resumo
In this work, a versatile method is proposed to increase the sensitivity of optical sensors based on the localized surface plasmon resonance (LSPR) phenomenon. It combines a physical deposition method with the oblique angle deposition technique, allowing the preparation of plasmonic thin films with tailored porosity. Thin films of Au-TiO2 were deposited by reactive magnetron sputtering in a 3D nanostructure (zigzag growth), at different incidence angles (0 degrees <= alpha <= 80 degrees), followed by in-air thermal annealing at 400 degrees C to induce the growth of the Au nanoparticles. The roughness and surface porosity suffered a gradual increment by increasing the incidence angle. The resulting porous zigzag nanostructures that were obtained also decreased the principal refractive indexes (RIs) of the matrix and favoured the diffusion of Au through grain boundaries, originating broader nanoparticle size distributions. The transmittance minimum of the LSPR band appeared at around 600 nm, leading to a red-shift to about 626 nm for the highest incidence angle alpha = 80 degrees, due to the presence of larger (scattering) nanoparticles. It is demonstrated that zigzag nanostructures can enhance adsorption sites for LSPR sensing by tailoring the porosity of the thin films Atmosphere controlled transmittance-LSPR measurements showed that the RI sensitivity of the films is improved for higher incidence angles.
palavras-chave
SURFACE-PLASMON RESONANCE; NANOSCALE OPTICAL BIOSENSOR; RANGE DISTANCE DEPENDENCE; METAL NANOPARTICLES; GOLD NANOPARTICLES; REFRACTIVE-INDEX; TIO2; SPECTROSCOPY; SHAPE; LSPR
categoria
Science & Technology - Other Topics; Materials Science; Physics
autores
Rodrigues, MS; Borges, J; Proenca, M; Pedrosa, P; Martin, N; Romanyuk, K; Kholkin, AL; Vaz, F
nossos autores
Andrei Kholkin
Investigador Principal
Konstantin Nikolaevich Romanyuk
Investigador Júnioragradecimentos
This research was sponsored by the Portuguese Foundation for Science and Technology (FCT) in the framework of Strategic Funding UID/FIS/04650/2013; project POCI-01-0145-FEDER-016902, with FCT reference PTDC/FIS-NAN/1154/2014; and project POCI-01-0145-FEDER-6032299, with FCT reference PTDC/FIS-MAC/32299/2017. This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, FCT Ref. UID/CTM/50011/2019, financed by national funds through the FCT/MCTES. Manuela Proenca acknowledges her PhD grant from FCT, with reference SFRH/BD/137076/2018. Joel Borges acknowledges FCT for his Post-Doc grant SFRH/BPD/117010/2016. Marco S Rodrigues acknowledges FCT for his PhD grant with reference SFRH/BD/118684/2016. Konstantin Romanyuk wish to thank the Portuguese FCT for the financial support (grant SFRH/BPD/88362/2012).