This article describes the three-dimensional self-assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers. For layers in which the NPs are more free to rotate, the easy axis of the NP can readily orient along the field direction. In more dense packing, free rotation of the NPs is hampered, and the NP ensembles likely build up quasi-domain states to minimize energy, which leads to lower magnetization in those layers. Detailed analysis of polarized neutron reflectometry data together with model calculations of the arrangement of the NPs within the layers and input from small-angle scattering measurements provide full characterization of the core/shell NP dimensions, degree of chaining, arrangement of the NPs within the different layers, and magnetization depth profile.
Anhui Provincial Engineering Center for High Performance Biobased Nylons, Anhui Provincial Engineering Center for Automotive Highly Functional Fiber Products, School of Materials and Chemistry, Anhui Agricultural University, Hefei 230036, China.
Communication technologies expose us to electromagnetic fields (EMF), which may pose health risks, especially for vulnerable groups like pregnant women.
We developed a triboelectric ferrofluid fiber (TFF) that can detect EMF and generates its own charge, making it flexible and suitable for integration into fabrics.
This smart fabric can provide environmental warnings and real-time health monitoring, specifically designed for the safety and healthcare needs of at-risk populations.
A new ferrofluid extractant (FeO @SiO-WDES) was ingeniously prepared by coating magnetic FeO @SiO microspheres with water-based deep eutectic solvent (WDES) and used for dispersive liquid-liquid microextraction (DLLME) and HPLC determination of naphthalene-derived plant growth regulators (PGRs, i.e., 1-naphthylacetic acid, 2-naphthylacetic acid, 1-naphthoxy acetic acid, 2-naphthyloxyacetic acid and 1-naphthylacetamide) in edible oil.
Ferrofluids or magnetic nanofluids are highly stable colloidal suspensions of magnetic nanoparticles (NPs) dispersed into various base fluids. These stable ferrofluids possess high thermal conductivity, improved thermo-physical properties, higher colloidal stability, good magnetic properties, and biocompatibility, which are the primary driving forces behind their excellent performance, and thus enable them to be used for a wide range of practical applications. The most studied and advanced ferrofluids are based on iron oxide nanostructures especially NPs, because of their easy and large-scale synthesis at low costs.
We study the assembly of magnetite nanoparticles in water-based ferrofluids in wetting layers close to silicon substrates with different functionalization without and with an out-of-plane magnetic field. For particles of nominal sizes 5, 15, and 25 nm, we extract density profiles from neutron reflectivity measurements. We show that self-assembly is only promoted by a magnetic field if a seed layer is formed at the silicon substrate.
Herein, we report the investigation of the electrical and thermal conductivity of FeO and FeO@carbon (FeO@C) core-shell nanoparticle (NP)-based ferrofluids. Different sized FeO NPs were synthesized a chemical co-precipitation method followed by carbon coating as a shell over the FeO NPs the hydrothermal technique. The average particle size of FeO NPs and FeO@C core-shell NPs was found to be in the range of ∼5-25 nm and ∼7-28 nm, respectively.
