Affiliation:
1. Physics Center of Minho and Porto Universities (CF-UM-UP), University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal
2. LaPMET–Laboratory of Physics for Materials and Emergent Technologies, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
Abstract
The extinction efficiency of noble metal nanoparticles (NPs), namely gold (Au) and silver (Ag), are dependent on their size and surrounding dielectric. Exploiting the Localized Surface Plasmon Resonance (LSPR) phenomenon, the composition and structure of the NPs might be tailored to achieve a configuration that optimizes their response (sensitivity) to environmental changes. This can be done by preparing a bimetallic system, benefiting from the chemical stability of Au NPs and the higher scattering efficiency of Ag NPs. To enhance the LSPR sensing robustness, incorporating solid supports in the form of nanocomposite thin films is a suitable alternative. In this context, the NPs composed of gold (Au), silver (Ag), and their mixture in bimetallic Au-Ag NPs, were grown in a titanium dioxide (TiO2) matrix using reactive DC magnetron sputtering. Thermal treatment at different temperatures (up to 700 °C) tuned the LSPR response of the films and, consequently, their sensitivity. Notably, the bimetallic film with Au/Ag atomic ratio 1 exhibited the highest refractive index sensitivity (RIS), with a value of 181 nm/RIU, almost one order of magnitude higher than monometallic Au-TiO2. The nanostructural analysis revealed a wide NP size distribution of bimetallic NPs with an average size of 31 nm, covering about 20% of the overall surface area. These findings underscore the significant potential of bimetallic film systems, namely AuAg-TiO2, in LSPR sensing enhancement.
Funder
Portuguese Foundation for Science and Technology
CO2Plasmon
FCT
Subject
Electrical and Electronic Engineering,Biochemistry,Instrumentation,Atomic and Molecular Physics, and Optics,Analytical Chemistry
Reference73 articles.
1. Nanoplasmonics: The physics behind the applications;Stockman;Phys. Today,2011
2. Divya, J., Selvendran, S., Raja, A.S., and Sivasubramanian, A. (2022). Surface plasmon based plasmonic sensors: A review on their past, present and future. Biosens. Bioelectron. X, 11.
3. Roadmap on plasmonics;Stockman;J. Opt.,2018
4. Localized Surface Plasmon Resonance Sensors;Mayer;Chem. Rev.,2011
5. Optical properties of metallic nanoparticles: Manipulating light, heat and forces at the nanoscale;Coronado;Nanoscale,2011