Antenna Effect on the Organic Spacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection of Vanadate Ions over a Wide pH Range

摘要

The excitation of the adsorbed vanadate group led to the red emission arising from the efficient energy transfer to Eu-doped layered gadolinium hydroxide (LGdH:Eu). This light-harvesting antenna effect allowed LGdH:Eu to detect selectively a vanadate in aqueous solution at different pHs. Because vanadate exists in various forms by extensive oligomerization and protonation reactions in aqueous solution depending on pH, it is important to detect a vanadate regardless of its form over a wide pH range. In particular, spacer molecules with long alkyl chains greatly facilitated access of a vanadate antenna into the interlayer surface of LGdH:Eu. The concomitant increase in adsorption capacity of LGdH:Eu achieved a strong antenna effect of vanadate on the red emission from Eu3+. When a suspension containing LGdH:Eu nanosheets (1.0 g/L) was used, the vanadate concentration down to 1 X 10(-5) M could even be visually monitored, and the detection limit based on the D-5(0) -> F-7(2) emission intensity could reach 4.5 x 10(-8) M.