One-Pot Synthesis of Magnetoplasmonic Au@FexOy Nanowires: Bioinspired Bouligand Chiral Stack

One-dimensional hybrid nanostructures composed of a plasmonic gold nanowire core covered by a shell of magnetic oxide nanoparticles (Au@Fe_xO_y NWs) were synthesized by a one-pot solvothermal synthesis process. The effects of reaction temperature, time, reducing agent, and precursor as well as postsynthesis treatment were optimized to produce highly uniform NWs with a diameter of 226 ± 25 nm and a plasmonic core aspect ratio of 25 to 82. By exploiting the interaction of NWs with an external magnetic field, precise arrangements into highly periodic photonic structures were achieved, which can generate distinctive structural colors that are vividly iridescent and polarization-sensitive. Furthermore, a Bouligand-type chiral nematic film consisting of multistacked unidirectional layers of achiral NWs was fabricated using a modified layer-by-layer deposition method, which displays circular dichroism (CD) and chiral sensing capability. The addition of bovine serum albumin (BSA) as a model protein analyte induced a concentration-dependent wavelength shift of CD peaks. These intriguing properties of magnetoplasmonic anisotropic NWs and their self-assemblies could be consequently valuable for developing nature-inspired structural color imprints as well as solid-state chiral sensing devices.

3D Flower-Like FeWO4/CeO2 Hierarchical Architectures on rGO for Durable and High-Performance Microalgae Biophotovoltaic Fuel Cells

A facile chemical reduction approach is adopted for the synthesis of iron tungstate (FeWO₄)/ceria (CeO₂)-decorated reduced graphene oxide (rGO) nanocomposite. Surface morphological studies of rGO/FeWO₄/CeO₂ composite reveal the formation of hierarchical FeWO₄ flower-like microstructures on rGO sheets, in which the CeO₂ nanoparticles are decorated over the FeWO₄ microstructures. The distinct anodic peaks observed for the cyclic voltammograms of studied electrodes under light/dark regimes validate the electroactive proteins present in the microalgae. With the cumulative endeavors of three-dimensional FeWO₄ microstructures, phase effect between rGO sheet and FeWO₄/CeO₂, highly exposed surface area, and light harvesting property of CeO₂ nanoparticles, the relevant rGO/FeWO₄/CeO₂ nanocomposite demonstrates high power and stable biophotovoltaic energy generation compared with those of previous reports. Thus, these findings construct a distinct horizon to tailor a ternary nanocomposite with high electrochemical activity for the construction of cost-efficient and environmentally benign fuel cells.

Water-guided synthesis of well-defined inorganic micro-/nanostructures

Water is one of the most commonplace solvents employed in wet chemical synthesis; however, it can sometimes play important roles such as an effective inducer or morphology-directing agent when introduced into a special reaction system, resulting in the formation of inorganic micro-/nanostructures with well-defined configurations. A better understanding of the key roles of water in the chemical synthesis will unlock a door to the design of many more novel single-component and hybrid nanocomposite architectures. Therefore, it is imperative to comprehensively review the topic of water-guided synthesis of well-defined micro-/nanostructures. Unfortunately, the significance of water has been underestimated and an in-depth study about the exact action of water in morphology-control is still lacking. In this review, we focus on the recent advances made in the development of the shape-controlled synthesis of inorganic micro-/nanostructures achieved by only adjusting the amount of water through some typical examples, including noble metals, metal oxides, perovskites, metal sulfides and oxysalts. In particular, the theory principles, synthesis strategies and growth mechanisms of the water-guided synthesis of well-defined inorganic micro-/nanostructures have been mainly highlighted. Finally, several current issues and challenges of this topic that need to be addressed in future investigations are briefly presented.

Synthesis engineering of iron oxide raspberry-shaped nanostructures

Magnetic porous nanostructures consisting of oriented aggregates of iron oxide nanocrystals display very interesting properties such as a lower oxidation state of magnetite, and enhanced saturation magnetization in comparison with individual nanoparticles of similar sizes and porosity. However, the formation mechanism of these promising nanostructures is not well understood, which hampers the fine tuning of their magnetic properties, for instance by doping them with other elements. Therefore the formation mechanism of porous raspberry shaped nanostructures (RSNs) synthesized by a one-pot polyol solvothermal method has been investigated in detail from the early stages by using a wide panel of characterization techniques, and especially by performing original in situ HR-TEM studies in temperature. A time-resolved study showed the intermediate formation of an amorphous iron alkoxide phase with a plate-like lamellar structure (PLS). Then, the fine investigation of PLS transformation upon heating up to 500 °C confirmed that the synthesis of RSNs involves two iron precursors: the starting one (hydrated iron chlorides) and the in situ formed iron alkoxide precursor which decomposes with time and heating and contributes to the growth step of nanostructures. Such an understanding of the formation mechanism of RSNs is necessary to envision efficient and rational enhancement of their magnetic properties.

Comparison of the effects of microcrystalline cellulose and cellulose nanocrystals on Fe3O4/C nanocomposites

Fe₃O₄/C nanocomposites with relatively high superparamagnetic and ferromagnetic performances were obtained by an ultrasound method combining calcination, which provided promising applications for the dye removal and wastewater treatment fields.

Ionic-liquid-micelle-functionalized mesoporous Fe3O4 microspheres for ultraperformance liquid chromatography determination of anthraquinones in dietary supplements

A magnetic solid-phase extraction method using ionic liquid (IL)-micelle-functionalized mesoporous Fe3O4 microspheres (MFMs) was proposed for the preconcentration of anthraquinones in dietary supplements. The analytes were then determined by ultraperformance liquid chromatography combined with an ultraviolet detector. The extraction parameters, such as the choice of ILs, the concentrations of ILs and MFMs, the pH of diluent, and the concentration of acetic acid in the eluent, were presented. Under the optimized conditions, the limits of detection and limits of quantitation were 0.4-2.8 ng mL(-1) and 1.4-9.4 ng mL(-1), respectively. The accuracy of the proposed method was investigated by recovery in herb and granules of Radix et Rhizoma Rhei, yielding values between 89.25% and 96.48%. The use of the proposed method in the sample pretreatment of complex dietary supplements is feasible due to the high surface area and excellent adsorption capacity of MFMs after modification with IL.

Green synthesis of Fe3O4 nanoparticles with controlled morphologies using urease and their application in dye adsorption

This paper describes a green method which employs urease for the preparation of Fe₃O₄ nanoparticles, and explores their application in dye adsorption.

One-step fabrication of functionalized magnetic adsorbents with large surface area and their adsorption for dye and heavy metal ions

Functionalized magnetic adsorbents were synthesized by a facile and surfactant-free one-pot solvothermal approach, using iron(iii) chloride hexahydrate as precursor, ethylene glycol as reducing agent, ammonium acetate, and EDTA-2Na as electrostatic stabilization agent.