Recyclable nitrite sensing composites with core-shell structure and rhodamine-based probe

Nitrite is an important analytical target owing to its reaction with amines in living bodies which releases carcinogenic nitrosamines and increases cancer risk and deformities. It is thus important to develop sensors for nitrite detection. In this paper, two site-specific nanocomposite samples (denoted as R6@MCM-41@Fe3O4 and RS6@MCM-41@Fe3O4, respectively) were designed for nitrite sensing. A core-shell structure was adopted in these composite samples, using Fe3O4 as core, two rhodamine derivatives (R6-NH2 and RS6-NH2) as chemosensor and MCM-41 as supporting shell, respectively. Here Fe3O4 means ferriferrous oxide, R6-NH2 and RS6-NH2 denote 2-amino-3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one and 2-amino-3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthene]-3-thione, MCM-41 is a silica molecular sieve, respectively. These nanocomposite samples were characterized and confirmed by electron microscopy images, XRD patterns, N-2 adsorption/desorption, magnetic feature, IR spectra, thermogravimetric analysis. Their sensing performance towards nitrite was evaluated by their emission spectra upon various nitrite concentrations. Limit of detection was determined as low as 1.3 mu M. Further analysis suggested that these sensing composite samples followed a static additive reaction between NO+ and our chemosensors. In addition, these sensing composites could be recycled by sulphamic acid. (C) 2016 Elsevier B.V. All rights reserved.