Study on the construction and performance of a Hg(II)-sensing system having an “off–on” probe derived from rhodamine and an up-conversion excitation core

In this work, a rhodamine derivative was synthesized and grafted onto the surface of an up-conversion host of β-NaYF4:Yb3+/Er3+, resulting in a Hg(II)-sensing system. The obtained nanocomposite was fully characterized and studied by electron microscopy images, wide-angle XRD diffraction patterns, IR spectra and thermogravimetry, which confirmed the successful construction of the nanocomposite. The analysis on absorption and emission spectra suggested that the up-conversion host could efficiently excite the probe, which was later proved by the emission decay characteristics. The sensing performance of the nanocomposite towards Hg(II) was studied by steady emission spectra. It was found that the fluorescence from the probe increased with the increasing Hg(II) concentration, showing an “off–on” effect. In addition, the fluorescence enhancement effect could be activated only by Hg(II), suggesting that the nanocomposite owned a high selectivity towards Hg(II).