Time-resolved infrared fluorescence

Martin CB, Shi X, Tsao M-L, Karweik D, Brooke J, Hadad CM, Platz MS. (2002) The photochemistry of riboflavin tetraacetate and nucleosides. A study using density functional theory, laser flash photolysis, fluorescence, UV-Vis and time resolved infrared spectroscopy. J Phys Chem B 106 10263-10271. 

Sakai, M., Kawashima, Y., Takeda, A., Ohmori, T. and Fujii, M. (2007) Far-field infrared super-resolution microscopy using picosecond time-resolved transient fluorescence detected IR spectroscopy. Chem. Phys. Lett., 439, 171—176. 

FIGURE 1. Experimental set-up for detection of time and spectral resolved infrared fluorescence signals from water molecules fomied in Reaction (1). 

TA transient absorbance TRIR time-resolved infrared resonance TRFS time-resolved fluorescence spectroscopy. 

Zhu L, Stryjweski WJ, Soper SA (2004) Multiplexed fluorescence detection with micro-fabricated devices with both time-resolved and spectral-discrimination capabilities using near-infrared fluorescence. Anal Biochem 330 206-218... 

From the analysis of the data in the LIPID AT database (41), more than 150 different methods and method modifications have been used to collect data related to the lipid phase transitions. Almost 90% of the data is accounted for by less than 10 methods. Differential scaiming calorimetry strongly dominates the field with two thirds of all phase transition records. From the other experimental techniques, various fluorescent methods account for 10% of the information records. X-ray diffraction, nuclear magnetic resonance (NMR), Raman spectroscopy, electron spin resonance (ESR), infrared (IR) spectroscopy, and polarizing microscopy each contribute to about or less than 2-3% of the phase transition data records in the database. Especially useful in gaining insight into the mechanism and kinetics of lipid phase transitions has been time-resolved synchrotron X-ray diffraction (62,78-81). 

The optical layout for the measurement of biological samples (cells) is shown in Figure 29.3b. The sample was irradiated with co-linear IR and visible light beams. The transient fluorescence from the sample was collected from the opposite side by an objective lens. In this optical layout, the spatial resolution was determined by the objective numerical aperture (NA) and the visible fluorescence wavelength IR superresolution smaller than the diffraction limit of IR light was achieved. Here, Arabidopsis thaliana roots stained with Rhodamine-6G were used as a sample. We applied this super-resolution infrared microscope to the Arabidopsis thaliana root cells, and also report the results of time-resolved measurements. 

We have performed super-resolution infrared microscopy by combining a laser fluorescence microscope with picosecond time-resolved TFD-IR spectroscopy. In this chapter, we have demonstrated that the spatial resolution of the infrared microscope improved to more than twice the diffraction limit of IR light. It should he relatively straightforward to improve the spatial resolution to less than 1 pm by building a confocal optical system. Thus, in the near future, the spatial resolution of our infrared microscope will be improved to a sub-micron scale. 

Transient terahertz spectroscopy Time-resolved terahertz (THz) spectroscopy (TRTS) has been used to measure the transient photoconductivity of injected electrons in dye-sensitised titanium oxide with subpicosecond time resolution (Beard et al, 2002 Turner et al, 2002). Terahertz probes cover the far-infrared (10-600 cm or 0.3-20 THz) region of the spectrum and measure frequency-dependent photoconductivity. The sample is excited by an ultrafast optical pulse to initiate electron injection and subsequently probed with a THz pulse. In many THz detection schemes, the time-dependent electric field 6 f) of the THz probe pulse is measured by free-space electro-optic sampling (Beard et al, 2002). Both the amplitude and the phase of the electric field can be determined, from which the complex conductivity of the injected electrons can be obtained. Fitting the complex conductivity allows the determination of carrier concentration and mobility. The time evolution of these quantities can be determined by varying the delay time between the optical pump and THz probe pulses. The advantage of this technique is that it provides detailed information on the dynamics of the injected electrons in the semiconductor and complements the time-resolved fluorescence and transient absorption techniques, which often focus on the dynamics of the adsorbates. A similar technique, time-resolved microwave conductivity, has been used to study injection kinetics in dye-sensitised nanocrystalline thin films (Fessenden and Kamat, 1995). However, its time resolution is limited to longer than 1 ns. 

Rate constants for reaction of the CH radical with a number of atomic and molecular collision partners have been reported, with multiple-photon dissociation of suitable precursor molecules using either infrared or ultraviolet " laser radiation used as the pulsed photolysis source, and laser-induced fluorescence near 431 nm employed as a sensitive time-resolved detection method. A similar technique has been used to measure removal rates of CH2 and CDj with... 

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