Study On The Design And Practical Application Of Paper-based Surface-enhanced Raman Spectroscopy Substrates

As one of promising powerful technique with high sensitivity, surface enhanced Raman spectroscopy (SERS) has been applied in various fields, including analytical chemistry, medical science, environmental monitoring, explosives analysis and so on. The majority of SERS studies are confined to laboratory investigation. From the application viewpoint, there still remains numerous considerations in the design of practical SERS substrates. As we know, most of conventional SERS substrates are based on silicon wafer, glass wafer, and porous alumina, which exists more or less drawbacks as a practical SERS substrate, such as high price, sophisticated preparation and treatment process. It is still a challenge to fabricate a sensitive, stable and practical SERS substrate.The first chapter made a simple introduction of the SERS development, enhancement mechanism, the main preparation methods and dynamic SERS technique. SERS substrates with applications in theoretical research and practical application were then introduced and summarized respectively. Owing to the low cost, portability, simplicity and flexibility of paper, the development of paper-based SERS device were presented.In chapter2, we fabricated a practical SERS substrate in a large area made up of Ag NPs decorated filter paper via simple silver mirror reaction at room temperature without complex reaction process. Ag NP-based paper substrates combined with D-SERS method revealed high SERS performance to CV molecules, including sensitivity, stability and reproducibility. All of these splendid properties used for the SERS substrates open up a new opportunity for Ag NP-based filter paper as practical SERS substrates.In chapter3, the excellent storage stability of paper substrate was deeply explored and reasonable explanation was given. It is difficult to realize local sample collection by conventional rigid substrates, such as silicon wafer, glass wafer. Additionally, the influence of surfaces on their own Raman signals can’t be eliminated by the technique that nanostructures were added to the surfaces. However, the prepared paper substrate can be used as a rag to collect samples in real world, which are incredibly difficult to rigid substrates. Here, pesticide residues were collected by simply swabbing the paper substrate across a wide-area surface of peels. Excellent detection performance was obtained by detection thiram and paraoxon residues at various peels, such as apples, bananas and tomatoes.In chapter4, different polyelectrolytes were decorated on the surface of Ag NP-based filter paper and the detection of pigments in drinks were realized by PSS-functionalized paper substrate. Analytes were concentrated by capillary attraction, surface chemical gradient and electrostatic interaction created by different polyelectrolyte coating of the paper. On the basis of this strategy, sunset yellow and lemon yellow in drinks were concentrated and detected successfully by polyelectrolyte-decorated paper substrate.At the end of this paper, we summarized the studies of preparation, functionalization and practical application of paper substrate, and proposed the outlook for future research.