Titanium(IV)–EDTA complex

Guinesi, Luciana Simionatto; Ribeiro, Clóvis Augusto; Crespi, Marisa Spirandeli; Santos, Andréa F. S.; Capela, Marisa Veiga

doi:10.1007/s10973-005-7027-7

Cited by 23 publications

(6 citation statements)

References 23 publications

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“…This may be due to the hindering effect of excess EDTA toward anatase phase evolution and its transformation to rutile. An additional exotherm responsible for the decomposition of unreacted EDTA was also observed at 290 °C in complexes containing excess EDTA (1:1.5 and 1:2) . The formation of anatase-rutile heterojunctions were observed only from EDTA modified titania precursor.…”

Section: Resultsmentioning

confidence: 82%

Highly Visible Light Active TiO_2−xN_x Heterojunction Photocatalysts

Seery²,

et al. 2010

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Nitrogen doped anatase-rutile heterojunctions are successfully synthesized through an ethylenediaminetetraacetic acid (EDTA) modified sol−gel process. An FT-IR study of EDTA modified TiO2 gel confirms the existence of an ionic intermediate (as indicated by a Δν value of 233 cm−1). Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman spectroscopy are employed to study the phase evolution, phase purity, and crystallite size of samples. Formations of O−Ti−N and N−Ti−N bonds in calcined samples are confirmed using XPS and FT-IR spectroscopy. All EDTA modified samples show significantly higher visible light photocatalytic activity than the unmodified sample. The most active nitrogen doped heterojunction obtained at 400 °C exhibits 9-fold visible light activity in comparison to the standard photocatalyst Degussa P-25. It is proposed that the photo excited electrons (from the visible midgap level) are effectively transferred from the conduction band of anatase to that of rutile causing effective electron−hole separation, which is responsible for the higher visible light activity and lower photoluminescence (PL) intensity.

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Section: Resultsmentioning

confidence: 82%

Highly Visible Light Active TiO_2−xN_x Heterojunction Photocatalysts

Seery²,

et al. 2010

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“…For the kinetic studies using spontaneously hydrated CBZ and samples of CBZ dried at 120 °C, TG analyses were performed at heating rates of were performed at heating rates of 2.5, 5.0, 10.0, and 15.0 min -1 , under the same conditions described above. Guinesi et al (2006) provided a detailed description of the theory and equations involved in this method. Data analysis was performed using Thermal Specialty Library v.1.4 software (TA Instruments).…”

Section: Methodsmentioning

confidence: 99%

Thermoanalytical studies of carbamazepine: hydration/dehydration, thermal decomposition, and solid phase transitions

Pinto¹,

Ambrozini²,

Ferreira³

et al. 2014

Braz. J. Pharm. Sci.

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Carbamazepine (CBZ), a widely used anticonvulsant drug, can crystallize and exhibits four polymorphic forms and one dihydrate. Anhydrous CBZ can spontaneously absorb water and convert to the hydrate form whose different crystallinity leads to lower biological activity. The present study was concerned to the possibility of recovering the hydrated form by heating. The thermal behavior of spontaneously hydrated carbamazepine was investigated by TG/DTG-DTA and DSC in dynamic atmospheres of air and nitrogen, which revealed that the spontaneous hydration of this pharmaceutical resulted in a Form III hydrate with 1.5 water molecules. After dehydration, this anhydrous Form III converted to Form I, which melted and decomposed in a single event, releasing isocyanic acid, as shown by evolved gas analysis using TG-FTIR. Differential scanning calorimetry analyses revealed that Form III melted and crystallized as Form I, and that subsequent cooling cycles only generated Form I by crystallization. Solid state decomposition kinetic studies showed that there was no change in the substance after the elimination of water by heating to 120 °C. Activation energies of 98 ± 2 and 93 ± 2 kJ mol -1 were found for the hydrated and dried samples, respectively, and similar profiles of activation energy as a function of conversion factor were observed for these samples. Uniterms:Carbamazepine/thermal analysis. Polymorphism. Hydrate. Dehydration.A carbamazepina (CBZ) é um anticonvulsivante frequentemente utilizado no Brasil e em vários países. Ela apresenta quatro formas polimórficas e um diidrato. Todas as formas são ativas farmacologicamente, porém a Forma III é a preferível do ponto de vista farmacêutico, em função de suas propriedades físico-químicas. Entretanto, essa forma é altamente higroscópica, podendo converter-se ao diidrato, menos ativo biologicamente. Nesse trabalho propõe-se avaliar o comportamento térmico da forma hidratada, visando à recuperação da forma ativa, por aquecimento. Para tanto, foi feito um estudo do comportamento térmico por TG/DTG-DTA e DSC em atmosfera dinâmica de ar e nitrogênio, que evidenciou hidratação espontânea da Forma III, gerando um hidrato contendo 1,5 moléculas de água. Essa forma sofre desidratação, seguida de fusão e conversão para a Forma I. Segue-se a decomposição em uma única etapa, na qual ocorre liberação do ácido isociânico, conforme análise de gases evolvidos, por termogravimetria acoplada ao infravermelho (TG-FTIR). Estudos por calorimetria exploratória diferencial mostraram que a Forma III se funde e se cristaliza imediatamente na Forma I, durante o aquecimento. A Forma I também se funde e ciclos de aquecimento/resfriamento posteriores evidenciaram que a substância se cristaliza apenas na Forma I por resfriamento. Estudos cinéticos da decomposição, em estado sólido, mostraram que não há alteração na substância pela eliminação da água por aquecimento, sendo determinados valores de energia de ativação da ordem de 98 ± 2 e 93 ± 2 kJ mol -1 , respectivamente, para a amostra hidratada e submeti...

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“…A mass loss of ca. 68.6% between 25°C and 800°C corresponds to the theoretical weight loss (69.4%) of 1 to strontium titanate (SrTiO 3 ) [31]. The powder annealed in air at 700°C had typical XRD pattern for a well-crystallized SrTiO 3 phase (Fig.…”

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confidence: 87%