Free‐Standing All‐Nanoparticle Thin Fibers: A Novel Nanostructure Bridging Zero‐ and One‐Dimensional Nanoscale Features

Abstract

Nanoscience and nanotechnology have had great success in revealing nanostructures with unique dimensionalities. To highlight a few, nacre is composed of nanolayers of inorganic crystallites and biopolymers [1] and is therefore 2D in nature and exhibits extraordinary toughness. [2,3] Derivatives of such a structure can be utilized to suit a variety of engineering applications due to their fine structure. Nanotubes, nanobelts, or nanofibers all possess a 1D structure, where the long dimension promotes applications for advanced functional materials and the short dimension delivers superior electronic, mechanical, or electromechanical properties. Long-lasting impacts of these 1D features are being generated in multiple fields. For example, nanotubes could be used as scanning probes to provide unprecedented resolution to scanning probe microscopy, [4,5] continuous nanofibers can be efficient intermediate layers in nanocomposites, [6,7] and functional nanobelts demonstrating an electromechanical coupling effect can be potential candidates to power future nanosystems. [8][9][10] While nanoparticles or nanodots qualify as 0D structures and also have peculiar electronic or optoelectronic properties, their role as building blocks for higher-order subjects is one of their most prominent features. Demonstrated examples include packed particle films for high sensitivity detection, [11] fabricated arrays for photonic crystals, [12][13][14] and layered pores for energy storage. [15,16] More interestingly, it is even possible to form laminates of nanolayers with a carefully designed manufacturing and surface chemistry approach, rendering the formation of artificial nacre. [17,18] Properties of resulting assemblies usually exceed that of individual nanoparticles, where a large surface-to-volume ratio is believed to be one of the reasons for such a collective effect.With so much evidence for the structural flexibility of nanoparticles, stumbling blocks still impede the control of the growth of these 0D elements into a 1D assembly. Major barriers to unidirectional growth are difficulties to attenuate the robust interactions between nanoparticles and their isotropic shape. Patterned templates or surfaces could guide the growth of these building blocks. [19][20][21][22][23][24][25][26][27] An anisotropic surface treatment atop nanoparticles could regulate their assembly to a certain degree. [28,29] Free-standing strings of nanoparticles are rarely observed. A good strategy to devise a high throughput manufacturing of these assemblies with decent uniformity and a large aspect ratio has not been reported.We present our strategy in this communication to make unidirectionally grown and template-free, i.e., free-standing, 1D nanostructures by using uniform nanoparticles. We call this newly discovered structure a particle-fiber, implying the 0D nature of the building blocks. These string-like structures are grouped into forests after fabrication and have a few unique features, such as a high aspect ratio (length vs. diameter ! 2500), a uni...

Controlled freezing and freeze drying: a versatile route for porous and micro-/nano-structured materials

“…Upon heating above the glass transition temperature, the PS colloids fused to form smooth microwires. Freeze-standing nanoparticlesassembled fibres were also formed by directional freezing of aqueous PS nanoparticle (80 nm) suspensions by Yan et al 102 Chemical vapour deposition (CVD) was further employed to afford ductility to these brittle fibres. Stucky and co-workers fabricated fibres with an ordered brick-and-mortar arrangement of inorganic phase and organic phase composed of silica (and other inorganic nanoparticles)@poly(N-isopropylacrylamide) (PNIPAM) in a directional freezing approach.…”

Preparation of aligned porous gelatin scaffolds by unidirectional freeze-drying method

“…The size of the tubular pores, the surface area and the pore wall thickness can be adjusted by varying the molecular weight and solution concentration of PVA, as well as the freezing speed. In addition, this method was also used to prepare unidirectional porous carbon nanotube or poly (L-lactic acid) scaffolds [29,30], as well as free-standing all-nanoparticle thin fibers [31,32]. The biocompatibility of the scaffold was improved by modification of the scaffold with natural polymers and natural particles such as HAP [33].…”

In situ synthesis of SiC nanowire porous layer on carbon/carbon composites

“…Reaction (7) was followed by reaction (5) to synthesize CO, which in turn reacted with SiO 2 and SiO according to reaction (4) and (7), and then the cycle continued. SiC can be prepared by heterogeneous nucleation according to the reaction (6) with gas-solid interaction, but the growth of SiCNWs was believed to undergo a gas-phase according to reaction (7) with gas-gas interaction.…”

“…[1][2][3] They have potential for using in composite materials as reinforcements because of their strength higher than their bulk counterparts. [4][5][6] 1D SiC nanowires (SiCNWs) have been suggested as effective reinforcement materials using for ceramic-matrix composites [7][8][9][10] and ultrahigh temperature ceramic oxidation resistant coatings, 2,11 which exhibits enhanced toughening effect. Tan et al 12 synthesized in situ SiCNWs in 2.5D needle punched carbon fiber fabric via precursor infiltration pyrolysis, and the flexural strength and interlaminar shear strength of the SiC nanowire-reinforced carbon/carbon (C/ C) composites were increased by 131% and 68% compared to C/C composites without SiCNWs, respectively.…”