The extraordinary long phosphorescence of SrAl2O4:Eu 2+ :Dy 3+ has been widely studied in powder samples due to its broad range of applications in this form and despite the fact that the bulk material shows higher intensity emission and longer afterglow. However, the investigation of SrAl2O4:Eu 2+ :Dy 3+ crystals that, unlike the powder do not contain surface defects, would allow a better insight into the mechanism that governs the long-lasting phosphorescence of this co-doped material. Thus, a SrAl2O4:Eu 2+ :Dy 3+ single crystal was studied in detail by absorption spectroscopy and photoluminescence, including a novel estimation of its extinction coefficient. In addition, thermoluminescence measurements and wavelength dependent quantum efficiencies measurements have been performed to improve the understanding of the role of both europium and dysprosium ions in the corresponding persistent phosphorescence mechanism.

A simple but versatile nanoporous silica-based optical sensor was synthesized and characterized using different techniques such as XRD, BET, TGA, and FT-IR.

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A novel organic-inorganic silica-based fluorescent probe was designed, synthesized and characterized by different techniques such as XRD, BET, TGA, and FT-IR. The fluorescence properties of the probe were studied in the presence of a variety of metal-ions in water. The results revealed that various metal-ions negligibly vary the emission intensity of the probe except for Hg 2+ , which quenched the intensity dramatically. The selectivity of the probe toward Hg 2+ ion was further investigated in the presence of common competing metal-ions and the results demonstrated the high selectivity of the probe toward Hg 2+ ion. The fluorescence emission of the probe was also studied as a function of the concentration of Hg 2+ ion. A nanomolar limit of detection was estimated for Hg 2+ , indicating a high sensitivity. Furthermore, the probe showed INHIBIT-type logic behavior with Hg 2+ and H + as inputs. Also, the optimum pH range was studied in addition to reversibility and real world applicability of the probe.

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