Catanionic Surfactant-Assisted Mineralization and Structural

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Catanionic Surfactant-Assisted Mineralization and Structural Properties of Single-Crystal-Like Vaterite Hexagonal Bifrustums Rui Liu, Fenglin Liu, Yunlan Su, Dujin Wang, and Qiang Shen Langmuir, Just Accepted Manuscript • DOI: 10.1021/la503726y • Publication Date (Web): 12 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

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Catanionic Surfactant-Assisted Mineralization and Structural Properties of Single-Crystal-Like Vaterite Hexagonal Bifrustums Rui Liu,† Fenglin Liu,1,† Yunlan Su,‡ Dujin Wang‡ and Qiang Shen*,† †

Key Laboratory for Colloid and Interface Chemistry of Education Ministry, School of

Chemistry & Chemical Engineering, Shandong University, Jinan 250100, China ‡

Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics,

Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.

ACS Paragon Plus Environment

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ABSTRACT: Crystalline vaterite is the most thermodynamically unstable polymorph of anhydrous calcium carbonate (CaCO3), and various morphologies can be controlled in the presence of organic additives. Constructing vaterite with minimal defects, determining its distinctive properties and understanding the formation mechanism behind a biomimetic process, are the main challenges in this field. In this paper, a unique single-crystal-like vaterite hexagonal bifrustum with two hexagonal and twelve trapezoidal faces has been fabricated through a catanionic surfactant-assisted mineralization approach for the first time. Compared with the polycrystalline vaterite aggregates, these bifrustums clearly present a doublet for Raman v1 symmetric stretching mode, a low depolarizaiton ratio for carbonate molecular symmetry and a high structural stability. These indicate a dominant position of hexagonal phase in each crystallite and confirm the Raman v1 doublet characteristics of synthetic and biomineral-based vaterites. Our finding may provide evidence to distinguish vaterite with different structures and shed light on a possible formation mechanism of vaterite single crystals.

KEYWORDS: Crystal growth, mineralization, polymorphism, vaterite, surfactants, single crystal.


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INTRODUCTION Calcium carbonate (CaCO3) is one of the most abundant minerals in nature and has been defined as a modeling material to investigate the biomineralization mechanism of invertebrate shells for a long time.1 Among the three well-known polymorphs of anhydrous CaCO3 (i.e., the generally defined calcite, aragonite and vaterite), the most thermodynamically unstable vaterite is often produced as polycrystalline aggregates either naturally or artificially. In biological systems, vaterites have been found in the statoliths of Mysidae,2 otoliths of teleostfishes,3 and porcine and human cardiac valve leaflets.4 In controlled artificial systems, spherical vaterite aggregates are commonly collected and applied as precursors for the crystal design of metastable aragonite and/or thermodynamically stable calcite.2, 5-8 Polycrystalline9-11 or meso-crystalline12, 13 (i.e., an ordered array of single-crystalline building blocks) vaterites can be facilely precipitated under various experimental conditions, such as by template-directed,14-16 ultrasonic17,

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and

additive-directed3, 7, 19 methods. Considering the recently well-demonstrated vaterite carbonate-rational polymorphism itself, the structural properties are still unclear so far. Multiple crystal phases (e.g., hexagonal and the others) could coexist in an integral structure of natural or synthetic products owing to the rotational freedom of carbonate groups, the multiple stacking sequences of carbonate layers and/or the corresponding chirality.5,

20-22

The ever proved crystal phases of the hexagonal,

monoclinic and triclinic vaterites (i.e., the h-, m- and t-vaterites)20-27 possess the different stacking of carbonate-ion layers but have almost no energy barrier for their mutual transformation. Aside from the dominative hexagonal structure, another two low-symmetry models of t- and m-vaterite structures have been successfully applied to analyze the polymorphic nature of vaterite spherulites obtained from non-aqueous media.21 This is well consistent with


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Kabalah-Amitai’s results that the natural vaterite spicules of H. momus ascidians are predominantly composed of a hexagonal phase, coexisting with at least one other polymorph.5 For these reasons, it is impossible to obtain the traditional single-crystalline vaterite and thus the term of “single-crystal-like” is used to describe vaterite crystallite with single-crystalline features. As reported previously, geological, biological and synthetic vaterities had different structural characteristics but exhibited the similar Raman spectra containing a triplet for the v1 symmetric stretching mode.22,

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Some assumed the Raman v1 triplet coming from the two

distinct site symmetries of carbonate groups28, while others attributed the Raman v1 triplet to vaterite coexisting with calcite impurity.28-31 Occasionally, micro-Raman spectrum of a vaterite domain in CaCO3 polycrystalline thin film clearly displayed a doublet for Raman v1 mode.32 If the carbonate-rational polymorphism of vaterite is neglected, merely the hexagonal model with P63/mmc space group23 can ideally predict a doublet for the Raman v1 mode of single-crystalline vaterite (i.e, h-vaterite) also.33 In consideration of these, it is of crucial importance to synthesize a relatively stable single-phase vaterite and to assure its possible v1 splitting in Raman spectroscopy. As for the controlling crystallization of hexagonal CaCO3, functionalized ammonium or lithium ions may preferentially induce the stabilization of CO32--rich (00.1) crystal planes,7, 34-38 while amphiphilic polymers12, 39 or surfactants40-42 may experience a specific adsorption onto the Ca2+-rich (00.1) crystal planes. Through the lamellar self-assemblies of Ca2+-containing surfactants in dilute ammonia, the hexagonal tablets of twinning aragonite,40 mesocrystal-like calcite41 or intermediate vaterite43 can be selectively produced. In this work, the organicinorganic

hybrid

lamellar

self-assemblies

of

calcium

dodecyl

sulfate

Ca(DS)2,

cetyltrimethylammonium hydroxide CTAOH and ammonia are successfully introduced for the


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massive production of single-crystal-like vaterite hexagonal bifrustums through the slowly basecatalyzed hydrolysis of diethyl carbonate Et2CO3. The possible mineralization mechanism and structural properties of vaterite hexagonal bifrustums are the main topics, discussed in detail in context. This finding may provide evidence to distinguish vaterite with different structures and shed light on a possible formation mechanism of vaterite single crystals. EXPERIMENTAL SECTION Materials. Cetyltrimethylammonium hydroxide (CTAOH, 25 wt% in methanol, Shanghai Chem. Co. Ltd.), sodium dodecyl sulfate (SDS, 99.5%, Fluka), diethyl carbonate (Et2CO3, Sinopharm), methanol (CH3OH, Sinopharm), calcium chloride (CaCl2, Sinopharm), and ammonia solution (NH3·H2O, 25.0-28.0 wt%, Sinopharm) are of analytical grade and were used as purchased. Calcium dodecyl sulfate (Ca(DS)2, Krafft point ~ 50°C) was synthesized via the reaction between 100.0 g of SDS and 34.0 g of CaCl2 in 1.0 L of deionized water. The obtained product was filtered through a cellulose acetate membrane, washed with deionized water and recrystallized three times, and dried in a vacuous desiccator at room temperature. Preparation of Single-Crystal-Like and Polycrystalline Vaterites. Firstly, the mixing of aqueous Ca(DS)2 (25 mL, 45 mM) and CTAOH (25 mL, 5.0 mM) was slowly conducted in a 100-mL beaker at 60oC, and the resulting catanionic surfactant system had a total concentration of DS- and CTA+ ions at 47.5 mM and a molar ratio of DS-:CTA+ at 18:1, which is designed for the polymorphic selectivity of hexagonal vaterite. Secondly, NH3·H2O was carefully added for pH adjustment to 11.0, followed by the five-time addition of Et2CO3 solution (1.0 M in methanol, 0.225 mL once per day). Thirdly, glass slides were placed at the bottom of the beaker side by side, and then the reaction system was allowed to stand still in a thermostatic chamber


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(60oC) for 10 d. Finally, the white precipitates of single-crystal-like vaterite were washed with ethanol for 3 times and dried at room temperature prior to analysis. The typical polycrystalline sample was synthesized by quickly pouring an aqueous Na2CO3 (25 mL, 0.33 M) into a 100-mL beaker containing an equal amount of aqueous CaCl2 (25 mL, 0.33 M) in the absence of any additives, which was agitated using an ultrasonic homogenizer at 300 W for 15 s. At a short interval of 45 seconds, the milky solution was filtrated, washed with deionized water for three times, and dried at room temperature for 24 h. As far as possible, this procedure could reduce the amount of co-existing amorphous CaCO3 and delay the well-known solution-mediated phase transformation of vaterite to calcite.44 Characterization. X-ray diffraction (XRD) measurements were performed using a Rigaku D/max-2400 powder X-ray diffractometer with Cu-Kα radiation (40 kV, 120 mA), and a 0.04° step (25 s) and the 2θ range of 10-80° were selected to analyze crystal phase. Samples were Ptcoated prior to examination using a JEOL JSM-6700F scanning electron microscope (SEM) with an energy disperse spectroscopy (EDS) attachment, fitted with a field emission source and operating at an accelerating voltage of 15 kV. Samples were deposited onto a carbon film supported by a copper grid after dispersed in ethanol, prior to transmission electron microscopy (TEM) measurements on a JEM 2100 microscope (200 kV). Raman spectra were collected on a HR800 spectrometer (excitation wavelength 514.5 nm) within the wavenumber range of 100 and 1500 cm-1, and the polarization and temperature-varying measurements were similarly performed in combination with the polarizer and thermostat adjuncts. Fourier transform infrared spectroscopy (FT IR) measurements were performed on a VERTEX-70 spectrometer using the KBr tablet method, with a region of 4000–400 cm-1 and a resolution of 4 cm-1. The simultaneous thermal analysis of thermogravimetry (TGA) and different scanning calorimetry (DSC) were


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performed on a SDT Q600 apparatus under nitrogen atmosphere, with a heating rate of 10oC min-1 from room temperature to 800oC. RESULTS AND DISCUSSION Preparation of Single-Crystal-Like Vaterite Hexagonal Bifrustums. Different from the catanionic biomimetics of calcite hexagonal tablets in dilute ammonia at an DS-:CTA+ molar ratio of 8.9:1.1,41 herein the similar organic-inorganic interfaces self-assembled at the DS-:CTA+ molar ratio of 18:1 are designed for the generally po0lymorphic selectivity of hexagonal vaterite through the batch addition of Et2CO3 in 5 days. After another 5 days, the sampled precipitates present a uniform shape of well-defined hexagonal bifrustums (Figure 1a and Supporting Information, Figure S1-a). By magnification, each bifrustum can be clearly defined as a hexagonal bipyramid with two polar vertices truncated (Figure 1b, c). Most crystallites have visually single-crystalline features, such as sharp edges, side faces and reasonable interfacial angles, and have different appearance from the previously hexagonal vaterite mesocrystals composed of tiny hexagons.36 From Figure 1a-c, statistical analysis presents that these bifrustums possess an average size of 4.3 ± 0.1 µm and a thickness of ~1.4 µm. However, this solutionbased crystallization is difficult to guarantee that each hexagonal bifrustum is geometrically perfect owing to the interfacial formation and uncertain diffusion within hydrophilic domains shown below.


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Figure 1. SEM images of different vaterite products obtained at 10 days: (a−c), hexagonal bifrustums obtained from a catanionic surfactant-assisted mineralization system with the 5-time addition of Et2CO3 once per day; (d−f), pseudohexagonal platelets with irregular edges obtained from this mineralization system with the addition of Et2CO3 once for all; (g−i), ultrathin hexagonal platelets with clear side facets obtained in the absence of cationic surfactant CTAOH, and an inset on the up-right of panel (i) is the side-view SEM image of an ultrathin platelet. When Et2CO3 was added into the mineralization system once for all, pseudohexagonal bipyramids of vaterite are completely obtained at an incubation time of 10 days, comparatively showing the larger average size of 7.0 ± 1.5 µm and the smaller thickness of ~1.0 µm (Figure 1d and Supporting Information, Figure S1-b). This may facilitate a fast crystal growth of vaterite nuclei and further enlarge the differences of diffusion rate of CO32- ions in each direction, resulting in crystallites with irregular edges and growth steps (Figure 1e, f).


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Another experimental control is the 5-day batch in which Et2CO3 were added into the crystallization system without cationic surfactant CTAOH. This may slow down the release rate of gaseous CO2 at organic-inorganic interfaces. Correspondingly, this should relatively increase both the effective concentration of DS- and Ca2+ ions, and subsequently favor the nucleation of vaterite as well as the crystal growth of uniform ultrathin hexagonal platelets with an average size of 5.1 ± 1.1 µm (Figure 1g, h and Supporting Information, Figure S1-c). By magnification, side-view SEM images clearly show that these thin platelets are also the truncated hexagonal bipyramids with sharp edges and smooth facets in ~300 nm thickness (Figure 1i and the inset).

Figure 2. (a, b) XRD and (c) Raman spectral characteristics of vaterite hexagonal bifrustums. In panel a), an inset is the schematic drawing of a single-crystalline structure marked by Miller indices; in panel b), the standard data of ideal h-vaterite correspond to the Crystallographic Information File (CIF) from the NIST/FIZ FindIt database; in panel c), an inset shows the correspondingly magnified Raman v1 mode. In the absence of the anionic surfactant Ca(DS)2, irregular crystallites of thermodynamically stable calcite are formed (Supporting Information, Figure S2a, S3a). When NaOH is used instead of ammonia for pH adjustment to 11.0, XRD diffractions originating from the powdered mixture


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of Ca(DS)2 and CTAOH are detected and the corresponding SEM picture shows that these crystallites are large irregular platelets (Supporting Information, Figure S2b, S3b). A slight decrease or increase of pH value adjusted by ammonia (i.e., pH ~ 10.5 or 11.5) induces the formation of irregular platelets with unclear edges, not the single-crystal-like vaterite hexagonal bifrustums (Supporting Information, Figure S2c, d or S3c, d). In a word, these indicate that both cationic and anionic surfactants, as well as ammonia and/or pH value, play a crucial role in fabricating hexagonal single-crystal-like vaterite. XRD measurements and Raman spectral characteristics assure that, in crystallography, the products along [00.1] direction belong to the hexagonal structure23 (Figure 2). In the principle of hexagonal symmetry, the manifest bottom- and top-hexagons of a bifrustum can be ideally indexed as {00.1} crystal faces and the other twelve are the equivalent crystal planes of {2-2.1}, schematically shown as an inset in Figure 2a. Considering the standard XRD data for these (hk.l) peak intensities of randomly oriented hexagonal vaterite (i.e., h-vaterite) shown in Figure 2b, the (00.l) reflections of powdered products (Figure 2a) “change” from the lowest to the highest ones. The preferential orientation parameter (αhk.l) can be calculated using the formula: αhk.l = Ihk.l / ΣIhk.l, where Ihk.l is the relative intensity of a corresponding diffraction peak.45, 46 Approximately, the value of α00.l of the single-crystal-like vaterite hexagonal bifrustums is as high as 72%, while that of the randomly oriented vaterite powders is only 3.1%. Employing the Scherrer’s equation, an average (00.2)-domain thickness of ~90.0 nm can be estimated according to the full width at half maximum (FWHM) of (00.2) peak shown in Figure 2a. This does not conflict with the single-crystalline nature of these hexagonal bifrustums but suggests a periodic lattice imperfection (e.g., stacking fault or sub-boundary) along the [00.l] direction. Instead of a triplet in the wavenumber region of 1070 and 1084 cm-1 assigned to the


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Raman v1 symmetric stretching mode (Figure 2c) for synthetic, geological and biological vaterites,22 the single-crystal-like sample differently presents an intense doublet. This is consistent with the previously mentioned theory predication based on the imaginary hexagonal symmetry with P63/mmc space group.33 In Figure 2c, the doublet around 740 cm-1 corresponds to the v4 in-plane stretching mode and the multiplet below 400 cm-1 comes from the well-defined lattice structures of vaterite hexagonal bifrustums.

Figure 3. (a) SEM image, (b) XRD pattern and (c) Raman spectrum of visually determined vaterite polycrystalline aggregates (an average diameter of ~1.3 µm), also showing their coexistence with rhombohedral calcite impurities highlighted in red.


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Comparison of Single-Crystal-Like with Polycrystalline Vaterites. To emphasize the particularly single-crystalline nature of these hexagonal bifrustums, spherical aggregates of commonly observed polycrystalline vaterite were synthesized and characterized as a comparison (Figure 3). Considering the fact that powdered synthetic vaterite can be entirely transformed into calcite after a two-hour heat-treatment at 490oC,47 herein the visually determined polycrystalline aggregates collected at a very short reaction interval of ~1 min still coexist with a small amount of calcite impurity48, and display the common Raman v1 triplet (Figure 3a-c). As far as we know, diverse profiles are observed in Raman spectra, where the v1 mode revealed a triplet in some studies and a doublet in others.31, 32, 49 Therefore, regardless of the recently recognized carbonaterational polymorphism of vaterite itself, herein the dominative hexagonal symmetry may be concluded for both polycrystalline and single-crystal-like ones. For polymorphic species, different structures (e.g., diamond vs. graphite) possess different properties such as structural stability and mechanical hardness;50, 51 and these discrepancies may be similarly used to distinguish the single-crystal-like and polycrystalline vaterites. As for the polarization measurements, the Raman v1 mode of single-crystal-like hexagonal bifrustums has a much lower depolarization ratio (ρ~0.2) than that of the comparative polycrystalline spherulites (ρ~0.5) (Supporting Information, Figure S4 and Table S1). These indicate that the Raman v1 mode of vaterite is polarized mode and the spatial configuration of carbonate molecule of singlecrystal-like sample is more symmetric than that of the polycrystalline one. Temperature-varying Raman spectra (Figure 4) and combined TGA/DSC results (Figure 5) further prove that hexagonal bifrustums have a better structural stability than polycrystalline


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aggregates. The comparative Raman measurements show that the structural stabilities of singlecrystal-like and polycrystalline samples are different according to the initial appearance of spectral fluctuation within the temperature range of 100 and 500°C (Figure 4). Taking the Raman red-shift of vaterite lattice modes between 200 and 400 cm-1 into consideration (Supporting Information, Figure S5), keeping half an hour at each temperature exerts a great influence on the lattice structures of the two samples. In detail, both of the lattice modes gradually broaden in wavenumber and the different red-shifts with the increasing temperature indicate a temperaturedependent discrepancy for their structural stabilities.

Figure 4. Temperature-varying Raman spectra and the magnified lattice modes of single-crystallike and polycrystalline vaterites: (a, b), single-crystal-like hexagonal bifrustums; (c, d), polycrystalline spherulites. In panels a) and c) the labeled dashed boxes highlight the comparative spectral fluctuations, and in panels b) and d) the marked dashed lines denote the comparative red shifts of lattice modes at ~290 cm-1.


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At high temperature, the solid-state phase transformation of polycrystalline vaterite to calcite should happen from particle surface to spherical interior, which can be facilely certified by one or two exothermic peak(s) in DSC curves appearing around 480oC.47, 52, 53 Prior to the final DSC endothermic peak of CaCO3→CaO transformation there is no peak for the singlecrystal-like sample (Figure 5a), but a DSC exothermic peak around 477oC for the polycrystalline sample (Figure 5b). This assures a relatively solid structure with less degree of disorder51 and a better structural stability of single-crystal-like vaterite hexagonal bifrustums than that of the polycrystalline aggregates. Furthermore, both the negligible weight loss before 600 oC (Figure 5a) and the reproducible EDS results (Supporting Information, Figure S6) confirm that there are nearly no residual surfactants in the final product of vaterite hexagonal bifrustums.

Figure 5. TGA/DSC profiles obtained with a heating rate of 10oC min-1 from room temperature to 800oC: (a), single-crystal-like vaterite hexagonal bifrustums; (b), polycrystalline vaterite spherulites. Biomimetic Mineralization Process. In order to figure out the specific mineralization process of these “single crystals”, time-dependent experiments were performed and the corresponding


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XRD patterns and FT-IR spectra are shown in Supporting Information, Figure S7a and S7b, respectively. The intermediate sample obtained at 2 d mainly displays the XRD and FT-IR characteristics similar to those of the powdered mixture of CTAOH and Ca(DS)2, the results of the precipitate collected at 5 d indicate the co-existence of the raw materials (i.e., catanionic surfactants) and hexagonal vaterites, and the final sample shows only the XRD and FT-IR characteristics of crystalline vaterites produced at a reaction interval of 10 d.

Figure 6. SEM and TEM images and corresponding SAED patterns of vaterite samples obtained at various reaction times: (a-c), 2 d; (d-f), 3 d; (g-i), 4 d; (j-l), 5 d. By focusing electron beam on


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the selected regions marked by red dash-circles, the corresponding SAED patterns were obtained (scale bar = 5 nm-1). With the reaction time less than 2 d, paper-like self-assemblies of cationic surfactant CTAOH and anionic surfactant Ca(DS)2 can be easily observed (Figure 6a). Prior to a possibly confined crystallization in hydrophobic domains, multilayer organic (surfactants’ hydrocarbon-chains)inorganic (e.g., ammonia and calcium hydroxide) hybrids have been successfully proved to possess a separation of ~3.3 nm41 (Figure 6b, c). After aging for 24 h, most of multilayer “papers” roll up to form well-defined multi-walled nanotubes owing to both the hydrophobic interaction of catanionic surfactants and the solidification of polymeric Ca(OH)2 (~1 µm in length) (Figure 6d, e), which could be regarded as “precursors”

41

. Selected area electron

diffraction (SAED) pattern reveals the initial crystallization of vaterite within multilayer hybrids (Figure 6f). Both the lamellar self-assemblies and the occasionally captured vaterite platelets (Figure 6g, h and Supporting Information, Figure S8) could be completely destroyed by the exsitu electron beam irradiation. Therefore, it is very difficult to trace the generally polymorphic selectivity of vaterite nuclei and the subsequent shape evolution of hexagonal bifrustums. At an incubation time of ~5 d, the mass production of both hexagonal platelets (~500 nm in size) and multi-walled organic-inorganic nanotubes can be achieved. By focusing the electron beam on a vaterite hexagon, the obtained SAED pattern clearly presents hexagonal reflections and indicates the (00.1) crystal plane of “single-phase” h-vaterite (Figure 6h, i). Especially, there are two extra diffraction spots between the origin and (11.0) spot, and the weak superlattice reflections indicate the existence of some degree of long-range ordering (Figure 6i, l).5, 23, 25, 54 As described in the previous Ref. 41, the continuous crystal growth results in a big separation of 6.6 nm for lamellar organic-inorganic hybrids. Therefore, a large hexagonal platelet (~3.8 µm)


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and the broken parts of multi-walled nanotubes can be simultaneously observed at 5 d (Figure 6j, k), also giving the similar SAED pattern (Figure 6l) and corresponding irradiation phenomenon to those shown in Supporting Information, Figure S8.

Figure 7. A schematic illustration of formation process adopted for single-crystal-like vaterite hexagonal bifrustums: (1), rolling up of the self-assembled lamellar precursors accompanied by random nucleation of vaterite; (2), disintegration of multi-walled nanotubes accompanied by the selective nucleation for (00.1)-manifest hexagonal platelets; (3), crystal growth for final products. According to these experimental results, a probable formation mechanism of single-crystallike hexagonal bifrustums may be factitiously divided into four stages as shown in Figure 7. The first stage is the initial self-assembling of lamellar organic-inorganic hybrids with Et2CO3 solubilized in the hydrophobic domains and Ca2+ ions (or polymeric Ca(OH)2) enriched at the organic-inorganic interfaces (Figure 7, stage 1). As reported previously,41 the paper-like precursors further roll up into the multi-walled nanotubes, whose shells are composed of surfactant bilayers (i.e., hydrophobic domains) with an inorganic separation (hydrophilic


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domains). At the same time, with the slowly alkali-catalyzed hydrolysis of Et2CO3 at organicinorganic interfaces, the gradually increasing CO32- ions lead to the local supersaturation for the selective nucleation of vaterite (Figure 7, stage 2). The achievement of selective nucleation for hexagonal structure is possibly due to a situation that both the positively (i.e., Ca2+-enriched) and negatively charged (i.e., CO32--enriched) {00.1} crystal faces of “single-phase” h-vaterite12 can be effectively stabilized through the specific adsorption of surfactant-ions and/or ammonium cations. Rapidly after the nucleation, the corresponding crystal growth induces the “initial” emerging of the middle largest (00.1)-manifest platelets (Figure 7, stage 3). The base-catalyzed hydrolysis of Et2CO3 solubilized in the hydrophobic domains causes the continuous consumption of polymeric Ca(OH)2. That is, the further crystal growth of vaterite platelets change the aggregation states of these catanionic surfactants and then induces the complete disappearance of tubular intermediates.41 This should decrease supersaturation for the horizontal crystal growth in hydrophilic domains and the released DS- anions may react with the cations of CTA+ and NH4+, completely resulting in the rarely seen hexagonal bifrustums (Figure 7, stage 4). Through the rinse using water and then ethanol, the adsorbed catanionic surfactants could be removed completely. When Et2CO3 was added into the catanionic surfactant system once for all, growth rates of a tiny vaterite nucleus along each direction may lose control and then develop into pseudohexagonal bipyramids with irregular edges and growth steps (Figure 1d-f). Presumably, the absence of CTAOH gives a higher DS- effective concentration for the selective nucleation, resulting in the generation of ultra-thin hexagonal bifrustums (Figure 1g-i). Moreover, this formation mechanism could be supported by the catanionic surfactant-assisted mineralization


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conducted in an open system (Supporting Information, Figure S9a, b). Therein, both the gradual evaporating of solvent and simultaneously slow uptake of gaseous CO2 from air may provide experimental evidence for the mineralization process (Supporting Information, Figure S9c-e). CONCLUSIONS In summary, we have successfully prepared single-crystal-like vaterite hexagonal bifrustums (i.e., truncated hexagonal bipyramids or tetrakaidecahedra) for the first time using an aqueous reaction system of anionic surfactant Ca(DS)2, cationic surfactant CTAOH, ammonia and Et2CO3 at 60oC. Regardless of the recently recognized carbonate-rational polymorphism of vaterite itself, these single-crystal-like hexagonal bifrustums confidently possess a Raman doublet in the v1 region of 1070-1110 cm-1, a low depolarization ratio (~0.21) and a high structural stability. Therefore, there is still a long way to fabricate the absolutely single-phase vaterite and to reveal its structural properties.

ASSOCIATED CONTENT Supporting

Information.

SEM

images

of

single-crystal-like

vaterite,

polarization

measurements, the effect of electron-beam irradiation, the XRD patterns and SEM images of the samples obtained from experimental controls, the XRD patterns and FT IR spectra of the samples obtained from time-dependent experiments and the SEM images of vaterite obtained from an open system. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION


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Corresponding Author * Email: [email protected]. Present Addresses 1

A present Ph. D. candidate at the University of Alberta.

†

Shandong University.

‡

Chinese Academy of Sciences.

Author Contributions The manuscript was written through contributions of all authors. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT A financial support from Beijing National Laboratory for Molecular Science is greatly acknowledged. Authors want to express great thanks to Prof. Dr. Jillian M. Buriak and Dr. Jeremy Bau (University of Alberta, Canada) for valuable comments. REFERENCES (1) Shir, I. B.; Kababya, S.; Katz, I.; Pokroy, B.; Schmidt, A. Exposed and Buried Biomineral Interfaces in the Aragonitic Shell of Perna canaliculus Revealed by Solid-State NMR. Chem. Mater. 2013, 25, 4595-4602.


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(2) Ariani, A. P.; Wittmann, K. J.; Franco, E. A Comparative study of Static Bodies in Mysid Crustaceans: Evolutionary Implications of Crystallographic Characteristics. Biol. Bull. 1993, 185, 393-404. (3) Falini, G.; Fermani, S.; Vanzo, S.; Miletic, M.; Zaffino, G. Influence on the Formation of Aragonite or Vaterite by Otolith Macromolecules. Eur. J. Inorg. Chem. 2005, 2005, 162167. (4) Kanakis, J.; Malkaj, P.; Petroheilos, J.; Dalas, E. The Crystallization of Calcium Carbonate on Porcine and Human Cardiac Valves and the Antimineralization Effect of Sodium Alginate. J. Crystal Growth 2001, 223, 557-564. (5) Kabalah-Amitai, L.; Mayzel, B.; Kauffmann Y.; Fitch A. N.; Bloch L.; Gilbert P. U. P. A.; Pokroy B. Vaterite Crystals Contain Two Interspersed Crystal Structures. Science 2013, 340, 454-457. (6) Giralt, S.; Julià, R; Klerkx, J. Microbial biscuits of Vaterite in Lake Issyk-Kul (Republic of Kyrgyzstan). J. Sediment. Res. 2001, 71, 430-435. (7) Hu, Q.; Zhang, J.; Teng, H.; Becker, U. Growth Process and Crystallographic Properties of Ammonia-Induced Vaterite. Am. Mineral. 2012, 97, 1437-1445. (8) Cantaert, B.; Verch, A.; Kim, Y.; Ludwig, H.; Paunov, V. N.; Kröger, R.; Meldrum, F. C. Formation and Structure of Calcium Carbonate Thin Films and Nano-fibers Precipitated in the Presence of Poly(Allylamine Hydrochloride) (PAH) and Magnesium Ions. Chem. Mater. 2013, 25, 4994-5003. (9) Wei H.; Shen Q.; Wang H.; Gao Y.; Zhao Y.; Xu D.; Wang D. Influence of Segmented Copolymers on the Crystallization and Aggregation of Calcium Carbonate. J. Crystal Growth 2007, 303, 537-545.


21

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

(10) Zhan, J.; Lin, H.; Mou, C. Biomimetic Formation of Porous Single-Crystalline CaCO3 via Nanocrystal Aggregation. Adv. Mater. 2003, 15, 621-623. (11) Wang, F.; Richards, V. N.; Shields, S. P.; Buhro, W. E. Kinetics and Mechanisms of Aggregative Nanocrystal Growth. Chem. Mater. 2014, 26, 5-21. (12) Xu, A.; Antonietti, M.; Cölfen, H.; Fang, Y. Uniform Hexagonal Plates of Vaterite CaCO3 Mesocrystals Formed by Biomimetic Mineralization. Adv. Funct. Mater. 2006, 16, 903-908. (13) Song, R.; Cölfen, H. Mesocrystals—Ordered Nanoparticle Superstructures. Adv. Mater. 2010, 22, 1301-1330. (14) Pouget E. M.; Bomans P. H. H.; Goos J. A. C. M.; Frederik P. M.; With G. de; Sommerdijk N. A. J. M. The Initial Stages of tTemplate-Controlled CaCO3 Formation Revealed by CryoTEM. Science 2009, 323, 1455-1458. (15) Heywood, B. R.; Rajam, S.; Mann, S. Oriented Crystallization of CaCO3 under Compressed Monolayers part 2.—Morphology, Structure and Growth of Immature Crystals. J. Chem. Soc. Faraday Trans. 1991, 87, 735-743. (16) Rajam, S.; Heywood, B. R.; Walker, J. B. A.; Mann, S. Oriented Crystallization of CaCO3 under Compressed Monolayers part 1.—Morphological Studies of Mature Crystals. J. Chem. Soc. Faraday Trans. 1991, 87, 727-734. (17) Wagterveld, R. M.; Miedema; H.; Witkamp, G. Effect of Ultrasonic Treatment on Early Growth During CaCO3 Precipitation. Gryst. Growth Des. 2012, 12, 4403-4410. (18) Nishida, I. Precipitation of Calcium Carbonate by Ultrasonic Irradiation. Ultrason. Sonochem. 2004, 11, 423-428. (19) Sims, S. D.; Didymus, J. M.; Mann, S. Habit Habit Modification in Synthetic Crystals of Aragonite and Vaterite. J. Chem. Soc., Chem. Commun. 1995, 1031-1032.


22

Page 23 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(20) Demichelis, R.; Raiteri, P.; Gale, J. D.; Dovesi, R. The Multiple Structures of Vaterite. Cryst. Growth Des. 2013, 13, 2247-2251. (21) Mugnaioli E.; Andrusenko I.; Schüler T.; Loges N.; Dinnebier R. E.; Panthöfer M.; Tremel W.; Kolb U. Ab initio Structure Determination of Vaterite by Automated Electron Diffraction. Angew. Chem. Int. Ed. 2012, 51, 7041-7045. (22) Wehrmeister U.; Soldati A. L.; Jacob D. E.; Häger T.; Hofmeister W. Raman Spectroscopy of Synthetic, Geological and Biological Vaterite: a Raman Spectroscopic Study. J. Raman Spectrosc. 2010, 41, 193-201. (23) Kamhi, S. R. On the Structure of Vaterite, CaCO3. Acta Cryst. 1963, 16, 770-772. (24) Wang, J.; Becker, U. Structure and Carbonate Orientation of Vaterite (CaCO3). Am. Mineral. 2009, 94, 380-386. (25) Bail, A. L.; Ouhenia, S.; Chateigner, D. Microtwinning Hypothesis for a More Ordered Vaterite Model. Powder Diffr. 2011, 26, 16-21. (26) Meyer, H. J. Struktur und Fehlordnung des Vaterits. Z. Kristallogr. 1969, 128, 183-212. (27) Demichelis, R.; Raiteri, P.; Gale, J. D.; Doversi, R. A New Structural Model for Disorder in Vaterite from First-Principles Calculations. CrystEngComm 2012, 14, 44-47. (28) Behrens, G.; Kuhn, L. T.; Ubic, R.; Heuer, A. H. Raman Spectra of Vateritic Calcium Carbonate. Spectrosc. Lett. 1995, 28, 983-995. (29) Pokroy, B.; Zolotoyabko, E.; Adir, N. Purification and Functional Analysis of a 40 kD Protein Extracted from the Strombus decorus persicus Mollusk Shells. Biomacromolecules 2006, 7, 550-556. (30) Seto, J.; Azaïs, T.; Cölfen, H. Formation of Aragonitic Layered Structures from Kaolinite and Amorphous Calcium Carbonate Precursors. Langmuir 2013, 29, 7521-7528.


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Page 24 of 27

(31) Schüler T.; Tremel W. Versatile Wet-Chemical Synthesis of Non-Agglomerated CaCO3 Vaterite Nanoparticles. Chem. Commun. 2011, 47, 5208-5210. (32) Cantaert B.; Kim Y.; Ludwig H.; Nudelman F.; Sommerdijk N. A. J. M.; Meldrum F. C. Think Positive: Phase Separation Enables a Positively Charged Additive to Induce Dramatic Changes in Calcium Carbonate Morphology. Adv. Funct. Mater. 2012, 22, 907-915. (33) Anderson, A. Group Theoretical Analysis of the v1 (CO32-) Vibration in Crystalline Calcium Carbonate. Spectrosc. Lett. 1996, 29, 819-825. (34) Pouget E. M.; Bomans P. H. H.; Dey A.; Frederik P. M.; With G. de; Sommerdijk N. A. J. M. The Development of Morphology and Structure in Hexagonal Vaterite. J. Am. Chem. Soc. 2010, 132, 11560-11565. (35) Huang, J. H.; Mao, Z. F.; Luo, M. F. Effect of Anionic Surfactant on Vaterite CaCO3. Mater. Res. Bull. 2007, 42, 2184-2191. (36) Xu, A.; Dong, W.; Antonietti, M.; Cölfen, H. Polymorph Switching of Calcium Carbonate Crystals by Polymer-Controlled Crystallization. Adv. Func. Mater. 2008, 18, 1307-1313. (37) Gehrke, N.; Cölfen, H.; Pinna, N.; Antonietti, M.; Nassif, N. Superstructures of Calcium Carbonate Crystals by Oriented Attachment. Cryst. Growth Des. 2005, 5, 1317-1319. (38) Pastero L.; Costa E.; Bruno M.; Rubbo M.; Sgualdino G.; Aquilano D. Morphology of Calcite (CaCO3) Crystals Growing from Aqueous Solutions in the Presence of Li+ ions. Cryst. Growth Des. 2004, 4, 485-490. (39) Xiao J. X.; Zhu Y.; Liu Y.; Liu H.; Zeng Y.; Xu F.; Wang L. Vaterite Selection by Chitosan Gel: an Example of Polymorph Selection by Morphology of Biomacromolecules. Cryst. Growth Des. 2008, 8, 2887-2891.


24

Page 25 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

(40) Liu F.; Gao Y.; Zhao S.; Shen Q.; Su Y.; Wang D. Biomimetic Fabrication of Pseudohexagonal Aragonite Tablets through a Temperature-Varying Approach. Chem. Commun. 2010, 46, 4607-4609. (41) Liu F.; Kang W.; Zhao C.; Su Y.; Wang D.; Shen Q. Integrative and Intermediate SelfAssembly of Multi-Walled Hybrid Nanotubes for Catanionic Biomimetics. Chem. Commun. 2011, 47, 12482-12484. (42) Schenk, A. S.; Cantaert, B.; Kim, Y.; Li, Y.; Read, E. S.; Semsarilar, M.; Armes, S. P.; Meldrum, F. C. Systematic Study of the Effects of Polyamines on Calcium Carbonate Precipitation. Chem. Mater. 2014, 26, 2703-2711. (43) Shen, Q.; Wang, L.; Li, X.; Liu, F. Biomimetic Synthesis of Calcium Carbonate Polymorphs using the Lamellar Lyotropic Liquid Crystalline Systems of Calcium Dodecyl sulfate. Cryst. Growth Des. 2008, 8, 3560-3565. (44) Shen, Q.; Hao, W.; Zhou, Y.; Huang, Y.; Yang, H.; Wang, D.; Xu, D. Properties of Amorphous Calcium Carbonate and the Template Action of Vaterite Spheres. J. Phys. Chem. B 2006, 110, 2994-3000. (45) Wu L.; Zhu J.; Xiao D.; Zhu J.; Tan J.; Zhang Q. Preparation and Properties of Highly (100)-Oriented Pb(Zr0.2Ti0.8)O3 Thin Film Prepared by rf Magnetron Sputtering with a PbOx Buffer Layer. J. Appl. Phys. 2007, 101, 094107-094107-5. (46) Shen Q.; Wei H.; Wang L.; Zhou Y.; Zhao Y.; Zhang Z.; Wang D.; Xu G.; Xu D. Crystallization and Aggregation Behaviors of Calcium Carbonate in the Presence of Poly(vinylpyrrolidone) and Sodium Dodecyl Sulfate. J. Phys. Chem. B 2005, 109, 1834218347.


25

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Page 26 of 27

(47) Rao, M. S. Kinetics and Mechanism of the Transformation of Vaterite to Calcite. B. Chem. Soc. Jan. 1973, 46, 1414-1417. (48) Wei, H.; Shen, Q.; Zhao, Y.; Wang, D.; Xu, D. Influence of Polyvinylpyrrolidone on the Precipitation of Calcium Carbonate and on the Transformation of Vaterite to Calcite. J. Crystal Growth 2003, 250, 516-524. (49) Gabrielli C.; Jaouhari R.; Joiret S.; Maurin G. In situ Raman spectroscopy applied to electrochemical scaling. Determination of the structure of vaterite. J. Raman Spectrosc. 2000, 31, 497-501. (50) Dunitz, J. D.; Bernstein, J. Disappearing Polymorphs. Acc. Chem. Res. 1995, 28, 193-200. (51) Falini, G.; Fermani, S.; Reggi, M.; Džakula, B. N.; Kralj, D. Evidence of structural variability among synthetic and biogenic vaterite. Chem. Commun. 2014, 50, 15370-15373. (52) Maciejewski, M.; Oswald, H.; Reller, A. Thermal transformations of vaterite and calcite. Thermochim. Acta 1994, 234, 315-328. (53) Nassrallah-Aboukaïs, N.; Jacquemin, J.; Decarne, C.; Abi-Aad, E.; Lamonier, J. F.; Aboukaïs, A. Transformation of vaterite into calcite in the absence and the presence of copper(II) species. J. Therm. Anal. Cal. 2003, 74, 21-27. (54) Dupont, L.; Portemer, F.; Figlarz, M. Synthesis and study of a well crystallized CaCO3 vaterite showing a new habitus. J. Mater. Chem. 1997, 7, 797-800.


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TOC GRAPHIC


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Catanionic Surfactant-Assisted Mineralization and Structural

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