Multifunctional Hybrid Nanomaterials from Water Dispersible CaF₂:Eu³⁺, Mn²⁺ and Fe₃O₄ for Luminescence and Hyperthermia Application

CaF₂ nanoparticles doped with 1 at. % Eu³⁺and codoped with Mn²⁺ ions (1, 2, and 3 at. %) were synthesized at 180 °C by using ethylene glycol as a capping agent and solvent medium. The emission spectra of these nanomaterials show two main peaks at 590 and 612 nm after excitation at 240 or 394 nm. Enhancement in luminescence is found upon codoping of Mn²⁺. Parts of Eu³⁺ ions are substituted into Ca²⁺ sites (having a symmetry environment), which is reflected in the higher probability of magnetic dipole transition over that of electric dipole transition. The polymer film of polyvinyl alcohol incorporated with CaF₂:1Eu shows the red emission. The prepared nanomaterials are highly water dispersible. The hybrid of CaF₂:1Eu and Fe₃O₄ shows the heating ability up to 42 °C under an AC magnetic field. This is suitable for cancer therapy through hyperthermia. A very high specific absorption rate (SAR) of 283 W/g is observed. This can be ascribed to the increased magnetocrystalline anisotropy and Brownian relaxation. Biocompatibility of hybrid nanoparticles up to 75% in HeLa cells is observed. Also, this hybrid shows the red emission, and thus, it will be useful in tracing of magnetic nanoparticles through in vivo and in vitro optical imaging applications. Interestingly, the new exciton band at 300 nm is found in such a hybrid material

Sequential Evolution of Different Phases in Metastable Gd_2–<i>x</i>Ce_<i>x</i>Zr_2–<i>x</i>Al_<i>x</i>O₇ (0.0 ≤ <i>x</i> ≤ 2.0) System: Crucial Role of Reaction Conditions

The Gd_2–<i>x</i>Ce_<i>x</i>Zr_2–<i>x</i>Al_<i>x</i>O₇ (0.0 ≤ <i>x</i> ≤ 2.0) series was synthesized by the gel combustion method. This system exhibited the presence of a fluorite-type phase, along with a narrow biphasic region, depending upon the Ce/Gd content in the sample. Thermal stability of these new compounds under oxidizing and reducing conditions has been investigated. The products obtained on decomposition of Gd_2–<i>x</i>Ce_<i>x</i>Zr_2–<i>x</i>Al_<i>x</i>O₇ in oxidizing and reducing conditions were found to be entirely different. It was observed that in air the fluorite-type solid solutions of Gd_2–<i>x</i>Ce_<i>x</i>Zr_2–<i>x</i>Al_<i>x</i>O₇ composition undergo phase separation into perovskite GdAlO₃ and fluorite-type solid solutions of Gd–Ce–Zr–O or Ce–Zr–Al–O depending upon the extent of Ce and Al substitution. On the other hand, Gd_2–<i>x</i>Ce_<i>x</i>Zr_2–<i>x</i>Al_<i>x</i>O₇ samples on heating under reducing conditions show a phase separation to CeAlO₃ perovskite and a defect-fluorite of Gd₂Zr₂O₇. The extent of metastability for a typical composition of Gd_1.2Ce_0.8Zr_1.2Al_0.8O₇ (nano), Gd_1.2Ce_0.8Zr_1.2Al_0.8O_6.6 (heated under reduced conditions), Gd_1.2Ce_0.8Zr_1.2Al_0.8O₇ (heated in air at 1200 °C) has been experimentally determined employing a high temperature Calvet calorimeter. On the basis of thermodynamic stability data, it could be inferred that the formation of a more stable compound in the presence of two competing cations (i.e., Gd³⁺ and Ce³⁺) is guided by the crystallographic stability

Preparation and Structure of Uranium-Incorporated Gd₂Zr₂O₇ Compounds and Their Thermodynamic Stabilities under Oxidizing and Reducing Conditions

Gd₂Zr₂O₇ is being contemplated as a futuristic matrix for the incorporation of high-level radioactive nuclear waste. This compound has the unique ability to incorporate several fission products and heavy metal ions like uranium and thorium into its lattice sites without undergoing structural changes. X-ray diffraction analyses of Gd_2–<i>x</i>U_<i>x</i>Zr₂O_7+δ samples indicate that the parent compound can incorporate a substantial amount of uranium, both under oxidizing and reducing conditions. The oxidation state of these samples was investigated by X-ray photoelectron spectroscopy. The thermodynamic stability of uranium-substituted Gd₂Zr₂O₇ is an important parameter that will govern the long-term storage of uranium and minor actinides in this matrix. High-temperature calorimetry has been used to investigate the stability of the Gd_2–<i>x</i>U_<i>x</i>Zr₂O_7+δ (0.00 ≤ <i>x</i> ≤ 0.15) compositions. The standard molar free energy of the formation of Gd_2–<i>x</i>U_<i>x</i>Zr₂O_7+δ (0.00 ≤ <i>x</i> ≤ 0.15) compositions has been estimated. From the free energy of formation data, the sample corresponding to <i>x</i> = 0.15 was found to be most stable in the Gd_2–<i>x</i>U_<i>x</i>Zr₂O_7+δ (0.00 ≤ <i>x</i> ≤ 0.15) series. The relative stabilities of U⁴⁺ and U⁶⁺ substituted gadolinium zirconate have been discussed on the basis of the charge on the uranium ion and the incorporation of corresponding extra oxygen atoms into the lattice for charge compensation

Mesoporous Alumina (MA) Based Double Column Approach for Development of a Clinical Scale ⁹⁹Mo/^99mTc Generator Using (n,γ)⁹⁹Mo: An Enticing Application of Nanomaterial

This paper describes the utility of mesoporous alumina (MA), a high capacity nanomaterial based sorbent, for the development of a clinical grade ⁹⁹Mo/^99mTc generator using (n,γ)⁹⁹Mo. Synthesis of MA was performed using a glucose template in an aqueous system. Structural characterization of the nanosorbent was carried out by analytical techniques such as X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron miscroscopy (SEM), transmission electron microscopy (TEM), thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. The material synthesized was mesoporous and nanocrystalline, with average crystallite size of 2–3 nm with a large surface area of 230 ± 10 m² g^–1. In order to evaluate the surface charge of MA in aqueous solution, the zeta potential was determined at different pH environments. Adsorption characteristics of the sorbent such as time course of the adsorption, distribution ratios of ⁹⁹Mo and ^99mTc ions, Mo sorption capacity under static and dynamic conditions, ⁹⁹Mo adsorption pattern and ^99mTc elution pattern were determined to assess its effectiveness in the preparation of ⁹⁹Mo/^99mTc generator. The measured distribution ratio values indicate that ⁹⁹Mo is both strongly and selectively retained by MA at acidic pH and ^99mTc could be readily eluted from it, using 0.9% NaCl solution. The static sorption capacity and practical sorption capacity under dynamic conditions of MA was determined to be 225 ± 20 and 168 ± 12 mg Mo per gram of sorbent, respectively. With a view to realize the scope of developing clinical scale generator, a novel tandem column generator concept was used in which two ⁹⁹Mo loaded columns were connected in series. In this method ^99mTc eluted from the first column was fed to the second column to achieve higher radioactive concentration (RAC) as well as purity of ^99mTc. A 26 GBq (700 mCi) ⁹⁹Mo/^99mTc generator was developed using (n,γ)⁹⁹Mo having specific activity of ∼18.5 GBq (500 mCi)/g of Mo. The ^99mTc eluted from the generator possessed high radionuclidic, radiochemical, and chemical purity and was amenable for the preparation of ^99mTc-labeled radiopharmaceuticals. The technology can be adapted by those countries having research reactors with flux >1 × 10¹⁴ n·cm^–2·s^–1 to produce ⁹⁹Mo by (n,γ) route. The capacity of the generator can be scaled up to 260 GBq (7 Ci) using (n,γ)⁹⁹Mo produced from a reactor with flux >1 × 10¹⁵ n·cm^–2·s^–1