Two Colorimetric and Fluorescent Dual‐Channel Chemosensors for the Selective Detection of pH in Aqueous Solutions

Abstract

Fluorescent probe – which can detect metal ions, pH, and other analytical species through spectroscopic approaches – have recently attracted significant research attention in the fields of analytical and biological chemistry. For this study, two novel colorimetric and fluorescent probes, named RP1 and RP2, were designed and synthesized. Their structural confirmations were then achieved through elemental analysis, FT‐IR, NMR (1H and 13C) spectroscopies, and tandem MS spectrometry. To gain full understanding of the photophysical properties and chemosensory performances of these two dyes, both the UV‐Vis absorption and fluorescence titration experiments were carefully performed in aqueous media. Notably, upon treatment of RP1 and RP2 in solutions with each competitive metal ion, neither increases in absorption and fluorescence spectra above 400 nm nor any changes in color were observed. However, at lower pH (i. e.,<7.0), those two sensors exhibited a drastic change in color from colorless to pink, followed by broadened absorption bands. As expected, upon excitation at 510 nm, a strong enhancement of the fluorescence emissions was obtained. By conducting 1H NMR and optical titrations, the spirolactam‐ring opening reaction of these receptors, induced by H+ ions at lower pH, was approved. The results demonstrate that the fluorescent dyes RP1 and RP2 can be effectively used as reversible pH‐responsive chromogenic and fluorogenic “Off‐On” switches in real samples.

A Highly Water-Soluble and Solid State Emissive 1,8-Naphthalimide as a Fluorescent PET Probe for Determination of pHs, Acid/Base Vapors, and Water Content in Organic Solvents

“…Consequently, major attention has been focused on the design and synthesis of fluorescent probes for a variety of analytes [12][13][14][15]. The used approaches were based on intramolecular charge transfer (ICT), photoinduced electron transfer (PET), twisted intramolecular charge transfer (TICT), fluorescence resonance energy transfer (FRET), excited-state intramolecular proton transfer (ESIPT), and aggregation-induced emission [16][17][18][19][20][21][22][23][24]. Notably, the PET using the "fluorophore-spacer-receptor" format was recognized as the most popular platform for the design of fluorescence chemosensing probes [25][26][27][28].…”

A Novel Fluorescent Probe for Determination of pH and Viscosity Based on a Highly Water-Soluble 1,8-Naphthalimide Rotor

“…The compound presented in Scheme 1 under study is a TICT (twisted intramolecular charge transfer) molecular rotor with fluorescence-sensing properties focusing on pH and viscosity. The rapid analysis of pH and viscosity plays a critical role in large areas of industrial production, food processing, and environmental monitoring [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]; also, the abnormal values of intracellular pH and viscosity could be associated with several diseases, such as atherosclerosis, Alzheimer’s disease, diabetes, and cancer [ 38 , 39 , 40 , 41 , 42 ]; hence, the synthesis of fluorescent probes for both pH and viscosity currently could be of significant importance. In order to simultaneously achieve pH- and viscosity-switchable fluorescence, the novel probe was based on a TICT molecular rotor platform.…”

Synthesis and investigation of 1,8-naphthalimide derivative with sensor activity

“…The measurement of pH is very important in biological, chemical and industrial fields. In recent years, the optical pH sensory technique based on the absorption or emission of certain organic compounds with structural diversity, has received increasing attention because it offers many advantages over the potentiometric method, such as fast response time and the absence of the otherwise requested reference electrode (Abu-Thabit et al, 2016;Martínez-Quiroz et al, 2016;Ozdemir, 2020;Qi et al, 2015;Ye et al, 2019;Wang et al, 2010).…”