We present that the stable and inert Er(III) -encapsulated complexes based on naphthalene and anthracene ligands bearing a Fréchet aryl-ether dendron exhibit much stronger near-IR emission bands bands at 1530 nm, originated from the 4f–4f electronic transition of the first excited state (4 I 13/2) to the ground state (4 I 15/2) of the partially-filled 4f shell. A strong decrease in the fluorescence of G n-aryl ether dendron (n = 0 or 2) is accompanied by strongly increasing the fluorescence intensity of the luminescent anthracene or naphthalene ligand with the generation number of the dendrons. The strong decrease of fluorescence intensity of luminescent ligand such as naphthalene and anthracene units is accompanied by strongly increasing the near infrared (IR) emission of the Er 3+ ions in Er(III) -encapsulated complexes. It could be attributed to the efficient energy transfer process occurring between the aryl-ether dendron and anthracene moiety as well as between dendritic anthracene ligand and Er 3+ ion. Thus, the emission intensity of the lanthanide complexes, upon photoexcitation of aryl-ether dendrons at 290 nm, was dramatically enhanced with an increase in the generation number n of dendrons, due to the site-isolation and light-harvesting effects. In addition, Er 3+-[ G 2- An ]3(terpy) exhibits the stronger PL intensity than Er 3+-[ G 2- Na ]3(terpy)) by 2.5 times, upon photoexcitation of aryl-ether dendrons at 290 nm. It may be due to the fact that the anthracene ligand in Er 3+-[ G 2- An ]3(terpy)) has higher spectral overlap integral (J) value than the naphthalene ligand in Er 3+-[ G 2- Na ]3(terpy) by 1.5 times. Surprisingly, all Er(III) -cored dendrimer complexes have excellent thermal- and photo-stability as well as good solubility.
Spectrally resolved confocal microscopy using lanthanide centred near-IR emission