共查询到20条相似文献,搜索用时 46 毫秒
1.
Near infrared (NIR) emitting semiconductor quantum dots can be excellent fluorescent nanoprobes, but the poor biodegradability and potential toxicity limits their application. The authors describe a fluorescent system composed of graphene quantum dots (GQDs) as NIR emitters, and novel MnO2 nanoflowers as the fluorescence quenchers. The system is shown to be an activatable and biodegradable fluorescent nanoprobe for the “turn-on” detection of intracellular glutathione (GSH). The MnO2-GQDs nanoprobe is obtained by adsorbing GQDs onto the surface of MnO2 nanoflowers through electrostatic interaction. This results in the quenching of the NIR fluorescence of the GQDs. In the presence of GSH, the MnO2-GQDs nanoprobe is degraded and releases Mn2+ and free GQDs, respectively. This gives rise to increased fluorescence. The nanoprobe displays high sensitivity to GSH and with a 2.8 μM detection limit. It integrates the advantages of NIR fluorescence and biodegradability, selectivity, biocompatibility and membrane permeability. All this makes it a promising fluorescent nanoprobe for GSH and for cellular imaging of GSH as shown here for the case of MCF-7 cancer cells. 相似文献
2.
The authors describe a fluorometric glucose assay that is based on the use of MnO2 nanosheets and copper nanoclusters (CuNCs) acting as nanoprobes. The CuNCs were synthesized by using bovine serum albumin as a template by chemical reduction of copper(II) sulfate. On addition of MnO2 nanosheets to a colloidal solution of CuNCs, the fluorescence of CuNCs (measured at excitation/emission wavelengths of 335/410 nm) is quenched. However, in the presence of enzymatically generated H2O2, the MnO2 nanosheets are reduced to form Mn(II) ions. As a result, fluorescence intensity recovers. The glucose assay is based on the enzymatic conversion of glucose by glucose oxidase to generate H2O2 and glucuronic acid. The calibration plot is linear in the 1 μM to 200 μM glucose concentration range, and the detection limit is 100 nM. The method was successfully applied to the determination of glucose in spiked human serum samples. 相似文献
3.
The authors report that carbon nitride quantum dots (CN QDs) exert a strong enhancing effect on the Cu(II)/H2O2 chemiluminescent system. Chemiluminescence (CL) intensity is enhanced by CN QDs by a factor of ~75, while other carbon nanomaterials have a much weaker effect. The possible mechanism of the effect was evaluated by recording fluorescence and CL spectra and by examining the effect of various radical scavengers. Emitting species was found to be excited-state CN QDs that produce green CL peaking at 515 nm. The new CL system was applied to the sensitive detection of H2O2 and glucose (via glucose oxidase-catalyzed formation of H2O2) with detection limits (3σ) of 10 nM for H2O2 and 100 nM for glucose. The probe was employed for glucose determination in human plasma samples with satisfactory results. 相似文献
4.
Félicité?Pacifique?Mutuyimana Juanjuan?Liu Min?Na Stanislas?Nsanzamahoro Zhi?Rao Hongli?Chen Xingguo?Chen
The authors describe a method for the preparation of orange-red emissive carbon dots (CDs) with excitation/emission peaks at 520/582 nm. The CDs were hydrothermally prepared by a one-pot strategy from trimesic acid and 4-aminoacetanilide. The fluorescence of the CDs is strongly quenched by hydrogen peroxide. The oxidation of glucose by glucose oxidase (GOx) produces H2O2 that quenches the fluorescence via static quenching. Based on this phenomenon, a fluorometric method was established for the determination of glucose. Under the optimum conditions, response is linear in the 0.5 to 100 μM glucose concentration range, with a 0.33 μM limit of detection. The method is selective for glucose over its analogues and was successfully applied to the determination of glucose in diluted human serum and in urine from diabetics and healthy individuals. Recoveries from spiked samples range from 98.7 to 102.5%. 相似文献
5.
The quenching of the fluorescence of carbon dots: A review on mechanisms and applications 总被引:1,自引:0,他引:1
Carbon dots (CDs) possess unique optical properties such as tunable photoluminescence (PL) and excitation dependent multicolor emission. The quenching and recovery of the fluorescence of CDs can be utilized for detecting analytes. The PL mechanisms of CDs have been discussed in previous articles, but the quenching mechanisms of CDs have not been summarized so far. Quenching mechanisms include static quenching, dynamic quenching, Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), surface energy transfer (SET), Dexter energy transfer (DET) and inner filter effect (IFE). Following an introduction, the review (with 88 refs.) first summarizes the various kinds of quenching mechanisms of CDs (including static quenching, dynamic quenching, FRET, PET and IFE), the principles of these quenching mechanisms, and the methods of distinguishing these quenching mechanisms. This is followed by an overview on applications of the various quenching mechanisms in detection and imaging. 相似文献
6.
A method is described for the determination of the activity of alkaline phosphatase (ALP). It is based on the reversible modulation of the fluorescence of WS2 quantum dots (QDs). The fluorescence of the QDs is quenched by Cr(VI) but restored by free ascorbic acid (AA). The detection scheme relies on the fact that ALP hydrolyzes the substrate ascorbic acid 2-phosphate to produce AA, and that enzymatically generated AA can restore the fluorescence of the QDs. The signal (best measured at excitation/emission peak wavelengths of 365/440 nm) increases linearly in the 0.5 to 10 U·L?1 ALP activity range, with a detection limit of 0.2 U·L?1. The method was applied to the determination of ALP activity in human serum samples and demonstrated satisfactory results. 相似文献
7.
A rapid and sensitive aptamer-based assay is described for kanamycin, a veterinary antibiotic with neurotoxic side effects. It is based on a novel FRET pair consisting of fluorescent carbon dots and layered MoS2. This donor-acceptor pair (operated at excitation/emission wavelengths of 380/440 nm) shows fluorescence recovery efficiencies reaching 93 %. By taking advantages of aptamer-induced fluorescence quenching and recovery, kanamycin can be quantified in the of 4–25 μM concentration range, with a detection limit of 1.1 μM. The method displays good specificity and was applied to the determination of kanamycin in spiked milk where it gave recoveries ranging from 85 % to 102 %, demonstrating that the method serves as a promising tool for the rapid detection of kanamycin in milk and other animal-derived foodstuff. 相似文献
8.
We report on a sensitive and selective fluorescent assay utilizing native carbon dots (CDs) as signal transducers. The optical probes 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) or 3,3′-diaminobenzidine (DAB) were employed as substrates of horseradish peroxidase (HRP). It was found that the corresponding oxidation products (ox-ABTS or ox-DAB) quench the fluorescence of CDs, mainly via photoinduced electron transfer in case of ox-ABTS, and via aggregation and inner filter effect in case of ox-DAB. By coupling with bienzyme (glucose oxidase and HRP)-mediated biocatalytic reactions, the method was applied to the determination of hydrogen peroxide and glucose. In case of ABTS as the substrate of HRP, a wide linear range (0.05 to 100 μM) and a very low detection limit (10 nM) for glucose were attained. The method was applied to the determination of glucose in human serum and the results were found to agree well with data provided by a local hospital. 相似文献
9.
A method is described for the fluorometric determination of hypochlorite. It is making use of molybdenum disulfide quantum dots (MoS2 QDs) as a fluorescent probe. The QDs are prepared by hydrothermal reaction of sodium molybdate with glutathione. They possess diameters typically ranging from 1.4 to 3.8 nm, excellent stability in water, and blue photoluminescence (with excitation/emission peaks located at 315/412 nm and a quantum yield of 3.7%). The fluorescence of the QDs is statically quenched by hypochlorite, and the Stern-Volmer plot is linear. Hypochlorite can be detected in the 5–500 μM concentration range with a 0.5 μM detection limit. The method has been successfully applied to the determination of hypochlorite in spiked samples of tap water, lake water, and commercial disinfectants. 相似文献
10.
The authors describe a new chemiluminescence (CL) system composed of Si-doped carbon dots (Si-CDs), Fe(II) ions, and K2S2O8. The Si-CDs were prepared by a hydrothermal method and characterized by fluorescence spectra, transmission electron microscopy, energy-dispersive X-ray and FTIR spectroscopy. The weak CL of the Fe(II)-K2S2O8 reaction is found to be intensified by a factor of ~125 in the presence of Si-CDs. The possible mechanism for CL and its enhancement was studied by recording fluorescence and CL spectra and by investigating the effect of some radical scavengers. It is found that norfloxacin exerts a strong enhancing effect on the CL intensity of the system. This finding was employed to design a CL-based norfloxacin assay that works in the 5.0 to 300 μg L?1 concentration range, with a limit of detection (3 σ) of 1.5 μg L?1. The method was applied to the determination of therapeutic levels of norfloxacin in spiked human plasma and gave satisfactory results. 相似文献
11.
Yueyue?Song Guanhong?Xu Fangdi?Wei Yao?Cen Muhammad?Sohail Menglan?Shi Xiaoman?Xu Yunsu?Ma Yujie?Ma Qin?Hu
The authors describe an aptamer-based fluorescent assay for adenosine (Ade). It is based on the interaction between silver nanoparticles (AgNPs) and CdTe quantum dots (QDs). The beacon comprises a pair of aptamers, one conjugated to Fe3O4 magnetic nanoparticles, the other to AgNPs. In the presence of Ade, structural folding and sandwich association of the two attachments takes place. After magnetic separation, the associated sandwich structures are exposed to the QDs. The AgNPs in sandwich structures act as the signaling label of Ade by quenching the fluorescence of QDs (at excitation/emission wavelengths of 370/565 nm) via inner filter effect, electron transfer and trapping processes. As a result, the fluorescence of QDs drops with increasing Ade concentration. The assay has a linear response in the 0.1 nM to 30 nM Ade concentration range and a 60 pM limit of detection. The assay only takes 40 min which is the shortest among the aptamer-based methods ever reported. The method was successfully applied to the detection of Ade in spiked biological samples and satisfactory recoveries were obtained. 相似文献
12.
Wenjie Tang Yan Wang Panpan Wang Junwei Di Jianping Yang Ying Wu 《Mikrochimica acta》2016,183(9):2571-2578
This article reports on the synthesis of water dispersible carbon quantum dots (CDs) by a one-step hydrothermal method using polyamidoamine (PAMAM) and (3-aminopropyl)triethoxysilane (APTES) as a platform and passivant. The resulting CDs are highly uniform and finely dispersed. The synergistic effect between PAMAM and APTES on the surface of the CDs results in a fluorescence that is much brighter than that of CDs modified with either APTES or PAMAM only. The fluorescence of the co-modified CDs is quenched by Hg(II) ions at fairly low concentrations. Under the optimum conditions, the intensity of quenched fluorescence drops with Hg(II) concentration in the range from 0.2 nM to 10 μM, and the detection limit is 87 fM. The effect of potentially interfering cations on the fluorescence revealed a high selectivity for Hg2+. The fluorescent probe was applied to the determination of Hg(II) in (spiked) waters and milk and gave recoveries between 95.6 and 107 %, with relative standard deviation between 4.4 and 6.0 %. 相似文献
13.
The authors describe the synthesis of a multifunctional nanocomposite with an architecture of type Fe3O4@SiO2@graphene quantum dots with an average diameter of about 22 nm. The graphene quantum dots (GQDs) were covalently immobilized on the surface of silica-coated magnetite nanospheres via covalent linkage to surface amino groups. The nanocomposite displays a strong fluorescence (with excitation/emission peaks at 330/420 nm) that is fairly selectively quenched by Hg2+ ions, presumably due to nonradiative electron/hole recombination annihilation. Under the optimized experimental conditions, the linear response to Hg2+ covers the 0.1 to 70 μM concentration range, with a 30 nM lower detection limit. The high specific surface area and abundant binding sites of the GQDs result in a good adsorption capacity for Hg2+ (68 mg?g?1). The material, due to its superparamagnetism, can be separated by using a magnet and also is recyclable with EDTA so that it can be repeatedly used for simultaneous detection and removal of Hg2+ from contaminated water. 相似文献
14.
Hetero-dimeric magnetic nanoparticles of the type Au-Fe3O4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods. 相似文献
15.
Cobalt oxyhydroxide (CoOOH) nanosheets are efficient fluorescence quenchers due to their specific optical properties and high surface area. The combination of CoOOH nanosheets and carbon dots (CDs) has not been used in any aptasensor based on fluorescence quenching so far. An aptamer based fluorometric assay is introduced that is making use of fluorescent CDs conjugated to the aptamer against methamphetamine (MTA), and of CoOOH nanosheets which reduce the fluorescence of the CDs as a quencher. The results revealed that the conjugated CDs with aptamers were able to enclose the CoOOH nanosheets. Consequently, fluorescence is quenched. If the aptamer on the CD binds MTA, the CDs are detached from CoOOH nanosheets. As a result, fluorescence is restored proportionally to zhe MTA concentration. The fluorometric limit of detection is 1 nM with a dynamic range from 5 to 156 nM. The method was validated by comparing the results obtained by the new method to those obtained by ion mobility spectroscopy. Theoretical studies showed that the distance between CoOOH nanosheet and C-Ds is approximately 7.6 Å which can illustrate the possibility of FRET phenomenon. The interactions of MTA and the aptamer were investigated using molecular dynamic simulation (MDS). 相似文献
16.
A composite material obtained by ultrasonication of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) was loaded with manganese dioxide (MnO2), poly(diallyldimethylammonium chloride) and gold nanoparticles (AuNPs), and the resulting multilayer hybrid films were deposited on a glassy carbon electrode (GCE). The microstructure, composition and electrochemical behavior of the composite and the modified GCE were characterized by transmission electron microscopy, Raman spectra, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The electrode induces efficient electrocatalytic oxidation of dopamine at a rather low working voltage of 0.22 V (vs. SCE) at neutral pH values. The response is linear in the 0.5 μM to 2.5 mM concentration range, the sensitivity is 233.4 μA·mM ̄1·cm ̄2, and the detection limit is 0.17 μM at an SNR of 3. The sensor is well reproducible and stable. It displays high selectivity over ascorbic acid, uric acid and glucose even if these are present in comparable concentrations. 相似文献
17.
A novel photoelectrochemical (PEC) aptasensor with graphitic-phase carbon nitride quantum dots (g-C3N4; QDs) and reduced graphene oxide (rGO) was fabricated. The g-C3N4 QDs possess enhanced emission quantum yield (with an emission peak at 450 nm), improved charge separation ability and effective optical absorption, while rGO has excellent electron transfer capability. Altogether, this results in improved PEC performance. The method is making use of an aptamer against sulfadimethoxine (SDM) that was immobilized on electrode through π stacking interaction. Changes of the photocurrent occur because SDM as a photogenerated hole acceptor can further accelerate the separation of photoexcited carriers. Under optimized conditions and at an applied potential of +0.2 V, the aptasensor has a linear response in the 0.5 nM to 80 nM SDM concentration range, with a 0.1 nM detection limit (at S/N =?3). The method was successfully applied to the analysis of SDM in tap, lake and waste water samples. 相似文献
18.
An electrochemical approach is introduced for synthesis of carbon dots (CDs) by exfoliating graphite rods at a voltage of 15 V in an electrolyte consisting of a mixture of water and two ionic liquids. It is found that the size of the CDs can be tuned by varying the fraction of water in the mixed electrolyte; CDs in sizes of 4.9, 4.1 and 3.1 nm are obtained if the electrolyte contains water in fractions of 24, 38 and 56 %, respectively. The CDs have a quantum yield of almost 10 % and display the typical excitation wavelength-dependent maxima of photoluminescence, strongest at excitation/emission wavelengths of 360/440 nm. Fourier transform infrared and X-ray photoelectron spectroscopy show the CDs to have oxygen functional groups on their surface which strongly improve solubility. The CDs were applied to image cells of the electricity-producing bacteria Shewanellaoneidensis MR-1. 相似文献
19.
The authors describe a sensitive method for determination of glutathione (GSH) that is based on a thiol-triggered inner filter effect on the fluorescence of N-doped carbon dots (N-doped CDs). N-doped CDs with a quantum yield as high as 31% were prepared by a one-pot procedure, and 5,5′-dithiobis-(2-nitrobenzoic acid) was employed as a reagent for GSH recognition. The reaction product (5-thio-2-nitrobenzoic acid; TNB) acts as an absorber of the 410-nm light used to photo-excite the N-doped CDs. Hence, the fluorescence of N-doped CDs (peaking at 510 nm) is reduced with increasing concentrations of GSH. As little as 30 nM of GSH can be detected by this method. The approach was successfully applied to (a) food analysis, (b) an investigation of an oxidative stress model, and (c) to live cells imaging. The method does not require the surface of N-doped CDs to be chemically modified, and a linkage between receptor and fluorophore is not needed. In our perception, the method may become a viable tool for the detection and imaging of thiols. 相似文献
20.
Graphite-like carbon nitride ? Fe3O4 magnetic nanocomposites were synthesized by a chemical co-precipitation method. The nanocomposites were characterized by transmission electron microscopy, X-ray diffraction, FTIR spectroscopy, X-ray photoelectron spectroscopy and magnetization hysteresis loops. The nanocomposites exhibit enhanced peroxidase-like activity (compared to that of graphite-like carbon nitride or Fe3O4 NPs). More specifically, they are capable of catalyzing the oxidation of different peroxidase substrates (such as TMB, ABTS or OPD) by H2O2 to produce the typical color reactions (blue, green or orange). The nanocomposites retain their magnetic properties and can be separated by an external magnet. On the basis of these findings, a highly sensitive and selective method was applied to the determination of H2O2 and glucose (by using glucose oxidase). It was successfully applied to the determination of glucose in (spiked) human serum. Compared to other nanomaterial-based peroxidase mimetics, the one described here provides distinctly higher sensitivity for both H2O2 and glucose, with detection limits as low as 0.3 μM and 0.25 μM, respectively. 相似文献