An Inexpensive, Pulsed, and Multiple Wavelength Bench-Top Light Source for Biological Spectroscopy

Abstract

Since signal/noise ratios are proportional to the square root of the intensity, high intensity light sources are advantageous for many forms of UV–Vis and IR spectroscopy particularly with very low or high absorbance samples. We report the construction of a low-cost (≈ £6500 GBP, ca. 2016) bench-top spectrometer suitable for biological spectroscopy, which utilizes a hot plasma, generated with a pulsed Nd:YAG laser (λ = 1064 nm). The properties (reliability, intensity, and spectral profiles) of light generated with the plasma in different gaseous media (helium, neon, argon, and krypton) were investigated. Argon provided high intensity broadband light and was the most cost effective. The instrument was compared for spectral accuracy to a commercially available spectrometer (Thermo Scientific, GENESYS 10S) by measurement of the absorbance spectrum of the UV–Vis calibration standard holmium (III) oxide (4%, w/v) in perchloric acid (10%, w/v) and accurately replicated the results of the commercial spectrometer. This economical instrument can record consecutive absorbance spectra (between λ = 380 and 720 nm) for each laser pulse (6 Hz; ~160 ms/pulse), evinced by investigations into lysozyme aggregation in the presence of heparin. This instrument is suitable for use with lasers of a higher pulse power and repetition rates that would induce higher temperature plasmas. Higher temperature plasma sources offer increased signal to noise ratios due to the higher intensity emission generated.