Isatin as a simple, highly selective and sensitive colorimetric sensor for fluoride anion

Abstract

Herein, we report the fluoride anion sensing properties of a commercially available and inexpensive organic compound, isatin, which is found to be a highly selective and sensitive sensor. In naked-eye experiments, by addition of fluoride anions, isatin shows a dramatic color change from pale yellow to violet at room temperature, while the addition of other anions, i.e. $\mathrm{Cl}^-,$$\mathrm{Br}^-,\mathrm I^-,\mathrm{ClO}_4^-,{\mathrm H}_2\mathrm{PO}_4^-\,\mathrm{and}\,\mathrm{PF}_6^-,$did not induce any colour change. Additionally, recognition and titration studies have also been done through UV/Vis spectroscopy. Isatin displayed a new absorption band at 533 nm after the addition of fluoride anions, which is presumably due to acid-base interaction between isatin and fluoride anions, while other anions did not trigger noticeable spectral changes. The detection limit was observed to be 0.367 ppm. DFT calculations were also performed to further explain the behavior of receptor 1 towards the Fˉ anion. Owing to high sensitivity and selectivity, isatin can be useful in the detection of biologically or environmentally important fluoride anions at very low concentration.

Plasmonic Superstructure Arrays Fabricated by Laser Near-Field Reduction for Wide-Range SERS Analysis of Fluorescent Materials

“…The Raman intensity increases with the amount of PFOA due to the increased amount of ion-pairs. The lower detection limit of PFOA can be defined as 3.3 σ/k, where σ is the standard error of the y-intercept in the regression line and k is the slope according to IUPAC definition [ 29 , 30 ]. Since this definition relies on a linear relationship, the lower detection limit is calculated in the lower concentration range of 0–100 ppb, which is 10.52 ppb.…”

Azurite blue in the Qing dynasty

“…Fabrics dyed with rhubarb root reflect red and yellow colors, which result in a reddish blue hue. The absorption spectra from rhubarb root and isatin can be distinguished easily 13,14 . Water extracted from rhubarb root absorbs most of the light above 300 nm; however, that from isatin absorbs light from 320 nm to 360 nm and light above 500 nm.…”

Recent advances in isatin‐based chemosensors: A comprehensive review

“…Due to its remarkable sensitivity and selectivity, isatin proved to be a valuable asset for the detection of biologically and environmentally relevant fluoride anions, even at exceedingly low concentrations. This study highlights the potential of isatin as an efficient and cost‐effective sensor for fluoride ions, with applications spanning the fields of biology and environmental monitoring [43].…”