Silane-modified layered double hydroxides with europium sensor for aqueous singlet oxygen detection

A silane-modified layered double hydroxide (LDH) hybrid with a covalently coupled europium complex for aqueous singlet oxygen ( 1 O 2 ) detection is presented. A Mg/AL-LDH is modified with two alkoxysilanes simultaneously to increase its covalent linkability (using –SH or –NH 2 groups) and to improve its dispersibility in water (using –N + (CH 3 ) 3 groups). The 1 O 2 -responsive europium complex is coupled to the –SH or –NH 2 - modified LDH employing epoxyphenanthroline (5,6-Epoxy-5,6-dihydro- [1,10]phenanthroline, “ephen”), which is acting as an ancillary ligand to the europium via its hetero-aromatic N-atoms on one hand and allows the covalent linkage of its epoxy-group to the modified LDH on the other hand. In this manner, the silane chains keep the europium complex away from the chemically active LDH surface, hence maintaining its structural integrity and photophysical properties. The result is a water-dispersible probe with a remarkable response to 1 O 2 . This is signaled by the significant increase in the characteristic Eu 3+ emission at 613 nm resulting in up to a 27-fold increase in emission intensity on exposure to 1 O 2 having a decay time of 380 μs. The resulting Eu-LDH hybrid is applicable for heterogeneous aqueous 1 O 2 detection; its long decay time, useful in time-gated measurements, in conjunction with the biocompatibility of LDH makes it particularly suitable for biological matrices, where 1 O 2 needs to be monitored. • Modified Mg/Al-LDH with functional alkoxysilanes for increased water dispersibility and covalent coupling to singlet oxygen sensitive europium complex. • Silane modification preserved the structure and photophysical properties of the europium complex. • The resulting Eu-LDH hybrid showed a 27-fold increase in emission intensity at 613 nm upon exposure to 1 O 2 . • The long decay time of 380 μs and the biocompatibility of LDH make this hybrid sensor particularly suitable for 1 O 2 monitoring biological settings.