Study of photoluminescence properties of Er<SUP>3+</SUP> ions in SiO<SUB>2</SUB>–GeO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> nanoparticles

We have used the sol–emulsion–gel method to prepare nanoparticles of SiO<SUB>2</SUB>, SiO<SUB>2</SUB>–GeO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> doped by the same concentration Er<SUP>3+</SUP> ions for comparison. We have compared the luminescent efficiencies of these particles and we found that the luminescence spectra and lifetime of the excited state <SUP>4</SUP>&#8739;<SUB>13/2</SUB> of Er<SUP>3+</SUP> ions are found to be sensitive to the nature of host. A broad emission spectrum of width 58–55 nm peaked at wavelength of 1.5 μm and the decay times of <SUP>4</SUP>&#8739;<SUB>13/2</SUB>→<SUP>4</SUP>&#8739; <SUB>15/2</SUB> transition are 7.57 and 2.07 ms for 1000 °C heat-treated 1.0 mol% Er<SUP>3+</SUP> doped SiO<SUB>2</SUB>–GeO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> nanoparticles, respectively. The analysis suggests that modification of relaxation mechanism is due to the nature of the host