Gilden Photonics launches new QY accessory for their single photon counting fluorimeter -  fluoroSENS

The measurement of Quantum Yields (QY) is a fundamental property of a luminescent sample. It refers specifically to the ratio of the number of photons of light radiated from the photo luminescent material to the number of photons of light that the material absorbs. Practically, QY are very important because they allow the assessment of fluorometric materials and the extent interferences.

As such these measurements are made on solutions, powders, and thin films and apply to a wide range of applications including, for example, fluorescent materials for whiteners and white lights, organic and inorganic LED materials, biology, fluorescent probes and quantum dots, laser threshold requirements, determining suitability of wavelength shifters and for studies of radiation-less transitions in molecular systems.

The fluoroSENS-QY achieves high performance through the use of an integrating sphere. The reason for this is that by the time the light reaches the detector much of the original emission anisotropy has been eliminated so that the detector gives a good measure of the total emitted radiant power. In addition there is the benefit that there is a relative lack of sensitivity to scattering and the geometry of the sample.

However, the sphere walls reflect the excitation light, as well as the emission light, which can be re-absorbed by the sample. This re-absorption is quite important for the excitation peak because part of this light, either reflected from or transmitted through the sample, can be re-absorbed by the sample after reflection from the sphere wall.