Nucleotide/Tb³⁺ coordination polymer nanoparticles as luminescent sensor and scavenger for nitrite ion

A susceptible coordination hybrid based terbium sensibilization coupled ESIPT effects for pattern discrimination of analogues

Multianalyte detection and analogue discrimination are extremely valuable frontier areas for their wide applications in environmental, medical, clinical and industrial analyses. Nowadays, researchers rack their brains on how to develop excellent multianalyte chemosensors that have presented huge challenges in designing high-efficient fluorescent sensing materials and constructing high-throughput detection methods. In this paper, we propose a novel strategy to utilize the dual-emission fluorescent detection platform as a lab-on-a-molecule, arising from the disalicylaldehyde-coordinated hybrid H₂Q_j3/Tb based terbium sensibilization coupled excited-state intramolecular proton transfer effects. Using the statistical analysis (PCA and HCA) for sensing signals of three fluorescence channels (431, 543 and 583 nm), we demonstrate this elaborate chemosensor with multianalyte detection of three species (solvents, anions and cations) and pattern discrimination of analogues. As a result, the H₂Q_j3/Tb shows great lab-on-a-molecule characters for each set of species, resulting in the easier identification of many critical analytes (e.g., H₂O, NO₂^- and Fe³⁺) and discrimination of analogues. In addition, it is also proven to be able to provide reliable content determination for an analyte, especially the NO₂^- (LOD = 0.37 μM), and discrimination for mixed analogues. A combination of easy-to-implement preparation procedure and data analysis technique makes this work promising for not only designing similar lanthanide-based materials but also realizing more high-efficient multianalyte sensing systems towards various potential applications.

A Fast and Easy Probe Based on CMC/Eu (Ⅲ) Nanocomposites to Detect Acrylamide in Different Food Simulants Migrating from Food-Contacting Paper Materials

The residual acrylamide in food paper packaging can be transferred into water and food, which will cause harmful effects on human beings. In this paper, a rapid and easily available fluorescent probe based on carboxymethyl cellulose (CMC)/Eu (Ⅲ) nanocomposites was designed to detect the residue acrylamide with high sensibility. The probe could respond in 1 min. The concentration of acrylamide was linearly correlated to the fluorescence intensity of the probe at the emission wavelength of 615 nm in the concentration range of 0.1–100 μmol/L. The limit of detection (LOD) of the probe was 0.085 μg/L, which is lower than the guideline value of the European Union, the U.S. EPA, and the WHO. An experiment was performed to simulate the acrylamide migrating from food-contacting paper materials to different foods, including waterborne food, alcohol beverage, acidic food, and greasy food. The recoveries and RSDs of acrylamide in all samples indicated that the CMC/Eu (Ⅲ) fluorescent probe was efficient for acrylamide detection. The possible mechanism of the probe for acrylamide detection involved both dynamically quenching and static quenching by forming of non-fluorescent substances.

A ratiometric fluorescent sensor for detection of metformin based on terbium-1,10-phenanthroline-nitrogen-doped-graphene quantum dots

Metformin (MTF), an effective biguanide and oral antihyperglycemic agent, is utilized to control blood glucose levels in patients with type II diabetes mellitus, and the determination of its concentration in biological fluids is one of the main issues in pharmacology and medicine. In this work, highly luminescent nitrogen-doped graphene quantum dots (N-GQDs) were modified using terbium (Tb³⁺)–1,10-phenanthroline (Phen) nanoparticles (NPs) to develop a dual-emission ratiometric fluorescent sensor for the determination of MTF in biological samples. The synthesized N-GQDs/Tb–Phen NPs were characterized using different techniques to confirm their physicochemical properties. The N-GQDs/Tb–Phen NPs showed two characteristic emission peaks at 450 nm and 630 nm by exciting at 340 nm that belong to N-GQDs and Tb–Phen NPs, respectively. The results indicated that the emission intensity of both N-GQDs and Tb–Phen NPs enhanced upon interaction with MTF in a concentration-dependent manner. Also, a good linear correlation between the enhanced fluorescence intensity of the system and MTF concentration was observed in the range of 1.0 nM–7.0 μM and the limit of detection (LOD) value obtained was 0.76 nM. In addition, the prepared probe was successfully used for the estimation of MTF concentration in spiked human serum samples. In conclusion, the reported dual-emission ratiometric fluorescent sensor can be used as a sensitive and simple fluorimetric method for the detection of MTF in real samples.

Shcematic representation of the MTF detection by an enhancing mechanism.

Nanomolar determination of nitrofurans in water via excited-state inter-ligand proton transfer

Qualification and quantification of trace organic contaminants necessitates development of highly efficient sensing system, where excited-state inter-ligand proton transfer (ESILPT) provides a feasible pathway to construct efficient chemo-sensors. Herein, a strategically synthesized lanthanide complex, Eu(DBM)₃(MeOH)₃ (briefly as Eu-DBM-MeOH; DBM = dibenzoylmethane), features two-step ESILPT processes, along with modification on molecular structure and energy band. As a result, Eu-DBM-MeOH exhibits excellent photophysical properties with characteristic luminescence of Eu³⁺ ion. Benefiting from these merits, the Eu-DBM-MeOH complex acts as ultra-sensitive chemo-sensor toward nanomolar-level nitrofuran antibiotics (nitrofurazone and nitrofurantoin) in water, by disrupting ESILPT processes. Combining the advantages on photophysical property and luminescent sensitivity, ESILPT-active compounds are expected to widen and deepen the research on complex-based luminophores, being potentially useful in trace detection and biological imaging.

A novel ratiometric and colorimetric probe for rapid and ultrasensitive detection of nitrite in water based on an Acenaphtho[1,2-d] imidazole derivative

The concentration of nitrite (NO₂^-) ions above allowable limits in water resources and food stuffs is considered hazardous and has been proven to be of great threat to the environment and public health. In this work, an acenaphtho [1,2-d] imidazole derivative (1) as a ratiometric colorimetric probe is developed. UV-Vis experiments demonstrate that the probe 1 shows excellent selectivity toward NO₂^- in the presence of other potential interfering species, a rapid response (20 s) and a low detection limit (100 nM) by a distinct visual color change with a bathochromic shift of 120 nm from colorless to intense yellow. Besides, this probe is further used for the quantification of nitrite ions in environmental water resources such as tap water, underground water, and surface water samples. The high recoveries (96-99% with relative standard deviations (RSD) of <2.0%) make the probe 1 a promising candidate for practical applications in daily life in the detection of nitrite ions.

Carboxymethyl chitosan crosslinked ꞵ-cyclodextrin containing hydrogen bonded NC QDs nanocomposites to design fluorescence probes for manganese ion (II) sensing

The direct determination Mn²⁺ using carboxymethyl chitosan crosslinked with cyclodextrin containing hydrogen-bonded NC QDs (NC QD/CCSCD nanocomposites). The probable mechanism of the NC QD/CCSCD nanocomposites' fluorescence was quenched by Mn²⁺ could be interpreted as acyclic crown ether chelation. Mn²⁺ induced the NC QD/CCSCD clusters assembly to form large aggregates, which resulted in aggregation-caused quenching. The linear detection (I = 479.93-15.94C (R² = 0.9954)) can be established at Mn²⁺ concentrations from 0 to 21.11 × 10^-6 mol/L. Common metal ions, except iron and magnesium, showed minimal effect on detection. It could satisfy the standard range of Mn²⁺ in actual water samples. The method which using chelating assembly mechanism to build a novel sensor would provide a new model for the application of polymer materials in this field, but the precise assembly of polymer is an unsolved challenge.

A dual-modal fluorometric and colorimetric nanoprobe based on graphitic carbon nitrite quantum dots and Fe (II)-bathophenanthroline complex for detection of nitrite in sausage and water

A fluorometric and colorimetric dual-mode sensing platform based on graphitic carbon nitrite quantum dots (g-CNQDs) and Fe (II)-bathophenanthroline complex (BPS-Fe²⁺) was designed to the sensitive detection of nitrite (NO₂^-) in sausage and water. In this system, the fluorescence of g-CNQDs was quenched by BPS-Fe²⁺ complex due to the inner filter effect (IFE). When NO₂^- was present, Fe²⁺ was oxidized by nitrite to form BPS-Fe³⁺ complex with BPS, leading to the recovery of the fluorescence from g-CNQDs. Therefore, we constructed a "turn-off-on" fluorescence probe for detection of NO₂^-. Moreover, with the increase of NO₂^- concentration, the color of the solution changed from red to colorless, so the UV-vis measurements and on-site visual detection were realized. The method is capable of detecting NO₂^- in the concentration range of 2.32-34.8 μM with good selectivity and high sensitivity. In addition, the method has the potential to determine NO₂^- in water samples and sausage samples.

Highly selective and sensitive long fluorescence lifetime polyurethane foam sensor based on Tb-complex as chromophore for the detection of H2PO4- in water

Developing novel rare-earth complexes to rapidly and reliably sensing anions in pure water is highly challenging. Here, a series of long fluorescence lifetime polyurethane foam bonded Tb(BAA)₃ chromophore porous material (Tb-PUFs) have been designed and synthesized via a simple one-step co-polycondensation reaction as an efficient fluorescent sensor for H₂PO₄^- in pure water. All Tb-PUFs exhibited strong green emission and long fluorescence lifetime in water, which was ascribed to Tb-complex can be dispersed very well in polyurethane foam, effectively avoiding the emission quenching of Tb³⁺ ions caused by water molecules vibration. The titration experimental results showed that precursor Tb(BAA)₃ can effective recognize F^-, CH₃COO^-, and H₂PO₄^- in DMSO solution. Interestingly, Tb-PUFs can only selectively recognize H₂PO₄^- in pure water, this phenomenon can be explained that H₂PO₄^- is acidic, and can occur deprotonation with -NH group of ligand BAA, thus making the fluorescence quenching effect was more sensitive for H₂PO₄^- in pure water. In addition, the sensing ability of Tb-PUFs for H₂PO₄^- is highly reversible by washing them with deionized water for three times. In a word, all results implied that Tb-PUFs was an excellent candidate for H₂PO₄^- ions detection selectively in pure water.

A colorimetric and fluorescent lighting-up sensor based on ICT coupled with PET for rapid, specific and sensitive detection of nitrite in food

A colorimetric and fluorogenic sensor exhibiting rapid, specific and sensitive detection of potentially toxic nitrite in food is described.

Fluorescence probe based carboxymethyl cellulose/Tb(III) nanocomposites for detection of Mn2+ with simpleness, rapidness and high sensitivity

A novel, rapid, high selective and sensitive probe, carboxymethyl cellulose (CMC)/Tb(III) with green fluorescence, for detecting Mn²⁺ in aqueous solution during pH = 4-10 was proposed in this work. The probe's synthesis had benefits of mild reaction condition, organic solvent-free and facile operation. A linear relationship between the fluorescence intensity of CMC/Tb(III) probe at 544 nm with 0.046 μM detection limitation and the concentration of Mn²⁺ in the range of 0.1-100 μM was obtained. The probe was also used to detected Mn²⁺ in tap water and the recoveries were between 97.10% and 101.61%, and the relative standard deviations (RSD, n = 5) of all samples were less than 2.04%. The results by UV absorption spectrum and fluorescence quenching suggested that there might be a dynamic quenching occurred to the fluorescence of CMC/Tb(III) probe when Mn²⁺ was involved.