Supersensitive Detection of Anions in Pure Organic and Aqueous Media by Amino Acid Conjugated Ellman’s Reagent

Abstract

The last few decades witnessed a remarkable advancement in the field of molecular anion receptors. A variety of anion binding motifs have been discovered, and large number of designer molecular anion receptors with high selectivity are being reported. However, anion detection in an aqueous medium is still a formidable challenge as evident from only a miniscule of synthetic systems available in the literature. We, herein, report 5,5′-dithio-bis­(2-nitrobenzoic acid) (Ellman’s reagent) appended with amino acids as supersensitive anion sensors that can detect F– and H2PO4 – ions in both aqueous as well as organic media. Interestingly, the sensors showed a dual response to anions, viz., chromogenic response in organic medium and electrochemical response in aqueous solutions. Various spectroscopic techniques such as UV–vis and 1H NMR are used to investigate the binding studies in acetonitrile, whereas electrochemical methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are employed to explore the anion binding in water. The host–guest complex stoichiometry and binding constants are calculated using the BindFit software. The geometry of host–guest complex has been optimized by the density functional theory (DFT) method. These molecules are versatile sensors since these function in both water and acetonitrile with extremely low limit of detection (LOD) up to 0.07 fM and limit of quantification (LOQ) up to 0.23 fM. To our knowledge, the present system is the first example of a sensor that can detect the lowest concentration of anions in water quantitatively. The minimalistic design strategy presented here opens up the innumerable possibilities for designing dual anion sensors in a one fell swoop.

In Situ Ni(II) Complexation Induced Deprotonation of Bis-Thiourea-Based Tweezers in DMSO–Water Medium: An Approach toward Recognition of Fluoride Ions in Water with Organic Probe Molecules

“…The peaks at E pa = −0.57 V and E pc = −0.81 V represent the redox couples Ni­(II)/Ni­(I) and Ni­(I)/Ni­(II), respectively, whereas the peaks at E pa = 0.41 V and E pc = −1.61 V indicate the redox couples Ni­(III)/Ni­(I) and Ni­(I)/Ni­(III), respectively. , This observation suggested the in situ Ni­(II) complexation of the conjugate base of S1 , which is formed upon the deprotonation reaction with fluoride. However, S2 did not show any significant response for aqueous sodium fluoride even in the presence of Ni­(II) ions. , …”

“…However, S2 did not show any significant response for aqueous sodium fluoride even in the presence of Ni(II) ions. 55,56 Furthermore, the electrochemical response of S1 upon incremental addition of aqueous fluoride ions in the presence 57,58 The study also revealed that the acetate anion led to some responses similar to that of the fluoride anion but with lower intensity. However, comparatively lower basic anions like Cl − , I − , HSO 4 − , and H 2 PO 4 − did not show any significant effect on the DPV pattern (Figure S47).…”

“…However, S2 did not show any significant response for aqueous sodium fluoride even in the presence of Ni(II) ions. 55 , 56 …”

Design of “turn-off” luminescent Ln-MOFs for sensitive detection of cyanide anions

“…The sensing and recognition of anions have garnered an increasing level of attention in light of the essential roles they play. 1,2 Cyanide specifically refers to compounds containing a cyano group (CN − ), which encompasses hydrogen cyanide, sodium cyanide, potassium cyanide, and ammonium cyanide. 3,4 Most inorganic cyanides are extremely toxic.…”

Designer Peptide‐PVDF Composite Films for High‐Performance Energy Harvesting

“…[21] Recently, among various bio-inspired materials, peptides and pseudopeptides have drawn significant attention due to their biocompatibility, molecular recognition (e.g., H-bonding and electrostatic interactions), and electronic properties. [18,[22][23][24][25][26][27] Nguyen et al demonstrated excellent piezoelectric properties of self-assembled peptide microrods, which could generate opencircuit output voltages up to ≈1.4 V. [22] Lee et al reported aligned peptide nanorods with improved piezoelectric properties and output voltages up to ≈2.8 V. [28] Hence, owing to their biocompatibility, intrinsic self-assembling ability, and piezoelectric properties, peptide-based materials are efficient candidates to be used as fillers in the PVDF matrix.…”