- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Quantitative Understanding of the Ultra-Sensitive and Selective Detection of Dopamine using Graphene Oxide/WS2 Quantum Dot Hybrid
摘要： Herein, we report on the ultra-high sensitive and selective detection of dopamine (DA) at pico-molar level by a low cost sensing platform based on graphene oxide (GO) sheets anchored with tungsten disulfide quantum dots (WS2 QDs). The liquid phase exfoliated WS2 QDs are mostly bilayer type with an average particle size ~2.0 ± 0.3 nm, while the GO sheets are of few-layer thickness. The WS2 QDs are highly luminescent with photoluminescence (PL) quantum yield of ~15% and they exhibit excitation wavelength dependent spectral shift in PL due to the high degree of edge/defect states. In presence of GO, the PL intensity of WS2 QDs partially quenches due to van der Waals interaction and excited-state charge transfer from WS2 to GO. However, in the presence of DA, drastic quenching of PL occurs for WS2/GO hybrid and this enables selective detection of DA as low as 10 pM, which is the lowest among the reported values. We present a new model to quantitatively explain the GO mediated efficient charge transfer and unusual quenching of PL as a function of the DA concentration. Finally, the WS2/GO based sensor is utilized for the detection of DA in the river water and blood serum with a satisfactory recovery, which establishes its practical utility as an efficient environmental/biochemical sensor.
关键词： Fluorescence Quenching,Dopamine,Biosensor,Graphene Oxide,WS2 Quantum Dots
更新于2025-09-23 15:21:01
-
Nitrogen-doped graphene quantum dots prepared by electrolysis of nitrogen-doped nanomesh graphene for the fluorometric determination of ferric ions
摘要： Nitrogen-doped graphene quantum dots (N-GQDs) were synthesized by direct electrolysis of a carbon cloth electrode coated with nitrogen-doped nanomesh graphene (NG) in high yield (~ 25%). The N-GQDs emit intense blue fluorescence with a quantum yield (QY) of 10% ± 3%. Meanwhile, the N-GQDs are rich in hydroxyl, carboxyl, basic pyridinic nitrogen, and nitro groups, which are conducive to strengthen the interaction between N-GQDs and Fe3+ for highly sensitive determination of Fe3+ ions. Specifically, the determination for Fe3+ was conducted at different concentrations of N-GQD solution with a wide linear range of 10–1000 μM (150 μg·mL?1) and a low detection limit of 0.19 μM (10 μg·mL?1). Moreover, the fluorescence quenching mechanism illustrated that the functional groups generated by electrochemical oxidation enhanced the interaction of N-GQDs and Fe3+, and the narrow band gap (2.83 eV) of N-GQDs accomplished electron transfer from N-GQDs to Fe3+ easily.
关键词： Fluorescence lifetime,Band gap,Dynamic quenching,Carbon cloth electrode,Electrochemical oxidation
更新于2025-09-23 15:21:01
-
Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption
摘要： Graphene quantum dots (GQDs) are an allotrope of carbon with a planar surface amenable to functionalization and nanoscale dimensions that confer photoluminescence. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including optical biosensing and delivery. Towards this end, noncovalent functionalization offers a route to reversibly modify and preserve the pristine GQD substrate, however, a clear paradigm has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to GQD surfaces, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates ranging ~60-fold in oxidation level, then investigating noncovalent polymer association to these substrates. Adsorption of ssDNA quenches intrinsic GQD fluorescence by 31.5% for low-oxidation GQDs and enables aqueous dispersion of otherwise insoluble no-oxidation GQDs. ssDNA-GQD complexation is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. Finally, we reveal the generality of the adsorption platform and assess how the GQD system is tunable by modifying polymer sequence and type.
关键词： molecular dynamics simulations,Graphene quantum dots,oxidation level,ssDNA,adsorption,noncovalent functionalization,fluorescence quenching
更新于2025-09-23 15:21:01
-
Fluorometric determination of morphine via its effect on the quenching of fluorescein by gold nanoparticles through a surface energy transfer process
摘要： A method is described for sensitive and selective fluorometric determination of morphine. It is based on the effect of morphine on quenching of the fluorescence of fluorescein by gold nanoparticles (AuNPs) via surface energy transfer. When fluorescein is added to solutions of colloidal AuNPs, its fluorescence becomes quenched due to nanometal surface energy transfer (NSET) because the absorption of AuNPs strongly overlaps the emission spectrum of fluorescein. In the presence of morphine, which contains both a tertiary nitrogen ring atom and a phenolic hydroxy group, it will coordinate to the AuNPs, and this causes recovery of fluorescence. The presence of a tertiary nitrogen ring atom and a phenolic hydroxy group (both required for the effect to occur) in morphine make the probe highly selective and sensitive for morphine. A paper strip assay also was developed by utilizing this detection scheme. The turn-on fluorescent probe was successfully applied to the determination of morphine in spiked serum and urine samples. The method has a 53 pM limit of detection. The paper strip was applied to the determination of morphine in sweat, urine and other biological fluids. It is perceived to be useful for early detection of drug abuse by adolescent.
关键词： Dynamic quenching,Neurotransmitter,Anesthetic drug,Paper-strip assay,Surface plasmon resonance,Stern-Volmer plot
更新于2025-09-23 15:21:01
-
Optimisation of a high-throughput fluorescamine assay for detection of N-acyl-L-homoserine lactone acylase activity
摘要： N-acyl-L-homoserine lactone (AHL) acylases are a well-known group of enzymes that disrupt quorum sensing in Gram-negative bacteria by degrading AHL signalling molecules. This degradation of signalling molecules (termed 'quorum quenching') has potential uses in the prevention or reduction of biofilm formation and/or bacterial infections. Therefore, there is a great deal of interest in the identification and characterisation of quorum quenching enzymes. Here, we present an optimised fluorescamine-based assay for the detection of AHL acylase activity and demonstrate it can be used in a high-throughput screening format.
关键词： Fluorescamine,Quorum quenching,Fluorescence,High-throughput,AHL acylase
更新于2025-09-23 15:21:01
-
Ultrasensitive Detection of MicroRNA with a Bismuthene-enabled Fluorescence Quenching Biosensor
摘要： Bismuthene, a monoelemental two-dimensional material, has shown promise in the biomedicine, electronic, and energy fields due to its high carrier mobility and stability at room temperature. However, its use in biosensing applications is restricted due to the undefined quenching mechanism for dye molecules. Herein, we develop a novel ultrathin bismuthene-based sensing platform for microRNA (miRNA)-specific detection that even discriminates single-base mismatches. The detection limit can reach 60 pM. Excitingly, the fluorescence quenching mechanism of bismuthene, ground state weakly fluorescent charge transfer, is determined via femtosecond pump-probe spectroscopy. This finding provides a proof-of-concept platform to i) fundamentally explore the quenching mechanism of bismuthene and ii) sensitively detect miRNA molecules for early cancer.
关键词： biosensor,Bismuthene,microRNA,charge transfer,fluorescence quenching
更新于2025-09-23 15:21:01
-
Oligonucleotide Detection and Optical Measurement with Graphene Oxide in the Presence of Bovine Serum Albumin Enabled by Use of Surfactants and Salts
摘要： As graphene oxide-based oligonucleotide biosensors improve, there is a growing need to explore their ability to retain high sensitivity for low target concentrations in the context of biological fluids. Therefore, we innovatively combined assay milieu factors that could influence the key performance parameters of DNA hybridization and graphene oxide (GO) colloid dispersion, verifying their suitability to enhance oligonucleotide–GO interactions and biosensor performance. As a model system, we tested single-strand (ss) DNA detection in a complex solution containing bovine serum albumin (BSA) and salts with surfactants. A fluorescein conjugated 30-mer oligonucleotide ssDNA probe was combined with its complementary cDNA target, together with solute dispersed GO and either non-ionic (Triton X-100 and Tween-20) or anionic sodium dodecyl sulfate (SDS) surfactants. In this context, we compared the effect of divalent Mg2+ or monovalent Na+ salts on GO binding for the quench-based detection of specific target–probe DNA hybridization. GO biosensor strategies for quench-based DNA detection include a “turn on” enhancement of fluorescence upon target–probe interaction versus a “turn off” decreased fluorescence for the GO-bound probe. We found that the sensitive and specific detection of low concentrations of oligonucleotide target was best achieved using a strategy that involved target–probe DNA hybridization in the solution with a subsequent modified “turn-off” GO capture and the quenching of the unhybridized probe. Using carefully formulated assay procedures that prevented GO aggregation, the preferential binding and quenching of the unhybridized probe were both achieved using 0.1% BSA, 0.065% SDS and 6 mM NaCl. This resulted in the sensitive measurement of the specific target–probe complexes remaining in the solution. The fluorescein-conjugated single stranded probe (FAM–ssDNA) exhibited linearity to cDNA hybridization with concentrations in the range of 1–8 nM, with a limit of detection equivalent to 0.1 pmoles of target in 100 μL of assay mix. We highlight a general approach that may be adopted for oligonucleotide target detection within complex solutions.
关键词： graphene oxide,optical DNA sensor,surfactants,fluorescence quenching
更新于2025-09-23 15:21:01
-
Determination of aminophylline based on fluorescence quenching of amino-functionalized graphene quantum dots induced by photoilluminated riboflavin-aminophylline system
摘要： A new method based on fluorescence spectroscopy for the sensitive determination of aminophylline (AP), an antiasthmatic drug, was developed in this work. Amino-functionalized graphene quantum dots (afGQDs) were synthesized based on a two-step method and they were characterized by transmission electron microscope, UV–vis absorption spectrum and infrared spectrum. The fluorescence of afGQDs was quenched by riboflavin (Rf) via both dynamic quenching and inner filter effect. Photoilluminated Rf-AP system in the presence of oxygen produced hydroxyl radicals (?OH). The latter accepted electrons from afGQDs owing to a photo-induced electron transfer process and led to the further fluorescence decline. The changing extent of the fluorescence intensity was found to be proportional to the concentration of AP in the range of 0.10–10 μg mL?1 and the limit of detection arrived at 40 ng mL?1. The proposed method was successfully employed for the determination of AP in a pharmaceutical sample and the recovery rate varied in the range of 99%–106%.
关键词： Riboflavin,Photoilluminated interaction,Amino-functionalized graphene quantum dots,Hydroxyl radicals,Aminophylline,Fluorescence quenching
更新于2025-09-23 15:21:01
-
Fe3+-selective and sensitive “on-off” fluorescence probe based on the graphitic carbon nitride nanosheets
摘要： An effective and facile “on-off” fluorescence sensing approach for the determination of Fe3+ ion using a large area and relatively uniform size graphitic carbon nitride nanosheets (GCNS) was developed. The prepared GCNS have blue and stable emission, as well as excellent water dispersion, and were applied as an effective fluorescent probe that based on the quenched fluorescence for selective and sensitive detection of Fe3+ ion. Herein, we explain the ambiguous fluorescence quenching mechanism between the GCNS and Fe3+, which mainly springs from the redox potential and empty d orbital of Fe3+. The redox potential and unfilled d orbit of Fe3+ endow it excellent binding force with GCNS, which generates most obvious fluorescence quenching effect with respect to other metal ions. The limit of detection (LOD) for Fe3+ was found to be about 2.06 μM. Therefore, the prepared GCNS has the potential to be used as a fluorescent probe for detection.
关键词： nanosheets,fluorescence detection,g-C3N4,fluorescence quenching mechanism
更新于2025-09-23 15:21:01
-
-SiC
摘要： We investigate the quenching of the photoluminescence (PL) from the divacancy defect in 4H-SiC consisting of a nearest-neighbor silicon and carbon vacancies. The quenching occurs only when the PL is excited below certain photon energies (thresholds), which differ for the four different inequivalent divacancy configurations in 4H-SiC. An accurate theoretical ab initio calculation for the charge-transfer levels of the divacancy shows very good agreement between the position of the (0/?) level with respect to the conduction band for each divacancy configuration and the corresponding experimentally observed threshold, allowing us to associate the PL decay with conversion of the divacancy from neutral to negative charge state due to capture of electrons photoionized from other defects (traps) by the excitation. Electron paramagnetic resonance measurements are conducted in the dark and under excitation similar to that used in the PL experiments and shed light on the possible origin of traps in the different samples. A simple model built on this concept agrees well with the experimentally observed decay curves.
关键词： quenching,electron paramagnetic resonance,4H-SiC,divacancy,charge-transfer levels,photoluminescence
更新于2025-09-23 15:21:01