Artículos de revistas: "Anhydrous precursors"

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Feng, Guo, Wei Hui Jiang, Jian Min Liu, Quan Zhang, Zi Hu, Li Feng Miao y Qian Wu. "Low-Temperature Synthesis of Magnesium-Stabilized Aluminum Titanate Powder via Non-Hydrolytic Sol-Gel Method". Materials Science Forum 848 (marzo de 2016): 319–23. http://dx.doi.org/10.4028/www.scientific.net/msf.848.319.

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Magnesium-stabilized aluminum titanate powder was prepared via non-hydrolytic sol-gel method using titanium tetrachloride and anhydrous aluminium chloride as precursors, anhydrous ethanol as the oxygen donor, magnesium powder, magnesium fluoride, magnesium ethoxide and anhydrous magnesium acetate as stabilizers. The effect of magnesium stabilizers on low temperature synthesis of aluminum titanate was investigated, and their role and mechanism in stabilizing aluminum titanate were also studied by XRD, FT-IR and thermal expansion dilatometer. The results show that introducing magnesium powder or magnesium fluoride can’t stabilize aluminum titanate, they also lead to the failure of aluminum titanate low-temperature synthesis at 750 °C due to its promotion of non-hydrolytic homogeneous condensation. Anhydrous magnesium acetate and magnesium ethoxide can react with aluminum alkoxide and titanium alkoxide in the precursor mixture to form heterogeneous condensation bonds, which promotes magnesium ion to dope into aluminum titanate lattice at 750 °C, and hence to improve its thermal stability.

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Nagpal, Keshav, Erwan Rauwel, Elias Estephan, Maria Rosario Soares y Protima Rauwel. "Significance of Hydroxyl Groups on the Optical Properties of ZnO Nanoparticles Combined with CNT and PEDOT:PSS". Nanomaterials 12, n.º 19 (10 de octubre de 2022): 3546. http://dx.doi.org/10.3390/nano12193546.

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We report on the synthesis of ZnO nanoparticles and their hybrids consisting of carbon nanotubes (CNT) and polystyrene sulfonate (PEDOT:PSS). A non-aqueous sol–gel route along with hydrated and anhydrous acetate precursors were selected for their syntheses. Transmission electron microscopy (TEM) studies revealed their spherical shape with an average size of 5 nm. TEM also confirmed the successful synthesis of ZnO-CNT and ZnO-PEDOT:PSS hybrid nanocomposites. In fact, the choice of precursors has a direct influence on the chemical and optical properties of the ZnO-based nanomaterials. The ZnO nanoparticles prepared with anhydrous acetate precursor contained a high amount of oxygen vacancies, which tend to degrade the polymer macromolecule, as confirmed from X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, a relative increase in hydroxyl functional groups in the ZnO-CNT samples was observed. These functional groups were instrumental in the successful decoration of CNT and in producing the defect-related photoluminescence emission in ZnO-CNT.

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Bommers, Sebastian y Hubert Schmidbaur. "Poly(trifluoromethanesulfonatosilyl)methanes - Precursors to Polysilylmethanes". Zeitschrift für Naturforschung B 49, n.º 3 (1 de marzo de 1994): 337–39. http://dx.doi.org/10.1515/znb-1994-0308.

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AbstractA new and efficient synthetic route to di- and tri(silyl)methane is presented. Starting from bis- and tris(phenylsilyl)methane, bis- and tris(trifluoromethanesulfonatosilyl)methane can be obtained by Si-Ph cleavage with equivalent quantities of trifluoromethanesulfonic acid (triflic acid). Their reduction with lithium aluminium hydride yields di- and tri(silyl)methane. Substitution of the previously employed liquid anhydrous hydrogen bromide by triflic acid thus offers an experimentally more simple alternative with shorter reaction times and high selectivity.

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4

Purdy, Andrew P. y Clifford F. George. "Anhydrous Dithiocarbamates. Potential Precursors to Alkaline Earth Sulfide Materials". Main Group Chemistry 1, n.º 2 (marzo de 1996): 229–40. http://dx.doi.org/10.1080/13583149612331338465.

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Heckman, J. W., M. J. Kielszewski, D. T. A. Lamport, E. P. Muldoon, B. T. Terhune y J. J. Willard. "Interspecific comparison of elutable cell wall extensin precursors by transmission electron microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 44 (agosto de 1986): 284–85. http://dx.doi.org/10.1017/s0424820100143043.

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In addition to cellulose microfibrils, the primary cell wall of many higher plants contains extensin, a class of hydroxyproline-rich glycoprotein (HRGP). Despite its predominately hydrophilic amino acid composition, most cell wall HRGP remains insoluble even after complete deglycosylation with anhydrous HF, suggesting a covalently linked macromolecular network. This led to the development of the "warp-weft" cell wall model, based on an extensin network ("weft") penetrated by cellulose microfibrils (the "warp")(FIG. 1). Extensin precursors elute rapidly from intact cells and cell wall preparations of tomato, carrot, and cucumber, with mild salt solutions. Tomato precursors, at least, are block copolymers of a few repeating sequences. Gel filtration data and immuno-crossreactivity suggest that tomato P2 and cucumber callus precursor are similar. TEM confirms the rod-like structure and the lengths of these molecules.

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Bénard, Patricia, Jean Paul Auffrédic y Daniel Louër. "High-temperature X-ray powder diffractometry of the decomposition of zirconium hydroxide nitrates". Powder Diffraction 8, n.º 1 (marzo de 1993): 39–46. http://dx.doi.org/10.1017/s0885715600017723.

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The decomposition reactions of two zirconium hydroxide nitrates Zr(OH)2(NO3)2·(4+x)H2O and α-Zr(OH)2 (NO3)2·(1+x)H2O (0≤x≤1) have been studied by thermogravimetric analysis and high-temperature X-ray powder diffractometry (HTXRD), in nitrogen gas environment. The decomposition reaction sequences were clearly displayed by the HTXRD technique. They are different for the two precursors, except the formation of amorphous zirconia at low temperature (200 °C) and crystalline zirconia at about 390 °C. Three modifications of Zr(OH)2(NO3)2·H2O (α,β,γ) were identified. Their X-ray powder diffraction patterns were indexed by the successive dichotomy method. The unit cells are triclinic and present some parametric and volumetric similarities from each other and also with that of their precursor. Moreover, the thermal decomposition sequences of Zr(OH)2(NO3)2·(4+x)H2O and α-Zr(OH)2(NO3)2·(1+x)H2O include the formation of anhydrous oxide nitrate ZrO(NO3)2 and anhydrous hydroxide nitrate Zr(OH)2(NO3)2, respectively.

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7

Jiang, Wei Hui, Yan Hui Yang, Qing Xia Zhu y Jian Min Liu. "Iron-Zircon Pigments Prepared by Non-Hydrolytic Sol-Gel Method at Low Temperature". Advanced Materials Research 412 (noviembre de 2011): 223–26. http://dx.doi.org/10.4028/www.scientific.net/amr.412.223.

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ron-zircon pigment has been synthesized by non-hydrolytic sol-gel method using zirconium chloride and tetraethoxysilane as precursors, anhydrous ferric chloride as colorant, lithium fluoride as mineralizer and anhydrous ethanol as solvent. Iron-zircon pigment has been characterized by means of DTA-TG, XRD, Colorimeter and TEM. The results show that only a small fraction of iron is incorporated in the zircon crystal structure while the remaining iron cations are trapped within the zircon matrix. The iron-zircon with the red value (a*) of 20.64 can be synthesized at 700°C with the optimum Fe/Zr molar ratio of 0.2.

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Gilbert, Pupa U. P. A., Susannah M. Porter, Chang-Yu Sun, Shuhai Xiao, Brandt M. Gibson, Noa Shenkar y Andrew H. Knoll. "Biomineralization by particle attachment in early animals". Proceedings of the National Academy of Sciences 116, n.º 36 (19 de agosto de 2019): 17659–65. http://dx.doi.org/10.1073/pnas.1902273116.

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Crystallization by particle attachment (CPA) of amorphous precursors has been demonstrated in modern biomineralized skeletons across a broad phylogenetic range of animals. Precisely the same precursors, hydrated (ACC-H2O) and anhydrous calcium carbonate (ACC), have been observed spectromicroscopically in echinoderms, mollusks, and cnidarians, phyla drawn from the 3 major clades of eumetazoans. Scanning electron microscopy (SEM) here also shows evidence of CPA in tunicate chordates. This is surprising, as species in these clades have no common ancestor that formed a mineralized skeleton and appear to have evolved carbonate biomineralization independently millions of years after their late Neoproterozoic divergence. Here we correlate the occurrence of CPA from ACC precursor particles with nanoparticulate fabric and then use the latter to investigate the antiquity of the former. SEM images of early biominerals from Ediacaran and Cambrian shelly fossils show that these early calcifiers used attachment of ACC particles to form their biominerals. The convergent evolution of biomineral CPA may have been dictated by the same thermodynamics and kinetics as we observe today.

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Yosi, Kusuma Eriwati, Arsista Dede, Triaminingsih Siti y Sunarso. "Effect of CaSO₄Dissolution-Precipitation Time on Formation of Porous Carbonate Apatite as Bone Replacement Material". Journal of Biomimetics, Biomaterials and Biomedical Engineering 44 (febrero de 2020): 83–90. http://dx.doi.org/10.4028/www.scientific.net/jbbbe.44.83.

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Introduction: Carbonate apatite type B (C-Ap) has been used as a bone replacement material because of its osteoconductive properties. Clinically, the pores formed in bone replacement material aid in cell mobility and nutrient supply, thereby increasing the bone regeneration ability. CO32- ions found in this material are useful for maintaining a stable physiological environment in the bone in order for it to be easily absorbed by osteoclasts. Porous C-Ap type B is formed using the dissolution–precipitation method by immersing porous anhydrous CaSO4 in a mixture of carbonate and phosphate solutions. Purpose: The present study aimed to evaluate the effect of immersion ofCaSO4using the dissolution–precipitation method on the formation of porous C-Ap type B with calcium sulfate precursor hemihydrate. Method: Porous C-Ap type B was produced usinga mixture of calcium sulfate hemihydrate precursors with 50 wt% polymethylmethacrylate (PMMA) porogen and distilled water. After hardening, the calcium sulfate dihydrate containing PMMA was burned in an oven at 700°C for 4 h to remove the PMMA. The specimen was immersed in a mixture of sodium phosphate (Na3PO4) and sodium carbonate (Na2CO3) for 6, 12, and 24 h. Phase testing through X-ray diffraction (XRD) using CuKα radiation at 40 kV and 40 mA was performed. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR, Thermo Fisher Scientific, Waltham, Massachusetts, USA) was used for detecting the functional groups of CO32- and PO42-. Results: XRD results showed the formation of C-Ap at 6 and 12 h, but the anhydrous CaSO4 phase remained; alternatively, this phase was absent after 24 h of immersion phase andFTIR showed the presence of the functional groups of CO32- compounds. Conclusion: Porous C-Ap type B can be formed from CaSO4 precursors after 24 h of immersion using the dissolution–precipitation method.

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10

Nie, Xiaobo y Yanming Chen. "Observation of Dominant Nuclei and Magic-Sized CdS Nanoparticles in a Single-Phase System". Journal of Nanoscience and Nanotechnology 21, n.º 12 (1 de diciembre de 2021): 5987–92. http://dx.doi.org/10.1166/jnn.2021.19504.

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Cadmium sulfide nanoparticles (CdS NPs) were synthesized by using cadmium acetate and thiourea as precursors and sodium oleate as the surfactant under different cadmium acetate concentrations in anhydrous ethanol. Cadmium (Cd) precursor concentration greatly affected the nucleation-growth of CdS NPs. In extremely dilute solution with a Cd precursor concentration of 0.1 mmol · L−1, an overlapped nucleation and growth corresponding to two pronounced absorption peaks at 310 nm and 350 nm, respectively, was observed. Unparalleled nucleation was dominant within very long reaction time until 10 hours. The nuclei and the resulting magic-sized CdS NPs may be used as seeds to prepare size and shape controllable nanoparticles. On the contrary, at a high Cd precursor concentration (5 mmol · L−1), nucleation and growth were separated. Only one first exciton absorption peak standing for the growth of regular CdS NPs appeared at 440 nm. Many techniques including transmission electron microscopy (TEM), X-ray powder diffraction (XRD), ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectrometers were applied to characterize the morphology, crystalline structure, and optical properties of CdS NPs.

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11

Coppa, Nicholas, Daniel H. Nichols, John W. Schwegler, J. E. Crow, G. H. Myer y R. E. Salomon. "Preparation of YBa2Cu3O7−x precursors from a fused eutectic of sodium and potassium hydroxides". Journal of Materials Research 4, n.º 6 (diciembre de 1989): 1307–11. http://dx.doi.org/10.1557/jmr.1989.1307.

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A method for preparing YBa2Cu3O7−x from the simultaneous thermal decomposition of the nitrates of yttrium, barium, and copper in an anhydrous fused eutectic of sodium and potassium hydroxide is described. This method eliminates the need for any mechanical grinding or the introduction of carbon containing anions. Products formed are fine powders (∼1 μm) having mole ratios 1.00Y:2.00Ba:3.06Cu.X-ray diffraction analyses reveal that the initial products are Y(OH)3, BaO2, and CuO, which when air calcinated/oxygen annealed at 900–950 °C form the superconducting YBa2Cu3O7−x A mechanism is postulated for product formation as a function of reaction conditions.

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12

Guo, Da Gang, Han Yong y Ke Wei Xu. "Preparation and Characterization of a New Type of Sr-Contained Hydroxyapatite Bone Cement". Materials Science Forum 510-511 (marzo de 2006): 846–49. http://dx.doi.org/10.4028/www.scientific.net/msf.510-511.846.

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A novel route is developed to prepare a new type of Sr-contained hydroxyapatite bone cement. Tetracalcium phosphate, strontium hydrogen phosphate or anhydrous strontium chlorite, dicalcium phosphate, phosphoric and water are used as precursors. XRD, FTIR and EDXS are used to characterize the incorporation of 5% or 10% Sr2+ into the crystal lattice of hydroxyapatite. Results indicate that the Sr-contained CPC system of TTCP/DCPA/DSPA can set in 0.5M diluted phosphate acid with a final product of non-stoichiometric Sr-contained hydroxyapatite.

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13

Zhang, Wen-Qi, Liu-Ying Huang, Ai-Dong Li, Qi-Yue Shao y Di Wu. "CHEMICAL VAPOR DEPOSITION OF ZrxHf1-xO2 THIN FILMS USING ANHYDROUS MIXED-METAL NITRATES PRECURSORS". Integrated Ferroelectrics 97, n.º 1 (10 de junio de 2008): 93–102. http://dx.doi.org/10.1080/10584580802088835.

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14

Pathak, Madhvesh, Blassan Samuel, Kiran Tummalapalli, Prasanth Vuppalapati Giri, Rakesh Bohra y Kap Jin Kim. "Synthetic Studies and Structural Aspects of some Metallacyclic Derivatives of Titanium (IV) - Better Precursors for Titania". Advanced Materials Research 584 (octubre de 2012): 411–14. http://dx.doi.org/10.4028/www.scientific.net/amr.584.411.

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Titanium(IV) complexes of the type [(acac)2Ti(O-G-O] and [(acac)2Ti(OCH2CH2SH)2] {where G = (CH2)2, CH2CH(CH3), CH2CH(C2H5), CH(CH3)CH(CH3) have been synthesized in high yield by the interaction of the precursor [(acac)2Ti( OR)2] {where R = Pri , Et} with a variety of glycols and thioglycols in 1:1 and 1:2 molar ratios in refluxing benzene under anhydrous condition yield heteroleptic derivatives. On the basis of physico-chemical analyses, a cis-octahedral environment around Ti (IV) is proposed.

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15

Samfaß, Julia, Timo D. Stark y Thomas F. Hofmann. "Sensory-Directed Identification of Creaminess-Enhancing Semi-Volatile Lactones in Crumb Chocolate". Foods 10, n.º 7 (25 de junio de 2021): 1483. http://dx.doi.org/10.3390/foods10071483.

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In order to gain a more comprehensive knowledge of the chemical nature of creaminess-related flavor compounds in milk chocolates on a molecular level, crumb chocolate was analyzed by means of activity guided screening techniques. Sensory studies of a triglyceride-free lipid emulsion indicated that the n-pentane extract showed the highest impact regarding creaminess sensation. Enhancement of creaminess by adding anhydrous milk fat fractions to chocolate was demonstrated by fractionated high-vacuum distillation of different fats associated with the chocolate production combined with sensory experiments. Syntheses of various δ-lactones and the quantification of these sensory active semi-volatiles led to the conclusion that the anhydrous milk fat contains a series of γ- and δ-lactones. Cocoa butter revealed a high concentration of δ-hexadecalactone, too. Experiments suggested that lactones are generated from the potential precursors monohydroxyalkanoic acid(s) esterified (mono-tri)glyceride(s) during heating. Sensory studies exhibited recognition thresholds of 29–40 µmol/kg for the long-chain δ-lactones in crumb chocolate. Furthermore, significant enhancement of the retro-nasal creamy flavor was found for δ-tetradecalactone.

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16

Zhang, Rong Mei y Yu Xiu Zhao. "Synthesis of Mesostructured Materials of Different Heteroatoms and Their Catalytic Performances for Styrene Epoxidation". Advanced Materials Research 233-235 (mayo de 2011): 1507–10. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.1507.

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FeS-1, VS-1 or CuS-1 precursors are loaded and highly dispersed on the surface of mesoporous materials SBA-15, MCM-41 or SiO2by impregnating method. The samples were characterized by X-ray diffraction, FT-IR spectroscopy, TEM and N2adsorption. Their catalytic performances for styrene epoxidation with anhydrous TBHP as an oxidant agent were studied. The results suggest that zeolite primary and secondary building units are highly dispersed on the samples and the samples have still retained mesoporous structure. All of the catalysts exhibit good catalytic activities, producing styrene oxide and benzaldehyde as the main products. Cu/SBA-15 shows high activity and selectivity, which are comparable with that of other samples. We find that, under the conditions of preferable precursors,n(TBHP)/n(styrene) =1.5, reaction temperature 80°C, and reaction time 2.0h, the conversion and yield of styrene epoxide reached 65.9% and 42.2%, respectively.

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Morlens, S., N. Romà, S. Ricart, A. Pomar, T. Puig y X. Obradors. "Thickness control of solution deposited YBCO superconducting films by use of organic polymeric additives". Journal of Materials Research 22, n.º 8 (agosto de 2007): 2330–38. http://dx.doi.org/10.1557/jmr.2007.0296.

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We show that the thickness of yttrium–barium–copper–oxide (YBCO) superconducting films grown from trifluoroacetate precursors can be strongly modified using polymeric additives, while deposition conditions by spin or dip coating remain unchanged. A screening of different families of organic additives has been performed, and the best results have been achieved using polymers having an oxygen functionalized backbone. Two different polymeric additives, polyvinyl pyrrolidone (PVP) and poly(ethylene glycol) (PEG), have been more thoroughly investigated, and thermal analysis suggests that PEG is the most promising alternative because the pyrolysis step of the new complex precursors remains sharp and narrow and hence the final homogeneity of the film is preserved. The combination of anhydrous trifluoroacetic acid (TFA) solutions and poly(ethylene-glycol) (PEG8000) as additive can produce an increase of the YBCO film thickness up to 300%, while keeping a fast pyrolysis process and high critical current densities.

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Colombo, Daniel G., David C. Gilmer, Victor G. Young Jr., Stephen A. Campbell y Wayne L. Gladfelter. "Anhydrous Metal Nitrates as Volatile Single Source Precursors for the CVD of Metal Oxide Films". Chemical Vapor Deposition 04, n.º 06 (diciembre de 1998): 220–22. http://dx.doi.org/10.1002/(sici)1521-3862(199812)04:06<220::aid-cvde220>3.0.co;2-e.

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19

Sun, Chang-Yu, Cayla A. Stifler, Rajesh V. Chopdekar, Connor A. Schmidt, Ganesh Parida, Vanessa Schoeppler, Benjamin I. Fordyce et al. "From particle attachment to space-filling coral skeletons". Proceedings of the National Academy of Sciences 117, n.º 48 (13 de noviembre de 2020): 30159–70. http://dx.doi.org/10.1073/pnas.2012025117.

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Reef-building corals and their aragonite (CaCO3) skeletons support entire reef ecosystems, yet their formation mechanism is poorly understood. Here we used synchrotron spectromicroscopy to observe the nanoscale mineralogy of fresh, forming skeletons from six species spanning all reef-forming coral morphologies: Branching, encrusting, massive, and table. In all species, hydrated and anhydrous amorphous calcium carbonate nanoparticles were precursors for skeletal growth, as previously observed in a single species. The amorphous precursors here were observed in tissue, between tissue and skeleton, and at growth fronts of the skeleton, within a low-density nano- or microporous layer varying in thickness from 7 to 20 µm. Brunauer-Emmett-Teller measurements, however, indicated that the mature skeletons at the microscale were space-filling, comparable to single crystals of geologic aragonite. Nanoparticles alone can never fill space completely, thus ion-by-ion filling must be invoked to fill interstitial pores. Such ion-by-ion diffusion and attachment may occur from the supersaturated calcifying fluid known to exist in corals, or from a dense liquid precursor, observed in synthetic systems but never in biogenic ones. Concomitant particle attachment and ion-by-ion filling was previously observed in synthetic calcite rhombohedra, but never in aragonite pseudohexagonal prisms, synthetic or biogenic, as observed here. Models for biomineral growth, isotope incorporation, and coral skeletons’ resilience to ocean warming and acidification must take into account the dual formation mechanism, including particle attachment and ion-by-ion space filling.

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Kanakarajan, K., Karl Haider y Anthony W. Czarnik. "Nitrosations in Anhydrous Trifluoroacetic Acid Media: A Modification for Insoluble or Deactivated Amine and Amide Precursors". Synthesis 1988, n.º 07 (1988): 566–68. http://dx.doi.org/10.1055/s-1988-27643.

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Albéric, Marie, Cayla A. Stifler, Zhaoyong Zou, Chang-Yu Sun, Christopher E. Killian, Sergio Valencia, Mohamad-Assaad Mawass, Luca Bertinetti, Pupa U. P. A. Gilbert y Yael Politi. "Growth and regrowth of adult sea urchin spines involve hydrated and anhydrous amorphous calcium carbonate precursors". Journal of Structural Biology: X 1 (enero de 2019): 100004. http://dx.doi.org/10.1016/j.yjsbx.2019.100004.

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22

Chen, Liyi, Christian Hanisch y Bernhard Rieger. "Controllable Formation of MgCl2-based Spherical Catalyst Support Precursors via Composites of Liquid Inorganics and Polymers". Zeitschrift für Naturforschung B 64, n.º 5 (1 de mayo de 2009): 509–16. http://dx.doi.org/10.1515/znb-2009-0506.

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Anhydrous MgCl2 was reacted with 2 equiv. of ethanol to generate the MgCl2(EtOH)2 adduct 1. An appropriate amount of higher alcohol having a long carbon chain, such as 1-decanol, was anchored on the surface of a part of adduct 1 to give a mixture of MgCl2 adducts having an internal surfactant. A multifunctional polymer/oligomer, e. g. poly(ethylene glycol)-200 (PEG-200), was introduced into this system yielding a composite of liquid inorganics and polymers (CLIP). Under the regulation of the internal surfactant and the multifunctional polymer, this composite was melted and dispersed in an inert hydrocarbon solvent under vigorous agitation at elevated temperatures followed by fast cooling to generate a MgCl2-based spherical catalyst support precursor. SEM pictures show that this support precursor has a narrow particle size distribution, and its surface structure is an intricate combination of smaller MgCl2-based crystallites.

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Shao, Qi Yue, Ai Dong Li, Yan Dong, Feng Fang, Jian Qing Jiang y Zhi Guo Liu. "Chemical vapor deposition of ZrxTi1−xO2 and HfxTi1−xO2 thin films using the composite anhydrous nitrate precursors". Applied Surface Science 254, n.º 8 (febrero de 2008): 2224–28. http://dx.doi.org/10.1016/j.apsusc.2007.08.025.

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Wulfsberg, G., K. Shadid, B. Farris, J. Monn, T. Bonner, J. Yanisch y Al Weiss. "Dioxin Precursors: NQR Studies of Group 1 and Related 2,6-Dichlorophenolate and 2,4,6-Trichlorophenolate Salts". Zeitschrift für Naturforschung A 47, n.º 1-2 (1 de febrero de 1992): 153–59. http://dx.doi.org/10.1515/zna-1992-1-228.

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AbstractThe 81Br and 35Cl NQR spectra of anhydrous Group 1, tetraalkylammonium, and thallium(I) 2,6-dichlorophenolates, 2,4,6-trichlorophenolates, and 4-bromo-2,6-dichlorophenolates were searched for evidence of solid-state cation-organochlorine interactions that might, for example, be (in part) responsible for the difference in the thermal decomposition reactions of these salts (to give the supertoxic environmental pollutants, the polychlorinated dibenzodioxins) versus those of the corresponding Group 11 chlorophenolate complexes, which do not decompose to dioxins.For cations ranging in size from tetraethylammonium to potassium, the total range of 35Cl NQR frequencies in 2,6-dichlorophenolate and 2,4,6-trichlorophenolate salts is only 1.401 MHz, which, although larger than the 0.7 MHz range likely in molecular chlorocarbons, is smaller than in individual chlorophenolates of copper(I) and silver(I) (up to 2.0 MHz). In sodium and thallium(I) 2,4,6-trichlorophenolates substantially large frequency shifts (ca. 2.0 MHz) occur, to higher frequencies for the para-chlorines and lower frequencies for the ortho-chlorines (Na only). These disappear even in closely related compounds and show a pattern that seems unrelated to the decomposition products of the chlorophenolates.

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Góral-Kowalczyk, Małgorzata, Elżbieta Grządka, Jolanta Orzeł, Dariusz Góral, Tomasz Skrzypek, Zbigniew Kobus y Agnieszka Nawrocka. "Green Synthesis of Iron Nanoparticles Using an Aqueous Extract of Strawberry (Fragaria × ananassa Duchesne) Leaf Waste". Materials 17, n.º 11 (23 de mayo de 2024): 2515. http://dx.doi.org/10.3390/ma17112515.

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In this study, we analysed the potential use of dried strawberry leaves and calyces for the production of nanoparticles using inorganic iron compounds. We used the following iron precursors FeCl3 × 6H2O, FeCl2 × 4H2O, Fe(NO3)3 × 9H2O, Fe2(SO4)3 × H2O, FeSO4 × 7H2O, FeCl3 anhydrous. It was discovered that the content of polyphenols and flavonoids in dried strawberries and their antioxidant activity in DPPH and FRAP were 346.81 µM TE/1 g and 331.71 µM TE/1 g, respectively, and were similar to these of green tea extracts. Microimages made using TEM techniques allowed for the isolation of a few nanoparticles with dimensions ranging from tens of nanometres to several micrometres. The value of the electrokinetic potential in all samples was negative and ranged from −21,300 mV to −11,183 mV. XRF analyses confirmed the presence of iron ranging from 0.13% to 0.92% in the samples with a concentration of 0.01 mol/dm3. FT-IR spectra analyses showed bands characteristic of nanoparticles. In calorimetric measurements, no increase in temperature was observed in any of the tests during exposure to the electromagnetic field. In summary, using the extract from dried strawberry leaves and calyxes as a reagent, we can obtain iron nanoparticles with sizes dependent on the concentration of the precursor.

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Lamaa, Ghandy, David Suescum-Morales, António P. C. Duarte, Rui Vasco Silva y Jorge de Brito. "Optimising the Performance of CO2-Cured Alkali-Activated Aluminosilicate Industrial By-Products as Precursors". Materials 16, n.º 5 (25 de febrero de 2023): 1923. http://dx.doi.org/10.3390/ma16051923.

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Three industrial aluminosilicate wastes were studied as precursors to produce alkali-activated concrete: (i) electric arc furnace slag, (ii) municipal solid waste incineration bottom ashes, and (iii) waste glass rejects. These were characterized via X-ray diffraction and fluorescence, laser particle size distribution, thermogravimetric, and Fourier-transform infrared analyses. Distinctive combinations of anhydrous sodium hydroxide and sodium silicate solution were tried by varying the Na2O/binder ratio (8%, 10%, 12%, 14%) and SiO2/Na2O ratio (0, 0.5, 1.0, 1.5) to find the optimum solution for maximized mechanical performance. Specimens were produced and subjected to a three-step curing process: (1) 24 h thermal curing (70 °C), (2) followed by 21 days of dry curing in a climatic chamber (~21 °C, 65% RH), and (3) ending with a 7-day carbonation curing stage (5 ± 0.2% CO2; 65 ± 10% RH). Compressive and flexural strength tests were performed, to ascertain the mix with the best mechanical performance. The precursors showed reasonable bonding capabilities, thus suggesting some reactivity when alkali-activated due to the presence of amorphous phases. Mixes with slag and glass showed compressive strengths of almost 40 MPa. Most mixes required a higher Na2O/binder ratio for maximized performance, even though, contrary to expectations, the opposite was observed for the SiO2/Na2O ratio.

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Rumyantsev, R. N., A. A. Kournikova, A. A. Ilyin, A. V. Afineevsky, D. A. Prozorov, N. N. Smirnov, T. N. Borisova y E. S. Severgina. "INVESTIGATION OF THE CONDITIONS OF CERAMIC AND MECHANOCHEMICAL SYNTHESIS OF COMPOSITES CuO/ZnO/?-Al2O3". Steklo i Keramika, n.º 21 (septiembre de 2023): 22–32. http://dx.doi.org/10.14489/glc.2023.09.pp.022-032.

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In this work, using the methods of X-ray phase, X-ray diffraction, synchronous thermal analysis, scanning electron microscopy, low-temperature adsorption-desorption of nitrogen, the process of obtaining CuO/ZnO/?-Al2O3 composites, which can be used as the main component of catalysts for large-tonnage processes for methanol production and monoxide conversion, was studied. carbon. The influence of the method of preparation, the nature and intensity of processing on the phase composition of the resulting precursors and the physicochemical properties of the resulting composites was established. The processes occurring at the stage of mechanochemical activation of a mixture of anhydrous CuO/ZnO/?-Al2O3 oxides, a mixture of oxides with ammonium carbonate and ethanedienic acid have been studied. The optimal parameters for obtaining CuO/ZnO/?-Al2O3 composites with a developed specific surface area and porous structure have been determined.

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28

Ovdiichuk, Olga, Salla Lahdenpohja, Quentin Béen, Laurent Tanguy, Bertrand Kuhnast y Charlotte Collet-Defossez. "[18F]fluoride Activation and 18F-Labelling in Hydrous Conditions—Towards a Microfluidic Synthesis of PET Radiopharmaceuticals". Molecules 29, n.º 1 (26 de diciembre de 2023): 147. http://dx.doi.org/10.3390/molecules29010147.

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18F-labelled radiopharmaceuticals are indispensable in positron emission tomography. The critical step in the preparation of 18F-labelled tracers is the anhydrous F-18 nucleophilic substitution reaction, which involves [18F]F− anions generated in aqueous media by the cyclotron. For this, azeotropic drying by distillation is widely used in standard synthesisers, but microfluidic systems are often not compatible with such a process. To avoid this step, several methods compatible with aqueous media have been developed. We summarised the existing approaches and two of them have been studied in detail. [18F]fluoride elution efficiencies have been investigated under different conditions showing high 18F-recovery. Finally, a large scope of precursors has been assessed for radiochemical conversion, and these hydrous labelling techniques have shown their potential for tracer production using a microfluidic approach, more particularly compatible with iMiDEV™ cassette volumes.

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29

Mass, Tali, Anthony J. Giuffre, Chang-Yu Sun, Cayla A. Stifler, Matthew J. Frazier, Maayan Neder, Nobumichi Tamura, Camelia V. Stan, Matthew A. Marcus y Pupa U. P. A. Gilbert. "Amorphous calcium carbonate particles form coral skeletons". Proceedings of the National Academy of Sciences 114, n.º 37 (28 de agosto de 2017): E7670—E7678. http://dx.doi.org/10.1073/pnas.1707890114.

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Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.

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30

Jiang, Wei Hui, Qian Wu, Jian Min Liu, Qing Xia Zhu y Li Feng Miao. "Low Temperature Synthesis of Mullite Whisker by Nonhydrolytic Sol-Gel Process Combined with Molten Salt Method". Advanced Materials Research 538-541 (junio de 2012): 2346–49. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.2346.

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Using tetraethyl orthosilicate and anhydrous aluminum chloride as precursors, ethyl ether as oxygen donor, LiF as mineralizer, and Na2SO4-NaCl as compound molten salt, mullite whisker was synthesized in the low temperature by nonhydrolytic sol-gel process combined with molten salt method. The phase transformation of mixed powder composed of mullite xerogel and molten salt during the heat treatment and the microstructure of mullite whisker corresponding to different temperature were characterized by means of DTA-TG, XRD SEM and TEM. The results show that mullite crystal phase can be formed via non-hydrolytic sol-gel process combined with the molten salt method at 750°C. The synthetic effect of mullite get better as the temperature increased to 850°C, while NaAlSiO4 crystal phase is also detected. Mullite whisker, with diameters ranging from 300~500 nm and lengths of 3~5μm, is prepared at the temperature of 850°C.

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31

Perini, J. M., T. Marianne, J. J. Lafitte, G. Lamblin, P. Roussel y M. Mazzuca. "Use of an antiserum against deglycosylated human mucins for cellular localization of their peptide precursors: antigenic similarities between bronchial and intestinal mucins." Journal of Histochemistry & Cytochemistry 37, n.º 6 (junio de 1989): 869–75. http://dx.doi.org/10.1177/37.6.2470810.

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Highly glycosylated regions of mucins, or glycopeptides, were obtained by proteolysis of human bronchial mucins. They were deglycosylated by treatment with a trifluoromethane sulfonic acid/anisole mixture and subsequent solvolysis with anhydrous liquid hydrogen fluoride. The resulting peptides were then used to raise an immune serum in rabbit. This immune serum was used to localize the peptide precursors of human respiratory mucins within bronchial cells, using an immunohistochemical method. Two main patterns of labeling were observed in the goblet cells: the entire cytoplasm of some goblet cells was immunoreactive, whereas in other cells the labeling was concentrated around the nucleus. In the respiratory mucous glands, the labeling was localized around or below the nucleus. The serous cells were not stained. Similar labeling was observed in human colon goblet cells. This immune serum seems to be specific for mucin-secreting cells and has a strong affinity for the perinuclear region of these cells.

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32

Yang, L., H. H. Hng, T. Sun, H. Cheng y Jan Ma. "Synthesis of Nano-Sized Co-Sb Compounds through Solvothermal Routes". Solid State Phenomena 136 (febrero de 2008): 57–62. http://dx.doi.org/10.4028/www.scientific.net/ssp.136.57.

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Skutterudite materials have received great attention because their promising properties for thermoelectric (TE) applications. Among the family of skutterudites, CoSb3 has been intensively investigated due to its large electrical conductivity and Seebeck coefficient. However, its thermal conductivity is too high to make it an effective TE material. Nanostructuring of CoSb3 has the desirable effects of reducing its lattice thermal conductivity as the point imperfections or grain boundaries can scatter phonons (heat carrier) more effectively than electrons (charge carrier). In this study, nanostructured CoSb3 was synthesized by solvothermal routes using CoCl2·6H2O and SbCl3 as precursors dissolved in anhydrous ethanol with the reaction temperature kept at 240°C. In addition to the CoSb3 phase, other Co-Sb compounds were also formed during the reaction process. In this paper, we investigated the effects of processing parameters, such as concentration of CoCl2·6H2O, SbCl3 and NaBH4 in ethanol and thermal duration of solvothermal synthesis, on the yield of CoSb3 phase.

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Bao, Yi, Wei Hui Jiang, Guo Feng, Jian Min Liu y Qian Wu. "Low Temperature Preparation of Aluminum Titanate Film via Sol-Gel Method". Advanced Materials Research 936 (junio de 2014): 238–42. http://dx.doi.org/10.4028/www.scientific.net/amr.936.238.

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Aluminum titanate (Al2TiO5) film was prepared via sol-gel method at low temperature, using ethyl acetoacetate and anhydrous citric acid as compound chelating agent, tetrabutyl titanate (Ti (OC4H9)4) and aluminum chloride (AlCl3.6H2O) as precursors, ethanol as solvent. The phase transformation of Al2TiO5 xerogel during heat treatment, the effect of different chelating agents on the synthesis of Al2TiO5, and the phase composition and morphology of film were investigated by means of differential thermal and thermo gravimetric analysis (DTA-TG), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The results demonstrate that Al2TiO5 can be synthesized at 750 °C by using compound chelating agent, rather than single chelating agent. Compound chelating agent contributes to the formation of Al-O-Ti heterogeneous bond, which is the key to preparing Al2TiO5 at low temperature. High quality Al2TiO5 film could be coated on the SiC substract at 750°C.

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Fukami, Takanori, Shuta Tahara, Keiko Nakasone y Chitoshi Yasuda. "Synthesis, Crystal Structure, and Thermal Properties of CaSO4·2H2O Single Crystals". International Journal of Chemistry 7, n.º 2 (16 de julio de 2015): 12. http://dx.doi.org/10.5539/ijc.v7n2p12.

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Single crystals were grown at room temperature from the precursors CaCO3 and NH2SO3H by a gel method using agar-agar gel as the medium of growth. Differential scanning calorimetry, thermogravimetric–differential thermal analysis, and X-ray diffraction measurements were performed on the single crystals. The crystal structure of the grown crystals was confirmed to be very similar to that of calcium sulfate dihydrate (CaSO4·2H2O, gypsum). The temperature at which dehydration and evaporation of intercalated water molecules in the single crystal occurred was found to be 375.9 K, which was very close to that in CaSO4·2H2O. From all these results, we identified the grown single crystals as CaSO4·2H2O. The weight loss owing to the thermal decomposition of anhydrous CaSO4 formed by the dehydration of the single gypsum crystals was found to occur at ~1530 K. This weight loss was probably caused by the evolution of SO3 gas by sublimation, and the chalky white substance left in the open vessel after decomposition was calcium oxide (CaO).

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35

Ma, Jie y Qingsheng Wu. "A novel additive-free oxides–hydrothermal approach for monazite-type LaPO4nanomaterials with controllable morphologies". Journal of Applied Crystallography 43, n.º 5 (10 de septiembre de 2010): 990–97. http://dx.doi.org/10.1107/s0021889810031894.

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A facile oxides–hydrothermal (O–HT) method is demonstrated to prepare high-purity monazite-type LaPO4nanomaterials. In this approach, La2O3and P2O5powder are first directly used as precursors under additive-free hydrothermal conditions. The as-prepared samples are characterized with X-ray diffraction, Fourier transform IR spectroscopy, thermogravimetry, scanning electron microscopy, transmission electron microscopy (high-resolution TEM, energy dispersive spectroscopy) and selected-area electron diffraction. The typical sample obtained at 433 K in 24 h comprises uniform single-crystal nanofibres with a diameter of ∼15–28 nm and an aspect ratio of 30–50. The influences of treatment time, synthesis temperature and P/La molar ratio are investigated. The phase transition from hexagonal hydrate to monoclinic anhydrous lanthanum phosphate and the growth process of nanofibres are revealed by the experimental results. The formation mechanism of the monoclinic LaPO4is discussed. The result indicates that the P/La ratio does not influence the composition and crystal phase but changes the morphology of the product in the O–HT system.

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WEI, Guohua, Chao CAI y Yuguo DU. "Highly Efficient and Versatile Synthesis of Some Important Precursors from 1,6-Anhydrous-β-D-glucopyranose as a Green Starting Material". Chinese Journal of Chemistry 27, n.º 8 (agosto de 2009): 1589–92. http://dx.doi.org/10.1002/cjoc.200990268.

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Sun, William, Cheryl Falzon, Ebrahim Naimi, Ali Akbari, Leonard I. Wiebe, Manju Tandon y Piyush Kumar. "Synthesis of [18F]FAZA Using Nosyl and Iodo Precursors for Nucleophilic Radiofluorination". Current Radiopharmaceuticals 12, n.º 1 (4 de marzo de 2019): 49–57. http://dx.doi.org/10.2174/1874471011666181019105947.

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Background: 1-α-D-(5-Deoxy-5-[18F]fluoroarabinofuranosyl)-2-nitroimidazole ([18F]FAZA) is manufactured by nucleophilic radiofluorination of 1-α-D-(2’,3’-di-O-acetyl-5’-O-toluenesulfonylarabinofuranosyl)- 2-nitroimidazole (DiAcTosAZA) and alkaline deprotection to afford [18F]FAZA. High yields (>60%) under optimized conditions frequently revert to low yields (<20%) in large scale, automated syntheses. Competing side reactions and concomitant complex reaction mixtures contribute to substantial loss of product during HPLC clean-up. Objective: To develop alternative precursors for facile routine clinical manufacture of [18F]FAZA that are compatible with current equipment and automated procedures. Methods: Two new precursors, 1-α-D-(2’,3’-di-O-acetyl-5’-O-(4-nitrobenzene)sulfonyl-arabinofuranosyl)-2- nitroimidazole (DiAcNosAZA) and 1-α-D-(2’,3’-di-O-acetyl-5’-iodo-arabinofuranosyl)-2-nitroimidazole (DiAcIAZA), were synthesized from commercially-available 1-α-D-arabinofuranosyl-2-nitroimidazole (AZA). A commercial automated synthesis unit (ASU) was used to condition F-18 for anhydrous radiofluorination, and to radiofluorinate DiAcNosAZA and DiAcIAZA using the local standardized protocol to manufacture [18F]FAZA from AcTosAZA. Results: DiAcNosAZA was synthesized via two pathways, in recovered yields of 29% and 40%, respectively. The nosylation of 1-α-D-(2’,3’-di-O-acetyl-arabinofuranosyl)-2-nitroimidazole (DiAcAZA) featured a strong competing reaction that afforded 1-α-D-(2’,3’-di-O-acetyl-5’-chloro-arabinofuranosyl)-2- nitroimidazole (DiAcClAZA) in 55% yield. Radiofluorination yields were better from DiAcNosAZA and DiAcIAZA than from DiAcTosAZA, and the presence of fewer side products afforded higher purity [18F]FAZA preparations. Several radioactive and non-radioactive by products of radiofluorination were assigned tentative chemical structures based on co-chromatography with authentic reference compounds. Conclusion: DiAcClAZA, a major side-product in the preparation of DiAcNosAZA, and its deprotected analogue (ClAZA), are unproven hypoxic tissue radiosensitizers. DiAcNosAZA and DiAcIAZA provided good radiofluorination yields in comparison to AcTosAZA and could become preferred [18F]FAZA precursors if the cleaner reactions can be exploited to bypass HPLC purification.

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Jiang, Wei Hui, Qi Ming Jiang, Jian Min Liu, Qing Xia Zhu y Quan Zhang. "Prepartion of Stabilized Aluminum Titanate Film via Nonhydrolytic Sol-Gel Route". Advanced Materials Research 538-541 (junio de 2012): 96–100. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.96.

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The stabilized aluminum titanate (Al2TiO5) film was coated on the silicon carbide (SiC) substrate via nonhydrolytic sol-gel method (NHSG), using anhydrous aluminum chloride and titanium tetrachloride as precursors, ethanol as oxygen donor, different iron sources as stabilizers, and dimethyl mixed dibasic acid (DBE) with the characteristic of environmental protection and high boiling point as solvent. The phase transformation of modified Al2TiO5 xerogel during heat treatment, the effect of different iron stabilizers on the stabilization of Al2TiO5 film, and the influence of the coating process parameters on film-forming quality were investigated by means of DTA/TG, XRD and SEM. The results indicate that ethanol iron as the stabilizer, Al2TiO5 crystal phase can be formed at 750°C. While the temperature is raised further to 1000°C, Al2TiO5 is stable without decomposition, and has better synthesis effect. Selecting iron chloride, iron sulfate and iron ethanol as stabilizers respectively, only iron ethanol is effective to thermal stability of Al2TiO5 film. The best optimal vertical sliding velocity is 3.75 mm/s.

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Sroor, Farid M., Phil Liebing, Cristian G. Hrib, Daniel Gräsing, Liane Hilfert y Frank T. Edelmann. "Formation and structure of the first metal complexes comprising amidinoguanidinate ligands". Acta Crystallographica Section E Crystallographic Communications 72, n.º 11 (4 de octubre de 2016): 1526–31. http://dx.doi.org/10.1107/s2056989016015322.

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The first metal complexes comprising amidinoguanidinate ligands have been prepared and structurally characterized, namely bis[μ-N,N′,N′′,N′′′-tetraisopropyl-1-(1-butylamidinato)guanidinato-κ3N1,N2:N2]bis[(tetrahydrofuran)lithium], [Li2(C18H37N4)2(C4H8O)2], (2), and [bis(tetrahydrofuran)lithium]-di-μ-chlorido-{(N,N′-dicyclohexyl-1-butylamidinato-κ2N1,N2)[N,N′,N′′,N′′′-tetracyclohexyl-1-(1-butylamidinato)guanidinato-κ2N1,N2]holmate(III)}, [HoLiCl2(C4H8O)2(C17H31N2)(C30H53N4)], (3). The novel lithium amidinoguanidinate precursors Li[nBuC(=NR)(NR)C(NR)2] [1:R= Cy (cyclohexyl),2:R=iPr) were obtained by treatment ofN,N′-diorganocarbodiimides,R—N=C=N—R(R=iPr, Cy), with 0.5 equivalents ofn-butyllithium under well-defined reaction conditions. An X-ray diffraction study of2revealed a ladder-type dimeric structure in the solid state. Reaction of anhydrous holmium(III) chloride within situ-prepared2afforded the unexpected holmium `ate' complex [nBuC(=NCy)(NCy)C(NCy)2]Ho[nBuC(NCy)2](μ-Cl)2Li(THF)2(3) in 71% yield. An X-ray crystal structure determination of3showed that this complex contains both an amidinate ligand and the new amidinoguanidinate ligand.

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40

Jiang, Wei Hui, Si Cheng, Qing Xia Zhu y Jian Min Liu. "Effects of Solvents on Synthesis and Dispersion of Zircon Powder via Non-Hydrolytic Sol-Gel Route". Key Engineering Materials 512-515 (junio de 2012): 54–58. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.54.

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Zircon nano–powder has been synthesized via the non-hydrolytic sol–gel route, using industral zirconium tetrachloride (ZrCl4) and tetraethoxysilane (TEOS) as precursors, lithium fluoride (LiF) as mineralizer, PEG1000 as dispersant. The effects of solvents on the synthesis and dispersion of zircon nano-powder were investigated by means of XRD and TEM. The results indicate that the aprotic solvent N, N-dimethyl formamide (DMF) is not conducive to the nucleophilic substitution reaction, which directly affect the zircon synthesis, and the particles are easy to agglomerate due to the large surface tension; the powder with size of 30nm and good dispersion can be obtained using dichloromethane (CH2Cl2) as solvent; different anhydrous alcohols as solvents influence zircon synthesis, the order of the synthesis ratio is listed as EtOH›propanol (PrOH)› isopropanol (PriOH). Powder particles are larger than 50nm with wide distribution and serious agglomeration when taking PrOH and PriOH as solvents. Nano-zircon with good dispersion and synthesis ratio up to 94.5% can be obtained via using ethanol as solvent.

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Ning, Keke, Guoqiang Xiang, Cuicui Wang, Jingxing Wang, Xiaohong Qiao, Ruofei Zhang, Xiuming Jiang, Lijun He y Wenjie Zhao. "UV-emitting polyelectrolyte-modified MoS2 quantum dots for selective determination of nitrophenol in water samples based on inner filter effect". Canadian Journal of Chemistry 98, n.º 5 (mayo de 2020): 222–27. http://dx.doi.org/10.1139/cjc-2019-0425.

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In this work, poly(sodium 4-styrenesulfonate) (PSS) modified molybdenum disulfide quantum dots (MoS2-PSS QDs) were synthesized via a simple hydrothermal method using l-cysteine and anhydrous sodium molybdate as precursors and PSS as a modification reagent, and a selective and sensitive fluorescent sensing method for the determination of p-nitrophenol (p-NP) based on their UV emission was developed. The obtained MoS2-PSS QDs have an obvious UV emission peak (390 nm) with quantum yield of 5.13%. The strong absorption peak of p-NP at 400 nm has large spectral overlap with the UV emission peak (390 nm) of MoS2-PSS QDs. Because of this p-NP absorption, the fluorescence of MoS2-PSS QDs at 390 nm is quenched with the introduction of p-NP via the inner filter effect (IFE) and the decreased fluorescence intensity was linearly proportional to the p-NP concentration in the range of 1–20 μmol/L, leading to a detection limit of 0.13 μmol/L for p-NP. The MoS2 QDs-based fluorescent probe for p-NP is sensitive and selective and was successfully applied in the determination of p-NP in the pond water samples with satisfactory results.

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42

Sokol, Ella, Svetlana Kokh, Victor Sharygin, Victoria Danilovsky, Yurii Seryotkin, Ruslan Liferovich, Anna Deviatiiarova, Elena Nigmatulina y Nikolay Karmanov. "Mineralogical Diversity of Ca2SiO4-Bearing Combustion Metamorphic Rocks in the Hatrurim Basin: Implications for Storage and Partitioning of Elements in Oil Shale Clinkering". Minerals 9, n.º 8 (30 de julio de 2019): 465. http://dx.doi.org/10.3390/min9080465.

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This is the first attempt to provide a general mineralogical and geochemical survey of natural Ca2SiO4-bearing combustion metamorphic (CM) rocks produced by annealing and decarbonation of bioproductive Maastrichtian oil shales in the Hatrurim Basin (Negev Desert, Israel). We present a synthesis of data collected for fifteen years on thirty nine minerals existing as fairly large grains suitable for analytical examination. The Hatrurim Ca2SiO4-bearing CM rocks, which are natural analogs of industrial cement clinker, have been studied comprehensively, with a focus on several key issues: major- and trace-element compositions of the rocks and their sedimentary precursors; mineral chemistry of rock-forming phases; accessory mineralogy; incorporation of heavy metals and other trace elements into different phases of clinker-like natural assemblages; role of trace elements in stabilization/destabilization of Ca2SiO4 polymorphic modifications; mineralogical diversity of Ca2SiO4-bearing CM rocks and trace element partitioning during high-temperature–low-pressure anhydrous sintering. The reported results have implications for mineral formation and element partitioning during high-temperature–low-pressure combustion metamorphism of trace element-loaded bituminous marine chalky sediments (“oil shales”) as well as for the joint effect of multiple elements on the properties and hydration behavior of crystalline phases in industrial cement clinkers.

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Osińska, K., M. Płońska y A. Marzec. "Application of the Sol-Gel Method at the Fabrication of PLZT:Yb3+ Ceramics". Archives of Metallurgy and Materials 61, n.º 3 (1 de septiembre de 2016): 1441–46. http://dx.doi.org/10.1515/amm-2016-0236.

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Abstract The aim of presented study was to obtain the PLZT:Yb3+ ceramics. Nanopowders of itterbium doped PLZT materials were synthesized by the sol-gel method from high quality metaloorganic precursors, as lead (II) acetate, lanthanum acetate, ytterbium acetate, zirconium (IV) propoxide and titanium (IV) propoxide. Anhydrous acetic acid and n-propyl alcohol were used as solvents, while acetyloacetone was added as stabilizer of hydrolysis reactions. Thermal evolution of the dried gels, before and after calcination, was studied by the simultaneous thermal analysis. The amorphous PLZT:Yb3+ gels were first calcined in the furnace at T = 850°C, and then mixed in the planetary ball mill. Additionally, the mean particle sizes were calculated by means of powder specific surface area measurements, based on the BET physical adsorption isotherm. Such obtained powders were subsequently pressed into pellets, and sintered by the free sintering method at temperature T = 1250°C / 6h. The morphology of fabricated PLZT:Yb3+ ceramic powders and samples was studied using Scanning Electron Microscopy. Chemical characterization of samples was carried on using the Energy-dispersive X-ray spectroscopy - EDS system. Studies provided detailed data concerning the relationships between doping and preparing conditions on the basic physical and chemical properties of obtained ceramic materials.

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Nosrati, Hassan, Rasoul Sarraf-Mamoory, Amir Hossein Ahmadi y Maria Canillas Perez. "Synthesis of Graphene Nanoribbons–Hydroxyapatite Nanocomposite Applicable in Biomedicine and Theranostics". Journal of Nanotheranostics 1, n.º 1 (22 de abril de 2020): 6–18. http://dx.doi.org/10.3390/jnt1010002.

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In order to investigate the effect of graphene nanoribbons on the final properties of hydroxyapatite-based nanocomposites, a solvothermal method was used at 180 °C and 5 h for the synthesis of graphene nanoribbons–hydroxyapatite nanopowders by employing hydrogen gas injection. Calcium nitrate tetrahydrate and diammonium hydrogenphosphate were used as calcium and phosphate precursors, respectively. To synthesize the powders, a solvent containing diethylene glycol, anhydrous ethanol, dimethylformamide, and water was used. Graphene oxide nanoribbons were synthesized by chemical unzipping of carbon nanotubes under oxidative conditions. The synthesized powders were consolidated by spark plasma sintering methodat 950 °C and a pressure of 50 MPa. The powders and sintered samples were then evaluated using X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, Vickers microindentation techniques, and biocompatibility assay. The findings of this study showed that the final powders synthesized by the solvothermal method had calcium to phosphate ratio of about 1.67. By adding a small amount of graphene nanoribbon (0.5%W), elastic modulus and hardness of hydroxyapatite increased dramatically. In biological experiments, the difference of hydroxyapatite effect in comparison with the nanocomposite was not significant. The findings of this study showed that graphene nanoribbons have a positive effect on the properties of hydroxyapatite, and these findings would be useful for the medical and theranostic application of this type of nanocomposites.

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Taborda-Barraza, Madeleing, Francine Padilha, Laura Silvestro, Afonso Rangel Garcez de Azevedo y Philippe Jean Paul Gleize. "Evaluation of CNTs and SiC Whiskers Effect on the Rheology and Mechanical Performance of Metakaolin-Based Geopolymers". Materials 15, n.º 17 (2 de septiembre de 2022): 6099. http://dx.doi.org/10.3390/ma15176099.

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Despite geopolymers having emerged as a more sustainable alternative to Portland cement, their rheological properties still need to be thoroughly investigated, aiming at the material’s applicability. Additionally, studies that evaluated the fresh state of geopolymer composites with nanomaterials are scarce. Thus, two metakaolin-based geopolymer systems were reinforced with nanomaterials with a similar geometry: carbon nanotubes (CNT) and silicon carbide whiskers (SCW). The nanomaterials incorporation was assessed by rotational rheometry (conducted up to 110 min), isothermal calorimetry, compressive strength after 7 and 28 days, and the microstructure was investigated using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). CNT and SCW incorporation (0.20 wt.%) did not significantly affect the yield stress and viscosity of the R2-group (based on metakaolin type 2), while increasing the rheological parameters up to 56.0% for the R1-group (based on metakaolin type 1). Both additions modified the reaction kinetics. Increments of up to 40.7% were observed in the compressive strength of geopolymer pastes with the incorporation of a SCW content of 0.2 wt.%. XRD and FTIR results suggest similar structural modifications between precursors. Nevertheless, R2 showed substantial transformations while the R1 group exhibited anhydrous material that can react over time. Overall, incorporating CNT and SCW contributed to higher mechanical increments on systems with average mechanical strength (R1) compared to systems with higher potential mechanical performance (R2).

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Shinde, Sandip S., Kim-Viktoria Bolik, Simone Maschauer y Olaf Prante. "18F-Fluorination Using Tri-Tert-Butanol Ammonium Iodide as Phase-Transfer Catalyst: An Alternative Minimalist Approach". Pharmaceuticals 14, n.º 9 (24 de agosto de 2021): 833. http://dx.doi.org/10.3390/ph14090833.

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The 18F syntheses of tracers for positron emission tomography (PET) typically require several steps, including extraction of [18F]fluoride from H2[18O]O, elution, and drying, prior to nucleophilic substitution reaction, being a laborious and time-consuming process. The elution of [18F]fluoride is commonly achieved by phase transfer catalysts (PTC) in aqueous solution, which makes azeotropic drying indispensable. The ideal PTC is characterized by a slightly basic nature, its capacity to elute [18F]fluoride with anhydrous solvents, and its efficient complex formation with [18F]fluoride during subsequent labeling. Herein, we developed tri-(tert-butanol)-methylammonium iodide (TBMA-I), a quaternary ammonium salt serving as the PTC for 18F-fluorination reactions. The favorable elution efficiency of [18F]fluoride using TBMA-I was demonstrated with aprotic and protic solvents, maintaining high 18F-recoveries of 96–99%. 18F-labeling reactions using TBMA-I as PTC were studied with aliphatic 1,3-ditosylpropane and aryl pinacol boronate esters as precursors, providing 18F-labeled products in moderate-to-high radiochemical yields. TBMA-I revealed adequate properties for application to 18F-fluorination reactions and could be used for elution of [18F]fluoride with MeOH, omitting an additional base and azeotropic drying prior to 18F-labeling. We speculate that the tert-alcohol functionality of TBMA-I promotes intermolecular hydrogen bonding, which enhances the elution efficiency and stability of [18F]fluoride during nucleophilic 18F-fluorination.

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Gradeff, Peter S., Kenan Yunlu, Timothy J. Deming, Jeffrey M. Olofson, Robert J. Doedens y William J. Evans. "Synthesis of yttrium and lanthanide silyloxy complexes from anhydrous nitrate and oxo alkoxide precursors and the x-ray crystal structure of [Ce(OSiPh3)3(THF)3](THF)". Inorganic Chemistry 29, n.º 3 (febrero de 1990): 420–24. http://dx.doi.org/10.1021/ic00328a016.

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Koverda, Anna A., Alexandra I. Korshunova, Mikhail N. Koverda y Evgeny N. Sechin. "Synthesis of monomers for the preparation of optically active poly(amido–imide)s. Part 1. Synthesis of chiral imides containing a fragment of the natural amino acid based on nitrophenylcycloalkanedicarboxylic acids". Butlerov Communications 57, n.º 1 (31 de enero de 2019): 27–40. http://dx.doi.org/10.37952/roi-jbc-01/19-57-1-27.

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Previously it was shown that the stereochemical result of the alkylation reaction of benzene with cycloalkanedicarboxylic acids depends on the order of mixing the reagents. The resulting diastereomerically pure derivatives can be used as precursors of monomers for the synthesis of optically active poly(amido–imide)s, which are basic materials in chiral chromatographic separation. Their potential for use in chiral catalytic systems, liquid crystals in ferroelectric and nonlinear optics, in the manufacture of electrodes for enantioselective recognition during bioelectrosynthesis, membrane separation technology, etc. is shown. Nitration reactions of alkyl derivatives were carried out with their subsequent imidization with natural amino acids. The resulting diastereomerically pure dicarboxylic acids are nitrated with low selectivity, unlike their anhydrides, so the nitro derivatives were synthesized by nitrating the anhydrides with anhydrous nitric acid in chloroform solution. The racemization of the α-carbon center of the amino acid fragment occurs during the imidization reaction in glacial acetic acid. Using of DMF as a solvent under mild conditions is preferable, as it eliminates the possibility of racemization of the chiral center of the amino acid fragment. It was also found that during the preparation of imides, the configuration of the chiral centers of the cycloalkane dicarboxylic acid fragment is preserved. Nitrophenylnorbornanedicarboxylic acid forms an anhydride directly during synthesis in acetic acid, unlike cyclohexanedicarboxylic acids, due to its spatial structure. Nitrophenylnorbornanedicarboxylic acid is also characterized by easier imidization. The structure was determined using 1H, 13C NMR, 1H-1H NOESY, 1H-1H COSY, HPLC, capillary electrophoresis.

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Rabiei, Khadijeh y Hossein Naeimi. "Sonocatalyzed Total Synthesis of N,N-diaryl-formamides Through Oxidation and Hydrolysis Reaction of gem-dichloroaziridines using DMSO/H2O". Current Organic Synthesis 15, n.º 7 (16 de octubre de 2018): 1014–19. http://dx.doi.org/10.2174/1570179415666180622122930.

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Background:.Aziridine compounds are among the most fascinating intermediates in organic synthesis, acting as precursors of many complex molecules due to the strain incorporated in their skeletons and can be opened in a stereo controlled manner with various nucleophiles, providing access to a wide range of important nitrogen-containing products. Sonochemistry involves the use of ultrasound technique to promote organic reactions. In recent years sonochemistry has been widely used in organic syntheses as it offers a versatile and facile pathway for a bewildering range of organic reactions. Materials and Method: The synthesis of some Schiff bases was done in according the previously reported procedure in literature. The synthesized Schiff bases in the presence of magnesium powder and CCl4 in anhydrous tetrahydrofuran was converted to gem-dichloroaziridines at ultrasonic irradiation. Finally, the synthesized 2,2- dichloro-1,3-bis(4-chlorophenyl) aziridine was treated with DMSO and H2O with ultrasonic irradiation to produce the N-(4-chlorophenyl)-N-[4-(chlorophenyl)hydroxy-methyl] formamides. Results: Here, total synthesis of N-(α-hydroxybenzyl)-formamides through ultrasonic promoted oxidation and hydrolysis reaction of gem-dichloroaziridine derivatives in the presence of dimethyl sulfoxide and water has been investigated. Conclusion: In this study, ultrasonic promoted oxidation and hydrolysis of gem-dichloroaziridines toward N- (α-hydroxybenzyl)-formamides in the presence of DMSO and H2O under neutral medium reaction conditions has been reported. Excellent yields of products were obtained through this method. Other advantages of this reaction are short reaction times, simplicity of the method and high purity of products.

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Carl, Frederike, Leonie Birk, Bettina Grauel, Monica Pons, Christian Würth, Ute Resch-Genger y Markus Haase. "LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals". Nano Research 14, n.º 3 (16 de octubre de 2020): 797–806. http://dx.doi.org/10.1007/s12274-020-3116-y.

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AbstractWe developed a procedure to prepare luminescent LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF4:Yb (Yb:YLF) and LiYF4:Yb,Er (Yb,Er:YLF) with identical doping concentrations. As the luminescence decay times of Yb3+ and Er3+ are known to be very sensitive to the presence of quenchers, the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell interfaces. This improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based synthesis. First, the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF4 shell material. Second, anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH− in the crystal lattice, known to quench the emission of Yb3+ ions. Excitation power density (P)-dependent absolute measurements of the upconversion luminescence quantum yield (ΦUC) of LiYF4:Yb,Er/LiYF4 core/shell particles reveal a maximum value of 1.25% at P of 180 Wcm−2. Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes, these ΦUC values are the highest reported so far for LiYF4:18%Yb,2%Er/LiYF4 nanocrystals without additional dopants. Further improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF4 nanocrystals.

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