Luminescent hetero lanthanide coordination polymers - Characteristics and applications

Counterfeiting is an ever-increasing phenomenon, benefiting from the globalization of trade and the expansion of e-commerce. It is a threat not only to the economy, but also to public health and consumer safety (the WHO estimates that in Africa, 100,000 deaths a year are attributable to the use of counterfeit medicines, for example) . Dozens of technologies have been developed to protect against them. All have advantages and disadvantages, and each is relevant to a given market.

Heterolanthanide coordination polymers, which can be used as luminescent markers, are particularly well suited to the in-mold marking of materials where the maximum temperature reached during the manufacturing process, and the temperature of use, do not exceed a few hundred degrees. These markers can be prepared as microcrystalline powders and dispersed in the material to be marked, or as colloidal suspensions that can be used to mark inks or technical liquids.

These compounds could also find applications in the field of marking plastic waste, to ensure sorting and thus optimize recycling. For this second application, the luminescence of the markers needs to be intense enough for them to be detected, and identified, on a high-speed sorting line. Given the huge quantities of plastic produced worldwide, of which only a small proportion is recycled today, this potential application is a challenge today.

To optimize luminescence properties, it is necessary to master the intermetallic energy transfer phenomena that govern them, within coordination polymers. The aim of this article is to review the current state of knowledge concerning heterolanthanide coordination polymers and their luminescence properties.