Functional helical silica nanofibers with coaxial mixed mesostructures for the fabrication of PtCo nanowires that display unique geometry-dependent magnetism

Abstract

Helical mesoporous silicas are notable from a self-assembly and applications points of view. We report a novel confinement-free synthesis of chloropropyl-functionalized helical mesoporous silica nanofibers (CP-HMSNFs) possessing straight channels at the fiber center surrounded by concentric short-pitch helical channels. The chloropropyl groups are found mainly distributed at the central cylindrical portion of the fibers, allowing the selective inclusion of guest species to fabricate novel nanocomposite fibers. Moreover, the chloropropyl-functionalized nanofibers were applied as a hard template to fabricate helical platinum-cobalt (PtCo) alloy nanowires with small and narrowly distributed radii of gyration. The helical metal nanowires exhibited distinct ferromagnetic properties as compared with their straight counterpart. NPG Asia Materials (2015) 7, e181; doi:10.1038/am.2015.39; published online 22 May 2015 INTRODUCTIONHelical mesoporous silicas 1-11 are analogous to the self-assembled helical biomaterials in nature and have attracted a substantial amount of attention. These helical silicas are also promising hard templates for the preparation of helical nanowires composed of metals [12][13][14][15] or other compositions that may possess unique optical, 16,17 electromagnetic 9,18 or other properties. Efforts to understand the formation mechanism of these helical nanostructures provide additional insights into the interplay of the thermodynamics and kinetics of the assembly of structure-directing surfactants and inorganic silicate species 1,2,19,20 and may also lead to the design and synthesis of additional novel selfassembled nanomaterials with controllable mesostructures and morphologies, allowing for innovative applications. 9,11,21 The first synthesis of helical mesoporous silica materials displaying a MCM-41-like two-dimensional (2D)-hexagonal structure was performed in a static two-phase acidic system. 7 Helical 2D-hexagonal mesoporous silica nanofibers (HMSNFs) or nanorods were then synthesized in single-phase dilute solutions using chiral 5 or achiral 2,20,22 surfactants. The helical formation is mainly driven by a reduction in the free energy of the surface, from straight micellar rods until the free energy is balanced by an increased bending energy. 2,20 Alternatively, HMSNFs can be prepared by evaporation-induced selfassembly (EISA) in porous anodic alumina membranes. 23,24 The confined EISA may result in helical and other thermodynamically more stable mesophases, the former generally being kinetically favored. Notably, materials with mixed mesostructures can also be

Twisted and tubular silica structures by anionic surfactant fibers encapsulation

“…The assembly of metal nanoparticles onto silica structures can combine the benefits of both materials and provide new properties [34][35][36][37][38][39][40][41][42]. Bringing chirality to plasmonic nanomaterials is on demand for potential applications in nanotechnology and metamaterials [43][44][45][46][47].…”

One-Pot Synthesis of Pd Nanorings Using a Soft Template of Spindle-Shaped Amphiphilic Molecular Assembly

“…The methods used to fabricate metal nanorings are mainly divided into two approaches: (i) advanced nanotechnology − such as ion-beam lithography or electron-beam lithography; (ii) nanotemplating techniques ,− using rigid and hard nanomaterials such as inorganic nanoparticles (NPs) or nanoporous materials. The first approach is extremely favorable for preparing metal nanorings with the desired diameters and thicknesses; however, the productivity is low because of the inherently two-dimensional (2D) fabrication method.…”

“…The second approach has the potential for large-scale synthesis because it can be applied to dispersions of nanotemplates. However, many studies on nanotemplating use 2D substrates decorated with nanotemplates as the platform of nanoring production because fabrication methods such as electroplating, − chemical reduction, − and selective etching, − except for galvanic replacements, all require 2D substrates. The galvanic replacement technique − can be applied to inorganic NPs dispersed in a solution, but the applicable NPs are restricted to those with anisotropic structures such as plate-like NPs.…”

“…The galvanic replacement technique − can be applied to inorganic NPs dispersed in a solution, but the applicable NPs are restricted to those with anisotropic structures such as plate-like NPs. Furthermore, the thickness of nanorings fabricated by both advanced nanotechnology and nanotemplating remains above ∼10 nm. − …”

Stress‐Induced 3D Chiral Fractal Metasurface for Enhanced and Stabilized Broadband Near‐Field Optical Chirality

“…So far, fabrication of 3D plasmonic nanostructures and metasurfaces is still challenging and complex, setting up a major technical barrier to the applications. State‐of‐the‐art fabrication methods for 3D chiral nanostructures or metasurfaces include focused ion/electron beam deposition, multistep electron beam lithography, direct laser writing, glancing angle deposition, and chemical synthesis with the assistance of chiral templates or circularly polarized illumination . However, these methods are typically complex with multiple fabrication steps involved.…”