Current models for magnetoviscosity suggest that replacing the spherical nanoparticles of a conventional ferrofluid with magnetic nanotubes would lead to a stronger field-induced viscosity enhancement and a much-improved stability against shear thinning -two important parameters for technological exploitation of the magnetoviscous effect. We report the development of positive and negative templating strategies for the synthesis of magnetic nanotubes out of a variety of materials. Our positive template is Tobacco mosaic virus (TMV) -in natural form or genetically engineered to express specific surface chemistries and lengths -which we exploit as a template for the electroless deposition (ELD) of nanosized clusters of nickel and as a scaffold for magnetic particles in a conventional ferrofluid. Our negative templating strategy employs porous anodic aluminum oxide (AAO) as a substrate for the atomic layer deposition (ALD) of a conformal coating of iron oxide, offering precise control over the length and wall thickness of the resulting nanotubes. Both strategies were scaled up to produce the mass quantities of uniform-aspect-ratio nanotubes that are needed for macroscopic ferrofluid volumes. The magnetoviscosity of these ''nanotube ferrofluid'' samples was studied as a function of applied magnetic field and shear frequency, and a particularly strong effect was found to be induced by viral scaffolding.
A kind of terpyridine derivative (NH2-Tpy) in which the amino was incorporated by a short alkyl chain was synthesized. Through grafting of terpyridine units into the hydrophilic copolymers of maleic anhydride and acrylic acid PAAMa via the reaction of the amino groups in NH2-Tpy and the maleic anhydride units, a series of gelator polymers—P1, P2, and P3—containing different contents of terpyridine units was synthesized. Under coordination of Ni2+ and terpyridine ligands in linear polymers, the supramolecular hydrogels H1, H2, and H3 with different cross-linking degrees were prepared. The linear polymers P1–P3 had a strong absorption peak at about 290 nm in the UV-vis spectra which was attributed to π–π* transition, and there was a new peak at about 335 nm led by the metal-to-ligands charge transfer (MLCT) when coordinated with Ni2+ ions. According to the rheological behaviors, the storage modulus (G′) was larger than the loss modulus (G′′). These hydrogels showed typical gel-like characteristics when the terpyridine content of the hydrogels exceeded 10%, and the hydrogels showed liquid-like characteristics when the terpyridine content of the hydrogels was less than 7%. The results of the micromorphological investigation of the xerogels from SEM illustrated the metal–terpyridine coordination cross-linking could have an important influence on the microstructures of the resulting hydrogels. Furthermore, these hydrogels based on supramolecular cross-links exhibited reversible solution–gel transition at different environmental temperatures. At the same time, the equilibrium swelling of the supramolecular hydrogels was 8.0–12.3 g/g, which increased with the decrease in the content of the terpyridine units in the resulting hydrogels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.