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In this work, multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy is used to investigate a range of inorganic materials, often in combination with DFT (density functional theory) studies. Solid-state NMR is particularly suited to the study of aluminophosphates (AlPOs), as the basic components of their frameworks have NMR active isotopes (²⁷Al, ³¹P, ¹⁷O), as do many of the atoms that comprise the structure directing agent (¹³C, ¹H, ¹⁵N), and the charge-balancing anions (OH⁻, F⁻). A study of the AlPO STA-15 (St Andrews microporous solid-15) provides an introduction to using solid-state NMR spectroscopy to investigate AlPOs. More in-depth studies of AlPO STA-2 (St Andrews microporous solid-2) and MgAPO STA-2 (magnesium-substituted AlPO) examine charge-balancing mechanisms in AlPO-based materials. A range of scandium carboxylate metal-organic frameworks (MOFs), with rigid and flexible frameworks, have been characterised by multinuclear solid-state NMR spectroscopy (⁴⁵Sc, ¹³C and ¹H). The materials studied contain a variety of metal units and organic linkers. ¹³C and ¹H magic-angle spinning (MAS) NMR were used to study the organic linker molecules and ⁴⁵Sc MAS NMR was used to study the scandium environment in the MOFs Sc₂BDC₃ (BDC = 1,4-benzenedicarboxylate), MIL-53(Sc), MIL-88(Sc), MIL-100(Sc) and Sc-ABTC (ABTC = 3,3`,5,5`-azobenzenetetracarboxylate). Functionalised derivatives of Sc₂BDC₃ and MIL-53(Sc) were also studied. The ⁴⁵Sc MAS NMR spectra are found to be strongly dependant on the Sc³⁺ coordination environment. ²⁷Al and ²⁵Mg MAS NMR have been used to study Ti-bearing hibonite samples (of general formula Ca(Al, Ti, Mg)₁₂O₁₉), and results compared to a recent complementary neutron powder diffraction study, in order to investigate the substitution sites for Ti³⁺/⁴⁺ and Mg²⁺. A DFT investigation was also carried out on the aluminium end member, CaAl₁₂O₁₉, due to debate in the literature on the ²⁷Al NMR parameters for the trigonal-bipyramidal site. The substitution of Mg onto the tetrahedral site (M3) and Ti primarily onto one of the octahedral sites (M4) is supported.

Rare earth ion doped glasses find applications in optical and photonic devices such as optical windows, laser, and optical amplifiers, and as model systems for immobilization of nuclear waste. Macroscopic properties of these materials, such as luminescence efficiency and phase stability, depend strongly on the atomic structure of these glasses. In this thesis, I have studied the atomic level structure of rare earth doped silicate and aluminophosphate glasses by using molecular dynamics simulations. Extensive comparisons with experimental diffraction and NMR data were made to validate the structure models. Insights on the local environments of rare earth ions and their clustering behaviors and their dependence on glass compositions have been obtained. In this thesis, MD simulations have been used to investigate the structure of Eu2O3-doped silica and sodium silicate glasses to understand the glass composition effect on the rare earth ions local environment and their clustering behaviors in the glass matrix, for compositions with low rare earth oxide concentration (~1mol%). It was found that Eu–O distances and coordination numbers were different in silica (2.19-2.22 Å and 4.6-4.8) from those in sodium silicate (2.32 Å and 5.8). High tendencies of Eu clustering and short Eu-Eu distances in the range 3.40-3.90 Å were observed in pure silica glasses as compared to those of silicate glasses with much better dispersed Eu3+ ions and lower probability to form clusters. The results show Eu3+ clustering behavior dependence on the system size and suggest for low doping levels, over 12,000 atoms to obtain statistical meaningful results on the local environment and clustering for rigid silica-based glasses. The structures of four cerium aluminophosphate glasses have also been studied using MD simulations for systems of about 13,000 atoms to investigate aluminum and cerium ion environment and their distribution. P5+ and Al3+ local structures were found stable while those of Ce3+ and Ce4+ ions, through their coordination numbers and bond lengths, are glass composition-dependence. Cerium clusters were found in the high cerium glasses.P5+ coordination numbers around cerium revealed the preference of phosphorus ions in the second coordination shell. Total structure factors from MD simulations and experimental diffraction results show a general agreement from comparison for all the cerium aluminophosphate glasses and with compositional changes up to 25 Å-1. Aluminum enters the phosphate glass network mainly as AlO4 and AlO5 polyhedra only connected through corner sharing to PO4 tetrahedra identified by Q11(1 AlOx), Q12(2 AlOx), Q21(1 AlOx), and Q22(2 AlOx) species.

Doctor of Philosophy / Department of Chemical Engineering / Jennifer L. Anthony / Zeolites and zeolite-like materials are a group of porous materials with many applications in industry including but not limited to detergent builders and catalyst in the oil refining and petrochemical industry, due to their unique properties such as uniform pore size, large surface area and ion-exchange capacity. Researchers are constantly seeking new methods to synthesize zeolites. Zeolites are commonly synthesized in water. Then in 2004, a new method called ionothermal synthesis was invented by Dr. Morris and his colleagues, using ionic liquids (ILs) and eutectic mixtures as the solvent. In contrast to water, ILs and eutectic mixtures have negligible vapor pressure, thus making the use of high-pressure vessel unnecessary. In addition, they have various structures which could render new structures to frameworks of zeolite. Furthermore, since the cations of some ILs have structures which are similar to common structure directing agents, they theoretically could be used both as solvent and structure directing agent in ionothermal synthesis, possibly simplifying the synthesis process. This project is aimed at investigating the behavior of precursors of zeolites in ionic liquids and the interaction between precursors and ionic liquids in ionothermal synthesis because these fundamental properties could be useful in the current and future synthesis of zeolites. First, solubilities of different precursors, including Syloid 63 silica particles, aluminium isopropoxide (Al(OiPr)3) and phosphoric acid (H3PO4) in ILs with different structures are reported. Parameters such as activity coefficient and Henry’s constant are calculated from the solubility result. Second, interaction between precursors and ILs are studied. It is found that the addition of ILs in Al(OiPr)3 could change the structure of Al(OiPr)3, especially with the presence of H3PO4. Both ILs’ structures and temperature are capable of influencing the structure change of Al(OiPr)3. Third, hydrochloric acid is used for the first time as the mineralizer to synthesize aluminophosphates in ILs and it could lead to both dense and porous materials. Regardless of the acid used, frameworks synthesized after several hours always undergo a dramatic change after further heating. A slightly longer alkyl chain of ILs could accelerate the formation of crystalline materials. Increasing concentration of precursors in the reaction gel could increase the yield, but the same framework is not retained. Researches have also been done on stability of ILs in the synthesis process and it is found that heat and the presence of H3PO4 could decompose ILs, but the decomposed amount is extremely small.

A long standing problem in catalysis is the identification and characterization of the active sites, i.e. an atom or an ensemble of atoms spouse on the surface of a catalyst.[Taylor1925] One relevant case, that is treated in this thesis, is constituted by the Phillips catalyst.[Hogan1958] For several reasons, even though this catalyst has be applied at industrial scale for decades and is accounted for a majority of the high density polyethylene (HDPE) production, the identification and the mechanism of the active sites are still under debate. This work was initiated in the framework of the PARACAT project, which is dedicated to study the paramagnetic species in catalysis, and focuses on 'The role of Cr paramagnetic states in olefin polymerization over Phillips catalyst.' In the course of the study, I brought this research to a larger scale which included but was not limited to the Phillips catalyst itself. Considering the relevance of the interaction between transition metal ions (TMI) and the support to the catalytic activity, I worked on systems that cover a number of oxide-supported TMIs by means of electron paramagnetic resonance (EPR) spectroscopy. In this thesis I investigated the paramagnetic Cr(V) and Cr(III) species in the Phillips catalyst. The Cr(III) species were suggested with possible relevance to the catalytic reaction while Cr(V) species were suggested as just the spectators in the reaction.[McDaniel2010, Groppo2018] Nevertheless, Cr(V) species were used in this work as spin probes to provide more information on the overall system. Field-sweep methods including continuous wave (CW) EPR and echo detected field sweep (EDFS) showed that the there are two Cr(V) species with different local geometries. Quantitative analysis of the CW EPR showed that these two Cr(V) species have different reactivity with ethylene. The instantaneous diffusion analysis were performed on the Cr(V) species to provide information on the dispersion of the Cr on the silica surface and the results suggested clusters were formed locally. Besides studying the Phillips catalyst itself, I studied also the silica supported organometallic-Cr catalyst, Cr[CH(SiMe3)2]3/SiO2, which served as a model system to investigate the catalytic active Cr species with well-defined oxidation states and geometry. Two categories of the Cr(III) species were assigned to the active sites for olefin oligomerization and polymerization. The assignment were done by comparing their distortion of the local geometries with that of the different precursors. On the other hand, microporous materials including zeolites and zeotype materials such as aluminophosphate (AlPO) can be engineered with different physical and chemical properties in terms of chemical composition and provide a relevant example of structure sensitivity of a heterogeneous catalyst.[Hartmann2002, Hartmann1999] Such structure sensitivity is highly relevant in catalysis and can be very well studies with EPR spectroscopy. In this regard, I investigated a series of SAPO-5 materials doped with different TMI. In the first place, the incorporation of Cr in SAPO-5 was studied focuses on the discrimination of isomorphous substitution at framework sites and extra-framework sites. In the hyperfine sublevel correlation (HYSCORE) spectrum, large hyperfine interaction (hfi) of 27Al with the matrix 31P signal provide solid evidence for the isomorphous substitution of Cr(V) at framework sites. In addition to the Cr-incorporated SAPO-5, a method to prepare a bi-metallic Mo/V-SAPO-5 system was developed and the metal-metal synergy was validated with a single electron transfer reaction and the short range hyperfine interaction. HYSOCRE spectra showed large \textit{hfi} of both 27Al and 31P and suggested the V species grafted at extra-framework sites. Moreover, the HYSCORE spectrum showed signals at low frequency region which were attributed to the 95,97Mo species with large hfi, confirming the short range interaction. Finally, the surface properties of SAPO-5 were studied by adsorbing NO radicals in the pores and investigating their interaction with the surface. Different adsorption sites of NO molecules according to different activation conditions were first discriminated by the g-factors obtained from the CW EPR. From the 27Al HYSCORE spectra, it is observed that when the activation temperature is higher the NO molecules are situated in vicinity of some defect Al sites. However, the dominant Al species were observed either in samples activated at lower temperature or by increasing the NO dosage. This is postulated as that the defect sites were blocked by residual water molecules or saturated by excessive NO molecules. The presence of water molecules were validated by 1H HYSCORE experiments and the coordination of NO-water was estimated from the hfi structure. [Taylor1925] Taylor, H. S. Proc. R. Soc. London. Ser. A, Contain. Pap. a Math. Phys. Character 1925, 108, 105-111 [Hogan1958] Hogan, J. P.; Banks, R. L. Polymers and production thereof US Patent 2,825,721, 1958. [McDaniel2010] McDaniel M. P. Advances in Catalysis, 1st Ed. 2010; Vol. 52, pp 123-606 [Groppo2018] Groppo, E.; Martino, G. A.; Piovano, A.; Barzan, C. ACS Catal. 2018, 8, 10846-10863 [Hartmann2002] Hartmann, M.; Kevan, L. Res. Chem. Intermed. 2002, 28, 625-695 [Hartmann1999] Hartmann, M.; Kevan, L. Chem. Rev. 1999, 99, 635-663

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-04-04T13:23:13Z No. of bitstreams: 1 AleffCruzdeCastro.pdf: 1452660 bytes, checksum: 8c8c4baa89c5a3373105fcb0cd29e65c (MD5) / Made available in DSpace on 2017-04-04T13:23:13Z (GMT). No. of bitstreams: 1 AleffCruzdeCastro.pdf: 1452660 bytes, checksum: 8c8c4baa89c5a3373105fcb0cd29e65c (MD5) Previous issue date: 2017-03-06 / CNPq, FAPEMA, CAPES, FSADU / Zeolites are microporous inorganic materials with a variety of applications in several areas of science and engineering. Their physical and chemical properties are attributed to the large internal surface area, and the chemical and hydrothermal stability, which are induced by the existence of well defined channels and/or cavities. These structural characteristics promote the use of zeolites as catalysts, molecular sieves, ion exchangers and, more recently, as electrochemical sensors. Taking in consideration these premises, this work describes the development of an electrochemical sensor obtained from the modification of the polyurethane graphite composite electrode with NiAlPO-5, a nickel-modified AFI aluminophosphate, and its application for determination of Cu2+ in ethanol biofuel. The synthesis of the aluminophosphates were conducted by the hydrothermal method and the obtained materials were characterized by X-ray diffraction, scanning electron microscopy, 31P nuclear magnetic resonance and UV-Vis and infrared spectroscopy. After synthesis and characterization, materials were used as modifiers (10%) in GPU electrodes in order to compare the performance of the unmodified and modified electrodes by Square Wave Anodic Stripping Voltammetry. The results showed that the incorporation of Ni to the material structure promotes an improvement in the electrical properties and analytical properties of the electrode. The analytical response of the sensor in the copper ion determination showed that the NiAlPO-5 electrode is more sensitive in terms of peak current than the electrolyte based on AlPO-5 only. The best response was obtained with the Ni/Al ratio of 0.5 on the NiAlPO-5 sensor. The experimental conditions of potential and deposition time, pulse amplitude, step potential, frequency and pH were optimized in an electrochemical cell containing 2 mL of ethanol, 8 mL of HCl 0.1 mol L-1 and Cu2+ concentration of 2.5×10-7 mol L-1. GPU/NiAlPO-5 modified sensor was then evaluated for electroanalytical determination of Cu2+ in ethanol biofuel samples presenting a linear response for Cu2+. Good results were obtained for the limit of detection (9.44×10-9 mol L-1), accuracy (recovery of 115%) and precision (RSD of 5.92%). / As zeólitas são materiais inorgânicos microporosos que apresentam uma grande variedade de aplicações em diversas áreas das ciências e engenharias. Suas propriedades físicas e químicas são atribuídas à grande área superficial interna e à estabilidade química e hidrotérmica, as quais são induzidas pela existência de canais e/ou cavidades bem definidos, tornando possível a sua utilização como catalisadores, peneiras moleculares, trocadores iônicos e, mais recentemente, como sensores eletroquímicos. Com base nisto, este trabalho apresenta o desenvolvimento de um sensor eletroquímico obtido a partir da modificação do eletrodo compósito de grafite poliuretana com NiAlPO-5, um aluminofosfato de estrutura AFI modificado com níquel, e sua aplicação na determinação de Cu2+ em amostras de etanol combustível. Os aluminofosfatos foram sintetizados através do método hidrotérmico e caracterizados por difração de raios-X, microscopia eletrônica de varredura, ressonância magnética nuclear de 31P e espectroscopia de UV-Vis e de infravermelho. Os materiais obtidos foram, então, utilizados como modificadores na proporção de 10% em eletrodos GPU, a fim de realizar-se uma comparação entre os eletrodos sem modificação e modificados com AlPO-5 e NiAlPO-5 mediante a utilização da técnica de voltametria de redissolução anódica com varredura de onda quadrada e o método de adição padrão. Os resultados mostraram que a incorporação do Ni à estrutura do material promove uma melhora nas propriedades elétricas e analíticas do eletrodo. A resposta analítica do sensor na determinação do íon Cu2+, mostrou que o eletrodo NiAlPO-5 é mais sensível, em termos de corrente de pico, que o eletrodo baseado apenas em AlPO-5. A melhor resposta foi obtida com a razão Ni/Al de 0,5 no sensor NiAlPO-5. As condições experimentais, potencial e tempo de deposição, amplitude de pulso, potencial de escada, frequência e pH foram otimizadas em uma célula eletroquímica contendo 2 mL de etanol, 8 mL de HCl 0,1 mol L-1 e uma concentração de Cu2+ de 2,5×10-7 mol L-1. O sensor modificado com NiAlPO-5 foi então avaliado para determinação eletroanalítica de Cu2+ em amostras de etanol combustível apresentando resposta linear para Cu2+. Bons resultados foram obtidos para o limite de detecção (9,44×10-9 mol L-1), limite de quantificação (3,15 x10-8 mol L-1), recuperação (115%) e precisão (5,92%).

Porous zeolite, carbon and aluminophosphate powders have been colloidally assembled and post-processed in the form of monoliths, flexible free standing films and coatings for gas separation and odor removal. Zeolite 13X monoliths with macroporosites up to 50 vol% and a high CO2 uptake were prepared by colloidal processing and sacrificial templating. The durability of silicalite-I supports produced in a binder-free form by pulsed current processing (PCP) were compared with silicalite-I supports produced using clay-binders and conventional thermal treatment. Long-term acid and alkali treatment of the silicalite-I substrates resulted in removal of the clay binder and broadened the size-distribution of the interparticle macropores. Furthermore, strong discs of hydrothermally treated beer waste (HTC-BW) were produced by PCP and the discs were activated by physical activation in CO2 at high temperatures. The activated carbon discs showed high strength up to 7.2 MPa while containing large volume of porosities at all length scales. PCP was further used to structure aluminomphosphate powders (AlPO4-17 and AlPO4-53) into strong functional monoliths. The aluminophosphate monoliths had strengths of 1 MPa, high CO2 uptake and were easy to regenerate. Zeolite Y, silicalite and ZSM5 were selected as potential zeolite adsorbents for removal of sulfur containing compound, e.g. ethyl mercaptan (EM) and propyl mercaptan (PM). A novel processing procedure was used to fabricate free-standing films and coatings of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite; 89 w/w% and 96 w/w%, respectively. Thin flexible free-standing films and coatings of zeolite-CNF on paperboards with thickness around 100 µm and 40 µm, respectively, were produced. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC/MS) analysis showed that the zeolite-CNF films can efficiently remove considerable amount of odors below concentration levels that can be sensed by the human olfactory system. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.</p>

This thesis combines solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), chemical synthesis, isotopic enrichment and density-functional theory (DFT) calculations to provide insight into a number of microporous materials. The first class of materials studied is metal-organic frameworks (MOFs), where the presence of paramagnetic ions has a range of effects on the ¹³C NMR spectra, depending on the nature of the ligand-metal interactions. For the Cu²⁺-based MOFs, HKUST-1 and STAM-1, the assignment of the NMR spectra is non-intuitive, and unambiguous assignment requires specific ¹³C labelling of the organic linker species. It is shown that ¹³C NMR spectra of these two MOFs could act as a sensitive probe of the nature of “guest” molecules bound to the Cu²⁺. The second class of materials is aluminophosphates (AlPOs). It is shown that, using a series of relatively simple linear relationships with the crystal structure, the NMR parameters calculated by DFT (with calculation times of several hours) can be predicted, often with experimentally-useful accuracy, in a matter of seconds using the DIStortion analysis COde (DISCO), which is introduced here. The ambient hydration of the AlPO, JDF-2, to AlPO-53(A) is shown to occur slowly, with incomplete hydration after ~3 months. The resulting AlPO-53(A) is disordered and some possible models for this disorder are investigated by DFT. The final class of materials is gallophosphates (GaPOs), particularly GaPO-34 and related materials. The two as-prepared forms of GaPO-34 are characterised by solid-state NMR, and their calcination investigated by TGA and in-situ powder XRD. An unusual dehydrofluorinated intermediate phase is isolated and characterised for the first time by solid-state NMR. The fully calcined material is shown to be stable under anhydrous conditions, but hydrates rapidly in air. The hydrated material is stable under ambient conditions, but collapses upon heating. Partial dehydration without collapse is achieved by gentle heating or room-temperature evacuation. The impurity phases, GaPO₄ berlinite and GaPO-X are investigated by solid-state NMR and, while the structure of GaPO-X remains unknown, much structural information is obtained.

Made available in DSpace on 2014-12-17T15:01:52Z (GMT). No. of bitstreams: 1 KalyaneKPG_TESE.pdf: 3118375 bytes, checksum: 2236ef256239dd7e294613c3eed787d5 (MD5) Previous issue date: 2011-10-27 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Discussions about pollution caused by vehicles emission are old and have been developed along the years. The search for cleaner technologies and frequent weather alterations have been inducing industries and government organizations to impose limits much more rigorous to the contaminant content in fuels, which have an direct impact in atmospheric emissions. Nowadays, the quality of fuels, in relation to the sulfur content, is carried out through the process of hydrodesulfurization. Adsorption processes also represent an interesting alternative route to the removal of sulfur content. Both processes are simpler and operate to atmospheric temperatures and pressures. This work studies the synthesis and characterization of aluminophosphate impregnate with zinc, molybdenum or both, and its application in the sulfur removal from the gasoline through the adsorption process, using a pattern gasoline containing isooctane and thiophene. The adsorbents were characterized by x-ray diffraction, differential thermal analysis (DTG), x-ray fluorescence and scanning electron microscopy (SEM). The specific area, volume and pore diameter were determined by BET (Brunauer- Emmet-Teller) and the t-plot method. The sulfur was quantified by elementary analysis using ANTEK 9000 NS. The adsorption process was evaluated as function of the temperature variation and initial sulfur content through the adsorption isotherm and its thermodynamic parameters. The parameters of entropy (&#916;S), enthalpy variation (&#916;H) and free Gibbs energy (&#916;G) were calculated through the graph ln(Kd) versus 1/T. Langmuir, Freundlich and Langmuir-Freundlich models were adjusted to the experimental data, and the last one had presented better results. The thermodynamic tests were accomplished in different temperatures, such as 30, 40 and 50?C, where it was concluded the adsorption process is spontaneous and exothermic. The kinetic of adsorption was studied by 24 h and it showed that the capability adsorption to the adsorbents studied respect the following order: MoZnPO > MoPO > ZnPO > AlPO. The maximum adsorption capacity was 4.91 mg/g for MoZnPO with an adsorption efficiency of 49%. / As discuss?es sobre o problema da polui??o causada por emiss?es veiculares s?o antigas e v?m evoluindo com o passar do tempo. A procura por tecnologias mais limpas e as altera??es clim?ticas cada vez mais frequentes induziram as ind?strias e os ?rg?os governamentais a impor limites cada vez mais rigorosos para os teores de contaminantes nos combust?veis, os quais impactam diretamente nas emiss?es atmosf?ricas. Atualmente a forma de melhorar a qualidade dos combust?veis, quanto ao enxofre, ? atrav?s do processo de hidrodessulfuriza??o e recentemente, os processos de adsor??o tem se mostrado como uma alternativa bastante interessante ? remo??o de enxofre, pois tais processos s?o mais simples e operam a temperaturas e press?es atmosf?ricas. O presente trabalho contempla a s?ntese e caracteriza??o do aluminofosfato impregnado com zinco, molibd?nio ou ambos e sua aplica??o no estudo da remo??o de enxofre da gasolina atrav?s do processo de adsor??o, utilizando uma gasolina modelo contendo iso-octano e tiofeno. Os adsorventes foram caracterizados por difra??o de raios-X, an?lise termogravim?trica (ATG), fluoresc?ncia de raios-X e microscopia eletr?nica de varredura (MEV). A ?rea espec?fica, volume e di?metro de poros foram determinados pelo m?todo BET (Brunauer-Emmet-Teller) e m?todo t-plot. O enxofre foi quantificado por analise elementar atrav?s do ANTEK 9000 NS. O Processo de adsor??o foi avaliado em fun??o da varia??o da temperatura e da concentra??o inicial de enxofre atrav?s das isotermas de adsor??o e de seus par?metros termodin?micos. Os par?metros varia??o de entropia (&#916;S), varia??o de entalpia (&#916;H) e varia??o da energia livre de Gibbs (&#916;G) foram calculados pelo gr?fico de ln(K) versus 1/T. Os modelos de Langmuir, Freundlich e Langmuir-Freundlich foram ajustados aos dados experimentais, tendo o ?ltimo apresentado os melhores resultados. Os testes termodin?micos foram realizados nas temperaturas de 30, 40, 50 ?C e constatou-se que o processo de adsor??o ? espont?neo e exot?rmico. A cin?tica da adsor??o foi estudada por 24 horas e mostrou que a capacidade de adsor??o para os adsorventes estudados segue a seguinte ordem: MoZnPO > MoPO > ZnPO > AlPO. A capacidade m?xima de adsor??o foi 4,91 mg/g para o MoZnPO com uma efici?ncia de adsor??o de 49%.