The near-infrared luminescence of Ca6Ba(PO4)4O:Mn5+ is demonstrated and explained. When excited into the broad and strong absorption band that spans the 500–1000 nm spectral range, this phosphor provides an ultranarrow (FWHM = 5 nm) emission centered at 1140 nm that originates from a spin-forbidden 1E → 3A2 transition with a 37.5% internal quantum efficiency and an excited-state lifetime of about 350 μs. We derived the crystal field and Racah parameters and calculated the appropriate Tanabe–Sugano diagram for this phosphor. We found that 1E emission quenches due to the thermally-assisted cross-over with the 3T2 state and that the relatively high Debye temperature of 783 K of Ca6Ba(PO4)4O facilitates efficient emission. Since Ca6Ba(PO4)4O also provides efficient yellow emission of the Eu2+ dopant, we calculated and explained its electronic band structure, the partial and total density of states, effective Mulliken charges of all ions, elastic constants, Debye temperature, and vibrational spectra. Finally, we demonstrated the application of phosphor in a luminescence intensity ratio thermometry and obtained a relative sensitivity of 1.92%K−1 and a temperature resolution of 0.2 K in the range of physiological temperatures.
We analyzed and compared the unmodified and three modified zinc oxide nanoplatelet materials. The three components used in zinc oxide modification were the 4,4apos;‐bipyridine and two ruthenium (II) complexes, namely, the trans‐[Ru (bpy)(bpyCOO)Cl2]2– and cis‐[Ru (bpy)(bpyCOO)Cl2]2–. The obtained results revealed that after modification, ZnO nanoplatelets became smaller and embedded in the materials used for the modification. When ZnO was modified with either of the two ruthenium (II) complexes, the interaction between them led to a higher activity of ZnO. The metal‐to‐ligand charge transfer that was also detected in the two cases of ZnO nanoplatelets modified with the ruthenium (II) complexes caused significant alteration of the Raman spectrum and consequent changes of the optical properties. Various forms of ruthenium (II) complexes were used in several published studies related to dye‐sensitized solar cells and biomedicine. The biomedical applications include, for example, the ATP (adenosine‐5apos;‐triphosphate) detection, interaction with human serum albumin, DNA analysis, and cancer detection and treatment. The properties of the ZnO nanoplatelets modified with the two ruthenium (II) complexes presented here indicate that it may be worth exploring if the studied materials are applicable in the dye sensitized solar cells and biomedicine. Possible advantage of our results is that they were obtained at room temperature.
In this paper, we describe synthesis and characterization of YVO 4 and Eu 3+doped YVO 4 nanopowders. Two methods of preparation were used-solution combustion synthesis (SCS) and classical ceramic method (CCM)-and compared. Morphology and structure of all samples were characterized with atomic-force microscopy (AFM), X-ray diffraction (XRD), and field-emission scanning electron microscopy (SEM). Raman spectroscopy was used to discuss the isotope-like effect. It is confirmed that doping with Eu ions results in a change of Raman spectra of doped samples-new modes arise, and intensity of existing ones change. Influence of different preparation methods on isotope-like effect is presented with detailed calculations of shifted modes.
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