Three surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and polyoxyethylene-80-sorbitan monooleate (Tween 80), were used to control the growth of CaCO3 crystals by carbonation route using Ca(OH)2 and compressed CO2. The obtained CaCO3 particles were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The effects of surfactants on the morphology of the particles were studied. It was demonstrated that Tween 80 and SDS have obvious effect on the morphology of CaCO3 particles, while CTAB does not affect morphology considerably. The possible mechanism has been discussed on the basis of the binding of the surfactants to the certain face of the crystals. 相似文献
Calcium carbonate (CaCO3) nanocrystals with controllable polymorph and morphology have been successfully synthesized with the aid of an effective control agent, a halogen-free, low-cost ionic liquid surfactant, 1-butyl-3-methylimidazolium dodecylsulfate ([C4mim][C12SO4]) in a supersaturated aqueous solution. For the first time, facile preparation of pure lens-like vaterite, sheet-like calcite, and peanut-like aragonite was all achieved in the [C4mim][C12SO4] aqueous solution through changing the concentration, temperature, and initial pH value and adding magnesium ions. Washed by water and ethanol, all the aggregates were free of [C4mim][C12SO4] and can be stable at least 1 month in air. The crystal form of the aggregates changed from pure calcite to pure vaterite at room temperature only through increasing [C4mim][C12SO4] concentration. Formation of the ordered CaCO3 structures is mainly ascribed to the aggregation of the primary nanoparticles whose formation mechanism is related to the change of supersaturation. This study can provide a facile and environment-friendly method to fabricate CaCO3 crystal aggregates with various morphologies and polymorphs and can be used for large-scale industrial production and biomimetic synthesis. 相似文献
Superhydrophobic nanocalcite crystals were prepared via an adjusted aqueous reaction of CaO, CO2 gas and sodium oleate. Box–Behnken design was used to optimize the preparation parameters such as CaO concentration, CO2 gas flow rate and surfactant concentration. The results revealed that the produced CaCO3 is indexed to the calcite phase. The crystallite size, particle size, morphology, hydrophobicity and surface charge of CaCO3 are significantly affected by changing the preparation parameters. The addition of sodium oleate helps in reducing the crystallite size from 101 nm to 48 nm, reducing the particle size from 1.5 μm length scalenohedral particles to 40 nm rhombohedral particles and modifying the properties of pure CaCO3 from highly hydrophilic to superhydrophobic. 相似文献
Biomineralization, a well-known natural phenomenon associated with various microbial species, is being studied to protect and strengthen building materials such as concrete. We characterized Rhodococcus erythreus S26, a novel urease-producing bacterium exhibiting CaCO3-forming activity, and investigated its ability in repairing concrete cracks for the development of environment-friendly sealants. Strain S26 grown in solid medium formed spherical and polygonal CaCO3 crystals. The S26 cells grown in a urea-containing liquid medium caused culture fluid alkalinization and increased CaCO3 levels, indicating that ureolysis was responsible for CaCO3 formation. Urease activity and CaCO3 formation increased with incubation time, reaching a maximum of 2054 U/min/mL and 3.83 g/L, respectively, at day four. The maximum CaCO3 formation was achieved when calcium lactate was used as the calcium source, followed by calcium gluconate. Although cell growth was observed after the induction period at pH 10.5, strain S26 could grow at a wide range of pH 4–10.5, showing its high alkali tolerance. FESEM showed rhombohedral crystals of 20–60 µm in size. EDX analysis indicated the presence of calcium, carbon, and oxygen in the crystals. XRD confirmed these crystals as CaCO3 containing calcite and vaterite. Furthermore, R. erythreus S26 successfully repaired the artificially induced large cracks of 0.4–0.6 mm width. 相似文献
Cytarabine (Cyt) encapsulated calcium carbonate (CaCO3) nanospheres were facilely synthesized through a simple co-precipitation method, and the Cyt encapsulated CaCO3 nanospheres (CaCO3/Cyt) were modified by polyacrylic acid (PAA) hydrogels through in situ polymerization of acrylic acid (AA) monomer on the surface of the CaCO3/Cyt. Successful preparation of the Cyt loaded CaCO3/PAA hydrogels were confirmed by the characterization of SEM, TEM and FT-IR. Premature release of Cyt in acidic medium (pH = 1.2) could be effectively circumvented by the introduction of the PAA hydrogels. More importantly, pH-responsive delivery of Cyt from the as-prepared CaCO3/PAA hydrogels could be achieved due to the pH-sensitivity of the PAA. Although the highest swelling ratio of PAA was obtained at pH 7.3 (27.7), the highest cumulative release of Cyt from the carrier was achieved at pH 5.3 (86.75%), which might be attributed to the high stability of CaCO3 at pH 7.3. That is to say, the highest cumulative release of Cyt at pH 5.3 was a compromise by considering the relatively high swelling ratio of PAA and the relatively low stability of CaCO3. 相似文献
The structure of trithallium hydrogen bis(sulfate), Tl3H(SO4)2, in the super‐ionic phase has been analyzed by Rietveld analysis of the X‐ray powder diffraction pattern. Atomic parameters based on the isotypic Rb3H(SeO4)2 crystal in space group Rm in the super‐ionic phase were used as the starting model, because it has been shown from the comparison of thermal and electric properties in Tl3H(SO4)2 and M3H(SO4)2 type crystals (M = Rb, Cs or NH4) that the room‐temperature Tl3H(SO4)2 phase is isostructural with the high‐temperature Rm‐symmetry M3H(SO4)2 crystals. The structure was determined in the trigonal space group Rm and the Rietveld refinement shows that an hydrogen‐bond O—H?O separation is slightly shortened compared with O—H?O separations in isotypic M3H(SeO4)2 crystals. In addition, it was found that the distortion of the SO4 tetrahedra in Tl3H(SO4)2 is less than that in isotypic crystals. 相似文献
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 μm) and elongated calcite (ca 20 μm) 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. 相似文献
Proton-NMR. spectra of amino- and hydroxypyrimidines including biologically important bases have been measured in four solvents: CF3COOH, CF3COOH? SO2, FSO3H and FSO3H? SbF5–SO2 at 27° and ?55°C. In CF3COOH mono-cations are formed, whereas in FSO3H and FSO3H? SbF5–SO2 double protonation occurs. In each case the structures of the protonated species are derived from the chemical shifts of CH, NH and OH protons and proton-proton spin coupling constants. A combination of the measurements described leads to a complete assignment of all proton resonances of the protonated pyrimidines. This approach is also recommended for the structural determination of heterocyclic compounds. 相似文献
The title compound, C21H21NO7S3, consists of an SO2ON(SO2)2 central fragment and three terminal 4‐methylphenyl groups each attached at a sulfonyl S atom. The most obvious characteristic is the presence of two nearly face‐to‐face benzene rings, with their centroids separated by a rather short distance [3.7808 (18) Å], but with a rather slanted relative orientation [dihedral angle = 20.63 (13)°] so as to preclude a strong intramolecular π–π interaction. The third benzene ring is nearly perpendicular to the other two [dihedral angles = 71.62 (14) and 70.4 (13)°]. The packing of the structure is directed by two C—H...O hydrogen bonds involving aromatic H atoms (methyl H atoms are strictly non‐interacting), which define chains running in the [100] direction. These one‐dimensional chains evolve parallel to each other and exhibit no significant lateral interactions. 相似文献
Summary: An in‐situ mineralization process in the presence of thermo‐responsive microgels leads to the formation of well‐defined hybrid materials. Experimental data suggest that control of the mineralization process in the presence of the microgels offers the possibility to obtain sub‐micrometer‐sized hybrid particles or macroscopic hybrid hydrogels. The rapid formation of CaCO3 crystals in the microgel structure favors the preparation of the hybrid particles wherein inorganic crystals cover the shell layer of the microgel. The slow formation of CaCO3 crystals leads to the simultaneous self‐assembly of the microgel particles on the bottom of the reaction vessel, and the formation of a physical network. It has been demonstrated that hybrid hydrogel materials with different calcium carbonate contents and temperature‐dependent swelling‐deswelling properties can be prepared.
Formation of a hybrid hydrogel by the vapor diffusion method. 相似文献
A tri‐quaternary ammonium salt cationic surfactant was synthesized. Its structure was confirmed by using Fourier‐transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy analyses. Three model surfaces, including Au‐CH3, Au‐OH and Au‐COOH, were fabricated. Adsorptions of surfactant on the three model surfaces and subsequent plasma proteins adsorption were investigated by quartz crystal microbalance with dissipation (QCM‐D). The mass of surfactant on the Au‐COOH surface was the largest, followed by that on the Au‐CH3 surface, and that on the Au‐OH surface. These results suggested that the main driving force of surfactant immobilization was electrostatic interaction followed by hydrophobic interaction. Based on the results obtained, we concluded that the protein mass adsorbed on Au‐CH3‐ S , Au‐OH‐ S , and Au‐COOH‐ S surfaces depended on the protein size and orientation. The mass and thickness of S on the Au‐COOH surface is the largest and the protein adsorption capacity of Au‐COOH‐ S surface is inferior to that of Au‐CH3‐ S . The Au‐COOH‐ S surface could inhibit lysozyme adsorption, maintain the adsorption balance of bovine serum albumin, and induce fibrinogen‐binding protein adsorption. 相似文献
A mixed system of poly (styrene-alt-maleic acid) (PSMA) and cetyltrimethylammonium bromide (CTAB) was used as a very effective crystal growth modifier to direct the controlled synthesis of CaCO3 crystals with various morphologies and polymorphs. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. It was found that the concentrations and relative ratios of PSMA and CTAB in the mixed aqueous solution were turned out to be important parameters for the morphology and polymorph of CaCO3 crystals. Various morphologies of CaCO3 crystals, such as hollow microsphere, peanut and so on, were produced depending on the concentrations and relative ratios of PSMA and CTAB. Moreover, the formation mechanisms of CaCO3 crystals with different morphologies were discussed. 相似文献
We documented a specific method for combining calcium ions and alginate molecules slowly and continuously in the mineralization system for the purpose of understanding the mediating function of alginate on the crystallization of calcium carbonate. The alginate was involved in the nucleation and the growth process of CaCO3. The crystal size, morphology and roughness of crystal surface were significantly influenced by the type of the alginate, which could be accounted for by the length of the G blocks in alginate. A combination of Fourier transform infrared spectroscopy and thermogravimetric analysis showed that there were the chemical interactions between the alginate and the mineral phase. This strategic approach revealed the biologically controlled CaCO3 mineralization within calcium alginate hydrogels via the selective nucleation and the confined crystallization of CaCO3. The results presented here could contribute to the understanding of the mineralization process in hydrogel systems. 相似文献
A new type of CuII ion sorbents is presented. These are obtained by CaCO3 mineralization from supersaturated solutions on gel‐like cross‐linked polymeric beads as insoluble templates. A divinylbenzene–ethylacrylate–acrylonitrile cross‐linked copolymer functionalized with weakly acidic, basic, or amphoteric functional groups has been used, as well as different initial inorganic concentrations and addition procedures for CaCO3 crystal growth. The morphology of the new composites was investigated by SEM and compared to that of the unmodified beads, and the polymorph content was established by X‐ray diffraction. The beads, before and after CaCO3 mineralization, were tested as sorbents for CuII ions. The newly formed patterns on the bead surface after CuII sorption were observed by SEM, and the elemental distribution on the composites and the chemical structure of crystals after interaction with CuII were investigated by EDAX elemental mapping and by FTIR‐ATR spectroscopy, respectively. The sorption capacity increased significantly after CaCO3 crystals growth on the weak anionic bead surface (up to 1041.5 mg CuII/g sample) compared to that of unmodified beads (491.5 mg CuII/g sample). 相似文献
In order to investigate how the self-assembly of organic matrix influences crystallisation and growth of inorganic minerals, we selected collagen as the matrix and conducted three experiments of crystallisation of CaCO3 in different reaction systems: H2O system, as-assembled collagen fibrils system and self-assembling of collagen system. It is found that (i) the self-assembly process of organic matrix had a remarkable effect on the morphology of inorganic minerals: CaCO3 crystals formed in the as-assembled collagen fibrils system were global clusters and those formed in the self-assembling of collagen system appeared as interlaced networks and (ii) the organic matrix decided the polymorph of crystals: CaCO3 crystals were calcite in the H2O system and appeared vaterite in the collagen system. From this study, we can conclude that the self-assembly of collagen fibrils greatly affect the crystallisation and growth of CaCO3. Such results are significant in understanding the mechanism of biomineralisation in calcified tissues in general, and useful in the synthesis of biominerals. (a)?CaCO3 formed in the as-assembled collagen fibrils system. (b)?CaCO3 formed in the self-assembling of collagen monomer system.The TEM images of samples obtained in the as-assembled collagen fibrils and self-assembling of collagen monomer system, were observed, respectively. The result shows that crystals CaCO3 formed in the as-assembled collagen fibrils system were global clusters; crystals CaCO3 formed in the self-assembling of collagen monomer system appeared interlaced networks. 相似文献