The effect of silver thickness on the enhancement of polymer based SERS substrates

Large-area Co(OH)2 Nanoflower Array Films Decorated with Ag Nanoparticles as Sensitive SERS Substrates

A novel structure of large-area three-dimensional (3D) well-ordered Co(OH)2 nanoflower array films decorated with Ag nanoparticles (Ag NPs) was designed as sensitive SERS substrates for trace detection of pesticides. Co(OH)2...

Silver-chitosan nanocomposite as a plasmonic platform for SERS sensing of polyaromatic sulfur heterocycles in oil fuel

Herein, a silver-chitosan nanocomposite for application in surface enhanced Raman spectroscopy (SERS) sensing was proposed. It was shown that optically transparent chitosan coatings with 0.8 μm thickness allow penetration of target analytes to silver nanoparticles and the analysis in both polar and nonpolar solvents. Under the chosen conditions, chitosan formed continuously smooth films and coatings stabilizing rough nanostructured metallic surfaces and served as a suitable matrix for immobilization, uniform spreading, and preconcentration of the analytes. Polycyclic aromatic sulfur heterocycles were chosen as target analytes being one of the most important fuel quality markers, hazardous components, and the hardest-to-remove impurities. For the most effective immobilization and even distribution of the analytes onto a nanostructured metallic surface, an additional polymer layer of chitosan was found to be needed. The presence of thin films of chitosan resulted in higher reproducibility of SERS spectra as compared to bare nanostructured silver substrates. Additionally, the developed nanocomposite SERS sensors provided the rapid determination of dibenzothiophene and its derivatives in isooctane with the threshold of detection better than 0.1 μM. This approach was successfully applied in the analysis of real fuel samples and the results agreed well with independently measured FTIR and GC-MS data.

Enhancement of Single Molecule Raman Scattering using Sprouted Potato Shaped Bimetallic Nanoparticles

Herein, for the first time, we report the single molecule surface enhanced resonance Raman scattering (SERRS) and surface enhanced Raman scattering (SERS) spectra with high signal to noise ratio (S/N) using plasmon-active substrates fabricated by sprouted potato shaped Au-Ag bimetallic nanoparticles, prepared using a new one-step synthesis method. This particular shape of the nanoparticles has been obtained by fixing the amount of Au and carefully adjusting the amount of Ag. These nanoparticles have been characterized using scanning electron microscopy, extinction spectroscopy, and glancing angle X-ray diffraction. The single molecule sensitivity of SERS substrates has been tested with two different molecular Raman probes. The origin of the electromagnetic enhancement of single molecule Raman scattering in the presence of sprouted shape nanoparticles has been explained using quasi-static theory as well as finite element method (FEM) simulations. Moreover, the role of (i) methods for binding Raman probe molecules to the substrate, (ii) concentration of molecules, and (iii) Au-Ag ratio on the spectra of molecules has been studied in detail.

Thickness of a metallic film, in addition to its roughness, plays a significant role in SERS activity

In this paper we evaluate the effect of roughness and thickness of silver film substrates, fabricated on glass and polydimethylsiloxane (PDMS) templates, on surface-enhanced Raman Spectroscopy (SERS) activity. While the silver substrates obtained on glass templates exhibit nm-scale roughness, the silver substrates on PDMS templates show larger roughness, on the order of 10 s of nm. These roughness values do not change significantly with the thickness of the silver film. The SERS intensities of 4-aminothiophenol (ATP) deposited on these substrates strongly depend on both roughness and thickness, with more significant contribution from the roughness on thinner films. FEM simulations of the electric field intensities on surfaces of different thicknesses for rough and flat surfaces suggest higher localized plamons on thinner, rough surfaces. This study indicates that, besides roughness, the thickness of the metallic layer plays a significant role in the SERS activity.