Abstract A series of polyesters PBSM, poly(butylene succinate-co-butylene methyl succinate), were obtained by direct melting polycondensation of succinate and methyl succinic acid with 1,4-butanediol. The compositions and physical properties of the resulted homopolyester and copolyesters were investigated by 1H NMR, differential scanning calorimetry(DSC)and X-ray diffraction. The results suggest that the introduction of comonomer containing a side-chain methyl group led to a change in thermal properties and crystallization behavior. The DSC analysis indicates that with the increase of comonomer content, the Tg, Tm, T0m and crystallinity were decreasing gradually, and the depression of Tm followed Flory′ prediction for random copolymer. Furthermore, an Avrami method was used to analyze the kinetics of isothermal crystallization of PBS and PBSM-20. The Avrami exponents, estimated by Avrami plots, ranging from 2.8 to 3.0 for PBS and 2.7 to 3.0 for PBSM-20 indicate that the mechanism of crystallization for both homopolyester and copolyester was a tridimensional growth with heterogeneous nucleation. Meanwhile, X-ray analysis shows that there was almost no effect of the methyl succinate unit on the crystal structure.
In a neutral or weak alkaline medium(pH=6.5-9.5), the gold nanoparticle can combine with methylene blue by the virtue of electrostatic and hydrophobic interaction, forming aggregate with bigger diameters(average diameter increase from 12 to 20 nm ). The aggregate arouse Resonance Rayleigh Scattering(RRS) intensity enhancing greatly. The maximum scattering peaks are at 371 nm. Under optimum conditions, there is a linear relationship between scattering intensity(ΔI) and the concentration of methylene blue. This method has a high sensitivity. So gold nanoparticle can be used as the RRS probe of high sensitivity for methylene blue. The detection limit of methylene blue is 21.17 ng/mL. The method which is simple and rapid has good selectivity. It was successfully applied to the detection of methylene blue in clinic serum samples.
In this study, in order to establish analysis models of near-infrared spectroscopy(NIR) of tobacco, 120 samples of tobacco from different cultivation area were surveyed by near-infrared(NIR) spectroscopy. As the new pattern recognition, support vector machine(SVM) can avoid over-fitting problem and owns the superior generalization ability and prediction accuracy, were applied in this study. The quantitative and qualitative analysis models of tobacco samples were studied separately in this experiment using radial basis function(RBF) SVM. For reducing dimension and moving noise, the spectrum variables were highly effectively compressed using the wavelet transformation(WT) technology and the haar wavelet was selected to decompose the spectroscopy signals. Simultaneously, the parameters of the models were also discussed in detail. The best experimental results were obtained using the RBF SVM regression with kernel parameter σ=1.0, 1.2, 1.4, 0\^6, separately corresponds to total-sugar, reducing sugar, nicotine, total-nitrogen, and RBF SVM classifier with kernel parameter σ=1.6. Meanwhile, the values of appraisal index, namely coefficient of determination(R2), root mean squared error of prediction(RMSEP) and mean relative error(RME), indicate its excellent generalization for quantitative and qualitative analysis results and high prediction accuracy. The overall results show that NIR spectroscopy combined with SVM can be efficiently utilized for rapid and accurate analysis of chemical compositions in tobacco and discrimination of tobacco of different origins. On the other hand, the research can show that SVM is effective modeling tools to NIR spectroscopy and can provide technical support for quantitative and quantitative analysis of other NIR applications.
Starting from pyridine-2,6-dicarboxylicacid(DPA),a series of novel pyridine-2,6-dicarboxylic acid derivatives were synthesized. In these compounds,4-(hydroxymethyl)pyridine-2,6-dicarboxylate(4-HMDPA) and 4-{［bis(carboxymethyl)amino］ methyl}pyridine-2,6-dicarboxylate(4-BMDPA) were used as multifunctional ligands to coordiate with Tb(Ⅲ) and Eu(Ⅲ) and their complexes were prepared. The fluorescence properties of the solid complexes and their solutions were investigated in detail. The results indicate that the weak election-withdrawing group 4-hydroxymethyl in 4-position of pyridine in 4-HMDPA could weaken the fluorescence intensity of the lanthanide complexes. The contradistinctive experimental results show that the fluorescence intensities of these complexes are related to pH value of the aqueous solution and the dipole moment of solvent molecule: in the neutral aqueous solution,the fluorescence intensities of these complexes were strongest,while the less the dipole moment was,the stronger the fluorescence intensity was. 4-BMDPA is the better sensitizer and may be used as time-resolved fluorommunoassay.
Abstract An achiral Schiff-base isopropoxide aluminum complex(Ⅱ) was used for the stereoselective ring-opening polymerization of rac-lactide. The kinetics studies indicated that rac-lactide polymerization was first order kinetics to monomer concentration. There was linear relationship between the monomer conversion and molecular weights(Mn) of the polymer with a narrow molecular distribution. These phenomena indicated that the polymerization was well controllable. Moreover, the obtained poly(rac-lactide) was crystalline polymer with relative high tm(179 ℃). 13C NMR and homonuclear decoupled 1H NMR spectra revealed that the polymerization of rac-lactide initiated by complex(Ⅱ) resulted in the isotactic stereoblock polymer, which contained blocks with an average of 11 units of enantiomerically pure lactic acid.
