Sequentially Shifted Excitation Raman Spectroscopy: Novel Algorithm and Instrumentation for Fluorescence-Free Raman Spectroscopy in Spectral Space

Abstract

A novel Raman spectrometer is presented in a handheld format. The spectrometer utilizes a temperature-controlled, distributed Bragg reflector diode laser, which allows the instrument to operate in a sequentially shifted excitation mode to eliminate fluorescence backgrounds, fixed pattern noise, and room lights, while keeping the Raman data in true spectral space. The cost-efficient design of the instrument allows rapid acquisition of shifted excitation data with a shift time penalty of less than 2 s. The Raman data are extracted from the shifted excitation spectra using a novel algorithm that is typically three orders of magnitude faster than conventional shifted-excitation algorithms operating in spectral space. The superiority of the instrument and algorithm in terms of background removal and signal-to-noise ratio is demonstrated by comparison to FT-Raman, standard deviation spectra, shifted excitation Raman difference spectroscopy (SERDS), and conventional multiple-shift excitation methods.

Surface oxygenation of biochar through ozonization for dramatically enhancing cation exchange capacity

“…The spectrometer has been described in detail previously (Cooper et al 2013(Cooper et al , 2014. The excitation wavelength was adjusted 32 times by setting the temperature of the laser to predetermined values that provide 1 cm −1 spacing between each shift.…”

Miniaturized time-resolved Raman spectrometer for planetary science based on a fast single photon avalanche diode detector array

“…Recently, shifted excitation methods for extracting Raman information from interfering backgrounds have been gaining widespread use in the laboratory and portable Raman spectrometers using 532 to 785 nm sources, as a means for mitigating fluorescence interference [24][25][26][27]. These methods have been applied to a wide variety of samples with great success for dealing with background interference.…”

Rapid and adjustable shifted excitation Raman difference spectroscopy using a dual‐wavelength diode laser at 785 nm

“…A more compact solution is presented by Cooper et al Here, a distributed Bragg reflector (DBR) diode laser at 785 nm is mounted on a Peltier element. The emission wavelength is adjusted by changing the temperature at the semiconductor device to provide several excitation lines to perform sequentially SERDS .…”