to form sulfonic acid groups. The obtained solid acids were thoroughly characterized and the results proved that sulfonic acid group terminated chains were successfully grafted onto the ZrP nanosheets with a high loading density. Such a strong solid acid based on inorganic nanosheets can be well-dispersed in polar solvents, leading to high accessibility to the acid functional groups. Meanwhile, it can be easily separated from the dispersion system by centrifugation or filtration. The strong solid acid can serve as an effective heterogeneous catalyst for various reactions, including the Bayer-Villiger oxidation of cyclohexanone to ε-caprolactone in the absence of organic solvents.

A novel potential-responsive ion exchange film system for heavy metal removal

In this study, we report on a novel potential-responsive hybrid film system for heavy metal removal, which was composed of a layered α-zirconium phosphate (α-ZrP) nanosheet and a conducting polyaniline (PANI)-intercalated chain that functioned as a proton pumping element. The proposed system features a quick responsive uptake/release rate that was about 10 times the adsorption/desorption rate with an open circuit. The potential-responsive film system exhibited a high electroactivity because of an acidic micro-environment for the nitrogen atoms in the PANI chains due to protons available on the electronegative α-ZrP nanosheets and their ion exchangeability. The uniform and dense hybrid film was formed on platinum electrodes using a one-step electrosynthesis based on unipolar pulse electrodeposition (UPED). By simply switching the operating potential applied to the electrode, heavy metal uptake onto the film from aqueous solutions and metal release for film regeneration were accomplished. This film system is shown to be a promising alternative to conventional techniques for heavy metal capture from wastewater.

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.

Hydrothermal synthesis of layered α-zirconium phosphate disks: control of aspect ratio and polydispersity for nano-architecture

The crystals of layered compounds are normally in the shape of disks or plates. Systematic experiments revealed that regular-shaped α-zirconium phosphate crystalline disks with a size-to-thickness ratio from 1 to 50 and size polydispersity as low as 0.2 can be obtained through hydrothermal treatment in 3 M to 15 M phosphoric acid solutions. Transmission and scanning electron micrographs revealed that the growth of the disks is mediated by oriented attachment, which happened continuously throughout the hydrothermal treatment between various sized disks. Ostwald ripening is effective in improving the regularity of the shape of the disks, especially under prolonged hydrothermal treatment. Preferred attachment among the flat surfaces of the disks leads to the diverse developments of their size and thickness polydispersities.

Synergistic antibacterial zinc ions and cerium ions loaded α-zirconium phosphate

In order to improve the antibacterial activity of Zn 2+, a series of Zn 2+ or/and Ce 3+ modified layered α-zirconium phosphate (ZrP) was prepared and characterized, and the antibacterial activity of the prepared Zn 2+ or/and Ce 3+ modified ZrP on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was investigated. The results show that the Zn 2+ or/and Ce 3+ is combined with ZrP, and the d 002 basal spacing of Ce 3+ modified ZrP is not obviously changed, while the d 002 basal spacing of Zn 2+ modified ZrP is increased. Zn 2+ and Ce 3+ modified ZrP displays excellent synergistic antibacterial activity, suggesting great potential application as antibacterial agents in microbial control.

Improved Gel Electrolyte by Layered α-Zirconium Phosphate for Quasi-Solid-State Dye-Sensitized Solar Cells

In this article, we present a new composite gel electrolyte for dye-sensitized solar cells (DSSC), with butylamine (BA) and propylene carbonate (PC) intercalated α-Zirconium phosphate (ZrP-BA-PC) as solid fillers dispersed in polyethlene oxide (PEO) polymer. The ionic electrical conductivity was markedly improved with the ZrP-BA-PC additive at ambient temperature. The DSSC with 5 wt% ZrP addition into the electrolyte obtained the maximum photovoltaic conversion efficiency of 6.61 % under 100 mW/cm-2irradiation.