Hybrid Mesostructures Research Articles

Controlled Crystallization of Diblock Copolymers on Carbon materials: Effect of Block Length

The fabrication of sophisticated hybrid mesostructures involving carbon nanomaterials and organic building blocks has attracted great attention due to their tunable properties and potential applications. Herein, we report the precisely controlled structure and morphology of diblock copolymers-carbon materials hybrid mesostructures, in which nano/micron- disc shape and honeycomb structure were fabricated on the surfaces of carbon nanotube (CNT), carbon nanofiber (CNF), and graphite, respectively. Synthesized ethylene/functional cyclic olefin block copolymers (PE-b-HPNBMA) showed a narrow dispersity, allowing the formation of nanohybrid shish-kebab structures (NHSK) with a highly uniform disc-shape crystalline size and period. The tunability of HPNBMA block length and functional substituent enables not only control of the nanocrystal size but also flexible design of the surface chemical structure, which can endow diblock copolymers-carbon materials hybrid mesostructures with specific properties. As proof of the ability, superhydrophobic (contact angle > 150°) NHSK films with tunable adhesion were successfully produced.

Near-Infrared Chiral Plasmonic Microwires through Precision Assembly of Gold Nanorods on Soft Biotemplates

Directing the assembly of plasmonic nanoparticles into chiral superstructures has diverse applications including, chiroptical sensing, nonlinear optics, and biomedicine. Though soft template-mediated assemblies of both spherical and nonspherical gold nanoparticles have made significant progress, most approaches require sophisticated chemical synthesis or advanced methodologies. Besides, reports of structurally precise chiral plasmonic assemblies beyond nanoscale are limited. Here, we propose an efficient yet simple strategy to grow such precision assemblies up to mesoscale, which is beneficial for a broader community. Briefly, cationic gold nanorods (AuNRs) are allowed to systematically assemble along atomically precise, chiral, rodlike tobacco mosaic virus (TMV) particles via electrostatic attraction under ambient condition. This leads to spontaneous formation of helical hybrid microwires with high structural precision, as evidenced by cryogenic transmission electron microscopy and tomography. Resulting composite superstructures show a strong circular dichroism response at the plasmon wavelength of the AuNRs, which is supported by simulations using discrete dipole approximation. Further, chirality of the system is investigated at a single-microwire level using polarized dark-field scattering microscopy. An alternative chiral template, negatively charged colloidal cellulose nanocrystals, also arrange AuNRs into similar chiral microstructures. Thus, our report proposes a generic methodology to obtain chiral plasmonic response at the NIR region using inexpensive templates that will encourage the exploration of a wider range of nanoscale templates for creating hybrid mesostructures with emerging optoelectronic properties.

A Modular Fluorescent Probe for Viscosity and Polarity Sensing in DNA Hybrid Mesostructures.

There exists a critical need in biomedical molecular imaging and diagnostics for molecular sensors that report on slight changes to their local microenvironment with high spatial fidelity. Herein, a modular fluorescent probe, termed StyPy, is rationally designed which features i) an enormous and tunable Stokes shift based on twisted intramolecular charge transfer (TICT) processes with no overlap, a broad emission in the far‐red/near‐infrared (NIR) region of light and extraordinary quantum yields of fluorescence, ii) a modular applicability via facile para‐fluoro‐thiol reaction (PFTR), and iii) a polarity‐ and viscosity‐dependent emission. This renders StyPy as a particularly promising molecular sensor. Based on the thorough characterization on the molecular level, StyPy reports on the viscosity change in all‐DNA microspheres and indicates the hydrophilic and hydrophobic compartments of hybrid DNA‐based mesostructures consisting of latex beads embedded in DNA microspheres. Moreover, the enormous Stokes shift of StyPy enables one to detect multiple fluorophores, while using only a single laser line for excitation in DNA protocells. The authors anticipate that the presented results for multiplexing information are of direct importance for advanced imaging in complex soft matter and biological systems.

Highly ordered AIEgen directed silica hybrid mesostructures and their light-emitting behaviours

Mesostructured fluorescent silica hybrids (MFSHs) were synthesized by using tetraphenylethylene (TPE)-based quaternary ammonium salts as surfactants with typical aggregation-induced emission (AIE) behaviours.

Spontaneous chiral self-assembly of achiral AIEgens into AIEgen-silica hybrid nanotubes.

Antipodal chiral AIEgen-silica hybrid mesostructures were fabricated by spontaneous chiral self-assembly of the achiral amphiphilic AIEgen 2-[4-(1,2,2-triphenylethenyl)phenoxy]-acetic acid via a co-structure directing route in the absence of any symmetry-breaking agent. The produced AIEgen-silica hybrid mesostructured nanotubes showed chiral features with optical activity originating from J-aggregation with an excess of one stereochemical hand of the helical conformation of the AIEgen.

1AW2 リオトロピック液晶材料の設計に基づく有機無機複合メソ構造の垂直配向制御(2014年奨励賞受賞講演,2015年日本液晶学会討論会)

1AW2 リオトロピック液晶材料の設計に基づく有機無機複合メソ構造の垂直配向制御(2014年奨励賞受賞講演,2015年日本液晶学会討論会)

Polymer-templated mesoporous hybrid oxides of Al and Cu: highly porous sorbents for ammonia

Hybrid mesostructures consisting of copper and aluminum oxides were synthesized via co-condensation of suitable precursors in the presence of a triblock copolymer, Pluronic F127.

ChemInform Abstract: Insights into Mesoporous Metal Phosphonate Hybrid Materials for Catalysis

AbstractReview: 236 refs.

Hierarchical Polymer-Carbon Nanotube Hybrid Mesostructures by Crystallization-Driven Self-Assembly.

Multistep crystallization-driven self-assembly has great potential to enable the construction of sophisticated hybrid mesostructures. During the assembly procedure, each step modifies the properties of the overall structure. Here, we demonstrate the flexibility and efficiency of this approach by preparing polymer-carbon nanotube (CNT) hybrid mesostructures. We started by growing polyferrocenyldimethylsilane (PFS) homopolymer crystals onto multiwalled CNTs. This first step facilitated the redispersion of the coated CNTs in both polar (2-propanol) and nonpolar (decane) solvents. In the second step of hybrid construction, a unimer solution of a PFS block copolymer was added into the PFS-CNT solution. The PFS coating on the CNT initiated the growth of elongated micelles, resulting in structures that resembled hairy caterpillars. PFS-b-P2VP (P2VP = poly-2-vinylpyridine) micelles were grown from the surface of PFS-CNT hybrids in 2-propanol, and PFS-b-PI (PI = polyisoprene) micelles were grown from these hybrids in decane. These micelles, by transmission electron microscopy were seen to have an unusual wavy kinked structure, very different from the uniform smooth structures normally formed by both block copolymers. For hybrids with PFS-b-PI micelles, cross-linking of the micelle coronas locked the whole structure in place and allowed us to use the partial oxidation of PFS components to grow metal nanoparticles in the core of these micelles. We finally investigated the influence of the corona-forming block used to grow the micelles on the wettability of films made from these mesostructures. Films formed with CNT hybrids grafted with PFS-b-PI micelles were superhydrophobic (contact angle, 152°). In contrast, the surface of the films was much more hydrophilic (contact angle, 54°) when they were prepared from CNT hybrids grafted with PFS-b-P2VP micelles.

Mesoporous Materials‐Based Electrochemical Enzymatic Biosensors

AbstractThis review (239 references) is dealing with the use of mesoporous materials in the field of electrochemical enzymatic biosensors. After a brief discussion on the interest of mesoporous materials for electrochemical biosensing, a presentation of the various types of inorganic and organic‐inorganic hybrid mesostructures used to date in the elaboration of enzymatic bioelectrodes is given and the main bioelectrode configurations are described. The various biosensor applications are then summarized on the basis of a comprehensive table and some representative illustrations. The main detection schemes developed in the field are based on amperometry and mediated electrocatalysis, as well as some on spectroelectrochemistry.

Mesoporous Materials‐Based Electrochemical Sensors

AbstractA review (350 references) is given to the interest of mesoporous materials for designing electrochemical sensors. After a brief summary of the implication of template‐based ordered mesoporous materials in electrochemical science, the various types of inorganic and organic‐inorganic hybrid mesostructures used to date in electroanalysis and the corresponding electrode configurations are described. The various sensor applications are then discussed on the basis of comprehensive tables and some representative illustrations. The main detection schemes developed in the field are (volt)amperometric sensing subsequent to preconcentration and electrocatalytic detection.

Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate-Ag2S-CdS semiconductors.

Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O40(3-), SiW12O40(4-) and PMo12O40(3-), were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.

ChemInform Abstract: Ordered Hybrids from Template‐Free Organosilane Self‐Assembly

AbstractReview: 133 refs.

Periodic Mesostructured Silica Films Made Simple Using UV Light

Recent research has shown that silica/surfactant self-assembly combined with photoacid-catalyzed sol–gel polymerization can direct the formation of disordered mesoporous silica films. Using only a mixture of photoacid generator (PAG), amphiphilic surfactant (PEO-b-PPO-b-PEO), and methoxy oligomeric precursor, this original UV-driven method is fast and obviates the need of sol preparation and volatile compounds. Here, we report a rational basis to promote a disorder-to-order transition through the control of relative humidity (RH) and irradiance. Above a threshold RH of 35%, a long-range organization is promoted by greater interactions between the water-enriched silica phase and the PEO block. Alternatively, mesophase rearrangement and ordering are achieved by decreasing the irradiance below a limiting value (150 mW/cm2) so as to minimize the condensation rate. These two strategies show that the fundamental driving force for the creation of well-ordered hybrid mesostructures can be described both on thermo...

Ordered Hybrids from Template‐Free Organosilane Self‐Assembly

Despite considerable achievements over the last two decades, nonporous organic-inorganic hybrid materials are mostly amorphous, especially in the absence of solvothermal processes. The organosilane self-assembly approach is one of the few opportunities for creating a regular assembly of organic and inorganic moieties. Additionally, well-established organosilicon chemistry enables the introduction of numerous organic functionalities. The synthesis of periodically ordered hybrids relies on mono-, bis-, or multisilylated organosilane building blocks self-assembling into hybrid mesostructures or superstructures, subsequently cross-linked by siloxane Si-O-Si condensation. The general synthesis procedure is template-free and one-step. However, three concurrent processes underlie the generation of self-organized hybrid networks: thermodynamics of amphiphilic aggregation, dynamic self-assembly, and kinetically controlled sol-gel chemistry. Hence, the set of experimental conditions and the precursor structure are of paramount importance in achieving long-range order. Since the first developments in the mid-1990s, the subject has seen considerable progress leading to many innovative advanced nanomaterials providing promising applications in membranes, pollutant remediation, catalysis, conductive coatings, and optoelectronics. This work reviews, comprehensively, the primary evolution of this expanding field of research.

Metal Phosphonate Hybrid Mesostructures: Environmentally Friendly Multifunctional Materials for Clean Energy and Other Applications

The synthesis of porous hybrid materials has been extended to mesoporous non-silica-based organic-inorganic hybrid materials, in which mesoporous metal phosphonates represent an important family. By using organically bridged polyphosphonic acids as coupling molecules, the homogeneous incorporation of a considerable number of organic functional groups into the metal phosphonate hybrid framework has been realized. Small amounts of organic additives and the pH value of the reaction solution have a large impact on the morphology and textural properties of the resultant hybrid mesoporous metal phosphonate solids. Cationic and nonionic surfactants can be used as templates for the synthesis of ordered mesoporous metal phosphonates. The materials are used as efficient adsorbents for heavy metal ions, CO₂, and aldehydes, as well as in the separation of polycyclic aromatic hydrocarbons. They are also useful photocatalysts under UV and simulated solar light irradiation for organic dye degradation. Further functionalization of the synthesized mesoporous hybrids makes them oxidation and acid catalysts, both with impressive performances in the fields of sustainable energy and environment.

Formation of Two- and Three-Dimensional Hybrid Mesostructures from Branched Siloxane Molecules

We report the design of a new precursor having three branching disiloxane units capable of forming 3D mesostructures with a cubic Pm-3n and its orthorhombic and tetragonal variants Cmmm and P4(2)/mnm, in addition to a conventional 2D hexagonal (p6mm) mesostructure, thus creating a novel research area of mesostructural design in silica-organic nanohybrid materials.

Self‐Assembly of Alkyl‐Substituted Cubic Siloxane Cages into Ordered Hybrid Materials

Siloxane-organic hybrids with well-ordered mesostructures were synthesized through the self-assembly of novel amphiphilic molecules that consist of cubic siloxane heads and hydrophobic alkyl tails. The monoalkyl precursors functionalized with ethoxy groups (C(n)H(2n+1)Si(8)O(12)(OEt)(7), 1 Cn, n=16, 18, and 20) were hydrolyzed under acidic conditions with the retention of the siloxane cages, leading to the formation of two-dimensional hexagonal phases by evaporation-induced self-assembly processes. Analysis of the solid-state (29)Si MAS NMR spectra of these hybrid mesostructures confirmed that the cubic siloxane units were cross-linked to form siloxane networks. Calcination of these hybrids gave mesoporous silica, the pore diameter of which varied depending on the alkyl-chain length. We also found that the precursors that had two alkyl chains formed lamellar phases, thus confirming that the number of alkyl chains per cage had a strong influence on the mesostructures. These results expand the design possibility of novel nanohybrid and nanoporous materials through the self-assembly of well-defined oligosiloxane-based precursors.

Ordered Mesoporous Materials from Metal Nanoparticle–Block Copolymer Self-Assembly

The synthesis of ordered mesoporous metal composites and ordered mesoporous metals is a challenge because metals have high surface energies that favor low surface areas. We present results from the self-assembly of block copolymers with ligand-stabilized platinum nanoparticles, leading to lamellar CCM-Pt-4 and inverse hexagonal (CCM-Pt-6) hybrid mesostructures with high nanoparticle loadings. Pyrolysis of the CCM-Pt-6 hybrid produces an ordered mesoporous platinum-carbon nanocomposite with open and large pores (>/=10 nanometers). Removal of the carbon leads to ordered porous platinum mesostructures. The platinum-carbon nanocomposite has very high electrical conductivity (400 siemens per centimeter) for an ordered mesoporous material fabricated from block copolymer self-assembly.

Design of nanohybrid and nanoporous materials through self-assembly of organosilane molecules

Structural control of silica-based materials prepared by sol-gel chemistry is important from both fundamental and practical viewpoints. This paper reviews our work on the synthesis of ordered siloxane-based nanomaterials by self-assembly of organosilane-based precursors. Lamellar siloxane-organic hybrids with various structures, macroscopic morphologies, and properties have been prepared from long-chain alkyltrialkoxysilanes or organoalkoxysilane-tetraalkoxysilane mixtures by self-assembly during hydrolysis and polycondensation. Furthermore, the molecular design of novel alkylsiloxane precursors having a large oligosiloxane head led to the formation of hybrid mesostructures consisting of cylindrical assemblies that gave ordered microporous or mesoporous silica by calcination. These results open a new self-assembly route to the design of ordered nanoporous materials as well as nanohybrid materials without the use of any templates or structure-directing agents.