Controlled-growth of Zn(OH)F Microbesoms in the Mild Aqueous Solution and Their Photocatalytic Activity

Zn(OH)F microbesoms have been synthesized on a large scale by a facile solution‐based method using polymer as crystal growth modifier. The obtained products were characterized by X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The effects of modifier polyacrylamide (PAM), reaction time, concentrations of NaF on the morphology and size of the product were studied. The results revealed that the Zn(OH)F microbesom had orthorhombic structures. Experimental conditions had all influence on the shape and size of the final products, but polymer PAM played the key role in formation of the Zn(OH)F microbesom. This novel structures exhibited good UV photocatalytic abilities.     

聚合物控制CuO纳米盘的液相生长

表面活性剂聚丙烯酰胺（PAM）的控制下,在温和的低温水溶液中,高产率的CuO纳米盘被合成。粉未衍射（XRD）,扫描电镜（SEM）,高分辨透射电子显微（HRTEM）对产物的形貌结构进行表征。研究了不同反应条件如温度、PAM浓度等对产物形貌与尺寸的影响。结果表明,CuO纳米盘为单晶结构,沿着（002）和（110）面生长。PAM对纳米盘的形成起到关键作用。典型的聚合物-晶体作用生长机理用来解释CuO纳米盘的形成。聚合物诱引晶体生长与调控纳米晶自组装将提供了一条有效的路径来合成具有复杂形貌与特殊结构的无机和无机-有机杂化材料。     

Polymer-controlled crystallization of zinc oxide hexagonal nanorings and disks

In this study, we have developed a novel route to the synthesis of ZnO nanorings, disks, and diskoidlike crystals on a large scale by a facile solution-based method by using polymers as crystal growth modifiers. The crystals precipitated with polyacrylamide (PAM) as the additive show ringlike morphology. A possible growth mechanism of the ZnO nanostructures based on typical polymer-crystals interactions in a mild aqueous solution is given. The polymer contains in the side chain a large number of amide ligands that are able to coordinate with Zn(2+) ions, that is, the otherwise just weakly exposed (001) face, leading to a lowering of surface energy and inhibition of growth along this direction and the formation of ringlike morphologies. While in the presence of carboxyl-functionalized polyacrylamide (PAM-COOH), nearly monodispersed disklike crystals were observed and finally evolved into diskoidlike microstructures with the reaction time prolonged. Polymer-directed crystal growth and mediated self-assembly of nanocrystals may provide promising routes to rational synthesis of various ordered inorganic and inorganic-organic hybrid materials with complex form and structural specialization.     

Preparation of porous CaCO3/PAM composites by CO2 in water emulsion templating method

Emulsion templating is an effective method to prepare well-defined porous polymeric materials. In this paper, porous CaCO₃/polyacrylamide (PAM) composites were prepared by emulsion templating polymerization in supercritical CO₂(scCO₂) by using a commercial grade surfactant (FC4430), therefore, the amount of the fillers and the pore size distribution of the composites can be modulated based on the demands of those potential applications as biomaterials. Calcium carbonate crystals can be in situ synthesized in the porous PAM matrix, and the morphology of CaCO₃ varied with the conditions of the reaction, the results indicated that three kinds of crystals were observed in the porous matrix. The results of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) showed that the macropores in PAM were interconnected and with narrow pore size distributions.     

Effects of Electron Beam Irradiation on the Structural Properties of PVA/PAM/CMC Ternary Polymer Blends

Ternary miscible blends based on various ratios of poly(vinyl alcohol) (PVA), poly(acrylamide) (PAM) and carboxymethyl cellulose (CMC) were prepared by solution casting in the form of thin films. The structure‐property behavior of the ternary PVA/PAM/CMC blends, before and after they had been exposed to various doses of electron beam irradiation, was investigated by FT‐IR spectroscopy, SEM, XRD and stress‐strain curves. The visual observation showed that the cast films of the individual polymers PVA, PAM, and CMC and their blends over a wide range of composition are clear and transparent indicating the miscibility of PVA/PAM/CMC ternary blends. The FT‐IR analysis of pure polymers or their ternary blends before or after electron beam irradiation proved the formation of hydrogen bonding. In addition, it was found that the intensity of the different absorption bands depends on the ratio of PAM and CMC in the ternary blend. The XRD patterns showed that the peak position for the ternary blends decreases with increasing the ratio of CMC in the blend. However, the peak position for the ternary blend based on equal ratios of pure polymers was not affected by blending and was found in the same position as in the XRD pattern of pure PVA. The SEM micrographs give support to the visual observation indicating the complete miscibility of PVA/PAM/CMC ternary blends. The improvement in morphology leads to improvement in the tensile mechanical properties of the ternary polymer blends.     

油炸圈饼状Cd(OH)2微结构的合成与可控生长机理

聚丙烯酰胺（PAM）表面活性剂的作用下,在温和的低温水溶液中,合成了Cd(OH)2油炸圈饼状微米结构。这种结构是由单晶结构的六方片状Cd(OH)2按一定排列方式自组装而成。在羰基修饰的PAM（PAM-COOH）表面活性剂作用下,得到中心有孔的油炸圈饼纳米结构。可能的生长机理为表面活性剂控制下Cd(OH)2纳米片经历有序连接过程,最终形成油炸圈饼状结构。聚合物诱引晶体生长与调控纳米晶自组装将提供了一条有效的路径来合成具有复杂形貌与特殊结构的无机和无机-有机杂化材料。     

Fuel‐Driven Transient Crystallization of a Cucurbit[8]uril‐Based Host–Guest Complex

Transient self‐assembling systems often suffer from accumulation of chemical wastes that interfere with the formation of pristine self‐assembled products in subsequent cycles. Herein, we report the transient crystallization of a cucurbit[8]uril‐based host‐guest complex, preventing the accumulation of chemical wastes. Base‐catalyzed thermal decarboxylation of trichloroacetic acid that chemically fuels the crystallization process dissolves the crystals, and produces volatile chemical wastes that are spontaneously removed from the solution. With such self‐clearance process, no significant damping in the formation of the crystals was observed. The morphology and structural integrity of the crystals was also maintained in subsequent cycles. The concept may be further extended to obtain other temporally functional materials, quasicrystals, etc., based on stimuli‐responsive guest molecules.     

Crystal Growth Mechanisms and Morphological Control of the Prototypical Metal–Organic Framework MOF‐5 Revealed by Atomic Force Microscopy

Crystal growth of the metal–organic framework MOF‐5 was studied by atomic force microscopy (AFM) for the first time. Growth under low supersaturation conditions was found to occur by a two‐dimensional or spiral crystal growth mechanism. Observation of developing nuclei during the former reveals growth occurs through a process of nucleation and spreading of metastable and stable sub‐layers revealing that MOFs may be considered as dense phase structures in terms of crystal growth, even though they contain sub‐layers consisting of ordered framework and disordered non‐framework components. These results also support the notion this may be a general mechanism of surface crystal growth at low supersaturation applicable to crystalline nanoporous materials. The crystal growth mechanism at the atomistic level was also seen to vary as a function of the growth solution Zn/H₂bdc ratio producing square terraces with steps parallel to the <100> direction or rhombus‐shaped terraces with steps parallel to the <110> direction when the Zn/H₂bdc ratio was >1 or about 1, respectively. The change in relative growth rates can be explained in terms of changes in the solution species concentrations and their influence on growth at different terrace growth sites. These results were successfully applied to the growth of as‐synthesized cube‐shaped crystals to increase expression of the {111} faces and to grow octahedral crystals of suitable quality to image using AFM. This modulator‐free route to control the crystal morphology of MOF‐5 crystals should be applicable to a wide variety of MOFs to achieve the desired morphological control for performance enhancement in applications.     

Synthesis,Properties, and Evolution Mechanism of Morphology Tunable InPO4 Crystals

In the synthesis of InPO₄ crystals, using F127 [(EO)₁₀₆(PO)₇₀(EO)₁₀₆] as a structure‐directing template, a morphology tunable progress was observed during the crystal evolution. By verifying the initial pH from 1.0 to 12.0, the morphology is evolved from single crystal, through sub‐micro crystallites, and finally to crystalline nanoparticles. The most influential factors in the morphology evolution are the initial pH level, the participation of surfactant‐template F127, and the change in pH during the reaction.     

Large-scale fabrication of tower-like, flower-like, and tube-like ZnO arrays by a simple chemical solution route

Large-scale arrayed ZnO crystals with a series of novel morphologies, including tower-like, flower-like, and tube-like samples, have been successfully fabricated by a simple aqueous solution route. The morphology and orientation of the obtained ZnO crystal arrays can be conveniently tailored by changing the reactants and experimental conditions. For example, the tower-like ZnO crystal arrays were obtained in a reaction solution system including zinc salt, ammonia, ammonium salt, and thiourea, and the orientation of these tower-like crystals could be controlled by the contents of these reactants. Flower-like ZnO arrays were obtained at lower temperatures, and tube-like ZnO arrays were obtained by ultrasonic pretreatment of the reaction system. The growth mechanism of the tower-like and tube-like ZnO crystals was investigated by FESEM. The results show that tower-like crystals grow layer by layer, while tube-like crystals grow from active nanowires. Ultrasonic pretreatment is proved to be effective in promoting the formation of active nuclei, which have important effects on the formation of the tube-like ZnO crystals. In addition, large-scale arrays of these ZnO crystals can be successfully synthesized onto various substrates such as amorphous glass, crystalline quartz, and PET. This implies this chemical method has a wide application in the fabrication of nano-/microscale devices.     

Size Fractionation of Two‐Dimensional Sub‐Nanometer Thin Manganese Dioxide Crystals towards Superior Urea Electrocatalytic Conversion

A universal technique has been proposed to sort two‐dimensional (2D) sub‐nanometer thin crystals (manganese dioxide MnO₂ and molybdenum disulfide MoS₂) according to their lateral dimensions. This technique is based on tuning the zeta potential of their aqueous dispersions which induces the selective sedimentation of large‐sized 2D crystals and leaves the small‐sized counterparts in suspension. The electrocatalytic properties of as‐obtained 2D ultrathin crystals are strongly dependent on their lateral size. As a proof‐of‐concept study, the small‐sized MnO₂ nanocrystals were tested as the electrocatalysts for the urea‐oxidation reaction (UOR), which showed outstanding performance in both half reaction and full electrolytic cell. A mechanism study reveals the enhanced performance is associated with the remarkable structural properties of MnO₂ including ultrathin (ca. 0.95 nm), laterally small‐sized (50–200 nm), and highly exposed active centers.     

Visualizing the crystal structure and locating the catalytic activity of micro- and mesoporous ZSM-5 zeolite crystals by using in situ optical and fluorescence microscopy

A combination of optical and fluorescence microscopy was used to study the morphology of micro‐ and mesoporous H‐ZSM‐5 zeolite crystals (17×4×4 μm) and to evaluate, in a spatially resolved manner, the effect of mesoporosity, introduced via desilication, on catalytic performance. For this purpose, the oligomerization of various styrene molecules was used as a model reaction, in which the carbocation intermediates formed in the zeolite pores act as reporter molecules. In situ confocal fluorescence measurements after the template removal process showed that the crystals generally consist of three different subunits that have pyramidal boundaries with each other. Examination of these crystals during styrene oligomerization revealed differences in the catalytic activity between the purely microporous and the combined micro‐ and mesoporous crystals. The introduction of intracrystalline mesoporosity limits the formation to dimeric carbocation intermediates and facilitates the transport of styrene molecules inside the zeolite volume. This leads to a more uniform coloration and fluorescence pattern of the crystals. Moreover, the oligomerization of various styrene compounds, which differ in their reactivity, provides a good way of estimating the Brønsted acid strength in a spatially resolved manner, showing a nonhomogeneously distributed Brønsted acidity over the volume of the crystals. More detailed information on the structure of the ZSM‐5 crystals was revealed for mesoporous crystals during the oligomerization of 4‐methoxystyrene. This reaction induced an “explosion” of the crystal leading to the formation of a complex system with at least eight different subunits. Finally, polarized‐light microscopy was used to unravel the pore geometry in these individual building blocks. The observed differences in catalytic behavior between micro‐ and mesoporous ZSM‐5 crystals are strengthened by the microspectroscopic techniques employed, which show that upon desilication the crystal morphology is affected, the product distribution is changed towards less conjugated carbocation intermediates, and that a gradient in Brønsted acid strength appears to be present.     

Facile synthesis of urchin-like glass/nickel core/shell composite hollow spheres

Novel urchin-like core/shell composite hollow spheres were fabricated by assembly of nickel nanocones on the surface of hollow glass spheres; the effects of some reaction parameters on the morphology of the shell layers and the room temperature magnetic properties of the products were investigated.     

Facile Fabrication of Nanorod‐Assembled Fluorine‐Substituted Hydroxyapatite (FHA) Microspheres

Nanorod‐assembled FHA microspheres with different F contents were for the first time prepared through a facile one‐step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self‐assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self‐assembled into sphere‐like sturctures at high pH conditions and rod‐like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca²⁺ release kinetics from EDTA‐Ca‐Na₂ at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self‐assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability.     

Oriented Two‐Dimensional Porous Organic Cage Crystals

The formation of two‐dimensional (2D) oriented porous organic cage crystals (consisting of imine‐based tetrahedral molecules) on various substrates (such as silicon wafers and glass) by solution‐processing is reported. Insight into the crystallinity, preferred orientation, and cage crystal growth was obtained by experimental and computational techniques. For the first time, structural defects in porous molecular materials were observed directly and the defect concentration could be correlated with crystal growth rate. These oriented crystals suggest potential for future applications, such as solution‐processable molecular crystalline 2D membranes for molecular separations.     

Biomimetic growth of CaCO3 pancakes on the leaves of Epipremnum aureum

Rhombohedral, disk-like and pancake-like calcite crystals were synthesized in the different reaction condition via facial vegetal bio-templates, the leaves of Epipremnum aureum. The resultant crystals were characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The results showed that disk-like and pancakes calcite were obtained on the surface of Epipremnum aureum leaves in 50 mM CaCl₂ solution at starting pH values of 9.7 and 11.7, respectively. The dynamic process of formation of multiple crystals was analyzed by monitoring the continuous morphological and structural evolution and components of crystals in different crystal stages. Moreover, it is found that the surface structure of the leave and starting pH value of reaction solution provide profound influence on the morphology of CaCO₃ crystals. This provides a facile and novel method to prepare hierarchical CaCO₃ crystals.     

Temperature Influence on the Morphology and Roughness of Silver Deposit Formed by Cementation

The morphology and surface roughness of silver deposits formed by cementation in 0.5M H₂SO₄ solution containing 0.5M CuSO₄ was investigated at various temperatures. The influence of O₂ on the morphology of deposited Ag on the Cu surface was studied in solutions containing 20 or 100 mg/dm³ initial Ag⁺. Surface‐height‐distribution diagrams were calculated from scanning‐electron‐microscopic (SEM) images. For the lower Ag⁺ concentration, the formation of granular deposits occurred in the presence of O₂. In contrast, under anaerobic conditions, rather flat deposits with tiny Ag crystals were observed. For the higher Ag⁺ concentration, the presence of O₂ did not significantly affect the morphology of the Ag deposit, but increasing temperature resulted in more‐compact and denser dendrites. Differences in the Ag‐deposit morphology and surface roughness were attributed to a different mechanism in the absence of O₂. Under anaerobic conditions, a competitive reaction between Ag⁺ and Cu⁺ occurs in bulk solution, which consumes additional Ag⁺ ions. The SEM images and, especially, distribution diagrams of the surface height provided useful information on the formation and expansion of anodic sites on the Cu surface at various temperatures.     

Chirality Induction through Nano‐Phase Separation: Alternating Network Gyroid Phase by Thermotropic Self‐Assembly of X‐Shaped Bolapolyphiles

The single gyroid phase as well as the alternating double network gyroid, composed of two alternating single gyroid networks, hold a significant place in ordered nanoscale morphologies for their potential applications as photonic crystals, metamaterials and templates for porous ceramics and metals. Here, we report the first alternating network cubic liquid crystals. They form through self‐assembly of X‐shaped polyphiles, where glycerol‐capped terphenyl rods lie on the gyroid surface while semiperfluorinated and aliphatic side‐chains fill their respective separate channel networks. This new self‐assembly mode can be considered as a two‐color symmetry‐broken double gyroid morphology, providing a tailored way to fabricate novel chiral structures with sub‐10 nm periodicities using achiral compounds.     

The Mosaic Structure of Zeolite Crystals

Zeolites are widely used in many commercial processes, mostly as catalysts or adsorbents. Understanding their intimate structure at the nanoscale is the key to control their properties and design the best materials for their ever increasing uses. Herein, we report a new and controllable fluoride treatment for the non‐discriminate extraction of zeolite framework cations. This sheds new light on the sub‐structure of commercially relevant zeolite crystals: they are segmented along defect zones exposing numerous nanometer‐sized crystalline domains, separated by low‐angle boundaries, in what were apparent single‐crystals. The concentration, morphology, and distribution of such domains analyzed by electron tomography indicate that this is a common phenomenon in zeolites, independent of their structure and chemical composition. This is a milestone to better understand their growth mechanism and rationally design superior catalysts and adsorbents.     

Luminescent Metallacycle‐Cored Liquid Crystals Induced by Metal Coordination

Two rhomboidal metallacycles based on metal‐coordination‐driven self‐assembly are presented. Because metal‐coordination interactions restrict the rotation of phenyl groups on tetraphenylethene units, these metallacycles were emissive both in solution and in solid state, and their aggregation‐induced emission properties were well‐retained. Moreover, the rhomboidal metallacyclic structures offer a platform for intermolecular packing beneficial for the formation of liquid crystalline phases. Therefore, although neither of building blocks shows mesogenic properties, both thermotropic and lyotropic (in DMF) mesophases were observed in one of metallacycles, indicating that mesophases could be induced by metal‐coordination interactions. This study not only reveals the mechanism for the formation of cavity‐cored liquid crystals, but also provides a convenient approach to preparing supramolecular luminescent liquid crystals, which will serve as good candidates for chemo sensors and liquid crystal displays.