ABSTRACT

We have developed a robust procedure for the visual on-site detection of zinc, cadmium and mercury metal ions in an aqueous medium using a polymeric hydrogel matrix-based colorimetric sensor. Zn²⁺, Cd²⁺and Hg²⁺, owing to their biological significant value and environmental harm, have attracted more attention. The selective detection of Zn²⁺, Cd²⁺and Hg²⁺ metal ions has always been challenging due to their closed-shell d¹⁰ electronic configuration which makes them spectroscopically silent. A polyacrylamide/carboxymethyl guargum polymeric hydrogel-based metal ion sensor was synthesized by in situ embedding 11, 16-bis (phenyl)-6, 6, 21, 21-tetramethyl-m-benzi-6,21-porphodimethene (meta-BPDM) in a host hydrogel. The meta-BPDM-embedded hydrogel shows high stability, sensitivity and selectivity when it is dipped into the aqueous solutions of Zn²⁺, Cd²⁺and Hg²⁺ metal ions. During detection, the binding of these metal ions in hydrogel causes hydrogel to change from red to bluish-green which was visually detected and confirmed by UV–visible spectroscopy. The meta-BPDM-embedded polymeric hydrogel was characterized by using solid-state UV–visible spectroscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis and its sensing properties were studied. The meta-BPDM-embedded polymeric hydrogel was found to be an excellent colorimetric sensor for Zn²⁺, Cd²⁺ and Hg²⁺ in aqueous medium without leaching of meta-BPDM from the hydrogel. The selectivity to sense these ions is mainly dependent on the binding constant of these metal ions with the meta-BPDM embedded in the hydrogel. The sensitivity of the hydrogel was 0.5, 1, and 2 mg/L with Hg²⁺, Zn²⁺ and Cd²⁺, respectively.

摘要

我们开发了一种强大的程序，用于使用基于聚合物水凝胶基质的比色传感器对水介质中的锌、镉和汞金属离子进行视觉现场检测。Zn ²⁺、Cd ²⁺和Hg ²⁺因其具有重要的生物学价值和对环境的危害而受到越来越多的关注。^{Zn 2+}、Cd ²⁺和 Hg ²⁺金属离子的选择性检测一直具有挑战性，因为它们的封闭壳 d ¹⁰电子结构使它们在光谱中无声。原位合成聚丙烯酰胺/羧甲基瓜尔胶聚合物水凝胶基金属离子传感器将 11, 16-bis (phenyl)-6, 6, 21, 21-tetramethyl-m-benzi-6,21-porphodimethene ( meta -BPDM) 嵌入宿主水凝胶中。嵌入间位-BPDM的水凝胶在浸入Zn ²⁺、Cd ²⁺和Hg ²⁺金属离子的水溶液中时表现出较高的稳定性、灵敏度和选择性。在检测过程中，这些金属离子在水凝胶中的结合导致水凝胶从红色变为蓝绿色，这可以通过紫外-可见光谱进行视觉检测和确认。元数据-BPDM包埋聚合物水凝胶采用固态紫外-可见光谱、扫描电子显微镜、X射线衍射、热重分析、傅里叶变换红外光谱、能量色散X射线分析及其传感性能进行了表征。发现嵌有间位-BPDM的聚合物水凝胶是水性介质中Zn ²⁺、Cd ²⁺和Hg ²⁺的优良比色传感器，不会从水凝胶中浸出间位-BPDM。检测这些离子的选择性主要取决于这些金属离子与嵌入水凝胶中的间位-BPDM 的结合常数。水凝胶对 Hg 的敏感性分别为 0.5、1 和 2 mg/L²⁺、Zn ²⁺和Cd ²⁺。