pH Effect on Two-Photon Cross Section of Highly Fluorescent Dyes Using Femtosecond Two-Photon Induced Fluorescence
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- 作者：Krishnandu Makhal ; Debabrata Goswami
- 关键词：Two Photon Absorption (TPA) ; Two Photon absorption cross section (TPACS) ; Two Photon Induced Fluorescence (TPIF) Technique ; pH and pKa ; Fluorescence Quantum Yield ; Acid Base Equilibrium
- 刊名：Journal of Fluorescence
- 出版年：2017
- 出版时间：January 2017
- 年：2017
- 卷：27
- 期：1
- 页码：339-356
- 全文大小：
- 刊物类别：Biomedical and Life Sciences
- 刊物主题：Biomedicine, general; Biological and Medical Physics, Biophysics; Biotechnology; Biochemistry, general; Analytical Chemistry;
- 出版者：Springer US
- ISSN：1573-4994
- 卷排序：27
文摘
Effect of solution pH on two-photon absorption cross-section of highly fluorescent Coumarin and Rhodamine dyes with high repetition rate femtosecond laser pulses at 780 nm is presented using two-photon induced fluorescence technique. A correspondence in the measured two-photon and single-photon cross-section values is seen when the pH changes from acidic to basic conditions (pH = 2–10) for solutions in 1:1 water-ethanol binary mixture. By plotting changes in the single-photon and two-photon fluorescence in this pH range, the excited state pKa values are found. The ground state pKa values are also affected by the protonation deprotonation equilibrium as a result of variation in pH from acidic to basic, which are characterized by changes in absorbance spectra. Most of these single-photon and two-photon induced fluorescence spectra show characteristic blue shifts. Different fluorescence quantum yields calculated at each pH reflect a change in structure corresponding to their associated properties as a result of acid base equilibrium.