Time-Resolved Laser-Excited Shpol'skii Spectrometry with a Fiber-Optic Probe and ICCD Camera

Abstract

Improved methodology for chemical analysis via laser-excited Shpol'skii spectrometry is reported. The complications of traditional methodology for measurements at liquid nitrogen temperature are avoided by freezing the distal end of a bifurcated fiber-optic probe directly into the sample matrix. Emission wavelength-time matrices were rapidly collected by automatically incrementing the gate delay of an intensified charge-coupled device (ICCD) camera relative to the laser excitation pulse. The excitation source is a compact frequency-doubled tunable dye laser whose bandwidth (<0.03 nm) is well matched for Shpol'skii spectroscopy. Data reproducibility for quantitative analysis purposes and analytical figures of merit are demonstrated for several polycyclic aromatic hydrocarbons at 77 K. Although not attempted in this study, time-resolved excitation-emission matrices could easily be collected with this instrumental system.

Instrumentation to rapidly acquire fluorescence wavelength-time matrices of biological tissues

“…2Schematic of the instrumentation developed for rapid acquisition of fluorescence WTMs, using fiber-optic probes for light delivery and detection (set-up 4, Table 1). WTMs were also obtained with three other set-ups (Table 1): (1) right-angle free-space geometry, in place of the fiber-probes, for light delivery and detection; (2) free-space light delivery and a fiber-probe for fluorescence detection; (3) a fiber-probe for light delivery and right-angle free-space geometry for detection.) consisted of a 473 nm microchip laser (Lumanova, 20-030005, µFlare Blue, 3 kHz pulse repetition rate, ~2 ns pulse duration), a specialized transient digitizer (Fluorescence Innovations (FI), Inc., Bozeman, MT) for WTM measurement [24–26], a scanning monochromator (Optometrics, MC1-03), and a photo-multiplier tube (PMT) (Hamamatsu, H6780-20).…”

Laser-Excited Time-Resolved Shpol'skii Spectroscopy for the Direct Analysis of Dibenzopyrene Isomers in Liquid Chromatography Fractions

“…Measurements were made with the aid of an instrumental setup previously described. [9][10][11] Samples were excited with the output of a Northern Lights tunable dye laser (Dakota Technologies, Inc.) through a KDP frequency-doubling crystal. The dye laser was operated on DCM (Exciton) and it was pumped with the second harmonic of a 10 Hz Nd : YAG Q-switched solid-state laser (Big Sky Laser Technologies).…”

“…In this article, we present improved Shpol'skii methodology to directly determine DB[a,l]P and its four dibenzopyrene isomers in HPLC fractions. Our approach, which we have named laser-excited time-resolved Shpol'skii spectroscopy (LETRSS), 9,10 eliminates the well-known disadvantages of conventional low-temperature measurements with the aid of a cryogenic fiber-optic probe. Fluorescence decay data, which results in information-rich multidimensional data formats, is efficiently collected with a frequency-doubled tunable dye laser, a spectrograph, a pulsed delay generator, and an intensified charge-coupled device (ICCD).…”

Novel clinical technology for rapid detection of tissue fluorescence wavelength-time matrices

“…Wavelength-time matrices (WTMs) of fluorescence intensity temporal decay at different wavelengths (illustrated in Fig. 2) can be acquired with the specialized digitizer described above [4][5][6]. The WTM contains two dimensions of fluorescence intensity information: wavelength-resolved and time-resolved.…”