Magnetically-responsive electrophoretic silica organosols

Aggregation-Augmented Magnetism of Lanthanide-Doped Nanoparticles and Enabling Magnetic Levitation-Based Exosome Sensing

Due to the presence of unpaired electron orbitals in most lanthanide ions, lanthanide-doped nanoparticles (LnNPs) exhibit paramagnetism. However, as to biosensing applications, the magnetism of LnNPs is so weak that can hardly be employed in target separation. Herein, it is discovered that the magnetism of the LnNPs is highly associated with their concentration in a confined space, enabling aggregation-augmented magnetism to make them susceptive to a conventional magnet. Accordingly, a magnetic levitation (Maglev) sensing system is designed, in which the target exosomes can specifically introduce paramagnetic LnNPs to the microbeads' surface, allowing aggregation-augmented magnetism and further leverage the microbeads' levitation height in the Maglev device to indicate the target exosomes' content. It is demonstrated that this Maglev system can precisely distinguish healthy people's blood samples from those of breast cancer patients. This is the first work to report that LnNPs hold great promise in magnetic separation-based biological sample sorting, and the LnNP-permitted Maglev sensing system is proven to be promising for establishing a new generation of biosensing devices.

Magnetic surfactants: A review of recent progress in synthesis and applications

Magnetic surfactants are a special class of surfactants with magneto-responsive properties. These surfactants possess lower critical micelle concentrations and are more effective in reducing surface tension as compared to conventional surfactants. Such surfactants' ability to manipulate self-assembly in a controlled way by tuning the magnetic field makes them an attractive choice for several applications, including drug delivery, catalysis, separation, oilfield, and water treatment. In this work, we reviewed the properties of magnetic surfactants and possible explanations of magnetic behavior. This article also covers the synthesis methods that can be used to synthesize different types of cationic, anionic, nonionic, and zwitterionic magnetic surfactants. The applications of magnetic surfactants in different fields such as biotechnology, water treatment, catalysis, and oilfield have been discussed in detail.

Noncovalent magnetic control and reversible recovery of graphene oxide using iron oxide and magnetic surfactants

The unique charging properties of graphene oxide (GO) are exploited in the preparation of a range of noncovalent magnetic GO materials, using microparticles, nanoparticles, and magnetic surfactants. Adsorption and desorption are controlled by modification of pH within a narrow window of <2 pH units. The benefit conferred by using charge-based adsorption is that the process is reversible, and the GO can be captured and separated from the magnetic nanomaterial, such that both components can be recycled. Iron oxide (Fe2O3) microparticles form a loosely flocculated gel network with GO, which is demonstrated to undergo magnetic compressional dewatering in the presence of an external magnetic field. For composites formed from GO and Fe2O3 nanoparticles, it is found that low Fe2O3:GO mass ratios (<5:1) favor flocculation of GO, whereas higher ratios (>5:1) cause overcharging of the surfaces resulting in restabilization. The effectiveness of the GO adsorption and magnetic capture process is demonstrated by separating traditionally difficult-to-recover gold nanoparticles (d ≈ 10 nm) from water. The fully recyclable nature of the assembly and capture process, combined with the vast adsorption capacity of GO, presents obvious and appealing advantages for applications in decontamination and water treatment.