Photoluminescence of Eu(III)-doped lamellar bridged silsesquioxanes self-templated through a hydrogen bonding array

An organic molecule, (EtO)(3)Si(CH2)(3)NH(C =O) NH-(CH2)(12) - NH(C = O) NH(CH2)(3)Si(OEt)(3), combining urea functionalities and a 12-carbon alkyl chain, underwent sol - gel reactions in the presence of an acid catalyst, a large excess of water and variable amounts of EuCl3, giving rise to the formation of crystalline hybrids through a self- directed organization process in which hydrogen bonding interactions play a key role. Three photoluminescent lamellar Eu3+- doped silsesquioxane hybrids incorporating 1.01, 1.83 and 15.04% Eu3+ were prepared and fully characterized. The lamellar hybrids are room temperature multi-wavelength emitters due to the convolution of the hybrid's emitting centres and the Eu3+ intra- 4f(6) transitions. Their emission colour can be easily tuned along the Commission Internationale d'Eclairage chromaticity diagram from the bluish- purple region to the pink area, either by changing the excitation wavelength or the Eu3+ amount. The Eu3+ first coordination shell is very similar for the three photoluminescent lamellar Eu3+- doped silsesquioxane hybrids incorporating oxygen atoms of the carbonyl group, Cl atoms and water molecules, despite the minor variations found in the D-5(0) quantum efficiency ( 16.3 - 19.2), number of water molecules ( 1.7 - 2.0) and experimental intensity Omega(2) parameter (8.9 - 10.1 x 10(-20) cm(2)) with the increase of Eu3+ content.