## 3 Results
### Water-Methanol Mixed Solution of TPPS  
Figure 5a shows the dependence of the absorption change of the water-MeOH mixed solution of F-monomer at 412 nm on the mole fraction of MeOH when the NaOH concentration is 1 mM. The 532 nm laser was used as the pump light. Because \(|\Delta A|\) at 412 nm is proportional to the absorbance \(A\) at the excitation wavelength of 532 nm, we do not compare \(|\Delta A|\) but \(|\Delta A|/A\). The \(A\) tended to decrease with the mole fraction of MeOH. As the proportion of MeOH to water was increased, \(|\Delta A|/A\) was decreased. \(|\Delta A|/A\) is 0.17 times larger when the mole fraction of MeOH is 0.96 than when it is 0. The decrease in \(|\Delta A|/A\) can be explained by the increase in the dissolved oxygen concentration by mixing methanol. As the dissolved oxygen concentration increases, the lifetime of the triplet state of the F-monomer becomes short, and the triplet excited-state absorption and SA effects decrease. Figure 5b shows the dependence of \(|\Delta A|/A\) of the water-MeOH mixed solution of F-monomer on the mole fraction of MeOH when the NaOH concentration is 10 mM. Because \(A\) tended to decrease with the mole fraction of MeOH, \(|\Delta A|\) needs to be corrected. By mixing MeOH with the F-monomer aqueous solution, \(|\Delta A|/A\) increased up to more than 50 times. Compared with when the mole fraction of MeOH is 0, \(|\Delta A|/A\) is 57 and 0.27 times  
Figure 4: Absorption spectra (red line) and DAS (black line) of presently (**a**) and previously (**b**) prepared PVA sample. The 532 nm laser was used as the pump. Figure 5: Dependence of amount of \(|\Delta A|/A\) of water-MeOH mixed solution of F-monomer with 1 mM NaOH (**a**) and 10 mM NaOH (**b**) on mole fraction of MeOH. The 532 nm laser was used as the pump. \(|\Delta A|\) is amount of absorbance change at 412 nm. \(A\) is absorbance at excitation wavelength of 532 nm. when it is 0.32 and 0.95, respectively. The dissolved oxygen concentration is considered to decrease by adding MeOH and NaOH. Figure 6 shows the DAS of the mixed solution of F-monomer when the mole fraction of MeOH is (a) 0 and (b) 0.32. Mixing MeOH did not significantly change the shapes of the absorption spectra and DAS. \(|\Delta A|/A\) of the F-monomer aqueous solution with [NaOH] = 10 mM was approximately two times larger than that of the F-monomer aqueous solution with [NaOH] = 1 mM (Figures 2a and 6a). Even when the F-monomer solution was irradiated with the pump on and the probe off, a signal was observed around Q band (Figure 7). Because the shape of the signal is the same as the emission spectrum of F-monomer [5; 39], the signal is due to the fluorescence of F-monomer. The well-known method [40] was used to compare the fluorescence quantum yields of each sample. The fluorescence quantum yields of two different samples, \(\Phi_{1}\) and \(\Phi_{2}\), are related by the equation  
\[\frac{\Phi_{1}}{\Phi_{2}}=\left(\frac{F_{1}}{A_{1}}\right)\left(\frac{A_{2}}{ F_{2}}\right)\left(\frac{n_{1}^{2}}{n_{2}^{2}}\right) \tag{1}\]  
where \(F_{1}\) and \(F_{2}\) are the fluorescence intensity (area under the emission peak) of each sample, \(A_{1}\) and \(A_{2}\) are the absorbance at the excitation wavelength of each sample, and \(n_{1}\) and \(n_{2}\) are the refractive indices of the solvent of each sample. Because the refractive indices of water and methanol are almost the same, in the present experiment, it can be approximated as  
\[\frac{\Phi_{1}}{\Phi_{2}}=\left(\frac{F_{1}}{A_{1}}\right)\left(\frac{A_{2}}{ F_{2}}\right). \tag{2}\]  
Therefore, it is simply expressed by  
\[\Phi\propto\frac{F}{A}. \tag{3}\]  
Figure 6: Absorption spectra (red line) and DAS (black line) of water-MeOH mixed solution of F-monomer with 0 (**a**) and 0.32 (**b**) mole fraction of MeOH. NaOH concentration is 10 mM. A 532 nm laser was used as the pump. Figure 7: Emission spectrum (corrected for spectral sensitivity) of F-monomer aqueous solution with [NaOH] = 1 mM observed with 128-channel lock-in detector. The 532 nm laser was used as the pump.