Formation and dynamics of "waterproof" photoluminescent complexes of rare earth ions in crowded environmentElectronic supplementary information (ESI) available: ESI provides details on sample preparation; photoexcitation spectrum of Tb ion; PL lifetime calculations; spectral distribution functions for transient Tb states; steady state PL data. See DOI: 10.1039/c4cp04342a

Understanding behavior of rare-earth ions (REI) in crowded environments is crucial for several nano- and bio-technological applications. Evolution of REI photoluminescence (PL) in small compartments inside a silica hydrogel, mimic to a soft matter bio-environment, has been studied and explained within a solvation model. The model uncovered the origin of high PL efficiency to be the formation of REI complexes, surrounded by bile salt (DOC) molecules. Comparative study of these REI-DOC complexes in bulk water solution and those enclosed inside the hydrogel revealed a strong correlation between an up to 5×-longer lifetime of REIs and appearance of the DOC ordered phase, further confirmed by dynamics of REI solvation shells, REI diffusion experiments and morphological characterization of microstructure of the hydrogel. Evolution of photoluminescence of rare-earth solvation complexes, interacting with bile salt molecules in a crowded bio-mimetic environment (hydrogel).