N-hydroxypropyl substituted 4-hydroxynaphthalimide: Differentiation of solvents and discriminative determination of water in organic solvents

Study on the modulating effect of halogen atom substitution on the detection range of water content detection probes in organic solvents

Fluorescence probes based on the variations of aggregation state (Aggregation-Induced Emission (AIE) and Aggregation-Caused Quenching (ACQ)) have received widespread attention due to their simplicity, efficiency and intuitiveness. However, typical probes are highly sensitive to changes in polarity and slight variations in the external environment can cause a complete change in the aggregation state. With the aim of expanding the detection range of the molecular probe, this work adopts a different design strategy from adjusting the molecular backbone but regulates the fluorescence behavior of the Schiff base molecular backbone by introducing different halogen atoms. Systematic studies show that when chlorine serves as substitutional atoms (3,5-Cl Salen), the probe can achieve full-range detection of water content (0-100 vol%) in ethanol and DMF. To our knowledge, the 3,5-Cl Salen represents the best water content probe in organic molecules. Experimental and theoretical studies have shown that the adjustment of halogen atoms can linearly change the charge distribution on the benzene ring and precisely control the strength of intermolecular interactions. At the same time, we developed a fluorescent filter paper based on 3,5-Cl Salen and used smartphones for rapid, sensitive and precise on-site measurement of water content in organic solvents.

A 1,8-naphthimide-based Fluorescent Probe for Analyzing DMF/H2O Composition

A novel 1,8-naphthalimide fluorescent probe (BNAS) containing 2-thiopheneethylamine moiety was designed and synthesized for analyzing the composition of N,N-dimethylformamide (DMF)/deionized water (H2O) mixtures. With the increase of DMF content, the fluorescence of the system was enhanced from dark to bright yellow-green. Taking 15% (volume) DMF content as the dividing point, the fluorescence intensity of the system at 535 nm showed two good linear relationships with the DMF content 1-15% and 15-99%, based on which the composition of the DMF/H2O mixtures with a volume ratio of 1/99-99/1 could be quickly and efficiently analyzed with high selectivity and sensitivity. BNAS can be applied in real sample assay and further be loaded onto filter paper to make a portable sensor. The mechanism of BNAS response to DMF/H2O composition was also explored.

Fluorescence ''turn-on'' probe for the selective detection of water in organic solvents based on functionalized mesoporous silica

A fluorescence ''turn-on'' probe, namely, TTA-SBA-15, for the selective detection of water (H₂O) was designed by grafting terthiophene fluorophore onto ethylenediamine functionalized mesoporous SBA-15 silica. The maximum fluorescence emission peak of TTA-SBA-15 ranged from 462 nm (toluene) to 525 nm (methanol) in various organic solvents. No fluorescence was observed in H₂O due to the donor-excited photoinduced electron transfer mechanism, in which terthiophene acted as the donor and the amino group acted as the acceptor. Upon adding trace amounts of H₂O into the TTA-SBA-15 suspensions dispersed in various organic solvents, TTA-SBA-15 was successfully applied as a ''turn-on'' fluorescent probe for the quantitative determination of trace H₂O in organic solvents with high sensitivity and low detection limit. To demonstrate the selective detection mechanism of TTA-SBA-15 for H₂O, the fluorescent spectra of two control materials (TT-SBA-15 and PyA-SBA-15) were also investigated in H₂O and various organic solvents. The experimental results indicated that the terthiophene fluorophore and amine functional group on TTA-SBA-15 contributed to the H₂O selectivity, highlighting the structure-activity relationships in developing organic functionalized mesoporous silica for potential applications.

Highly Sensitive Water Detection Through Reversible Fluorescence Changes in a syn-Bimane Based Boronic Acid Derivative

Reported herein is a fluorometric and colorimetric sensor for the presence of trace amounts of water in organic solvents, using syn-bimane based boronate ester 1. This sensor responds to the presence of water with a highly sensitive turn-off fluorescence response, with detection limits as low as 0.018% water (v/v). Moreover, analogously high performance was observed when compound 1 was adsorbed on filter paper, with the paper-based sensor responding both to the presence of liquid water and to humid atmospheres. Reusability of the paper-based sensor up to 11 cycles was demonstrated, albeit with progressive decreases in the performance, and 1H NMR and mass spectrometry analyses were used to explain the observed, hydrolysis-based sensor response.