Novel borosilicate glasses were developed by adding in the glass batch Er³⁺–Al₂O₃ nanoparticles synthetized by using a soft chemical method. A similar nanoparticle doping with modified chemical vapour deposition (MCVD) process was developed to increase the efficiency of the amplifying silica fibre in comparison to using MCVD and solution doping. It was shown that with the melt quench technique, a Er₃₊–Al₂2O₃ nanoparticle doping neither leads to an increase in the Er³⁺ luminescence properties nor allows one to control the rare-earth chemical environment in a borosilicate glass. The site of Er³⁺ in the Er³⁺–Al₂O₃ nanoparticle containing glass seems to be similar as in glasses with the same composition prepared using standard raw materials. We suspect the Er³⁺ ions to diffuse from the nanoparticles into the glass matrix. There was no clear evidence of the presence of Al₂O₃ nanoparticles in the glasses after melting.