Dual-target optical sensors assembled by lanthanide complex incorporated sol-gel-derived polymeric films

Sensors bearing functional units that could transform the chemical recognition into readable signals due to binding to single or even more targets have received much attention. Here, two F-/Cu2+ optical sensors based on lanthanide edifices were designed. The f-f forbidden transitions of lanthanide elements differ significantly from organic compounds since they exhibited favorable features such as narrow emissions and high color purity. Europium(III) complex of 2-(3-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline (Eu-1) and europium(III) ternary complex of 2-(3-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and dibenzoylmethane (Eu-2) showed on-off changes in responses to the guest species. The excitation wavelength of Eu-2 could be extended to nearly visible light range, and this longer wavelength sensitisation will be useful in the selection of cheap laser sources. Generally organic complexes suffered from the instabilities in practical uses, the encapsulation of indicators into hosts will be necessary. Therefore, the lanthanide containing hybrid films which were composed of cross-linked siloxane and polymeric matrices were also prepared. The inorganic-organic film could be excited at 410 nm and demonstrated improved thermal stability. Moreover, we could detect F- and Cu2+ in aqueous mixed solution and this feature would be favorable for future uses.