N-doped carbon dots for the determination of Al3+ and Fe3+ using aggregation-induced emission

New portable hydrogel sensors for Al3+ and Fe3+ detection were designed based on the aggregation-induced emission (AIE) and color change of N-doped carbon dots (N-CDs). N-CDs with yellow fluorescence were prepared by a one-pot hydrothermal method from 2,5-dihydroxyterephthalic acid and acrylamide. The fluorescence of N-CDs was enhanced by Al3+ about 20 times and quenched by Fe3+. It was interesting that although Fe3+ showed obvious quenching on the fluorescence of N-CDs it did not cause a noticeable change in the fluorescence of N-CDs + Al3+. The colorless solution of N-CDs appeared blue in the presence of Fe3+ without the influence of Al3+. Therefore, the turn-on fluorometry and colorimetry systems based on N-CDs were constructed for the simultaneous detection of Al3+ and Fe3+. Furthermore, the portable sensing of Al3+ and Fe3+ was realized with the assistance of hydrogel, filter paper, cellulose acetate, and cellulose nitrate film. The proposed approach was successfully applied to the detection of Al3+ and Fe3+ in food samples and cell imaging.

Novel selective "on-off" fluorescence sensor based on julolidine hydrazone-Al3+ complex for Cu2+ ion: DFT study

A hydrazone (T1) was synthesized by reacting 8-hydroxyjulolidine-9-carboxaldehyde with 2-furoic hydrazide and then modified with Al³⁺ ion to form a novel hydrazone Al³⁺ complex (T1-Al³⁺) in an aqueous solution (8% propylene glycol in 10 mM HEPES pH 5.5). The T1-Al³⁺ complex was studied as a Cu²⁺ selective sensor due to its highly efficient capacibility of paramagnetic quenching. The results showed that the T1-Al³⁺ complexed sensor possesses remarkable sensitivity and selectivity for Cu²⁺ ion in 8% propylene glycol in 10 mM HEPES pH 5.5 as compared with other tested analytes. Notably, this sensor has a broad linear detection range of 10-110 µM for Cu²⁺ ion and a detection limit level of 0.62 µM, which is lower than the Cu²⁺ concentration threshold in drinking water designated by the United States Environmental Protection Agency (EPA). Additionally, it was detectable for the presence of Cu²⁺ ion in mineral water and tap water samples. The selectivity of T1-Al³⁺ complexed sensor with Cu²⁺ ion could be explained by the basis of computation with Gaussian software complied with the basis sets of B3LYP/6-31 G(d,p)/LANL2DZ. Furthermore, only T1 exhibited anticancer efficacy against HeLa and U251 cells with MTT assay.

Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

We report herein the design and mechanochemical synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), an orange aggregation-induced emission (AIE), for the selective detection of H2O2 in a turn-on manner.

A new 7-diethylamino-4-hydroxycoumarin based reversible colorimetric/fluorometric probe for sequential detection of Al3+/PPi and its potential use in biodetection and bioimaging applications

A new 7-diethylamino-4-hydroxycoumarin appended acylhydrazone probe was prepared and utilized for the sequential detection of Al³⁺/PPi in a reversible off–on–off emissive manner. The various practical applications of the probe were established.

Biotinylated and fluorophore-incorporated polymeric mixed micelles for tumor cell-specific turn-on fluorescence imaging of Al3

Excessive amounts of Al3+ in the human body can cause adverse effects on immune function and induce several neurodegenerative disorders. So far, most of the reported fluorescent probes for Al3+ present some common drawbacks, such as low sensitivity and poor water solubility. In addition, a number of traditional fluorescent probes failed to image Al3+ in tumor cells due to the lack of tumor cell targeting capacity and cell penetrating abilities. To overcome these shortcomings, we constructed tumor-targeting fluorescent mixed nano-micelles (mPEG-Dye-Biotin) with an average particle size of 21 nm from an amphiphilic polymer containing a Schiff-base fluorescent unit (mPEG-Dye) and another amphiphilic polymer containing a tumor cell recognition ligand (DSPE-PEG-Biotin), through the co-self-assembly of both amphiphilic polymers in water using the film rehydration method. The as-prepared nanoprobe showed a highly sensitive and selective turn-on fluorescence response to Al3+ in aqueous solution with a low detection limit. MTT assay revealed the negligible cytotoxicity of the mPEG-Dye-Biotin nanoprobe to both HeLa cells and COS-7 cells, indicating the safety of mPEG-Dye-Biotin for biological applications. More importantly, the biotinylated nanoprobe showed better ability to enter biotin receptor-positive HeLa cells than that of the non-biotinylated micelle mPEG-Dye, which made it more suitable for imaging Al3+ in biotin receptor-positive tumor cells. This work provides a simple and general strategy to design a highly sensitive and tumor cell-specific metal ion nanoprobe, which can not only be applied in Al3+ imaging, but can also be extended to other ions or biomolecules by changing the incorporated fluorescent unit in the amphiphilic polymer.

A 4,5-quinolimide-based fluorescent sensor for sequential detection of Cu2+ and cysteine in water and living cells with application in a memorized device

In this study, a new 4,5-quinolimide-based fluorescent sensor BNC was synthesized and characterized. BNC showed single selectivity for Cu²⁺via the "turn-off" fluorescence among various common metal ions. After forming a 1:1 stoichiometric complex with Cu²⁺, the detection limit (LOD) of BNC for Cu²⁺ was measured to be 0.44 μM. Subsequently, the in situ generated BNC-Cu²⁺ complex had been used for sensing Cys with the LOD of 1.5 μM through the displacement strategy, resulting in the revivable emission of BNC. According to the "off-on-off" fluorescence cycle of BNC generated by the alternate addition of Cu²⁺ and Cys, a reversible memorized device with "read-write-read-erase" behavior was constructed at the molecular level. Furthermore, the recoveries of Cu²⁺ in lake water with BNC were in the range of 95.0-105%. And sequential fluorescence imagings of BNC for Cu²⁺ and Cys were successfully applied in living yeast cells.

An easy-to-synthesize multi-photoresponse smart sensor for rapidly detecting Zn2+ and quantifying Fe3+ based on the enol/keto binding mode

A readily available salicylaldazine-modified fluorene Schiff base (EASA-F) exhibits fast fluorescent OFF–ON response to Zn²⁺ and OFF–ON–OFF behavior to Fe³⁺ synchronously accompanied the diverse absorption-ratiometric and colorimetric changes.

Thiophene-containing tetraphenylethene derivatives with different aggregation-induced emission (AIE) and mechanofluorochromic characteristics

Four thiophene-containing tetraphenylethene derivatives were successfully synthesized and characterized. All these highly fluorescent compounds showed typical aggregation-induced emission (AIE) characteristics and emitted different fluorescence colors including blue-green, green, yellow and orange in the aggregation state. In addition, these luminogens also exhibited various mechanofluorochromic phenomena.

Four thiophene-containing AIE-active TPE derivatives were synthesized. Furthermore, these luminogens exhibited various mechanofluorochromic phenomena.