Regenerable Multifunctional Mesoporous Silica Nanocomposites
for Simultaneous Detection and Removal of Mercury(II)
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Abstract
Mercury
(Hg<sup>2+</sup>) is a highly toxic and widespread environmental
pollutant. Herein, a regenerable and highly selective core–shell
structured magnetic mesoporous silica nanocomposite with functionalization
of thymine (T) and T-rich DNA (denoted as Fe<sub>3</sub>O<sub>4</sub>@nSiO<sub>2</sub>@mSiO<sub>2</sub>-T-TRDNA nanocomposite) has been
developed for simultaneous detection and removal of Hg<sup>2+</sup>. In this work, the thymine and T-rich DNA were immobilized onto
the interior and exterior surface of outermost mesoporous silica,
respectively. The detection mechanism is based on Hg<sup>2+</sup>-mediated
hairpin structure formed by T-rich DNA functionalized on the exterior
surface of the nanocomposites, where, upon addition of SYBR Green
I dye, strong fluorescence is observed. In the absence of Hg<sup>2+</sup>, however, addition of the dye results in low fluorescence. The limit
of detection for Hg<sup>2+</sup> in a buffer is 2 nM by fluorescence
spectroscopy. Simultaneously, the Fe<sub>3</sub>O<sub>4</sub>@nSiO<sub>2</sub>@mSiO<sub>2</sub>-T-TRDNA nanocomposite features a selective
binding with Hg<sup>2+</sup> between two thymines immobilized at the
interior surface of the mesopores and exhibits efficient and convenient
Hg<sup>2+</sup> removal by a magnet. Kinetic study reveals that the
Hg<sup>2+</sup> removal is a rapid process with over 80% of Hg<sup>2+</sup> removed within approximately 1 h. The applicability of the
developed nanocomposites is demonstrated to detect and remove Hg<sup>2+</sup> from samples of Xiangjiang river water spiked with Hg<sup>2+</sup>. In addition, distinguishing aspects of the Fe<sub>3</sub>O<sub>4</sub>@nSiO<sub>2</sub>@mSiO<sub>2</sub>-T-TRDNA nanocomposites
for Hg<sup>2+</sup> detection and removal also include the regeneration
using a simple acid treatment and resistance to nuclease digestion.
Similar process can be used to functionalize the Fe<sub>3</sub>O<sub>4</sub>@nSiO<sub>2</sub>@mSiO<sub>2</sub> nanocomposites with other
nucleic acids and small molecules for environmental and biomedical
applications