Investigation On The Spectral Properties Of 2D Asynchronous Fluorescence Spectra Generated By Using Variable Excitation Wavelengths As A Perturbation

Fluorescence spectroscopy is widely utilized as tool of investigation, analysis, control and diagnosis in many fields relevant to physical, chemical, biological and medical sciences. When fluorescent spectroscopic method is utilized to study a chemical system, a complex situation may be encountered. Even though only one fluorescent solute occurs in a solution, the fluorescent molecules may exist in different micro-environments, so that the corresponding emission spectra are different. Therefore, we need to study a suitable method to detect the different Subtle spectral.In two-dimensional correlation spectroscopy, the spectral data are extended to the second dimension, providing a chance to alleviate the problem caused by overlapping spectral congestion. We find the idea of orthogonality is also helpful in the fluorescent spectroscopic studies.In this paper, we investigate 2D asynchronous fluorescence spectrum generated by using variable wavelength of monochromatic radiation as an external perturbation. Based on the results of mathematical analysis and computer simulation, we find that no cross peak will be produced on the 2D asynchronous spectrum if the fluorescent solute under investigation occurs in a single micro-environment. The observation of cross peaks implies that the fluorescent molecule may occur in different micro-environments in a solution. Based on these results, we use 2D asynchronous spectra to investigate the emission spectra of anthracene dissolved in cyclohexane. When the concentration of anthracene is low, no cross peak is produced in the resultant 2D asynchronous spectrum, confirming that anthracene is dissolved as single molecule in the solution. As the concentration elevated, cross peaks appear in the corresponding 2D asynchronous spectra. A plausible explanation of this phenomenon is that anthracene may undergo aggregation via ?-? interaction or ?-C-H interaction.We can obtain that this poach is an advantageous tool even if the characteristic peaks are highly overlapped and the corresponding experiments can be achieved by only general spectrofluorimeter. And this method is still valid for the detection of low concentration of dilute solution.