Spectroscopic properties and fluorescent recognition of dye sensitized layered lutetium-terbium hydroxides

Abstract

The layered rare earth hydroxides have attracted increasing interests due to their diverse chemical composition and tunable spectroscopic properties. In this paper, a novel Tb3+ activated layered lutetium hydroxide (LLuH:Tb) was fabricated, in which the inorganic NO3− ions were ion-exchanged with organic (ibuprofen or dodecylsulfonate) anions. After the ion-exchange reaction, the organic anions intercalated LLuH:Tb showed the distinct lamellar structure with the interlayer distance of about 2.56 nm, confirming the formation of inorganic/organic hybrid assembly. The dye ibuprofen-intercalated hybrid effectively promoted the characteristic 5D4 → 7F5 green emission of Tb3+ in the host but failed to be exfoliated into nanosheet colloid. On the contrary, the dodecylsulfonate-intercalated hybrid was readily to be exfoliated into nanosheet colloid by dissolving in formamide solvent, but the green emission of Tb3+ was too weak to be observed. To take advantage of their respective merits and explore the practical uses, certain amounts of dye ibuprofen were directly added to the dodecylsulfonate-intercalated hybrid colloid. Excited with the ultraviolet light, the characteristic green fluorescence of Tb3+ was dramatically enhanced, indicating that the dye was a superior light-harvesting antenna to sensitize the activator Tb3+. The dye sensitized hybrid colloid was very stable at ambient temperature and exhibited excellent fluorescent recognition for Cu2+ ions over other metal ions in aqueous solution due to the large fluorescence quenching. The detection limit for Cu2+ ion reaches 7.63 × 10−7 mol/L, which is far lower than the limitation of Cu2+ in drinking water recommended by the World Health Organization (1.57 × 10−5 mol/L). The fluorescence enhanced/quenched sensor with excellent stability exhibits a high potential for the detection of Cu2+ in routine environmental water.