Shape change of calcite single crystals to accommodate interfacial curvature: Crystallization in presence of Mg2+ ions and agarose gel-networks

Synthetic calcite single crystals,due to their strong crystal habit,tend to grow into characteristic rhombohedra.In the nature,biogenic calcite crystals form composites together with biomacromolecular materials,spurring investigations of how the growing calcite single crystals change their habit to satisfy the curvature of the organic phase.In this work,we examine calcite crystallization on a flat surface of glass slide and a curved surface of polystyrene(PS)sphere.The crystals exhibit tiny contact area onto the glass substrate that is averagely only 15% of their projected area on the substrate.In sharp contrast,the contact area greatly increase to above 75% of the projected area,once magnesium ions or agarose gel networks are introduced into the crystallization media.Furthermore,the calcite crystals form rough and step-like interfaces with a curved surface.However,the interfaces become smooth and curved as the crystals grow in presence of magnesium ions or agarose gel networks.The discrepancy between the interfacial structures implies kinetic effects of the additives on the crystallization around the surfaces. This work may provide implications for understanding the formation mechanisms of single-crystal composite materials.     

Highly polarized luminescence from optical quality films of a semiconducting polymer aligned within oriented mesoporous silica

In this Communication, we show that nanometer scale control of semiconducting polymer chain conformation is possible using host/guest chemistry in highly ordered and macroscopically oriented thin films of mesoporous silica. This control leads to a thin film composite material that is optically transparent, densely filled with polymer, and has highly polarized optical properties. Calculations of absorption and emission anisotropies further indicate full incorporation of the polymer into the nanoscale pore spaces. Such materials could serve as a useful tool for further investigations of polymer photophysics, as well as for device applications.     

Intermarriage of Halide Perovskites and Metal-Organic Framework Crystals

This Review examines how the intermarriage of perovskite and metal-organic framework crystals brings new paradigms for material design and functionality. The strategic combination of halide perovskites and metal–organic frameworks (MOFs) has generated a new family of porous composite materials that will enable new applications, including optoelectronic, catalysis, sensing, and data encryption. This Review surveys the current progress of this exciting new area. Fundamental aspects, including perovskite nucleation and growth, heterojunction electron–hole transfer, electronic structure, and luminescence within confined spaces, are highlighted, with suggestions of approaches by which guest confinement within MOFs can be synthetically designed. We further address the underlying principles and discuss the new insights and tools for the manipulation of these composite materials for the development of synthetic microporous semiconducting composites, as well as new strategies for host–guest interfacial engineering.     

Synthesis and Confinement of Carbon Dots in Lysozyme Single Crystals Produces Ordered Hybrid Materials with Tuneable Luminescence

The synthesis and confinement of graphitic nanoparticles (carbon dots) in the nanoscale solvent channels of cross‐linked lysozyme single crystals is used to prepare novel biohybrid luminescent materials. Co‐sequestration of acridine orange within the biohybrid crystals from acidic or neutral solutions yields FRET‐mediated phosphors emitting white or green light, respectively. The results offer a route to new types of tuneable multicolour luminescent materials based on microcrystalline host–guest energy‐transfer systems.     

Crystallization and morphology of iPP/MWCNT prepared by compounding iPP melt with MWCNT aqueous suspension

In this work, isotactic polypropylene (iPP) composites filled with multiwalled carbon nanotubes (MWCNTs) were prepared by compounding iPP melt with MWCNT aqueous suspension using a corotating twin-screw extruder, and the morphology and crystallization behavior of the composites were investigated. Scanning electron microscopy micrographs showed that MWCNTs dispersed individually at nanoscale in the iPP matrix when the MWCNTs concentration was low, though MWCNTs aggregates were detected when the filler concentration increased. The results of differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy indicated that the β-form crystal of iPP was induced by MWCNTs at the concentration of 0.1 wt.% which was dispersed individually in the iPP matrix. At higher content, however, MWCNTs acted as α-nucleating agent, and the crystals in the iPP/MWCNT composites showed higher degree of perfection than that of pure iPP though smaller in dimension. Crystallization rate of iPP increased significantly with increasing MWCNT content.     

Incorporating polymers within a single-crystal: From heterogeneous structure to multiple functions

Single-crystals, commonly considered as homogeneous solids, are able to be internally interfaced abnormally with guest polymers, which can be found in the biominerals where single-crystals incorporate surrounding biomacromolecules to reinforce their mechanical properties. This unique feature combining heterogeneous structure and long-range atomic ordering have attracted abundant investigations of reproducing their synthetic analogs to expand the potential application scope. Here, we summarize the recent progresses in the synthetic single-crystal composites, where polymer guests are incorporated inside single-crystals to generate heterogeneous structures without interruption to the long-range ordering of crystal hosts. First, the uniform and patterned encapsulations inside the various single-crystals are concluded in the sequence of isolated and continuous polymer-based guests. In addition, the mechanisms are classified chemically and physically, and the corresponding controlled factors that govern the incorporation processes are discussed. Most importantly, typical attempts on the applications of these heterogeneous single crystals are introduced, including mechanical reinforcement, bandgap engineering, catalyst, self-healing, controlled release, and optoelectronic devices. We aim at stressing on the current and potential applications benefited from the unique structural properties of the polymer incorporated single-crystals, and accordingly propose the perspectives to accelerate the path from the structural analysis toward prosperous functions.     

Controlled release of doxorubicin from electrospun MWCNTs/PLGA hybrid nanofibers

In this study, multiwalled carbon nanotubes (MWCNTs) were used to encapsulate a model anticancer drug, doxorubicin (Dox). Then, the drug-loaded MWCNTs (Dox/MWCNTs) with an optimized drug encapsulation percentage were mixed with poly(lactide-co-glycolide) (PLGA) polymer solution for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun Dox/PLGA, MWCNTs/PLGA, and Dox/MWCNTs/PLGA composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro viability assay and SEM morphology observation of mouse fibroblast cells cultured onto the MWCNTs/PLGA fibrous scaffolds demonstrate that the developed MWCNTs/PLGA composite nanofibers are cytocompatible. The incorporation of Dox-loaded MWCNTs within the PLGA nanofibers is able to improve the mechanical durability and maintain the three-dimensional structure of the nanofibrous mats. More importantly, our results indicate that this double-container drug delivery system (both PLGA polymer and MWCNTs are drug carriers) is beneficial to avoid the burst release of the drug and able to release the antitumor drug Dox in a sustained manner for 42 days. The developed composite electrospun nanofibrous drug delivery system may be used as therapeutic scaffold materials for post-operative local chemotherapy.     

Efficient and organic host–guest room-temperature phosphorescence: tunable triplet–singlet crossing and theoretical calculations for molecular packing

Organic host–guest doped materials exhibiting the room temperature phosphorescence (RTP) phenomenon have attracted considerable attention. However, it is still challenging to investigate their corresponding luminescence mechanism, because for host–guest systems, it is very difficult to obtain single crystals compared to single-component or co-crystal component materials. Herein, we developed a series of organic doped materials with triphenylamine (TPA) as the host and TPA derivatives with different electron-donating groups as guests. The doped materials showed strong fluorescence, thermally activated delayed fluorescence (τ: 39–47 ms), and efficient room temperature phosphorescence (Φ_phos: 7.3–9.1%; τ: 170–262 ms). The intensity ratio between the delayed fluorescence and phosphorescence was tuned by the guest species and concentration. Molecular dynamics simulations were used to simulate the molecular conformation of guest molecules in the host matrix and the interaction between the host and guest molecules. Therefore, the photophysical properties were calculated using the QM/MM model. This work provides a new concept for the study of molecular packing of guest molecules in the host matrix.

Molecular dynamics simulations were used to simulate the molecular conformation and interaction between hosts and guests. This work provides a new concept for the study of molecular packing for the investigation of the luminescence mechanism.     

Insight into the Structural Variation and Sodium Storage Behavior of Polyoxometalates Encapsulated within Single-Walled Carbon Nanotubes

The host–guest interaction can remarkably alter the physiochemical properties of composite materials. It is crucial to clarify the mechanism by revealing the influence of the host on the electronic structure of the guest molecules. Herein, we study the structural variation of polyoxometalates (POMs) after being confined in single-walled carbon nanotubes (SWNT). What we found is that in addition to the reported charge transfer from SWNT to POM, an intramolecular electron transfer within a single POM cluster can be observed in the POM@SWNT composites. Moreover, the charge density on the bridged oxygen of POMs is prominently enhanced. The structural change and electron reconfiguration of POMs upon encapsulation in SWNT significantly speed up electron and ion transport, leading to the improved electrochemical performance for sodium ions storage.     

CNT-based organic-inorganic composite materials with optoelectronic functionality

This paper focuses on the fabrication of organic-inorganic composite materials with optoelectronic functionality based on carbon nanotubes (CNTs) by chemical and physical modifications. The one-dimensionally (1D) ordered composites of rare earth phthalocyanine compounds (RePc₂) encapsulated by MWCNTs were obtained using a simple capillary filling method. The CNT-templated assembly of RePc₂ nanowires was performed by a phase-separation method. Two other kinds of organic-inorganic 1D-ordered optoelectronic composites were prepared using the template method: coating MWCNTs with a fluorescent poly(tripheny lamine) related co-polymer can be realized via a facile phase-separation strategy: 1D hy brid of bamboo-shaped CNTs covalently bound to RePc₂. The relationship between the microstructure of the obtained 1D-ordered composites and optoelectronic properties was studied, and it was found that these ordered composites exhibited enhanced photoconductivity due to the charge transfer between the composite components.     

Polarisation switching and molecular relaxation behaviour of anthraquinone dye-dispersed polymer-stabilised ferroelectric liquid crystal composites

Guest–host polymer-stabilised ferroelectric liquid crystal (GH-PSFLC) composite films have been prepared with dispersion of small concentration (0.1, 0.25 and 0.5 wt%) of anthraquinone blue dye in PSFLC host matrix via a polymerisation-induced phase separation (PIPS) process. The variation in alignment and size of twisted fibril has been observed in the optical textures of the guest–host composites with different wt/wt ratio of anthraquinone dye. The electrical and dielectric properties of PSFLC mixture and its guest–host derivatives are studied. Our results showed that an optimum amount of dye concentration (0.1 wt%) enhances the dielectric permittivity as well as the spontaneous polarisation of the GH-PSFLC material in the SmC* phase.     

A robust microporous 3D cobalt(II) coordination polymer with new magnetically frustrated 2D lattices: single-crystal transformation and guest modulation of cooperative magnetic properties

A microporous 3D cobalt(II) coordination polymer featuring pillared layers [Co(2)(ma)(ina)](n) x 2nH(2)O (1 x 2H(2)O) (ma = malate, ina = isonicotinate) was generated by hydrothermal treatment with a void volume of 25.8%, in which the in-situ generated ma ligands connect the Co(II) ions into a 2D lattice with mixed and multiple exchange-bridges, affording a new geometrical topology different from the Kagomé lattice and leading to spin frustration. The rigid ina-pillared metallic-layered structure could retain 3D structural ordering upon guest removal and exchange. By soaking guest-free host in MeOH and methanamide (HCONH(2)) solutions, single crystals of dehydrated were transformed into single crystals of 1 x MeOH and 1 x HCONH(2), respectively, without apparent host-structural changes. 1 can also be rehydrated into 1 x 2H(2)O'. The guest-inclusion crystals have been characterized by X-ray single-crystal diffraction at 293 K and 93 K, confirming the single-crystal-to-single-crystal transformations and providing detailed information of the guest molecules confined in the subnanospace and host-guest and/or guest-guest hydrogen-bonding interactions. The magnetic behaviours of this family of porous magnetic materials are complex due to the influences of multiple metal sites, intra- and inter-layer exchanges, spin-orbit coupling, as well as geometrical frustration, which show magnetic ordering at <2 K, 3.5 K, 3.5 K, and 8 K for 1, 1 x MeOH, 1 x HCONH(2), and 1 x 2H(2)O, respectively, due to the different size of guest molecules along with the different host-guest interaction, which may slightly modify the path of magnetic exchange, decrease the intensity of the spin-frustration in the 2D lattice, and cooperatively enhance the magnetic ordering temperature.     

Activating Versatile Mechanoluminescence in Organic Host–Guest Crystals by Controlling Exciton Transfer

Mechanoluminescence (ML) materials are attracting increasing interest owing to promising applications in various areas. However, to date, it remains a major challenge to develop a precise and universal route to achieving organic ML materials. Herein, we show that ML can be easily realized in organic piezophotonic host–guest crystals, under conditions in which neither the host nor the guest is ML-active. The experimental and theoretical results reveal that excitons of the host generated by piezoelectricity can be harvested effectively by the guest for light emission, owing to the restraint of intersystem crossing process. Moreover, different host–guest crystals are constructed, wherein the emission color, intensity, color purity, and emission duration of ML can be manipulated. This work deepens our understanding of organic ML generation in piezophotonic host–guest crystals and provides an inspiring principle to design more organic ML materials.     

Thermally conductive cyanate ester nanocomposites filled with graphene nanosheets and multiwalled carbon nanotubes

In this work, dodecylamine‐modified graphene nanosheets (DA‐GNSs) and γ‐aminopropyl‐triethoxysilane‐treated multiwalled carbon nanotubes (f‐MWCNTs) are employed to prepare cyanate ester (CE) thermally conductive composites. By adding 5 wt% DA‐GNSs or f‐MWCNTs to the CE resin, the thermal conductivities of the composites became 3.2 and 2.5 times that of the CE resin, respectively. To further improve the thermal conductivity, a mixture of the two fillers was utilized. A remarkable synergetic effect between the DA‐GNSs and f‐MWCNTs on improving the thermal conductivity of CE resin composites was demonstrated. The composite containing 3 wt% hybrid filler exhibited a 185% increase in thermal conductivity compared with pure CE resin, whereas composites with individual DA‐GNSs and f‐MWCNTs exhibited increases of 158 and 108%, respectively. Moreover, the composite with hybrid filler retained high electrical resistivity. Scanning electron microscopy images of the composite morphologies showed that the modified graphene nanosheets (GNSs) and multiwalled carbon nanotubes (MWCNTs) were uniformly dispersed in the CE matrix, and a number of junction points among MWCNTs and between MWCNTs and GNSs formed in the composites with hybrid fillers. Generally, we can conclude that these composites filled with hybrid fillers may be promising materials of further improving the thermal conductivity of CE composites. Copyright © 2014 John Wiley & Sons, Ltd.     

Reticular chemistry of metal-organic polyhedra

Metal-organic polyhedra (MOPs), are discrete metal-organic molecular assemblies. They are useful as host molecules that can provide tailorable internal volume in terms of metrics, functionality, and active metal sites. As a result, these materials are potentially useful for a variety of applications, such as highly selective guest inclusion and gas storage, and as nanoscale reaction vessels. This review identifies the nine most important polyhedra, and describes the design principles for the five polyhedra most likely to result from the assembly of secondary building units, and provides examples of these shapes that are known as metal-organic crystals.     

Synthesis and characterization of tin telluride inorganic/organic composite materials with nanoscale periodicity through solution-phase self-assembly: a new class of composite materials based on Zintl cluster self-oligomerization

In this work, we demonstrate the synthesis of semiconducting tin telluride inorganic/organic composite materials with nanoscale periodicity prepared using solution phase self-assembly. Oligomerization of anionic SnTe ₄ ^4? clusters by halogen-mediated tellurium elimination in the presence of surfactant leads to the formation of a meosotructured composite. The composites initially forms as a mixture of mesophases, usually some combination of a layered phase and a phase based on cylindrical building blocks. Post synthetic treatment leads to a solid-state structural change which converts the composites to a single mesophase architecture with a hexagonal honeycomb (p6mm) morphology on the nanometer length scale. A by product of this reaction, however, is bulk tellurium. Changes in the electronic structure of the materials during synthesis and solid-state restructuring are probed using electron spin resonance (ESR) spectroscopy.     

Orientational control of guest molecules in an organic intercalation system by host polymer tacticity

Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n-alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals.     

The Crystalline Sponge Method in Water

The crystalline sponge method entails the elucidation of the (absolute) structure of molecules from a solution phase using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals. The host crystal that is most often used decomposes in protic or nucleophilic solvents, or when guest molecules with Lewis basic substituents are introduced. Here a new class of (water) stable host crystals based on f-block metals is disclosed. It can be shown that these hosts not only increase the scope of the crystalline sponge method to a wider array of solvents and guests, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry.     

Carbon nanotubes incorporated within lyotropic hexagonal liquid crystal formed in room-temperature ionic liquids

Multiwalled carbon nanotubes (MWCNTs) were evenly dispersed within hexagonal lyotropic liquid crystals (LLCs) formed in room-temperature ionic liquids (RTILs), ethylammonium nitrate (EAN). Characterization and tribological properties of dispersed system were studied in detail. Polarized optical microscopy images combined with small-angle X-ray scattering (SAXS) results indicate that the MWCNTs are well-dispersed and that the introduction of MWCNTs does not destroy the structure of hexagonal LLCs. The increase of d spacing demonstrates the integration of MWCNTs within the cylinders of the hexagonal LLCs. FT-IR and Raman spectra of the MWCNTs-LLC composites show the characteristic absorption peaks and Raman bands of MWCNTs. The tribological properties were explored to greatly extend the applications of MWCNTs-LLC composites in RTILs as lubricating materials. The rheological measurement results indicate that MWCNTs-LLC composites are highly viscoelastic and that the apparent viscosity is enhanced by the presence of the MWCNTs.     

Organic intercalation material: reversible change in interlayer distances by guest release and insertion in sandwich-type inclusion crystals of cholic acid

Cholic acid (CA) forms inclusion crystals that have a sandwich-type lamellar structure constructed by the alternative stacking of host bilayers and guest layers. Five disubstituted benzenes, o-toluidine, m-fluoroaniline, o-chlorotoluene, o-bromotoluene, and indene, are accommodated in the two-dimensional void space between the host bilayers at 1:2 host-guest stoichiometries. Thermal gravimetric analysis of the inclusion crystals revealed that all the guest molecules, except o-toluidine, are released in two separate steps, indicating the formation of intermediate crystals after the first guest release. Adequate heat treatment of the four inclusion crystals induces release of half or three quarters of the guest molecules. X-ray diffraction patterns of the intermediate crystals revealed that the crystals have a bilayer structure the same as those of the common CA inclusion crystals. They have one-dimensional cavities, in which the guest molecules are included at a 1:1 or 2:1 host-guest stoichiometry. These facts indicate that the host bilayers move 1.6-4.5 A perpendicular to the layer direction by desorption of the guest molecules. Furthermore, a reverse structural change is also achieved by absorption of the guest molecules to regenerate the starting sandwich-type inclusion crystals. This reversible change in the host bilayer by the guest sorption and desorption is a novel example of organic intercalation materials.