Zhehao Huang

Silica Biomineralization via the Self‐Assembly of Helical Biomolecules

The biomimetic synthesis of relevant silica materials using biological macromolecules as templates via silica biomineralization processes attract rapidly rising attention toward natural and artificial materials. Biomimetic synthesis studies are useful for improving the understanding of the formation mechanism of the hierarchical structures found in living organisms (such as diatoms and sponges) and for promoting significant developments in the biotechnology, nanotechnology and materials chemistry fields. Chirality is a ubiquitous phenomenon in nature and is an inherent feature of biomolecular components in organisms. Helical biomolecules, one of the most important types of chiral macromolecules, can self-assemble into multiple liquid-crystal structures and be used as biotemplates for silica biomineralization, which renders them particularly useful for fabricating complex silica materials under ambient conditions. Over the past two decades, many new silica materials with hierarchical structures and complex morphologies have been created using helical biomolecules. In this review, the developments in this field are described and the recent progress in silica biomineralization templating using several classes of helical biomolecules, including DNA, polypeptides, cellulose and rod-like viruses is summarized. Particular focus is placed on the formation mechanism of biomolecule-silica materials (BSMs) with hierarchical structures. Finally, current research challenges and future developments are discussed in the conclusion.

Optically Active Nanostructured ZnO Films

Inorganic nanomaterials endowed with hierarchical chirality could open new horizons in physical theory and applications because of their fascinating properties. Here, we report chiral ZnO films coated on quartz substrates with a hierarchical nanostructure ranging from atomic to micrometer scale. Three levels of hierarchical chirality exist in the ZnO films: helical ZnO crystalline structures that form primary helically coiled nanoplates, secondary helical stacking of these nanoplates, and tertiary nanoscale circinate aggregates formed by several stacked nanoplates. These films exhibited optical activity (OA) at 380 nm and in the range of 200-800 nm and created circularly polarized luminescence centered at 510 nm and Raman OA at 50-1400 cm(-1) , which was attributed to electronic transitions, scattering, photoluminescent emission, and Raman scattering in a dissymmetric electric field. The unprecedented strong OA could be attributed to multiple light scattering and absorption-enhanced light harvesting in the hierarchical structures.

Rigid bolaform surfactant templated mesoporous silicon nanofibers as anode materials for lithium-ion batteries

Mesoporous silicon nanofibers were synthesised by magnesiothermic reduction of earthworm-like, lamellar structured silica nanotubes for use in developing highly efficient lithium ion batteries. The silica nanotubes resulted from the single-molecular-layer arrangement of a bolaamphiphile surfactant. The calcined mesoporous silica nanotubes transformed into mesoporous silicon nanofibers (nf-Si) after magnesiothermic reduction. Finally, carbon-layer-coated silicon nanofibers (nf-Si@C) were obtained by chemical vapour deposition (CVD), which displayed a stable capacity of approximately 1141 mA h g−1 over 100 cycles at 0.2 C.

Optically active chiral Ag nanowires

Chiral Ag nanowires (CAgNWs), fabricated inside chiral carbon nanotubes (CCNTs), exhibit strong circular dichroism (CD) signals in the visible and near-IR regions. Enantiopure CCNTs were prepared by carbonization of the self-assembled chiral polypyrrole nanotubes according to our previous report. Ag ions could be easily introduced into the chiral pores of CCNTs due to the capillary phenomenon. After hydrogen reduction, the optically active CAgNWs formed inside the channels of the CCNTs. The helical channels in the CCNTs played a predominant effect on the chiral formation of the CAgNWs. This system provides new insight into the fabrication as well as the study of optical activity (OA) of chiral inorganic nanomaterials. Such novel chiral inorganic material will bring new opportunities in non-linear optics, biosensors and chiral recognition.中文摘要本文以手性碳纳米管为模板, 成功地在其内部形成了手性银纳米线. 由于手性排列的银纳米线之间的集合耦合效应, 在可见光区和近红外区产生了较强的手性圆二色信号. 根据我们先前报道的方法, 通过碳化处理自组装合成的手性吡咯碳纳米管得到了单一手性的碳纳米管. 由于毛细管效应, 银离子能够很容易地进入手性碳纳米管的手性孔道中, 然后再通过氢气高温还原, 在其管内得到了具有光学活性的手性银纳米线. 手性碳纳米管内的螺旋孔道对手性银纳米线的形成起模板作用. 该合成体系将有助于理解具有手性光学活性的无机材料的形成及其机理. 这种新颖的手性无机材料也将有机会应用到非线性光学器件、生物传感和手性识别等领域.

Design of Amphiphilic Peptide Geometry towards Biomimetic Self-Assembly of Chiral Mesoporous Silica

In nature, diatoms and sponges are exquisite examples of well-defined structures produced by silica biomineralisation, in which proteins play an important role. However, the artificial peptide templating route for the silica mesostructure remains a formidable and unsolved challenge. Herein, we report our effort on the design of amphiphilic peptides for synthesising a highly ordered two-dimensional (2D)-hexagonal and lamellar chiral silica mesostructure using trimethoxysilylpropyl-N,N,N-trimethylammonium chloride as the co-structure directing agent (CSDA). The geometry of the peptide was designed by adding proline residues into the hydrophobic chain of the peptide to break the b-sheet conformation by weakening the intermolecular hydrogen bonds; this led to the mesophase transformation from the most general lamellar structure to the 2D hexagonal P6mm mesostructure by increasing the amphiphilic molecules packing parameter g. Enantiomerically pure chiral mesostructures were formed thanks to the intrinsic chirality and relatively strong intermolecular hydrogen bonds of peptides.

Control of chiral nanostructures by self-assembly of designed amphiphilic peptides and silica biomineralization.

Peptides, the fundamental building units of biological systems, are chiral in molecular scale as well as in spatial conformation. Shells are exquisite examples of well-defined chiral structures produced by natural biomineralization. However, the fundamental mechanism of chirality expressed in biological organisms remains unclear. Here, we present a system that mimics natural biomineralization and produces enantiopure chiral inorganic materials with controllable helicity. By tuning the hydrophilicity of the amphiphilic peptides, the chiral morphologies and mesostructures can be changed. With decreasing hydrophilicity of the amphiphilic peptides, we observed that the nanostructures changed from twisted nanofibers with a hexagonal mesostructure to twisted nanoribbons with a lamellar mesostructure, and the extent of the helicity decreased. Defining the mechanism of chiral inorganic materials formed from peptides by noncovalent interactions can improve strategies toward the bottom-up synthesis of nanomaterials as well as in the field of bioengineering.

Hard-templating of chiral TiO2 nanofibres with electron transition-based optical activity

Abstract The fabrication of optically active inorganic nanomaterials with chiral superstructures attracts attention because of their potential applications in chemical sensing and non-linear optics. Here, we present a facile way to prepare TiO2 nanofibres, in which the nanocrystals are helically arranged into a chiral superstructure. Notably, the chiral superstructure shows strong optical activity due to the difference of absorbing left- and right-handed circularly polarized light. This special optical activity resulted from electron transition from the valence band to the conduction band of TiO2 through a vicinal effect of helically arranged TiO2 nanocrystals.

Fabrication of Chiral Materials via Self-Assembly and Biomineralization of Peptides

With different scales of chirality, chiral materials have various particular properties and potential applications in many fields. Peptides are the fundamental building units of biological systems, and a variety of ordered functional nanostructures are produced through self-assembly and biomineralization of peptides in nature. This Personal Account describes chiral silica materials fabricated by using amphiphilic peptides as building blocks. Three particular biomineralization approaches are described based on different kinds of geometry of amphiphilic peptides: the influence of the specific amino acid proline in the peptide sequence, the hydrophilicity of amphiphilic peptides, and different kinds of hydrophobic tails in amphiphilic peptides. These strategies are useful for designing peptides toward the bottom-up synthesis of nanomaterials as well as improving the understanding of the mechanism of peptide self-assembly.

Synthesis of Zeolite/Mesoporous Silica Composite Microspheres by Microemulsion Method

Zeolite/mesoporous silica composite microspheres (ZMMS) have been prepared by self-assembling mesoporous silica phase with Y or Ti-MWW zeolites crystallites in a simple microemulsion system. The synthesis process involved the formation of a stable O/W microemulsion from silica precursor of tetrabutyl orthosilicate and cationic quaternary ammonium surfactants as well as a simultaneous assembling of zeolite into the oil phase by their hydrophobic interaction, in which mesoporous silica was formed by self-assembling of surfactant and silica source. Through optimizing synthesis conditions, the ZMMS materials were prepared to possess controllable mass ratio of zeolite to mesoporous silica (0—2.3) and sphere diameter (186—965 μm). The mesopore sizes of the ZMMSs were 3.75 (zeolite-Y/MMSs) and 3.98 nm (Ti-MWW/MMSs). In the liquid-phase ammoximation of cyclohexanone, Ti-MWW/mesoporous silica microspheres showed a high mechanical stability and a catalytic activity comparable to the parent Ti-MWW powders. Keywords zeolite microsphere; micro/mesoporous composite; microemulsion; zeolite-Y; Ti-MWW