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Relative quantum yield of 2-aminopyridine

Quantum yield is a fundamental photophysical parameter that describes a sample’s fluorescence efficiency and is defined as the ratio of the number of photons emitted to the number of photons absorbed by a sample. Accurate and reliable quantum yield measurements are important for a broad range of applications including displays, solar cells, bioimaging and drug development.

There are two optical methods for measuring the quantum yield: the absolute method and the relative method. In the absolute method, the quantum yield is measured directly using an integrating sphere, while in the relative method the fluorescence intensity of the unknown sample is compared with the fluorescence intensity of a standard sample to calculate the quantum yield of the unknown. In this application note, an Edinburgh Instruments FS5 spectrofluorometer is used to measure the quantum yield of 2-Aminopyridine (2AMP) via the relative method. 2AMP in sulfuric acid (H2SO4) has been previously used as a quantum yield reference standard in the UV-visible range. The quantum yield of 2AMP was measured to be 60 % in 1968 and 66 % in 1983. These literature quantum yield reference values are now decades old, and this note presents a reinvestigation and revaluation of the quantum yield of 2AMP in 1 M H2SO4 using quinine bisulphate (QBS) in 1 M H2SO4 as the reference standard with a modern spectrofluorometer.