Samarium(III) as luminescent probe for copper(II)

Lanthanide-based luminescent sensing of copper(II) is currently an active area of research given the need for determining trace amounts of the analyte in environmental and biological matrices. Moreover, the increasing interest of Cu-doped materials for a variety of applications (e.g. luminescent and plasmonic) calls for appropriate measures for the assessment of residual Cu²⁺ in the solid state. In this work, Sm³⁺ ions are investigated as luminescent probes for Cu²⁺ within a glass matrix as model system based on Sm³⁺→Cu²⁺ energy transfer. The Cu²⁺ concentration dependence of the Sm³⁺ emission quenching and decay rates of the ⁴G_5/2 excited state allow for establishing calibration curves useful for determining Cu²⁺. The luminescence-based approaches are employed for estimating residual Cu²⁺ in a Cu⁺/Sm³⁺ co-doped glass as 'unknown', the results being compared with the spectrophotometric method based on Cu²⁺ absorption in the visible. Remarkably, the approaches appeared in good agreement. Thus, the present work demonstrates the potential of Sm³⁺ ions for optical sensing of copper(II), opening research avenues extending from materials to liquid phase systems with relevance to biological and environmental sciences.