*2.1.2 Synthesis of Cr or Cu-doped ZnTe nanocrystals embedded in glass matrix*

The PZABP glass matrix with a nominal composition of 65P2O5 · 14ZnO · 1Al2O3 · 10BaO · 10PbO (mol %) adding 2Te (wt %), and Cr or Cu at doping *x* content varying with Zn content from 0 to 10 (wt %), were synthesized by fusion in alumina crucibles at 1300 °C for 30 minutes. These melted mixtures were quickly cooled to room temperature forming a glass system doped with the precursor ions needed for nanoparticle growth. Next, the glass samples were thermally annealed at 500 °C for 10 hours to enhance the diffusion of Zn2+, Cr2+ or Cu2+ and Te2− ions throughout the host PZABP matrix and induce the growth of Zn1-xCrxTe/Zn1-xCuxTe NCs. The physical properties of the glass samples were studied by optical absorption (OA), recorded with a model UV-3600 Shimadzu UV–VIS–NIR spectrometer, operating between 190 and 3300 nm; XRD patterns were recorded using a XRD-6000 Shimadzu diffractometer equipped with monochromatic CuKa1 radiation (k = 1.54056 Å) and set to a resolution of 0.02; Transmission electron micrographs (TEM JOEL, JEM-2100, 200 kV) and EPR measurements at temperature of 10 K were performed with a high sensitivity Bruker-EMX spectrometer operating at X-band (9.4 GHz) microwave frequency.
