Rozalia Czoik

Ultraviolet-to-visible downconversion luminescence in solgel oxyfluoride glass ceramics containing Eu 3+ :GdF 3 nanocrystals

GdF3 nanocrystals doped with Eu3+ ions in oxyfluoride glass ceramics were prepared by a solgel method. The structural properties were examined by x-ray diffraction measurements. The effects of gadolinium codoping on europium emission in the prepared solgel glasses and glass ceramics have been studied. The emission bands originating from the 5D0 state of Eu3+ ions are enhanced under excitation of Gd3+ ions by 273 nm line. The electric dipole 5D0→7F2 transitions were dominant in the samples before heat treatment, whereas magnetic dipole 5D0→7F1 transitions had a higher probability in the samples after annealing. The luminescence lifetime for the 5D0 level of Eu3+ ions in the samples after excitation at 273 nm is long lived in comparison to excitation at 393 nm and increased to 190%. Energy transfer from Gd3+ to Eu3+ was observed.

Emission of Eu3+ in sol-gel oxyfluoride glass materials obtained by different preparation methods

Abstract Silica glasses doped with Eu 3+ ions prepared by sol-gel methods were investigated. The X-ray diffraction (XRD) was used to verify the nature of the studied systems. Excitation and emission spectra of Eu 3+ ions in sol-gel glass materials were detected. Red-to-orange luminescence intensity ratios R/O related to integrated intensities of 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 transitions and luminescence lifetimes for 5 D 0 state of Eu 3+ ions were determined. The results indicated that spectroscopic parameters for Eu 3+ ions strongly depended on reagents and their relative ratios used for sol-gel glass preparation.

A Highly Sensitive Spectrophotometric Method for Gallium Determination with Chrome Azurol S in the Presence of Mixed Cationic-Nonionic Surfactants and its Application in Plant Analysis

ABSTRACT A simple and very sensitive spectrophotometric method determining microgram quantities of gallium (Ga) has been developed. The method is based on the complex of Ga(III) with Chrome Azurol S (CAS) in the presence of benzyldodecyldimethylammonium bromide (ST) and polyoxyethylenesorbitan monopalmitate (Tween 40). The complex forms in weakly acid solution (pH 3.8) and shows the absorption maximum at 627 nm. The molar absorptivity (ε) of this system is 1.87 × 105 L mol−1 cm−1, and it is clearly higher than ε of other spectrophotometric methods of gallium determination. The detection and quantification limits (LOD, LOQ) are 7.6 × 10–3 and 0.023 µg mL−1, respectively. Beer‘s law is obeyed in the range from 0.02 to 0.60 µg mL−1 of Ga. The precision and accuracy are good. This first spectrophotometric method of Ga(III) determination in the four-component system has been successfully applied for the analysis of mushrooms and grasses with low content of gallium.