Highly Sensitive Strategy for Hg<sup>2+</sup> Detection
in Environmental Water Samples Using Long Lifetime Fluorescence Quantum
Dots and Gold Nanoparticles
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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 Hg<sup>2+</sup> 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 Hg<sup>2+</sup> ions were present in the aqueous solution, DNA
hybridization will occur because of the formation of T–Hg<sup>2+</sup>–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 Hg<sup>2+</sup> ions. Under the optimum conditions, the sensing
system exhibits the same liner range from 1 × 10<sup>–9</sup> to 1 × 10<sup>–8</sup> M for Hg<sup>2+</sup> ions, with
the detection limits of 0.49 nM in buffer and 0.87 nM in tap water
samples. This sensor was also used to detect Hg<sup>2+</sup> ions
from samples of tap water, river water, and lake water spiked with
Hg<sup>2+</sup> 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 Hg<sup>2+</sup> ion detection