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Selective Detection of Trinitrophenol by Amphiphilic Dimethylaminopyridine-Appended Zn(II)phthalocyanines at the Near-Infrared Region
摘要： Novel amphiphilic Zn(II)phthalocyanines (ZnPcs) peripherally substituted with four and eight dimethylaminopyridinium units (ZnPc1 and ZnPc2) were synthesized by cyclotetramerization of the corresponding phthalonitriles. The effect of aggregation and photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties was investigated. The chemosensing ability of ZnPcs toward explosive nitroaromatic compounds was explored in aqueous medium. This study demonstrates that ZnPc1 and ZnPc2 show fluorescence quenching behavior upon interaction with different nitro analytes and show unprecedented selectivity toward 2,4,6-trinitrophenol with a limit of detection (LOD) of 0.7?1.1 ppm with a high quenching rate constant (Ksv) of 1.6?2.02 × 105. The near-infrared (NIR) fluorescence in thin films was quenched efficiently because of the photoinduced electron-transfer process through strong intermolecular π?π and electrostatic interactions. The sensing process is highly reversible and free from the interference of other commonly encountered nitro analytes. Further, experiments were performed to demonstrate the use of ZnPcs as efficient heterogeneous photocatalysts in the reduction of nitro explosives. The smart dual performance of multicharged ZnPcs in aqueous media quantifies them as attractive candidates in developing sensor materials at the NIR region and to possibly convert the toxic explosives into useful scaffolds. These results provide an interesting perspective toward elaboration of stable fluorescent systems for the selective sensing behavior of nitro explosives and their facile heterogeneous catalytic behavior in the reduction reactions.
关键词： trinitrophenol,photocatalysis,explosive detection,near-infrared,fluorescence quenching,dimethylaminopyridinium,Zn(II)phthalocyanines
更新于2025-11-21 11:08:12
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Facile Synthesis of Luffa Sponge Activated Carbon Fiber Based Carbon Quantum Dots with Green Fluorescence and Their Application in Cr(VI) Determination
摘要： Carbon quantum dots (CQDs) were prepared by a chemical oxidation method using lu?a sponge based activated carbon ?ber as the raw material. The obtained CQDs were well characterized. The ?uorescence quenching e?ect of Cr(VI) ion on CQDs was investigated. The results show that the addition of Cr(VI) changes the intensity of the ultraviolet characteristic absorption peak of CQDs, and causes static quenching of the ?uorescence of CQDs. With the increase in the Cr(VI) concentration, the ?uorescence of CQDs was gradually extinguished linearly.
关键词： Activated carbon ?ber,Lu?a sponge,Cr(VI) determination,Fluorescence quenching,Carbon quantum dots
更新于2025-11-21 11:01:37
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Highly sensitive and selective label-free detection of dopamine in human serum based on nitrogen-doped graphene quantum dots decorated on Au nanoparticles: Mechanistic insights through microscopic and spectroscopic studies
摘要： A rapid, facile and label-free sensing strategy is developed for the detection of dopamine (DA) in the real samples by exploiting nitrogen-doped graphene quantum dots (N-GQDs) decorated on Au nanoparticles (Au@N-GQD). The as-grown Au@N-GQD exhibits strong blue fluorescence at room temperature and the fluorescence intensity is drastically quenched in presence of DA in neutral medium. The mechanistic insight into the DA sensing by Au@N-GQDs is explored here by careful monitoring of the evolution of the interaction of Au NPs and N-GQDs with DA under different conditions through electron microscopic and spectroscopic studies. The highly sensitive and selective detection of DA over a wide range is attributed to the unique core-shell structure formation with Au@N-GQD hybrids. The quenching mechanism involves the ground state complex formation as well as electron transfer from N-GQDs. The presence of Au NPs in Au@N-GQD hybrids accelerates the quenching process (~14 fold higher than bare N-GQDs) by the formation of stable dopamine-o-quinone (DQ) in this present detection scheme. The fluorescence quenching follows the linear Stern-Volmer plot in the range 0-100 μM, establishing its efficacy as a fluorescence-based DA sensor with a limit of detection (LOD) 590 nM, which is ~27 fold lower than the lowest abnormal concentration of DA in serum (16 μM). This sensing scheme is also successively applied to trace DA in Brahmaputra river water sample with LOD 480 nM including its satisfactory recovery (95-112%). Our studies reveal a novel sensing pathway for DA through the core-shell structure formation and it is highly promising for the design of efficient biological and environmental sensor.
关键词： Dopamine,Fluorescence quenching,Nitrogen-doped graphene quantum dots,Colorimetric sensing,Core-shell structure,Gold nanoparticles
更新于2025-11-21 11:01:37
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Tunable Emission of Bluish Zn-Cu-Ga-S Quantum Dots by Mn Doping and their Electroluminescence
摘要： Based on bluish-emitting double-shelled quantum dots (QDs) of Zn?Cu?Ga?S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS:Mn) QDs exhibit a distinct Mn2+ 4T1?6A1 emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor-acceptor pair (DAP) recombinations. The relative contribution of Mn emission in the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration all QDs possess high PL quantum yield (QY) levels of 74?79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. When compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn2+ EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.
关键词： Tunable emission,Electroluminescence,Emission quenching,Zn?Cu?Ga?S quantum dots,Mn doping
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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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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Detection of Tetracycline in Water Using Glutathione-protected Fluorescent Gold Nanoclusters
摘要： Tetracycline (Tc), a widely used antibiotic, is one of the major pollutants in water. Herein, glutathione (GSH)-protected Au nanoclusters (GSH-AuNCs) were prepared to detect Tc. The fluorescence quenching ratio of GSH-AuNCs shows an excellent linear response against tetracycline in the concentration range of 50 μg/L – 50 mg/L with the detection limit of 5.31 μg/L. For the test paper prepared by GSH-AuNCs, 1 mg/L Tc caused a significant difference that could be recognized by the naked eye. The method exhibited good selectivity and excellent recovery when applied to a tap water sample. The method has the potential for Tc detection in real samples.
关键词： tetracycline detection,Au nanocluster,glutathione,recovery experiment,quenching ratio
更新于2025-11-19 16:56:35
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The Application of Green-Synthesis-Derived Carbon Quantum Dots to Bioimaging and the Analysis of Mercury(II)
摘要： Ginkgo leaves were used as precursors for the hydrothermal synthesis of carbon quantum dots (CQDs), which were subsequently characterized by transmission electron microscopy as well as Fourier-transform infrared, X-ray powder di?raction, and X-ray photoelectron spectroscopy. The prepared CQDs exhibited a ?uorescence quantum yield of 11% and superior water solubility and ?uorescence stability, as well as low cytotoxicities and excellent biocompatibilities with A549 and HeLa cells; these CQDs were also used to bioimage HeLa cells. Moreover, owing to the experimental observation that Hg2+ quenches the ?uorescence of the CQDs in a speci?c and sensitive manner, we developed a method for the detection of Hg2+ using this ?uorescence sensor. The sensor exhibited a linear range for Hg2+ of 0.50–20 μM, with an excellent coe?cient of determination (R2 ? 0.9966) and limit of detection (12.4 nM). In practice, the proposed method was shown to be highly selective and sensitive for the monitoring of Hg2+ in lake water and serum samples.
关键词： mercury(II) detection,carbon quantum dots,hydrothermal synthesis,fluorescence quenching,bioimaging
更新于2025-11-19 16:46:39
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A novel fluorescent probe for H2O2 detection based on CdSe@ZnS quantum dots/Ag nanocluster hybrid
摘要： The selective and quantitative detection of H2O2 is important for its employment in physiological, environmental and industrial applications. In this paper, a sensitive and selective strategy for H2O2 detection was established based on the fluorescence quenching of CdSe@ZnS quantum dots (QDs) by H2O2-mediated etching process of Ag nanoclusters (AgNCs). In this strategy, dihydrolipoic acid (DHLA) modified AgNCs were applied as H2O2 response group, the existence of H2O2 could initiate the oxidation of AgNCs and the production of Ag+, which could give rise to the effective fluorescence quenching of CdSe@ZnS QDs. Based on this strategy, the present fluorescent assay could realize the quantificational detection of H2O2 and the limit of detection is calculated to be 0.3 mM under the optimum conditions. Furthermore, CdSe@ZnS/AgNCs hybrid-based probe was applied to detecting H2O2 in milk samples and showed a good recoveries results ranged from 95.8% to 112.0%, meaning the potential applicability of this strategy.
关键词： H2O2 detection,Ag nanoclusters,Fluorescence quenching,CdSe@ZnS quantum dots
更新于2025-11-19 16:46:39
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Homogeneous immunoassay for alpha-fetoprotein based on the quenching of the fluorescence of quantum dots by antibody labelled with complexed copper ion tags
摘要： A homogeneous fluorescent immunoassay is described for the determination of alpha fetoprotein (AFP) relying on the interaction between copper ion complex and quantum dots (QDs). The copper ion complex-labelled antibody can be employed as a quencher of fluorescence of QDs and capture probe of AFP in homogeneous solution. The labelled antibody is mixed with QDs to form the immune ensemble probe. Upon the addition of AFP, the labelled antibody is stripped away from QDs by antigen-antibody combination leading to the increase in the fluorescence signal. Thus, the determination of AFP can be realized by fluorometry (best measured at excitation/emission wavelengths of 360/520 nm). The fluorescence intensity shows a good linear relationship with the AFP concentration ranging from 40 to 640 ng mL?1, and the LOD is 26 ng mL?1. The proposed method provides a new approach to incorporate metal complexes into QD-based biomolecule sensing.
关键词： Stern-Volmer plot,Metal complex,DTPAA,Copper ion complex-labelled antibody,Fluorescence quenching
更新于2025-11-19 16:46:39