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Introduction mixture of two fluorophores of different lifetimes showing the difference between the single and double exponential fitting. 1.2.6 Average Lifetimes For analysis of complex mixtures such as crude oils, the intensity based average lifetime, τ is often used and is given by: τ int = α1τ 2 1 + α2τ 2 2 + αnτ 2 n α1τ1 + α2τ2 + αnτn = f1τ1 + f2τ2 + fnτn = n i=1 fiτi (1.38) where fi is the fractional contribution of the i th component. In this expression, each decay time is weighted by its corresponding fractional intensity and thus this average lifetime is termed the intensity averaged lifetime. The intensity averaged lifetime can be defined as the average lifetime of a collection of different excited- state populations, where the lifetime of each population is weighted by the relative contribution of that population to the total fluorescence. It is also possible to use the pre-exponential factors (i.e. the amplitudes) as weights and define the amplitude averaged lifetime: τ amp = n i=1 n i=1 αiτi αi = n i=1 αiτi where αi are the fractional amplitudes which are defined as: Since n αi = αi n αi = 1, the amplitude averaged lifetime reduces to: i=1 τ amp = i=1 n i=1 αi αiτi (1.39) (1.40) (1.41) For heterogeneous decays, the intensity-based average lifetime is more accurate than the amplitude-based lifetime. However, there are cases where the amplitude 36
Introduction based average lifetime is more appropriate, for example, it has been used to calculate the efficiency of energy transfer [57]. 1.2.7 Lifetime Distributions There are a number of situations where a distribution of decay terms is expected instead of a set of discrete decay times [58–60]. For example, samples containing a mixture of interacting fluorophores, or where a fluorophore exists in a number of different but closely related environments, may be analysed as a distribution of decay times. The most common distributions used are the Gaussian, Lorentzian, and Stretched Exponential distributions [36]. Here, the αi values are replaced by a distribution function α(τ). The relationship to each lifetime is given by: The total decay is given by: I(τ, t) = α(τ)e −t/τ I(t) = ∞ τ=0 (1.42) α(τ)e −t/τ dτ (1.43) where α(τ) = 1.0. The Gaussian αG(τ) and Lorentzian αG(τ) lifetime distributions are given by: αG(τ) = 1 σ √ 2π exp 2 τ − τ −1/2 σ αL(τ) = 1 π Γ/2 (τ − τ) 2 + (Γ/2) 2 (1.44) (1.45) where τ is the central value of the distribution, σ is the standard deviation and Γ is the full width of the distribution at half maximum. For a Gaussian distribution the full width at half maximum is given by 2.345σ. When analysing lifetime distributions, each decay time component is associated with three variables, the amplitude αi, the fractional contribution fi, and the full width at half maximum or FWHM Γ. Consequently, a complex decay may be fit with fewer exponential components. The 37
Page 1 and 2: Time-Resolved Fluorescence Spectros
Page 3 and 4: Abstract behaviour allowing calcula
Page 5 and 6: Contents List of Publications and P
Page 7 and 8: Contents 2.3 Temperature based Life
Page 9 and 10: List of Publications and Presentati
Page 11 and 12: Abbreviations Abbrev Definition API
Page 13 and 14: Chapter 1 Introduction For many yea
Page 15 and 16: Introduction temperature increases
Page 17 and 18: A seal or cap-rock that prevents th
Page 19 and 20: Introduction Figure 1.2: Crude oil
Page 21 and 22: Introduction eroatoms (O, S, N) and
Page 23 and 24: Introduction toluene, dichlorometha
Page 25 and 26: 1.2 Fluorescence Spectroscopy 1.2.1
Page 27 and 28: Introduction S1 state for a certain
Page 29 and 30: Introduction The peaks in the absor
Page 31 and 32: Introduction Figure 1.9: Jablonski
Page 33 and 34: Introduction Figure 1.10: Static qu
Page 35 and 36: Introduction the ratio of τ 0/τ i
Page 37 and 38: 1.2.5 Measuring fluorescence lifeti
Page 39 and 40: Introduction Figure 1.14: Time-reso
Page 41 and 42: Introduction The autocorrelation fu
Page 43 and 44: Introduction case, the molecules ex
Page 45 and 46: From Equation 1.26, Introduction ω
Page 47: m = 1 P 2 + Q 2 Introduction (1.36
Page 51 and 52: Introduction Figure 1.21: General p
Page 53 and 54: Introduction TAC output pulse is gi
Page 55 and 56: Introduction at each frequency acco
Page 57 and 58: Introduction diagram showing the op
Page 59 and 60: Introduction Figure 1.26: Schematic
Page 61 and 62: Introduction provides enhanced cont
Page 63 and 64: Introduction PAH’s. It has been s
Page 65 and 66: to heavy oils (low API gravity). In
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Page 69 and 70: Introduction Figure 1.34: Fluoresce
Page 71 and 72: Introduction used [126, 129, 132] a
Page 73 and 74: Introduction Figure 1.36: Plot of a
Page 75 and 76: fractional contributions over time
Page 77 and 78: Introduction concentration and Ksv
Page 83 and 84: 1.5 Crude oil photophysics Introduc
Page 85 and 86: Introduction stages of thermal matu
Page 87 and 88: Introduction yellow to red fluoresc
Page 89 and 90: 1.7 Thesis goal Introduction This i
Page 91 and 92: Materials and Methods concentration
Page 93 and 94: Table 2.2: Fractionation Data for B
Page 95 and 96: Materials and Methods 2.2 Frequency
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Materials and Methods The dichroic
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Figure 2.5: Transmission characteri
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Materials and Methods Figure 2.7: S
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Materials and Methods The variation
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Materials and Methods Figure 2.9: L
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Materials and Methods Figure 2.10:
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Materials and Methods Comparison ca
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Materials and Methods with ρ param
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Materials and Methods 2.3 Temperatu
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Materials and Methods IRF of the sy
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Materials and Methods 2.4 Temperatu
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Materials and Methods a series of w
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Materials and Methods 2. Using the
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Lifetime study on crude oils by the
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Table 3.3: Average lifetime and sin
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Table 3.5: Average lifetime and sin
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3.5 Single Lifetime distributions L
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Energy Transfer and Quenching proce
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Influence of low temperature on flu
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Conclusions and Future Work model (
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Appendix A Reference Lifetime Stand
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Appendix Figure A.2: FD response fo
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A.3 SPA N-(3-sulfopropyl) acridiniu
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A.4 Rhodamine B Appendix Rhodamine
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A.5 Acridone Appendix The highly ph
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Appendix Figure A.11: FD response f
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Table B.1: Frequency Domain average
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Appendix Table B.3: Emission λmax
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Table B.5: Frequency Domain lifetim
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Appendix for the determination of t
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Appendix Figure C.3: Multifrequency
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Appendix Figure C.5: FLIM intensity
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Appendix Table C.1: Fluorescence li
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Appendix D Published Work 281
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998 J Fluoresc (2008) 18:997-1006 s
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1000 J Fluoresc (2008) 18:997-1006
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1002 J Fluoresc (2008) 18:997-1006
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1004 J Fluoresc (2008) 18:997-1006
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1006 J Fluoresc (2008) 18:997-1006
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Bibliography [10] W. G. Dow (1977),
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Bibliography [31] M. A. Ali and W.
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Bibliography [53] R. D. Spencer and
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Bibliography [75] K. Konig (2000),
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Bibliography [93] C. Pasquini and A
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Bibliography [113] C. Ralston, X. W
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Bibliography [132] A. Ryder (2004),
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Bibliography variable-angle synchro
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Bibliography [171] R. K. McLimans (
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Bibliography using fluorescence spe
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Bibliography [210] H. Mishra, S. Pa
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Bibliography [229] N. Boens, W. W.
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