Zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanostructured materials for advanced electrochemical energy devices

This feature article highlights the recent advances on the chemical synthesis, surface modification and applications of rare earth fluoride nano-/microcrysals. In the past decade, great progress in the size and shape control of rare earth fluoride nano-/microcrystals has been made by developing solution phase-based methods such as thermal decomposition, hydro(solvo)thermal reaction, hydrothermal in situ conversion route, and ionic liquids-based synthesis. The main challenge of fluoride nanocrystals for biological applications is that it is hard to obtain ideal nanocrystals with smaller size (sub-50 nm), higher luminescence yield, better dispersity and stability in aqueous solvents, and superior biocompatibility. In order to overcome these shortcomings, a series of strategies of surface modification have been outlined in this review. Finally, we introduce the application of rare earth fluorides, with special emphasis on β-NaY(Gd)F4 : Yb3+, Er3+ upconversion nanopaticles (UCNPs) in biomedical applications including biological labels, multimodal bioimaging, photodynamic therapy and drug delivery.

Rare earth fluoride nano-/microcrystals: synthesis, surface modification and application

Coating a homogeneous layer outside the core nanoparticles has become a common method to improve the optical properties of nanoparticles. For rare earth ion-doped nanoparticles, although the homogeneous coating is found to enhance the upconversion luminescence, a large deviation in the reported enhancement amplitude, however, demonstrates the lack of a complete picture of the enhancement mechanism. In this work, we have performed steady-state and time-resolved spectroscopic studies on one of the most efficient upconversion nanosystems − β-NaYF4:Yb3+,Er3+ and β-NaYF4:Yb3+,Er3+@β-NaYF4 core/shell nanoparticles. Roles of the surface quenching centers, typically the high-frequency vibrational modes provided by the organic surfactants in the upconversion luminescence, are studied in detail. Our results show that excitation power density, once over a threshold, say ∼150 W/cm2 in this case, does have a non-negligible annealing effect, which may even lead to high luminescence upconversion intensity of the core na...

Upconversion Luminescence of β-NaYF4: Yb3+, Er3+@β-NaYF4 Core/Shell Nanoparticles: Excitation Power Density and Surface Dependence

A simple and effective template-mediated protocol has been developed for the large-scale, room-temperature preparation of high-aspect-ratio, single-crystalline Tb-doped CePO(4) nanowires, measuring approximately 12 nm in diameter and over 10 mum in length. Moreover, we also isolated sheaf-like bundles of nanostructures. The synthesis mechanism likely involved a crystal splitting step. The resulting nanowires demonstrated an intense redox-sensitive green photoluminescence, which was exploited, in addition to their inherently high biocompatibility and low toxicity, for potential applications in biological imaging and labeling of cells.

Ambient Large-Scale Template-Mediated Synthesis of High-Aspect Ratio Single-Crystalline, Chemically Doped Rare-Earth Phosphate Nanowires for Bioimaging

A novel and facile soft-chemical method has been proposed for the synthesis of Ag3PO4 crystals with various new morphologies (branch, tetrapod, nanorod, triangular prism), and the morphological effect on the photocatalytic activity of the obtained Ag3PO4 crystals has been investigated. It is demonstrated that the morphology of Ag3PO4 crystals can be controlled by simply adjusting external experimental conditions such as static and ultrasonic conditions. Photocatalytic results indicate that the branched Ag3PO4 crystal with porous structure shows the highest photocatalytic activity among these Ag3PO4 crystals with multiform morphologies, and the photocatalytic rate constants of branched Ag3PO4 are 2.8 and 4 times those of irregular spherical Ag3PO4 for degradation of methylene blue (MB) and rhodamine B (RhB) dye solutions under visible light irradiation, respectively.

Shape-controllable synthesis and morphology- dependent photocatalytic properties of Ag3PO4 crystals†

A simple, efficient and quick method has been established for the synthesis of CePO4:Tb nanorods and CePO4:Tb/LaPO4 core/shell nanorods via ultrasound irradiation of inorganic salt aqueous solution under ambient conditions for 2?h. The as-prepared products were characterized by means of powder x-ray diffraction (PXRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and lifetimes. TEM micrographs show that all of the as-prepared cerium phosphate products have rod-like shape, and have a relatively high degree of crystallinity and uniformity. HRTEM micrographs and SAED results prove that these nanorods are single crystalline in nature. The emission intensity and lifetime of the CePO4:Tb/LaPO4 core/shell nanorods increased significantly with respect to those of CePO4:Tb core nanorods under the same conditions. A substantial reduction in reaction time as well as reaction temperature is observed compared with the hydrothermal process.

Facile sonochemical synthesis of CePO4:Tb/LaPO4 core/shell nanorods with highly improved photoluminescent properties

A single-crystalline EuF3 nanoflower with a novel three-dimensional (3D) nanostructure has been successfully synthesized via a facile, fast, efficient, and mild ultrasonic irradiation solution route employing the reaction of Eu(NO3)3 and KBF4 under ambient conditions without any template or surfactant. The ultrasonic irradiation plays an important role and is necessary for the synthesis of EuF3 with the complex structure. The formation mechanism of this complex nanostructure is proposed in this paper. No template or surfactant is used in this method, which avoids the subsequent complicated workup for the removal of the template or surfactant. Furthermore, a substantial reduction in the reaction time as well as the reaction temperature is observed compared with the hydrothermal process.

Xiaoming Liu

Papers

Facile sonochemical synthesis of CePO4:Tb/LaPO4 core/shell nanorods with highly improved photoluminescent properties

Facile Sonochemical Synthesis of Single-Crystalline Europium Fluorine with Novel Nanostructure