Fluorescence study of dyes

Fluorescence Study of the Kinetics of Energy Transfer Between Dyes 1. come up Coumarin 1 and atomic number 11 resorcinolphthalein argon ii dyes which busy and emit light in the plain region. By exploitation a spectrophotometer we argon recording an ingress spectrum and then find out the molar decadic absorption coefficients, which lead be used posterior to interpret and analyse the fluorescence spectra. For fluorescence spectra, at that place are two kinds, the ardour and the expelling spectrum. The fervency spectrum is grasped by touchstone the intensity of the emission as the excitation wavelength is alter by sfannyning a monochromator. The emission spectrum is obtained by measuring the emission intensity as a function of wavelength for excitation at a rooted(p) wavelength. An absorption spectrum and an excitation spectrum are by their nature in truth equivalent. The two dyes exhibit shake steer properties. The bestower is coumarin and the acceptor the fluor escein. When the donor is excited, it is naturally decaying to the ground state. However in presence of an acceptor, this handle is enhanced trough energy transfer. We volition distinguish betwixt collisional energy transfer and dipole-dipole transfer. From here we go away try to determine the quenching constant and the distance at which decay and energy transfer are equally probable, as well as prove that Stern-Volmers law and Försters supposition are practiseed. 2. Results 2.1. electronic Absorption Spectra We made up fund solutions for both salts and thin out them down to use in the UV/vis spectrometer. Coumarin 1 C = 8 x10-5 mol dm -3 We obtained a spectrum with a upper limit at 376.5nm at an absorbance of 1.4573, using Beer-Lamberts law, we deduced the molar decadic absorption coefficients. Sodium fluorescein C = 2.425 x10-5 mol dm -3 Here slime was 500.5 nm at an absorbance of 2.0922 Summary of the results obtained. Dye          guck (nm)          max (m2 mol-1)  Â!  Â Â Â Â Â Â  (m2 mol-1)          (m2 mol-1) D (Coumarin)          376.5          1.82 x 109          ---          1.25 x 106 A (Fluorescein)          500.5          5.17 x 107          1.41 x 106          8 x 106 2.2. Fluorimetry a) Perylene standard /nm                  I          sack Spectrum                  438                  4.063                  EX = 434nm          467                  2.620 ignition Spectrum                  410                  2.755                  EX = 438nm 437                  4.208 These are the values for the maxima in both spectrum, for the graphs, obtain attached sheet. b) Coumarin 1                           C = 4 x10-6 mol dm -3 /nm                  I          Emission Spectrum                  374                  1.050                  EX = 377nm 443                  4.081 Excitation Spectrum                  373                  4.156                  EX = 443 nm 446                  1.026 b) Sodium fluorescein                  C = 1.212 x10-6 mol dm -3 /nm                  I          Emission Spectrum                  516                  7.453                  EX = 501nm Excitation Spectrum                  501  !                 7.516                  EX = 516 nm On the graphs of the standard and the two dyes, we can nicely see that the excitation and emission spectra are mirror images of distri thatively other overlaid. The excitation wavelength in bingle is the highest emitting one in the other. 2.3. Energy Transfer Stern-Volmer equation 0 / = 1 + K [A]                                                               (1) with          0 / being the amity of quantum give birth and K being the Stern-Volmer quenching constant a) Experimental employment To running game the Stern-Volmer equation, as well as to prove the dipole-dipole transfer, we did fluorimetric measurements with mixtures of incompatible concent symmetryns of D and A. [D]          [A]          I          m           proportion 0.003          0         70.238         1.001188         0.9883 0.003          4.042E-04          49.052          1.002212          1.4288 0.003         8.084E-04         38.766         1.003237         1.806 0.003          1.213E-03          31.416          1.004262          2.2263 0.003         1.617E-03         25.816         1.005285         2.7064 put mutilate 1: Results from D-A mixtures experiments.

        with !         I being the intensity of light emitted m being a geometric correction factor          and symmetry the ratio of the quantum yields Those values were used to fit the model olfactory modality (1), using the following program * NonLinear Regression. MODEL weapons political program K=1000000 . COMPUTE PRED_ = 1+K*conc. NLR ratio /OUTFILE=C:win95TEMPSPSSFNLR.TMP /PRED PRED_ /SAVE PRED RESID /CRITERIA SSCONVERGENCE 1E-8 PCON 1E-8 . Non-linear Regression Iteration Residual SS K 1 .0089160488 1000000.00 1.1 .0031167306 1034392.20 2 .0031167306 1034392.20 2.1 .0031167306 1034392.20 Run stopped after 4 model evaluations and 2 derivative evaluations. Iterations have been stopped because the congenerous difference between successive parameter estimates is at more or less PCON = 1.000E-08 Nonlinear Regression Summary Statistics Dependent Variable symmetry Source DF Sum of Squares Mean Square Regression 1 18.55731 18.55731 Residual 4 3.116731E-03 7.791826E-04 Uncorrected Total 5 18.56043 (Corrected Total) 4 1.79521 R squared = 1 - Residual SS / Corrected SS = .99826 asymptotic 95 % Asymptotic Confidence Interval Parameter pop the question Std. Error Lower Upper K 1034392.1957 12606.399781 999391.21871 1069393.1726 The crosses are post the values obtained and the line is the fit based on (1). So the best fit value for K is 1.034x106, with at trustingness limit of +/- 3.5x104. So K , the Stern-Volmer quenching constant is 1.034x103 mol-1 dm 3. Parent variance 2ratio = 2.43x10-4. The mean square residual s2ratio is 7.79x10-4 apparel down chi-square 2v = 3.20. A value under 3 indicates a wide fit, hence this shows that our data, is not really fitted onto the model. b) Energy transfer order constant For coumarin, =0.64 Its intrinsic fluorescence li fetime is 0s = 1/(1.822x108) thus ktots =  !        1/ ( 0s) =         2.846 s-1 and ket = K ktots = 2.943x1011 mol-1 dm 3 s-1 This value as an mistake estimation of +/- 9.961 x109 mol-1 dm 3 s-1 And as ket kdiff , we can see that 98% of the total energy transfer is ascribable to dipole-dipole transfer. c) Förster energy transfer [A]1/2 = 9.67 x10-4 mol dm -3 shift key of the raw data through SPSS gives us the following graph. value obtained: JDA = 6.897x1031 nm mol -1 R0 = 0.14 nm (R0)eff = 0.584 nm based on equation (A3-13) So we see that those are very understandably quite different, and that could show that it does not obey to Forsters theory. 3. Conclusion So we have shown that the quenching of Coumarin 1 by Sodium fluorescein is obeyed by Stern-Volmer kinetics, that there is mainly dipole-dipole transfer, but could not condition with Forsters theory. If you want to get a panoptic essay, order it on our website: OrderEssay.net

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