We studied the limits of optical reflectance to detect plasmonic nanoparticles (NPs) embedded in air and supported by a glass substrate, in an internal reflection configuration. We used a recently derived multiple-scattering model for the coherent reflectance of a disordered monolayer of particles supported on a flat surface to calculate the sensitivity of optical reflectance variations to the presence of plasmonic NPs. We considered gold and silver NPs with radii up to 50 nm and studied the sensitivity as a function of the angle of incidence, wavelength, particle size, and polarization of light. Using our own measurements of noise, we estimated the minimum detectable surface-coverage by the particles. The highest sensitivity is found around the critical angle between the glass substrate and air, for transverse-magnetic polarization, and at wavelengths of light near the plasmon resonance of the particles. We provide estimates of the minimum number of particles per unit area detectable from reflectivity variations and set the basis for single particle detection.
We explore using measurements of the effective refractive index of a metallic nanofluid to estimate the size of the particles in it. We assume the nanofluid consists of spherical metallic nanoparticles suspended in a transparent base liquid and discuss a way of measuring the real and imaginary parts of the effective refractive index for concentrated nanofluids to about 1% in particles’ volume concentration. Specifically, we consider the case of copper nanoparticles suspended in water. We propose an unambiguous effective optical parameter as a candidate to evidence the particle size, potentially in real time. Limitations due to dependent scattering effects in concentrated nanofluids are briefly stated.
In this work we study the sensitivity and detection limits of optical reflectivity measurements to inspect the deposition of metallic nanoparticles on a at surface. We use a theoretical model for the coherent reflectance of a disordered monolayer of particles to calculate the reflectivity of an air-glass interface with silver and gold nanoparticles deposited randomly on it as a function of the angle of incidence and wavelength of light. Assuming reasonable noise scenarios, we estimate the minimum detectable surface coverage fractions by the nanoparticles.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.