Abstract
The thesis is forcing on the study of afterglow properties for two categories of phosphate compounds. They were synthesized using long-linear alkyl chain diamines under hydrothermal conditions. Three compounds are presented, all were structurally characterized in detail by single-crystal X-ray diffraction methods to facilitate elucidation of the structure-property relationships. By UV-light excitations, one would display fluorescence in green while the other two in yellow. Remained emissions were observed for some time after removal of the UV-light source for all three compounds. The afterglow properties were studied to disclose possible emission origins and mechanisms and factors governing the lifetime. Category A contains one gallium phosphate, (H2DADD)[Ga2O2(HPO4)2] (A1; where DADD = 1,12-Diaminododecane). It adopts a two-dimensional layered structure with DADD deprotonated, residing between two adjacent layers. The inorganic [Ga2O2(HPO4)2] layer is built up with infinite octahedral chains of GaO6, and HPO4 tetrahedra. The duration of the afterglow emission for A1 was up to two seconds. The afterglow was suspected to associate with lattice defects related to trapped electrons. Such kind of defects was diagnosed on A1 by electron paramagnetic resonance (EPR) spectral study. Factors that could affect the duration of the afterglow emission were found to closely relate to hydrogen bonding pattern between the organic species and the inorganic layers. The presence of heavy metal ions could as well play a role to extend the lifetime of the afterglow emission. Category B consists of two compounds synthesized using the organic acid, 2,6- naphalenedicarboxylicacid (NDC), combined with DADD or 1,10-diaminodecane (DAD), and having the formulas (H2DADD)4(NDC)(HPO4)2(H2PO4)2·2H2O (B1), and (HDAD)4[Ga6(OH)4(NDC)(HPO4)8] (B2). Both showed yellow light afterglow, with a duration up to two seconds. But the lifetime was a bit shorter for B1 than B2. Presumably the lifetime can be enhanced by metals and B1 contains no metal ions in structure. The lattice defects in series B is similar to that of series A. Compared to A1, the emission bands of B1 and B2 both red-shifted approximately by 50 nm. It is likely due to the presence of NDC in addition to the amines.