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1.
Nanomaterials (Basel) ; 10(5)2020 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-32357400

RESUMO

Zirconium phosphate (ZrP) nanomaterials have been studied extensively ever since the preparation of the first crystalline form was reported in 1964. ZrP and its derivatives, because of their versatility, have found applications in several fields. Herein, we provide an overview of some advancements made in the preparation of ZrP nanomaterials, including exfoliation and morphology control of the nanoparticles. We also provide an overview of the advancements made with ZrP as an inorganic support for the electrocatalysis of the oxygen evolution reaction (OER). Emphasis is made on how the preparation of the ZrP electrocatalysts affects the activity of the OER.

2.
Dalton Trans ; 49(13): 3914-3916, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-32154526
3.
Dalton Trans ; 49(12): 3892-3900, 2020 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-31894216

RESUMO

The electrochemical oxygen evolution reaction (OER) is the half-cell reaction for many clean-energy production technologies, including water electrolyzers and metal-air batteries. However, its sluggish kinetics hinders the performance of those technologies, impeding them from broader implementation. Recently, we reported the use of zirconium phosphate (ZrP) as a support for transition metal catalysts for the oxygen evolution reaction (OER). These catalysts achieve promising overpotentials with high mass activities. Herein, we synthesize ZrP structures with controlled morphology: hexagonal platelets, rods, cubes, and spheres, and subsequently modify them with Co(ii) and Ni(ii) cations to assess their electrochemcial OER behavior. Through inductively coupled plasma mass-spectrometry measurements, the maximum ion exchange capacity is found to vary based on the morphology of the ZrP structure and cation selection. Trends in geometric current density and mass activity as a function of cation selection are discussed. We find that the loading and coverage of cobalt and nickel species on the ZrP supports are key factors that control OER performance.

4.
Science ; 362(6410): 7, 2018 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-30287637
7.
Magn Reson Chem ; 55(7): 648-654, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27966256

RESUMO

Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy-polyethyleneglycol-monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid-state MAS NMR techniques. The organic components of the phosphates have been characterized by the 13 C{1 H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton-phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd.


Assuntos
Zircônio/química , Doxorrubicina/química , Espectroscopia de Ressonância Magnética , Polietilenoglicóis/química , Propriedades de Superfície
8.
J Nanosci Nanotechnol ; 16(1): 117-29, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27398437

RESUMO

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.


Assuntos
Apoptose/efeitos dos fármacos , Doxorrubicina , Portadores de Fármacos , Nanopartículas/química , Neoplasias/tratamento farmacológico , Zircônio , Doxorrubicina/química , Doxorrubicina/farmacologia , Portadores de Fármacos/química , Portadores de Fármacos/farmacologia , Feminino , Humanos , Células MCF-7 , Neoplasias/metabolismo , Neoplasias/patologia , Zircônio/química , Zircônio/farmacologia
9.
Nanoscale ; 5(23): 11456-63, 2013 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-24072038

RESUMO

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.


Assuntos
Antineoplásicos/química , Antineoplásicos/farmacologia , Cisplatino/química , Cisplatino/farmacologia , Substâncias Intercalantes/química , Nanopartículas Metálicas/química , Zircônio/química , Antineoplásicos/administração & dosagem , Neoplasias da Mama/tratamento farmacológico , Sobrevivência Celular/efeitos dos fármacos , Cisplatino/administração & dosagem , Portadores de Fármacos/química , Feminino , Humanos , Concentração de Íons de Hidrogênio , Substâncias Intercalantes/farmacologia , Células MCF-7
10.
Inorg Chem ; 51(5): 2777-84, 2012 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-22339702

RESUMO

The direct intercalation of a pyrazolate-bridged platinum(II) bipyridyl dimer ([{Pt(dmbpy)(µ-pz)}(2)](2+); dmbpy = 4,4'-dimethyl-2,2'-bipyridine, pz(-) = pyrazolate) within a zirconium phosphate (ZrP) framework has been accomplished. The physical and spectroscopic properties of [{Pt(dmbpy)(µ-pz)}(2)](2+) intercalated in ZrP were investigated by X-ray powder diffraction and X-ray photoelectron, infrared, absorption, and luminescence spectroscopies. Zirconium phosphate layers have a special microenvironment that is capable of supporting a variety of platinum oxidation states. Diffuse reflectance spectra from powders of the blue-gray intercalated materials show the formation of a low-energy band at 600 nm that is not present in the platinum dimer salt. The nonintercalated complex is nonemissive in room-temperature fluid solution, but gives rise to intense blue-green emission in a 4:1 ethanol/methanol 77 K frozen glassy solution. Powders and colloidal suspensions of [{Pt(dmbpy)(µ-pz)}(2)](2+)-exchanged ZrP materials exhibit intense emissions at room-temperature.

11.
Langmuir ; 28(9): 4447-52, 2012 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-22316317

RESUMO

The direct intercalation reaction of [Co(tpy)(2)](2+) with the highly hydrated θ phase of layered zirconium phosphate (θ-ZrP) resulted in the formation of the oxidized [Co(tpy)(2)](3+) ion within the ZrP material. The X-ray powder diffraction patterns showed that the interlayer distance increases from 10.3 Å in θ-ZrP to 14.9 Å in the dry [Co(tpy)(2)](3+)-intercalated ZrP {[Co(tpy)(2)](3+):ZrP} phase. The complex remains electroactive within the layers of ZrP. The formal potential of a carbon paste electrode (CPE) modified with [Co(tpy)(2)](3+):ZrP (E°' = 40.8 mV versus Ag/AgCl, 3.5 M NaCl) is non-pH-dependent. However, the sensitivity of the [Co(tpy)(2)](3+):ZrP-modified CPE for the detection of reduced nicotinamide adenine dinucleotide (NADH) electrooxidation was lower than that of a previously reported CPE modified with [Ru(phend)(2)bpy](2+)-intercalated ZrP. (1) To improve the characteristics of NADH electrooxidation of the [Co(tpy)(2)](3+):ZrP-modified CPE, we included the enzyme diaphorase in solution, which increased the electrocatalytic current for NADH oxidation. A bienzymatic lactate biosensor was constructed and used for lactate sensing.


Assuntos
Técnicas Biossensoriais/métodos , Cobalto/química , Zircônio/química , Catálise , NAD/química , Difração de Raios X
12.
Chem Commun (Camb) ; 48(12): 1754-6, 2012 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-22218458

RESUMO

Doxorubicin was intercalated into novel zirconium phosphate nano-platelets (ZrP). The obtained doxorubicin intercalated ZrP nano-platelets had an impressive 34.9% (w/w) drug loading. We used this material to deliver doxorubicin to breast cancer cells (MCF-7). Cellular studies with MCF-7 cells showed higher uptake and cytotoxicity of doxorubicin loaded ZrP compared to free doxorubicin.


Assuntos
Antibióticos Antineoplásicos/administração & dosagem , Doxorrubicina/administração & dosagem , Portadores de Fármacos/química , Nanoestruturas/química , Zircônio/química , Antibióticos Antineoplásicos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Doxorrubicina/farmacologia , Feminino , Humanos , Nanoestruturas/ultraestrutura
13.
Inorg Chem ; 49(16): 7298-303, 2010 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-20690739

RESUMO

We studied the structures, luminescence, and self-quenching properties of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) two-dimensional arrangements within the layers of zirconium phosphate (ZrP). The intercalation of Ru(bpy)(3)(2+) was accomplished using a hydrated form of zirconium phosphate ZrP. Varying the Ru(bpy)(3)(2+)/ZrP intercalation ratio, different Ru(bpy)(3)(2+)-exchanged ZrP loading levels were achieved. The ion exchange of Ru(bpy)(3)(2+) within ZrP produces a red shift in the metal-to-ligand charge-transfer (MLCT) absorption band of the complex from 452 nm in aqueous solution to 460 nm in ZrP. Steady state luminescence spectra of the Ru(bpy)(3)(2+)-exchanged ZrP materials show an increase in the luminescence intensity with an increase in the Ru(bpy)(3)(2+) loading level until about 0.77 M, where subsequent increases in the loading level produce a decrease in the luminescence (self-quenching region). Time-resolved luminescence measurements are consistent with the steady state luminescence measurements. Analysis of the time domain luminescence measurements in loadings higher than 0.77 M leads to the determination of a collisional quenching rate constant of (1.67 +/- 0.05) x 10(6) M(-1) s(-1). Stern-Volmer analysis of the luminescence quantum yield of Ru(bpy)(3)(2+)-exchanged ZrP materials indicates that static quenching is also involved in the Ru(bpy)(3)(2+) self-quenching mechanism. The quantum yield data behavior might be explained by a model that takes into account collisional quenching and the quasi-static Perrin mechanism. The calculation yields a quenching sphere of action of 14.8 A, which is slightly larger than the collisional radii of two Ru(bpy)(3)(2+) ions (12.2 A), as predicted by the model.


Assuntos
Compostos Organometálicos/química , Zircônio/química , Medições Luminescentes , Teoria Quântica , Análise Espectral
14.
Biomacromolecules ; 11(9): 2465-70, 2010 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-20707305

RESUMO

The encapsulation of insulin into different kinds of materials for noninvasive delivery is an important field of study because of the many drawbacks of painful needle and syringe delivery such as physiological stress, infection, and local hypertrophy, among others (Khafagy, E.-S.; et al. Adv. Drug Delivery Rev. 2007, 59 (15), 1521-1546). A stable, robust, nontoxic, and viable noninvasive carrier for insulin delivery is needed. We present a new approach for protein nanoencapsulation using layered zirconium phosphate (ZrP) nanoparticles produced without any preintercalator present. The use of ZrP without preintercalators produces a highly pure material, without any kinds of contaminants, such as the preintercalator, which can be noxious. Cytotoxicity cell viability in vitro experiments for the ZrP nanoparticles show that ZrP is not toxic, or harmful, in a biological environment, as previously reported for rats (Zhu, Z. Y.; et al. Mater. Sci. Forum 2009, 620-622, 307-310). Contrary to previous preintercalator-based methods, we show that insulin can be nanoencapsulated in ZrP if a highly hydrate phase of ZrP with an interlayer distance of 10.3 Å (10.3 Å-ZrP or θ-ZrP) is used as a precursor. The intercalation of insulin into ZrP produced a new insulin-intercalated ZrP phase with about a 27 A interlayer distance, as determined by X-ray powder diffraction, demonstrating a successful nanoencapsulation of the hormone. The in vitro release profile of the hormone after the intercalation was determined and circular dichroism was used to study the hormone stability upon intercalation and release. The insulin remains stable in the layered material, at room temperature, for a considerable amount of time, improving the shell life of the peptidic hormone. This type of material represents a strong candidate to developing a noninvasive insulin carrier for the treatment of diabetes mellitus.


Assuntos
Hipoglicemiantes/química , Insulina/química , Substâncias Intercalantes/química , Nanocápsulas/química , Nanotecnologia/métodos , Zircônio/química , Animais , Neoplasias da Mama/tratamento farmacológico , Bovinos , Sobrevivência Celular/efeitos dos fármacos , Dicroísmo Circular , Feminino , Humanos , Hipoglicemiantes/farmacologia , Insulina/farmacologia , Microscopia Eletrônica de Varredura , Pâncreas/metabolismo , Ratos , Espectroscopia de Infravermelho com Transformada de Fourier , Células Tumorais Cultivadas
15.
Biochemistry ; 48(22): 5018-25, 2009 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-19368336

RESUMO

Nitrosyl hydride, HNO or nitroxyl, is the one-electron reduced and protonated form of nitric oxide. HNO is isoelectronic to singlet O(2), and we have previously reported that deoxymyoglobin traps free HNO to form a stable adduct. In this report, we demonstrate that oxygen-binding hemoglobins from human, soy, and clam also trap HNO to form adducts which are stable over a period of weeks. The same species can be formed in higher yields by careful reduction of the ferrous nitrosyl adducts of the proteins. Like the analogous O(2)-Fe(II) adducts, the HNO adducts are diamagnetic, but with a characteristic HNO resonance in (1)H NMR at ca. 15 ppm that splits into doublets for H(15)NO adducts. The (1)H and (15)N NMR resonances, obtained by HSQC experiments, are shown to differentiate subunits and isoforms of proteins within mixtures. An apparent difference in the reduction rates of the NO adducts of the two subunits of human hemoglobin allows assignment of two distinct nitrosyl hydride peaks by a combination of UV-vis, NMR, and EPR analysis. The two peaks of the HNO-hHb adduct have a persistent 3:1 ratio during trapping reactions, demonstrating a kinetic difference between HNO binding at the two subunits. These results show NMR characterization of ferrous HNO adducts as a unique tool sensitive to structural changes within the oxygen-binding cavity, which may be of use in defining modes of oxygen binding in other heme proteins and enzymes.


Assuntos
Compostos Ferrosos/química , Globinas/química , Oxigênio/química , Animais , Bivalves , Hemeproteínas/química , Hemoglobinas/química , Cavalos , Humanos , Ácidos Hidroxâmicos/química , Mioglobina/química , Compostos Nitrosos/química , Ressonância Magnética Nuclear Biomolecular , Prótons , Sulfonamidas/química
16.
Inorg Chem ; 46(21): 8569-76, 2007 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-17880059

RESUMO

The direct ion exchange of chloro(2,6-bis(N-methylbenzimidazol-2-yl)pyridine)platinum(II) ([Pt(Me(2)bzimpy)Cl]+) and chloro(2,2':6',2' '-terpyridine)platinum(II) ([Pt(tpy)Cl]+) complexes within a zirconium phosphate (ZrP) framework has been accomplished. The physical and spectroscopic properties of [Pt(Me(2)bzimpy)Cl]+ and [Pt(tpy)Cl]+ intercalated in ZrP were investigated by X-ray powder diffraction and X-ray photoelectron, infrared, absorption, and luminescence spectroscopies. In contrast to unintercalated complexes in fluid solution, which do not emit at room temperature, both intercalated materials in the solid state and in colloidal suspensions exhibit intense emissions at room temperature. A [Pt(Me(2)bzimpy)Cl]+-exchanged ZrP colloidal methanol suspension gives rise to an emission at 612 nm that originates from a lowest (3)MMLCT[dsigma*(Pt) --> pi*(tpy)] state (MMLCT = metal-metal-to-ligand charge transfer) characteristic of strong Pt...Pt interactions. A [Pt(tpy)Cl]+-exchanged ZrP colloidal aqueous suspension exhibits a strong emission band at 600 nm. The accumulated data demonstrate that at high concentrations, [Pt(Me(2)bzimpy)Cl]+ and [Pt(tpy)Cl]+ ions can serve as luminescent pillars inside the ZrP framework.


Assuntos
Química/métodos , Compostos de Platina/química , Platina/análise , Platina/química , Zircônio/análise , Íons , Luz , Metanol/química , Modelos Químicos , Conformação Molecular , Estrutura Molecular , Pós , Espectrometria por Raios X/métodos , Espectrofotometria/métodos , Temperatura , Difração de Raios X , Zircônio/química
17.
Langmuir ; 23(14): 7810-7, 2007 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-17547428

RESUMO

The direct intercalation reaction of ferrocene (bis(eta5-cyclopentadienyl)iron(II), Fc) with a highly hydrated layered zirconium phosphate (ZrP) resulted in the formation of the ferrocenium ion (Fc+) within the ZrP material. The Fc+-intercalated ZrP material has an interlayer distance of 10.7 A. The intercalated material was used as an electron acceptor for the oxidation of both ferro-cytochrome c and the excited state of tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+). Upon contact of the material with a 1.5 x 10(-5) M solution of ferro-cytochrome c, the UV-vis absorption spectrum shows the successful formation of ferri-cytochrome c. Luminescence spectroscopy shows that the Fc+-intercalated ZrP material quenches the luminescence of [Ru(bpy)3]2+. The excited-state quenching mechanism of [Ru(bpy)3]2+* by Fc+-intercalated ZrP follows a dynamic plus sphere of action model. The second-order dynamic quenching rate constant kq is 2.2 x 10(8) M(-1) s(-1).


Assuntos
Compostos Ferrosos/química , Substâncias Intercalantes/química , Zircônio/química , 2,2'-Dipiridil/análogos & derivados , 2,2'-Dipiridil/química , Cátions , Complexos de Coordenação , Grupo dos Citocromos c/química , Grupo dos Citocromos c/metabolismo , Transporte de Elétrons , Cinética , Luminescência , Metalocenos , Modelos Químicos , Oxirredução , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta
18.
Dalton Trans ; (17): 1713-8, 2007 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-17443264

RESUMO

The intercalation of fac-tricarbonylchloro-1,10-phenanthrolinerhenium(i) (Re(phen)(CO)(3)Cl) within zirconium phosphate (ZrP) has been achieved using a hydrated ZrP phase that possesses six water molecules per formula unit. This intercalation occurs only at high solution molar ratios (Re : ZrP, 3 : 1) and is characterized by the emergence of a new phase in the X-ray powder diffraction (XRPD) pattern with an interlayer distance of 15.6 A. The XRPD patterns show a decrease in the crystallinity upon intercalation of the inorganic complex. The MLCT absorption bands of Re(phen)(CO)(3)Cl-containing ZrP materials are red shifted in comparison with the complex in acetonitrile whilst the luminescence spectra at different loading levels are blue shifted up to 30 nm in comparison with the complex in acetonitrile. This blue shift is consistent with the rigidochromic effect. The luminescence lifetime of Re(phen)(CO)(3)Cl within ZrP was increased in comparison with its lifetime in acetonitrile solution but is shorter than that of Re(phen)(CO)(3)Cl in frozen glass and polyesther resins. To our knowledge, this is the first example of a water insoluble metal complex intercalated within the layers of ZrP, which opens up new possibilities in the intercalation chemistry of this lamellar material and in the study of host-guest interactions.


Assuntos
Substâncias Intercalantes/química , Rênio/química , Zircônio/química , Solubilidade , Espectrofotometria Ultravioleta , Água/química , Difração de Raios X
19.
Electroanalysis ; 18(6): 559-572, 2006 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-18516242

RESUMO

We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthroline-5,6-dione) (2,2'-bipyridine)ruthenium(II) ([Ru(phend)(2)bpy](2+)) exchanged into the inorganic layered material zirconium phosphate (ZrP). X-Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)(2)bpy](2+) intercalation from 10.3 Å to 14.2 Å. The UV-vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)(2)bpy](2+). The UV-vis spectrophotometric results indicate that the [Ru(phend)(2)bpy](2+) concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)(2)bpy](2+) exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°' = -38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis -Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers' yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.

20.
Langmuir ; 21(3): 890-5, 2005 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-15667164

RESUMO

The ion exchange of the luminescent probe 1-pyrenemethylamine (PYMA) into zirconium phosphate (ZrP) layered materials has been accomplished. The matrices used were the hexahydrated 10.3 A phase of ZrP (10.3 A ZrP, where 10.3 A represents the interlayer distance) and butylammonium-exchanged ZrP (BAZrP) with an expanded 18.6 A interlayer distance. The XRPD patterns for the 10.3 A ZrP after PYMA exchange (PYMA-exchanged ZrP), at high PYMA concentrations, show an increase in the interlayer distance from 10.3 A in unexchanged 10.3 A ZrP to 23.5 A in PYMA-exchanged ZrP, indicating PYMA intercalation. The luminescence spectrum for the PYMA-exchanged ZrP exhibits an excimer band at 458 nm that is absent in the luminescence spectrum of PYMA in aqueous solution at low concentrations. The intensity of the excimer emission increased at low PYMA concentrations. These results are in contrast to experiments using the BAZrP matrix. The XRPD patterns for PYMA-exchanged BAZrP do not show changes in the interlayer distance, which suggests that PYMA is not being intercalated and is only surface bound. The luminescence spectrum for PYMA-exchanged BAZrP exhibits a lower emission intensity in its excimer band, at different PYMA concentrations, compared with the PYMA-exchanged ZrP excimer band. For PYMA-exchanged ZrP, we propose a process in which exchange at low PYMA concentrations occurs at external surface sites with clustering promoting excimer formation followed by exchange at high PYMA concentrations occurring at interior sites reducing excimer formation.

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