2- naphthol fluorescence spectrum

Naphthol and its 3,6-disulfonate derivative show consistency in their spectral feamres in both the photoacid and base sides, while much less consistency is evident in the spectral features of the 1-naphthol derivatives in the acid side, where the fluorescence spectrum appears to be much narrower and more structured than the absorption spectrum (Figure 21). This points to more extensive electronic rearrangements in the acid side of... 

Figures 22 and 23 offer a closer look at the absorption and fluorescence spectra of several 1-naphthol derivatives in methanol. In the case of sulfonate-substituted 1-naphthols, the substituent effect on the absorption spectra is relatively small, while a considerable effect is observed in the corresponding fluorescence spectra of the photoacids. This effect resembles the solvent effect on the fluorescence spectrum of the parent 1-naphthol molecule. Using the analogy to the effect of solvent polarity on the spectra, the ring position of the sulfonate group seems to appear more polar , moving from the 2- to the...

Fluorescence from A and A -H should occur at different wavelengths. Curve A in Figure 12.19 shows the fluorescence spectrum of 2-naphthol (3), which was recorded under acidic conditions, while curve B shows the fluorescence spectrum of the 2-naphthoate ion (4), which was recorded under basic conditions. At intermediate pH values, fluorescence spectra from both 3 and 4 may be seen. Figure 12.20 shows the fluorescence spectrum of 2-naphthol in a series of solutions with pH values that increase from A to... 

The fluorescence level inversion of 1-naphthol from La to Lb occurred after the gelation ofTEOS, while the fluorescence spectrum of 2-naphthoI molecules during the sol-gel-xerogel transitions was almost unchanged (Fujii, 1990). Therefore, the fluorescence spectrum of 1-naphthol molecules is a useful photophysical probe. The probe was used in the sol-gel-xerogel transition systems ofmixed aluminum and silicon oxides system (Fujii, 1992, 1997). Hydrogen-bonded forms and contact ion pair forms are considered for the interaction species formed between 1-naphthol and the gel surface. 

For n = 4, the emission spectrum shows a broad structure centered at about 430 nm, that is, largely displaced towards the red. The same kind of spectra are obtained when n > 4 clusters are excited. These excited clusters give rise to an emission characteristic of naphtholate anion fluorescence emission which corresponds to an emission following the intracluster proton transfer. 

Figure 4-12. Fluorescence emission spectra of l-naphthol(NH3) clusters (n — 1-4). The excitation laser is fixed on the 0° bands for n = 1-3. For n = 4, the excitation frequency is fixed at 30,985 cm 1 (laser-scattered light is marked with an asterisk) (from Cheshnovsky and Leutwyler 1988). This clearly shows that the emission spectrum of n = 4 is strongly displaced towards the red characteristic of the naphtholate emission.

The origins of the first scenario goes back to the classic studies of Shizuka and Tsutsumi . In this scenario the Lb and La transitions are congested together in the absorption (the absorption spectrum of 1-naphthol in water is shown in Figure 14) and fluorescence spectra of 1-naphthol (Figure 17). 

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