Synthesis of a Single Benzene-Based Fluorophore for Selective Recognition of Al Ions

Abstract

Though 2,5-dihydroxyterephthalic acid (DHT) is composed of a single benzene molecule, it is blue-emissive in common organic solvents and in the solid state. Like most organic fluorophores, DHT is not soluble in water, which limits its versatile use in metal ion detection in an aqueous medium. To improve the water solubility of DHT and its use as a molecular sensor in aqueous solutions, its deprotonated form, DHT-K, was synthesized through the simple one-pot reaction of DHT with KOH. Compared with DHT, DHT-K was highly soluble in water and emitted yellow fluorescence in the solution and the solid. In addition, DHT-K showed high selectivity for Al ions, exhibiting fluorescence wavelength changes from 540 to 495 nm depending on the Al ion concentration. A linear relationship between the fluorescence intensity of DHT-K and Al ion concentration was established ranging from 18.96 to 247 μM with a detection limit of 1.84 µM. The binding stoichiometry between DHT-K and Al ions was determined by Job’s plot and found to be 1:2. Upon exposure to Al ions, DHT-K showed significant changes in fluorescence color and emission wavelength, whereas no fluorescence changes were observed by the addition of various metal ions such as Zn2+, Mg2+, Ca2+, Cu2+, Fe3+, and Co2+. Thus, DHT-K can be applied as a fluorescent sensor that can selectively detect Al ions in aqueous solutions.

Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5-(tert-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5-tBHI)

“…Organic emitters, based on a single benzene scaffold, have been explored extensively because of their trouble-free syntheses, low cost, and unique photophysical properties like solid-state emission, high quantum yield, and specific wave guidance for optoelectrical applications. − Commonly, tunable emission is the key factor since it empowers the performance of the emitter in optoelectronic applications by easily modulating the molecular composition, phase, and packing arrangements. However, the development of a single benzene-based emitter (SBBE), which could have color-tunable emission responses against external factors like optical output, temperature, pressure, electrical current, etc., is still challenging, as evident from only a few reported studies .…”