食品色素日落黄与诱惑红荧光特性的研究

应用英国Edinburgh FLS920P型稳态和时间分辨荧光光谱仪,对日落黄与诱惑红溶液进行荧光光谱的实验测量,得到日落黄荧光峰在420nm,诱惑红荧光峰在432nm。进一步,应用Gaussian 09W软件构建日落黄分子与诱惑红分子的基态和激发态的几何构型,基于密度泛函理论和含时密度泛函理论,完成对两种分子基态和激发态的优化和计算。优化过程中,采用MPWK泛函和6-31g(d)基组;计算过程中,采用B3LYP泛函和6-311g(d,p)基组。考虑到溶剂效应对计算结果的影响,因此在计算过程中引入了极化连续介质模型,最后计算得到日落黄的荧光峰在435nm,与实验所得有3.57%的相对误差;计算得到诱惑红荧光峰在443nm,与实验所得有2.55%的相对误差,两种分子荧光峰的相对误差都在允许范围之内,说明计算合理。在分析光谱特性时,发现两种分子荧光峰的产生与分子内电荷转移有关。

Research on the Fluorescence Properties of Synthetic Pigment Sunset Yellow and Allura Red

For sunset yellow and allura red,the fluorescen ce spectra have been measured with British Edinburgh FLS920 Steady and Time-Res olved Fluorescence Spectrometer.Two geometries which involve the ground state a nd the excited state of sunset yellow and allura red are constructed by utilizin g Gaussian 09W software.Based on the density functional theory and time-depend ent density functional theory,the optimization and calculation about the ground state as well as the excited one are completed.The MPWK function and 6-31g (d) basis sets are applied during the optimization process.Compared with the func tion and basis sets in the former job,the B3LYP functional and 6-311g (d,p) b asis sets are employed when the calculation is carried out.With the considerati on of the influence of the solvent effects on the calculation results,thereby,it is necessary to add the polarized continuum model.In the end,the calculated fluorescence spectra are compared with the experimental measurement of spectra,respectively,the results about sunset yellow show that the calculated fluoresc ence peak at 435 nm which has a relative error of 3.57％,compared with the 420 nm by experiment.For allura red,the calculated fluorescence peak at 443 nm,wh ich means a relative error of 2.55％ exists,compared with the 432 nm by experim ent.That is to say,for the fluorescence peak of sunset yellow and allura red,their relative errors are in the reasonable range.In a word,the calculation re sults show that the calculated fluorescence peaks are advisable.When studying t he fluorescence properties of two molecules,we find the fluorescence peaks are related to intramolecular charge transfer.