A new naphthalimide-picolinohydrazide derived fluorescent "turn-on" probe for hypersensitive detection of Al3+ ions and applications of real water analysis and bio-imaging

The development of high-selective chemosensors for trace Al³⁺ detection in the ecosystem is crucially importance due to its detrimental effects. In this work, a simple Schiff-base fluorescent probe NPP derived from naphthalimide and picolinohydrazide was rationally designed and prepared for efficient detection of Al³⁺. NPP exhibited prominent sensing behaviors toward Al³⁺ with low detection limit (LOD) (39 nM), rapid response time (1 min), strong binding affinity (4.02 × 10⁴), good anti-interference characteristics and visual detection. Binding ratio of NPP-Al³⁺ complex was determined to be 1:1 by Job's plot analysis. In addition, the chelation mechanism of NPP with Al³⁺ ions was proposed and substantiated by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT), IR spectrum and ¹H NMR titration experiments. Furthermore, this "signal-on" probe NPP was efficiently utilized as a promising indicator for Al³⁺ detection in environmental and biological samples.

Naphthalimide appended isoquinoline fluorescent probe for specific detection of Al3+ ions and its application in living cell imaging

Herein, a novel Schiff base fluorescent probe NIQ based on naphthalimide and iso-quinoline units has been readily prepared for the selective detection of Al³⁺ ions. The obviously visible color changes and prominent fluorescence enhancement were observed upon the addition of Al³⁺ to NIQ, which could be attributed to the complexation of NIQ with Al³⁺ and thus leading to the inhibition of photo-induced electron transfer (PET) and the chelation-enhanced fluorescence (CHEF) progress. The limit of detection (LOD) was 52 nM that was far below the standard recommended by the WHO. Binding ratio (1:1) of NIQ with Al³⁺ ions was supported by Job's plot. The binding constant of NIQ for Al³⁺ were calculated to be 3.27 × 10⁵ M^-1 on the basis of benesi-Hildebrand plot. The plausible binding mechanism for NIQ towards Al³⁺ ions was evidenced by the density functional theory (DFT) and ¹H NMR titration experiment. Furthermore, this "turn-on" probe NIQ has been successfully applied as a biomarker for imaging the Al³⁺ ions in living cells.

A purine based fluorescent chemosensor for the selective and sole detection of Al3+ and its practical applications in test strips and bio-imaging

A novel purine Schiff base fluorescent probe (WYW), (E)-4-methyl-2-((2-(9-(naphthalen-1-yl)-8-(thiophen-2-yl)-9H-purin-6-yl)hydrazono)methyl)phenol, was designed and prepared as an excellent reversible fluorescent chemosensor for monitoring Al³⁺. The fluorogenic "turn-on" sensor WYW exhibited high selectivity towards Al³⁺ over other coexistent metal ions, accompanying with an obvious visual color change in DMSO/H₂O (9/1, v/v, pH = 7.4) media. The enhancement fluorescence of WYW could be attributed to the inhibition of PET and ESIPT process induced by Al³⁺. Notably, the WYW-Al³⁺ complex exhibited a fluorescence "turn-off" response towards F^- with exceptional selectivity via the displacement approach. The detection limit of WYW for Al³⁺ was calculated to be as low as 82 nM. The formation of complex WYW-Al³⁺ (1:1 stoichiometry) was confirmed by Job's methods and further verified by density functional theory (DFT) calculations. Furthermore, the probe WYW with low cytotoxicity and excellent membrane-permeable property has also been successfully applied for detecting low concertation Al³⁺ in living HeLa cells.

Preparation of sulfur-doped carbon quantum dots from lignin as a sensor to detect Sudan I in an acidic environment

To achieve a rapid and facile quantitative evaluation of Sudan I illegally added in ketchup, fluorescent carbon quantum dots with excellent stability in acidic environments are required as the actual pH value of ketchup is close to 4.0. In this paper, we developed a green approach to prepare sulfur-doped carbon quantum dots (SCQDs) via hydrothermal treatment of lignin, isolated from pre-hydrolysis liquor, in sulfuric acid solution. The resultant SCQDs from lignin possessed sulfur-containing groups, which exhibited excellent fluorescence with a quantum yield up to 13.5% and good stability in acidic environments with a wide pH range of 0-5.0. Therefore, the SCQDs were successfully employed as a sensor to detect Sudan I in acidic solutions with excellent selectivity and sensitivity. The linear range for Sudan I was 0-40 μM, while the limit of detection was 0.12 μM. In addition, the fluorescent indicator paper functionalized with SCQDs also showed outstanding selectivity to Sudan I. The proposed SCQD sensing system not only displayed application potential for quantitative evaluation of Sudan I dye in practical samples, but also provided a way to convert lignin-based waste into highly valued nanoscale materials.

Dual recognition of Al3+ and Zn2+ ions by a novel probe based on diarylethene and its application

We synthesized a new fluorescent probe 1O by attaching a diarylethene molecule to a functional group. The probe can be used to detect Al3+ and Zn2+ at the same time with high selectivity, and its detection limit is very low. When Al3+ was added, the fluorescence intensity was increased 310 folds, and was accompanied by a fluorescent color change from black to grass-green. Similarly, after the addition of Zn2+, the fluorescence intensity was enhanced 110 folds, with a concomitant color change from black to yellow-green. Moreover, based on the properties of 1O, we designed a logic circuit, and that also can be used for water sample testing.

A turn-on fluorescence sensor for the highly selective detection of Al3+ based on diarylethene and its application on test strips

A novel fluorescent sensor, 1O, based on photochromic diarylethene with a 2-hydroxybenzhydrazide unit was designed and synthesized and can be used to recognize Al³⁺ in methanol (2.0 × 10⁻⁵ mol L⁻¹).

Heteroatom-doped carbon dots: synthesis, characterization, properties, photoluminescence mechanism and biological applications

Heteroatom-doped carbon dots (CDs), due to their excellent photoluminescence (PL) properties, attracted widespread attention recently and demonstrated immense promise for diverse applications, particularly for biological applications. The objective of this feature article is to provide a comprehensive overview of the recent progress in the research and development of heteroatom-doped CDs and a detailed description of the influence of single or co-doping heteroatoms on their PL behavior. The most recent understanding and critical insights into the PL mechanism of heteroatom-doped CDs are also highlighted. Moreover, potential bio-related applications of heteroatom-doped CDs in biosensing, bioimaging, and theranostics are also reviewed. This state-of-the-art review will provide a platform for understanding the intricate details of heteroatom-doped CDs, a summary of the latest progress in the field, and related applications in biology and is expected to inspire further developments in this exciting class of materials.