| 1. |
- Neira-Carrillo, Andronico, et al.
(författare)
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Synthesis and characterization of sulfonated polymethylsiloxane polymer as template for crystal growth of CaCO3
- 2009
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Ingår i: Colloid and Polymer Science. - : Springer Science and Business Media LLC. - 0303-402X .- 1435-1536. ; 287:4, s. 385-393
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to synthesize a sulfonated polymethylsiloxane (S-PMS) by hydrosilylation and sulfonation reactions and to investigate their effect on the growth of CaCO3 crystals using a gas diffusion method as a function of concentration, pH, and time. The result of IR and NMR shows good agreement with all proposed structures. Scanning electron microscopy images of CaCO3 showed small well-defined calcite-forming short piles (ca 5 mu m) and elongated calcite (ca 20 mu m) crystals. The morphology of the resultant CaCO3 crystals reflects the electrostatic interaction of sulfonate moieties and Ca2+ modulated by S-PMS adsorbed onto the CaCO3 surface. X-ray diffraction confirmed the crystalline calcite polymorph. Energy dispersive spectroscopy of CaCO3 crystals determined the presence of Si atoms from S-PMS. The use of PMS chemistry as an organic additive for the production of CaCO3 particles is a viable approach for studying the biomineralization and could be useful for the design of novel materials with desirable shape and properties.
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| 2. |
- Nieira-Carrillo, Andronico, et al.
(författare)
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Calcium carbonate growth modification by constituents releases from porous cellulose filter membranes
- 2008
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Ingår i: Journal of the Chilean Chemical Society (Print). - 0717-9324 .- 0717-9707. ; 53:2, s. 1469-1473
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Tidskriftsartikel (refereegranskat)abstract
- Filtration of a suspension of calcium carbonate (CaCO3) or other inorganic solutions are often part of the methodology for recovering crystals during biomimetic mineralization experiments performed by various procedures. However, the use of cellulose filter membranes (FM) may cause a problem in in vitro crystallization experiments, because constituents released from the filters into the filtrates can alter the morphology of CaCO3 crystals. Therefore, it is possible to misinterpret data obtained when the effect of specific additives tested in the investigation of biomineralization mechanisms. Herein, we present essential information to avoid such misinterpretations of data obtained from mineralization experiments. CaCO3, was precipitated at room temperature by the gas diffusion method in the presence of FM as support and particularly as filtrates of calcium chloride (CaCl2) obtained from various commercial FM. The occurrence or absence of morphological modifications of the calcite and vaterite crystals obtained with different FM correlates well with the different elemental compositions of the solutions where crystals are grown because of the constituents released from the filters into the filtrate. X-ray photoelectron spectroscopy (XPS) data indicate significant differences in the filter elemental composition. We assume that the observed chronological changes in CaCO3 crystal modification could be due to incorporation into the calcite lattice of constituents released from the FM, most likely monomers, oligomers, or short-chain polymers.
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| 3. |
- Pai, Ranjith Krishna, et al.
(författare)
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Divalent cation-induced variations in polyelectrolyte conformation and controlling calcite morphologies : Direct observation of the phase transition by atomic force microscopy
- 2008
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 130:39, s. 13074-13078
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Tidskriftsartikel (refereegranskat)abstract
- In the biomineralization process, the changes in conformation of organic matrix may be a widespread phenomenon. Investigation of the structural relationship between organic and inorganic materials is the main subject. The approach taken was to extract quantitative information of the variations in polyelectrolyte conformation during the mineralization process using atomic force microscopy. The results inter the evidence of the role of polyelectrolyte conformation in mineralization of calcium carbonate and the methods for understanding the principle that govern biomineralization.
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| 4. |
- Pai, Ranjith Krishna, et al.
(författare)
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Nanoparticles of amorphous calcium carbonate by miniemulsion : synthesis and mechanism
- 2008
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 10:7, s. 865-872
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of the present study is to develop a system to synthesize stable amorphous calcium carbonate (ACC) particles with controlled particle size in the range of nanometers by the use of miniemulsion technique and to understand the 'facilitated transport mechanism'. The surfactant adsorption can be explained by the change in solubility of CaCO3 and surfactant in aqueous solution. This article covers our experimental observations and the possible reaction mechanisms.
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| 5. |
- Pai, Ranjith Krishna, et al.
(författare)
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Temperature induced formation of strong gels of acrylamide-based polyelectrolyte
- 2009
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 337, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- Very strong physical gels have been formed by moderate temperature increases in aqueous dispersions of acrylamide-based beads and dissolved polymeric molecules. Rheometry, confocal laser scanning microscopy, and differential scanning calorimetric studies of acrylamide-based copolymers with acrylic acid, [Poly(AM-co-AA)], and 2-acrylamido-2-methylpropane acid, [Poly(AM-co-NaAMPS)], suggest that the temperature induced swelling of the polymer beads and chains, create strongly entangled polymer networks, above the upper critical solution temperature. Analyses of the viscoelastic response showed that the time-scale for the gelation process is about minutes to hours. The addition of high concentrations of Ca2+ resulted in a significant decrease in the gel strength
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| 6. |
- Pai, Ranjith Krishna, et al.
(författare)
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Transport-Mediated Control of Particles of Calcium Carbonate.
- 2009
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 9:11, s. 4581-4583
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Tidskriftsartikel (refereegranskat)abstract
- Micrometer-sized particles of calcium carbonate were formed by adding NaHCO3 (aq) to a buffered aq. soln. of CaCl2 (aq) and polyelectrolytes. Particle morphol. and crystal polymorphol. were tuned by varying the stirring rate. Vigorous stirring led to the formation of micrometer-sized spherical particles of nanocryst. vaterite; slow stirring formed rhombohedral nanostructured particles of calcite.
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| 7. |
- Pillai, Saju, et al.
(författare)
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Effect of lateral morphology formation of polymer blend towards patterning silane-based SAMs using selective dissolution method
- 2008
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 108:5, s. 458-464
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Tidskriftsartikel (refereegranskat)abstract
- A number of strategies have been developed including soft lithography and photolithography for patterning various surfaces. Here we have discussed a customized strategy for surface patterning of nanosized, silane-based SAMs and monolayer thickness measurement investigated using atomic force microscope (AFM). We have utilized the versatile morphology of a binary polymer blend to generate patterned SAMs over silicon substrate by employing a selective dissolution procedure. This method was confirmed with different organosilanes with varying number of C-atoms and to other polymer blend. The samples were imaged both in tapping mode and pulsed force mode AFM.
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| 8. |
- Thormann, Esben, et al.
(författare)
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Embedded proteins and sacrificial bonds provide the strong adhesive properties of gastroliths
- 2012
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 4:13, s. 3910-3916
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Tidskriftsartikel (refereegranskat)abstract
- The adhesive properties of gastroliths from a freshwater crayfish (Cherax quadricarinatus) were quantified by colloidal probe atomic force microscopy (AFM) between heavily demineralized gastrolith microparticles and gastrolith substrates of different composition. Combined AFM and transmission electron microscopy studies demonstrated that the sequential detachment and large adhesion energies that characterise the adhesive behaviour of a native gastrolith substrate are dominated by sacrificial bonds between chitin fibres and between chitin fibres and CaCO3. The sacrificial bonds were shown to be strongly related to the gastrolith proteins and when the majority of these proteins were removed by ethylenediaminetetraacetic acid (EDTA), the sequential detachment disappeared and the adhesive energy was reduced by more than two orders of magnitude.
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