Theoretical Investigation of the EPR G-Factor for the Axial Symmetry Ce3+ Center in the BaWO4 Single Crystal

The parameters g-factor (g|| and g⊥) together with the local structure of the Ce3+ center in BaWO4 single crystal (scheelite structure crystals) were theoretically investigated using a complete diagonalization procedure of energy matrix (CDM method). The intrinsic parameters were calculated. It is shown that the experimental and the calculated values of the g-factors are in good agreement. The angular distortion has also been calculated. It was found that the polar angles of the impurity–ligand bonding are smaller than in BaWO4 single crystal (Δθ≈1.00 ) . The validity of the results and the changing in the local environment of the impurity–cerium ion is also discussed.

Non-Metallic Modified Thermal Barrier Coatings

The radiation resistance and optical properties of zinc and zirconium silicate doped with cerium ion obtained by the hydrothermal microwave method are investigated. To study the radiation resistance of materials, the samples were irradiated with electrons energy of 4 MeV and a dose of 1016 el/cm2. X-ray diffraction (XRD) technique was used to characterize the phase composition of materials. To study the optical properties of materials, photoluminescence spectra were studied. Using the comparative section method, the thermal conductivity of the materials was measured. The results show that thermal barrier coatings made of cerium-doped zinc and zirconium silicate can be excellent candidates for use in space crafts and not only.

Switching Between Methanol Accumulation and Cell Growth by Expression Control of Methanol Dehydrogenase in Methylosinus trichosporium OB3b Mutant

Methanotrophs have been used to convert methane to methanol at ambient temperature and pressure. In order to accumulate methanol using methanotrophs, methanol dehydrogenase (MDH) must be downregulated as it consumes methanol. Here, we describe a methanol production system wherein MDH expression is controlled by using methanotroph mutants. We used the MxaF knockout mutant of Methylosinus trichosporium OB3b. It could only grow with MDH (XoxF) which has a cerium ion in its active site and is only expressed by bacteria in media containing cerium ions. In the presence of 0 μM copper ion and 25 μM cerium ion, the mutant grew normally. Under conditions conducive to methanol production (10 μM copper ion and 0 μM cerium ion), cell growth was inhibited and methanol accumulated (2.6 μmol·mg−1 dry cell weight·h−1). The conversion efficiency of the accumulated methanol to the total amount of methane added to the reaction system was ~0.3%. The aforementioned conditions were repeatedly alternated by modulating the metal ion composition of the bacterial growth medium.

Enhanced Crystallinity and Luminescence Characteristics of Hexagonal Boron Nitride Doped with Cerium Ions According to Tempering Temperatures

Hexagonal boron nitride was synthesized by pyrolysis using boric acid and melamine. At this time, to impart luminescence, rare earth cerium ions were added to synthesize hexagonal boron nitride nanophosphor particles exhibiting deep blue emission. To investigate the changes in crystallinity and luminescence according to the re-heating temperature, samples which had been subjected to pyrolysis at 900 °C were subjected to re-heating from 1100 °C to 1400 °C. Crystallinity and luminescence were enhanced according to changes in the reheating temperature. The synthesized cerium ion-doped hexagonal boron nitride nanoparticle phosphor was applied to the anti-counterfeiting field to prepare an ink that can only be identified under UV light.

Reduced Graphene Oxide-Resorcinol Nanocomposite: A Chemosensor for the Detection of Cerium Ions

A hybrid material reduced graphene oxide based organic nanocomposite was synthesized from graphite by modified Hummers method, which is further chemically reduced to form reduced graphene oxide (rGO) and with resorcinol through a solvothermal process a reduced graphene oxide-resorcinol (rGO-R) nanocomposite was obtained. The synthesized materials surface morphology and structural compositions were studied through X-ray diffraction (XRD) and scanning electron microscope (SEM) and their optical properties were studied through UV-visible spectroscopy and photoluminescence. The material was further used as a fluorescent chemosensor to detect cerium ion under aqueous conditions. The rGO-R composite’s sensing abilities were studied by following parameters viz. pH, reversibility, time and the interference of other probable competing ions. The sensing follows both the photo-induced electron transfer and intramolecular charge transfer processes.