Morphosynthesis of Nanostructured Gold Crystals by Utilizing Interstices in Periodically Arranged Silica Nanoparticles as a Flexible Reaction Field

Abstract

Nanostructural and morphological design of gold has attracted great attention because of its chemical stability, high conductivity, and quantum-size effects. Nanostructured gold materials with various morphologies [1] show unique optical properties due to their localized surface plasmon resonance [2] and catalytic activity. [3] Ordered arrays of nanostructured gold with various arrangements that depend on their morphology are also important for the fabrication of hierarchically organized functional materials.[4] However, the applications of nanostructured gold are often limited because of its tendency to form unstable aggregates. To circumvent this problem, the formation of three-dimensionally extended frameworks is quite effective. Such three-dimensionally nanostructured gold materials are stable to catalytic reactions [5] and promising for various applications, such as electrochemistry, sensing, and surface-enhanced Raman scattering. [5][6][7] However, the design of highly ordered three-dimensional gold nanostructures is quite limited because of the difficulty of controlling the growth of gold. Three-dimensional mesoporous gold materials are formed by a dealloying technique, whereas their nanostructures are not ordered.[5] Though various mesoporous metals have been prepared by soft and hard templating techniques, [8] the nanostructured gold materials prepared by using nanoscale hard templates have been limited to nanoparticles and nanowires without specific threedimensional nanostructures.[9] Colloidal templating is one of the most useful techniques to form three-dimensionally ordered macroporous materials.[10] By replicating periodically arranged silica nanoparticles with relatively small diameter, [11] three-dimensionally ordered mesoporous (3DOM) materials, such as polymers, [12] carbon, [11a] and platinum, [13,14] have been prepared. Studies on silica nanoparticles assembled into thin films, [15a] patterned structures, [15b] and one-dimensional arrays [15c] have also been reported. Although macroporous gold with submicrometer-scale periodicity is formed by using large templates, [6] disordered mesoporous gold is formed when small silica nanoparticles (ca. 50 nm) are used as templates.[13] The rapid growth of gold may cause collapse of the three-dimensional structure of templates due to the structural mismatch between templates and gold.To achieve slower crystal growth, we have focused on vapor infiltration of a reducing agent (dimethylamineborane, DMAB) to deposit gold inside the template (denoted vapor reduction). We have applied this technique for the formation of mesoporous platinum by replicating lyotropic liquid-crystalline templates [16] or colloidal crystal templates.[14]It allows both a slower reduction rate and lower reaction temperature than reduction with H 2 .[13]To our surprise, during the course of this study, many gold particles deposited in the interstices of periodically arranged silica nanoparticles by vapor reduction showed a two-dimensional morphology in spite of the three-dimen...

A Single‐Crystalline Mesoporous Quartz Superlattice

“…Mesoporous non-silica materials with single-crystalline frameworks are also very rare (e.g. gold, [21] TiO 2 , [22] and Nbdoped TiO 2 [23] ). Thepresent method is promising as ageneral concept for the design of nanostructured materials with single-crystalline frameworks.…”

Size-dependent synthesis and catalytic activities of trimetallic PdAgCu mesoporous nanospheres in ethanol electrooxidation

“…[8][9][10][11][12][13][14][15] Furthermore, noble metal MNSs with cylindrically open nanochannels and sub-100 nm sizes would further enlarge the accessibility to the reactants, facilitate reactant/product transfer, accelerate the reaction kinetics, and thus enhance the (electro)catalytic performance. [16][17][18][19][20] During the past few decades, dozens of synthetic methods and techniques, including the hardtemplating method, [21][22][23] so-templating method, 14,[24][25][26][27] and solution-phase approach, 28,29 have been employed to fabricate various nanosized MNSs with monometallic or multimetallic compositions. However, in most cases, successful synthesis of nanosized noble metal MNSs (<100 nm) consisted of spherical mesopores and uncontinuous frameworks, [30][31][32] which kinetically inhibited the mass transfer inside mesopores and electron transfer on mesoporous frameworks during the (electro)catalysis.…”

Mesoporous gold nanospheres via thiolate–Au(i) intermediates

“…mesoAu) is (electro)catalytically more active, due to large surface areas, highly accessible inner sites and abundance of low-coordination surface atoms 11–14. To date, various nanosynthesis methodologies and techniques, including alloying–dealloying,7,15,16 electrochemical reduction,12,17,18 soft-/hard-templating,12,13,19–21 and other methods,22–24 have been used to generate mesoAu. However, the accessible morphologies were generally limited to powders with irregular shapes or films on conductive substrates.…”