Characterisation of fluorescence standard materials

Fluorescence is an important property when determining the colour and appearance of a solid opaque material. Relative and absolute measurements of angular fluorescence spectra and quantum yield are important in many industrial fields including paper, textile and also in medical industry. The uncertainty of the measurements is naturally dependent on the uncertainty of the reference standards and therefore it is important to have high-accuracy calibration instruments capable of absolute measurements. Lambertian behaviour of fluorescent emission in solid amorphous materials is a commonly made assumption. Deviation from this behaviour has been shown [1][2] by using goniometric measurements of fluorescence [3][4].This finding is significant since most commercial and research instruments are limited to fixed geometry measurements and usually rely on the assumption of Lambertian emission of fluorescence. This may result in errors in inter geometry measurements of fluorescence and also absolute quantum yield estimations. To address these challenges, either more Lambertian standard materials or reliable methods to correct for these effects are needed. Figure 1. The relative luminescent radiance factors ?L and reflected radiance factors ?R at peak emission wavelength for each sample and reflected wavelength (380 nm) respectively. In this work bispectral luminescent radiance factors and reflected radiance factors of a number of commercially available fluorescence standards and a novel standard material candidate have been measured in a wavelength range from 380 nm to 700 nm with an uncertainty (k=2) of 1%. The angular distribution of the emitted radiation from the standard materials is in addition to being non-Lambertian also shown to be different from the angular distribution of reflected radiation as seen on Figure 1. The novel sample is shown to exhibit more Lambertian emission and reflection behaviour than the commercially available standard materials. In addition the effects of the angular profiles of measured radiation on the absolute quantum yield estimation of the materials are shown