Use of a Sample Translation Technique to Minimize Adverse Effects of Laser Irradiation in Surface-Enhanced Raman Spectrometry

Abstract

Surface-enhanced Raman spectroscopy (SERS) has proven to be a very powerful tool in the analysis of a wide range of compounds. However, continuous irradiation of the laser beam over the SERS substrate can promote the gross decomposition of the sample analytes and significantly broaden and diminish the intensities of observed spectral bands. In addition, the incident radiation can promote thermal or photolytic fragmentation of analytes, thereby altering the observable bands and possibly leading to a misinterpretation of analytical data. Finally, chemical or morphological changes in the SERS substrate are possible. This work presents the use of a sample translation technique (STT) as a means to minimize these adverse effects. By spinning the sample rapidly, the effective residence time of analytes and substrate within the irradiated zone is dramatically decreased without reduction of spectral acquisition time or the density of analyte in the zone. The technique is studied by acquiring SERS spectra of Naproxen USP, riboflavin, folic acid, Rhodamine 6G, and 4-aminothiophenol using silver islands on glass and silver-poly(dimethylsiloxane) composite substrates under various spinning and stationary conditions. In all cases, spectra show improvements upon spinning at laser powers as low as 4.2 (+/- 0.1) mW. Specific differences in the appearance of the spectra and the potential use of STT for improved SERS qualitative and quantitative determinations are presented.

Analytical optimization of nanocomposite surface‐enhanced Raman spectroscopy/scattering detection in microfluidic separation devices

“…Experimentally, this is revealed by following the decreasing ratio of a prominent, descriptive resorufin band at 573 cm 21 to the graphitic carbonaceous band, a harbinger of polymer and resorufin degradation, at 740-950 cm 21 (Fig. 3a).…”

“…The stage was then reprogrammed to take smaller steps with averaging of three latitudinal spatially distinct spectra within the same longitudinal location along the channel's length. This step recreates the electrophoretic band shape by following the intensity of resorufin's vibrational band at 573 cm 21 . Raman data was processed with LabSpec software, Version 4.03.…”

Hybrid Micro-Electro-Mechanical Systems for Highly Reliable and Selective Characterization of Tank Waste

“…This ensures that neither of the two adjacent MCs have been coated with the phase that has been applied to the MC shown. This coating approach has been applied to the measurement of a mixture of quinoxaline and 8-hydroxyquinoline in solution by coating two adjacent MCs with calix [6]arene and calix [8]arene, respectively.…”

“…We discovered that the photodegredation problem can be overcome by very effectively rastering the laser spot onto new areas of the SERS substrate to prevent photodegredation without loss of signal. 8 The long desorption times of adsorbed molecules is a more complex problem that may require the development of thermal desorption methods.…”

Chemically Functionalized Arrays Comprising Micro and Nano-Electro-Mechanizal Systems for Reliable and Selective Characterization of Tank Waste

“…This coating approach has been applied to the measurement of a mixture of quinoxaline and 8-hydroxyquinoline in solution by coating two adjacent MCs with calix [6]arene and calix [8]arene, respectively. Calibration curves were obtained for each analyte independently using each phase and response factors were calculated using this data.…”