A simple, highly selective and ultra-sensitive “off-on-off” fluorescent chemosensor for successive detection of aluminum ion and phosphate in water samples

A bisalicylhydrazone based fluorescent probe for detecting Al3+ with high sensitivity and selectivity and imaging in living cells

A bisalicylhydrazone based fluorescence probe, bisalicyladehyde benzoylhydrazone (BS-BH), has been designed to detect Al3+. It exhibited high sensitivity and selectivity towards Al3+ in methanol-water media in physiological condition. Large stokes shifts (∼122 nm) and over ∼1000-fold enhanced fluorescence intensity were observed, which was ascribed to the formation of the two relatively independent rigid extended π conjugated systems bridged by biphenyl group when binding with Al3+. A 1:2 binding ratio between BS-BH and Al3+ was shown by Job's plot. Based on the fluorescence titration data, the detection limit was down to 3.50 nM and the association constant was evaluated to be 1.12 × 109 M-2. The plausible fluorescence sensing mechanism of suppressed ESIPT, inhibited PET, activated CHEF and restricted C = N isomerization was confirmed by a variety of spectral experiments and DFT / TD-DFT calculations. The reversibility of recognition of Al3+ for probe BS-BH was validated by adding Na2-EDTA. In addition, the MTT assay showed the good biocompatibility of BS-BH and BS-BH could be used for imaging Al3+ in living cells.

Microwave synthesis of chitosan-based carbon dots for Al3+ detection and biological application

Yellow fluorescent carbon dots (Y-CDs) were prepared via microwave method using chitosan and o-phenylenediamine as the main raw materials. The obtained Y-CDs possesses good water solubility, excellent biocompatibility and luminous stability. During the microwave pyrolysis carbonization process, the surface of Y-CDs was modified with the functional groups such as amino and carboxyl, which can bind to Al3+ by forming complexes, further improving the selectivity and sensitivity of the Al3+ detection. And the fluorescence of Y-CDs was quenched by Al3+ by static quenching process. More importantly, Y-CDs as fluorescent sensor was further applied for the determination of Al3+ in the real water samples with high reliability and accuracy. In addition, Y-CDs present potential application in biological imaging. The cultivated zebrafish embryos with Y-CDs displayed clearly in vivo uptake and metabolic fluorescence images, further confirming its low toxicity and excellent biocompatibility.

Ratiometric fluorescence sensor for sensitive detection of inorganic phosphate in environmental samples

Fast, simple, and low-cost on-site visualized detection of inorganic phosphate (Pi) is in great demand since phosphate is the major reason of eutrophication. In this work, a ratiometric fluorescent probe composed by green carbon dots (GCDs) and red carbon dots (RCDs) has been established for high-sensitivity and selective sensing of Pi. A trend of color change from red to green is observed for the detection of Pi under ultraviolet light and the detection limit is 0.09 μM in the range of 0 to 55 μM. Fluorescent test paper prepared from the probe solution was successfully applied to semi-quantitative visual detection of Pi in real-world water and soil samples, which shows great real-world application potentials.

Tracking the concentration of Al3+ in the aqueous system up to nanomolar range using modified biopolymer chitosan based fluorophore

The paper reports the development of biopolymer chitosan based fluorophore for selective detection of Al3+ in aqueous streams. Fluorescence sensing based on the change in the photophysical properties of the...

An Acylhydrazone-Based Fluorescent Sensor for Sequential Recognition of Al3+ and H2PO4. MATERIALS (BASEL, SWITZERLAND) 2021;14:6392. [PMID: 34771920 PMCID: PMC8585233 DOI: 10.3390/ma14216392]

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al3+ and H2PO4-. NATB displayed fluorometric sensing to Al3+ and could sequentially detect H2PO4- by fluorescence quenching. The limits of detection for Al3+ and H2PO4- were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al3+ and NATB-Al3+ to H2PO4- were found to be 1:1. The sequential recognition of Al3+ and H2PO4- by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al3+ and H2PO4- by NATB were investigated through fluorescence and UV-Visible spectroscopy, Job plot, ESI-MS, 1H NMR titration, and DFT calculations.

Ratiometric fluorescence for sensitive detection of phosphate species based on mixed lanthanide metal organic framework

Phosphate (PO₄^3-) plays a major role in aquatic ecosystems and biosystems. Developing a highly sensitive and selective ratiometric fluorescence probe for detection of PO₄^3- is of great significance to the ecological environment and human health. In this work, a novel dual lanthanide metal organic framework was synthesized via hydrothermal reaction based on Tb³⁺ and Ce³⁺ as the center metal ions and terephthalic acid as the organic ligand (designated as Tb-Ce-MOFs). The fluorescence of Tb-Ce-MOFs shows emission at 375 nm. In the presence of PO₄^3-, with increased concentration of PO₄^3-, the fluorescence intensity of Tb-Ce-MOFs at 500 nm and 550 nm increased, while the intensity at 375 nm was reduced. Hence, ratiometric fluorescence detecting of PO₄^3- can be achieved by measuring the ratio of fluorescence at 550 nm (FL₅₅₀) to 375 nm (FL₃₇₅) in the fluorescent spectra of the Tb-Ce-MOFs. In this sensing approach, the Tb-Ce-MOFs probe exhibits highly sensitive and selective for detection of PO₄^3-. The limit of detection is calculated to be 28 nM and the detection range is 0.1 to 10 μM. In addition, the Tb-Ce-MOFs were used in the detection of PO₄^3- in real samples. We design and synthesize a mixed lanthanide metal organic framework fluorescence probe (Tb-Ce-MOFs) for ratiometric fluorescence for the detection of PO₄^3- based on Tb³⁺ and Ce³⁺ as the center metal ions and terephthalic acid as the organic ligand.

An "off-on-off" fluorescence chemosensor for the sensitive detection of Cu2+ in aqueous solution based on multiple fluorescence emission mechanisms

A new organosiloxane precursor ((E)-3-hydroxy-4-((2-(2-hydroxy-4-(3-(3-(triethoxysilyl)propyl)ureido)benzoyl)hydrazono)methyl)phenyl(3-(triethoxysilyl)propyl)carbamate, hereinafter referred to as AHBH-Si) and tetraethylorthosilicate (TEOS) were mixed as the mixed Si source, and bridged periodic mesoporous organic silica (AHBH-PMOs) nanoparticles were obtained through the co-condensation reaction. AHBH-PMO nanoparticles possess mechanisms of "Aggregation Induced Emission" (AIE) and "Intramolecular Charge Transfer" (ICT), which originate from the molecular structure of AHBH having "C[double bond, length as m-dash]N" bond, ortho hydroxyl groups, etc.. Therefore, the optical properties of AHBH are excellent with respect to the solvent effect and enhanced fluorescence. For hybrid materials, the silica framework provides a rigid environment that restricts the rotation of AHBH, thereby turning on the fluorescence of AHBH due to the regulation by the AIE effect. In particular, AHBH-PMOs are no longer restricted by organic solvents and could really achieve the response to Cu2+ with high sensitivity and selectivity in aqueous solutions of a wide pH range. In addition, the detection limit is as low as 3.26 × 10-9 M. Methods such as Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry have shown the coordination interaction between AHBH and Cu2+. The Gaussian 09 software of density functional theory to calculate the reducing changes of energy gaps among AHBH and AHBH-Si before and after the addition of Cu2+ showed that coordination interaction exists in the system. These results indicate that AHBH-PMO hybrid materials have potential applications in the field of environmental monitoring.

A novel quinoline-based turn-on fluorescent probe for the highly selective detection of Al (III) and its bioimaging in living cells, plants tissues and zebrafish

A novel quinoline fluorescent probe QNP ((E)-N'-(5-chloro-2-hydroxybenzylidene) quinoline-2-carbohydrazide) for detection of Al3+ ion was designed, synthesized and characterized. QNP displayed a high fluorescence enhancement in the presence of Al3+ ion in DMF:PBS (99:1, v/v) solution and the detection limit was as low as 1.25 μM with high selectivity and excellent sensitivity from 0 to 3 μM. The sensing ability of QNP towards Al3+ ion is attributed to the synergistic effect of PET and ICT. Furthermore, the binding stoichiometry between QNP and Al3+ ion is of 1:1 by Job's plot and mass spectrum, and the calculated binding constant is 4.29 × 108 M-1. The detection of Al3+ ion in water samples illustrates that QNP could be applied to the detection of practical samples in the environment. Bioimaging experiments on Hela cells, zebrafish and soybean root tissues demonstrate that it has potential application to investigate biological processes involving Al3+ ion within living cells. A quinoline-based turn-on fluorescence probe for the detection of Al3+ and its bioimaging in living cells, plant, and zebrafish.