Layer-by-layer chitosan and gold nanoparticles as surface-enhanced Raman scattering substrate

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2024-04, Vol.26 (4), p.74, Article 74
• Main Authors: de Melo Toledo, Paulo Henrique, de Faria Peixoto, Linus Pauling, Fragneaud, Benjamin, Fernandes Souza Andrade, Gustavo
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Bilayers; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chitosan; Gold; Infrared spectroscopy; Inorganic Chemistry; Lasers; Low concentrations; Materials Science; Nanoparticles; Nanotechnology; Optical Devices; Optics; Pesticides; Photonics; Physical Chemistry; Polysaccharides; Raman spectra; Raman spectroscopy; Reducing agents; Signal monitoring; Sodium citrate; Substrates
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-024-05982-9

The layer-by-layer (LbL) method demonstrates significant versatility for constructing substrates with nanoscale-thick layers and diverse compositions. This technique is based on alternate deposition of species that interact electrostatically. Studies have demonstrated that this technique holds promise for use as a surface-enhanced Raman scattering (SERS) substrate, enabling the detection of pesticides at low concentrations and finding applications in the biological field. In this study, a simple methodology based on the layer-by-layer (LbL) method was developed to construct SERS substrates. Substrates with varying numbers of bilayers (1, 5, or 10) were built on glass slides. The positive layer was composed of the natural polysaccharide chitosan. In contrast, the negative layer consists of gold nanoparticles (AuNPs) with a negative charge on their surface, achieved using sodium citrate as a reducing agent. The SERS substrates were characterized by UV–VIS-NIR spectroscopy and atomic force microscopy (AFM). They were tested as SERS substrates by utilizing thiophenol (TP) at a concentration of 1.0 × 10 –3  mol L −1 . The distribution of the SERS signal was monitored through the 417 cm −1 peak, which is attributed to the CH stretching mode characteristic of TP. The substrates exhibited a more significant enhancement with an increase in the number of bilayers. They have proven highly promising for future applications, such as diagnostic evaluation of diseases, detection of pesticide molecules, biological molecules, and various other applications.