No abstract

This work presents the production and characterization of a new prolific binary glass system based on SbPO 4-GeO 2. The dependence of GeO 2 content on thermal, structural and optical properties were investigated by means of thermal analysis, Raman, UV-Vis-NIR, infrared, M-lines and EPR spectroscopy. Glass transition temperatures remain constant around 410°C when GeO 2 content is increased, indicating that GeO 4 units are not responsible for increasing the connectivity of PO 4 units. Thermal stability linearly increases as a function of GeO 2 content, reaching a value around 400°C for glass containing 90 mol% of GeO 2. Raman spectroscopy was used to evaluate the glass structural changes when GeO 2 is incorporated from 30 to 90 mol% indicating a gradual change from a phosphate to a germanate glass skeleton. The optical window extends from 350 nm at UV region, up to 2.7 μm in the middle-infrared region limited by the multiphonon cutoff due to the strong OH absorption. M-lines technique shows that increasing GeO 2 content decreases the refractive index, mainly because the lower concentration of higher polarizable antimony atoms. EPR spectra of heat treated V 2 O 5 doped glasses, at different temperatures above the glass transition temperature, shows the characteristic eight-line hyperfine splitting spectrum. The spin Hamiltonian parameters obtained from the simulated spectra indicates that the paramagnetic tetravalent vanadium ions in the glasses exist as vanadyl form VO 2+ , located in axially distorted octahedral sites. For glasses treated at higher temperatures a second VO 2+ component appears in the EPR spectra and the analysis of the spin-Hamiltonian parameters suggests that these vanadyl ions are in more tetragonal distorted octahedral sites than those in the glass.

In the search for understanding and improving the luminescence of optical materials based on Ir(III) complexes, three [Ir(C ∧ N) 2 (dnbp)] + (dnbp = 4,4′-dinonyl-2,2′-bipyridine) emitters were immobilized in MCM-41 mesoporous nanoparticles. By taking advantage of the amphiphilic nature of [Ir(C ∧ N) 2 (dnbp)] + , the complexes were mixed with an appropriate surfactant and the resulting micelles served as templates for the synthesis of mesoporous silica host materials in a one-step sol−gel route. The MCMencapsulated [Ir(C ∧ N) 2 (dnbp)] + complexes present intense emissions with prominent rigidochromic spectral changes that are substantially less affected by O 2 as compared to methanolic solutions, with a thousand-fold decrease in quenching rate constants. These photophysical results points to a possible suitability of Ir(III)-complex−MCM-41 host−guest systems for possible future optoelectronic devices, rigidity optical sensors, or biological markers in different colors.