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Keywords = proto-vaterite ACC

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12 pages, 2736 KB  
Communication
The Crystallization Process of Vaterite Microdisc Mesocrystals via Proto-Vaterite Amorphous Calcium Carbonate Characterized by Cryo-X-ray Absorption Spectroscopy
by Li Qiao, Ivo Zizak, Paul Zaslansky and Yurong Ma
Crystals 2020, 10(9), 750; https://doi.org/10.3390/cryst10090750 - 26 Aug 2020
Cited by 12 | Viewed by 4383
Abstract
Investigation on the formation mechanism of crystals via amorphous precursors has attracted a lot of interests in the last years. The formation mechanism of thermodynamically meta-stable vaterite in pure alcohols in the absence of any additive is less known. Herein, the crystallization process [...] Read more.
Investigation on the formation mechanism of crystals via amorphous precursors has attracted a lot of interests in the last years. The formation mechanism of thermodynamically meta-stable vaterite in pure alcohols in the absence of any additive is less known. Herein, the crystallization process of vaterite microdisc mesocrystals via proto-vaterite amorphous calcium carbonate (ACC) in isopropanol was tracked by using Ca K-edge X-ray absorption spectroscopy (XAS) characterization under cryo-condition. Ca K-edge X-ray absorption near edge structure (XANES) spectra show that the absorption edges of the Ca ions of the vaterite samples with different crystallization times shift to lower photoelectron energy while increasing the crystallization times from 0.5 to 20 d, indicating the increase of crystallinity degree of calcium carbonate. Ca K-edge extended X-ray absorption fine structure (EXAFS) spectra exhibit that the coordination number of the nearest neighbor atom O around Ca increases slowly with the increase of crystallization time and tends to be stable as 4.3 (±1.4). Crystallization time dependent XANES and EXAFS analyses indicate that short-range ordered structure in proto-vaterite ACC gradually transform to long-range ordered structure in vaterite microdisc mesocrystals via a non-classical crystallization mechanism. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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13 pages, 4279 KB  
Article
Functionalized Multiwalled CNTs in Classical and Nonclassical CaCO3 Crystallization
by Andrónico Neira-Carrillo, Patricio Vásquez-Quitral, Marianela Sánchez, Masoud Farhadi-Khouzani, Héctor Aguilar-Bolados, Mehrdad Yazdani-Pedram and Helmut Cölfen
Nanomaterials 2019, 9(8), 1169; https://doi.org/10.3390/nano9081169 - 15 Aug 2019
Cited by 12 | Viewed by 4224
Abstract
Multiwalled carbon nanotubes (MWCNTs) are interesting high-tech nanomaterials. MWCNTs oxidized and functionalized with itaconic acid and monomethylitaconate were demonstrated to be efficient additives for controlling nucleation of calcium carbonate (CaCO3) via gas diffusion (GD) in classical as well as nonclassical crystallization, [...] Read more.
Multiwalled carbon nanotubes (MWCNTs) are interesting high-tech nanomaterials. MWCNTs oxidized and functionalized with itaconic acid and monomethylitaconate were demonstrated to be efficient additives for controlling nucleation of calcium carbonate (CaCO3) via gas diffusion (GD) in classical as well as nonclassical crystallization, yielding aragonite and truncated calcite. For the first time, all amorphous calcium carbonate (ACC) proto-structures, such as proto calcite-ACC, proto vaterite-ACC and proto aragonite-ACC, were synthesized via prenucleation cluster (PNC) intermediates and stabilized at room temperature. The MWCNTs also showed concentration-dependent nucleation promotion and inhibition similar to biomolecules in nature. Incorporation of fluorescein-5-thiosemicarbazide (5-FTSC) dye-labeled MWCNTs into the CaCO3 lattice resulted in fluorescent hybrid nanosized CaCO3. We demonstrate that functionalized MWCNTs offer a good alternative for controlled selective crystallization and for understanding an inorganic mineralization process. Full article
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15 pages, 9446 KB  
Article
Effect of Alginate from Chilean Lessonia nigrescens and MWCNTs on CaCO3 Crystallization by Classical and Non-Classical Methods
by Marianela Sánchez, Patricio Vásquez-Quitral, Nicole Butto, Felipe Díaz-Soler, Mehrdad Yazdani-Pedram, Juan Francisco Silva and Andrónico Neira-Carrillo
Crystals 2018, 8(2), 69; https://doi.org/10.3390/cryst8020069 - 31 Jan 2018
Cited by 9 | Viewed by 4902
Abstract
In our crystallization experiments, the influence of alginate from Chilean Lessonia nigrescens and functionalized multi-walled carbon nanotubes (MWCNTs) was tested through electrocrystallization (EC) and gas diffusion (GD) methods on the crystal growth of calcium carbonate (CaCO3) and their possible stabilization of [...] Read more.
In our crystallization experiments, the influence of alginate from Chilean Lessonia nigrescens and functionalized multi-walled carbon nanotubes (MWCNTs) was tested through electrocrystallization (EC) and gas diffusion (GD) methods on the crystal growth of calcium carbonate (CaCO3) and their possible stabilization of proto-structures in amorphous CaCO3 (ACC) state through pre-nucleation clusters (PNC) essays with automatic potentiometric titrations were performed. CaCO3 crystals obtained in the in vitro above-mentioned crystallization systems were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and powder X-ray diffractometer (XRD). Our experimental findings showed that ALG and functionalized MWCNTs stabilized truncated and agglomerated vaterite-like particles through GD and EC methods. While, on the other hand, we obtained qualitative information about induction or inhibition of CaCO3 nucleation that was provided by potentiometric titrations. Full article
(This article belongs to the Special Issue Carbonates)
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