Construction of the single-diamond-structured titania scaffold-Recreation of the holy grail photonic structure.

As one of the most stunning biological nanostructures, the single-diamond (SD) surface discovered in beetles and weevils exoskeletons possesses the widest complete photonic bandgap known to date and is renowned as the "holy grail" of photonic materials. However, the synthesis of SD is difficult due to its thermodynamical instability compared to the energetically favoured bicontinuous double diamond and other easily formed lattices; thus, the artificial fabrication of SD has long been a formidable challenge. Herein, we report a bottom-up approach to fabricate SD titania networks via a one-pot cooperative assembly scenario employing the diblock copolymer poly(ethylene oxide)-block-polystyrene as a soft template and titanium diisopropoxide bis(acetylacetonate) as an inorganic precursor in a mixed solvent, in which the SD scaffold was obtained by kinetically controlled nucleation and growth in the skeletal channels of the diamond minimal surface formed by the polymer matrix. Electron crystallography investigations revealed the formation of tetrahedrally connected SD frameworks with the space group Fd [Formula: see text] m in a polycrystalline anatase form. A photonic bandgap calculation showed that the resulting SD structure has a wide and complete bandgap. This work solves the complex synthetic enigmas and offers a frontier in hyperbolic surfaces, biorelevant materials, next-generation optical devices, etc.

Spin Selectivity of Chiral Mesostructured Iron Oxides with Different Magnetisms.

Spin selectivity physically depends on either magnetic materials with strong internal magnetic fields or symmetry-breaking materials with large spin-orbit coupling (SOC). However, the spin selectivity of symmetry-breaking magnetic materials is not understood. Herein, the spin selectivity of iron oxides with different magnetisms arising from varying spin alignment is investigated. Chiral mesostructured films of Fe3 O4 (CMFFs), γ-Fe2 O3 (CMγFs), and α-Fe2 O3 (CMαFs), which share the same mesostructure, are prepared by a controllable calcination process of chiral mesostructured FeOOH films (CMOFs) grown on the substrate via an amino acid-induced hydrothermal route. CMFFs and CMγFs with ferrimagnetism exhibit magnetic field-dependent and simultaneously chirality-independent magnetic circular dichroism (MCD) signals, while CMαFs with antiferromagnetism exhibit chirality-dependent, magnetic field-independent MCD signals. It is speculated that the competitive effect between the spin alignment-induced and chirality-induced effective magnetic fields determines the energy splitting of opposite spins in the materials with different magnetisms.

DNA-Assisted Creation of a Library of Ultrasmall Multimetal/Metal Oxide Nanoparticles Confined in Silica.

Supported ultrasmall metal/metal oxide nanoparticles (UMNPs) with sizes in the range of 1-5 nm exhibit unique properties in sensing, catalysis, biomedicine, etc. However, the metal-support and metal-metal precursor interactions were not as well controlled to stabilize the metal nanoparticles on/in the supports. Herein, DNA is chosen as a template and a ligand for the silica-supported UMNPs, taking full use of its binding ability to metal ions via either electrostatic or coordination interactions. UMNPs thus are highly dispersed in silica via self-assembly of DNA and DNA-metal ion interactions with the assistance of a co-structural directing agent (CSDA). A large number of metal ions are easily retained in the mesostructured DNA-silica materials, and their growth is controlled by the channels after calcination. Based on this directing concept, a material library, consisting of 50 mono- and 54 bicomponent UMNPs confined within silica and with narrow size distribution, is created. Theoretical calculation proves the indispensability of DNA with combination of several organics in the synthesis of ultrasmall metal nanoparticles. The Pt-silica and Pt/Ni-silica chosen from the library exhibit good catalytic performance for toluene combustion. This generalizable and straightforward synthesis strategy is expected to widen the corresponding applications of supported UMNPs.

Self-Assembly of Single-Diamond-Surface Networks.

Biological scaffolds with hyperbolic surfaces, especially single gyroid and single-diamond structures, have sparked immense interest for creating novel materials due to their extraordinary physical properties. However, the ability of nature to create these unbalanced surfaces has not been achieved in either lyotropic liquid crystals or block copolymer phases due to their thermodynamical instability in these systems. Here, we report the synthesis of a porous silica scaffold with a single-diamond-surface structure fabricated by self-assembly of the poly(ethylene oxide)-b-polystyrene-b-poly(L-lactide) and silica precursors in a mixed solvent of tetrahydrofuran and water. The single-diamond structure with tetrahedral interconnected frameworks was revealed by the electron crystallographic reconstruction. We assume that the formation of single networks is induced by the structural transition and related to the energetic change due to the fluctuations of the Gaussian curvature. This work may provide new insights into these biologically relevant surfaces and related self-assembly systems.

Resistance-Chiral Anisotropy of Chiral Mesostructured Half-metallic Fe3 O4 Films.

Half-metallic materials are theoretically predicted to be metallic and insulating, which have not been confirmed experimentally, and the predictions are still in doubt. We report the resistance-chiral anisotropy (R-ChA), i.e., chirality-dependent electrical conductivity, in chiral mesostructured Fe3 O4 films (CMFFs) grown on the substrates via a hydrothermal method using amino acids as symmetry-breaking agents. Two levels of chirality exist in the CMFFs: primary distortion of the crystal lattice forms twisted nanoflakes, and secondary helical stacking of nanoflakes forms fan-shaped nanoplates. At temperatures below 30 K, the CMFFs exhibited metallic conductivity and insulation for one handedness and the other, respectively. The chirality-dependent effective magnetic fields were speculated to stabilize the opposite spin in the antipodal chiral frame, which led to the free transport of electrons in one handedness of the chiral structure and immobility for the other handedness.

Chiral Mesostructured NiO Films with Spin Polarisation.

Spin polarisation is found in the centrosymmetric nonferromagnetic crystals, chiral mesostructured NiO films (CMNFs), fabricated through the symmetry-breaking effect of a chiral molecule. Two levels of chirality were identified: primary nanoflakes with atomically twisted crystal lattices and secondary helical stacking of the nanoflakes. Spin polarisation of the CMNFs was confirmed by chirality-dependent magnetic-tip conducting atomic force microscopy (mc-AFM) and magnetic field-independent magnetic circular dichroism (MCD). Electron transfer in the symmetry-breaking electric field was speculated to create chirality-dependent effective magnetic fields. The asymmetric spin-orbit coupling (SOC) generated by effective magnetic fields selectively modifies the opposite spin motion in the antipodal CMNFs. Our findings provide fundamental insights for directional spin control in unprecedented functional inorganic materials.

Chiral Mesostructured BiOBr Films with Circularly Polarized Colour Response.

Achieving strong and broadband circularly polarized colour responses in chiral inorganic materials is challenging. Here, we fabricated chiral mesostructured bismuth oxybromide (BiOBr) films (CMBFs) via hydrothermal growth using chiral sugar alcohols as symmetry-breaking agents. The layered slabs of BiOBr crystals with weak van-der-Waals interactions are prone to mismatching due to the chiral driving force, resulting in hierarchically chiral arrangements of fine size. Three levels of chirality exist in the CMBFs: primary, helical distortion crystal lattices of a nanoflake, secondary, helical stacking of nanoflakes to form nanoplates, and tertiary, chiral vortexes arranged by nanoplates. The CMBFs displayed optical activities (OAs) over a wide wavelength range of 350-2500 nm with an anisotropic factor of up to 0.99, which led to a significant chirality-dependent colour response to circularly polarized light. The high selectivity can be considered as the result of enhanced resonance due to structural-handedness matching and the synergistic effect of multiple OAs.

Library Creation of Ultrasmall Multi-metallic Nanoparticles Confined in Mesoporous MFI Zeolites.

The development of materials integrated with ultrasmall multi-metal nanoparticles (UMMNs) and mesoporous zeolite is a considerable challenge in chemistry and materials science. We designed a trifunctional surfactant, in which the pyridyl benzimidazole in the hydrophobic tail generates the mesopores through π-π stacking; the diquaternary ammonium in the hydrophilic headgroup direct the formation of MFI zeolite sheets and the nitrogen atoms in the heterocyclic rings coordinate with various metal ions to form UMMNs confined in the zeolite matrix after calcination and reduction. A library of 56 UMMNs confined within both micropores and mesopores of MFI zeolites (MMZs) with 4 mono-, 14 bi- and 38 tri-metallic nanoparticles (sizes of 1.3-4.7 nm) of combinations of Rh, Pd, Pt, Au, Fe, Co, Ni, Cu and Zn were made. An improved catalytic performance was exhibited in the sequence of Rh-MMZ

π-π Interactions Between Aromatic Groups in Amphiphilic Molecules: Directing Hierarchical Growth of Porous Zeolites.

The development of hierarchical macro- or mesoporous zeolites is essential in zeolite synthesis because the size of the micropores limits mass transport and their use as industrial catalysts for bulky molecules. Although major breakthroughs have been achieved, fabricating crystallographically ordered mesoporous zeolites using a templating strategy is still an unsolved challenge. This minireview highlights our recent efforts on the self-assembly of amphiphilic molecules to obtain ordered hierarchical MFI zeolites by introducing aromatic groups into the hydrophobic tail of the amphiphilic molecules. Owing to the geometric matching between the self-assembled aromatic tails and the MFI framework, a) single-crystalline mesostructured zeolite nanosheets (SCZNs), b) SCZNs with a 90° rotational intergrowth structure, c) a hierarchical MFI zeolite with a two-dimensional square P4mm mesostructure, and d) a single-crystalline mesoporous ZSM-5 with three-dimensional pores and sheetlike mesopores layered along the a-axis were successfully synthesized.

Enantiomeric Discrimination by Surface-Enhanced Raman Scattering-Chiral Anisotropy of Chiral Nanostructured Gold Films.

A surface-enhanced Raman scattering-chiral anisotropy (SERS-ChA) effect is reported that combines chiral discrimination and surface Raman scattering enhancement on chiral nanostructured Au films (CNAFs) equipped in the normal Raman scattering Spectrometer. The CNAFs provided remarkably higher enhancement factors of Raman scattering (EFs) for particular enantiomers, and the SERS intensity was proportional to the enantiomeric excesses (ee) values. Except for molecules with mesomeric species, all of the tested enantiomers exhibited high SERS-ChA asymmetry factors (g), ranging between 1.34 and 1.99 regardless of polarities, sizes, chromophores, concentrations and ee. The effect might be attributed to selective resonance coupling between the induced electric and magnetic dipoles associated with enantiomers and chiral plasmonic modes of CNAFs.

One-Pot Synthesis and Formation Mechanism of Hollow ZSM-5.

Coffin-shaped hollow ZSM-5 zeolite (HZZ) particles with shell thickness of about 200 nm and hollow diameter of approximately 1.5 µm were synthesized in one pot by using tetrapropylammonium bromide (TPABr), aluminum triisopropoxide Al[OCH(CH3 )2 ]3 and tetraethoxysilane (TEOS) as the structure-directing agent (SDA), aluminum and silica source, respectively. The appropriate molar ratios of TPABr/SiO2 and Si/Al as well as suitable crystallization temperature are the key factors for the formation of HZZ. The formation of the HZZ can be attributed to the existence of intrinsic density variation inside the initial amorphous aggregates and the Al zoning in the outer surface of the ZSM-5 particles. Amorphous silica with low crystallinity formed at early stages and low Al concentration, which has been subsequently dissolved and recrystallized on the ZSM-5 particle surface through Ostwald ripening, leading to the formation of HZZ. This approach, which uses a high concentration of SDA, will provide new possibilities and insight into the prospective fabrication of hollow zeolites.

Single-Crystalline MFI Zeolite with Sheet-Like Mesopores Layered along the a Axis.

Designing a templating strategy for directing mesopore growth along different crystallographic directions is essential for fabricating two- or three-dimensional single-crystalline mesoporous zeolites. However, so far, mesopores formed in MFI zeolites by soft templates have mostly been generated by disrupting growth along the b axis; generating mesopores by disrupting growth along the a axis is rare. Herein, a single-crystalline mesoporous MFI zeolite (SCMMZ) with sheet-like mesopores layered along the a and b axes was synthesized using a triply branched surfactant with diquaternary ammonium groups connected to 1,3,5-triphenylbenzene by a six- and eight-carbon alkyl chain (TPB-6 and 8). The sheet-like mesopores were embedded in the MFI framework and were retained even after calcination. Molecular mechanics calculations provided evidence of low binding energy configurations of the surfactant that directed the growth of straight and zigzag channels along the b and a axes, respectively. The formation of nanosheets was attributed to the geometric matching of the arrangement of the aromatic groups to the zeolite framework.

Topotactic Conversion of Alkali-Treated Intergrown Germanosilicate CIT-13 into Single-Crystalline ECNU-21 Zeolite as Shape-Selective Catalyst for Ethylene Oxide Hydration.

The conversion of the alkali-treated intergrowth germanosilicate CIT-13 into the single-crystalline high-silica ECNU-21 (named after East China Normal University) zeolite, with a novel topology and a highly crystalline zeolite framework, has been realized through a creative top-down strategy involving a mild alkaline-induced multistep process consisting of structural degradation and reconstruction. Instead of acid treatment, hydrolysis in aqueous ammonia solution not only readily cleaved the chemically weak Ge(Si)-O-Ge bonds located within the interlayer double four ring (D4R) units of CIT-13, but also cleaved the metastable Si-O-Si bonds therein. This led to extensive removal of the D4R units, and also generated silanol groups on adjacent silica-rich layers, which then condensed to form a novel daughter structure upon calcination. Individual oxygen bridges in the reassembled ECNU-21 replaced the germanium-rich D4R units in CIT-13, thereby eliminating the original intergrowth phenomenon along the b axis. With an ordered crystalline structure of 10-ring (R) channels as well as suitable germanium-related Lewis acid sites, ECNU-21 serves as a stable solid Lewis acid catalyst for the shape-selective hydration of ethylene oxide (EO) to ethylene glycol (EG) at greatly reduced H2 O/EO ratios and reaction temperature in comparison with the noncatalytic industrial process.

Fabrication of Photonic Bandgap Materials by Shifting Double Frameworks.

Biological organisms have evolved over millions of years to generate tremendously complex structures on a nanometer to micrometer scale. Among them, a range of three-dimensional (3D) biological photonic structures with minimal surface or constant mean curvature surfaces have been discovered in the wing scales of insects, attracting a great deal of interest because of their unique optical properties, such as structural color, antireflection, light collection, and photonic band gaps. Single-diamond and single-gyroid surface structures are considered to be excellent photonic crystals with complete band gaps. Although the corresponding bicontinuous architectures have been synthesized by self-assembly, single-framework structures are thermodynamically unfavorable and have been only achieved by physical fabrications and the alternating gyroid method. The production of materials derived from the thermodynamically stable double-framework structures provides a feasible solution for their chemical construction. This concept article highlights the significant progress in understanding 3D photonic structures by shifting double-frameworks to form low-symmetry structures, the physical properties of which can be greatly altered. Specifically, a complete photonic band gap can be achieved via a shifted double-diamond structure composed of materials with high dielectric contrast and high refractive index. We believe this concept will provide new insights in interdisciplinary research areas including the study of photonic structures, the self-assembly of amphiphilic molecules and the formation of biological architectures.

Hierarchical MFI Zeolites with a Single-Crystalline Sponge-Like Mesostructure.

Single-crystalline sponge-like MFI mesoporous zeolites (SSMZs) have been synthesized by using bolaform surfactants with an axial chiral binaphthyl core in the hydrophobic tail and triquaternary ammonium head groups, as bifunctional organic structure-directing agents (OSDAs). By changing the length of alkyl chain between a triquaternary ammonium head group and a binaphthyl group from 4 to 10 carbons, SSMZs with high specific surface area (382-434 m2 g-1 ), abundant micropore-mesopore connectivity, and uniform mesopore diameter (4-10 nm) were obtained. OSDAs with an alkyl chain length of 11 and 12 carbons led to the formation of nanorod-constructed mesoporous MFI zeolites. A geometrical matching between the cylindrical arrangement of the binaphthyl groups and the zeolitic framework is speculated to be the key factor for the formation of mesoporous zeolites. The SSMZ zeolites, with abundant mesopores beneficial for the diffusion of reactants, exhibited significantly higher catalytic efficiencies than those of the conventional ZSM-5 with a microcrystal morphology (≈1.5 µm).

Mesoporous MFI Zeolite with a 2D Square Structure Directed by Surfactants with an Azobenzene Tail Group.

Mesoporous MFI zeolites (MMZs) have been constructed by using the surfactant-containing azobenzene segment in the hydrophobic tail. The cylindrical π-π stacking of azeobenzene groups is considered to be the key factor to form the ordered mesostructure through cooperative structural matching and the rearrangement of MFI frameworks. The mesostructure has been tuned from a disordered hierarchical arrangement into an ordered 2D square p4mm structure by changing the length of the alkyl chain between the diquaternary ammonium head group and azobenzene group. The geometric matching between the MFI zeolitic framework and the alkyl chain length plays an important role in the construction of the crystallographically correlated mesostructure with 2D square ordering. A combination of X-ray diffraction patterns and electron microscopy studies provides visible evidence for the mesostructural transformation from a short-range hexagonal or lamellar ordering to 2D square mesostructure.

A Hierarchical MFI Zeolite with a Two-Dimensional Square Mesostructure.

A conceptual design and synthesis of ordered mesoporous zeolites is a challenging research subject in material science. Several seminal articles report that one-dimensional (1D) mesostructured lamellar zeolites are possibly directed by sheet-assembly of surfactants, which collapse after removal of intercalated surfactants. However, except for one example of two-dimensional (2D) hexagonal mesoporous zeolite, no other zeolites with ordered 2D or three-dimensional (3D) mesostructures have been reported. An ordered 2D mesoporous zeolite can be templated by a cylindrical assembly unit with specific interactions in the hydrophobic part. A template molecule with azobenzene in the hydrophobic tail and diquaternary ammonium in the hydrophilic head group directs hierarchical MFI zeolite with a 2D square mesostructure. The material has an elongated octahedral morphology, and quaternary, ordered, straight, square channels framed by MFI thin sheets expanded along the a-c planes and joined with 90° rotations. The structural matching between the cylindrical assembly unit and zeolite framework is crucial for mesostructure construction.

Silica Scaffold with Shifted "Plumber's Nightmare" Networks and their Interconversion into Diamond Networks.

Bicontinuous structures with hyperbolic surfaces have been found in a variety of natural and synthetic systems. Herein, we present the synthesis and structural study of the shifted double-primitive networks, which is known as the rare "plumber's nightmare", and its interconversion into diamond networks. The scaffold was prepared by self-assembly of an amphiphilic triblock terpolymer and silica precursors. Electron crystallography indicates that the structure consists of two sets of hollow primitive networks shifted along 0.75b and 0.25c axes (2pcu(38 63), space group Cmcm). The "side-by-side" epitaxial relationship of the primitive and diamond networks with unit cell ratio of about 1.30 has been directly observed with the intermediate surface related to the rPD family. These results bring new insights to previous theoretical studies.

Silver Films with Hierarchical Chirality.

Physical fabrication of chiral metallic films usually results in singular or large-sized chirality, restricting the optical asymmetric responses to long electromagnetic wavelengths. The chiral molecule-induced formation of silver films prepared chemically on a copper substrate through a redox reaction is presented. Three levels of chirality were identified: primary twisted nanoflakes with atomic crystal lattices, secondary helical stacking of these nanoflakes to form nanoplates, and tertiary micrometer-sized circinates consisting of chiral arranged nanoplates. The chiral Ag films exhibited multiple plasmonic absorption- and scattering-based optical activities at UV/Vis wavelengths based on their hierarchical chirality. The Ag films showed chiral selectivity for amino acids in catalytic electrochemical reactions, which originated from their primary atomic crystal lattices.

A Shifted Double-Diamond Titania Scaffold.

Photonic crystals are expected to be metamaterials because of their potential to control the propagation of light in the linear and nonlinear regimes. Biological single-network, triply periodic constant mean curvature surface structures are considered excellent candidates owing to their large complete band gap. However, the chemical construction of these relevant structures is rare and developing new structures from thermodynamically stable double-network self-organizing systems is challenging. Herein, we reveal that the shifted double-diamond titania scaffold can achieve a complete band gap. The largest (7.71 %) band gap is theoretically obtained by shifting 0.332 c with the dielectric contrast of titania (6.25). A titania scaffold with similar shifted double-diamond structure was fabricated using a reverse core-shell microphase-templating system with an amphiphilic diblock copolymer and a titania source in a mixture of tetrahydrofuran and water, which could result in a 2.05-3.78 % gap.