Coumarin derivative-functionalized nanoporous silica as an on-off fluorescent sensor for detecting Fe³⁺ and Hg²⁺...

A highly efficient fluorescent sensor (S-DAC) was easily created by functionalizing the SBA-15 surface with N-(2-Aminoethyl)-3-Aminopropyltrimethoxysilane followed by the covalent attachment of 7-diethylamino 3-acetyl coumarin (DAC). This chemosensor (S-DAC) demonstrates selective and sensitive recognition of Fe³⁺ and Hg²⁺ in water-based solutions, with detection limits of 0.28 × 10^-9 M and 0.2 × 10^-9 M for Hg²⁺ and Fe³⁺, respectively. The sensor's fluorescence characteristics were examined in the presence of various metal ions, revealing a decrease in fluorescence intensity upon adding Fe³⁺ or Hg²⁺ ions at an emission wavelength of 400 nm. This sensor was also able to detect ferric and mercury ions in spinach and tuna fish. The quenching mechanism of S-DAC was investigated using UV-vis spectroscopy, which confirmed a static-type mechanism for fluorescence quenching. Moreovre, the decrease in fluorescence intensity caused by mercury and ferric ions can be reversed using trisodium citrate dihydrate and EDTA as masking agents, respectively. As a result, a circuit logic gate was designed using Hg²⁺, Fe³⁺, trisodium citrate dihydrate, and EDTA as inputs and the quenched fluorescence emission as the output.