荧光量子产率计算.pdf

Jobin Yvon Ltd. 2 Dalston Gardens, Stanmore, Middlesex HA7 1BQ UK Tel: 020 8204 8142 Fax: 020 8204 6142 Email: jy@jyhoriba.co.uk www.jyhoriba.co.uk A Guide to Recording Fluorescence Quantum Yields Introduction: When a fluorophore absorbs a photon of light, an energetically excited state is formed. The fate of this species is varied, depending upon the exact nature of the fluorophore and its surroundings, but the end result is deactivation (loss of energy) and return to the ground state. The main deactivation processes which occur are fluorescence (loss of energy by emission of a photon), internal conversion and vibrational relaxation (non-radiative loss of energy as heat to the surroundings), and intersystem crossing to the triplet manifold and subsequent non-radiative deactivation. The fluorescence quantum yield (ΦF) is the ratio of photons absorbed to photons emitted through fluorescence. In other words the quantum yield gives the probability of the excited state being deactivated by fluorescence rather than by another, non-radiative mechanism. 1 The most reliable method for recording ΦF is the comparative method of Williams et al., which involves the use of well characterised standard samples with known ΦF values. Essentially, solutions of the standard and test samples with identical absorbance at the same excitation wavelength can be assumed to be absorbing the same number of photons. Hence, a simple ratio of the integrated fluorescence intensities of the two solutions (recorded under identical conditions) will yield the ratio of the quantum yield val