Visualization of gold/silver nanostars in wood by surface enhanced Raman spectroscopy
C Geers, L Rodríguez-Lorenzo, M Placencia Peña, P Brodard, T Volkmer, B Rothen-Rutishauser, A Petri-Fink
Nanotechnology is a fast growing up-to-date technology and ventures expeditiously in the wood preservative market. However, there is still a huge lack of understanding about the interaction and incorporation of nanoparticles (NSs) in wood. Surface-enhanced Raman scattering (SERS) offers unique advantages as an analytical tool with a high selectivity and sensitivity without matrix interference. Here, we design and fabricate SERS-tagged silver/gold nanostars (NSs), coated with a silica shell encapsulating nile blue A (NBA), as potential platforms for SERS imaging. These NSs can be pressure-impregnated in different wood types (pine and beech) due their optimal size (< 100 nm), allowing for their rapid and accurate identification and localization in the wood samples. For comparison and visualization of the NSs, the samples were coated with a carbon layer for analysis in a scanning electron microscope (SEM). We demonstrate that SERS provides advantages over SEM. The NSs can be visualised by SERS without coating of the samples. In addition, no vacuum is needed to image the NSs, and the excitation laser line (633 nm) used applies a lower energy for detection of NSs than the electron beam of the SEM. These facts lead to a much decreased formation of artefacts during NSs detection in wood. This quick and easy method can be used for fast analysis of new nanoparticle-based wood preservative systems, which leads to a better understanding of impregnation processes, providing an essential step in finding fundamentally new wood preservatives.