Formation Of Mesocrystals Research Articles

Formation of nanoplate-based clew-like ZnO mesocrystals and their photocatalysis application

The formation mechanism of a nanoplate-based clew-like ZnO mesocrystal was found to be mainly by a nonclassical crystallization process.

Understanding the Role of Solvation Forces on the Preferential Attachment of Nanoparticles in Liquid.

Optimization of colloidal nanoparticle synthesis techniques requires an understanding of underlying particle growth mechanisms. Nonclassical growth mechanisms are particularly important as they affect nanoparticle size and shape distributions, which in turn influence functional properties. For example, preferential attachment of nanoparticles is known to lead to the formation of mesocrystals, although the formation mechanism is currently not well-understood. Here we employ in situ liquid cell scanning transmission electron microscopy and steered molecular dynamics (SMD) simulations to demonstrate that the experimentally observed preference for end-to-end attachment of silver nanorods is a result of weaker solvation forces occurring at rod ends. SMD reveals that when the side of a nanorod approaches another rod, perturbation in the surface-bound water at the nanorod surface creates significant energy barriers to attachment. Additionally, rod morphology (i.e., facet shape) effects can explain the majority of the side attachment effects that are observed experimentally.

Oriented Attachment of Cubic or Spherical BaTiO3Nanocrystals by van der Waals Torque

It has been believed that dipole–dipole interaction is the reason for the oriented attachment (OA) of nanocrystals if they have electric or magnetic dipoles. In this study, the role of van der Waals torque (Casimir torque) originated in dielectric anisotropy of a nanocrystal is numerically studied for the first time on OA of cubic or spherical BaTiO3 nanocrystals. The present numerical simulations of OA have indicated that the alignment of the crystal axes is mainly due to van der Waals torque when the crystal size is smaller than 5 nm both in aqueous and organic solutions with and without electric charge screening by ions, respectively. For larger crystals, the electric dipole–dipole interaction dominates. The mesocrystal formation of 5 nm BaTiO3 nanocrystals in aqueous solution is due to van der Waals torque.

Formation of Vaterite Mesocrystals in Biomineral-like Structures and Implication for Biomineralization

Vaterite mesocrystals with a hexagonal prism structure were successfully achieved in the presence of sodium citrate (SC) and sodium dodecyl benzenesulfonate (SDBS) by use of a gas-diffusion method at room temperature. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), nitrogen physisorption analysis, and field-emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray (EDX) were used to characterize the hexagonal prisms. XRD and FESEM results reveal that the superstructures are composed of hundreds of well-stacked nanoflakes, which construct the laminated hexagonal prism of vaterite. TEM and SAED analyses show that the hexagonal prism has the same crystallographic symmetry as single-crystal vaterite, confirming that the hexagonal prismatic architectures are orientationally aligned mesocrystals of vatreite. However, no hexagonal prism st...

Rutile TiO2 mesocrystals/reduced graphene oxide with high-rate and long-term performance for lithium-ion batteries.

An in situ hydrothermal route is developed for fabricating rutile TiO2 mesocrystals/reduced graphene oxide nanosheets (TGR) hybrids in the presence of dodecylbenzenesulphonic acid (ADBS). These rutile TiO2 mesocrystals with a Wulff shape are composed of ultra-tiny rod-like subunits with the same oriented direction and closely wrapped by the nanosheets of reduced graphene oxide (RGO). It is found that ADBS played a key role for the formation of mesocrystals during the self-assembly process, which pillared the graphene oxide (GO) nanosheets and involved the aggregation of the mesocrystal subunits. Furthermore, the TGR hybrids are used as an anode material and exhibited a large capacity over 150 mA h g−1 at 20 C after 1000 cycles, and high rate capability up to 40 C. These high performance characteristics may be due to the intrinsic characteristics of rutile TiO2 mesocrystals constructed from ultra-tiny subunits and hybridized with super conductive RGO nanosheets.

Ball Milling to Build the Hybrid Mesocrystals of Ibuprofen and Aragonite

Mesocrystal formation is one of the new paradigms of the nonclassical crystallization, where the assembly of crystal domains is observed. Also, it has been recently employed in studies on drug formulation to utilize controlled dissolution of the drug domains. In this report, ibuprofen was attempted to form hybrid mesocrystals with calcium carbonate crystals. Two polymorphs of calcium carbonate (aragonite and calcite) were used during the solid‐state process of ball milling. Structural analyses confirmed the mesocrystal formation of ibuprofen with aragonite but not with calcite. The origin of the observed behavior was found from the higher affinity of ibuprofen to aragonite, especially its (0 1 0) surface, compared to calcite. The hybrid mesocrystals of ibuprofen and aragonite showed the environment‐responsive release behavior, where the stability of aragonite was the controlling factor for the release kinetics of ibuprofen.

Insight into the formation of magnetite mesocrystals from ferrous precursors in ethylene glycol.

Uniform magnetite mesocrystals were fabricated by solvothermal treatment of ferrous chloride in ethylene glycol in the presence of sodium hydroxide. The formation mechanism of magnetite mesocrystals in ethylene glycol was deduced by a time-dependent experiment.

Formation of porous calcite mesocrystals from CO2–H2O–Ca(OH)2 slurry in the presence of common domestic drinks

Simple method to synthesize porous calcite mesocrystals by aqueous carbonation of portlandite in presence of common domestic drinks.

The many roles of mellitic acid during barium sulfate crystallization

The various roles of mellitic acid during barium sulfate crystallization from nucleation to mesocrystal formation are explored and elucidated.

Protein biomineralized nanoporous inorganic mesocrystals with tunable hierarchical nanostructures.

Mesocrystals with the symmetry defying morphologies and highly ordered superstructures composed of primary units are of particular interest, but the fabrication has proved extremely challenging. A novel strategy based on biomineralization approach for the synthesis of hematite mesocrystals is developed by using silk fibroin as a biotemplate. The resultant hematite mesocrystals are uniform, highly crystalline, and porous nanostructures with tunable size and morphologies by simply varying the concentration of the silk fibroin and iron(III) chloride in this biomineralization system. In particular, we demonstrate a complex mesoscale biomineralization process induced by the silk fibroin for the formation of hematite mesocrystals. This biomimetic strategy features precisely tunable, high efficiency, and low-cost and opens up an avenue to access new novel functional mesocrystals with hierarchical structures in various practical applications.

Endowing manganese oxide with fast adsorption ability through controlling the manganese carbonate precursor assembled in ionic liquid

Manganese oxides with desired structure are controllably obtained through annealing MnCO3 precursors with required structures. The structures of MnCO3 precursors are determined by a “mesocrystal formation” process in an ionic liquid system of a choline chloride/urea (CU) mixture. Without addition of surfactants, only CU solvent and manganese chloride are needed in the reaction system, in which the CU acts as reaction medium as well as control agent for particle growth. A shape transformation of MnCO3 particles from well-defined rhombohedral mesocrystals to ellipsoidal polycrystal ensembles, and to nanoparticulate aggregates is observed when heating the reaction system for 4h at 120, 150, and 180°C, respectively. With a longer aging time at 120°C, etching and disassembly of MnCO3 mesocrystals happened. The correlation between the microstructure and the underlying formation mechanism is highlighted. Porous and nanowire-like MnOx nanostructures are obtained through a facile thermal conversion process from the diverse MnCO3 precursors, which are demonstrated as effective and efficient adsorbents to remove organic waste (e.g. Congo red) from water. Significantly, the nanowire-like MnOx nanostructures obtained by annealing the MnCO3 mesocrystals at 300°C for 4h can remove about 95% Congo red in waste water at room temperature in only one minute, which is superior to the reported hierarchical hollow nanostructured MnO2.

Facile synthesis of tetrahedral Ag3PO4 mesocrystals and its enhanced photocatalytic activity

A novel and rapid strategy has been developed to synthesize tetrahedral Ag3PO4 mesocrystals with the help of surfactant oleic acid. Homogeneous Ag3PO4 tetrahedron with average apex-to-apex length of 1.1μm could be synthesized under optimized conditions. Oleic acid is considered to be essential for the formation of this homogeneous tetrahedral morphology. The as-prepared tetrahedral Ag3PO4 mesocrystals could be formed through the close-packed assembly of Ag3PO4 nanoparticles, thus the formation of tetrahedral Ag3PO4 mesocrystals is explained by the oriented aggregation mechanism based on time-dependent experiments. Furthermore, the obtained tetrahedral Ag3PO4 mesocrystals exhibit enhanced visible-light photocatalytic degradation of methylene blue (MB) and methyl orange (MO) solutions compared to the reported micro-sized spherical Ag3PO4 particles with high photocatalytic performance.

Multicore iron oxide mesocrystals stabilized by a poly(phenylenepyridyl) dendron and dendrimer: role of the dendron/dendrimer self-assembly.

We report the formation of multicore iron oxide mesocrystals using the thermal decomposition of iron acetyl acetonate in the presence of the multifunctional and rigid poly(phenylenepyridyl) dendron and dendrimer. We thoroughly analyze the influence of capping molecules of two different architectures and demonstrate for the first time that dendron/dendrimer self-assembly leads to multicore morphologies. Single-crystalline ordering in multicore NPs leads to cooperative magnetic behavior: mesocrystals exhibit ambient blocking temperatures, allowing subtle control over magnetic properties using a minor temperature change.

Synthesis of octagonal microdisks assembled from anatase TiO2 nanosheets with exposed {001} facets

Octagonal TiO2 microdisks constructed orderly from anatase nanosheet building blocks (NSBBs) with exposed {001} facets were synthesized using a facile liquid phase precipitation method combined with subsequent heat treatment. The in-situ generated BF4− and F− adsorbed onto {001} facets of NH4TiOF3 (as precursor of TiO2) decreased the surface energy instead of extremely poisonous and corrosive HF. Polymer surfactant is likely to further stabilize the {001} facets and it may induce NH4TiOF3 nanocrystals as a linkage to align high-orderly by lateral expansion for the formation of NH4TiOF3 mesocrystals. Sintering temperature for the heat treatment of NH4TiOF3 microdisks has a considerable effect on TiO2 microdisks for the extent of exposure of the {001} surface. Symmetrically growths on [100] and [110] directions parallel to the {001} surface are favored which lead to the well-defined octagonal flat-shape. TiO2 microdisks show an excellent adsorption capacity in dark and enhanced reactive activity under irradiation of UV-light for the degradation of methylene blue, owing to the high-ordered organization of nanosheets and large exposure of high-energy facets.

Template-free synthesis of novel, highly-ordered 3D hierarchical Nb3O7(OH) superstructures with semiconductive and photoactive properties

3D hierarchical Nb3O7(OH) mesocrystals can be formed by self-organization from nanometer sized building blocks. The present study focuses on the synthesis and detailed investigation of mesocrystals, which can be achieved from a one-step, template-free hydrothermal synthesis approach. The obtained cubic superstructures consist of a periodic nanowire-network and combine a large surface area, high crystallinity, with a band gap of 3.2 eV and photocatalytic activity. Their easy processability in combination with the named excellent properties makes them promising candidates for a large number of applications. These include photochemical and photophysical devices where the Nb3O7(OH) mesocrystals can be used as electrode material since they are semiconducting and possess a large surface area. Generally the forces involved in the self-organized formation of mesocrystals are not fully understood. In this regard, the assembly of the Nb3O7(OH) mesocrystals was investigated in-depth applying transmission electron microscopy, scanning electron microscopy, UV/Vis measurements and electron energy-loss spectroscopy. Based on the achieved results a formation mechanisms is proposed, which expands the number of mechanisms for mesocrystal formation reported in literature. In addition, our study reveals different types of nanowire junctions and investigates their role at the stabilization of the networks.

Oriented aluminum nanocrystals in a one-step process

Aluminum coatings were deposited on glass substrates by chemical vapor deposition using N-methylpiperidine (nmp) stabilized dichloroalane [Cl2AlH·2nmp] as aluminum precursor. With regard to temperature, the experimental conditions were varied between 75°C and 125°C for the precursor and between 250°C and 450°C for the substrate. Depending on these parameters, highly textured layers could be deposited. The substrates have been consistently covered by a layer of idiomorphic, mostly distorted octahedra of aluminum single crystals. The morphologies of the structures and the degree of orientation of the crystals were investigated by a scanning electron microscopy and X-ray diffraction measurements. The high order of [111] orientation was found to decrease with increasing precursor and substrate temperature. We propose a mechanism for the generation of the octahedral structures based on the formation of mesocrystals. On heating, the dichloroalane (stabilized with nmp) loses the nmp ligands together with hydrogen and chlorine. The amine (nmp) seems to trigger the formation of aluminum crystals depending on the temperature and thus influences the texture of the Al-layer and the formation of well-formed octahedron-like structures.

Simple Additive-Free Method to Manganese Monoxide Mesocrystals and Their Template Application for the Synthesis of Carbon and Graphitic Hollow Octahedrons

Mesocrystals are of great importance owing to their novel hierarchical microstructures and potential applications. In the present work, a simple additive-free method has been developed for the controllable synthesis of manganese monoxide (MnO) mesocrystals, in which cheap manganese acetate (Mn(Ac)2) and ethanol were used as raw materials without involving any other expensive additives such as surfactants, polyelectrolyte, or polymers. The particle size of the resulting MnO mesocrystals is tunable in the range 400-1500 nm by simply altering the concentration of Mn(Ac)2 in ethanol. The percentage yield of the octahedral MnO mesocrystals is about 38 wt % with respect to the starting Mn(Ac)2. The selective adsorption of oligomers, which was resulted from the polymerization of ethanol, acted as an important role for the mesocrystal formation. A mechanism involving the oriented aggregation of MnO nanoparticle subunits and the subsequent ripening process was proposed. Moreover, for the first time, the as-synthesized MnO mesocrystals were employed as a novel template to fabricate functional materials with an octahedral morphology including MnO@C core/shells, carbon, and graphitic hollow octahedrons. This method shows the importance of mesocrystals not only for the field of material research but also for the application in functional materials synthesis.

Anatase TiO2 mesocrystals with exposed (0 0 1) surface for enhanced photocatalytic decomposition capability toward gaseous styrene

Anatase TiO2 mesocrystals with exposed (001) surface have been successfully synthesized by a facile one-step solvothermal method using NH4F as the structure regulator in glacial acetic acid environment. The exposed (001) surface of the obtained anatase TiO2 mesocrystal was consisted of numerous nanocrystals with exposed {001} facet. The results indicated that both the added amount of NH4F and solvothermal reaction time played significant roles in the formation of anatase TiO2 mesocrystals with exposed (001) surface. A possible formation mechanism of anatase TiO2 mesocrystal with exposed (001) surface was proposed based on the experimental data. As UV active photocatalysts, the resultant anatase TiO2 mesocrystals were evaluated in detail by photocatalytic decomposition of gaseous styrene. The results demonstrated that the anatase TiO2 mesocrystals fabricated by solvothermal treating a mixture of 0.50g NH4F, 2.50mL Ti(OC4H9)4 and 50mL of glacial acetic acid at 210°C for 24h exhibited the highest photocatalytic activity to the decomposition of styrene. This is due to the synergistic effects of excellent crystallinity, high energy {001} crystal facets, relatively large surface area, enhanced bandgap energy and unique mesoporous structure.

Anomalous magnetic behavior below 10 K in YCrO3 nanoparticles obtained under droplet confinement

Nanoparticles of multiferroic YCrO3 synthesized using the droplet confinement of miniemulsions show unusual features in the magnetic properties at low temperatures, which have not been reported before. Below 10 K, there is a sudden increase in the magnetization, and the nature of M–H hysteresis loops changes appreciably. The hysteresis loop shows two contributions, one similar to ferromagnetic and another similar to that expected from antiferromagnetic systems. This behavior can be understood by the formation of elongated grains or mesocrystals. It is remarkable that YCrO3 behaves quite differently from other multiferroic chromates such as ACrO3 (A = In, Sc, Sm).

Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano‐Structured Electrode Materials: Vanadium Oxide Mesocrystals

An additive and template free process is developed for the facile synthesis of VO2 (B) mesocrystals via the solvothermal reaction of oxalic acid and vanadium pentoxide. The six-armed star architectures are composed of stacked nanosheets homoepitaxially oriented along the [100] crystallographic register with respect to one another, as confirmed by means of selected area electron diffraction and electron microscopy. It is proposed that the mesocrystal formation mechanism proceeds through classical as well as non-classical crystallization processes, and is possibly facilitated or promoted by the presence of a reducing/chelating agent. The synthesized VO2 (B) mesocrystals are tested as a cathodic electrode material for lithium-ion batteries, and show good capacity at discharge rates ranging from 150-1500 mA g(-1) and a cyclic stability of 195 mA h g(-1) over fifty cycles. The superb electrochemical performance of the VO2 (B) mesocrystals is attributed to the porous and oriented superstructure that ensures large surface area for redox reaction and short diffusion distances. The mesocrystalline structure ensures that all the surfaces are in intimate contact with the electrolyte, and that lithium-ion intercalation occurs uniformly throughout the entire electrode. The exposed (100) facets also lead to fast lithium intercalation, and the homoepitaxial stacking of nanosheets offers a strong inner-sheet binding force that leads to better accommodation of the strain induced during cycling, thus circumventing the capacity fading issues typically associated with VO2 (B) electrodes.