Lanthanide–based luminescent hybrid silica materials prepared by sol-gel methodologies: a review

Research in the field of lanthanide-based luminescent hybrid silica materials has grown substantially in the last decades, given the unique spectroscopic properties of lanthanide(III) complexes and the stability and biocompatibility of silica hosts. The versatility of the sol-gel technique to produce glasses, fibers, films, nanoparticles and ceramics has turned it into one of the most powerful methods to achieve such goals. This review describes the most commonly used sol-gel strategies to insert a luminescent lanthanide(III) complex inside a silica host and their potential applications, with the aim to help in the choice for a particular functional material. In particular, the focus is set on the different approaches developed to embed the visible or near infrared emitting guest in the silica matrix, either by entrapment within the three-dimensional network, anchoring on the surface of a nano or microparticle or inclusion in a mesopore. In addition, the usual organic ligands and the different functionalization strategies are discussed.