Search

The wide accessibility to nanostructures with high uniformity and controllable sizes and morphologies provides great opportunities for creating complex superstructures with unique functionalities. Employing anisotropic nanostructures as the building blocks significantly enriches the superstructural phases, while their orientational control for obtaining long-range orders has remained a significant challenge. One solution is to introduce magnetic components into the anisotropic nanostructures to enable precise control of their orientations and positions in the superstructures by manipulating magnetic interactions. Recognizing the importance of magnetic anisotropy in colloidal assembly, we provide here an overview of magnetic field-guided self-assembly of magnetic nanoparticles with typical anisotropic shapes, including rods, cubes, plates, and peanuts. The Review starts with discussing the magnetic energy of nanoparticles, appreciating the vital roles of magneto-crystalline and shape anisotropies in determining the easy magnetization direction of the anisotropic nanostructures. It then introduces superstructures assembled from various magnetic building blocks and summarizes their unique properties and intriguing applications. It concludes with a discussion of remaining challenges and an outlook of future research opportunities that the magnetic assembly strategy may offer for colloidal assembly.

When a diamagnetic graphite plate is placed on top of a magnet, it is subject to both magnetic levitation and gravitational forces. Computational modeling is used to demonstrate that these forces can balance each other to allow a stable tilt angle θ to be attained when the graphite plate pivots on the magnet surface. θ depends on the magnetic susceptibility χmag, which can be controlled by using laser irradiation to change the temperature of the graphite. Over a limited temperature range, there is a linear relation between the angle change Δθ and the temperature change ΔT. This predicted behavior is confirmed experimentally using a graphite plate (5 × 5 × 0.83 mm) placed on top of a 7.5 cm diameter neodymium iron boride magnet with a surface field strength of ∼5000 G. Using a 532 nm laser, θ could be continuously tuned from 52° to 26° by varying the laser power between 20 and 800 mW. The response time was about 15 s at all powers. Higher laser powers were observed to lead to a complete loss of levitation, followed by recovery and oscillation in and out of the laser beam. The linear dependence of Δθ on power suggests that photothermal tilting of the graphite plate in a magnetic field provides a fatigue resistant way to achieve large angular deviations using an external light source. This effect can be harnessed to function as a laser-controlled beam steering device. [ABSTRACT FROM AUTHOR]

Titania nanocrystals have been investigated for fast color switching through photocatalytic reduction of dyes and hexacyanometalate pigments. Here we reveal that direct binding of sacrificial electron donors (SEDs) to the surface of titania nanocrystals can significantly promote the charge transfer rate by more efficiently scavenging photogenerated holes and releasing more photogenerated electrons for reduction reactions. Using diethylene glycol (DEG) as an example, we show that its binding to the nanoparticle surface, which can be achieved either during or after the nanoparticle formation, greatly enhances the photocatalytic reduction in comparison with the case where free DEG molecules are simply added as external SEDs.

Magnetic fields are uniquely valuable for creating colloidal nanostructured materials, not only providing a means for controlled synthesis but also guiding their self‐assembly into distinct superstructures. In this study, a magnetothermal process for synthesizing hybrid nanostructures comprising ferrimagnetic magnetite nanorods coated with fluorescent perovskite nanocrystals is reported and their magnetic assembly into superstructures capable of emitting linear and circularly polarized light are demonstrated. Under UV excitation, the superstructures assembled in a liner magnetic field produce linear polarized luminescence, and those assembled in a chiral magnetic field exhibit strong circularly polarized luminescence (CPL) with a glum value up to 0.44 (±0.004). The CPL is believed to originate from the dipolar interaction between neighboring perovskite nanocrystals attached to the chiral assemblies and the chiral‐selective absorption of the perovskite emission by the magnetite phase. The magnetic synthesis and assembly approaches and the resulting distinctive chiral superstructures are anticipated to open up new avenues for designing diverse functional chiroptical devices. [ABSTRACT FROM AUTHOR]

Adipose tissue is the body largest free cholesterol reservoir and abundantly expresses ATP binding cassette transporter A1 (ABCA1), which maintains plasma high-density lipoprotein (HDL) levels. HDLs have a protective role in atherosclerosis by mediating reverse cholesterol transport (RCT). Soluble epoxide hydrolase (sEH) is a cytosolic enzyme whose inhibition has various beneficial effects on cardiovascular disease. The sEH is highly expressed in adipocytes, and it converts epoxyeicosatrienoic acids (EETs) into less bioactive dihydroxyeicosatrienoic acids. We previously showed that increasing EETs levels with a sEH inhibitor (sEHI) (t-AUCB) resulted in elevated ABCA1 expression and promoted ABCA1-mediated cholesterol efflux from 3T3-L1 adipocytes. The present study investigates the impacts of t-AUCB in mice deficient for the low density lipoprotein (LDL) receptor (Ldlr(-/-) mice) with established atherosclerotic plaques. The sEH inhibitor delivered in vivo for 4 weeks decreased the activity of sEH in adipose tissue, enhanced ABCA1 expression and cholesterol efflux from adipose depots, and consequently increased HDL levels. Furthermore, t-AUCB enhanced RCT to the plasma, liver, bile and feces. It also showed the reduction of plasma LDL-C levels. Consistently, t-AUCB-treated mice showed reductions in the size of atherosclerotic plaques. These studies establish that raising adipose ABCA1 expression, cholesterol efflux, and plasma HDL levels with t-AUCB treatment promotes RCT, decreasing LDL-C and atherosclerosis regression, suggesting that sEH inhibition may be a promising strategy to treat atherosclerotic vascular disease.

The small hydropower stations have reached a new balance after years of operation. The ecological balance of the river would been broken by the dam removal and the reservoir area above the dam would disappear. Consequently, a series of changes occurred in water depth, velocity of flow, the concentration of organic and inorganic nutrients, distribution and form of organic matter, aquatic organism, etc. It is unclear what would happen for the hydrodynamic conditions, sediment characteristics and aquatic organism community structure of the reservoir area and the lower reaches after the dam removal. Therefore, it is urgent to study the impact of dam removal on the transportation and redistribution of organic debris and the potential ecological effects with benthos as indicators in the river where the small hydropower station is located.