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We report a fluorescence resonance energy transfer (FRET) system in which the fluorescent donor is fluorescein isothiocyanate (FITC) dye and the fluorescent acceptor is CdTe quantum dot (QDs). Based on FRET quenching theory, we designed a method to detect the concentration of silver ions (Ag(+) ). The results revealed a good linear trend over Ag(+)...
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... Fig. 9, compared with pure FITC and CdTe QDs/PAH, the ab- sorption intensities of the donor and acceptor in the FITC-CdTe FRET system were both decreased. The absorption peak of FITC did not change significantly, but the absorption peak of the CdTe QDs/PAH shows an obvious red shift from 525 to 537 nm. This is due to the combination of donor ...
Context 2
... by the complexes. The dissociation process is very slow, and the complexes decay to the ground state by non-radiative transition. The performances of static quenching are that the fluorescence intensity is decreased and the absorption spectrum changes significantly, which is in contrast to the lifetime after addition of fluorescent quencher. In Fig. 9 (UV absorption spectrum of FITC-CdTe system), when the Ag + solution is added, the UV absorption of the resonance system remained almost unchanged, indicating that no complex was formed through inter- action between the resonance system and the Ag + solution, which showed that the process is not static quenching. The lifetime of the ...
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... Many substances have no fluorescence characteristics or weak signal and cannot be quantitatively analyzed by direct fluorescence method [20]. Therefore, some indirect fluorescence analysis methods were established. ...
A magnetic molecularly imprinted probe (MMIP@QD) was synthesized by reverse microemulsion method using CdTe QDs, Fe3O4, and molecularly imprinted polymer as the fluorophore, magnetic carrier, and recognition sites, respectively. The nanoparticle was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and vibrating sample magnetometry (VSM). In the optimal experimental condition, fluorescent emission intensity (measured at excitation wavelengths of 350 nm) was quenched linearly with increasing malachite green (MG) concentration from 0.8 to 28.0 μM with LOD of 0.67 μM. Simultaneously, it was observed that the maximum absorption wavelength was blue shifted gradually with the increase of MG concentration. The inner filter effect, static quenching, and band gap transition were interpreted as the mechanisms of fluorescence quenching and wavelength shift. Thermodynamic studies indicated that the quenching reaction proceeded spontaneously. The developed sensor was applied to detect MG in seawater samples. Satisfactory recoveries of MG in spiked seawater ranged from 83.6 to 122.1% with RSD < 1.8%.
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... According to the previous description (Feng et al. 2016b), multi-photon excitation wavelength selection may follow the following rules: Based on the empirical formula and spectral feature shown in Fig. 2, two wavelengths (~ 754 nm and ~ 1350 nm) were chosen for effective two-and three-photon excitation of these QDs. ...
In this study, we investigated the multi-photon excited fluorescence resonance energy transfer (FRET) between ZnSe and ZnSe:Mn quantum dots and Rhodamine 6G in aqueous solution. Two and three photon excited FRET was measured by ~ 50 fs laser pulses at wavelength of ~ 754 nm and ~ 1300 nm, respectively. The FRET efficiency of ZnSe:Mn-R6G system was about 1.5-fold higher than that of the ZnSe-R6G, which was associated with increase of Forster radius of the sample. In addition, FRET efficiency of ZnSe:Mn-R6G systems were up to 45% excited by two-photon. Our study contributed to the application of FRET in the biological and medical fields.
... Applications of various sizes of cadmium telluride QDs with a core diameter of 3.0-9.0 nm and emission range of 540-800 nm in radiological purposes such as fluorescence resonance energy transfer analysis (FRET) [71][72][73], fluorophores in gene technology [74], fluorescent labeling of cellular proteins [75], cell tracking [3,76], pathogen and toxin detection [77,78] and in vivo animal imaging [79] have been reported. Functionalization of these nanomaterials allows better surface functions as well as cell permeability [80]. ...
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... [21][22][23] The extent of FRET occurrence is usually expressed as FRET efficiency, i.e. the proportion of the photons absorbed by the donor that is transferred to the acceptor. 24 Due to the excellent nonlinear properties of QDs, the covalent linking of the QDs and ALA allow us to use the excitation wavelengths wherein the ALA alone couldn't achieved. The QDs-ALA conjugates have the optical advantages of quantum dots and the treatment efficacy of ALA, and they can overcome the weaknesses of QDs or ALA alone in cancer treatment. ...
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Quantum dots (QDs), commonly considered as semiconductor nanoparticle with sizes < 10 nm, recently have emerged as a highly studied field in material science due to their size dependent unique...
Silver nanoparticles can be used in antibacterial packaging or disinfection. Research has shown that sugary fluid induces the leaching of silver nanoparticles into water, which may be harmful to humans. Single wavelength fluorescence analysis has been used for quantitative analysis of silver nanoparticles but suffers from low specificity and poor anti-interference ability. In this paper, a ratiometric fluorescence sensor system (GCS) was used for the detection of Ag+, which realized both visual detection and quantitative analysis of silver in drinks. The color changes of GCS with different concentrations of Ag+ are distinguishable and easy to analyze. There is also a good linear relationship between the concentrations of Ag+ and varieties of F424 nm/F570 nm, and the lowest detection limit reached 0.2266 nmol/L. This GCS shows good selectivity and recovery and could be used for the detection of Ag+ in drink samples.
Luminescent metal-organic frameworks (LMOF) with ligand-modified are a promising strategy to be applied to fabricate chemical sensors. Herein, a novel Co (II) metal-organic framework (Co-MOF), namely Co [(NTB) bpy] (NTB = 4,4'4″-tricarboxylic acid triphenylamine, bpy = 4,4 '-bipyridyl), was successfully synthesized with excellent water stability and fluorescence properties. Due to the propeller structure of NTB ligands, a special topological structure of Co-MOF was shown: {24.416.68}{2}4. It was proved that Co-MOF has great stability by soaking in different solvents for two weeks. Remarkably, the fluorescence quenching experiment verified that Co-MOF has excellent fluorescence sensor performance. Trinitrophenol, 2,4-dinitrophenol, and 2-amino-4-nitrotoluene (10-5 M) with LOD of 9.00 × 10-5, 5.40 × 10-5 and 5.07 × 10-6 M can be detected via the process of fluorescence enhancement and quenching. Throughout the investigation, the mechanics of fluorescence quenching was performed. Due to the excellent UV absorption capacity of Co-MOF, it was a promising application to combine low-dimensional nanomaterials with sustainable biomass materials. A hybrid films of Co-MOF and cellulose acetate (CA) was generated. The hybrid films had highly transparency in the visible wavelength range and excellent UV-shielding ability owing to the CA/Co-MOF hybrid films enhanced the UV absorption capacity of Co-MOF.
With increasing demand for public security and environmental protection, it is highly desirable to develop strategies to identify trace explosives (e. g., 2,4,6‐trinitrotoluene (TNT)). Herein, we report novel photonic crystal (PC)‐based sensor chips for trace TNT detection by using amplification effect of PCs on fluorescence (FL) signals. The sensor chips are constructed by integrating silica nanoparticles (NPs) modified with (3‐aminopropyl)triethoxysilane (APTES) and fluorescein isothiocyanate isomer (FITC) and PC substrates. The amino groups on FITC‐APTES‐silica NPs can specifically bind with TNT molecules to form Meisenheimer complexes and strongly quench the FL signal of neighboring fluorophores FITC through Förster resonance energy transfer. PCs with matched PBG can amplify the FL signal of FITC‐APTES‐silica NPs about 24.4‐fold and significantly improve sensitivity and resolution of trace TNT detection with the limit of detection of 0.23 nM. The PC‐based sensor chips are stable, sensitive, and reliable TNT sensing platforms, showing great potential in homeland safety and environmental protection.
