Spectral analysis in ultraweak emissions of chemi-and electrochemiluminescence systems

Investigation of ultraweak emissions in the processes of chemiluminescence, CL, and electrochemiluminesce, ECL, requires special techniques of their recording and spectral analysis. From among the hitherto proposed methods of detection of the emission spectra of these processes, that of the cut-off filter was most sensitive. The usefulness of this method in interpretation of the CL and ECL systems of the quantum yields in the range 1×10^-9-1×10^-11 containing ions and complexes of Eu（Ⅲ）, Tb（Ⅲ） and Dy0ID was shown. Exceptional character of the emission bands of lanthanide ions, being a result of the f-f electron transitions and in particular their low FWHM, permitted the appli- cation of the cut-off filter method to their analysis. The results obtained for CL and ECL on the basis of analysis of ultraweak emission proved to be successful in analytical applications. The systems containing Eu（Ⅲ） ions hydrated or complexed with organic ligands enabled inferring changes in the coordination sphere of the ions.

Luminescence properties of calcium tungstate activated by lanthanide(Ⅲ) ions

Calcium tungstate phosphors activated by the Ln3＋ ions （Ln-Pr, Nd, Tb, Yb） were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by scanning electron microscopy （SEM）, X-ray powders diffraction （XRD） and infrared spectra （FT-1R）. The samples were fotmd to show luminescence properties （down-conversion, DC, at excitation wavelength 254 nm and up-conversion, UC, at excitation wavelength 980 nm）. CaWO4 doped with Tb3＋/yb3＋ showed green DC and UC luminescence characteristic of Tb（Ⅲ） ion in the range of 470-660 nm, cor- responding to the 5D4→7F6,5,4,3,2 electronic transition. CaWO4 doped with Pr3＋/Yb3＋ showed week blue, green and red （DC and UC） luminescence of Pr（Ⅲ） ion, in the wavelength region of 450-700 nm. Emission peaks were ascribed to the 3P1→3H4,5,6, 3P0→3H4,5,6, 3P1→3F2 and 3P0→3F2 transitions, respectively. CaWO4 doped with Nd3＋/yb3＋ phosphor emitted orange UC luminescence at 450-690 nm （2p3/2→4I15/2, 4G7/2→419/2,11/2,13/2） and strong near-infrared UC luminescence at 720-900 nm （4F7/2＋4S3/2→4419/2, 4F5/2＋2H3/2→419/2, 4F3/2→4I9/2） which is the characteristic of Nd（Ⅲ） ion.

Luminescence properties of Tm^(3+) /Yb^(3+) ,Er^(3+) /Yb^(3+) and Ho^(3+) /Yb^(3+) activated calcium tungstate

CaWO4 phosphor activated by the Tm^3＋/Yb^3＋, Er^3＋/Yb^3＋ and Ho^3＋/Yb^3＋ ions were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by X-ray powders diffraction method （XRD）, infrared spectra （FT-IR） and scanning electron microscopy （SEM）. The samples were found to show up-conversion luminescence properties. CaWO4 doped with Tm^3＋/Yb^3＋ showed blue luminescence characteristic of Tm（Ⅲ） ion in the range of 460-485 urn, corresponding to the ^1G4→^3H6 electronic transition. CaWO4 doped with Er^3＋/Yb^3＋ showed strong green luminescence at 510-565 nm （^2H11/2, ^4S3/2→^4I15/2） and weak red luminescence at 640-685 nm （^4F9/2→^4I15/2） of Er（Ⅲ） ion. CaWO4 doped with Ho^3＋/Yb^3＋ phosphor emitted green luminescence at 525-560 nm （5S2, 5F4→518） and red luminescence at 6304i70 um （SFs→518） and at 730-770 nm （^5S2, ^5F4→^5I7）, which is the characteristic of Ho（Ⅲ） ion.