High Strength Conductive Composites with Plasmonic Nanoparticles Aligned on Aramid Nanofibers

Abstract

Rapidly evolving fields of biomedical, energy, and (opto)electronic devices bring forward the need for deformable conductors with constantly rising benchmarks for mechanical properties and electronic conductivity. The search for conductors with improved strength and strain have inspired the multiple studies of nanocomposites and amorphous metals. However, finding conductors that defy the boundaries of classical materials and exhibit simultaneously high strength, toughness, and fast charge transport while enabling their scalable production, remains a difficult materials engineering challenge. Here, composites made from aramid nanofibers (ANFs) and gold nanoparticles (Au NPs) that offer a new toolset for engineering high strength flexible conductors are described. ANFs are derived from Kevlar macrofibers and retain their strong mechanical properties and temperature resilience. Au NPs are infiltrated into a porous, free-standing aramid matrix, becoming aligned on ANFs, which reduces the charge percolation threshold and facilitates charge transport. Further thermal annealing at 300 °C results in the Au-ANF composites with an electrical conductivity of 1.25 × 10 4 S cm −1 combined with a tensile strength of 96 MPa, a Young's modulus of 5.29 GPa, and a toughness of 1.3 MJ m −3 . These para meters exceed those of most of the composite materials, and are comparable to those of amorphous metals but have no volume limitations. The plasmonic optical frequencies characteristic for constituent NPs are present in the composites with ANFs enabling plasmon-based optoelectronic applications.

Water‐Rich Biomimetic Composites with Abiotic Self‐Organizing Nanofiber Network

“…Preparation of ANF–PVA Hydrogels : A 2 wt% ANF dispersion in DMSO was prepared using methods described elsewhere, and mixed with an equal volume of a 10 wt% PVA (Sigma–Aldrich, M w 146 000–186 000 a.u., 99%+ hydrolyzed) solution in DMSO. The mixing ratio was optimized for both the stiffness and strength of the resulting hydrogels (Figure S16, Supporting Information).…”

“…Solution‐processable nanoscale versions of Kevlar, i.e., aramid nanofibers (ANFs), retain the high mechanical properties of their macroscale parent, and these materials have served as the building blocks for high‐strength flexible conductors and battery separators . In the context of this study, a key fact is that ANFs with diameters of 5–30 nm and lengths of 3–10 µm form networked structures when DMSO is exchanged with water . Their structural similarity to biological nanofibers, such as those from collagen and those that display extensive branching, inspired us to explore ANFs as the stiff components of biomimetic composites .…”

“…We recently reported that para‐aramid, commonly known as Kevlar, can form a nanofibrous dispersion in dimethyl sulfoxide (DMSO) . Solution‐processable nanoscale versions of Kevlar, i.e., aramid nanofibers (ANFs), retain the high mechanical properties of their macroscale parent, and these materials have served as the building blocks for high‐strength flexible conductors and battery separators . In the context of this study, a key fact is that ANFs with diameters of 5–30 nm and lengths of 3–10 µm form networked structures when DMSO is exchanged with water .…”

New Self‐Organization Route to Tunable Narrowband Optical Filters and Polarizers Demonstrated with ZnO–ZnWO4 Eutectic Composite

“…Other bottom‐up methods which were utilized to manufacture novel optical materials include: colloidal chemistry, self‐assembled nanoparticle clusters, use of liquid crystals, laser‐induced self‐organization, use of anodized alumina templates, block copolymers, silicon‐based dielectric metamaterials, nanoparticles aligned in porous matrices, or a bottom‐up nanolithography …”

Green Formation of Robust Supraparticles for Cargo Protection and Hazards Control in Natural Environments

“…Ecofriendly and porous BSiO 2 particles, isolated from silicon‐accumulating plants through green platforms, are in contrast to synthetic porous silica particles obtained from bottom‐up processes that generate highly hazardous by‐products and toxic intermediate reactants such as ferrosilicon (FeSi) and silicon tetrachloride (SiCl 4 ) . CNFs, derived from mechanical disintegration of cellulosic fibers, represent an emerging alternative for the self‐assembly of 3D fibrillar networks, akin to those obtained by chemically treated aramid (Kevlar) nanofibers . The high specific surface area of BSiO 2 particles (≈350 m² g −1 ) together with the unique properties of CNFs (i.e., biodegradability, high aspect ratio, and high strength and stiffness) makes them an outstanding combination to prepare highly porous and strong superstructures, addressing toxicological and environmental considerations.…”