Literatura académica sobre el tema "TiO2 polymorphs"
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Artículos de revistas sobre el tema "TiO2 polymorphs"
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Eddy, Diana Rakhmawaty, Muhamad Diki Permana, Lintang Kumoro Sakti, Geometry Amal Nur Sheha, Solihudin, Sahrul Hidayat, Takahiro Takei, Nobuhiro Kumada y Iman Rahayu. "Heterophase Polymorph of TiO2 (Anatase, Rutile, Brookite, TiO2 (B)) for Efficient Photocatalyst: Fabrication and Activity". Nanomaterials 13, n.º 4 (12 de febrero de 2023): 704. http://dx.doi.org/10.3390/nano13040704.
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TiO2 exists naturally in three crystalline forms: anatase, rutile, brookite, and TiO2 (B). These polymorphs exhibit different properties and consequently different photocatalytic performances. This paper aims to clarify the differences between titanium dioxide polymorphs, and the differences in homophase, biphase, and triphase properties in various photocatalytic applications. However, homophase TiO2 has various disadvantages such as high recombination rates and low adsorption capacity. Meanwhile, TiO2 heterophase can effectively stimulate electron transfer from one phase to another causing superior photocatalytic performance. Various studies have reported the biphase of polymorph TiO2 such as anatase/rutile, anatase/brookite, rutile/brookite, and anatase/TiO2 (B). In addition, this paper also presents the triphase of the TiO2 polymorph. This review is mainly focused on information regarding the heterophase of the TiO2 polymorph, fabrication of heterophase synthesis, and its application as a photocatalyst.
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Serga, Vera, Regina Burve, Aija Krumina, Marina Romanova, Eugene A. Kotomin y Anatoli I. Popov. "Extraction–Pyrolytic Method for TiO2 Polymorphs Production". Crystals 11, n.º 4 (16 de abril de 2021): 431. http://dx.doi.org/10.3390/cryst11040431.
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The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 powders. A titanium-containing precursor (extract) was prepared by liquid–liquid extraction using valeric acid C4H9COOH without diluent as an extractant. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), as well as the Fourier-transform infrared (FTIR) spectroscopy were used to determine the temperature conditions to fabricate TiO2 powders free of organic impurities. The produced materials were also characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The results showed the possibility of the fabrication of storage-stable liquid titanium (IV)-containing precursor, which provided nanocrystalline TiO2 powders. It was established that the EPM permits the production of both monophase (anatase polymorph or rutile polymorph) and biphase (mixed anatase–rutile polymorphs), impurity-free nanocrystalline TiO2 powders. For comparison, TiO2 powders were also produced by the precipitation method. The results presented in this study could serve as a solid basis for further developing the EPM for the cheap and simple production of nanocrystalline TiO2-based materials in the form of doped nanocrystalline powders, thin films, and composite materials.
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Dima, Ratshilumela S., Lutendo Phuthu, Nnditshedzeni E. Maluta, Joseph K. Kirui y Rapela R. Maphanga. "Electronic, Structural, and Optical Properties of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells—A First Principles Study". Materials 14, n.º 14 (14 de julio de 2021): 3918. http://dx.doi.org/10.3390/ma14143918.
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Titanium dioxide (TiO2) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO2 polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO2 brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO2 brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO2 brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO2 brookite (210) surfaces.
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Poleti, Dejan, Ljiljana Karanovic, Miodrag Zdujic y Cedomir Jovalekic. "Phase composition of Bi2O3 specimens doped with Ti, Zr and Hf". Journal of the Serbian Chemical Society 77, n.º 8 (2012): 1091–96. http://dx.doi.org/10.2298/jsc110914215p.
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Powder mixtures of ?-Bi2O3 containing 2, 5 and 10 mole % of TiO2, ZrO2 or HfO2 were homogenized, heated at 820?C for 24 h and quenched in air. X-ray powder diffraction technique was used to characterize the prepared samples. In all cases metastable Bi2O3 polymorphs, ?-Bi2O3 or ?-Bi2O3, are found as single or major phases. Addition of Ti4+ ions stabilizes ?-Bi2O3 polymorph, while either Zr4+ or Hf4+ ions stabilize ?-Bi2O3 polymorph. In the samples with 2 and 5 mole % of TiO2 the presence of even two ?-Bi2O3 phases (Bi12TiO20 compound and a very low Ti-doped ?-Bi2O3) was established. Similarly, in the sample with 2 mole % of HfO2 two ?-Bi2O3 phases were found. Phase composition of prepared samples, values of unit cell parameters and the appearance of two polymorphs with identical crystal structure but different unit cell parameters are discussed and compared with known data.
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Basavaraj, K., Anupriya Nyayban y Subhasis Panda. "Structural phase transitions and elastic properties of TiO2 polymorphs: Ab-initio study". IOP Conference Series: Materials Science and Engineering 1248, n.º 1 (1 de julio de 2022): 012064. http://dx.doi.org/10.1088/1757-899x/1248/1/012064.
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Abstract TiO2 has tremendously drawn the attention of researchers from the photocatalytic to photovoltaic groups. To explore further avenues of applications, it is important to understand various properties and the phase transformations of TiO2 polymorphs at ambient conditions. The detailed study on the phase transitions (pressure induced) of the low-pressure polymorphs (rutile, anatase, brookite and columbite) of TiO2 is surprisingly missing in the literature. In view of the above, we have carried out ab-initio calculations on these four polymorphs of TiO2 using full potential linearized augmented plane wave [FP-LAPW] method to study the structural phase transitions and elastic properties. The transition pressures at 0 K among anatase (A), rutile (R), brookite (B) and columbite (C) are found out to be -2.4 GPa (A-B), 5.3 GPa (A-R), 5.7 GPa (A-C), 8.7 GPa (R-C), 10.7 GPa (B-C) and 11.6 GPa (B-R) respectively. The elastic properties at P = 0 GPa are examined through computation of elastic constants for all polymorphs. All the polymorphs are found to be mechanically stable. The anisotropy in shear moduli and directional dependence of Young's modulus are also investigated for all the polymorphs.
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Song, Miao, Zexi Lu y Dongsheng Li. "Phase transformations among TiO2 polymorphs". Nanoscale 12, n.º 45 (2020): 23183–90. http://dx.doi.org/10.1039/d0nr06226j.
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Nagy, Dávidné, Tamás Firkala, Eszter Drotár, Ágnes Szegedi, Krisztina László y Imre Miklós Szilágyi. "Photocatalytic WO3/TiO2 nanowires: WO3 polymorphs influencing the atomic layer deposition of TiO2". RSC Advances 6, n.º 98 (2016): 95369–77. http://dx.doi.org/10.1039/c6ra18899k.
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Shi, Huili, Chaoyun Shi, Zhitong Jia, Long Zhang, Haifeng Wang y Jingbo Chen. "Titanium dioxide-based anode materials for lithium-ion batteries: structure and synthesis". RSC Advances 12, n.º 52 (2022): 33641–52. http://dx.doi.org/10.1039/d2ra05442f.
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In this paper, the structure of three TiO2 polymorphs are introduced, then the preparation and electrochemical properties of TiO2 with different morphologies and the related research on the composite with carbon and other materials are discussed.
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Asagoe, Keisuke, Supachai Ngamsinlapasathian, Yoshikazu Suzuki y Susumu Yoshikawa. "Addition of TiO2 nanowires in different polymorphs for dye-sensitized solar cells". Open Chemistry 5, n.º 2 (1 de junio de 2007): 605–19. http://dx.doi.org/10.2478/s11532-007-0001-4.
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AbstractTiO2 (B) and TiO2 anatase nanowires were prepared at 150 °C for 120 h by a hydrothermal method followed by calcination in air at 400 °C for 2 h and at 700 °C for 2 h for TiO2 (B) and TiO2 anatase, respectively. Although dye-sensitized solar cells (DSC) with fully nanowire electrodes showed a rather low light-to-electricity conversion efficiency of 1.33 % for TiO2 (B) and 2.42% for TiO2 anatase, 10 wt % nanowire-dispersed electrodes in a P-25 TiO2-nanoparticle matrix demonstrated improved efficiency of 6.17 % for TiO2 (B) and 6.53% for TiO2 anatase, these exceeding that of pure P-25 electrodes in this work (η=5.59%). The dominant mechanisms of the improvement at 10 wt% for the two different polymorphs are thought to be different, i.e., a light-scattering and film-thickness increment for the TiO2 (B) system, whereas there is an improved conduction path through the matrix for the TiO2 anatase system.
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Gaspar, Miguel, Nuno Grácio, Rute Salgueiro y Mafalda Costa. "Trace Element Geochemistry of Alluvial TiO2 Polymorphs as a Proxy for Sn and W Deposits". Minerals 12, n.º 10 (30 de septiembre de 2022): 1248. http://dx.doi.org/10.3390/min12101248.
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The Segura mining field, the easternmost segment of the Góis–Panasqueira–Segura tin–tungsten metallogenic belt (north–central Portugal), includes Sn-W quartz veins and Li-Sn aplite-pegmatites, which are believed to be genetically related to Variscan Granites. Sediment geochemistry indicates granite-related Ti-enrichments, locally disturbed by mineralization, suggesting magmatic and metamorphic/metasomatic titaniferous phases. Therefore, Segura alluvial samples and the geochemistry of their TiO2 polymorphs (rutile, anatase, and brookite) were investigated, and their potential as exploration tools for Sn and W deposits was evaluated. The heavy-mineral assemblages proved to be good proxies for bedrock geology, and TiO2 polymorph abundances were found to be suitable indicators of magmatic and/or metasomatic hydrothermal processes. The trace element geochemistry of Segura’s alluvial rutile, anatase, and brookite is highly variable, implying multiple sources and a diversity of mineral-forming processes. The main compositional differences between TiO2 polymorphs are related to intrinsic (structural) factors, and to the P-T-X extrinsic parameters of their forming environments. Anomalous enrichments, up to 9% Nb, 6% Sn and W, 3% Fe, 2% Ta, and 1% V in rutile, and up to 1.8% Fe, 1.7% Ta, 1.2% Nb, 1.1% W 0.5% Sn and V in anatase, were registered. Brookite usually has low trace element content (<0.5%), except for Fe (~1%). HFSE-rich and granitophile-rich rutile is most likely magmatic, forming in extremely differentiated melts, with Sn and W contents enabling the discrimination between Sn-dominant and W-dominant systems. Trace element geochemical distribution maps show pronounced negative Sn (rutile+anatase) and W (rutile) anomalies linked to hydrothermal cassiterite precipitation, as opposed to their hydrothermal alteration halos and to W-dominant cassiterite-free mineralized areas, where primary hydrothermal rutile shows enrichments similar to magmatic rutile. This contribution recognizes that trace element geochemistry of alluvial TiO2 polymorphs can be a robust, cost- and time-effective, exploration tool for Sn(W) and W(Sn) ore deposit systems.
Tesis sobre el tema "TiO2 polymorphs"
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Deswaziere, Antoine. "Propriétés photo-électrochimiques de la brookite pour la photo-électrolyse de l’eau et comparaison aux autres phases de TiO2". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS298.
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La photo-électrolyse de l’eau est une alternative prometteuse pour décarboner la production mondiale de dihydrogène à partir de matériaux abondants à la surface terrestre, peu chers et non-toxiques comme le TiO2. Parmi tous ses polymorphes, seules les phases de rutile et d’anatase ont été étudiées : les propriétés de la brookite sont moins connues. Ici, nous présentons une approche particulaire, consistant à synthétiser des particules de TiO2 de phase pure, de taille et de morphologie choisies, puis de mettre en forme une photoanode à la microstructure contrôlée à partir de ces « briques élémentaires ». Les nanoparticules des 3 polymorphes de TiO2 anatase, brookite et rutile ont été synthétisées puis déposées sur FTO par une technique de « dip-coating » et traitées thermiquement afin d’assurer un bon contact électronique. La phase de TiO2 brookite a d’abord été caractérisée ; en particulier, les propriétés influençant la microstructure de l’électrode comme la taille et la morphologie des nanoparticules mais aussi l’épaisseur et la porosité de l’électrode ont été étudiées et corrélées aux performances photo-électrochimiques. D’une façon intéressante, les faibles photocourants n’ont pas pu être expliqués par les recombinaisons des porteurs de charge aux interfaces « particule – particule » mais davantage dans le « bulk » de la particule elle-même. Ces propriétés de « bulk » ont alors été évaluées pour les trois polymorphes. Finalement, une hétérostructure anatase – rutile a été testée et a montré une augmentation des photocourants significative par rapport aux phases pures, qui a pu été attribuée à l’amélioration de la séparation et de la mobilité des porteurs de chargeThe use of solar energy via photoelectrochemical water splitting is an attractive approach for clean hydrogen production. Because of its physico-chemical properties, Earth abundance and non-toxicity, TiO2 is one of the most studied photoanode material. Yet the focus is only put on the anatase and rutile structures. However, photoelectrochemical properties of TiO2 brookite remain quite unknown and need to be assessed. Here we present an easy, scalable synthesis approach for photoanodes allowing a good control of crystallinity, shape and particles size and their organization in the photoanode. The three different pure phases of TiO2 nanoparticles were synthetized, assembled into a photoanode with a dip-coating technique and appropriately sintered to obtain good film cohesion. The brookite phase is first studied: parameters such as thickness and porosity of the electrode, crystallinity and size of the crystallites are carefully investigated to understand their influence on the photoanode performances. Interestingly, its poor photocurrent cannot be attributed to electron-hole recombination at grains interfaces rather than charge carrier separation and transfer properties in the bulk of the particles. Furthermore, the influence of the TiO2 phase is evaluated. Because of small particles size and isotropic morphology, poor electron and hole transfer were found too deleterious to establish an indicative performance hierarchy between anatase, brookite and rutile pure phases. Eventually, phase mixture of anatase – rutile was investigated and showed a significant performance increase attributed to the improvement of charge carrier separation and mobility
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Zhang, Geshan. "The Degradation of Cyanotoxins by using Polymorphic Titanium Dioxide Based Catalysts". University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406810827.
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Spektor, Kristina. "Extreme water catalyzed transformations of SiO2, TiO2 and LiAlSiO4". Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-124010.
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The dramatic change in properties of water near its critical point (i.e. T = 374 °C and p = 22.1 MPa, note: 100 MPa = 0.1 GPa = 1 kbar ≈ 1000 atm) has been a subject of numerous studies and also lead to the development of various applications (e.g. in waste destruction, biomass processing, and the synthesis of advanced ceramic materials). However, comparatively little is known about the behavior of water at gigapascal pressures. The present study attempts to explore catalytical properties and reactivity of extreme water with respect to several oxide systems: SiO2, TiO2 and LiAlSiO4. “Extreme water” here is defined as existing at p,T conditions of 0.25–10 GPa and 200–1000 °C, thus considering both supercritical fluid and hot compressed ice. The study shows that extreme water can make high pressure mineral phases accessible at relatively mild T conditions. At the same time, high pressure aqueous environments appear efficient in stabilizing novel metastable structures and may be considered as a general route for synthesizing new materials. The hydrothermal treatment of SiO2 glass at 10 GPa and 300–550 °C yielded an unusual ultrahydrous form of stishovite with up to 3% of structural water. At the same time, the extreme water environment enhanced notably the kinetics of stishovite formation, making it accessible at unprecedentedly low temperatures. Thus, for the SiO2–H2O system water acts as both catalyst and reactant. For TiO2 a hydrothermal high pressure treatment proved to be of high importance for overcoming the kinetical hindrance of the rutile – TiO2-II transformation. 6 GPa and 650 °C were established as the mildest conditions for synthesizing pure TiO2-II phase in less than two hours. The crystallization of LiAlSiO4 glass in an extreme water environment yielded a number of different phases. In the low pressure region (0.25 – 2 GPa) mainly a zeolite (Li-ABW) and a dense anhydrous aluminosilicate (α-eucryptite) were obtained. At pressures above 5 GPa the formation of novel pyroxene-like structures with crystallographic amounts of structural water was observed. The overall conclusion of this study is that extreme water environments show a great potential for catalyzing phase transitions in oxide systems and for stabilizing novel structures via structural water incorporation.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Dantas, M?rcia Danielle de Ara?jo. "Estudo do genoma do v?rus causador da mionecrose infecciosa em camar?es e desenvolvimento de m?todos para detec??o de polimorfismos". Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12630.
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Shrimp farming is one of the activities that contribute most to the growth of global aquaculture. However, this business has undergone significant economic losses due to the onset of viral diseases such as Infectious Myonecrosis (IMN). The IMN is already widespread throughout Northeastern Brazil and affects other countries such as Indonesia, Thailand and China. The main symptom of disease is myonecrosis, which consists of necrosis of striated muscles of the abdomen and cephalothorax of shrimp. The IMN is caused by infectious myonecrosis virus (IMNV), a non-enveloped virus which has protrusions along its capsid. The viral genome consists of a single molecule of double-stranded RNA and has two Open Reading Frames (ORFs). The ORF1 encodes the major capsid protein (MCP) and a potential RNA binding protein (RBP). ORF2 encodes a probable RNA-dependent RNA polymerase (RdRp) and classifies IMNV in Totiviridae family. Thus, the objective of this research was study the IMNV complete genome and encoded proteins in order to develop a system differentiate virus isolates based on polymorphisms presence. The phylogenetic relationship among some totivirus was investigated and showed a new group to IMNV within Totiviridae family. Two new genomes were sequenced, analyzed and compared to two other genomes already deposited in GenBank. The new genomes were more similar to each other than those already described. Conserved and variable regions of the genome were identified through similarity graphs and alignments using the four IMNV sequences. This analyze allowed mapping of polymorphic sites and revealed that the most variable region of the genome is in the first half of ORF1, which coincides with the regions that possibly encode the viral protrusion, while the most stable regions of the genome were found in conserved domains of proteins that interact with RNA. Moreover, secondary structures were predicted for all proteins using various softwares and protein structural models were calculated using threading and ab initio modeling approaches. From these analyses was possible to observe that the IMNV proteins have motifs and shapes similar to proteins of other totiviruses and new possible protein functions have been proposed. The genome and proteins study was essential for development of a PCR-based detection system able to discriminate the four IMNV isolates based on the presence of polymorphic sites
A carcinicultura ? uma das atividades que mais contribui para o crescimento da aquicultura mundial. Entretanto, esta atividade vem sofrendo perdas econ?micas significativas devido ao surgimento de doen?as virais como a Mionecrose Infecciosa (IMN). A IMN j? est? disseminada em toda regi?o Nordeste do Brasil e atingiu outros pa?ses como Indon?sia, Tail?ndia e China. O principal sintoma da doen?a ? a mionecrose, que consiste na necrose dos m?sculos estriados do abd?men e do cefalot?rax do camar?o. A IMN ? causada pelo v?rus da mionecrose infecciosa (IMNV), um v?rus n?o envelopado que apresenta protrus?es ao longo de seu caps?deo. O genoma viral ? formado por uma ?nica mol?cula de RNA dupla fita e possui duas Open Reading Frames (ORFs). A ORF1 codifica a prote?na principal do caps?deo (MCP) e uma poss?vel prote?na de liga??o a RNA (RBP). A ORF2 codifica uma prov?vel RNA polimerase dependente de RNA (RdRp) e classifica o IMNV dentro da fam?lia Totiviridae. Assim, o objetivo desse estudo foi estudar o genoma completo do IMNV e as prote?nas codificadas no intuito de desenvolver um sistema que identificasse diferentes isolados do v?rus com base na presen?a de polimorfismos. A rela??o filogen?tica entre alguns totiv?rus foi investigada e mostrou um novo grupo para o IMNV dentro da fam?lia Totiviridae. Dois novos genomas foram sequenciados, analisados e comparados a outros dois genomas j? depositados no GenBank. Os novos genomas foram mais semelhantes entre si do que com aqueles j? descritos. Regi?es vari?veis e conservadas do genoma foram identificadas atrav?s de gr?ficos de similaridade e alinhamentos utilizando as quatro sequ?ncias do IMNV. Esta an?lise possibilitou o mapeamento de s?tios polim?rficos e revelou que a regi?o mais vari?vel do genoma se encontra na primeira metade da ORF1 e coincide com as regi?es que possivelmente codificam a protrus?o viral, enquanto que as regi?es mais est?veis se encontraram em dom?nios conservados de prote?nas que interagem com o RNA. Al?m disso, estruturas secund?rias foram preditas para todas as prote?nas empregando diversos softwares e modelos estruturais proteicos foram calculados usando modelagens por threading e simula??es ab initio. A partir dessas an?lises foi poss?vel observar que as prote?nas do IMNV possuem motivos e formas similares ?s prote?nas de outros totiv?rus, e novas poss?veis fun??es proteicas foram propostas. O estudo do genoma e das prote?nas foi essencial para o desenvolvimento de um sistema de detec??o baseado em PCR capaz de discriminar os quatro isolados do IMNV com base na presen?a de s?tios polim?rficos
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Li, Huei-wen y 李惠雯. "Photodegradation of diethyl phthalate (DEP) by polymorphs TiO2 co-doped with PANi and CNT irradiated with visible light". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/894amc.
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Brás, Elisa Cristina Marçalo. "On the Tautomerism of 2-Mercaptoimidazoles and 2-Mercaptobenzimidazoles: A Low Temperature Matrix Isolation and Solid State Study". Master's thesis, 2017. http://hdl.handle.net/10316/83322.
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Dissertação de Mestrado em Química apresentada à Faculdade de Ciências e TecnologiaApesar da sua relevância em vários processos químicos, o tautomerismo tiona-tiol não tem sido alvo de muitas investigações. O trabalho apresentado nesta tese centra-se no do tautomerismo nas moléculas 2-mercaptoimidazol, 2-mercaptobenzimidazol e dos seus derivados de metil (1-metil-2-mercaptoimidazol e 1-metil-2-mercaptobenzimidazol). O tautomerismo fotoinduzido foi investigado através da técnica de espectroscopia de infravermelho com isolamento em matrizes criogénicas e métodos computacionais. Antes da irradiação, a comparação da informação espectral experimental e calculada levou à conclusão de que o tautómero tiona era único tautómero presente nas matrizes. Este resultado apresenta-se coerente com os cálculos realizados ao nível DFT (B3LYP) / 6-11 ++ G (d, p), através dos quais foi possível concluir que o tautómero tiona é o tautómero termodinamicamente mais estável. Após a irradiação com luz UV de banda estreita, cujo comprimento de onda foi selecionado criteriosamente, os tautómeros tiona das espécies isoladas foram parcialmente convertidos nos respectivos tióis. Para além disso, a reversibilidade do tautomerismo foi confirmada para o caso dos 2-mercaptoimidazóis benzo substituídos através da irradiação selectiva a λ = 246 nm. Este processo é mais eficiente que a conversão thiona → thiol.Uma vez que estas espécies não são estabilizadas por interacções intramoleculares, facto que é sustentado pelas estruturas cristalinas e pelos dados teóricos, o mecanismo por transferência de protão intramolecular (ESIPT) não deve ser considerado. Um possível mecanismo consiste na transferência de átomo de hidrogénio do anel imidazol para o átomo de enxofre. A investigação sobre o tautomerismo do 2-mercaptoimidazole no estado sólido também foi realizada através de microscopia Raman, difração de raios X, microscopia térmica de luz polarizada e calorimetria diferencial de varrimento. Os resultados das experiências realizadas comprovaram apenas a presença do tautómero mais estável e o polimorfismo, desta forma, também não foi observado. No decorrer das investigações do estado sólido, um novo polimorfo do composto 2 -[(1H-imidazol-2-il)dissulfanil]-1H-imidazole foi sintetizado e analisado por espectroscopia de Raman e difracção de raios-X de monocristal. Os resultados revelaram uma estrutura com quatro moléculas independentes por simetria na célula unitária (Z '= 4). As propriedades térmicas desta nova estrutura também foram investigadas.
The thione-thiol tautomerism has been only scarcely investigated in spite of its well-known relevance in chemical processes. In this thesis, investigations on the tautomerism of 2-mercaptoimidazole, 2-mercaptobenzimidazole and its 1-methyl substituted derivatives (1-methyl-2-mercaptoimidazole and 1-methyl-2-mercaptobenzimidazole) are reported.Photoinduced thione-thiol tautomerism in these molecules was investigated by low-temperature matrix isolation spectroscopy and quantum chemical calculations. The initial population of all the experiments comprised only the thione tautomer, the thermodynamically most stable tautomer predicted by DFT(B3LYP)/6-11++G(d,p) calculations. Upon in situ narrowband UV irradiation, the as-deposited thiones were partially converted into thiols. The reverse photoreversibility of the process was proved for the benzosubstituted 2-mercaptoimidazoles by a selective irradiation at λ = 246 nm, showing greater efficiency than thione → thiol conversion. Since these molecular species may be not stabilized by intramolecular interactions, which was confirmed by both crystal structures and calculations, the mechanism of phototautomerization may occurred by a hydrogen atom transfer from the nitrogen of the imidazole ring to the sulphur atom, instead of by the well-known ESIPT process. The investigation on the tautomerism of 2-mercaptoimidazole in the solid state was also undertaken by Raman microscopy, X-ray diffraction, polarized light thermal microscopy and differential scanning calorimetry. The results shown only the presence of thione tautomer in the solid state and polymorphism was not observed. In the course of solid state investigations, a new polymorph of 2-[(1H-Imidazol-2-yl)disulfanyl]-1H-imidazole was synthetized and analyzed by Raman spectroscopy and single crystal X-ray diffraction. X-ray results revealed a structure with four symmetry independent molecules in the unit cell (Z’ = 4). Thermal properties of this new structure were also investigated.
Capítulos de libros sobre el tema "TiO2 polymorphs"
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Christoforidis, Konstantinos C. y Paolo Fornasiero. "TiO2 polymorphs for hydrogen photoproduction". En Current Developments in Photocatalysis and Photocatalytic Materials, 127–40. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-12-819000-5.00009-6.
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Mhadhbi, Mohsen, Houyem Abderazzak y Barış Avar. "Synthesis and Properties of Titanium Dioxide Nanoparticles". En Updates on Titanium Dioxide [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.111577.
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Natural titanium dioxide (TiO2) occurs in three distinct polymorphs (rutile, anatase, and brookite). Currently, TiO2 gained the attention of several researchers around the world. TiO2 is used in several applications because of its excellent properties (structural, optical, electrical, chemical, non toxic, etc.). Thus, the applications are influenced by its surface, size, morphology, and crystal phase. TiO2 as photocatalyst is widely used in energy and eco-friendly applications involving water purification, hydrogen production, phenol degradation, etc. The novelty of the present chapter lies in explaining the recently reported methods that are used to synthesize TiO2 nanoparticles, such as sol-gel, hydrothermal, precipitation, etc. The different properties of TiO2 are also provided in this chapter.
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Dudziak, Szymon, Marta Kowalkińska y Anna Zielińska-Jurek. "Crystal Facet Engineering of TiO2 from Theory to Application". En Updates on Titanium Dioxide [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.111565.
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Recently, the surface structure effect on photocatalytic activity has gathered increasing attention due to its reported influence on the charge carrier trapping and separation. Detailed control over the surface structure can be achieved by exposing the specific crystal facets. As a result, the photogenerated electrons and holes can be effectively separated between the different facets of semiconductor crystals. TiO2 is the most studied photocatalyst, with the particles exposing {0 0 1}, {1 0 0}, {1 0 1}, {1 1 0}, {1 1 1}, and {1 0 5} crystal facets. The performed studies have shown that the efficiency of the photocatalytic process strongly depends on the nature of the crystal facet exposed at the photocatalyst surface. In this regard, this chapter focuses on the comparison of possible surface-related parameters and photocatalytic activity of anatase, rutile, and brookite polymorphs with exposed different crystal facets. Particularly, computational data on their different possible surface structures are summarized, focusing on the geometry, energy, and possible reconstructions. This is followed by the general description of the hypothetical Wulff constructions and existing stabilization/synthesis strategies. Such an approach could help to further design, simulate, and optimize photocatalyst surface for efficient photoreduction and photooxidation processes.
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Ariyanti, Dessy, Aprilina Purbasari, Dina Lesdantina, Filicia Wicaksana y Wei Gao. "Modified TiO2 Nanomaterials as Photocatalysts for Environmental Applications". En Food Sustainability, Environmental Awareness, and Adaptation and Mitigation Strategies for Developing Countries, 103–17. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-5629-3.ch006.
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Since the water splitting breakthrough using semiconductor reported in 1972, titanium dioxide (TiO2) has been extensively investigated as a promising material used in broad range of research areas. TiO2 is a transition metal oxide semiconductor with three distinct polymorph crystalline structures. With that alone TiO2 established remarkable performance as photocatalyst for organic photodegradation in the irradiation of UV. However, improvement on the light absorption properties that support the excellent photocatalytic activity still needs to be pursued for wider environmental application. In this book chapter, the limitations of TiO2 as photocatalyst were discussed especially in the industrial wastewater treatment application. The strategies in overcoming the limitation by TiO2 morphology and surface modification were also presented. The modified TiO2 nanomaterials proves to have excellent photocatalytic activity in dyes (Rhodamine B, Methyl Orange and Methylene Blue) as representative of organic pollutant degradation and Cu (II) reduction as representative of inorganic pollutant.
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Jolivet, Jean-Pierre. "Titanium, Manganese, and Zirconium Dioxides". En Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0011.
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The dioxides of titanium (TiO2), manganese (MnO2), and zirconium (ZrO2) are important materials because of their technological uses. TiO2 is used mainly as white pigment. Because of its semiconducting properties, TiO2, in its nanomaterial form, is also used as an active component of photocells and photocatalysis for self-cleaning glasses and cements . MnO2 is used primarily in electrode materials. ZrO2 is used in refractory ceramics, abrasive materials, and stabilized zirconia as ionic conductive materials stable at high temperature. Many of these properties are, of course, dependent on particle size and shape (§ Chap. 1). Dioxides of other tetravalent elements with interesting properties have been studied elsewhere in this book, especially VO2, which exhibits a metal–isolator transition at 68°C, used, for instance, in optoelectronics (§ 4.1.5), and silica, SiO2 (§ 4.1.4), which is likely the most ubiquitous solid for many applications and uses. Aqueous chemistry is of major interest in synthesizing these oxides in the form of nanoparticles from inorganic salts and under simple, cheap, and environmental friendly conditions. However, as the tetravalent elements have restricted solubility in water (§ 2.2), metal–organic compounds such as titanium and zirconium alkoxides are frequently used in alcoholic solution as precursors for the synthesis of TiO2 and ZrO2 nanoparticles. An overview of the conversion of alkoxides into oxides is indicated about silica formation (§ 4.1.4), and since well-documented works have already been published, these compounds are not considered here. The crystal structures of most MO2 dioxides are of TiO2 rutile type for hexacoordinated cations (e.g., Ti, V, Cr, Mn, Mo, W, Sn, Pb) and CaF2 fluorite type for octacoordinated, larger cations (e.g., Zr, Ce), but polymorphism is common. Some dioxides of elements such as chromium and tin form only one crystalline phase. So, hydrolysis of SnCl4 or acidification of stannate [Sn(OH)6]2− leads both to the same rutile-type phase, cassiterite, SnO2. Many other dioxides are polymorphic, especially TiO2, which exists in three main crystal phases: anatase, brookite, and rutile; and MnO2, which gives rise to a largely diversified crystal chemistry.
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Smith, Moyra. "Advances In Genome Analysis: Discovery Of Structural Variation And Genomic Dosage Differences In Health And Disease". En Translational Researchin Genetics and Genomics, 21–35. Oxford University PressNew York, NY, 2008. http://dx.doi.org/10.1093/oso/9780195313765.003.0002.
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Abstract Resources to search for genomic variation have rapidly expanded with availability of the genomic sequence, development of fluorescence-based genomic hybridization in analysis of chromosomes, and particularly through availability of microarray technologies. Comparative genomic hybridization using arrayed Bac clones with large inserts (approximately 170 kb) of human genomic DNA has been particularly informative. Structural genomic information is also becoming more intensely studied through use of oligonucleotide arrays and single nucleotide polymorphism (SNP) arrays (described below). One of the most surprising discoveries in human genome research between 2005 and 2007 relates to the extent of copy number variation (CNV) of large genomic segments. In establishing the role of CNVs in genetic disease, it is particularly important to distinguish between normal variations and disease-causing variations. The application of extended SNP data and of microarray data to analysis of human genetic disease requires that background informa- tion be gathered to determine the extent of normal variation in the genome in that population.
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Girman, Derek J. "The Use of PCR-Based Single-Stranded Conformation Polymorphism Analysis (PCR-SSCP) in Conservation Genetics". En Molecular Genetic Approaches in Conservation, 167–82. Oxford University PressNew York, NY, 1996. http://dx.doi.org/10.1093/oso/9780195095265.003.0011.
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Abstract The use of molecular markers to investigate the population structure of endangered or threatened species has become a key component in the genetic management of endangered species (see chapter 1). The identification of variable genetic loci has allowed the analysis of DNA sequence data to become one of the most useful measures of genetic differentiation, genetic variability, and evolutionary related¬ ness for conservation-oriented analysis at or below the species level (Wayne and Jenks, 1991; Wenink et al. 1993; Gottelli et al., 1994; Rosel et al., 1994; Taberlet and Bouvet, 1994; Taylor et al., 1994). In addition, the development of PCR (polymerase chain reaction) has allowed specific regions of the genome to be quickly isolated and amplified, so that the products of this relatively simple procedure can be readily sequenced (Saiki et al., 1988). The use of PCR technology is also advantageous because it provides a way to access DNA from a wide variety of sample sources including skin, hair, and feces which allows researchers to use noninvasive sampling methods (Karesh et al., 1987; Hoss et al., 1992; see chapter 18). With increased use of remote sampling, researchers can greatly increase the sample size of their studies, thereby increasing the strength of their analyses. However, with increased sample sizes (often hundreds of individuals), the task of generating DNA sequences from every individual in the study becomes labor-intensive, time-consuming, and costly. To facilitate the identifica¬ tion of DNA sequence genotypes in a more efficient manner, a number of DNA screening techniques have been developed that allow one to distinguish sequence differences among individuals without having to sequence each individual directly. Among the range of techniques that are available, PCR-SSCP (polymerase chain reaction combined with the analysis of single-stranded conformation poly¬ morphisms) has emerged as a favored technique for screening DNA sequences in a wide variety of applications in molecular biology (Desgeorges et al., 1993; Hunter et al., 1993; Pietravalle et al., 1994).
Actas de conferencias sobre el tema "TiO2 polymorphs"
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Siroha, Piyush, Davender Singh, Rakhi Soni y Jitendra Gangwar. "Comparative study on crystallographic representation of transition metal oxides polymorphs nanomaterials using VESTA software: Case study on Fe2O3 and TiO2". En NATIONAL CONFERENCE ON RECENT ADVANCES IN EXPERIMENTAL AND THEORETICAL PHYSICS (RAETP-2018). Author(s), 2018. http://dx.doi.org/10.1063/1.5051294.
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Rizvi, Afsar H., Mohammad Azhar Aziz, F. Ali y A. Ahmad. "Synthesis and characterization of different polymorph of TiO2-polyaniline nanocomposite for energy storage application". En 66TH DAE SOLID STATE PHYSICS SYMPOSIUM. AIP Publishing, 2024. http://dx.doi.org/10.1063/5.0178948.
Texto completoInformes sobre el tema "TiO2 polymorphs"
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Adill, Anders. Ekologiska trender och prognoser i recipientområdet för Forsmarks kärnkraftverk. Institutionen för akvatiska resurser, Sveriges lantbruksuniversitet, 2023. http://dx.doi.org/10.54612/a.570suuv8lh.
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Forsmarks kärnkraftverk är en av Sveriges största elproducenter och utgörs av tre stycken kokvattenreaktorer. Vid elproduktionen i kärnkraftverket krävs enorma mängder havsvatten för kylning av processerna i reaktorerna. Kylvattnet tas in till kraftverket från Öregrundsgrepen via en kanal från Asphällafjärden. Brackvattnet innehåller levande organismer i form av bland annat alger, vattenvegetation, djurplankton och fisk. De största organismerna, bland annat vegetation och fisk, avskiljs från vattnet via stora bandsilar som sitter i kylvattenintaget till kraftverket. Periodvis kan mängden rensmaterial i dessa silar vara omfattande, främst under vårperioden och hösten. Kylvattnet värms upp med cirka 11°C när det passerar över reaktorerna och innan det pumpas ut till Biotestsjön (den huvudsakliga recipienten), och sedan ut till det omgivande havsområdet i Öregrundsgrepen. Vattentemperaturen i Biotestsjön är vid normal energiproduktion 7–9 °C högre än i omgivande områden. Intag och utsläpp av kylvatten ger effekter på den närliggande miljön och dess organismer. Under slutet av 1960-talet påbörjades biologiska förstudier och basundersökningar i Forsmarksområdet för att planera för kärnkraftverket. När elproduktionen inleddes 1980 övergick undersökningarna i fastställda kontrollprogram med syfte att övervaka påverkan på fisk, bottenfauna och fågel i recipientområdet. Under de senaste decennierna har även ett stort fokus riktats för att förbättra miljön i Sveriges havsområden. I havsmiljöförordningen finns ingående beskrivningar för vilka aktiviteter som ska genomföras för att nå fastställda miljömål, bland annat att genomföra miljöövervakning. Övervakningsprogrammen syftar till att ge underlag och följa upp utvecklingen av miljöstatus, som exempelvis beståndsövervakning av fisk och bottenfauna, utveckling i kustfiskbestånden och introduktion av främmande arter. Den samlade miljöövervakningen som genomförs inom recipientkontroll och i nationella övervakningsprogram genererar stor kunskap om rådande miljöstatus, organismsamhällena och utvecklingen för ekosystemen i Forsmarks skärgård och Bottenhavet. Under åren som kärnkraftverket i Forsmark varit i drift har det skett storskaliga miljöförändringar i Bottenhavet. Trots flertalet förvaltningsåtgärder kan det konstateras att miljömålen för exempelvis övergödning, kommersiellt nyttjande av fisk samt spridning av främmande arter inte uppnåtts. De hydrologiska förhållandena som successivt har förändrats har haft en stor påverkan på ekosystemen i Bottenhavet och Forsmarks skärgård. Beståndet av storspigg gynnas av miljöförändringarna och förekommer nu i höga tätheter i Bottenhavet och Forsmarks skärgård, och förväntas finnas i samma omfattning eller öka de kommande åren. I silstationerna vid Forsmark kärnkraftverk kommer detta medföra att mängden storspigg fortsatt kommer att vara omfattande under vårperioderna. Strömming återfinns relativt glest längs kusten under stora delar av året och har historiskt ansamlats i höga tätheter under lekperioden under vårarna. Den negativa beståndsutvecklingen och det omfattande yrkesfisket av strömming i Bottenhavet bidrar sannolikt till att tätheterna minskar de kommande åren. Eftersom strömming förekommer främst som årsyngel i silstationerna kommer biomassorna att vara i låga nivåer. I Forsmarks skärgård har andelen abborre, mört, björkna och löja ökat sedan 1990-talet, arter som föredrar varma vattentemperaturer. Dessa arter förväntas förekomma i liknande tätheter eller något ökande de kommande tio åren. De senaste fyra åren har det noterats en spridningseffekt av mört och björkna från Biotestsjön till övriga delar av skärgården. Utvecklingen i bottenfaunasamhällena i Öregrundsgrepen visar att arter som gynnas av miljöförändringarna ökar i omfattning. I övervakningen av bottenfaunasamhällena påträffas flertalet främmande invasiva arter. Tre arter av musslor har påträffats i recipienten eller i närliggande område som kan utgöra stor påverkan och negativ ekonomisk inverkan på kraftverket. Trekantig brackvattenmussla (Mytilopsis leucophaeata), amerikanska trågmusslan (Rangia cuneata) och vandrarmusslan (Dreissena polymorpha) kan samtliga bilda stora kolonier och potentiellt kunna sätta igen vattenledningar och kylvattensystem. En annan djurgrupp som rapporterats ge negativa konsekvenser i kylvattensystem är maneter. I området där Forsmark kärnkraftverk ligger är dock tätheterna av inhemska maneter mycket lågt och utgör sannolikt ingen stor påverkan, men det skulle kunna ändras om främmande arter etableras i Bottenhavet. Under de senaste decennierna har omfattande moderniseringar genomförts i kraftverket och förändringar i utformningen av kylvattenvägarna. Kylvattenflödena som successivt har ökat den senaste tioårsperioden har bidragit till att större mängder fisk och vegetation sugs in i kylvattenintagen. Musslor är en djurgrupp som gynnas av höga kylvattenflöden och risken finns att främmande arter etablerar sig i kylvattenvägarna. För tillfället genomförs flertalet projekt inom skyddsobjektet, bland annat rivning av piren i utloppet från Biotestsjön och en etablering av elektrobränslefabrik. För att utreda om Forsmarks kylvattenintag och vattenkanaler är tillräckligt robusta i framtiden bör det även vägas in vilka effekter de olika projekten får för omgivande miljö och dess organismer.