Europium-doped GdVO_4 nanocrystals as a luminescent probe for hydrogen peroxide and for enzymatic sensing of glucose

摘要

The authors describe the preparation of Eu~(3+)-doped GdVO_4 nanocrystals (NCs) by precipitation of the Gd~(3+)(Eu~(3+) )-citrate complex which was then converted to the respective vanadate by dialysis. The fractions of Eu~(3+) ranged from 5 to 100mol%. The NCs were characterized by XRD, TEM, ICP-OES and dynamic light scattering which revealed that they possess superior colloidal stability in aqueous solutions in that no precipitation can be observed even after several months. The NCs display red and largely red-shifted fluorescence (peaking at 618 nm) on photoexcitation at around 300 nm. Fluorescence is strongly quenched by hydrogen peroxide. It is also shown that the fraction of doping with Eu~(3+) strongly affects quenchability. Most efficient quenching by H_2O_2 is observed if the NCs are doped with 50% of Eu~(3+). The findings were exploited to develop a fluorometric assay for H_2O_2 that works in the 5 to 250 μM concentration range, with a limit of detection as low as 1.6 μM (at a signal-to-noise ratio of 3). The probe was further employed to design a highly sensitive enzymatic assay for glucose via measurement of the quantity of H_2O_2 formed as a result of the catalytic action of glucose oxidase.