An AIE and ESIPT active Schiff base as colorimetric probe of Fe3+ and turn-on fluorescent probe of Al3+: Experimental and theoretical studies

An HDBB-based fluorescent probe for the sensitive detection of human serum albumin

The detection of human serum albumin (HSA) in bodily fluids is of great significance in the biomedical area because HSA in bodily fluids is commonly used as a biomarker for the early diagnosis of diseases. To detect HSA, we employed HDBB, 4,4'-(hydrazine-1,2-diylidene bis(methanylylidene)) bis(3-hydroxybenzoic acid), as a fluorescent probe with a large Stokes shift. HDBB had obvious excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) features. We elucidated the ESIPT characteristics of HDBB through the DFT approach. We also performed a molecular docking simulation between HDBB and HSA, showing that HDBB primarily bonded to HSA via hydrophobic force and hydrogen bonds. The FL intensities of HDBB with HSA concentrations had a linear range of 0.01-0.2 mg mL-1 (R2 = 0.9995), and the LOD was 1.104 μg mL-1. We also used the probe to detect HSA in urine, with spiked recoveries of 98.10-105.33%. Given its high selectivity and feasible synthesis, HDBB has potential applications in detecting HSA in real biological systems.

A novel AIE fluorescent probe for the monitoring of aluminum ions in living cells and zebrafish

A novel fluorescent probe BTD with aggregation induced emission (AIE) characteristics for the monitoring of Al³⁺ was developed. This fluorescent probe could be used to detect Al³⁺ in aqueous solution under mild conditions, along with high sensitivity and high selectivity. The detection limit of the probe BTD for Al³⁺ is as low as 3.25 nM, which is below the WHO recommendation concentration (7.41 μM) for drinking water. Furthermore, this probe was successfully applied to the sensing of Al³⁺ in living cells and zebrafish.

AIE-based fluorescent sensors for low concentration toxic ion detection in water

Ions, including anions and heavy metals, are extremely toxic and easily accumulate in the human body, threatening the health of humans and even causing human death at low concentrations. It is therefore necessary to detect these toxic ions in low concentrations in water. Fluorescent sensing is a good method for detecting these ions, but some conventional dyes often exhibit an aggregation caused quench (ACQ) effect in their solid state, limiting their large-scale application. Fluorescent probes based on aggregation-induced emission (AIE) properties have received significant attention due to their high fluorescence quantum yields in their nano aggragated states, easy fabrication, use of moderate conditions, and selevtive recognization of organic/inorganic compounds in water with obvious changes in fluorescence. We surmarize the recent advances of AIE-based sensors for low concentration toxic ion detection in water. The detection probes can be divided into three categories: chemical reaction types, chemical interaction types and physical interaction types. Chemical reaction types utilize nucleophilic addition and coordination reaction, while chemical interaction types rely on hydrogen bonding and anion-π interactions. The physical interaction types are composed of electrostatic attractions. We finally comment on the challenges and outlook of AIE-active sensors.

Adsorption Promoted Aggregation-Induced Emission Showing Strong Dye Lateral Interactions

Aggregation-induced emission (AIE) is a powerful method to produce fluorescence for a diverse range of applications. While most previous work induced aggregation by change of solvent, ionic strength, pH, or self-assembly, we herein explored adsorption-induced aggregation using 4,4'-(hydrazine-1,2-diylidene bis(methanylylidene)) bis(3-hydroxybenzoic acid) (HDBB) as an AIE luminogen. HDBB is known to aggregate with AIE at low pH but not at neutral pH, and its aggregation facilitates excited state intramolecular proton transfer for enhanced emission. Using a nonquenching nanomaterial, Y₂O₃ nanoparticles, HDBB showed sevenfold fluorescence increase at pH 7.0. Fluorescence lifetime showed that HDBB was in the aggregated state in the presence of Y₂O₃. For comparison, a fluorescent porphyrin compound showed that adsorption caused quenching after mixing with Y₂O₃, whereas other dyes such as fluorescein, calcein, and rhodamine B failed to be adsorbed by Y₂O₃. Adsorption did not follow a Langmuir isotherm, but it showed strong lateral HDBB interactions because adsorption was only achieved with a high concentration of HDBB. Adsorption was inhibited by salt and by phosphate, indicating the importance of electrostatic and metal-binding interactions. Comparisons were made with other nanomaterials, where graphene oxide and CeO₂ quenched HDBB and a cationic liposome also enhanced its emission, although with a less red-shifted peak wavelength. This study provides a simple method to induce aggregation of an AIE dye and its aggregation in turn-enhanced adsorption.