Time resolved emission spectra and electron paramagnetic resonance studies of Gd3+ doped calcium phosphate glasses

Abstract

Gadolinium, Gd3+ (4f7 ), containing glasses are particularly interesting owing to their magnetic and optical properties. Gd3+ has an electron paramagnetic resonance (EPR) centre, which is often used as the EPR probe in different matrices. Another important feature of Gd3+ is that emits ultraviolet radiation (UVR) at around 310 â 313 nm from the 6 P7/2 ï 8 S7/2 transition and is suitable for the treatment of skin disease. Here, we report on Gd3+ doped calcium phosphate host glasses with four different concentrations; 0.5 - 4 mol % and labelled as 0.5Gd, 1Gd, 2Gd and 4Gd. A strong emission peak at 310 nm was observed in the reported glasses with excitation at 274 nm. The emission spectra can also be obtained at specific times during the decay. The time resolved emission data was analyzed with three different approaches namely, simple exponential, NED distribution and stretched exponential. The other approaches confirm the single exponential behaviour for all samples with deviation for the 0.5 Gd. The decay associated spectra (DAS) for the 0.5 Gd indicate that both decays have the same origin. The EPR spectrum exhibits several resonance signals characteristic of Gd3+ ions. The stimulated emission cross sections (Ï P EÃ 10â 21 cm2 ) of the UV emission transition 6 P7/2 ï 8 S7/2 were also reported in the above three approaches. ; The authors would like to acknowledge the financial support from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement nº REGPOT-CT2012-316331-POLARIS. Also, SHN would like to thank to Cost Action, ref. # MP 1205 under materials (soft, bio & nano) and technologies for ptofluidic devices, and further acknowledge to the FCT-Fundação para a Ciência e a Tecnologia, Portugal, hrough the project PTDC/SAU-BEB/103034/2008. ...