No abstract

In this work, the combination of three different thermal lens spectroscopic methodologies was used to better determine the fluorescence quantum yield and to observe the concentration quenching in Yb 3þdoped binary tellurite glasses (in mol%, 80TeO 2 e 20Li 2 O and 80TeO 2 e 20WO 3). The samples were synthesized by the conventional melt-quenching method and then studied using optical spectroscopy and thermal lens spectroscopy (TLS). These characterizations enabled investigation of the radiative and nonradiative processes involved in the ytterbium doped systems. High fluorescence quantum yield was obtained for low Yb 3þ doping (>90%), and in both glasses the Yb 3þ presented concentration quenching mainly caused by impurities, host-ion interaction and OH À vibrations. The observations suggested that there is a possibility of doping the glasses with higher Yb concentration (>1.6 Â 10 21 ions/cm 3) with low reduction of the quantum yield.

A B S T R A C TIn this work, a lithium tellurite glass (80TeO 2 − 20Li 2 O, in mol%) was synthesized and its optical properties were analyzed. This glass matrix has been extensively studied, mainly due to its highly nonlinear optical properties, but there have been no reports concerning its luminescence properties. To the best of our knowledge, this is the first observation of visible emission related to Te 4+ centers in a lithium tellurite glass. A broad and intense emission band was centered at 650 nm and there was a broad excitation band in the UV-Vis region. The emission lifetime at room temperature was approximately 7.0 ± 0.2 μs and the fluorescence quantum efficiency was 63 ± 6%. These characteristics indicated that the system consisting of Te 4+ centers in lithium tellurite glass is a good candidate as a phosphor material for various applications.

An uncommon emissive pseudotetranuclear compound, {[Au(CHNS)][Au(CHNS)](PF)}, was synthesized and characterized in terms of its structure and optical properties. The synthesis produced a crystalline compound composed of four gold atoms with two different oxidation states (Au and Au) in the same crystalline structure. The title complex belonged to a triclinic crystalline system involving the centrosymmetric P1̅ space group. X-ray diffractometry and vibrational spectroscopy (infrared, Raman, and SERS) were used for structural characterization of the new crystal. The vibrational spectroscopy techniques supported the X-ray diffraction results and confirmed the presence of bonds including Au-Au and Au-S. Optical characterization performed using UV-vis spectroscopy showed that under ultraviolet excitation, the emissive crystalline complex presented characteristic broad luminescent bands centered at 420 and 670 nm.