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Porous Amorphous Calcium Carbonate and Phosphate: Synthesis and Application
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The synthesis of porous amorphous calcium carbonate (ACC) and porous amorphous calcium phosphate (ACP) was developed in this thesis. Porous ACC with specific Brunauer–Emmett–Teller (BET) surface area of >350 m2/g was synthesized using a surfactant free approach. The high surface area of porous ACC was related to its nanostructure. Porous ACC was constructed with aggregated ACC nanoparticles that were less than 10 nm in diameter. The porosity and stability of porous ACC could be enhanced by introducing additives in the synthesis steps. The use of additives could also be used to control the crystallization of ACC to form vaterite particles with controllable morphologies. Porous ACC was tested as a drug carrier for two poorly soluble drugs (itraconazole and celecoxib). The porous ACC carrier was able to stabilize these drugs in their amorphous forms and enhance their release rate significantly when compared with the crystalline drug. Furthermore, porous ACC could also be used as a precursor/template for the synthesis of porous carbon. A porous carbon adsorbent with high uptake and high selectivity for greenhouse gases was produced. Porous ACP with a specific BET surface area of >400 m2/g was obtained by introducing phosphoric acid to the ACC suspension obtained during the synthesis of porous ACC. Similar to porous ACC, porous ACP was constructed of aggregated nanoparticles. ACP was found to be stable in ambient conditions for over 12 months and the stability could also be tailored by adjusting its composition. Porous ACP was cytocompatible and an effective drug carrier for alendronate - a bisphosphate drug for treatment of osteoporosis. The development of porous ACC and porous ACP as functional porous materials is summarized in this thesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 71
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1844
Keywords [en]
amorphous calcium carbonate, amorphous calcium phosphate, stabilization, crystallization, porous material, drug delivery, gas adsorption
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
URN: urn:nbn:se:uu:diva-391172ISBN: 978-91-513-0727-5 (print)OAI: oai:DiVA.org:uu-391172DiVA, id: diva2:1344716
Public defence
2019-10-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2019-09-18 Created: 2019-08-21 Last updated: 2019-10-15
List of papers
1. Amorphous Calcium Carbonate Constructed from Nanoparticle Aggregates with Unprecedented Surface Area and Mesoporosity
Open this publication in new window or tab >>Amorphous Calcium Carbonate Constructed from Nanoparticle Aggregates with Unprecedented Surface Area and Mesoporosity
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 25, p. 21556-21564Article in journal (Refereed) Published
Abstract [en]

Amorphous calcium carbonate (ACC), with the highest reported specific surface area of all current forms of calcium carbonate (over 350 m2 g-1), was synthesized using a surfactant-free, one-pot method. Electron microscopy, helium pycnometry, and nitrogen sorption analysis revealed that this highly mesoporous ACC, with a pore volume of ∼0.86 cm3 g-1 and a pore-size distribution centered at 8-9 nm, is constructed from aggregated ACC nanoparticles with an estimated average diameter of 7.3 nm. The porous ACC remained amorphous and retained its high porosity for over 3 weeks under semi-air-tight storage conditions. Powder X-ray diffraction, large-angle X-ray scattering, infrared spectroscopy, and electron diffraction exposed that the porous ACC did not resemble any of the known CaCO3 structures. The atomic order of porous ACC diminished at interatomic distances over 8 Å. Porous ACC was evaluated as a potential drug carrier of poorly soluble substances in vitro. Itraconazole and celecoxib remained stable in their amorphous forms within the pores of the material. Drug release rates were significantly enhanced for both drugs (up to 65 times the dissolution rates for the crystalline forms), and supersaturation release of celecoxib was also demonstrated. Citric acid was used to enhance the stability of the ACC nanoparticles within the aggregates, which increased the surface area of the material to over 600 m2 g-1. This porous ACC has potential for use in various applications where surface area is important, including adsorption, catalysis, medication, and bone regeneration.

Keywords
amorphous calcium carbonate, drug delivery, large-angle X-ray scattering, nanoparticles, porous materials
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-358032 (URN)10.1021/acsami.8b03939 (DOI)000437811400059 ()29862822 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 2014-3929
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-08-21Bibliographically approved
2. Highly Porous Amorphous Calcium Phosphate
Open this publication in new window or tab >>Highly Porous Amorphous Calcium Phosphate
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(English)In: Article in journal (Other academic) Submitted
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-391171 (URN)
Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-08-21
3. The Effects of Additives on the Porosity and Stability of Amorphous Calcium Carbonate
Open this publication in new window or tab >>The Effects of Additives on the Porosity and Stability of Amorphous Calcium Carbonate
(English)In: Article in journal (Other academic) Submitted
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-391170 (URN)
Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-08-21
4. Mesoscale Transformation of Amorphous Calcium Carbonate to Porous Vaterite Microparticles with Morphology Control
Open this publication in new window or tab >>Mesoscale Transformation of Amorphous Calcium Carbonate to Porous Vaterite Microparticles with Morphology Control
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2019 (English)In: Crystal Growth & Design, ISSN 1528-7483Article in journal (Refereed) Published
Abstract [en]

The morphology controlled synthesis of porous vaterite microparticles from amorphous calcium carbonate (ACC) nanoparticles via mesoscale transformation and self-assembly is presented. The morphology of vaterite microparticles ranging from ellipsoidal to spherical can be controlled by adjusting the amount of adipic acid (AA) additive during synthesis. Electron microscopy and electron diffraction reveal that the vaterite microparticles are formed by the oriented self-assembly of vaterite nanocrystals. The Brunauer−Emmett−Teller (BET) surface area of the vaterite microparticle varies between ∼30 and ∼80 m2/g. The coverage of AA on the surface of the ACC nanoparticle plays the pivotal role in the morphology controlled synthesis of vaterite microparticles. 6-Aminocaproic acid (6A), benzoic acid (BA), citric acid (CA), and poly(acrylic acid) (PAA) are also tested as additives and their effect on the morphology of vaterite microparticles is presented. Morphology control of functional materials can be beneficial for application where the morphology and porosity are critical, such as drug delivery. This work demonstrates a possible method to finely adjust the morphology of vaterite microparticles with the assistance of additives through mesoscale transformation and self-assembly using amorphous nanoparticles as precursors.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-390852 (URN)
Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-21
5. Hierarchical Porous Carbon Synthesized from Novel Porous Amorphous Calcium or Magnesium Citrate with Enhanced SF6 Uptake and SF6/N2 Selectivity
Open this publication in new window or tab >>Hierarchical Porous Carbon Synthesized from Novel Porous Amorphous Calcium or Magnesium Citrate with Enhanced SF6 Uptake and SF6/N2 Selectivity
2019 (English)In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 2, no 2, p. 778-789Article in journal (Refereed) Published
Abstract [en]

The emission of greenhouse gases such as CO2and SF6 is believed to contribute significantly toward globalwarming. One way to reduce their release is by adsorption atpoint sources using a suitable adsorbent. In this work we presentthe synthesis of two hierarchical porous carbon materials(referred to as PC-CaCit and PC-MgCit) with a high uptake ofSF6 (5.23 mmol/g, 0 °C, 100 kPa) and a reasonable uptake ofCO2 (>3 mmol/g). PC-CaCit and PC-MgCit were obtained bypyrolysis of the most porous calcium citrate and magnesiumcitrate ever reported, which were synthesized by us. TheLangmuir specific surface area of PC-CaCit and PC-MgCit wasover 2000 m2/g (BET surface area also close to 2000 m2/g). Wecharacterized PC-CaCit and PC-MgCit using a range of advanced characterization techniques including N2 adsorption, highresolutionelectron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. PC-CaCit and PC-MgCit alsoshowed a SF6-over-N2 selectivity of ∼33 at 0 °C (100 kPa), good cyclic performance, and moderately low heat of adsorption.The porous carbons synthesized in this work are good candidate adsorbents for greenhouse gases.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
porous carbon, SF6 adsorption, CO2 adsorption, amorphous calcium citrate, amorphous magnesium citrate
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-381054 (URN)10.1021/acsanm.8b02005 (DOI)000469409900019 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-08-21Bibliographically approved

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