Time-resolved emission spectrum

Jaye AA, Stoner-Ma D, Matousek P, Towrie M, Tonge PJ, Meech SR (2005) Time resolved emission spectra of green fluorescent protein. Photochem Photobiol 82 373-379... 

As an example for linear x2-fitting, we analyse time resolved emission spectra of a mixture of two components with overlapping emission spectra and similar lifetimes. 

Among other examples, time-resolved luminescence has recently been applied to the detection of different trace elements (i.e., elements in very low concentrations) in minerals. Figure 1.13 shows two time-resolved emission spectra of anhydrite (CaS04). The emission spectrum just after the excitation pulse (delay 0 ms) shows an emission band peaking at 385 nm, characteristic of Eu + ions. When the emission spectmm is taken 4 ms after the pulse, the Eu + luminescence has completely disappeared, as this luminescence has a lifetime of about 10/rs. This allows us to observe the weak emission signals of the Eu + and Sm + ions present in this mineral, which in short time intervals are masked by the En + Inminescence. The trivalent ions have larger lifetimes and their luminescence still remains in the ms delay range. 

The narrow band with two maxims at 335 and 360 nm in time-resolved emission spectra of datolite (Fig. 4.16a), with a short decay time of 30 ns is connected with Ce +. 

The time-resolved emission spectra (TRES) and fluorescence lifetimes, ti, of the fluorene derivatives were measured in liquid solutions at room temperature with a PTI QuantaMaster spectrofluorimeter with 0.1 ns temporal resolution [20]. At this resolution, all investigated fluorenes exhibited TRES which were coincident with the corresponding steady-state fluorescence spectra. As an example, TRES for compounds 3 and 11 in hexane, THE, and ACN are presented in Eig. 8 for different nanosecond delays 0 ns (curves 2,4,6) and 5 ns, which modeled the steady-state condition (curves 3,5,7). No differences in the fluorescence spectra for these two delays were observed, indicating that all relaxation processes in the first excited state Si are sufficiently fast for fluorene molecifles and did not exceed the time resolution of the PTI system ( 0.1 ns). 

Time-resolved emission spectra are reconstructed from the normalized impulse response functions (26) ... 

Once the time-resolved emission spectra are so generated, it is informative to monitor the time evolution of the emission spectra. To this end, it is convenient to focus on the time course of the emission center of gravity (i>(t)) (27) ... 

Time-resolved emission spectra were reconstructed from a set of multifrequency phase and modulation traces acquired across the emission spectrum (37). The multifrequency phase and modulation data were modeled with the help of a commercially available global analysis software package (Globals Unlimited). The model which offered the best fits to the data with the least number of fitting parameters was a series of bi-exponential decays in which the individual fluorescence lifetimes were linked across the emission spectrum and the pre-exponential terms were allowed to vary. 

The time-resolved emission spectra were reconstructed from the fluorescence decay kinetics at a series of emission wavelengths, and the steady-state emission spectrum as described in the Theory section (37). Figure 4 shows a typical set of time-resolved emission spectra for PRODAN in a binary supercritical fluid composed of CO2 and 1.57 mol% CH3OH (T = 45 °C P = 81.4 bar). Clearly, the emission spectrum red shifts following excitation indicating that the local solvent environment is becoming more polar during the excited-state lifetime. We attribute this red shift to the reorientation of cosolvent molecules about excited-state PRODAN. 

Steady-state fluorescence spectra recorded after the addition of the NDI or PM I acceptor to the bisporphyrin tweezer ( rrl = 660 nm), demonstrated substantial quenching (75%) with increasing quantities of the NDI or PM I acceptors. Time-resolved emission spectra recorded in toluene for the complex 26 were biexponential containing a dominant short-lived CS components (80 ps, -95%) attributed to photoinduced ET from donor porphyrin to NDI, and a minor long-lived component (Ins, 5%). The lifetime of the dominant short-lived CS state is increased two- to threefold relative to covalently linked systems under similar conditions of solvent, donor-acceptor distance and thermodynamics [37]. Charge recombination rates from 1.4 to 3.8 x 1()9s 1 were observed, depending on whether the NDI or PM I acceptor was bound within the cavity. 

Fig. 22 Emission spectra of polycrystalline [AuI C(NHMe)2 2](PF6)-0.5(acetone). A Emission (A,excitation 383 nm) and excitation (Aemission 482 nm) spectra at 300 K. B Time resolved emission spectra at 300 K solid line emission acquired within 50 ns of a 337 nm laser pulse dotted line emission acquired 200 ns after the laser pulse at 295 K. C Emission (Aexcitation 365 nm) spectrum at 77 K. From [48]...

Figure 11-16. Time-resolved emission spectra of C153 at 296 K in formamide showing the continuous red shift with time characteristic of solvation dynamics. The times represented are 0, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, and 50 ps in order of decreasing peak intensity. The figure is taken from Stratt and Maroncelli [110] with permission...

Sheet-like, flower-like, and bimdle-like YB03 Eu " NCs are synthesized via a hydrothermal route. The time-resolved emission spectra... 

Table 3. Vibrational satellites of the electronic origin at 18,418 cm of Pd(2-thpy)2 dissolved in n-octane from time-resolved emission spectra (Fig. 8) compared to IR data [58]...

Time-resolved emission spectra (Sect. 3.1.4, Fig. 8) show that the triplet sublevels I and III exhibit very different emission spectra with respect to their vibrational satellite structures. The long-lived state I is mainly vibronically (Herz-berg-Teller, HT) deactivated, while the emission from state III is dominated by vibrational satellites due to Franck-Condon (FC) activities, whereby both types of vibrational modes exhibit different frequencies. This behavior makes it attractive to measure a PMDR spectrum. 

In conclusion, it is possible for Pt(2-thpy)2, to separate the emission spectra that are super-imposed in time-integrated spectra by time-resolved emission spectroscopy. It is important that one also obtains a low-temperature (1.3 K) emission spectrum from a higher lying state with the corresponding high spectral resolution. This possibility is a consequence of the relatively slow spin-lattice relaxation. Or vice versa, since the monitored time-resolved emission spectra are clearly assignable to different triplet substates, these results nicely support the concept of a slow spin-lattice relaxation as developed above. Moreover, the results presented reveal even more distinctly a triplet substate selectivity with... 

Figure 1 illustrates typical time-resolved emission spectra of C153 observed in the solvents acetonitrile, chloroform, and 1-pentanol. Also shown (dashed curves) are the steady-state emission spectra (equal to the time infinity spectra in most cases) and the estimated time-zero spectra, the spectra expected prior to any solvent relaxation. (The latter were obtained through comparison of steady-state spectra in the solvent of interest and in a non-polar reference solvent as described in Ref. 17.) A few features of these spectra are noteworthy. 

GW cm ) pulsed CO2 laser radiation shown to result in broad u.v.-visible chemiluminescence Measurement of time-resolved emission spectra in the 618 2—5 p,m region following CO2 laser irradiation of CDF, and mixtures of CDF3-CHF,. Emission from vibrationally excited CDF, and DF observed, the latter being produced in the IRMPD of CDF,... 

Time-resolved emission spectra exhibit multi-exponential decay at 340 and 437 nm corresponding to lifetimes in the range 0.1-10 ns [107]. The longer lifetimes agree with those reported for other ZnS powders [108] and for colloids [26, 94]. It is recalled that multi-exponential decay may originate not only in different emitting states but also in the presence of various particle sizes [109-111]. 

Fig. 41. Time-resolved emission spectra for TNS bound to egg lipid at 20 °C. Early spectrum time delay (At) = 0 gate width (8t) = 2.5 ns. Late spectrum At = 31 ns, 6t = 2.5 ns...

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