Time-correlated single photon counting spectroscopy

D. J. S. Birch and R. E. Imhof, Time-domain fluorescence spectroscopy using time-correlated single-photon counting, in Topics in Fluorescence Spectroscopy (J. R. Lakowicz, ed.), Vol. 1, pp. 1-95, Plenum Press, New York (1991). 

Most of the time-resolved emission spectroscopy setups are home made in the sense that they are built from individual devices (laser, detection system,. ..) hence they are not of a plug and press type, so that their exact characteristics may vary from one installation to the other. Some of these differences have no impact on the overall capabilities of the system but some have a drastic influence on the way the collected data are processed and analysed. This aspect will be detailed in the next section, while this section deals with a general description of the apparatus. The most basic type of apparatus will be described, with no reference to sophisticated techniques such as Time Correlated Single Photon Counting or Circularly Polarized Luminescence devices. 

Three techniques are actually available for measuring the fluorescence lifetime Strobe, Time Correlated Single Photon Counting (TCSPC), and multifrequency and crosscorrelation spectroscopy. Strobe and TCSPC are based on measurement in the time domain, while multifrequency and cross-correlation spectroscopy measure fluorescence lifetimes in the frequency domain. The time domain allows direct observation of fluorescence decay, while the frequency domain is a more indirect approach in which the information regarding the fluorescence decay is implicit. 

The rotational reorientation times of the sample in several solvents at room temperature were measured by picosecond time-resolved fluorescence and absorption depolarization spectroscopy. Details of our experimental setups were described elsewhere. For the time-correlated single photon counting measurement of which the response time is a ut 40 ps, the sample solution was excited with a second harmonics of a femtosecond Ti sapphire laser (370 nm) and the fluorescence polarized parallel and perpendicular to the direction of the excitation pulse polarization as well as the magic angle one were monitored. The second harmonics of the rhodamine-640 dye laser (313 nm 10 ps FWHM) was used to raesisure the polarized transient absorption spectra. The synthesis of the sample is given elsewhere. All the solvents of spectro-grade were used without further purification. 

When the experimental system emits light after the initial pumping pulse, quite different techniques can be used to obtain a time-resolved spectrum of the sample emission. The simplest of these is time-correlated single photon counting. The time resolution of this technique is limited by the design of the photon detectors. Two other methods used in emission spectroscopy are the streak camera and... 

Time-resolved PL measurements were also performed using time-correlated single-photon counting (TCSPC) and photoluminescence upconversion (PLUC) spectroscopies. Descriptions of the setups can be found in refs. [14, 65], respectively. All measurements were taken in continuous-flow He cryostats (Oxford Instruments OptistatCF) under inert conditions. Finally, PL efficiency measurements were performed on simple polymer thin films spin coated on Spectrosil substrates using an integrating sphere coupled to an Oriel InstaSpec IV spectrograph and excitation with the same Ar+ laser as above. 

W. Becker, A. Bergmann, G. Biscotti, A. Rtick, Advanced time-correlated single photon counting technique for spectroscopy and imaging in biomedical systems, Proc. SPIE 5340, 104-112 (2004)... 

Steady-state and time-resolved fluorescence spectroscopy Absorption and fluorescence spectra were measured with a Hitachi 557 spectrophotometer and a Hitachi 850 spectrofluorometer, respectively. The time-resolved fluorescence spectra were measured with the apparatus reported previously [4,6] in principle, the time-correlated single photon counting system under a low excitation condition. The pulse intensity (540 nm, 6 ps (fwhm)) was in a range of 10 to 10 photons/cm. The time resolution of our optical set-up was 6 ps. Correction of spectral sensitivity and data treatment were carried out as reported previously [4,6]. 

We have studied the microsecond and nanosecond kinetics of the D1/D2 reaction centre by time correlated single photon counting and transient absorption spectroscopy. Stabilisation of the reaction centre has been necessary to establish the kinetics correctly. 

FCS fluorescence correlation spectroscopy PCH photon counting histogram TCSPC time correlated single photon counting MCS muiti-channei scaiar APDiavaianche photodiode PMT photo-mutipiiertube PCi peripherai component interconnect. 

We have also performed time resolved studies (time correlated single photon counting dispersed emission spectroscopy) on all of the above emission spectral features. An example of the data typically obtained is presented in Figure 4. This figure shows that the decay... 

New techniques have demonstrated how fast a cyclization can be. Thus, investigation by means of femtosecond-microsecond transient absorption spectroscopy and a time-correlated single-photon counting method of the photoreaction of l,2-bis(2-methyl-3-benzothienyl)perfluorocyclopentene in nonpolar alkane solutions with different viscosities revealed that a ring closure rapidly occurred with a time constant of 450 fs from the antiparallel form, while from the triplet the predominating path was intersystem crossing to the Tj state [5] (Scheme 11.2). 

Harris describe a method for the quantitative estimation of component amplitudes in multiexponential data obtained from time-resolved fluorescence spectroscopy. A design of apparatus which uses time correlated and single photon counting with alternate recording of excitation and emission minimises troublesome lamp... 

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