Preparation, Growth Mechanism, Upconversion, and Near-Infrared Photoluminescence Properties of Convex-Lens-like NaYF₄ Microcrystals Doped with Various Rare Earth Ions Excited at 808 nm

Preparation of rare earth ions doped photoluminescence materials with controlled morphology was desired to fulfill the requirement of different applications. In the work, convex-lens-like NaYF₄ microcrystals doped with various rare earth ions were prepared by adjusting preparation parameters including the reaction time, reaction temperature, NaOH concentration, ratio of oleic acid to 1-octadecene, and types of doping ions. A possible growth mechanism of convex-lens-like NaYF₄ microcrystals is proposed based on reaction time and temperature-dependent morphology evolution. The formation of micro-convex-lens includes the three processes of NaYF₄ nanoparticles self-assemble, dissolution–nucleation, and regrowth. Doping ions dependent near-infrared and upconversion luminescence properties of convex-lens-like NaYF₄ microcrystals were investigated excited at 808 nm. The visible upconversion luminescence was observed in the Er³⁺, Yb³⁺/Er³⁺, Nd³⁺/Er³⁺, Nd³⁺/Yb³⁺/Er³⁺ doped convex-lens-like NaYF₄ microcrystals, and near-infrared luminescence was obtained in the Nd³⁺, Nd³⁺/Er³⁺, Yb³⁺/Er³⁺, Nd³⁺/Yb³⁺, Nd³⁺/Yb³⁺/Er³⁺ doped NaYF₄ convex-lens-like NaYF₄ microcrystals. The Er³⁺, Yb³⁺/Er³⁺, Nd³⁺/Er³⁺, Nd³⁺/Yb³⁺/Er³⁺ doped convex-lens-like NaYF₄ microcrystals exhibit various upconversion luminescence mechanisms. The energy transfer of the Er³⁺ → Yb³⁺ and the Nd³⁺ → Er³⁺ was observed in the Yb³⁺/Er³⁺ and Nd³⁺/Er³⁺ doped convex-lens-like NaYF₄ microcrystals, respectively. The upconversion emission of Nd³⁺/Yb³⁺/Er³⁺ doped convex-lens-like NaYF₄ microcrystals is from the energy transfer mechanisms of Nd³⁺ → Yb³⁺ → Er³⁺

Evaluation of Graphene Oxide as a Thermal Ionization Enhancer for Plutonium in TIMS Measurement

Thermal ionization mass spectrometry (TIMS) has been extensively employed for the assessment of plutonium (Pu) isotopes in nuclear forensics and environmental monitoring. Recently, great efforts have been made to improve the ionization efficiency (IE) of Pu to achieve better accuracy and precision for trace-level analysis. Herein, the thermal ionization enhancement effect for plutonium of graphene oxide (GO) was investigated and the corresponding mechanism was discussed. The GO layers were homogeneously mounted on the filament’s central surface to promote pg-level Pu ion emission. With the excellent structural property of GO, a greatly promoted ionization efficiency of 0.44% for Pu was obtained, and the initial ionization temperature for Pu was remarkably reduced from 1610 to 1390 °C. Average boosts in IE compared to the classical double-filament mode and graphite-loaded single-filament mode were 1640 and 520%, respectively. The analytical accuracy and precision based on the GO-loaded single-filament mode were validated using Pu isotopic certified reference materials. This work demonstrates the excellent property of GO as an ion source additive for Pu ionization, as it provided an interface for the promotion of energy transfer and Pu carbide formation. The operation of GO loading is quite simple and can be finished within 5 min. This rapid filament carburization approach has great potential for improving the measurement precision of trace-level plutonium isotopes and can be applied in nuclear safeguards, nuclear forensics, and environmental monitoring

Sweet Theophylline Cocrystal with Two Tautomers of Acesulfame

A novel pharmaceutical cocrystal (THPAH12) of Theophylline (THP) was obtained with an artificial sweetener, Acesulfame (AH), in a molar ratio of 1:2. Solid state NMR spectra of the cocrystal indicate that the two AH molecules exist as keto and enol tautomers, which is further confirmed by the refined crystal structure. THPAH12 is the first keto form AH containing cocrystal. This highlights the fact that not only −OH of enol form of AH, but also the −NH–CO group of the keto form of AH should be considered when designing new pharmaceutical cocrystals via the supramolecular synthon approach. Compared with pure THP, THPAH12 possesses enhanced solubility and hydration stability, which highlight its potential for further pharmaceutical applications

Graphene Oxide Based Theranostic Platform for <i>T</i>₁‑Weighted Magnetic Resonance Imaging and Drug Delivery

Magnetic resonance imaging (MRI) is a powerful and widely used clinical technique in cancer diagnosis. MRI contrast agents (CAs) are often used to improve the quality of MRI-based diagnosis. In this work, we developed a positive <i>T</i>₁ MRI CA based on graphene oxide (GO)–gadolinium (Gd) complexes. In our strategy, diethylenetriaminepentaacetic acid (DTPA) is chemically conjugated to GO, followed by Gd­(III) complexation, to form a <i>T</i>₁ MRI CA (GO–DTPA–Gd). We have demonstrated that the GO–DTPA–Gd system significantly improves MRI <i>T</i>₁ relaxivity and leads to a better cellular MRI contrast effect than Magnevist, a commercially used CA. Next, an anticancer drug, doxorubicin (DOX), was loaded on the surface of GO sheets via physisorption. Thus-prepared GO–DTPA–Gd/DOX shows significant cytotoxicity to the cancer cells (HepG2). This work provides a novel strategy to build a GO-based theranostic nanoplatform with <i>T</i>₁-weighted MRI, fluorescence imaging, and drug delivery functionalities

Combined intrinsic and extrinsic proton conduction in robust covalent organic frameworks for hydrogen fuel cell applications

Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H3PO4, the COFs (H3PO4@COFs) realize an ultrahigh proton conductivity of 1.13×10−1 S cm−1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H3PO4@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm−2 and a maximum current density of 456 mA cm−2, which exceeds all previously reported COF materials

Aptamer-Modified Temperature-Sensitive Liposomal Contrast Agent for Magnetic Resonance Imaging

A novel aptamer modified thermosensitive liposome was designed as an efficient magnetic resonance imaging probe. In this paper, Gd-DTPA was encapsulated into an optimized thermosensitive liposome (TSL) formulation, followed by conjugation with AS1411 for specific targeting against tumor cells that overexpress nucleolin receptors. The resulting liposomes were extensively characterized <i>in vitro</i> as a contrast agent. As-prepared TSLs-AS1411 had a diameter about 136.1 nm. No obvious cytotoxicity was observed from MTT assay, which illustrated that the liposomes exhibited excellent biocompatibility. Compared to the control incubation at 37 °C, the liposomes modified with AS1411 exhibited much higher T₁ relaxivity in MCF-7 cells incubated at 42 °C. These data indicate that the Gd-encapsulated TSLs-AS1411 may be a promising tool in early cancer diagnosis