The crystallization of calcium carbonate was conducted by the reaction of sodium carbonate with calcium chloride in the presence of polyvinylpyrrolidone (PVP), sodium dodecylbenzene sulfonate (SDBS), or the mixture of PVP and SDBS, respectively. The morphology and polymorphism of these CaCO3 crystals were characterized with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The results showed that the organic additives and their self-assemblies turn out to be important factors to affect the crystallization habit of CaCO3. In particular, the controlling effect on the morphology depends upon not only the total concentration of PVP and SDBS, but also the relative concentration ratio of PVP to SDBS.

The synthesis of calcium carbonate (CaCO3) crystals from aqueous solutions containing anion surfactants (sodium dodecylsulfonate (DDS), sodium dodecylbenzenesulfonate (SDBS)) or anionic surfactant–poly(N-vinyl-1-pyrrolidone) (PVP) complexes has been performed by the method of rapid mixing of the solutions of calcium chloride (CaCl2) and sodium carbonate (Na2CO3), followed by 10-h incubation under stirring. Polymorphism of CaCO3 crystals was observed in different additive systems. In pure anionic surfactant systems, DDS induced the transformation of initially formed amorphous CaCO3 to calcite, while SDBS favored the formation of vaterite as the final product. The addition of PVP into the above two anionic surfactant systems, promoting the formation of supermolecular complexes of surfactant/polymer, resulted in a distinct variation of the morphology of CaCO3 crystals. The polymorphs of CaCO3 are dependent not only on PVP but also on DDS or SDBS concentrations in the complex solution, i.e., anionic surfactants control the crystalline phase, but PVP only changes the crystal shape.

Hydrogels of calcium alginate are the cross-linked networks containing a large fraction of water, which were used as the precursors of calcium carbonate (CaCO3) mineralization for the first time. The well-defined geometry, the permeability, and the ion-exchange property of these pregels favored the facile fabrication of calcite superstructures through the slow inpouring of ammonia and carbon dioxide gases. When calcium alginate hydrogels sponged up a relatively high amount of liquid, the resulting products with the outside calcite sequences transcribed the spongelike pregel beads with the outside nucleation sites of carboxyl groups. The inner characteristic of these CaCO3 superstructures showed the endocentric growth trends of calcite, indicating the permeability of hydrogel beads and the diffusing directions of permeated gases. In the presence of low liquid content, the pregels favored the formation of calcite superstructures with relatively smooth surfaces, demonstrating the inside lamellar array of alcite nanoparticles. This strategic approach indicated to a great extent the biologically controlled mineralization mechanism, dealing with (1) the preadsorption of calcium ions by the functional groups of biomolecules, (2) the confined crystallization within the threedimensional networks, and (3) the proper arrangement of nanosized calcites by association with the organic architectures. Surprisingly, even the apparently "single-crystalline" CaCO3 was proven to comprise tiny calcite rhombohedrons. Furthermore, these building blocks coaligned each other with respect to the polymers' conjugated backbones. Therefore, these suggest a novel pathway of multivalent metal pregelation phases for the biomimetic fabrication of functional materials.

It is believed that chitosan plays an important role on the formation of specific inorganic–organic hybrid structure of shells. In this paper, insoluble chitoan was modified to a water-soluble macromolecule-carboxymethyl chitosan (CMCS), and further used as an additive in the crystallization process of calcium carbonate (CaCO3). The combination investigation of XRD, Micro FT-IR and SEM on the precipitated crystals shows that the addition of CMCS obviously changed the crystal morphology, but did not induce the transformation of the crystal form, i.e., CaCO3 keeps calcite form in all the cases no matter whether CMCS exists or not in the precipitation systems. The morphological variation of CaCO3 strongly depends on the CMCS concentration in the aqueous solutions.

Alkaline agents have an appeal for enhanced oil recovery because of their low cost and favorable performance. In this paper, sodium carbonate (Na2CO3) and sodium hydroxide (NaOH) are used as the alkaline chemicals, at the same Na2O content, to investigate the oil/water interfacial reactions between the Daqing crude oil and the alkaline solutions. Moreover, oleic acid or the mixture of ethyl acetate and phthalic acid diethyl ester were added into the crude oil, respectively, to facilitate the direct observation of the interfacial reactions and to compare the functional effectiveness of alkalis. The results showed that: Na2CO3 reacted slowly and partly with the acid components in crude oil, while NaOH did it very fast and completely. Interestingly, Na2CO3 is better than NaOH in lowering the oil/water interfacial tension (IFT), due to its buffer effect. These help the optimum formulation design of flooding alkali, which should also be of great importance for tertiary oil recovery.

The fast mixing of aqueous solutions of calcium chloride and sodium carbonate could immediately result in amorphous calcium carbonate (ACC). Under vigorous stirring, the formed ACC in the precipitation system will dissolve first and, then, transform within minutes to produce crystalline forms of vaterite and calcite. After that, the solution-mediated mechanism dominates the transformation of the thermodynamically unstable vaterite into the thermodynamically stable calcite. Although ACC is the least stable form of the six anhydrous phases of calcium carbonate (CaCO3), it could be, however, produced and stabilized by a variety of organisms. To better understand the formation-transformation mechanism of ACC and vaterite into calcite, ex-situ methods (i.e., scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy) were used to characterize the formation-transformation process of ACC and vaterite in aqueous systems without organic additives, showing that ACC sampled at different conditions has different properties (i.e., lifetime, morphology, and spectrum characterization). It is also very interesting to capture the obviously polycrystalline particles of CaCO3 during the transformation process from vaterite to calcite, which suggests the formation mechanism for the calcite superstructure with multidimensional morphology.

An anionic surfactant interacts strongly with a polymer molecule to form a self-assembled structure, due to the attractive force of the hydrophobic association and electrostatic repulsion. In this crystallization medium, the surfactant-stabilized inorganic particles adsorbed on the polymer chains, as well as the bridging effect of polymer molecules, controlled the aggregation behavior of colloidal particles.1 In this presentation, the spontaneous precipitation of calcium carbonate (CaCO3) was conducted from the aqueous systems containing a water-soluble polymer (poly(vinylpyrrolidone), PVP) and an anionic surfactant (sodium dodecyl sulfate, SDS). When the SDS concentrations were lower than the onset of interaction between PVP and SDS, the precipitated CaCO3 crystals were typically hexahedron-shaped calcite; the increasing SDS concentration caused the morphologies of CaCO3 aggregates to change from the flower-shaped calcite to hollow spherical calcite, then to solid spherical vaterite. These results indicate that the self-organized configurations of the polymer/surfactant supramolecules dominate the morphologies of CaCO3 aggregates, implying that this simple and versatile method expands the morphological investigation of the mineralization process.

The synthesis of calcium carbonate (CaCO3) crystals from aqueous solutions containing sodium dodecyl sulfate (SDS), poly(N-vinyl-1-pyrrolidone) (PVP) or SDS/PVP complexes has been performed through a slow titration method. It was found that aragonite and calcite coexisted in the prepared crystals. The formation of aragonite in the precipitation systems without magnesium ions indicates that at ambient temperature ca. 26.0℃, initially formed amorphous CaCO3 could also transfer into aragonite in the sedimentary phase, which indicates the controlling factor of organic additives in the nucleation and growth process of CaCO3 crystals. The appearance of hexagonal crystals in the suspensible phase confirmed the hexagonal crystallization cell of vaterite, and revealed the colloidal-dispersion function of the SDS/PVP complex in the crystallization process of CaCO3.

In this paper, the functionalized surfactant of copper dodecyl sulfate [Cu(DS)2] was used both as the metal ion source and as the modifier to investigate the preparation and shape evolution of cuprous oxide (Cu2O). The increase of Cu(DS)2 concentration from 0.27 to 6.82 mM caused the morphological change of Cu2O crystals from the truncated cubic to the cuboctahedral, then to the coexistence of the cubic and the truncated octahedral, and finally to the truncated octahedrons. As an experimental control, the inorganic salt of copper (Ⅱ) chloride was also used as the metal ion source to conduct the precipitation of Cu2O. These results indicate that the special adsorption of organic counterions (i.e., dodecyl sulfate ions) exerted a great influence on the shape control of Cu2O crystals, especially at a relatively low concentration. Meanwhile, the D-glucose concentration and the incubation time of crystals were also considered. In conclusion, the competitive adsorption of surfactant ions and D-glucose molecules onto crystalline faces, as well as the aging time, accounted jointly for the shape control of Cu2O crystals.

Calcium dodecyl sulfate (CDS) was used for the first time both as an anionic surfactant and as the source of mineral ions in the precipitation process of calcium carbonate (CaCO3). The simple reaction of the enriched Ca2+ ions at the so-called organic-inorganic interfaces with the slowly bubbled CO2 gas resulted in the metastable vaterite polymorph with various structures. The single-crystalline vaterite of the hexagonal platelets, the lens-shaped structures with hexagonal symmetry, the olive-shaped superstructures and these with a concave at each top of olives, and another metastable polymorph of aragonite were obtained, respectively, depending upon the concentration ratio between CDS and n-pentanol. The synergistic effect of CDS and n-pentanol is believed to play a crucial role in driving the oriented aggregation of metastable nanoparticles. Simultaneously, the novel phase transformation of vaterite to aragonite was observed, implying the possible formation mechanism of aragonite at room temperature and in the absence of magnesium ions.