Photothermal Determination of Absorption and Scattering Spectra of Silver Nanoparticles

Abstract

This work reports on photothermal lens spectra of silver nanoparticles of different dimensions in the spectral region of 370-730 nm performed using an arc-lamp-based photothermal spectrophotometer. We show that the photothermal and extinction cross-section spectra of the samples are similar for nanoparticles of reduced dimensions where scattering effects are small. The results differ substantially for nanoparticles of a diameter larger than 30 nm for which scattering becomes relevant. We demonstrate that the photothermal spectrum corresponds to the absorption component of the particle's extinction. Photothermal spectra show a clear picture of the plasmonic peaks of the nanoparticle even in the presence of high scattering. By subtracting the photothermal component from the total extinction, we extract the scattering cross-section spectra of the nanoparticles. The technique allows determination of the absorption and scattering components of the extinction providing a better understanding of the particle's optical properties. The results agree well with the Mie approximation, which is valid for a single spherical nanoparticle. We discuss and demonstrate the application of the method to characterize particles of arbitrary shape and dimensions.

Thermometric lateral flow immunoassay with colored latex beads as reporters for COVID-19 testing

“…( 4 ), we used the TLFIA reader to investigate how the temperature rises varied with the CLB concentrations of the droplets deposited on the strips. The PTD serves well for the purpose because it has been previously demonstrated that the photothermal spectra obtained for absorbing molecules or nanoparticles dispersed in scattering medium corresponds to the absorption component of the sample’s extinction 35 – 37 .…”

Experiments And Simulations of Thermometric Lateral Flow Immunoassay For Point-of-Care Testing

“…This PTD approach serves well for the purpose because it has been previously demonstrated that the photothermal spectra obtained for absorbing molecules or nanoparticles dispersed in scattering medium corresponds to the absorption component of the sample's extinction. [31][32][33] Our experiment started with a temperature measurement for a sample spot prepared with concentrated CLB solution (4% w/w) and excited by a 520-nm laser at a power of 10 mW. The power used in this measurement was kept low to avoid photodamage of the dye molecules embedded in the microspheres.…”

Machine-Free Polymerase Chain Reaction with Triangular Gold and Silver Nanoparticles

“…Among various geometries, triangular, rods, and bipyramidal nanostructures are well-known for their strong near-infrared (NIR) absorbance coefficients compared to spherical shape . Thus, tuning the geometry of NPs has a wide range of potential applications in biomedical research, biosensing, photothermal therapy, and photovoltaic devices . In this direction, gold nanorods are promising as an efficient source for photothermal therapies such as hyperthermia in cancer treatment, thermal contrasting in lateral flow assays, and nonviral gene carrier systems .…”

“…For silver nanoparticles, lower concentrations enhance the PCR efficiency making them more attractive for potential applications. Also, the localized heat at the surface of AgTNPs may be considerably higher compared to AuTNPs, due to silver exhibiting sharper and stronger surface plasmon band and its fine optical characteristics like larger absorption and scattering cross sections . These features can result in more efficient photothermal conversion at the nanoscale level resulting in enhancement of heat transfer even at low annealing temperatures.…”

“…5 Thus, tuning the geometry of NPs has a wide range of potential applications in biomedical research, biosensing, photothermal therapy, and photovoltaic devices. 6 In this direction, gold nanorods are promising as an efficient source for photothermal therapies such as hyperthermia in cancer treatment, 7 thermal contrasting in lateral flow assays, and nonviral gene carrier systems. 8 For example, nanorods, nanostars, and triangular gold nanoparticles (AuTNPs) are superior to spherical gold nanoparticles in cellular uptake, drug delivery, and photothermal therapy.…”