Fluorescence Energy Transfer System Research Articles

Enhanced and broadened fluorescence of ZnSe quantum dots enabled by the fluorescence energy transfer system of ZnSe quantum dots and gold nanoparticles.

The enhanced and broadened fluorescence of ZnSe quantum dots (QDs) were studied by using a fluorescence energy transfer system (FETS) of ZnSe QDs and gold nanoparticles (NPs). The FETS were prepared via uniformly dispersing the gold nanoparticles into ZnSe QD solution in the condition of magnetic stirring. Enhanced and broadened fluorescence was observed on the film of the FETS due to the transfer of photo-generated carriers between the ZnSe QDs and the gold NPs, instead of the surface plasma resonance effect. The excitonic and enhanced fluorescence on the FETS film depended on the competition of electron-hole recombination and electron transfer from the ZnSe QDs to the gold NPs. In addition, because of the excitonic fluorescence of the ZnSe QDs absorbed by the gold NPs, the electrons of the s-p band of the gold NPs were further increased to facilitate its energy level shift toward the conduction band of the ZnSe QDs in order to create a blueshift in the enhanced fluorescence. This enhanced and broadened fluorescence method can be applied for controlling fluorescence in photoelectric detection, photodiodes, lightshows, and sensor devices.

半导体聚合物量子点-亚甲基蓝荧光能量转移体系测定水中Bi3+

半导体聚合物量子点-亚甲基蓝荧光能量转移体系测定水中Bi³⁺

Feasibility of fluorescence energy transfer system for imaging the renoprotective effects of aliskiren in diabetic mice.

Introduction:We investigated the feasibility of using a fluorescence resonance energy transfer system to image enzymatic activity in order to evaluate the effects of aliskiren (a direct renin inhibitor) on diabetic nephropathy.Materials and methods:First, we induced diabetes in C57BL/6J mice using streptozotocin, then treated them with either aliskiren (25 mg/kg/day) or the angiotensin type 1 receptor blocker valsartan (15 mg/kg/day) for four weeks. Finally, we utilized renin fluorescence resonance energy transfer substrate to assess renin activity.Results:Renin activity was much higher in the kidneys of diabetic mice compared to those of the non-diabetic control mice. While aliskiren inhibited this activity, valsartan did not. We noted that production of reactive oxygen species intensified and the bioavailability of nitric oxide diminished in the glomeruli of diabetic mice. Aliskiren and valsartan significantly ameliorated these effects. They suppressed glomerular production of reactive oxygen species and urinary albumin excretion. In fact, urinary albumin excretion in diabetic mice treated with aliskiren or valsartan was lower than that in untreated diabetic mice. Furthermore, aliskiren and valsartan significantly reduced glomerular permeability by maintaining the glomerular endothelial surface layer.Conclusion:Fluorescence resonance energy transfer could provide a new tool for evaluating tissue and plasma enzymatic activity.

Efficient fluorescence energy transfer system between fluorescein isothiocyanate and CdTe quantum dots for the detection of silver ions.

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(+) concentrations in the range 0.01-8.96 nmol/L, a range that was larger than with other methods; the quenching coefficient is 0.442. The FRET mechanism and physical mechanisms responsible for dynamic quenching are also discussed.

Efficient Fluorescence Energy Transfer System between CdTe-Doped Silica Nanoparticles and Gold Nanoparticles for Turn-On Fluorescence Detection of Melamine

We here report an efficient and enhanced fluorescence energy transfer system between confined quantum dots (QDs) by entrapping CdTe into the mesoporous silica shell (CdTe@SiO₂) as donors and gold nanoparticles (AuNPs) as acceptors. At pH 6.50, the CdTe@SiO₂-AuNPs assemblies coalesce to form larger clusters due to charge neutralization, leading to the fluorescence quenching of CdTe@SiO₂ as a result of energy transfer. As compared with the energy transfer system between unconfined CdTe and AuNPs, the maximum fluorescence quenching efficiency of the proposed system is improved by about 27.0%, and the quenching constant, K(sv), is increased by about 2.4-fold. The enhanced quenching effect largely turns off the fluorescence of CdTe@SiO₂ and provides an optimal "off-state" for sensitive "turn-on" assay. In the present study, upon addition of melamine, the weak fluorescence system of CdTe@SiO₂-AuNPs is enhanced due to the strong interactions between the amino group of melamine and the gold nanoparticles via covalent bond, leading to the release of AuNPs from the surfaces of CdTe@SiO₂; thus, its fluorescence is restored. A "turn-on" fluorimetric method for the detection of melamine is proposed based on the restored fluorescence of the system. Under the optimal conditions, the fluorescence enhanced efficiency shows a linear function against the melamine concentrations ranging from 7.5 × 10⁻⁹ to 3.5 × 10⁻⁷ M (i.e., 1.0-44 ppb). The analytical sensitivity is improved by about 50%, and the detection limit is decreased by 5.0-fold, as compared with the analytical results using the CdTe-AuNPs system. Moreover, the proposed method was successfully applied to the determination of melamine in real samples with excellent recoveries in the range from 97.4 to 104.1%. Such a fluorescence energy transfer system between confined QDs and AuNPs may pave a new way for designing chemo/biosensing.

Terbium (III) chelate complexes as fluorescence energy transfer donor in the determination of formaldehyde in aqueous solutions

The sensitized fluorescence intensity of the terbium (III) ion can be notably enhanced in the presence of sodium hexametaphosphate (SHMP). Based on this, water-soluble Tb-SHMP chelate complexes were synthesized in aqueous solutions, and characterized by spectrofluorometry. 6-Mercapto-5-triazole[4,3-b]-S-tetrazine was generated by the quantitative reaction of HCHO with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole under alkaline conditions at room temperature. The spectral overlap between the emission of Tb-SHMP chelate complexes and absorption of 6-mercapto-5-triazole[4,3-b]-S-tetrazine meets the prerequisite for fluorescence energy transfer. Based on this, a novel efficient fluorescence energy transfer system between Tb-SHMP chelate complexes as donor and 6-mercapto-5-triazole[4,3-b]-S-tetrazine as acceptor was developed for the determination of HCHO in aqueous solutions. Under the optimal experimental conditions, this method is capable of detecting HCHO concentrations from 2.06 × 10 −5 to 6.18 × 10 −3 mg mL −1 and the limit of detection was 7.11 × 10 −6 mg mL −1. Compared with other general methods for the determination of HCHO, the proposed method improved the sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of HCHO in water samples.

Ultrasensitive mercury(II) ion detection by europium(III)-doped cadmium sulfide composite nanoparticles

With the biomolecule glutathione (GSH) as a capping ligand, Eu 3+-doped cadmium sulfide composite nanoparticles were successfully synthesized through a straightforward one-pot process. An efficient fluorescence energy transfer system with CdS nanoparticles as energy donor and Eu 3+ ions as energy accepter was developed. As a result of specific interaction, the fluorescence intensity of Eu 3+-doped CdS nanoparticles is obviously reduced in the presence of Hg 2+. Moreover, the long fluorescent lifetime and large Stoke's shift of europium complex permit sensitive fluorescence detection. Under the optimal conditions, the fluorescence intensity of Eu 3+ at 614 nm decreased linearly with the concentration of Hg 2+ ranging from 10 nmol L −1 to 1500 nmol L −1, the limit of detection for Hg 2+ was 0.25 nmol L −1. In addition to high stability and reproducibility, the composite nanoparticles show a unique selectivity towards Hg 2+ ion with respect to common coexisting cations. Moreover, the developed method was applied to the detection of trace Hg 2+ in aqueous solutions. The probable mechanism of reaction between Eu 3+-doped CdS composite nanoparticles and Hg 2+ was also discussed.

Determination of formaldehyde in aqueous solutions by a novel fluorescence energy transfer system

An efficient fluorescence energy transfer (FET) system between CePO(4):Tb(3+) nanocrystals as donor and 6-mercapto-5-triazole[4,3-b]-S-tetrazine as acceptor was built. CePO(4):Tb(3+) nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy, electron diffraction pattern spectroscopy and spectrofluorometry. Under alkaline conditions, 6-mercapto-5-triazole[4,3-b]-S-tetrazine was generated by redox reaction of formaldehyde (HCHO) with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) at room temperature. The degree of the overlap was effective for FET between the emission spectrum of CePO(4):Tb(3+) and the absorption spectrum of 6-mercapto-5-triazole[4,3-b]-S-tetrazine. Based on this system, a simple and sensitive fluorescence method for the selective determination of formaldehyde in aqueous solutions was developed. Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of HCHO ranging from 1.03 x 10(-9) to 1.03 x 10(-5) mg mL(-1) with a correlation coefficient of 0.9976. The limit of detection was 1.65 x 10(-10) mg mL(-1). Compared with several methods, the proposed method had a wider linear range, higher selectivity and sensitivity. Moreover, analytical application of the method was demonstrated by water samples.