Deep Eutectic Solvents-based Ionogels with Ultrafast Gelation and High Adhesion in Harsh Environments.

Adhesive materials have recently drawn intensive attention due to their excellent sealing ability, thereby stimulating advances in materials science and industrial usage. However, reported adhesives usually exhibit weak adhesion strength, require high pressure for strong bonding, and display severe adhesion deterioration in various harsh environments. In this work, instead of water or organic solvents, a deep eutectic solution (DES) was used as the medium for photopolymerization of zwitterionic and polarized monomers, thus generating a novel ionogel with tunable mechanical properties. Multiple hydrogen bonds and electrostatic interactions between DES and monomers facilitated ultrafast gelation and instant bonding without any external pressure, which was rarely reported previously. Furthermore, high adhesion in different harsh environments (e.g., water, acidic and basic buffers, and saline solutions) and onto hydrophilic (e.g., glass and tissues) and hydrophobic (e.g., polymethyl methacrylate, polystyrene, and polypropylene) adherends was demonstrated. Also, high stretchability of the ionogel at extreme temperatures (-80 and 80 °C) indicated its widespread applications. Furthermore, the biocompatible ionogel showed high burst pressure onto stomach and intestine tissues to prevent liquid leakage, highlighting its potential as an adhesive patch. This ionogel provides unprecedented opportunities in the fields of packaging industry, marine engineering, medical adhesives, and electronic assembly.

Fabrication and Characterization of Solid Composite Yarns from Carbon Nanotubes and Poly(dicyclopentadiene).

In this report, networks of carbon nanotubes (CNTs) are transformed into composite yarns by infusion, mechanical consolidation and polymerization of dicyclopentadiene (DCPD). The microstructures of the CNT yarn and its composite are characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and a focused ion beam used for cross-sectioning. Pristine yarns have tensile strength, modulus and elongation at failure of 0.8 GPa, 14 GPa and 14.0%, respectively. In the composite yarn, these values are significantly enhanced to 1.2 GPa, 68 GPa and 3.4%, respectively. Owing to the consolidation and alignment improvement, its electrical conductivity was increased from 1.0 × 105 S/m (raw yarn) to 5.0 × 105 S/m and 5.3 × 105 S/m for twisted yarn and composite yarn, respectively. The strengthening mechanism is attributed to the binding of the DCPD polymer, which acts as a capstan and increases frictional forces within the nanotube bundles, making it more difficult to pull them apart.

Ultrasonication-assisted synthesis of high aspect ratio gold nanowires on a graphene template and investigation of their growth mechanism.

We report a facile synthesis of Au nanowires (AuNWs) with a high aspect ratio (l/D) of up to 5000 on a plasma activated graphene template with ultrasound assistance. We demonstrate that the ultrasonication induced symmetry breaking of Au clusters facilitates the growth of AuNWs from the embryonic stages. Furthermore, the growth mechanism of AuNWs is systematically investigated using high resolution electron transmission microscopy (HRTEM), which reveals the unique role of the defective graphene template in directing the growth of AuNWs.

One-Step Synthesis of Tunable-Size Gold Nanoplates on Graphene Multilayers.

Au nanoplates (quasi-two-dimensional single crystals) are most commonly synthesized using a mixture of Au precursors via approaches involving multiple processing steps and the use of seed crystals. Here, we report the synthesis of truncated-hexagonal {111}-oriented micrometer-scale Au nanoplates on graphene multilayers using only potassium tetrabromoaurate (KAuBr4) as the precursor. We demonstrate that the nanoplate sizes can be controllably varied from tens of nanometers up to a few micrometers by introducing desired concentrations of chloroauric acid (HAuCl4) to KAuBr4 and their thicknesses from ∼13 to ∼46 nm with the synthesis time. Through a series of experiments carried out as a function of synthesis time and precursor composition [mixtures of HAuCl4 and KAuBr4, KBr, or ionic liquid 1-butyl-3-methylimidazolium bromide ([Bmim]Br)], we identify the optimal HAuCl4 and KAuBr4 concentrations and synthesis times that yield the largest and the thinnest size nanoplates. We show that the nanoplates are kinetically limited morphologies resulting from preferential growth of {111} facets facilitated by bromide ions in KAuBr4 solutions; we suggest that the presence of chloride ions enhances the rate of Au deposition and the relative concentration of chloride and bromide ions determines the shape anisotropy of resulting crystals. Our results provide new insights into the kinetics of nanoplate formation and show that a single precursor containing both Au and Br is sufficient to crystallize nanoplates on graphitic layers, which serve as reducing agent while enabling the nucleation and growth of Au nanoplates. We suggest that a similar approach may be used for the synthesis of nanoplates of other metals on weakly interacting van der Waals layers for, potentially, a variety of new applications.

Graphene template-induced growth of single-crystalline gold nanobelts with high structural tunability.

Assembling Au nanocrystals with tunable dimensions and shapes on graphene templates has attracted increasing attention recently. However, directly growing anisotropic Au nanobelts on a graphene support has been rarely reported. Here, a facile, one-pot, and surfactant-free route is demonstrated to synthesize well-defined Au nanobelts with the induction of a multilayer graphene (mlG) template. The obtained Au nanobelts are single-crystalline with a preferable (111) orientation. More importantly, their structural evolution starting from Au clusters is systematically investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that mlG consistently induces the growth of Au nanobelts from nucleation to the growth completion. The interfacial interaction between Au atoms and the graphene lattice is a predominant factor to direct the shapes and structures of Au nanocrystals, which makes the structures of Au nanobelts highly tunable with the surface modification of the mlG template. The assembly of mlG-Au nanobelts also presents extraordinary detection sensitivity when employed as a flexible surface-enhanced Raman scattering (SERS) substrate, suggesting their great potential application in high-performance sensors. This report strengthens the fundamental understanding of the interactions between noble metals and carbon interfaces, which paves the way to construct and manipulate the complex structures of metals on graphitic substrates.

Novel Strategy for One-Pot Synthesis of Gold Nanoplates on Carbon Nanotube Sheet As an Effective Flexible SERS Substrate.

In this work, we demonstrate a novel route for one-pot synthesis of two-dimensional gold nanoplates (2-D AuNPLs) on carbon nanotube (CNT) sheet. Well-defined AuNPLs are grafted onto CNT sheet via a facile hydrothermal reduction process, during which bromine ions are employed as the surfactant for gold anisotropic growth. Scanning electron microscopy (SEM) shows large-scale AuNPLs with micrometer-scaled length and sub-100 nm thickness are deposited uniformly on the CNT sheet. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results confirm the synthesized AuNPLs are single-crystalline with preferential {111} orientation. Based on the CNT sheet/AuNPLs hybrid, we have fabricated a flexible surface-enhanced Raman scattering (SERS) substrate, which can effectively detect the analyte Rhodamine 6G (Rh6G) at the concentration as low as 1 × 10-7 M. The excellent SERS performance of this novel flexible substrate is mainly attributed to nanoscaled gaps between the neighbors, large surface area with roughness, and their sharp edges and corners.