Singlet Oxygen Luminescence

The FluoTime 300 photoluminescence spectrometer alone or in combination with the MicroTime 100 confocal laser scanning microscope can be used to study singlet oxygen luminescence. A combination set-up will provide spatial information in addition to the lifetime data.

The sample is excited by a pulsed laser, LED or Xe-flash lamp in time-resolved experiments, or by a Xe lamp or a CW laser in steady-state experiments and the emitted singlet oxygen phosphorescence is detected by using a NIR sensitive detector after emission wavelength selection by a monochromator.

For lifetime measurements, either a Time-Correlated Single Photon Counting (TCSPC) or Multi-Channel Scaling (MCS) unit is used for data acquisition.

Consequently the essential components of a spectrometer set-up are:

• pulsed or CW excitation source
• monochromator
• single photon sensitive detector in the NIR
• for lifetime measurements: TCSPC or MCS unit to record lifetimes ranging from ps to ms

PicoQuant offers the following system capable of detecting singlet oxygen luminescence:

FluoTime 300

Fully Automated High Performance Fluorescence Lifetime Spectrometer

The FluoTime 300 "EasyTau" is a fully automated, high performance fluorescence lifetime spectrometer with steady-state and phosphorescence option. It contains the complete optics and electronics for recording fluorescence decays by means of Time-Correlated Single Photon Counting (TCSPC) or Multichannel Scaling (MCS). The system is designed to be used with picosecond pulsed diode lasers, LEDs or Xenon lamps. Multiple detector options enable a large range of system configurations. With the FluoTime 300 decay times down to a few picoseconds can be resolved.

MicroTime 100

Upright time-resolved confocal microscope

The MicroTime 100 is an idea tool for the study of time-resolved photoluminescence of solid samples such as wafers, semiconductors or solar cells. It can also be used for mapping purposes or to measure intensity dependent TRPL. The system is based on a conventional upright microscope body that permits easy access to a wide range of sample shapes and sizes. The MicroTime 100 can be supplied with either manual scanning or with a 2D piezo scanner with either µm or cm resolution..

The following core components are needed to build a system capable of fluorescence upconversion measurements, which are partly available from PicoQuant:

• Laser drivers
  • PDL 800-D
  • Taiko PDL M1
  • PDL 828 "Sepia II"
• Laser or LED heads
  • LDH Series
  • LDH-FA Series
  • PLS Series
• Photon Counting Detector
  • UV/Vis sensitive PMA Hybrid Series
  • UV/Vis sensitive Photomultiplier Detector Assembly
  • NIR sensitive NIR Photomultiplier Detector
• TCSPC and MCS Electronics
  • PicoHarp 300
  • TimeHarp 260 PICO (with long range mode)
  • TimeHarp 260 NANO
• Analysis software
  • EasyTau 2
  • SymPhoTime 64

H₂TTP as sensitizer for singlet oxygen generation

The first graph displays the steady-state emission spectra of singlet oxygen generated by H₂TTPS in acetone or H₂O. The latter is especially challenging due to a spectral overlap of water and singlet oxygen emission peaks. The second graph shows the time-resolved singlet oxygen decay recorded using the burst mode of the FluoTime 300. In burst mode, multiple laser pulses are used to pump excitation energy into the sample over a time range. Excitation is then stopped long enough to capture the comparably slow decay of the sample phosphorescence. A tail fit yields a lifetime of 3.4± 0.3 µs, which is in excellent agreement with published literature values.

Set-up:

• FluoTime 300
• Excitation source: LDH-P-C-405
• Excitation wavelength: 405 nm, burst mode
• Detector: H01033-45 (Hamamatsu)

Steady-state and time-resolved singlet oxygen luminescence of Zn-phthalocyanin

Singlet oxygen measurements can also be performed using a microscope stage (e.g., MicroTime 100) set to wide field illumination and connected via a 600 µm fiber to the spectrometer. The fiber acts as a pinhole, i.e. the detection volume is smaller than the excitation volume. This set-up allows recording both the phosphorescence decay as well as the emission spectrum from the confocal volume. In this experiment, the burst mode was also used to excite the photosensitiziser (Zn-phthalocyanin in aceton), which resulted in generation of singlet oxygen.

Set-up:

• MicroTime 100 coupled to FluoTime 300
• Excitation: 660 nm using a LDH-P-C-660 operated in pulsed burst mode using a PDL 828
• Detector: H01033-45 (Hamamatsu)
• Analysis: EasyTau 2