Jingbo Duan

Hydrothermal synthetic mercaptopropionic acid stabled CdTe quantum dots as fluorescent probes for detection of Ag

Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) with particle size 3 nm have been successfully synthesized in aqueous medium by hydrothermal synthesis method. And the effects of different metal ions on MPA capped CdTe QDs fluorescence were studied using fluorescence spectrometry. The results demonstrated that at the same concentration level, Ag(+) could strongly quench CdTe QDs fluorescence, and the other metal ions had little effect on CdTe QDs fluorescence except Cu(2+). On the basis of this fact, a rapid, simple, highly sensitive and selective method based on fluorescence quenching principle for Ag(+) detection in aqueous solution was proposed. Under optimal conditions, the quenched fluorescence intensity (F(0)-F) increased linearly with the concentration of Ag(+) ranging from 4 × 10(-7) to 32 × 10(-7)mol L(-1). The limit of detection for Ag(+) was 4.106 × 10(-8)mol L(-1). The obtained plot of F(0)/F versus [Ag(+)] was an upward curvature, concave towards the y-axis, rather than a straight line. The modified form of the Stern-Volmer equation was third order in Ag(+) concentration. According to the modified Stern-Volmer equation, it can be inferred that dynamic quenching and static quenching simultaneously occurred when Ag(+) interacted with MPA capped CdTe QDs. At the same time other factors might also influence the quenching process. Based on this study, hydrothermal synthesized MPA capped CdTe QDs with particle size 3 nm may be used as a novel fluorescence probe to quantificationally and selectively detect Ag(+).

Analytic Method on Characteristic Parameters of Bacteria in Water by Multiwavelength Transmission Spectroscopy

An analytic method together with the Mie scattering theory and Beer-Lambert law is proposed for the characteristic parameter determination of bacterial cells (Escherichia coli 10389) from multiwavelength transmission spectroscopy measurements. We calculate the structural parameters of E. coli cells, and compared with the microscopy, the relative error of cell volume is 7.90%, the cell number is compared with those obtained by plate counting, the relative error is l.02%, and the nucleic content and protein content of single E. coli cells are consistent with the data reported elsewhere. The proposed method can obtain characteristic parameters of bacteria as an excellent candidate for the rapid detection and identification of bacteria in the water.

Measurement of Phytoplankton Photosynthesis under Different Habitats Using Variable Pulse Light Induced Fluorescence

The technique based on variable pulse light induced fluorescence was employed to measure the photosynthesis of phytoplankton under different nutrient, light, temperature conditions and growing periods. The validity of this technique was conformed.

New type of alga photosynthesis activity modulation fluorometer in situ

A developed in situ measuring system uses light emitted diodes (LED) and laser diodes(LD) as light sources is employed for the recording of algae chlorophyll fluorescence induction kinetics (Kautsky-effect). Photosynthesis activity as an important parameter is obtained in the system which measures the chlorophyll fluorescence yield. Minimal fluorescence is excited by the brief but really weak light pulses from LED as measure light while photosynthesis is happened, variable fluorescence which means there is energy conversion through photosynthesis is also excited by a LED but the beam is more stronger, LD induced saturation fluorescence stands for maximum fluorescence. The system could works for alga chlorophyll photosynthesis activity continuous measure in situ through efficiently mechanical and optical design.

Monitoring fluorescence quenching of polycyclic aromatic hydrocarbons by humic acid in water using fluorescence fingerprints

Fluorescence measurements on selected polycyclic aromatic hydrocarbons were performed to obtain the information about the fluorescence quenching of polycyclic aromatic hydrocarbons by humic acid. The fluorescence properties of pyrene and fluoranthene in the presence of humic acid in water were investigated by three dimensional excitation-emission matrix fluorescence spectroscopy. The pH influence on the fluorescence quenching of pyrene and fluoranthene were also investigated. For both pyrene and fluoranthene, the fluorescence quenching were dominated by static quenching processes. According to the result of the research, the effect of humic acid on the pyrene and fluoranthene can be calibrated in the water environment. The results show that three dimensional excitation-emission matrix fluorescence spectroscopy has great potential for the use of in-situ measurement of polynuclear aromatic compounds in water environment.

Simultaneous determination of Benzo(k)fluoranthene and Perylene using Excitation-Emission Matrix Fluorescence

Benzo[k]fluoranthene (BkF) and perylene (Per) are among the sixteen priority pollutants of polycyclic aromatic hydrocarbons recommended by The United States Environment Protection Agency (EPA). In this paper, we report a simple and rapid method for quantitative analysis of BkF and Per using the three-dimensional excitation-emission matrix (EEM) fluorescence coupled with parallel factor analysis (PARAFAC). Before analyzing of two mixtures quantitatively, we study the fluorescence characterization of pure BkF and Per first. The maximal peak values are at 306 nm of the excitation wavelength and 406 nm of the emission wavelength for BkF, and 252 and 438nm for Per, the linear ranges of BkF and Per are 0.8~16~ L-1 and 0.6~20~ L-1 respectively. Finally the average recoveries are obtained using PARAFAC algorithm, which can reach 101.1% and 99.5% for BkF and Per respectively. In order to evaluate the accuracy of the PARAFAC algorithm, selectivity (SEL) and sensitivity (SEN) have also been presented. Results show that a good performance has been achieved using excitation-emission fluorescence coupled with PARAFAC algorithm.