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Pyridine Appended Poly(Alkyl Ether) Based Ionogels for Naked Eye Detection of Cyanide Ions: A Metal-Free Approach
Bhaswati Sarkar, Prabakaran P., ,
Published in ACS Publications
Volume: 8
Issue: 22
Pages: 8327 - 8337
The present study initiates applications of ionogels (gels from ionic liquids (ILs)) toward selective detection of cyanide ions (CN-) in aqueous media through a metal-free and colorimetric approach. Three low molecular weight ionogels based on poly(alkyl ether) appended pyridinium ILs-containing ethyl (IL-1), butyl (IL-2), and hexyl (IL-3) substituents-were designed, synthesized, and used for cyanide sensing. All ILs formed unique thermoreversible gels in aqueous solutions of dimethylformamide, dimethylsulfoxide, ethanol, methanol, and dioxane. The self-assembled structure of the ionogels has been characterized by temperature-dependent 1H nuclear magnetic resonance, powder X-ray diffraction, scanning electron microscopy, atomic force microscopy, and rheology. The as-synthesized ionogels exhibited a rapid color change from yellow to saffron upon interaction with CN- ions (0.1 equiv). The remarkable features of this detection are that (a) the gel color was changed without losing the physical structural integrity; (b) the color change is reversible in the presence of a proton source, assuring the reusability of the material; and (c) the color change can be identified by the naked eye. The mechanism of the sensing has been investigated using 1H nuclear magnetic resonance titration experiments. All the ionogels showed a CN- response at micromolar range in the solution media and at 0.1 equiv to the gelator concentration in the gel medium. Results taken together suggest that as-prepared gels are useful for developing environmentally friendly portable kits for testing CN- in aqueous samples with a response time in seconds. Copyright © 2020 American Chemical Society.
About the journal
JournalACS Sustainable Chemistry and Engineering
PublisherACS Publications
Open AccessNo