Ionogels as Precursors To Prepare ZnS Nanoparticles for Colorimetric Sensing of Sulfide Ions

Abstract

In this study, novel supramolecular ionogels with ultrahigh efficient gelation and robust mechanical properties were prepared by mixing 4′-para-phenylcarboxyl-2,2′:6′,2″-terpyridine (PPCT) and zinc ions (Zn2+) in ethylammonium nitrate (EAN). The microstructure of the ionogels was determined to be three-dimensional networks of fibrous aggregates. X-ray diffraction and Fourier-transform infrared spectroscopy measurements demonstrated that ionogel formation involve the following steps: the terpyridine rings of PPCT form an assembled unit via π–π interaction, the unit further aggregates to form fibers using Zn2+ via hydrogen bonding and Zn2+ coordination, and the fibers stretch and intertwine to form a cross-linked network to immobilize EAN by solvophobic interactions, electrostatic interactions, and van der Waals forces. Rheological results revealed that ionogels exhibited high mechanical strength with an elastic modulus and a yield stress of 50 000 and 900 Pa, respectively. The ionogels of PPCT and Zn2+ mixtures served as the precursors to produce zinc sulfide (ZnS) nanoparticles (NPs). The uniform 10 nm-sized ZnS exhibited higher surface area and higher peroxidase-like activity that can be used for sulfide ion (S2–) colorimetric sensing to detect S2– at a lower limit detection of 5.27 nmol·L–1. Furthermore, an innovative, green, and convenient approach has been developed to produce ZnS NPs, which are an environmentally friendly and sustainable candidate material in bioengineering technology, environmental protection, and food industries.

Fluorescent Hydrogel Producing ZnO for Colorimetric Detection of Glutathione and Cysteine

“…Pincer terpyridine contained a larger π-conjugated system, abundant coordination, and high binding affinity toward many metal ions, which should be an excellent LMWG gelator for constructing gels. [35,21] Therefore, the derivative of terpyridine, 4′-(4-n-butylimidazole)-p-benzyl-2,2′:6′2″-terpyridine (C 4 -Ter), was synthesized and the chemical molecular structure was shown in Figure 1a. Hydrogels were produced by the mixing of C 4 -Ter and Zn 2+ in water, and the gel phase region was confirmed by the inverted tube observation (Figure 1b).…”

“…In addition, they supply guidelines for gels sustainable application. [21,40] Stress sweep and dynamic frequency sweep measurements were conducted to quantitatively evaluate the viscoelasticity and mechanical strength of hydrogels by determining the elastic modulus (G′), viscous modulus (G′′), and yield stress (τ*). [41,42] In stress sweep (Figure 3), the value of G′ for gels depends on the shear stress (τ) over the entire investigated region, which is the typical character of soft materials.…”

“…Thus, it is very urgent to design LMWGs with functional groups to develop hydrogels with prominent mechanical strength and stability for functional applications. [21][22][23][24] Among the 20 amino acids used as building blocks for proteins, the thiolcontaining amino acids, acting as antioxidants and antidotes, participate in biological activities and metabolic processes, which can retain the cellular defense against xenobiotics, gene regulation, and free radicals signal transduction. [25,26] As the only thiol-containing amino acids, cysteine (Cys) contributes biologically in human body by providing a mode for intermolecular cross-linking of proteins using the disulfide bonding to support the secondary structures and functions.…”