PROCEEDINGS ARTICLE | October 17, 2006
Proc. SPIE. 6377, Advanced Environmental, Chemical, and Biological Sensing Technologies IV
KEYWORDS: Gold, Continuous wave operation, Nanoparticles, Spectroscopy, Luminescence, Laser induced fluorescence, Surface enhanced Raman spectroscopy, Raman spectroscopy, Raman scattering, Bacteria
Raman and Laser Induced Fluorescence (LIF) spectroscopic techniques were used for studying Azotobacter vinelandii- a genus of free-living diazotrophic soil bacteria. Azotobacter has generated a great deal of interest owing to their unique mode of metabolism. It is a large, obligately aerobic soil bacterium, which has one of the highest respiratory rates known among living organisms and is able to grow on a wide variety of carbohydrates, alcohols and organic acids. The Raman Scattering of Azotobacter, incubated with gold nanoparticles, was examined with 532-nm as an excitation laser wavelength. The basic instrumentation for characterizing the bacteria by Raman spectroscopy employed a continuous wave (CW) frequency doubled Nd: YAG laser (532-nm) and a modified In-Photonics fiber optic state-of-art miniaturized Raman Probe. The surface enhancement effects allowed the observation of Raman spectra of such bacterial cells, and were excited in the visible region of wavelength at low incident power for minimum sample degradation. LIF spectra of Azotobacter were measured with a 410-nm CW diode laser as an excitation source, and a reflection probe to deliver laser beam on the sample and collect the LIF signal from the sample. Spectral contrast observed in gold particles conjugated bacteria, from nitrogen fixing and non-nitrogen fixing condition was analyzed for characterizing the bacteria cells, and the results are presented in the paper.
