[Laser Induced Time-Resolved Fluorescence Spectroscopy Characteristics of Fluoranthene in Ethanol with Eanosecond Laser of 355 nm].

Polycyclic Aromatic Hydrocarbons (PAHs) have been widely investigated in environmental field, for most of them are mutagenic (carcinogenic, teratogenic, mutagenic). The influence of delay time and gate width on the time-resolved fluorescence spectroscopy of fluoranthene in ethanol was studied in this paper. Furthermore, laser induced time-resolved fluorescence spectroscopy of fluoranthene with different concentration were also researched. According to the results, fluorescence kinetics decay curves and fluorescence lifetime of fluoranthene matched. The research results showed that there was closely relationship between the fluorescence spectrum of fluoranthene and the delay time and gate width of detector. When the delay time was fixed, the fluorescence intensity of fluoranthene grew increased as the gate width increased. When the gate width was fixed, the fluorescence intensity of fluoranthene increased first and then decreased with the delay time increases. The process of the attenuation of fluorescence intensity of fluoranthene with time delay conformed to the exponential decay process. The stepwise dilution of fluoranthene ethanol solution was also studied. With increasing dilution, the fitting of fluoranthene fluorescence lifetime increased. The results of this paper can provide a technical basis for the detection of PAHs in the environment, due to the different characteristics of the fluorescent substance having fluorescence lifetime.

[Effect of Methanol-Water Mixture on Three-Dimensional Fluorescence Spectra of Carbaryl].

Extensive use of pesticides has a significant impact on the environment. Carbaryl, whose residues stay in the surface water, is one of the most widely used broad spectrum insecticides in agriculture. It is important to understand carbaryl spectral characteristics and detection methods. The characteristic of excitation-emission three-dimensional spectra of carbaryl is studied. By changing the concentration of methanol in methanol-water binary solvent, the impact of methanol-water mixture on three-dimensional fluorescence spectra of carbaryl is discussed. The results show that the characteristic excitation-emission spectra of carbaryl is single peak, the range of the excitation wavelength and emission wavelength are: 244~304 and 300~350 nm respectively, the maximum excitation/emission peak located at 280 and 335 nm. With increasing the content of methanol in methanol-water binary solvent mixture, there is no obviously spectra shift of three dimensional fluorescence spectra of carbaryl. However, the intensity of fluorescence is nonlinear dependent on the content of methanol, mainly due to the specific properties of binary mixed solvent.

[Outlier Detection of Time Series Three-Dimensional Fluorescence Spectroscopy].

The qualitative and quantitative analysis are often interfered by the outliers in time series three-dimensional fluorescence spectroscopy. In this work, an efficient outlier detection method is proposed by taking advantage of the characteristics in time dimension and the spectral dimension. Firstly, the wavelength points that are mostly the outliers are extracted by the variance in time dimension. Secondly, by the analysis of the existence styles of outliers and similarity score of any two samples, the cumulative similarity is introduced in spectral dimension. At last, fluorescence intensity at each wavelength of all samples is modified by the correction matrix in time dimension and the outlier detection is completed according the to cumulative similarity scores. The application of the correction matrix in time dimension not only improves the validity of the method but also reduces the computation by the choice of characteristics region in correction matrix. Numerical experiments show that the outliers can still be detected by the 50 percent of all points in spectral dimension.

[Analysis of three-dimensional fluorescence overlapping spectra using differential spectra and independent component analysis].

The analysis of multi-component three-dimensional fluorescence overlapping spectra is always very difficult. In view of the advantage of differential spectra and based on the calculation principle of two-dimensional differential spectra, the three-dimensional fluorescence spectra with both excitation and emission spectra is fully utilized. Firstly, the excitation differential spectra and emission differential spectra are respectively computed after unfolding the three-dimensional fluorescence spectra. Then the excitation differential spectra and emission differential spectra of the single component are obtained by analyzing the multicomponent differential spectra using independent component analysis. In this process, the use of cubic spline increases the data points of excitation spectra, and the roughness penalty smoothing reduces the noise of emission spectra which is beneficial for the computation of differential spectra. The similarity indices between the standard spectra and recovered spectra show that independent component analysis based on differential spectra is more suitable for the component recognition of three-dimensional fluorescence overlapping spectra.

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(+).

Application of excitation-emission matrix fluorescence combined with second-order calibration algorithm for the determination of five polycyclic aromatic hydrocarbons simultaneously in drinking.

Direct determination of five polycyclic aromatic hydrocarbons including fluorene, anthracene, phenanthrene, pyrene and fluoranthene was accomplished by excitation-emission matrix fluorescence coupled with chemometric methods based on an alternating trilinear decomposition (ATLD) algorithm. A uniform design and orthogonal design are proposed for the creation of the calibration set. Results showed that no significant difference in the recoveries for each of the PAHs was observed. Thus, both of the designs can be used for the calibration set. In addition, some statistical parameters and figures of merit, such as average recovery, root-mean-square error of prediction, sensitivity, and selectivity were investigated to evalute the performance of the proposed method. The results showed that fluoranthene was the most selective, whereas fluorene was more sensitive than any other compound. This method was also employed for the determination of samples of drinking water spiked with all these PAHs. It can be observed that the results were not as satisfying as those in synthetic samples due to the negative effects of humic acid or fulvic acid in drinking water.