Abstract
The goal of this thesis was to study, determine, and measure Raman and surface-enhanced Raman spectroscopy (SERS) of fatty acids and lipids. Firstly, the Raman measurement was done using silver substrate where the activation process was achieved by focusing crystals of green laser radiation 5 mW power at 5 minutes on the silver substrate. The Raman measurement again was done using Invia Raman Spectroscopy with 514 nm excitation and objective 100x magnification where the samples to be measured were incubated using RH6G (good signal analyzer). After the incubation process, the samples were rinsed with water and allowed to dry for 5 minutes where ten samples of fatty acids and lipids were measured, recorded, saved and baseline of the spectra’s were corrected using matlab codes and averaged. Secondly the SERS measurement was done by growing silver chloride nanoparticle on the silver substrate where the substrate was dipped in a precursor solution of silver nitrate and sodium chloride in a cyclic process. The photosensitive silver chloride crystals were reduced into silver nanoparticles using laser light from the Invia Raman spectroscopy. The SERS measurement was done by depositing the fatty acids and lipids to be measured on the spot which contains the silver nanoparticle recorded the values, saved and baseline of the spectra’s corrected using MatLab codes and averaged. This thesis work reveals that, the peaks obtained by the Raman and SERS measurement originated from the double bonds which was used to identify saturated and unsaturated fatty acids and lipids from one another. The study reveals that, the Raman measurement occurs at higher concentrations whereas the SERS measurement occurs at lower concentrations. The study reveals that the SERS measurement depends on the nature of the analyte, integration time, shape, size and laser power whereas the Raman measurement depends on the surface area and laser power. Lastly, the study reveals that the 514 nm excitation was negligible to efficiently execute the surface Plasmons of the SERS measurement.
Highlights
Fatty acid and lipids biology The identification and investigation of lipids and fatty acids started in the 17th, 18th, 19th, and 20th centuries where researchers used non-optical methods to investigate various structure of lipids and fatty acids
Solvent Preparation part of methanol and 1 part of chloroform were used in the preparation where 5mg of fatty acids and glycerides each were dissolved in 500μl of MetOH: chloroform 2:1 with fatty acid content of 10mg/ml
It clearly shows that, the peak at both 2825 1/cm and 2950 1/cm exhibited some double bonds which could be used to identify both saturated, unsaturated, polysaturated and polyunsaturated fatty acid from one another Again there were higher intensity counts with low signalto-noise ratio
Summary
Fatty acid and lipids biology The identification and investigation of lipids and fatty acids started in the 17th, 18th, 19th, and 20th centuries where researchers used non-optical methods to investigate various structure of lipids and fatty acids. The following fatty acids and glycerides were studied and characterized using Raman and Surface- Enhanced Raman Spectroscopy (SERS). 16:1 FA = palmitoleic acid eli cis-9-hexadecenoic acid (omega-7) 16:0 FA = palmitic acid eli hexadecanoic acid 18:1 FA = oleic acid eli cis-9-octadecenoic acid (omega-9). 18:0 FA = stearic acid eli octadecanoic acid 18:2 MAG = sn-1 (sn-3) -linoleic acid MAG 18:0 MAG = sn-1 (sn-3) -stearic acid MAG 18:1/18:0 PC = sn-3-phosphatidylcholine-sn-2-oleic acidsn-1-stearic acid glycerol 22:6/18:0 PC = sn-3-phosphatidylcholine-sn-2docosahexanoic acid-sn-1-stearic acid glycerol. The motivation of this thesis is to identify the spectra ranges of the samples where the peaks originated from, biological difference, various bond position (length), chemical point and measuring point. The library of different lipids and fatty acids spectra’s will be kept and compared with spectra of other constituents. Eric Amankwa: Raman and Surface-Enhanced Raman Spectroscopy of Fatty Acids and Lipids The uses, features and analyses of fatty acids and lipids are introduced.
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