Guangjun Zhou

Study on the Fluorescence Characteristics of Alkaline Degradation of Cefadroxil, Cephradine, Cefotaximum Sodium and Amoxicillini

Abstract A simple and sensitive fluorescence method for cefadroxil, cephradine, cefotaximum and amoxicillini is described. The method is based on their degradation under alkaline condition producing fluorescence products. The factors affecting the degradation and the determination were studied in detail. Under optimum conditions a linear relationship was obtained between the concentration of the antibiotics and the fluorescence intensity. The linear ranges of cefadroxil, cephradine, sodium cefotaximum and amoxicillini were 2.5x10−5 ~ 4.0x10−3 mg/ml, 4.0x10−5~4.0x10−3 mg/ml, 2.0x10−5 ~ 4.0x10−3 mg/ml and 8.0x10−5 ~ 4.0x10−3 mg/ml, respectively. Their detection limits (S/N=2) were 5.0x10−6 mg/ml, 8.0x10−6 mg/ml, 2.0x10−6 mg/ml and 7.5x10−6 mg/ml, respectively. The proposed method has been applied to the determination of cephalosporins and amoxicillini in human serum, urine and pharmaceutical formulations with satisfactory results.

Energy transfer from Bi3+ to Ho3+ triggers brilliant single green light emission in LaNbTiO6:Ho3+, Bi3+ phosphors

Excitation of Ho3+ and Bi3+ co-doped LaNbTiO6 particles with 453 nm blue light gave an intense single green glow. All the phosphors were synthesized via a facile sol–gel and combustion approach, and the crystal structure, particle morphology, photoluminescence (PL) properties of the phosphors and energy transfer between Bi3+ and Ho3+ were also investigated. The large spectral overlap between the broad emission band of Bi3+ around 425–570 nm and the excitation band of Ho3+ supports the efficient energy transfer from Bi3+ to Ho3+, which enhances the PL intensity remarkably. When the PL intensity is considered, the best composition for producing green light is LaNbTiO6:4 mol% Ho3+, 2 mol% Bi3+. The luminescence mechanisms of Ho3+ doped and Ho3+/Bi3+ co-doped in the LaNbTiO6 host were also discussed.

Study on the co-luminescence effect of Eu-Gd-BM-DPG-Triton X-100 system and its application to the determination of europium

Abstract The Eu-benzoylacetone (BM)-diphenylguanide(DPG)-Triton X-100 system, which has a strong fluorescence intensity, was studied. It was found that the fluorescence intensity can be greatly enhanced by Gd 3+ . The experiment showed that the fluorescence intensity of the system was a maximum under the following conditions: pH = 8.3 and the concentrations of Gd 3+ , BM and DPG were 5.0 × 10 −5 , 1.0 × 10 −3 and 7.5 × 10 −4 mol l −1 , respectively. At the optimum conditions, a linear relationship was obtained between fluorescence intensity and Eu 3+ concentration in the range of 2.0 × 10 −10 −2.0 × 10 −7 mol l -1 . The detection limit was 4.0 × 10 −13 mol l −1 .

Enhanced anti-stocks luminescence in LaNbO4:Ln3+ (Ln3+ = Yb3+, Er3+/Ho3+/Tm3+) with abundant color

Lanthanide ion doped up-conversion luminescent (UCL) materials, which have the ability to convert near-infrared longer wavelength excitation light into shorter wavelength visible light, have recently drawn much attention. Now, a series of Ln3+ (Yb3+, Er3+/Ho3+/Tm3+) ions doped LaNbO4 (LNO) materials were prepared through a two-step route, including a facile sol–gel process and subsequent combustion. In our work, thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), up-conversion luminescence (UCL), energy level diagram, luminescent lifetimes and corresponding CIE were utilized to characterize the properties. A 980 nm laser was employed to excite Yb3+ ions to achieve the 2F7/2 → 2F5/2 transition, and the LNO:Yb3+,Er3+/Ho3+/Tm3+ samples exhibited intense green, yellowish-green and blue emission, respectively. Luminescent spectra at different powers demonstrated the two-photon absorption process; meanwhile, the corresponding energy transfer mechanisms from Yb3+ to Ln3+ and the emissions of Ln3+ under 980 nm laser excitation were described via an energy level diagram. Moreover, multicolor UCL emissions, the optimal intensities and corresponding mechanism were systematically explored via a suite of concentration spectra of different Ln3+ ions. At last, the decay lifetimes based on the concentration variation of Yb3+ ion demonstrated that the lifetimes are heavily influenced by Yb3+ ion.

High luminescent core–shell QDs based on noninjection synthesized CdSe QDs: observation of magic sized CdSe quantum dots

CdSe QDs have been synthesized via a noninjection approach using ODE as the solvent, Se powder and Cd(SA)2 as the raw materials. Under optimized conditions, magic-sized CdSe QDs were observed, which showed an uncommon continuous growth at low temperatures. The growth kinetics of the CdSe QDs was studied using UV-vis absorption and photoluminescence spectroscopy. The results indicate that the dissolution of Se powder limited the starting point and the rate of nanocrystal nucleation. Comparative studies validated that the growth of QDs in the noninjection synthesis approach showed distinctly different kinetic features from those synthesized by the traditional hot-injection route. In addition, the changes of the Cd/Se feed molar ratio primarily influence the nucleation moment of the QDs, thus they control the particle size. The as prepared CdSe QDs were of high quality with a photoluminescence quantum yield (PL QY) of 34%. After passivating with ZnS, the PL QY increased to 63%. Moreover, with an additional ZnSe transition layer between the ZnS shell and CdSe core, the QY reached as high as 74%, which was comparable with the QY of QDs obtained by the hot-injection route.

Mechanistic investigation on up and down conversion of Er3+ and Gd3+ co-doped YTiNbO6 phosphors

YTiNbO6 phosphors doped with Er3+, Gd3+ were synthesized via a facile sol–gel and combustion approach. The crystal structure and particle morphology were characterized and the phonon energy was investigated in detail. The up-conversion emission excited at 980 nm and down-conversion emission excited at 378 nm of Er3+ with different concentrations were analysed. They both have strong green emission peaks at 522 and 552 nm but the red emission peak at 668 nm only appears in the up-conversion. Furthermore, the Er3+ quenching concentration for up-conversion is higher than that for down-conversion because the up-conversion is a complex multiple stepwise process which includes energy transfer, phonon-assisted energy transfer and excited state absorption that can cover a wider range of Er3+ doping concentrations. Moreover, the influence of co-doped Gd3+ on the morphology and particle size was also explored. Gd3+ had a great effect on the up and down conversion emission intensity as well as the decay time of up-conversion by changing the structure distortion, vibration frequencies and surface defects.

Facile combustion synthesis of novel CaZrO3:Eu3+, Gd3+ red phosphor and remarkably enhanced photoluminescence by Gd3+ doping

A facile sol–gel combustion route was reported for the direct preparation of CaZrO3:Eu3+ and CaZrO3:Eu3+, Gd3+. The obtained deposits were characterized by XRD, TGA-DSC, SEM, EDS, PL measurements and microscope fluorescence. When the Gd3+ ions were introduced in this compound, the emissions of CaZrO3:Eu3+were remarkably enhanced. The emission spectrum of CaZrO3:Eu3+, Gd3+ nanocrystals exhibited a red shift compared with CaZrO3:Eu3+ samples. A new mechanism of the improved photoluminescent properties of Eu3+ by Gd3+ was investigated. The optimized phosphor CaZrO3:5%Eu3+, 2%Gd3+ could be considered an efficient red-emitting component for white lighting devices excited in the near-ultraviolet region.

Study on the fluorescence system of Tb-ATP-Phen for the determination of ATP

Abstract It was found that ATP could form a ternary complex with Tb3+ and Phen, which can emit the characteristic fluorescence of Tb3+. The experiment showed that the fluorescence intensity of the system was maxmium in the following conditions: pH of the solution is 7.2, the concentrations of Tb3+ and phenanthroline (Phen) are 2.0×10-5mol.L-1 and 2.0 × 10-4mol.L-1, respectively. At the optimum conditions, a linear relationship is obtained between the fluorescence intensity and ATP concentration in the range of 1.0×10-6—1.0×10-5mol.L-1. Traces of ATP in drugs (ATP disodium salt tablets) can be determined using the standard addition method. The luminescence mechanism of the system was discussed.

Color tunable up-conversion emission from ZrO2:Er3+,Yb3+ textile fibers

ZrO2:xEr3+,yYb3+ fibers (diameters of approximately 1 μm) with good flexibility and toughness were synthesized via electrospinning technology. The composition, morphology, and up-conversion photoluminescence properties of the fibers were investigated. The up-conversion photoluminescence mechanisms of ZrO2 fibers singly doped with Er3+ ions or co-doped with Er3+,Yb3+ ions are also discussed in detail, including decay curves, and lifetimes. The main mechanisms in ZrO2:xEr3+,yYb3+ fibers were energy transfer from Yb3+ to Er3+ and cross relaxation processes between Yb3+ and Er3+ or between adjacent Er3+ ions. When the concentration of Yb3+ was 4 mol%, emission intensity over the entire spectrum and lifetime of the 2H11/2/4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions in ZrO2:Er3+,Yb3+ fibers were maximized using 980 nm excitation light. When the concentration of Yb3+ was 20 mol%, pure red emission could be obtained. Different colors—green, yellow, and red—could be obtained with Er3+/Yb3+ concentrations. Given the chemical, thermal, and mechanical stability of zirconia, Er3+/Yb3+ co-doped ZrO2 up-conversion luminescence fibers may be an attractive choice for photonic materials.

Fabrication and enhanced photoluminescence properties of

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