Table 2.

Fluorescence quantum yield Ф_F, radiative rate constant k_r, and non-radiative rate constant k_nr of different W species.

Drug Forms	λex/nm	ФF (×10–3) a	kr (× 107 s–1) b	knr (×109 s–1) b	τ/ns (Mean)
W OPEN	320	6.0 ± 0.1	>6	>10	<0.1
W−	320	12 ± 0.1	>12	>10	<0.1
W-Me-β-CD OPEN	320	0.5 ± 0.1	0.02	0.50	2.0
W−-Me-β-CD	320	24 ± 0.1	2.0	0.81	1.22

^a Measured using W in phosphate-buffered saline (PBS, pH ~7.4, 10 mM sodium phosphate) as the standard (Ф_F = 0.012) [9], and calculated using the known equation [18]: ${\varnothing }_{unk}={\varnothing }_{std}\left(\frac{I_{unk}}{A_{unk}}\right)\left(\frac{A_{std}}{I_{std}}\right){\left(\frac{n_{unk}}{n_{std}}\right)}^2$, where n is the refractive indices for the standard (std) and experimental (unk) solvents, I is the fluorescence integral of the emission between 300 and 550 nm, and A is the absorbance at the excitation wavelength. The error estimated as standard deviation of the mean was approximately 10% for the fluorescence quantum yields. ^b Calculated using the known equations: $\varnothing =\frac{{\mathrm{k}}_{\mathrm{r}}}{{\mathrm{k}}_{\mathrm{r}}+{\mathrm{k}}_{\mathrm{nr}}}$, $\mathsf{\tau }=\frac{1}{{\mathrm{k}}_{\mathrm{r}}+{\mathrm{k}}_{\mathrm{nr}}}$, ${\mathrm{k}}_{\mathrm{nr}}=\frac{1-\varnothing }{\mathsf{\tau }}$, and ${\mathrm{k}}_{\mathrm{r}}=\frac{\varnothing }{\mathsf{\tau }}$.