Amine Functionalized Cross-Linked Hybrid Full Color Phosphors Lacking   Metal Activator Ions
  White light tunable phosphors are obtained from a sol-gel derived siliceous network to which oxyethylene units are covalently grafted by means of urea or urethane cross-linkages. The bright photoluminescence is ascribed to an unusual convolution of distinct emissions originated in the NH groups of the urea or urethane bridges and in the siliceous nanodomains. The lifetimes of these emissions show a remarkable temperature dependence of approximately six orders of magnitude between $\approx 220$ and 300 K associated with the hybrids glass transition temperature. This set of xerogels is one of the most surprising classes of full color emitters lacking metal activator ions. 
L. D. Carlos, R. A. Sa Ferreira, V. De Zea Bermudez, and Sidney J.L.   Ribeiro