Abstract
Reactions of ZnSO4∙7H2O, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, [Zn(Br-1,3-bdc)(NI-mbpy-34)]n (1), under hydro(solvo)thermal conditions. Single-crystal X-ray structure analysis revealed that 1 features a three-dimensional (3-D) 2-fold interpenetrating cds (or CdSO4) net topology with the point symbol of (65·8), where the Zn(II) centers are considered as 4-connected square-planar nodes. X-ray powder diffraction (XRPD) patterns and thermogravimetric (TG) analysis confirmed that 1 shows high chemical and thermal stabilities. Notably, 1 displayed solvent dependent photoluminescence properties; the fluorescence intensity and emission maximum of 1 in different solvent suspensions varied when a solvent was changed. Furthermore, the H2O suspension of 1 exhibited blue fluorescence emission and thus can be treated as a selective and sensitive fluorescent probe for turn-on detection of Cr3+ cations through absorbance caused enhancement (ACE) mechanism and turn-off detection of Cr2O72−/CrO42− anions through collaboration of the absorption competition and energy transfer process, with limit of detection (LOD) as low as μM scale.
Highlights
The monitoring and detection of chemical pollutants and/or controlled chemicals in complicated samples are very important tasks in managing the environment, water resources, and the food industry
Infrared (IR) spectroscopy was tested in a Perkin-Elmer Frontier Fourier transform infrared spectrometer (Perkin-Elmer, Taipei, Taiwan), and the region 4000–500 cm−1 was recorded with attenuated total reflection (ATR) technique
If the Zn(II) centers are considered as 4-connected square-planar nodes and both the Br-1,3-bdc2− and NI-mbpy-34 ligands are considered as linear linkers (Figure 1a), the 3-D framework of 1 can be simplified as a 4-connected cds net topology with the point symbol of (65 ·8) (Figure 1d)
Summary
The monitoring and detection of chemical pollutants and/or controlled chemicals in complicated samples are very important tasks in managing the environment, water resources, and the food industry. Among various conventional instrumental techniques, fluorescence sensing responding to fluorescence turn on, turn off, or ratiometric signal, has attracted immense attention in recent years because of its particular aspects such as economics, user-friendliness, short response time, visualization, monitoring in real-time, excellent sensitivity, and high selectivity [1,2,3,4]. Chromium existing as Cr(III) and Cr(VI) oxidation states in the aquatic environments can directly contaminate the soil and aquatic systems. As an essential trace biological element in humans, Cr(III) is considered to be harmless and safe.
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