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 calorimetric 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). (C) 2013 Elsevier B.V. All rights reserved.