Abstract
The authors herein described a time-gated fluorescence resonance energy transfer (TGFRET) sensing strategy employing water-soluble long lifetime fluorescence quantum dots and gold nanoparticles to detect trace Hg2+ ions in aqueous solution. The water-soluble long lifetime fluorescence quantum dots and gold nanoparticles were functionalized by two complementary ssDNA, except for four deliberately designed T-T mismatches. The quantum dot acted as the energy-transfer donor, and the gold nanoparticle acted as the energy-transfer acceptor. When Hg2+ ions were present in the aqueous solution, DNA hybridization will occur because of the formation of T-Hg2+-T complexes. As a result, the quantum dots and gold nanoparticles are brought into close proximity, which made the energy transfer occur from quantum dots to gold nanoparticles, leading to the fluorescence intensity of quantum dots to decrease obviously. The decrement fluorescence intensity is proportional to the concentration of Hg2+ ions. Under the optimum conditions, the sensing system exhibits the same liner range from 1 x 10(-9) to 1 X 10(-8) M for Hg2+ ions, with the detection limits of 049 nM in buffer and 0.87 nM in tap water samples. This sensor was also used to detect Hg2+ ions from samples of tap water, river water, and lake water spiked with Hg2+ ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. In comparison to some reported colorimetric and fluorescent sensors, the proposed method displays the advantage of higher sensitivity. The TGFRET sensor also exhibits excellent selectivity and can provide promising potential for Hg2+ ion detection.