Liquid‐Crystal Templating in Ammonia: A Facile Route to Micro‐ and Mesoporous Metal Nitride/Carbon Composites

Qi, Hao; Roy, Xavier; Shopsowitz, Kevin E.; Hui, Joseph K.-H.; MacLachlan, Mark J.

doi:10.1002/ange.201004974

Cited by 7 publications

(3 citation statements)

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“…At the same time, the material may exhibit excellent catalytic properties. Thus far, helical silica, 21 organosilica, 85 TiO 2 , 84 a metal nitride/carbon composite 87 and carbon 86 have been produced in this way.…”

Section: Toward Structure Control and Applications Of Self-assembled mentioning

confidence: 99%

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

et al. 2014

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Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations-some constituting severe obstacles for applications of CNCs-may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies. NPG Asia Materials (2014) 6, e80; doi:10.1038/am.2013.69; published online 10 January 2014Keywords: cholesteric; gel; glass; liquid crystal; nanocellulose; photonic crystal; self-assembly INTRODUCTION Nanomaterials based on renewable resources are attracting rapidly growing interest, both from a fundamental scientific point of view and from the perspective of developing novel structural and functional macroscopic materials. 1,2 Using nature-based nanomaterials offers ecological advantages, and the extraordinary mechanical performance and/or photonic crystal character of biological composites such as bone, nacre, wood, beetle scales and butterfly wings is also an important inspiration for the development of new multifunctional materials. [3][4][5] However, full utilization of the intrinsic properties of nanosized starting materials requires the development of robust and versatile synthetic and processing routes to control assembly over several length scales. [6][7][8] Cellulose, one of the most versatile and widely found biopolymers in nature, has been used by humans for millennia as a building material, an energy source, a component of clothing and for storing and sharing knowledge and culture. Today, cellulose materials are used in a wide range of applications, and the paper and pulp industry

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Section: Toward Structure Control and Applications Of Self-assembled mentioning

confidence: 99%

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

et al. 2014

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“…[1][2][3] Although silica can be prepared with a variety of periodic structures (for example, lamellar, hexagonal, cubic) and pore sizes by aqueous sol-gel methods using a surfactant template, [4,5] this method cannot generally be applied to other materials. [8][9][10][11][12] On the other hand, by using porous silica as a hard template, diverse nanostructured materials may be obtained with a wide variety of compositions (carbon, polymers, noble metals, and metal oxides) after etching of the silica. Sometimes these problems can be overcome by using chelating ligands or by a judicious choice of solvent and template.…”

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Hard Templating of Nanocrystalline Titanium Dioxide with Chiral Nematic Ordering

et al. 2012

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Anatase TiO(2) nanocrystals have been organized into high-surface-area (150-230 m(2) g(-1)) mesoporous films with long-range chiral nematic ordering. The chiral structure of the anatase films causes them to selectively reflect circularly polarized light and appear iridescent. These materials show replication of structural features found in the silica template on nanometer to millimeter length scales.

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“…Sometimes these problems can be overcome by using chelating ligands or by a judicious choice of solvent and template. [8][9][10][11][12] On the other hand, by using porous silica as a hard template, diverse nanostructured materials may be obtained with a wide variety of compositions (carbon, polymers, noble metals, and metal oxides) after etching of the silica. [13][14][15][16][17][18] The thermal stability of silica also allows for the use of high-temperature treatments to generate highly crystalline mesoporous products that may be otherwise difficult to obtain.The hard-templating approach has been applied to the synthesis of various novel mesoporous materials.…”

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Hard Templating of Nanocrystalline Titanium Dioxide with Chiral Nematic Ordering

et al. 2012

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Hard templating (also called nanocasting) has emerged as a powerful method for constructing new solid-state materials with periodic order. [1][2][3] Although silica can be prepared with a variety of periodic structures (for example, lamellar, hexagonal, cubic) and pore sizes by aqueous sol-gel methods using a surfactant template, [4,5] this method cannot generally be applied to other materials. [6,7] This limitation stems from the fact that the required precursor for many materials either condenses too quickly, disrupts the organization of the surfactant, or is not compatible with aqueous chemistry (for example, in the preparation of metal nitrides). Sometimes these problems can be overcome by using chelating ligands or by a judicious choice of solvent and template. [8][9][10][11][12] On the other hand, by using porous silica as a hard template, diverse nanostructured materials may be obtained with a wide variety of compositions (carbon, polymers, noble metals, and metal oxides) after etching of the silica. [13][14][15][16][17][18] The thermal stability of silica also allows for the use of high-temperature treatments to generate highly crystalline mesoporous products that may be otherwise difficult to obtain.The hard-templating approach has been applied to the synthesis of various novel mesoporous materials. Yue et al. recently reported the synthesis of mesoporous rutile and anatase TiO 2 using SBA-15 silica as the hard template, [19] and other hard templates have been employed in the synthesis of nanostructured titania. [20] High-surface-area nanocrystalline TiO 2 is of particular interest for applications, such as dyesensitized solar cells, [21] photocatalysts, [22] gas sensors, [23] and batteries. [24] The incorporation of high-surface-area anatase TiO 2 into photonic structures is a further challenge that has recently garnered attention. [25,26] By using titania in colloidal crystals and inverse opals, the high refractive index of TiO 2 (n = 2.5-2.9) can impart a complete photonic bandgap in these materials.To date, the synthesis of mesoporous materials has been mainly limited to the ordered pore structures obtained from the lyotropic liquid crystalline phases of surfactants and block copolymers. We have recently developed a new class of mesoporous materials with chiral nematic pore structures templated by the lyotropic liquid-crystalline phase of nanocrystalline cellulose (NCC). [27][28][29] Condensation of a silica precursor (Si(OMe) 4 in the current study) in the presence of nanocrystalline cellulose affords a composite material in which the SiO 2 surrounds NCC with a chiral nematic organization. Upon removal of the cellulose template, a porous silicate is obtained as a free-standing film that has a long-range chiral nematic structure, resulting in photonic properties. By varying the pitch of the chiral nematic composites, mesoporous materials with tunable photonic properties are obtained.Herein, we present the synthesis of mesoporous anatase TiO 2 using chiral nematic mesoporous silica films as a hard te...

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Liquid‐Crystal Templating in Ammonia: A Facile Route to Micro‐ and Mesoporous Metal Nitride/Carbon Composites

Cited by 7 publications

References 50 publications

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

Hard Templating of Nanocrystalline Titanium Dioxide with Chiral Nematic Ordering

Hard Templating of Nanocrystalline Titanium Dioxide with Chiral Nematic Ordering

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