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PtT975 Lifetime measurement (라이프타임)

Introduction1. Principle of fluorescence and phosphorescenceFluorescence and phosphorescence are types of luminescence, which is the spontaneous emission of light. Fluorescence is a radiative process from the lowest excited state (S1) to the ground state (S0) in a fast (10-9 to 10-6s). However, in the phosphorescence, fast intersystem crossing from singlet excited state (S1) to the triplet excited state (T1) occurs and the following relaxation process happens, which is called phosphorescence. In fact, the decay of the T1 state back to the S0 is a forbidden transition since the states have different spin multiplicity, due to conservation of angular momentum. However, spin-orbit coupling relaxes this restriction and a radiative transition from the T1 to the S1 becomes possible. T1 to S0 transition occurs on a much slower timescale, microseconds to thousands of seconds.2. UV/Vis spectrometerFigure SEQ Figure * ARABIC 1 UV/Vis spectrometerUV/Vis spectrometer measures the absorption intensrometer is an instrument that measure the concentrations in solution that contain fluorescing molecules.Figure SEQ Figure * ARABIC 2 FluorometerA fluorometer is composed of light source, excitation monochromator, sample, emission monochromaterand detector. Flurometer has excitation and emission monochromator since the excitation and emission process occurs and each wavelength region is different each other. Also, the detector is located in to 90⁰ to the sample to measure the emitted radiation unlike the spectrometer.4. PhotodiodeIt is a PN junction device that creates current from external light as a photodetector. Photodiode performs as a reverse biased mode and converts light energy into electrical energy.5. Kinetic model for the photoluminescenceLuminescence is the transition process of an excited molecular state (A*) into the ground state (A). These process is a kind of the first rate reaction, of which the concentration of A* is exponentially decrease and its logarithm is negativorganic dyes or metal complexes, so a transition toward oxygen energy states is possible and even favorable. Therefore, in the presence of oxygen, the oxygen sensor like PtT975 loses its phosphorescence energy so that the lifetime is shorten.Experimental MethodProcedures1. Absorption spectra of PtT975 with UV/Vis spectrometera. Prepare the blank and PtT975/Acetonitrile solution before purging.b. Obtain the absorption spectra of 1-a.c. Prepare the PtT975/Acetonitrile solution after purging.d. Obtain the absorption spectra of 1-c.* Set up the wavelength scan range: 300nm~600nm2. Emission spectra of PtT975 with a fluorometera. Obtain the emission spectra of the PtT975 before puring.b. Obtain the emission spectra of the PtT975 after puring.* Set up the wavelength scan rage: 400nm~700nm3. Time-domain lifetime measurement.a. Time-domain lifetime measurement for a purged sample.ⅰ. Check the optical setup for the time-domain lifetime measurementⅱ. Turn on the laser and warm it up for 10 min.ⅲ.igure SEQ Figure * ARABIC 5 Aerated absorption spectrum of 3μM PtT975Data analysis:Actually, there is no significant difference between [Figure ] and [Figure ]. That means, the oxygen has no impact on absorption process of PtT975 sample.Figure SEQ Figure * ARABIC 6 Purged and aerated absorption spectrum of 3μM PtT9752. Emission spectra of PtT975 with a fluorometera. Purged sampleFigure SEQ Figure * ARABIC 7 Purged emission spectrum of 100um PtT975b. Aerated sampleFigure SEQ Figure * ARABIC 8 Aerated emission spectrum of 100um PtT975Data analysis:purged and aerated PtT975 well shows that both results have the highest peak near 650nm wavelength. The only difference is the y-axis counts scale. In other words, the peak intensity is reduced in the case of the aerated PtT975. Compared to the result of absorption process, emission spectrum is influenced by the air. Due to phosphorescence quenching, the oxygen takes the excited energy instead of the sample, so total energy that sample is t sensor, but not theabsolute concentration of the oxygen. What kind of additional research do you propose to addthe capability to this oxygen sensor?A: To know the absolute concentration of the oxygen, use collisional quenching process.I0/I=1+KSV [Q]I0: Fluorescence intensity observed in the absence of quencherI: Fluorescence intensity observed in the presence of quencherKSV: Stern-Volmer quenching constant[Q]: quencher concentrationThrough the Stern-Volmer equation, the concentration of quencher (i.e. O2) can be calculated.ConclusionAbsorption spectrum via UV/Vis spectrometer shows the most appropriate wavelength range to excite PtT975 sample. As PtT975 undergoes phosphorescence process, relatively longer wavelength compared to the absorption result is measured. After aeration, additionally different result is detected. In the presence of oxygen, the emission intensity life [Figure 8] is decreased rather than before [Figure 7]. Therefore, in the time-domain lifetime measurement, the l

자연과학| 2021.05.07| 7페이지| 1,500원| 조회(188)

물리화학, 화학, 라이프타임, spectrometer, Oscilloscope, lifetime

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