Instrumentation For Multidimensional Luminescence Spectroscopy And Its Application To Low-Temperature Analysis In Shpol\u27Skii Matrixes And Optically Scattering Media

We present a single instrument with the capability to collect multidimensional data formats in both the fluorescence and the phosphorescence time domains. We also demonstrate the ability to perform luminescence measurements in highly scattering media by comparing the precision of measurements in Shpol\u27skii solvents to those obtained in snowlike matrixes and solid samples. For decades, conventional low-temperature methodology has been restricted to optically transparent media. This restriction has limited its application to organic solvents that freeze into a glass. We remove this limitation with the use of cryogenic fiber-optic probes. © 2006 American Chemical Society

Measuring Scatter With A Cryogenic Probe And An Iccd Camera: Recording Absorption Spectra In Shpol\u27Skii Matrixes And Fluorescence Quantum Yields In Glassy Solvents

Recording absorption spectra via transmittance through frozen matrixes is a challenging task. The main reason is the difficulty in overcoming the strong scattering light reaching the detector. This is particularly true when thick samples are necessary for recording absorption spectra of weak oscillators. In the case of strongly fluorescent compounds, additional errors in absorbance measurements arise from the emission reaching the detector, which might have an intensity comparable to that of the transmitted light. This article presents a fundamentally different approach to low-temperature absorption measurements as the sought for information is the intensity of laser excitation returning from the frozen sample to the ICCD. Laser excitation is collected with the aid of a cryogenic fiber optic probe. The feasibility of our approach is demonstrated with single-site and multiple-site Shpol\u27skii systems. The 4.2 K absorption spectra show excellent agreement with their literature counterparts recorded via transmittance with closed-cycle cryogenators. Fluorescence quantum yields measured at room temperature compare well to experimental data acquired in our laboratory via classical methodology. Similar agreement is observed between 77 K fluorescence quantum yields and previously reported data acquired with classical methodology. We then extend our approach to generate original data on fluorescence quantum yields at 4.2 K. © 2007 American Chemical Society

Exploring The Multidimensionality Of High-Resolution Luminescence Spectroscopy To Generate High-Order Data For Multivariate Calibration Methods

This chapter provides an overview of experimental and instrumentation developed in the author\u27s lab to take full advantage of the multidimensional nature of line narrowing spectroscopy at liquid nitrogen (77. K) and liquid helium (4.2. K) temperatures. The inconvenience of sample freezing procedures was eliminated with the aid of cryogenic fiber optic probes. Rapid collection of excitation-modulated wavelength time matrices (EMWTMs) and time-resolved excitation-emission cubes (TREECs)-in both the fluorescence and the phosphorescence time domains-is made possible with the combination of a pulsed tunable dye laser, a spectrograph and an intensifier-charged coupled device. 4.2. K EMWTMs and 4.2. K TREECs provide unique opportunities for processing vibrational luminescence data with second-order multivariate calibration algorithms. Applications of parallel factor analysis and U-PLS/RTL to 4.2. K EMWTMs and 4.2. K TREECs provide a general solution to unpredictable spectral interference, a ubiquitous problem for the analysis of organic pollutants in environmental samples of unknown composition. © 2015 Elsevier B.V

Determination of high-molecular weight polycyclic aromatic hydrocarbons in high performance liquid chromatography fractions of coal tar standard reference material 1597a via solid-phase nanoextraction and laser-excited time-resolved Shpol'skii spectroscopy

This article presents an alternative approach for the analysis of high molecular weight – polycyclic aromatic hydrocarbons (HMW-PAHs) with molecular mass 302 Da in complex environmental samples. This is not a trivial task due to the large number of molecular mass 302 Da isomers with very similar chromatographic elution times and similar, possibly even virtually identical, mass fragmentation patterns. The method presented here is based on 4.2 K laser-excited time-resolved Shpol'skii spectroscopy, a high resolution spectroscopic technique with the appropriate selectivity for the unambiguous determination of PAHs with the same molecular mass. The potential of this approach is demonstrated here with the analysis of a coal tar standard reference material (SRM) 1597a. Liquid chromatography fractions were submitted to the spectroscopic analysis of five targeted isomers, namely dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, naphtho[2,3-a]pyrene and dibenzo[a,h]pyrene. Prior to analyte determination, the liquid chromatographic fractions were pre-concentrated with gold nanoparticles. Complete analysis was possible with microliters of chromatographic fractions and organic solvents. The limits of detection varied from 0.05 (dibenzo[a,l]pyrene) to 0.24 μg L(−1) (dibenzo[a,e]pyrene). The excellent analytical figures of merit associated to its non-destructive nature, which provides ample opportunity for further analysis with other instrumental methods, makes this approach an attractive alternative for the determination of PAH isomers in complex environmental samples