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One-pot synthesis of chitosan/LaF3:Eu3+ nanocrystals for bio-applications

Lanthanide-based nanocrystals have shown great potential to be used as luminescent materials but their biological applications have been limited because most of the nanocrystals synthesized so far are not water soluble or biocompatible. We report a very straightforward method to synthesize water soluble and biocompatible LaF3 nanocrystals doped with Eu3+ via facile co-precipitation with a natural biopolymer, chitosan. The nanocrystals are very fluorescent and have a small size of about 20 nm. Chitosan is found to cap the nanocrystals during the synthesis process, which renders them water soluble and biocompatible, and provides functional groups such as hydroxyl and amino groups for further attachment of biomolecules. The nanocrystals remain stable in aqueous solution with pH ranging from 2 to 7.4. The nanocrystals are very suitable for use in biological applications, for example, intracellular labelling or measurements, because they are very small in size.