Spectroscopic and theoretical studies on a novel bis(salamo)-like probe for highly effective fluorimetric-colorimetric identification of Fe3+ and Cu2+ in aquo-organic medium

Sensitive and selective chemosensor for Fe3+ detection using carbon dots synthesized by microwave method

The excessive accumulation of heavy metal ions can pose significant hazards to human health and the environment, hence the detection and removal of heavy metal ions from water bodies are essential. Generally, carbon dots (CDs) are used as a good fluorescence sensor to sense heavy metal ions. In this study, using one-step microwave method, CDs were synthesized with the traditional Chinese medicine Radix Vladimiriae as a carbon source for the first time. These CDs display excellent fluorescence properties with an average particle size of approximately 5.9 nm and a fluorescence quantum yield (QY) about 0.15. The fluorescence emission spectra were recorded at different excitation peaks with the highest intensity emission peak observed at 465 nm with an excitation wavelength of 360 nm. Interestingly, fluorescence intensities of CDs greatly decreased in the existence of Fe3+. Under optimum conditions, a good linear relationship was observed between (I0-I)/I and the Fe3+ concentration in the range of 0.2-200 μM with the correlation coefficient (R2) of 0.9992 and the limit of detection (LOD) of 62 nM. Finally, after adding Fe3+ at concentrations of 5 μM, 20 μM, and 50 μM to real water samples, the relative standard deviation and spiked recovery rates were 1.2 %-2.7 % and 99.2 %-101.6 %, respectively. Thus, a novel method for rapid detection of Fe3+ were successfully discovered.

A quinoline colorimetric ionic liquid probe by electrostatic enhancement for visual detection of Fe3+ in food

Excessive or insufficient iron(Ⅲ) will pose burdens of human body, and its content is the key to control the function of iron-fortified food. In this regard, a functionalized quinoline ionic probe, benefiting from the electrostatic attraction, was designed for the colorimetric detection of Fe3+ in food. This probe formed a 2: 1 complex with Fe3+, altering the UV-vis spectra and solution color. The UV-vis detection limit was 0.2 μM, and visually, the color shifted from light-yellow to dark-green as Fe3+ concentrations increased, with a visual detection limit of 3.4 μM, meeting the maximum acceptable level of 5.4 μM. Noteworthy, ionic liquid-based sensing paper was constructed for rapid, semi-quantitative Fe3+ detection. Furthermore, the satisfying recovery (97.4-102.9 %) was obtained in real samples, showcasing the probe's efficiency. This work demonstrated the potential of ionic liquids for the fast, sensitive, and visual detection of Fe3+, offering a promising direction for metal element sensing platforms.

A highly selective and recyclable fluorescent sensor based on a Salamo-Salen-Salamo type ligand for continuous detection of Al3+ and phosphates in drug

In this work, a fluorescence chemical sensor continuous detection Al3+ and phosphates by a Salamo-Salen-Salamo type compound (SL) was employed. The sensor continuously recognized Al3+ and phosphates with good selectivity and fast response time, and a low limit of detection of 0.25 μΜ and 0.96 μM, at the same time accompanied by a naked-eye identification specificity. The detection mechanism of SL towards Al3+ is due to the chelating fluorescence enhancement effect and ICT effect, and continuously towards phosphates is due to the collapse of the SL-Al3+ and coordination interaction between Al3+ and phosphates, by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, other spectral characterization and DFT calculation as evidence. In addition, the sensor had good recyclability and reusability. The distribution of Al3+ and phosphates in zebrafish cells was effectively monitored by confocal microscopy based on the good biocompatibility and tissue permeability of SL. Furthermore, the feasibility of using sensor SL to detect the content of Al3+ and phosphate ions in certain drugs was quantitatively analyzed through experiments. It was found SL had a good result in practical application.

Ampicillin-derived carbon dots as the sensitive probe for the detection of Fe3+ and Cu2+ in living cells and water samples

Water-soluble N-doped fluorescent (FL) carbon dots (ACDs) were successfully fabricated hydrothermally using ampicillin sodium as sole precursor. The produced ACDs exhibit satisfactory optical behavior, favorable photostability, and acceptable water solubility. With bright blue emission at 450 nm, the ACDs were utilized for multivariate sensing Fe3+ and Cu2+ based on the synergistic effect of the inner filter effect (IFE) and static quenching with detection limits of 0.31 μM and 0.26 μM, respectively. The practicality of ACDs has been verified by the successful determination  of Fe3+ and Cu2+ in real water and living cells. These findings confirm the feasibility of the proposed ACDs as FL sensors for efficient and selective detection of Fe3+ and Cu2+, which present promising prospects for real-time monitoring these two metal ions  in environmental and biological systems.

A benzimidazole-appended double-armed salamo type fluorescence and colorimetric bifunctional sensor for identification of MnO4- and its applications in actual water samples

The symmetrically double-armed salamo type fluorescent sensor BMS, incorporating benzimidazole units, was designed and synthesized. Showcasing remarkable specificity and responsiveness to MnO4- within a DMSO:H2O (V/V = 9:1, pH = 7.2) Tris-HCl buffer medium, it enabled dual-channel detection of MnO4- through fluorescent and colorimetric changes. Critical experimental parameters, including detection and quantification thresholds (LOD and LOQ) along with binding affinity constants (Ka), were calculated using the Origin software. A rational interaction mechanism between BMS and MnO4- was deduced, based on fluorescence titration, Electrospray Ionization Mass Spectrometry (ESI-MS), Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared Spectroscopy (IR), Stern-Volmer plots, and Density Functional Theory (DFT) computations. Additionally, the sensor BMS was applied to monitor MnO4- in real water samples. Advancing its practical utility, BMS was fabricated into test strips for the selective detecting of MnO4-.

An unusual highly sensitive dual-channel bis(salamo)-like chemical probe for recognizing B4O72-, sensing mechanism, theoretical calculations and practical applications

A bis(salamo)-like chemical sensor H3L ((1E,3E)-2-hydroxy-5-methylisophthalaldehyde O,O -di(3-((((E)-(2-hydroxynaphthalen-1-yl)methylene)amino)oxy)propyl) dioxime) was constructed. H3L is capable of recognizing B4O72- in H2O/DMF (1:9, v/v) solution by both fluorescent and colorimetric channels, bright green fluorescence was turned on when B4O72- was added to H3L and changed from colorless to yellow in natural light. The detection limit was 3.21 × 10-8 M. The identification has good anti-interfering ability, quickly responsive time (5 S) and broad pH detecting range (pH = 5-12). The mechanism of action was determined by 1H NMR titration, infrared spectrometry, HRMS spectra and further elucidated by theory calculations. The fluorescence imaging of bean sprouts and spiked recovery assays of actual water samples demonstrated the practical use of sensor H3L for the detection of B4O72-, which is expected to have applications for the detection of B4O72- in plants and the environment.

Phenothiazine appended thiophene derivative: a trilateral approach to copper ion detection in living cells and aqueous samples

This research paper unveils a fluorescent probe (PTZ-SCN) engineered for the specific detection of Cu2+, featuring a 10-ethyl-10H-phenothiazine-3-carbaldehyde and 2-(thiophen-2-yl) acetonitrile moiety. The fluorescence sensing behavior of PTZ-SCN towards various metal cations was scrutinized in CH3CN : HEPES (9 : 1) buffer aqueous solution. The UV absorbance of PTZ-SCN displayed a distinct red shift in the presence of Cu2+ cations, whereas other metal cations did not cause any interference. Similarly, the fluorescence emission of the probe was also only quenched by Cu2+ cations. The limit of detection (LOD) was calculated as 1.0461 × 10-8 M. PTZ-SCN showed the ability to identify Cu2+ using the colorimetric method, the fluorometric method and even through visual observation in a trilateral detection. We studied the recognition mechanism of PTZ-SCN for Cu2+ using 1H-NMR, HRMS analysis, and time-dependent density functional theory (TDDFT) calculations. Furthermore, our study encompassed the investigation of PTZ-SCN's practical applicability, bridging the gap from research to real-world implementation. This was achieved by employing test strips and water samples for the detection of Cu2+. Additionally, the PTZ-SCN probe's low cytotoxicity and effective imaging properties for Cu2+ in living cells were confirmed, indicating that PTZ-SCN shows the potential to serve as a promising probe for detecting Cu2+in vivo.

A unique N-heterocyclic oligo(N,O-donor) salamo-Ni(II)-based probe for highly selective fluorescence detection of Cr2O72

A unique fluorescent probe Ni-DAS was developed by a nitrogenous heterocyclic oligo(N,O-donor) salamo-based compound DAS. DAS exhibits AIE and ESIPT effects which are extremely infrequent in salamo-based multi-oxime compounds. In addition, Ni-DAS can be used as a fluorescent probe with high selectivity and sensitivity to recognize Cr2O72- in DMF with 80 % water content, which enhances the value of the probe for application in real environments, and outperforms most similar molecular fluorescence probes. The probe Ni-DAS can recognize Cr2O72- by oxidative hydrolysis of C = N bonds, which promotes further research on theory of C = N bond hydrolysis, and the binding ratio and recognition mechanism were verified and supported by relevant theoretical calculations (DFT & MESP). The experiments showed that the probe Ni-DAS can be used for ion detection in real environments. It provides a new strategy for the oxidative hydrolysis of C = N bond and the structure of salamo-based compounds with AIE nature, and offers new ideas for study ion recognition and acidity detection.

A nonsymmetrical salamo-like fluorescence chemical sensor for selective identification of Cu2+ and B4O72- ions and practical applications

An innovative salamo-like fluorescent chemical sensor H2L, has been prepared that can be utilized to selectively detect Cu2+ and B4O72- ions. Cu2+ ions can bind to oxime state nitrogen and phenol state oxygen atoms in the chemosensor H2L, triggering the LMCT effect leading to fluorescence enhancement. The crystal structure of the copper(II) complex, named as [Cu(L)], has been achieved via X-ray crystallography, and the sensing mechanism has been confirmed by further theoretical calculations with DFT. Besides, the sensor H2L recognizes B4O72- ions causing an ICT effect resulting in bright blue fluorescence. Moreover, the sensor has relatively high selectivity and sensitivity for Cu2+ and B4O72- ions, and the detection limits are 1.02 × 10-7 and 2.06 × 10-7 M, respectively. In addition, the good biocompatibility and excellent water solubility of the sensor H2L make it very advantageous in practical applications, using H2L powder for fingerprint visualization, using H2L to identify the phenomenon of B4O72- ions emitting bright blue fluorescence, making it an ink that can print encrypted messages on A4 paper, in addition to this, based on H2L, the real water sample was tested for Cu2+ ion recognition, and finally the test strip experiment was carried out.