I synthesized nanoparticle with fluorescence excitation wavelength of 400 nm and emission wavelength of 450 nm. Therefore, to measure the quantum yield, we should use standards that have an excitation wavelength of 400 nm. What standard you suggest?
In addition, you also need to consider some technical aspects such as band shape (i.e. band width) in order to select the best standard, Here find attached a useful paper about relevant technical aspects you must consider.
Quinine sulphate is O.K. but you have to be careful because its QY is wavelength dependent.. SO experimental conditions have to be exactly those for which the QY was determined.
9,10-diphenylanthracene in cyclohexane may be another possibility (exc 365 nm, em between 400 and 450 nm (QY 90%). One point deserves attention: re-absorption: if excitation and emission spectra overlap, you have to correct for this (i.e. you will get higher QY :))
For safe measurement it is wise to measure with 2 standards and then measure one standard against the other...