Search

Size and shape uniformity of nanomaterials are extremely important for their applications in batteries, supercapacitors, catalysis, etc. In the crystallization process, finding proper synthesis conditions is necessary to have control over size dispersion, as well as crystal planes. In this work, we synthesized Cu2O rhombic dodecahedra (exposing 12 {110} planes) with size range from 1351 nm to 142 nm at a reaction temperature of 31–60 °C. The main parameters governing the size of Cu2O were the concentration of the precursor species and reduction reaction, which were affected by a given temperature. Results of crystallization experiments indicated that reaction and crystallization kinetics were mainly enhanced by raised temperature. Serving as lithium ion battery anodes, Cu2O rhombic dodecahedra showed higher capacity than cubes and octahedra. This work gives us a way of optimizing the temperature conditions for obtaining size uniformity of nanomaterials. [ABSTRACT FROM AUTHOR]

A chemical bonding model is established to describe the chemical potential decrease during crystallization. In the nucleation stage, in situ molecular vibration spectroscopy shows the increased vibration energy of constituent groups, indicating the shortened chemical bonding and the decreased chemical potential towards the formation of nuclei. Starting from the Gibbs free energy formula, the chemical potential decrease during crystallization is scaled, which depends on the released chemical bonding energy per unit phase transition zone. In the crystal growth, the direction-dependent growth rate of inorganic single crystals can be quantitatively determined, their anisotropic thermodynamic morphology can thus be constructed on the basis of relative growth rates. [ABSTRACT FROM AUTHOR]

A general and programmed fast crystallization process (about 12 seconds) was designed to synthesize binary (MOx) and ternary (ABO3, A2BO4) metal oxide nanomaterials with controllable sizes and composition. The fast crystallization process mainly included the burning of metal-nitrate–filter-paper without additional energy supply and it can lead to the formation of exceptionally fine binary and ternary crystallites with sizes of ∼10–20 nm. The thermodynamic reduction potential of the metal-nitrate–filter-paper burning system can be estimated to be between −0.26 and 1.72 V, which can favor the occurrence of redox reactions, i.e. Cu2+→ Cu+→ Cu, Ni2+→ Ni, Co2+→ Co3+, Ce3+→ Ce4+, and Pr3+→ Pr4+. When used as anode materials for lithium-ion batteries, most of the as-burned metal oxides displayed high cycling stability. The discharge capacity of CoO nanoparticles can reach as high as 501.1 mA h g−1 after continuous 50 discharge–charge cycles at a current density of 100 mA g−1. The proposed fast crystallization route provided a versatile, facile and fast method for the synthesis of functional metal oxide nanomaterials with controllable sizes and composition. [ABSTRACT FROM AUTHOR]

The effects of crystallization on the formation of geochemical, biological, and synthetic materials have been motivating decades of research into crystal nucleation and growth processes. The development of crystal growth theories and models can deepen the understanding of physicochemical interactions during the crystal growth process, which facilitates the designing of crystallization approaches in material production. The chemical bonding theory of single crystal growth emphasizes the dominant role of dynamic chemical bonding mechanisms at the growing interfaces. In this paper, we highlight the chemical bonding theory of single crystal growth from the chemical reaction viewpoint, by focusing on the atomic level of the growing interface between the liquid and crystal phases. Using ZnO, CeO2, MnO2 and Y3Al5O12 as examples, we review some typical applications of the chemical bonding theory of single crystal growth in calculating crystal habits, evaluating crystal properties, and guiding practical single crystal growth. Microscopically speaking, the essence of crystal growth and design is to create ideal chemical bonding architectures at both the crystal surface and the growing interface via both thermodynamic and kinetic strategies. [ABSTRACT FROM AUTHOR]

MnCO3 precursors with different morphologies were crystallized using three kinds of surfactants as soft templates, i.e., cation surfactant cetyl trimethyl ammonium bromide (CTAB), anion surfactant sodium dodecyl sulfate (SDS) and neutral poly(vinyl pyrrolidone) (PVP). When PVP was used, the reaction manner was changed from only stirring at room temperature to a hydrothermal route. Under hydrothermal conditions, different ethanol/water ratios and sources of CO32− (NaHCO3 and urea) were used. Porous cubic, regular spherical and nut-like spherical Mn2O3 samples can be obtained by a simple post-annealing process. The correlation between the morphology of Mn2O3 and its performance as an anode material for Li-ion batteries was evaluated. The nut-like spherical Mn2O3 sample has the best cycling performance, with a specific discharge capacity of 925 mA h g−1 at a current density of 100 mA g−1 after 180 cycles. The sample composed of cubes and spheres has superior rate performance. The specific discharge capacity decreases with increasing current density from ~872 mA h g−1 at 100 mA g−1 to ~361 mA h g−1 at 2000 mA g−1. [ABSTRACT FROM AUTHOR]

Both the crystallizing molecule without long-range ordered arrangement and the complex interactions between solvent, anti-solvent, and molecule crystal challenge the imaging of molecule configurations during anti-solvent crystallization. Here, the structural evolution of NH4H2PO4 during anti-solvent crystallization was tracked by in situ ATR-IR spectroscopy. The NH4H2PO4 molecule undergoes D2d→C2v→D2d or C2v→D2d during anti-solvent crystallization, depending on both V(H2O)/V(ethanol) ratio and the concentration of NH4H2PO4 aqueous solution. Moreover, IR spectroscopy can also be used to confirm the anti-solvent role of ethanol in the NH4H2PO4–H2O–ethanol crystallization system. The volatilization of ethanol has been demonstrated as an effective approach to control the dissolution process of NH4H2PO4, which can be used to study the crystallization–dissolution–recrystallization process. The present study can shed light on the anti-solvent crystallization physical and chemistry of NH4H2PO4 from a molecule-level viewpoint. [ABSTRACT FROM AUTHOR]

In this work, we designed a simple hydrolysis reaction to study the chemical roles of anions with different chemoaffinity abilities to iron ions on the crystallization of FeOOH. FeOOH products with different morphologies and sizes can be crystallized by using commercial iron salts such as FeSO4, FeCl2, FeCl3 and Fe(NO3)3. Their crystallization mechanisms can be evidenced in terms of hard–soft acid–base theory, which can control the chemical reaction and crystallization process. Herein, FeOOH particles with high electroactivity were successfully synthesized at 80 °C via the use of a single-source of iron salt in each corresponding experiment without adding any other reagents. The as-obtained FeOOH samples exhibit high specific capacitances of 441.2, 385.7, 577.3 and 619.6 F g−1, which show good potential to be candidates as high performance electrode materials for supercapacitors. Moreover, this facile synthesis method provides a huge opportunity for future practical applications of supercapacitors. [ABSTRACT FROM AUTHOR]

In the present work, size-tunable Fe2O3 microspindles were crystallized by a simple feasible ethylenediamine (EN) ligand-controlled hydrothermal approach. The size of Fe2O3 microspindles can be controlled from several hundreds of nanometers to above 1 micrometer. Fe2O3 particles with spindle-like structure can be controlled well via the assistance of EN. A clear growth pathway of the EN-assisted synthesis of Fe2O3 microspindles was illustrated by us. As-obtained Fe2O3 microspindles in different sizes exhibit high specific capacitance values of 558.7, 496.6, 504.7 and 271.0 F g−1, which are much higher than previous reported results. The smaller size of Fe2O3 microspindles can lead to higher specific capacitance. [ABSTRACT FROM AUTHOR]

Crystallographically, KDP and ADP have familiar ( H 2 PO 4 - ) n framework, which is formed via hydrogen bonding between H 2 PO 4 - groups along main crystallographic axes. The common characteristics of both KDP and ADP crystallization behaviours are studied from the viewpoint of ( H 2 PO 4 - ) n framework. On the basis of chemical bonding theory of single crystal growth, the anisotropic hydrogen bonding in ( H 2 PO 4 - ) n framework and the chemical bonding between K + / NH 4 + and ( H 2 PO 4 - ) n dominate the anisotropic thermodynamic equilibrium morphology of KDP and ADP. The thermodynamic equilibrium morphology is used to find out the possible preferential growth directions for the dendrite growth of both KDP and ADP, i.e., 〈1 0 0〉 and 〈1 0 1〉 directions. IR spectroscopy of both KDP and ADP solutions with different concentrations has testified our theoretical results, which shows that H 2 PO 4 - ions are initially form ( H 2 PO 4 - ) n framework, and then constituent cations inset into the ( H 2 PO 4 - ) n framework during both KDP and ADP crystallization processes. The present work can provide helpful basic information for the study of crystallization of MH 2 XO 4 crystal family. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel concept of ionic pseudocapacitor was proposed. [•] Crystallization of YbCl3 in alkaline electrolyte leads to highly electrochemical reactive YbOOH colloids. [•] Crystallization proceeds under chemical coprecipitation and Faradaic redox reactions in YbCl3-KOH supercapacitor system. [•] YbCl3 pseudocapacitors can show ultrahigh capacitance of 2210F/g, and commercial YbCl3 salts can be directly used. [Copyright &y& Elsevier]

Highlights: [•] The hydrogen bonding nature during ADP crystallization is studied. [•] The crystallographic structures of and in ADP crystal are discussed. [•] The hydrogen bonding of and is recorded by in situ IR spectrum. [•] Anisotropic chemical bonding conditions dominate ADP crystal morphology. [•] ADP crystal morphologies with different clusters are calculated. [Copyright &y& Elsevier]

Currently, one of the biggest challenges in the field of pseudocapacitors is their capacitance value. Current knowledge on improving specific capacitance values is mainly focused on the synthesis of electrode materials with different structures and sizes. However, no studies have addressed using soluble inorganic salts directly as electrode materials. For the first time, we have reported that water-soluble CuCl2 electrodes show a fast and reversible redox reaction of Cu2+↑ Cu+ and deliver a very high specific pseudocapacitance, ~5442 F g−1. We have identified that the cation Cu2+ is responsible for achieving this big number. The chemical and crystallization transformation of the CuCl2 electrode is presented. Commercial inorganic salts can be used directly as electrodes neglecting complex synthesis procedures, which is an easily scalable and highly economical method. This method can be extended to a large variety of commercial inorganic salt electrodes following the guideline of ionic electronegativity. [ABSTRACT FROM AUTHOR]

Crystallization of hopper-like Cu2O cubes is demonstrated in alkaline citrate-copper solution upon the equilibrium between complexation, precipitation and redox reactions. The complexation reactions of Na3cit and NaOH with Cu2+ manipulate the current chemical reaction routes, phase transformation, and thus crystallization morphologies and compositions. During the crystallization of Cu2O variations of mother solution such as pH and the concentration of Cu2+ (Cu+) are monitored by ex situ pH measurement and UV-Vis absorption spectroscopy. The shape evolution of Cu2O hopper cubes is consistent with the chemical reaction routes, which demonstrates the interplay between chemical reactions and crystal growth. The appropriate reaction concentration, Na3cit:Cu2+ > 2 and 1 < NaOH:Cu2+ < 2, has been identified for the growth of these hopper cubes. The current reaction-controllable crystal growth may further the synthesis chemistry toward rational control over crystallization. [ABSTRACT FROM AUTHOR]

Crystallization of KDP-family crystals depends on the chemical bonding behavior of the crystal constituents in aqueous solution, which are sensitive to solution conditions. We applied in situ ATR-IR spectroscopy combined with a morphology-evolution calibration to declare the structural dynamics of NH4+ and H2PO4− during the NH4H2PO4 crystallization in aqueous solution with different concentrations and pH values. For unsaturated NH4H2PO4 solution, both the H2PO4− stretching vibration mode and NH4+ bending vibration mode are enhanced with increasing concentration. When the NH4H2PO4 solution becomes a saturated and then supersaturated and crystalline state, H2PO4− ions undergo hydrated dimerisation and polymerisation, which can be recorded by the appearance and red shift of the P–O…H–O–P in-plane bending vibration mode from 1250 to 1263 cm−1. During this process, hydrated NH4+ ions bind to the (H2PO4−)n frame, reflected by the splitting of the HN4+ bending vibration mode at 1450 and 1400 cm−1. For the supersaturated NH4H2PO4 solution, HPO42− and H2PO4− coexist in solution with increasing pH value up to 6.64, whereas H3PO4 and H2PO4− coexist with decreasing pH value down to 1.52. Such an in situ recording strategy is of particular value in studying system dynamics, and in general to monitor the solution concentrations and compositions before and during the crystallization process. [ABSTRACT FROM AUTHOR]

Abstract: In this article, we briefly summarized our recent work on the studies of crystallization and functionality of inorganic materials. On the basis of the chemical bonding theory of single crystal growth, we can quantitatively simulate Cu2O crystallization processes in solution system. We also kinetically controlled Cu2O crystallization process in the reduction solution route. Lithium ion battery and supercapacitor performances of some oxides such as Co3O4 and MnO2 were shown to elucidate the important effect of crystallization on functionality of inorganic materials. This work encourages us to create novel functionalities through the study of crystallization of inorganic materials, which warrants more chances in the field of functional materials. [Copyright &y& Elsevier]

Rapid development of nanomaterials with their outstanding physical/chemical properties and subsequently extraordinary functions indicates that nanoscience and nanotechnology are no longer unacquainted in our daily life. However, exquisitely controlling the crystallization of nanomaterials, building complex architecture and nanodevices, and finally realizing their practical applications still remain challenges in improving our civilization. Starting from the challenges in the crystallization of nanomaterials which acts as the cornerstone of their practical applications, we review recent advances in crystallization strategy, formation mechanism, and theoretical modeling of nanomaterials. Considering the significant role of chemical bonding in both reaction and crystallization processes, we emphasize that exquisite fabrication of nanomaterials can be realized by essentially controlling the bonding processes during crystallization. [ABSTRACT FROM AUTHOR]

Sodium niobate (NaNbO3) microcrystals were crystallized by a technically flexible ion exchange method in solution phase. A potassium niobate hollow sphere (KNHS) precursor was first grown viaa hydrothermal route, the metastable compound is chemically active in NaOH solution, leading to the crystallization of NaNbO3microcrystals by a spontaneous ion exchange and recrystallization process. The crucial influences of ion exchange duration, NaOH concentration, surfactant, and reaction medium (water, ethylene glycol/water, ethylenediamine/water) on both the morphology and crystal phase of the NaNbO3microcrystals have also been established. This current chemical route provides an extremely simple, mild, and effective recipe to crystallize NaNbO3, which could possibly be expanded to more niobate crystals with well controlled chemical compositions, structures, and particle morphologies. [ABSTRACT FROM AUTHOR]

Nanostructured materials with controlled architectures are desirable for many applications, among which, metal oxides are especially important in optics, electronics, biology, catalysis, and energy conversions. Various chemical routes have been widely investigated for the synthesis of nanostructured metal oxide particles and films. More recently, deliberately designed chemical strategies have been used to produce particles and films composed of more complex crystal structures. In this paper, we discuss some recent progresses in the design of complex nanostructures through chemical routes, emphasize particularly on metal oxides. We first review some basic concepts involved in the fabrication of complex nanostructures, including crystal nucleation and growth, shape controlling and ripening process. We then describe more recent work on the use of different methods to synthesize a wide range of complex nanostructures, including hierarchical structures, heterostructures, as well as oriented nanowires and nanotubes. Such purposely built materials are designed, and engineered to match the physical, chemical, and structural requirements of their applications. [ABSTRACT FROM AUTHOR]

Abstract: Three methods were employed to produce specific Mg(OH)2 (MH) granules with improved filtration efficiency, using crystallization technique. A buffer solution was utilized to improve the crystallization of MH, the spherical assembly composed of both nanosheets and hollow microspheres was obtained. A hydrothermal treatment of amorphous MH led to MH hexagonal nanoplates. In a directing growth, SO4 2− ions were found to strongly improve the crystallization of MH. In the current work, one-dimensional 5Mg(OH)2·MgSO4 ·2H2O whiskers and MH microspheres can be crystallized on a large scale. The filtration tests show that these specific MH granules have improved filtration properties. The current work opens up a new avenue for the production of MH granules, and the optimal filtration efficiency offers a significant control over the quality of MH-type products. [Copyright &y& Elsevier]

Abstract: A novel rapid crystal growth system was conveniently constructed on the basis of the high-speed acquisition card and the Laboratory Virtual Instrument Engineering Workbench software. All growth parameters were real-time monitored and controlled to provide a stable environment with small fluctuation for crystal growth. A simple equation was derived from the solution properties to calculate the cooling curves corresponding to different growth parameters. The combination of the calculated cooling curve and our designed growth system can lead to the rapid growth of potassium dihydrogen phosphate crystal routinely. [Copyright &y& Elsevier]

Abstract: In this communication, we report the hexagonal ZnO taper-tubes prepared through an electroless deposition method in an acidic medium based on a modified galvanic replacement reaction. Inspection of SEM images of ZnO suggests a one-step, acetic acid in situ crystallization/etching mechanism for producing tubular ZnO arrays. During electroless deposition reaction, the formation process may be rationalized by considering that the etching of ZnO with acetic acid starts from six sites located at the six corners of the top surface of ZnO truncated taper, resulting in a gradual widening of the open holes and tubular ZnO. The present electroless deposition strategy is versatile and with a potential to be developed into a more practical method. [Copyright &y& Elsevier]

As an industry useful mineral, calcium sulfate crystal system including gypsum, bassanite, and anhydride, has numerous storage and widespread applications in our society. Controlling the process of gypsum formation and crystallization still remains a certain challenge under different conditions. In this work, an in-situ micro-Raman spectroscopy was used to explore the effect of chemical reaction on the crystallization process of gypsum (CaSO 4 ·2H 2 O). Under the conditions of equal molar volume reaction, it was found that the formation time and crystallization rate of gypsum were related to the reactant concentration, which showed us the driving force of chemical reaction kinetics and the chemical potential of crystallization. Excess reactants in the non-isomolecular reaction clearly modified the precipitation reaction and crystallization of gypsum, which were recorded by in-situ Raman spectral variations at molecular level. The whole process involves chemical reaction, amorphous precursor aggregation, nucleation and crystal growth, which may provide us solid evidences towards deeply clarifying the microscopic effect of chemical reaction on gypsum crystallization at molecular level. Image 1096643 • Crystallization process of gypsum solution with reaction of CaCl 2 and Na 2 SO 4 was monitored by in-situ micro-Raman spectroscopy. • Crystallization of gypsum related to isomolecular and non-isomolecular reaction. • Effect of chemical reaction on gypsum crystallization was identified at molecular level. [ABSTRACT FROM AUTHOR]

Abstract: On the basis of the crystal phase evolution from β-Ni(OH)2 to α-Ni(OH)2, α-Ni(OH)2, β-Ni(OH)2, and their mixed-phase structures were selectively crystallized at different stages during the hydrolysis of Ni(Ac)2 at hydrothermal conditions. We used both XRD characterization and SEM observation to clearly identify such a transformation process. Electrochemical tests indicate that the mixed-phase Ni(OH)2 obtained at 3h possesses the best capacitive performance among all as-obtained samples such as initially formed β-Ni(OH)2 nanosheet aggregates, mixed-phase Ni(OH)2 obtained at other reaction stages, and the ultimately formed α-Ni(OH)2 nanobelts. This phase selective route provides us an effective way to investigate the correlation between crystal phase composition of electrode materials and their capacitive performance. [Copyright &y& Elsevier]

Abstract: The challenge on lanthanide–transition-metal (Ln–M) coordination polymer crystals and a corresponding ligand-directed assembly strategy of crystal engineering were studied. The multifunctional isonicotinate with mixed donor sites was selected as the directing ligand to link lanthanide and transition-metal ions on the basis of the coordination nature of both different types of metal ions. A new three-dimensional (3D) Ln–M heterometallic coordination polymer crystal, Ce2(H2O)2(OAc)Cu4Cl3(IN)6 (1) (HIN=isonicotinic acid, HOAc=acetic acid), has been grown under hydrothermal crystal growth conditions and characterized by IR, UV–vis, photoluminescent spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. The crystal with sizes 0.8×0.2×0.2mm3, crystallizing in monoclinic C2/c space group, structurally exhibits a 3D coordination framework based on the linkage of 1D Ce−carboxylate chains and {Cu4Cl3} complexes with different geometries by IN ligands. The results show that current strategy can be used to design and grow novel heterometallic coordination polymer crystals. [Copyright &y& Elsevier]

Abstract: Hexagonal nanoplatelets of layered double hydroxide containing Mg2+ and Al3+ cations and anion (MgAl–CO3-LDH) were successfully synthesized via an ethylenediamine-assisted hydrothermal route. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), transmission electron microscope (TEM), and UV–vis diffuse reflectance spectrum, respectively. The results show that ethylenediamine not only inhibits impurity phases generated in the synthesis of MgAl–CO3-LDH but also can effectively control the crystal size of MgAl–CO3-LDH in the range of 50−100nm. In particular, a possible formation mechanism of hexagonal nanoplatelet MgAl–CO3-LDH is proposed. The present work develops a simple and mild route to crystallize MgAl–CO3-LDH with hexagonal nanoplatelet morphology, which is a key engineering step toward its potential size-dependent applications. [ABSTRACT FROM AUTHOR]