Silica nanospheres functionalized by a rhodamine-based Hg(II)-sensing probe having two sensing channels: Preparation, characterization and sensing performance

In this paper, we designed and synthesized a rhodamine derived probe of (E)-2-(3′,6′-bis(ethylamino)-2′,7′-dimethyl-3-oxospiro[isoindoline-1,9′-xanthene]-2-ylimino)acetaldehyde (denoted as Rb–CO). The photophysical measurement on this probe suggested that its absorption and fluorescence increased with the increasing Hg(II) concentration, showing two sensing channels of colorimetric and fluorescence sensing. In addition, Rb–CO owned high selectivity and good linear response towards Hg(II). Rb–CO was then grafted onto a supporting matrix of silica nanospheres, resulting in a Hg(II) sensing system of Rb@SiO2 which was identified and characterized by electron microscopy, IR spectrum and thermogravimetry. The corresponding photophysical measurements confirmed that the absorption and fluorescence of Rb@SiO2 also increased with the increasing Hg(II) concentration. Both sensing channels had shown good selectivity, linear response and high photostability towards Hg(II).