Lower Rim-Modified Calix[4]arene–Bentonite Hybrid System as a Green, Reversible, and Selective Colorimetric Sensor for Hg²⁺ Recognition

Abstract

A new quinaldine-functionalized calix [4]arene receptor (QHQC) was synthesized, characterized, and analyzed for its selective sensing properties toward Hg 2+ ions, and the binding event with characteristic color change can be followed by the naked eye. The sensing process is reversible, and the detection limit for Hg 2+ ions is 2.95 × 10 −6 M. A colorimetric solid state Hg 2+ sensor was fabricated by intercalating this receptor molecule into the bentonite galleries via the ionexchange method. This organic−inorganic hybrid sensor shows properties analogous to the receptor molecule and effectively detects Hg 2+ ions rapidly with visual color change. The solid state Hg 2+ sensor is economically affordable, environmentally benign, portable, reversible, and reusable.

Sustainable and safer nanoclay composites for multifaceted applications

“…The detection of mercury ions using low-cost, efficient, and highly stable sensors is of high priority due to the adverse effect of mercury on human health and the environment. Maya et al 226 prepared an environmentally friendly and reusable colorimetric solid-state sensor for detecting Hg 2+ ions using Na-bentonite (Na-Ben) nanoclay and a new synthetic quinaldine-functionalized calix [4]arene receptor (QHQC). Bentonite clays are able to expand their layers to incorporate organic molecules, thereby improving the overall properties of the hybrid structure in terms of mechanical, chemical, and thermal stability.…”

Development of Nitrobenzoxadiazole-Appended Calix[4]arene Conjugate (L) for Selective Sensing of Trivalent Cr3+, Fe3+, and Al3+ Ions in Solution and in the Solid State and Imaging MCF7 cells by {L + Al3+}

“…Among the fluorescent sensors, a “ turn-on ” response is more preferred over the “ turn-off ” because the turn-off results in fluorescence quenching, and the quenching is in turn influenced by a variety of processes. It has been demonstrated in the literature by our group − and others − that the calix[4]­arene platform provides an excellent scaffold for modifying these ions using ion binding groups and fluorophoric moieties. Connecting the 1,3-arms derivatized with appropriate binding centers at the lower rim of calix[4]­arene would provide a cyclic and preformed binding core.…”

Super Hydrophilic Semi-IPN Fluorescent Poly(N-(2-hydroxyethyl)acrylamide) Hydrogel for Ultrafast, Selective, and Long-Term Effective Mercury(II) Detection in a Bacteria-Laden System

“…Mercury ion pollution is a significant environmental issue affecting millions of people all over the world. , According to recent reports, Hg­(II) ion accumulates in the vital tissues and animals organs, which can cause a variety of diseases. − Actually, Hg­(II) ion entering the body through various means not only hinders the normal metabolism of cells but also causes neurotoxicity and renal toxicity-based multisystem damage of human body. Therefore, seeking effective methods for visual or real-time detection of mercury ions is becoming much more important. − However, most of these studies are primarily based on solution phases.…”