ESIPT-Induced Carbazole-Based AIEE Material for Nanomolar Detection of Cu2+ and CN- Ions: A Molecular Keypad Security Device

Aggregation-induced Emission Properties of Triphenylamine Chalcone Compounds

Two triphenylamine chalcone derivatives 1 and 2 were synthesized through the Vilsmeier-Haack reaction and Claisen-Schmidt condensation reaction. Through ultraviolet absorption spectroscopy and fluorescence emission spectroscopy experiments, it was confirmed that these two compounds exhibited good aggregation-induced emission (AIE) behavior in ethanol/water mixtures. The solvent effect test showed with the increase of the orientation polarizability of the solvent, the Stokes shift in the solvent of compound 1 and compound 2 shows a linear change trend. Through solid state fluorescence test and universal density function theory (DFT), the existence of π-π stacking interaction in the solid state of the compound has been studied, resulting in weak fluorescence emission. pH has no effect on the fluorescence intensity of the aggregate state of excited state intramolecular proton transfer (ESIPT) molecules in an acidic environment, but greatly weakens its fluorescence intensity in an alkaline environment. Cyclic voltammetry (CV) test shows that compound 1 was more prone to oxidation reaction than compound 2. The results of thermal stability test show that the thermal stability of compound 1 was better than that of compound 2, indicating that triphenylamine chalcone derivatives can improve the thermal stability of compounds by increasing the number of branches.

A C3-symmetrical tripodal acylhydrazone organogelator for the selective recognition of cyanide ions in the gel and solution phases: practical applications in food samples

The method of formation of low-molecular-weight organogelators via modifications in the substituents has been demonstrated. The organogelator formed can selectively sense cyanide ions in the gel and solution phases. Interaction of cyanide with acylhydrazone was noticeably visible to the "naked eye" and was proved using 1H NMR titrations. Notably, the ligand has been successfully explored for the recognition of cyanide ions in food samples. Additionally, low-cost cotton swabs coated with the organogelator showed rapid, on-site recognition of cyanide ions. The structure-property relationship discovered in the given study provides insight into the development of novel, cost-effective multifunctional materials.

Hydroxyl phenyl imino modified phenanthro[9,10-d] imidazole: An AIEE-active sensor for determination of Cu2+ in water samples and subsequent "turn-on" recognition of Cr3+ with logic gates

A 2-hydroxyl phenyl imino modified phenanthro[9,10-d]imidazole probe (PPIP) was synthesized and its aggregation-induced emission enhancement (AIEE) phenomenon in aqueous medium was characterized by the Tyndall phenomena, morphologies of scanning electron microphotograph (SEM) as well as the enhanced fluorescence intensities. The AIEE-active PPIP in aggregated states exhibited a sensitive detection for Cu²⁺ along with the elimination of fluorescence intensity; subsequently, in situPPIP-Cu²⁺ complex showed selective fluorescence "turn-on" for Cr³⁺, providing a potential platform for tandem recognition of Cu²⁺ and Cr³⁺. The 1:1 M ratio between PPIP and Cu²⁺ was confirmed by Job's plot, ¹H NMR spectra, mass spectra and density functional theory (DFT) calculations. The detection limits for Cu²⁺ and Cr³⁺ were 4.127 × 10^-2 μM and 9.404 × 10^-1 μM, respectively. Moreover, this successive recognition could be utilized to construct the molecular logic gates by the fluorescence changes. In addition, PPIP was successfully employed for quantitative detecting Cu²⁺ in real water samples with satisfactory results.

Aggregation induced emission enhancement (AIEE) of tripodal pyrazole derivatives for sensing of nitroaromatics and vapor phase detection of picric acid

Organosoluble tris-pyrazole compounds aggregate in organic/aqueous solvent mixtures, showing aggregation-induced emission enhancement (AIEE), the latter being quenched by picric acid.

Fluorescence light-up detection of cyanide in water based on cyclization reaction followed by ESIPT and AIEE

Schiff base 1 (2,4-di-tert-butyl-6-((2-hydroxyphenyl-imino)-methyl)phenol) containing two hydroxyl groups could undergo an oxidative cyclization reaction and then generate hydroxyphenylbenzoxazole (HBO) 2 when CN^- was present as a catalyst. The multistep cyclization reaction was proved by spectroscopy, ¹H NMR, ¹³C NMR and mass spectra. C[double bond, length as m-dash]N isomerization is the predominant decay process of the excited states, so sensor 1 is weakly emissive in solution at ambient temperature. When 1 reacts with CN^-, the emission is remarkably enhanced, where 1 is converted to 2. The cyclization product HBO 2 displays bright green luminescence in micellar due to the ESIPT (excited-state intramolecular proton transfer) as well as AIEE (aggregation-induced emission enhancement) effect. The detection limit is 5.92 × 10^-7 M, lower than the WHO guideline of CN^- in drinking water (1.9 μM). The selective and competitive experiments reveal that sensor 1 shows high sensing selectivity and sensitivity for CN^- over other anions. Test papers containing absorbed 1 were prepared and applied for practical application of cyanide detection.