Localized surface plasmon sensing based investigation of nanoscale metal oxidation kinetics

Abstract

The localized surface plasmon resonance (LSPR) of nanoparticles can be a powerful and sensitive probe of chemical changes in nanoscale volumes. Here we have used the LSPR of silver (Ag) to study the oxidation kinetics of nanoscopic volumes of cobalt (Co) metal. Bimetal nanoparticles of the immiscible Co-Ag system prepared by pulsed laser dewetting were aged in ambient air and the resulting changes to the LSPR signal and bandwidth were used to probe the oxidation kinetics. Co was found to preferentially oxidize first. This resulted in a significant enhancement by a factor of 8 or more in the lifetime of stable Ag plasmons over that of pure Ag. Theoretical modeling based on optical mean field approximation was able to predict the oxidation lifetimes and could help design stable Ag-based plasmonic nanoparticles for sensing applications.

Symbiosis in Plasmonic Nanoparticles

“…Kalyanaraman and co-workers extensively studied the Ag-Co bimetallic system synthesized by PLiD [11,12,29,[32][33][34][35]. Two separate studies were conducted on these bimetallic nanoparticles, one in which the bimetal composition was fixed while the nanoparticle size was varied.…”

“…Sachan et al stabilized the Ag nanoparticles by synthesizing bimetals of Ag and Co having segregated regions within a single nanoparticle using PLiD. The oxidation behavior was studied using optical spectroscopy and core-loss EELS mapping and showed prolong optical stability of Ag nanoparticles [12,29,34]. This ultra-stability was due to the galvanic coupling between Co and Ag at the nanoscale where Co was acting as a sacrificial anode, thus protecting Ag surface by providing electrons as shown in Figure 4(a).…”

“…This ultra-stability was due to the galvanic coupling between Co and Ag at the nanoscale where Co was acting as a sacrificial anode, thus protecting Ag surface by providing electrons as shown in Figure 4(a). The study was further extended by Malasi et al to understand the role of Co composition in these bimetals and how the Co-Ag nanoparticle life could be extended [34]. On studying the extended optical bandwidth decay of these nanoparticles, two observations were made.…”

“…To answer this, a theoretical model is used to quantify the oxidation of Co in the bimetallic nanoparticle system, details of which are available in Ref. [34]. Co-Ag bimetals showed almost 12 times better shelf life than pure Ag nanoparticles for 50% degradation in the optical bandwidth and depending on Co amount, the Ag could be oxide free for almost a year.…”

Surface sensitivity of optical and magneto-optical and ellipsometric properties in magnetoplasmonic nanodisks

“…Bio-chemical sensing devices have been recently improved by the realization of Surface Plasmon Resonance (SPR) based sensors. [1][2][3][4][5][6][7][8] In this technique, the high sensitivity of plasmonic resonances to dielectric environment provides the sensing principle. Moreover, a significant improvement in signal-to-noise ratio, sensitivity, and limit of detection has been demonstrated in Magneto-Optical Surface Plasmon Resonance (MO-SPR) based sensors.…”