Study On The Application Of Photoacoustic Spectroscopy In Photoluminescent Materials

Photoacoustic Spectroscopy (PAS) is a nondestructive detecting technology based on photoacoustic effect. Unlike the traditional absorption spectra, PA spectroscopy can measure opaque samples directly without the need for sample preparation. PA spectroscopy is well applied in physics, materials science, environmental monitoring, biology and pharmaceutics owing to its advantages including high sensitivity, low detection limit and easy operation.In this dissertation, a brief review of the development history and present situation of PA theory and PA spectroscopy application is presented firstly. Then, one-dimensional solid photoacoustic theory (R-G theory) is introduced and the generation mechanism of photoacoustic signal is analyzed. Moreover, the expression of photoacoustic amplitude and phase signal is given and the particular solution of photoacoustic signal under some special cases is discussed. Besides that, a PA measurement system which can realize photochemical translation rate monitoring is described and measurement method of PA amplitude and phase spectrum is discussed. In the system, the photoacoustic spectrum calibration is realized by using characteristic peak of erbium oxide (Er2O3).The work of the dissertation on the application of photoacoustic spectroscopy in photoluminescent materials includes following main aspects:1. PA spectroscopy is used to analyze the rare earth luminescent material BaY2Si3O10:Ce3+. Based on the studies of the relationship between modulation frequency and intensity of photoacoustic signal, the optical property and thermal property of the material are characterized. PA amplitude spectrum is combined with PA phase spectrum, absorption spectrum and excitation (emission) spectrum to analyze the transitions of rare earth ion in rare earth luminescent materials. 2. The influence of doping concentration of rare earth to luminous efficiency is analyzed. A new method that combining PA amplitude and phase spectroscopy to measure relative luminous efficiency of phosphorus materials with variant doping density is presented. The feasibility of the method is proved by fluorescence spectroscopy.3. The energy gap and semiconductor type of the photoluminescent material bismuth oxychloride (BiOCl) are determined by PA spectroscopy, and the results are compared with those of bismuth oxybromide (BiOBr). After UV light irradiation, the white BiOCl became black and the PA amplitude increases gradually. The reason for that is owing to the formation of oxygen vacancies in it. The experimental results show that the forming process of oxygen vacancies can be detected through the PA spectroscopy under different UV irradiation time. The photochemical process can be further explored by the relationship between the intensity of the photoacoustic signal and the UV irradiation time.