Significant enhancement in Eu3+/Eu2+ emissions intensity by CdS quantum dots, in chloroborosilicate glasses

Eu3+ and CdS were singly doped and co-doped into chloroborosilicate glasses with composition 37.8SiO2-27B2O3-18BaO-3.6K2O-3.6Al2O3-10BaCl2 (mol%), by one-step melt quench technique. The samples were characterized by transmission electron microscopy (TEM), UV-Vis absorption, excitation, and emission spectroscopy. TEM images revealed the presence of CdS quantum dots (QDs) of size 5-20 nm in the CdS-doped glasses. The Eu-doped glass shows characteristic orange emission of Eu3+ at 393 nm excitation, while excitation at 250 and 317 nm revealed the existence of Eu2+ ions. There are strong evidences of energy transfer involving the charge transfer band (CTB) and different energy levels of Eu2+ and Eu3+ ions. The CdS-doped glass showed broad emission bands, originating from various electronic transitions involving defect and trap states in CdS crystalline structure. The emission band in the lower wavelength region, shows a red shift with increasing excitation wavelength, which proves the quantum confinement effect in CdS QDs. Eu/CdS co-doped glasses showed significant enhancements in Eu3+/Eu2+ emissions, up to 20 and 70 times, upon excitations at 393 and 317 nm, respectively, which is considerably higher compared to previously reported similar systems. This enhancement is attributed to a complex energy transfer occurring between Eu2+/Eu3+ and CdS QDs, reported for the first time in a glassy system, especially considering the in-situ growth of the QDs during melt. The co-doped glass also showed pure white emission at 6-7 nm slit width upon 387 nm excitation, which is a novel finding from an Eu/CdS co-doped glass.

Automated summary

Eu3+ and CdS were singly doped and co-doped into chloroborosilicate glasses. The co-doped glass showed significant enhancements in Eu3+/Eu2+ emissions and exhibited pure white emission.