Directing Gold Nanoparticles into Free‐Standing Honeycomb‐Like Ordered Mesoporous Superstructures

Abstract

www.small-journal.com 2D mesoporous materials fabricated via the assembly of nanoparticles (NPs) not only possess the unique properties of nanoscale building blocks but also manifest additional collective properties due to the interactions between NPs. In this work, reported is a facile and designable way to prepare free-standing 2D mesoporous gold (Au) superstructures with a honeycomblike configuration. During the fabrication process, Au NPs with an average diameter of 5.0 nm are assembled into a superlattice film on a diethylene glycol substrate. Then, a subsequent thermal treatment at 180 °C induces NP attachment, forming the honeycomb-like ordered mesoporous Au superstructures. Each individual NP connects with three neighboring NPs in the adjacent layer to form a tetrahedron-based framework. Mesopores confined in the superstructure have a uniform size of 3.5 nm and are arranged in an ordered hexagonal array. The metallic bonding between Au NPs increases the structural stability of architected superstructures, allowing them to be easily transferred to various substrates. In addition, electron energy-loss spectroscopy experiments and 3D finite-difference time-domain simulations reveal that electric field enhancement occurs at the confined mesopores when the superstructures are excited by light, showing their potential in nano-plasmonic applications.storage, biomedical sensing and so on. [1][2][3][4][5][6] Synthetic progress of many kinds of mesoporous materials has been achieved in the past decades, such as silica, carbon, titania, lead selenide, and metal-organic framework. [5,[7][8][9][10][11][12][13] Upon recent discovery of several metallic mesoporous structures with excellent optical and electronic properties, growing effort has been devoted to establish simple and efficient ways toward design and fabrication of metallic mesoporous materials. [14][15][16][17][18][19] Up to now, several template-based and dealloying approaches have been developed to produce metal-based mesoporous nanostructures, [2,15,17,[20][21][22][23] but some drawbacks are recognized which add limitations on the fabrication and application of metallic mesoporous materials. For example, the preparation processes are usually complex and involve harsh experimental conditions, and the harvested metallic mesoporous materials are often absent of size regularity and uniform distribution of mesopores. As a result, it is highly desired to develop a novel strategy capable of addressing such issues, enabling fabrication of highly uniform metallic mesoporous nanostructures. Nanoparticle (NP) assembly emerges as one promisingly designable way to organize monodisperse NPs into various Mesoporous nanomaterials possess a variety of distinctive geometric features, such as high surface area, large pore size, rigid structure, and 3D nanoscale framework. These unique properties allow the use of mesoporous materials for widespread applications, and examples include catalysis, energy Superstructures

Unprecedented efficient electron transport across Au nanoparticles with up to 25-nm insulating SiO2-shells

“…In the blue-visible region, higher energy electrons were excited and participated in the electron transfer, which finally increase the tunneling probability 36 . In addition, complex plasmonic nanoparticle coupling among 2D close-packed nanomembrane may also result in enhanced interaction between nanoparticles and optical radiation, which ultimately leads to the increase of tunneling current with decreasing the wavelength of light 37–39 .…”

Low‐Density 2D Superlattices Assembled via Directional DNA Bonding

“…Colloidal nanoparticle (NP) superlattices (SLs) can behave as metamaterials with unique optical, [1, 2] electrical, [3, 4] and magnetic [5] properties based on the structure‐dependent interactions between the particles that comprise them. As such, researchers have devoted significant effort towards developing methods to prepare ordered assemblies of colloidal NPs with control over various structural parameters [1, 5–8] . Colloidal crystal engineering with DNA, which utilizes DNA‐grafted NPs as “programmable atom equivalents” (PAEs), has arisen as a versatile method to fabricate SLs with remarkable control over lattice symmetry and spacing independent of the size, shape, and composition of the NP core [9–11] .…”

“…In this structure, each octahedral NP core is oriented in the ⟨111⟩ direction, and the resultant film exposes the {111} plane of a BCC SL. Notably, although 2D colloidal honeycomb SLs have been assembled using sub‐10‐nm NPs sub‐10‐nm NPs [6, 30] and micron‐sized particles, [31] this is the first time they have been prepared using NPs in the ≈100‐nm size range, which is most relevant for plasmonics and metamaterials. In fact, lithographically patterned honeycomb SLs at this length scale behave as the photonic counterpart of graphene, exhibiting extraordinary phenomena including Dirac‐like plasmons [32–34] and complete photonic band gaps [35, 36] …”

Nano-substructured plasmonic pore arrays: a robust, low cost route to reproducible hierarchical structures extended across macroscopic dimensions

“…Alternatively, self-assembled plasmonic metallic nano-particles in various lattice formations can also be employed as a SERS active substrate. 57,58 They can be fabricated with much lower cost, but oen intrinsically less reproducible methods, including 2-dimensional sphere lithography. 59,60 Low cost sphere array templating has been reported with vapour or electrodeposition of silver or most commonly gold, as described by Xu et al 61 or Bartlett et al; 62 the latter conducted an extensive study regarding the optical properties of such metallic nanocavity arrays.…”