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Yun Gao , Li Liang , Wei Gao (2014). Randic Index and Edge Eccentric Connectivity Index of Certain Special Molecular Graphs. International Journal of Chemistry and Materials Research, 2(8): 81-87. DOI:
In this paper, we determine the Randic index and edge eccentric connectivity index of fan molecular graph, wheel molecular graph, gear fan molecular graph, gear wheel molecular graph, and their r-corona molecular graphs.
Photoluminescence Characteristics of the Caal2o4: Eu2+ Co-Doped With Ion Dy3+ Synthesized By Combustion Method
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Nguyen Ngoc Trac , Nguyen Manh Son , Phan Tien Dung (2014). Photoluminescence Characteristics of the Caal2o4: Eu2+ Co-Doped With Ion Dy3+ Synthesized By Combustion Method. International Journal of Chemistry and Materials Research, 2(8): 75-80. DOI:
The phosphors of CaAl2O4: Eu2+, Dy3+ with varying concentrations were synthesized by combustion method. The monoclinic single phase structure of CaAl2O4 was investigated by X-ray diffraction. The emission spectra of phosphors had a broad band with maximum at 444 nm due to electron transition from the 4f65d1 to the 4f7 of Eu2+ ion and a small peak at 575 nm due to 4F9/2 6H13/2 transition of Dy3+ ions. The excitation spectra and the decay time of phosphors were investigated also. The phosphors of CaAl2O4: Eu2+, Dy3+ had long persistence luminescence. In these phosphors, Eu2+ ions play the role of activators. Whereas, Dy3+ ions generate the hole traps that lead to the long persistent phosphorescence and act as the activators in the phosphors simultaneously. The concentration of Dy3+ ion co-doped has strong influence on the luminescence of phosphor.