Xiao-Yu Zheng

Gd-Dots with Strong Ligand–Water Interaction for Ultrasensitive Magnetic Resonance Renography

Magnetic resonance imaging contrast agents with both significantly enhanced relaxivity and minimal safety risk are of great importance for sensitive clinical diagnosis, but have rarely been reported. Herein, we present a simple strategy to improve relaxivity by introducing surface ligands with strong interaction to water molecules. As a proof of concept, NaGdF4 nanoparticles (NPs) capped by poly(acrylic acid) (PAA) show superior relaxivity to those capped by polyethylenimine and polyethylene glycol, which is attributed to the strong hydrogen-bond capacity of PAA to water molecules as revealed by theoretical calculation. Furthermore, benefiting from PAA and ultrasmall particle size, Gd-dots, namely PAA-capped GdOF NPs (2.1 ± 0.2 nm), are developed as a high-performance contrast agent, with a remarkable ionic relaxivity of ∼75 mM-1 s-1 in albumin solution at 0.5 T. These Gd-dots also exhibit efficient renal clearance with <3% of injected amount left 12 h post-injection. Ultrasensitive MR renography achieved with Gd-dots strongly suggests their great potential for practical applications.

TbF3 nanoparticles as dual-mode contrast agents for ultrahigh field magnetic resonance imaging and X-ray computed tomography

Considering the development of magnetic resonance imaging (MRI) under ultrahigh magnetic field (>3 T), the exploration of novel contrast agents (CAs) for ultrahigh field MRI is urgently needed. Herein, we report polyethyleneimine (PEI)-coated TbF3 nanoparticles (NPs), which were synthesized by a facile solvothermal method, as potential dual-mode CAs for ultrahigh field MRI and X-ray computed tomography (CT). Owing to their strong paramagnetism, the TbF3 NPs showed excellent transverse relaxivity (395.77 mM–1·s–1) and negligible longitudinal relaxivity under an ultrahigh magnetic field (7 T) with a great potential as a T2-weighted MRI contrast agent. Furthermore, by comparison with the clinically used CT CAs (iohexol), the TbF3 NPs showed superior X-ray attenuation ability. The practical application for T2-weighted MRI and CT imaging was demonstrated with an animal model. Moreover, cell cytotoxicity and in vivo toxicity assessments implied the low toxicity of TbF3 NPs. In summary, the above results indicate that TbF3 NPs are promising candidates for ultrahigh field MRI and CT dual-mode imaging.

Heterogeneous synergistic catalysis by Ru-RuO x nanoparticles for Se–Se bond activation

The transition from homogeneous to heterogeneous synthetic chemistry enabled by nanocatalysts necessitates investigations of the reaction mechanism and structure-activity relationships for inorganic nanoparticles and organic substrates. Herein, we report that hydrothermally synthesized ruthenium nanoparticles performed differently in the Se–Se bond activation and selenylation of heterocycles, exhibiting a volcano-shaped relationship between catalytic activity and composition. A synergistic effect was observed for Ru-RuOx nanocatalysts, with numerous characterizations and density functional theory (DFT) calculations suggesting that a PhSeSePh molecule can initially be adsorbed on the metallic Ru sites and cleaved into two PhSe* species, which subsequently migrate to RuOx sites and react with the nucleophile to achieve the selenylation of heterocycles.

Phase segregation enabled scandium fluoride–lanthanide fluoride Janus nanoparticles

Janus particles, in which two distinct compositions are integrated, have attracted considerable interest for their potential multi-functionalities and synergistic effects. Although seed-mediated growth appears to be a suitable strategy that meets the stringent specifications for obtaining Janus particles, it is inapplicable to guide the growth of two crystalline components with different crystal structures. Herein, the formation of Janus particles via phase segregation is proposed. As proof-of-concept, promising photon conversion materials, ScF3 and lanthanide (Ln) fluorides, with great differences in structure, were chosen to build a series of Janus particles. Interestingly, using heavy (Lu, Yb, Dy and Tb) and light (Pr, Nd, Sm, Eu and Gd) lanthanides, ScF3–LiLnF4 and ScF3–LnF3 were formed, respectively. Time-dependent reaction studies indicate that phase segregation paves the way for the formation of these Janus nanoparticles (NPs), and this speculation is further confirmed by in situ transmission electron microscopy observations. These investigations provide new insights for the synthesis of heterostructured materials.

Rare Earth Based Anisotropic Nanomaterials: Synthesis, Assembly, and Applications

Rare earths (RE) refer to the lanthanide elements La–Lu together with Sc and Y. Conventionally, they have found applications in phosphors, magnets, catalysts, fuel cell electrodes/electrolyte. Here in this chapter, we discuss the synthesis, assembly and applications of rare earth based anisotropic nanomaterials. Regarding synthesis, the anisotropic growth behaviors of these nanocrystals are predominantly governed by their own unique crystal structures. Yet for wet-chemistry synthetic methods where a number of parameters could be finely tuned, the addition of particular coordination agents, templating agents or mineralizers has proven to be an effective way to direct the growth of nanocrystals into some anisotropic structures. Regarding applications, anisotropic nanomaterials, compared to their isotropic counterparts, often exhibit distinct properties. For example, the luminescence of anisotropic nanomaterials can display polarization and site-specific features. As for rare earth nanomaterials as magnetic resonance imaging (MRI) contrast agents, the high surface area of anisotropic nanostructures can give rise to superior performances. And for catalysis applications, anisotropic nanomaterials expose rich, highly active facets, which is of great importance for facet-selective catalytic reactions. In the chapter, we will start with introduction of the crystal structures of rare earth compounds, then briefly summarize the synthesis and assembly of rare earth anisotropic nanomaterials, and discuss their properties and applications in three realms, namely, luminescence, magnetism and catalysis.