Near-Infrared NIR Emitters

A fundamental issue concerning the emission efficiency relates to the control of nonradiative decays (NRDs) for Ln excited states. Lowering NRD can be achieved by locating the active ion in a low-phonon host and in this way, different Er -doped metal oxides have also been obtained by the SGM. Nb20s [30], ZrOa-HfOi [31-37], TajOs [38,39], AI2O3 [40], SnOi [41], TiOi [29,42], and 

Interestingly enough, the results clearly indicate that for the richer compositions in Ta20s, most of the Er ions are located in an environment rich in Ta205. Broadest emission bands are the holy grail for those working in the development of Er materials for optical amplification. 

Despite the presence of organic counterparts and therefore higher phonon energies, Er emission may be observed in OIH as well. As an example, Er -doped diureasils were obtained from different carboxylic acid solvolysis routes [44]. Characterization techniques included X-ray absorption (EXAFS) at the Er Lm-edge, FTIR, and photoluminescence. Judd-Ofelt intensity parameters (Q ) were evaluated from absorption measurements together with the Er Iis/2 radiative lifetime (trad) and the peak emission cross section (cem)- Values so 

420 nm) with Er absorption line assigned, (b) NIR photoluminescence spectra obtained under 488 nm excitation for diureasil samples containing 5 mol% (i), 10 mol% (ii), and 20 mol% (iii) Er. (Adapted with permission from Ref. [44].) 

NIR emission could be observed through energy transfer from the ligands to the active Ln ion (in this case, Ln Er, Sm, Yb, Nd). 

---