Question

Explain why a plot of Fluorescence Intensity vs. Concentration has a maximum.

Answer 1

Since, the fluorochrome is usually excited at the wavelength at the peak of the excitation curve, and the emission detection is selected at the peak wavelength (or any other wavelengths chosen by the observer) of the emission curve. The selections of excitation wavelengths and emission wavelengths are controlled by an appropriate filter.

The wavelength shift between excitation and emission has been known as Stokes shift. The excitation and emission curves overlap somewhat at the upper end of the excitation and the lower wavelengths of the emission curve (spectral overlap).