Responsive hydrogel sensing materials have been fabricated using three dimensional (3D) polymerized colloidal photonic crystals (PCPCs) for highly sensitive and selective detection of hazardous metal ions in seawater at ultra-low concentration. Due to periodically ordered lattice of the embedded photonic crystals, the hydrogel diffracts light in visible spectral range according to the Bragg's law. When the hydrogel is functionalized by spatially distributed –SH groups through cleaving –S–S– bonds in grafted N,N′-cystaminebisacrylamide molecules, the functionalized hydrogel can selectively bind with mercury ions (Hg2+) to form –S–Hg–S– bridge bonds in seawater. The Hg2+ binding causes the volume of the hydrogel to shrink, corresponding to a wavelength shift of the light diffracted by the hydrogel, while the shifted wavelength is proportional to the amount of bound Hg2+ ions, which enables the quantitative evaluation of Hg2+ ions with a limit of detection at 10−9 M level in seawater, as measured by a portable spectrometer. When the hydrogel is functionalized with crown ether molecules containing the smallest cavities, the grafted benzo-9-crown-3 can strongly and selectively chelate with beryllium ions (Be2+) in solution, which enables the detection of the smallest metal ions Be2+ quantitatively at a detection of limit of 10−11 M in seawater. With this intelligent hydrogel sensors, we demonstrate a simple method for the rapid in situ monitoring and detection of hazardous metal ions such as Hg2+ and Be2+ at ultra-low concentrations in seawater.

Fabrication of intelligent colloidal photonic crystal hydrogels for sensing trace metal in seawater

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.