White light emission from a mixed organogel of lanthanide(iii)-containing organogelators

Abstract

We prepared Eu(III) and Tb(III) complexes (Eu2 and Tb2) with phenanthroline derivatives which formed organogels in n-decane. The organogels of Eu2 and Tb2 showed red and green emissions, respectively, when excited at 330 nm. TEM images of dry gels of Eu2 and Tb2 showed entangled fiber network structures with fiber diameters ranging from 20 to 60 nm. Eu2 and Tb2 formed stable mixed gels of different compositions in n-decane. The emission spectrum of a mixed gel showed emission peaks from Eu(III) at 595 and 618 nm and from Tb(III) at 496 and 551 nm when excited at 330 nm. A broad emission was observed around 470 nm that was attributed primarily to the ligands of Tb2. At a ratio of Eu2/Tb2 of 1 : 19 by weight, the mixed gel exhibited white luminescence. The CIE color coordinates of the mixed gel were x = 0.36 and y = 0.30 in the white region. The TEM image of the dry gel revealed entangled fibers with diameters ranged from 20 nm to 80 nm without evidence of self-sorting. Trimetallic organogelators, Eu4 and Tb4, were prepared by coordination of Eu2 and Tb2 with two 1,3-diketone groups. Eu4 showed three transitions of Eu(III) ion in the red region and a ligand-centered emission but Tb4 showed only a broad emission in the greenish blue region from the ligands. Eu4 and Tb4 also formed a homogeneous mixed gel in n-decane, showing a whitish luminescence at the ratio of 3 : 1 by weight.