Novel Surface Enhanced Raman Spectroscopy (SERS) sensors
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Full Text E-thesis
Date
2022
Authors
Yang, Yuqing
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Publisher
University College Cork
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Abstract
Surface Enhanced Raman Spectroscopy (SERS)-based sensors and devices offer rapid, cost-effective, highly selective, and sensitive detection of various chemicals in water. This thesis explores the SERS principle, substrate fabrication methods, functionalization techniques, and their applications. It also addresses the limitations of SERS sensing devices, including cross-contamination during application and challenges in fabrication reproducibility.
The fabricated sensors were based on Ag-Gum Arabic nanostructures for the detection of 2,4-D in Chapter 2, Ag-Corn Starch nanostructures for MCPA in Chapter 3, and Ag NPs/ss-DNA in Chapter 3. The nanoparticles were synthesized using an electrochemical deposition method, which enables tailoring of the nanoparticle structure by adjusting parameters such as deposition time, precursor concentrations, and applied voltage. This method is straightforward and repeatable, making the sensor fabrication process highly reproducible.
In Chapters 2 and 3, no significant changes in Raman signal intensities were observed as the analyte concentrations increased, contrary to what would typically be expected with SERS effects. Instead, a slight increase in the ratio between two peaks of the Raman spectra was noted. This may be attributed to a local increase in pesticide concentration caused by the polysaccharide polymer layers of Gum Arabic and Corn Starch. Although changes in the ratio between two peaks were detectable as the concentration increased, quantification was not feasible due to the low slope obtained and the inadequacy of the experimental procedure, which involved oversampling. Additionally, the recorded spectra for the two pesticides were very similar, rendering selectivity unachievable.
For the E. coli O157 ss-DNA SERS sensor, neither Gum Arabic nor Corn Starch was used. Instead, a two-thiol functionalization method was employed for the development of the Ag nanoparticle SERS ss-DNA sensor. This ss-DNA SERS sensor demonstrated good linearity, selectivity, and relatively fast detection compared to other sensors or methods used for ss-DNA detection.
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Keywords
Surface Enhanced Raman Spectroscopy , Ag nanoparticles , Electrochemical deposition , Chemical sensor , Biosensor , Micro/nano device
Citation
Yang, Y. 2022. Novel Surface Enhanced Raman Spectroscopy (SERS) sensors. PhD Thesis, University College Cork.