Progressive aggregation-induced emission strategy for imaging of aluminum ions in cellular microenvironment

Construction of nanohybrid Tb@CDs/GSH-CuNCs as a ratiometric probe to detect phosphate anion based on aggregation-induced emission and FRET mechanism

The simple preparation of a nanohybrid of terbium-doped carbon dots/glutathione-capped copper nanoclusters (Tb@CDs/GSH-CuNCs) was for the first time developed for ratiometric detection of phosphate anion (Pi). Blue-emission of Tb@CDs can trigger non-luminescence of GSH-CuNCs for aggregation-induced emission (AIE) performance due to the strong reserved coordination capacity of Tb3+. Thus, Tb@CDs/GSH-CuNCs rapidly generated dual-emission signals at 630 nm and 545 nm by directly mixing the two individual materials via the AIE effect, alongside fluorescence resonance energy transfer (FRET) process. However, by the introduction of Pi, both AIE and FRET processes were blocked because of the stronger binding affinity of Tb3+ and Pi than that of Tb3+ and -COOH on Tb@CDs, thus realizing successful ratiometric detection of Pi. The linear concentration range was 0-16 μM, with the limit of detection (LOD) of 0.32 μM. The proposed method provided new ideas for designing nanohybrid of CDs and nanoclusters (MNCs) as ratiometric fluorescent probes for analytical applications.

Portable Smartphone Platform Based on Aggregation-Induced Enhanced Emission Carbon Dots for Ratiometric Quantitative Sensing of Fluoride Ions

The development of an instrument-free, on-site, real-time, sensitive, and visualized fluoride-ion (F^-) content rapid detection strategy is crucial to ensuring the health of the population. Smart microdevices that are portable, directly read, and easy to operate have recently attracted much attention. Herein, a ratiometric fluorescent probe (AA-CDs@[Ru(bpy)₃]²⁺)-based smartphone sensing platform was developed for the detection of F^-. The red fluorescent ruthenium bipyridine [Ru(bpy)₃]²⁺ molecule was chosen as the reference signal, and the carbon dots (AA-CDs) with Al³⁺ aggregation-induced enhanced emission (AIE) were designed as the response signal. The ratiometric probe fluorescence changed continuously from red to cyan in response to different concentrations of F^-, and the red-green-blue (RGB) channel values of the fluorescence image were extracted through the smartphone color recognition application (APP). There was a linear relationship between the blue-red (B/R) ratio and the F^- concentration, with a limit of detection (LOD) of 1.53 μM, far below the allowable content of F^- in drinking water prescribed by the World Health Organization. The F^- content was rapidly detected on-site with satisfactory repeatability and relative standard deviation using several water and toothpaste samples as the real sample. The platform features low cost, portability, easy operation, and good stability, selectivity, and repeatability, which provides a powerful tool for the visual quantitative detection of smartphone-based microsensing platforms possibly in the fields of environmental protection, diagnosis, and food safety assessment.

A simple AIE chemosensor based on diphenyl imidazole scaffold for 2,4,6-trinitrophenol detection and dye absorption

Fluorescent material exhibiting aggregation-induced emission (AIE) has demonstrated to be a facile and effective method to detect 2,4,6-trinitrophenol (TNP) due to its excellent features. In this study, a novel diphenyl imidazole-based fluorescent material (DINP) was successfully synthesized via a facile method. Fluorescence spectra showed that DINP had a typical AIE effect in DMSO/water solution, and the fluorescence emission was effectively quenched by TNP without being affected by other explosives. The Stern-Volmer quenching constant of 2.70 × 10⁵ M^-1 and detection limit of 7.2 × 10^-8 M demonstrated that the DINP aggregates could serve as potential chemosensor for TNP detection. The mechanism behind the quenching of fluorescence could be ascribed to the formation of ground state complex. In addition, fluorescent test strips and TLC plate prepared with the aggregates provided an easy and low cost method for TNP detection in the aqueous solution. Especially, DINP was applied to quantitatively detect the content of TNP in real water samples. Furthermore, the aggregates exhibited good selective adsorptive performance to rhodamine B dye in aqueous solution with high adsorption efficiency of 98 % in a few minutes.

Insights into AIE materials: A focus on biomedical applications of fluorescence

Aggregation-induced emission (AIE) molecules have garnered considerable interest since its first appearance in 2001. Recent studies on AIE materials in biological and medical areas have demonstrated that they show their promise as biomaterials for bioimaging and other biomedical applications. Benefiting from significant advantages of their high sensitivity, excellent photostability, and good biocompatibility, AIE-based materials provide dramatically improved analytical capacities for in vivo detection and demonstration of vital biological processes. Herein, we introduce the development history of AIE molecules and recent progress in areas of biotesting and bioimaging. Additionally, this review also offers an outlook for the potential applications of versatile AIE materials for tracing and treating pathological tissues, including overcoming challenges and feasible solutions.

Ratiometric fluorescence determination of chlortetracycline based on the aggregation of copper nanoclusters triggered by aluminum ion

The aggregation-induced emission (AIE) characteristic of copper nanoclusters (CuNC) was for the first time used to construct a ratiometric fluorescence probe (CuNC-Al³⁺) for detection of chlortetracycline (CTC). Aluminum ion (Al³⁺) can aggregate free CuNC and make it emit a bright and stable red fluorescence. A slight excess of Al³⁺ in CuNC-Al³⁺ solution can form a CTC-Al³⁺ complex to limit the conformational rotation of CTC molecule and enhance CTC fluorescence. So, the red fluorescence of CuNC-Al³⁺ probe and the enhanced CTC fluorescence are used as a reference signal and a response signal to detect CTC, respectively. The method developed shows a good linear relationship between the CTC concentration and the fluorescence intensity ratio (I₄₉₅/I₅₇₅) in the range 0.1-3.0 µM, and the detection limit is 25.3 nM (S/N = 3). In addition, the fluorescent color of CuNC-Al³⁺ probe changes from red to yellow-green as the concentration of CTC increases. Based on this observation, a fluorescent test paper has also been fabricated. Schematic illustration of Al³⁺ inducing CuNC to produce AIE performance and detecting CTC.