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Tuning the photophysical properties of carboranyl luminophores by <i>closo</i> - to <i>nido</i> -carborane conversion and application to OFF–ON fluoride sensing
摘要： A family of closo-carborane-appended luminophores (closo-OXD1–2 and closo-DPS1–2) in which 2-R-o-carboranes (R = H, Me) are attached to the diphenyl-1,3,4-oxadiazole (OXD) or diphenyl-sulfone (DPS) acceptor groups were prepared and characterized. Deboronation of the closo-carborane cage produced the corresponding nido-carboranyl luminophores (nido-OXD1–2 and nido-DPS1–2). Whereas the closo-compounds were poorly emissive in THF (ΦPL < 0.01), the nido-luminophores exhibited an intense fluorescence with good quantum yields (ΦPL = 0.1–0.45). Electrochemical studies showed that while the closo-OXD and -DPS compounds displayed only carborane-centred, quasi-reversible reduction, the nido-compounds exhibited the typical features for nido-carborane-centred, irreversible oxidation and acceptor-centred, reversible reduction. Theoretical studies suggested that while the 1ππ* state of closo-compounds is nonemissive due to the contribution of closo-carborane to the LUMO in the S1 excited state, the intramolecular charge transfer (ICT) state from the nido-carborane to acceptor moieties in nido-compounds leads to an efficient fluorescence. Finally, THF solutions of closo-OXD1 and -DPS1 showed strong fluorescence upon the addition of fluoride anions under mild heating, but were intact to other anions, including cyanide, allowing the selective OFF–ON fluorescence sensing of fluoride.
关键词： fluoride sensing,carborane,fluorescence,photophysical properties,luminophores
更新于2025-11-20 15:33:11
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Magnesium tetrapyrazinoporphyrazines: tuning of the pKa of red-fluorescent pH indicators
摘要： Magnesium (II) tetrapyrazinoporphyrazines (TPyzPzs) are excellent red fluorophores (λF ~ 663 nm, ΦF ~ 0.53 in THF). In this work, a series of magnesium (II) complexes of unsymmetrical TPyzPzs bearing one or two phenol substituents was prepared. Suitable substitutions on the phenolic moiety tuned its pKa in the range of 5.5 to 13. Deprotonation of the phenolic group at higher pH induced a strong donor (phenolate) in the macrocycle that led to pH-dependent quenching of the red fluorescence of these indicators. pH sensing was proven in water solutions after incorporation of TPyzPs into two delivery systems – microemulsions and liposomes. The latter also serves as a simple model of biomembranes. Finally, a wavelength-ratiometric probe was constructed by incorporation of a TPyzPz indicator and lipophilic pH-nonsensitive BODIPY dye into liposomes. Synthetic precursors for TPyzPzs, substituted pyrazine-2,3-dicarbonitriles, also represent donor-acceptor system and the pH-dependent changes in absorption spectra may be easily visible to the naked eye.
关键词： pH indicators,microemulsions,fluorescence,BODIPY,wavelength-ratiometric probe,liposomes,tetrapyrazinoporphyrazines,magnesium complexes
更新于2025-11-20 15:33:11
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Sulfur and Nitrogen Co-Doped Graphene Quantum Dots as a Fluorescent Quenching Probe for Highly Sensitive Detection toward Mercury Ions
摘要： Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) were synthesized through an efficient infrared (IR)-assisted pyrolysis of glucose, urea, and ammonia sulfate at 260°C. These served as a highly selective probe for the sensing of Hg2+ ions in an aqueous solution. The IR technique can also prepare N-doped graphene quantum dots (N-GQDs), which have been compared with SN-GQDs for their fluorescence (FL) quenching sensitivities by Hg2+ ions. The FL intensities of both GQDs show decreasing functions of concentration of Hg2+ ions within the entire concentration ranges of 10 ppb?10 ppm. The sensitivity of SN-GQD is 4.23 times higher than that of N-GQD, based on the calculation of the Stern-Volmer equation. One inter-band gap structure of SN-GQDs for the detection of mercury ions is proposed. The S doping can coordinate with phenolic groups on the edge of SN-GQDs (i.e., the formation of (CxO)2Hg2+) and induce the cutting off or alleviation of photon injection paths, thereby leading to significant FL quenching. This work proves that SN-GQD offers sufficient sensitivity for probing the quality of drinking water to ensure that it contains less than 10 ppb of Hg2+ ions, as per the World Health Organization standard.
关键词： Fluorescence quenching,Nitrogen doping,Infrared-assisted heating,Graphene quantum dots,Sulfur doping,Mercury detection
更新于2025-11-19 16:56:42
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Monitoring of polycyclic aromatic hydrocarbon contamination at four oil spill sites using fluorescence spectroscopy coupled with parallel factor-principal component analysis
摘要： Fluorescence spectroscopy analysis of oil and environmental samples collected from four oil spill incidents in Canada—a 2016 pipeline spill into the North Saskatchewan River (NSR), Saskatchewan; a 2015 train derailment in Gogama, Ontario; the 1970 sinking of the SS Arrow ship in Chedabucto Bay, Nova Scotia; and the 1970 sinking of the Irving Whale barge in the Gulf of St. Lawrence—permitted assessment of the PAH content of environmentally weathered samples. A recently developed fluorescence fingerprinting model based on excitation–emission matrix-parallel factor analysis-principal component analysis (EEM-PARAFAC-PCA) was applied to (i) evaluate the intensity of the abundant PAH groups in the samples, (ii) investigate changes in the PAH composition of environmental samples over time due to weathering, and (iii) classify the original spilled oil and environmental samples within the already established classes of the fingerprinting PCA model. The environmental sediment samples collected from the Husky Energy spill site show loss of PAHs occurring over the course of 15 months post-spill. However, the extent of weathering depends on several environmental factors rather than solely the time of weathering, the PAH loss was maximum at 15 months. There was a decrease in the PAH content of the environmental samples of Gogama spill collected 20 months post-spill. Almost all of Gogama environmental sediment samples underwent substantial weathering, making PCA classification impractical. The SS Arrow and Irving Whale samples fell within adjacent PCA groups, as they both had a similar type of spilled oil (Bunker C) with similarity in chemical composition.
关键词： EEM-PARAFAC-PCA,fluorescence spectroscopy,environmental monitoring,oil spill,PAH contamination
更新于2025-11-19 16:56:42
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Photoluminescence enhancement <i>via</i> microwave irradiation of carbon quantum dots derived from solvothermal synthesis of <scp>l</scp> -arginine
摘要： Photoluminescence enhancement of carbon quantum dots was achieved via solvothermal synthesis followed by microwave irradiation. Nitrogen and phosphorous doped carbon quantum dots were prepared by solvothermal heating of L-arginine with phosphoric acid for 12 hours followed by microwave irradiation for 3 minutes. The photoluminescence enhancement was nearly two fold after microwave irradiation. The morphology, structure, and surface properties were the same for the solvothermal (CQDs-S) as well as after microwave (CQDs-M) irradiation. Thus, the enhancement is attributed to the decrease of surface defects within CQDs, which led to a decrease in the non-radiative transitions. The CQDs were quenched selectively by Fe3+ ions. The quenching led to the fabrication of the fluorescence probe for ferric ion determination. The CQDs-M had a low detection limit of 4.0 nM, while CQDs-S had a limit of 50 nM. This study gives a tool for enhancing photoluminescence quantum yields, which is highly desired for biosensing and bioimaging applications.
关键词： Photoluminescence enhancement,Fluorescence probe,Solvothermal synthesis,Ferric ion determination,Microwave irradiation,Carbon quantum dots
更新于2025-11-19 16:56:42
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Tuning the luminescence of nitrogen-doped graphene quantum dots synthesized by pulsed laser ablation in liquid and their use as a selective photoluminescence on–off–on probe for ascorbic acid detection
摘要： In this work, nitrogen-doped graphene quantum dots (N-GQDs) were synthesized by pulsed laser ablation in liquid using Nd:YAG laser (532 nm). Graphite target was ablated in dimethylformamide, as solvent and nitrogen source, and the microstructure as well as optical properties of N-GQDs were studied. The N-GQDs structure consists of a graphitic core with oxygen and nitrogen functionalities and particle size about 3 nm, as demonstrated by X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The as-prepared N-GQDs structure was modified by solvothermal treatment at 65, 90 and 120 °C reducing the oxygen functional groups, adding nitrogen and restoring the π-conjugated structure of N-GQD. The N-GQDs exhibit UV-Vis absorption spectrum with the characteristic π-π* and n – π* electronic transitions of the GQDs with a large amount of oxygen and nitrogen functionalities. These N-GQDs exhibited a visible light photoluminescence centered at 486 nm upon an excitation of 410 nm and the photoluminescence intensity enhanced up to 4.05% of quantum yield after solvothermal treatment. The N-GQDs dispersion was used for selective detection of ascorbic acid, through a signal-off and signal-on system. The results show the use of N-GQDs as a competent photoluminescence sensor for metal ions and ascorbic acid.
关键词： Fluorescence quenching,electron transfer,carbon nanoparticles
更新于2025-11-19 16:56:42
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Diffusion Behavior of Differently Charged Molecules in Self-Assembled Organic Nanotubes Studied Using Imaging Fluorescence Correlation Spectroscopy
摘要： The diffusion behavior of fluorescent molecules within bolaamphiphile-based organic nanotubes (ONTs) was systematically investigated using imaging fluorescence correlation spectroscopy (imaging FCS). Anionic sulforhodamine B (SRB), zwitterionic/cationic rhodamine B (RB) or cationic rhodamine 123 (R123) was loaded into ONTs having cylindrical hollow structures (ca. 10 nm in inner diameter) with amine and glucose groups on the inner and outer surfaces, respectively. Wide-field fluorescence video microscopy was used to acquire imaging FCS data for dye-doped ONTs in aqueous solutions of different ionic strengths (1 – 500 mM) at different pH (3.4 – 8.4). The diffusion behavior of these dyes was discussed on the basis of their apparent diffusion coefficients (D) that were determined by autocorrelating the time transient of fluorescence intensity at each pixel on an ONT. Molecular diffusion in the ONTs was significantly slowed by molecule-nanotube interactions, as shown by the very small D (10-1 – 10-2 μm2/s). The pH-dependence of D revealed that dye diffusion was basically controlled by electrostatic interactions associated with the protonation of the amine groups on the ONT inner surface. The pH-dependent change in D was observed over a wide pH range, possibly due to electrostatically induced variations in the pKa of the densely packed ammonium ions on the ONT inner surface. On the other hand, the influence of ionic strength on D was relatively unclear, suggesting the involvement of non-coulombic interactions with the ONTs in molecular diffusion. Importantly, individual ONTs of different lengths (1 – 5 μm) afforded similar diffusion coefficients for each type of dye at each solution condition, implying that the properties of ONTs were uniform in terms of solute loading and release. These results highlight the characteristics of molecular diffusion behavior within the ONTs, and will help in the design of organic nanotubes better suited for use as drug vehicles and contaminant adsorbents.
关键词： Electrostatic Interactions,Diffusion Behavior,Ionic Strength,pH-dependence,Imaging Fluorescence Correlation Spectroscopy,Organic Nanotubes
更新于2025-11-19 16:56:42
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Facile preparation of boron and nitrogen co-doped green emission carbon quantum dots for detection of permanganate and captopril
摘要： A hydrothermal strategy for preparing boron and nitrogen co-doped carbon quantum dots was studied using the precursors of p-amino salicylic acid, boric acid and ethylene glycol dimethacrylate. The boron and nitrogen co-doped carbon quantum dots have high fluorescence intensity, good monodispersity, high stability, superior water solubility, and a fluorescence quantum yield of 19.6%. Their average size is 5 nm. Their maximum excitation and emission wavelengths are 380 nm and 520 nm, respectively. Permanganate (MnO4-) quenched boron and nitrogen co-doped carbon quantum dots fluorescence through inner filter effect and static quenching effects. The linear relation between quenching efficiency and MnO4- concentration ranged from 0.05 to 60 μmol/L with a detection limit of 13 nmol/L. In the presence of captopril, MnO4- was reduced to Mn2+ and the fluorescence of boron and nitrogen co-doped carbon quantum dots was recovered. The linear range between recovery and captopril concentration was from 0.1 to 60 μmol/L. The limit of detection was 0.03 μmol/L. The developed method can be employed as a sensitive fluorescence sensing platform for MnO4-. It has been successfully used for captopril detection in mouse plasma.
关键词： Captopril,Plasma,Fluorescence,Potassium permanganate,Carbon quantum dots
更新于2025-11-19 16:56:42
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Spectroscopic properties of push-pull 2-(4-carboxyphenyl)-6-dimethylaminobenzothiazole derivatives in solution and the solid state
摘要： 6-Dimethylamino-2-phenylbenzothiazoles with a carboxy, ester and amide substituent on the 2-phenyl group were prepared as a series of the push-pull benzothiazoles, and their spectroscopic and photophysical properties in solutions were investigated. The derivatives showed solvatochromic fluorescence with quantum yields over 0.68 in various organic solvents similar to the core fluorophore structure. The color variation ranges in fluorescence solvatochromism of the derivatives were wider than that of the original compound having the core structure, 6-dimethylamino-2-phenylbenzothiazole. It was also found that the derivatives together with the original compound show solid state fluorescence depending on their crystal structures. In particular, an ester derivative with a protected serine has a reasonable crystal packing leading to increase in fluorescence efficiency. The results of the present study provide a guide to design push-pull 2-phenylbenzothiazoles exhibiting fluorescence in solution and the solid state.
关键词： Substituent effect,Firefly oxyluciferin,Fluorescence solvatochromism,Solid state fluorescence,Benzothiazole
更新于2025-11-19 16:56:35
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Rational design of a visible-light photochromic diarylethene: a simple strategy by extending conjugation with electron donating groups
摘要： Photochromic diarylethenes have been widely used in many fields. However, their cyclization process must be induced by UV light. In this article, a simple strategy is developed by extending π-conjugation with electron donating groups. The modified dirylethene derivative can photocyclolize under 405-nm light with a good photochromic efficiency. Meanwhile, its absorption and moderate fluorescence can be switched effectively in both directions by visible lights (405 and 520 nm, respectively) in different solutions and in living cells. We believe that this simple method will become a versatile strategy for developing various dirylethylenes with visible-light photochromism.
关键词： fluorescence photoswitching,diarylethylenes,photoreaction quantum yield,visible-light photochromism
更新于2025-11-19 16:56:35