On the quantitative optical properties of Au nanoparticles embedded in biological tissue phantoms

• Published in: Optical materials 2021-04, Vol.114, p.110924, Article 110924
• Main Authors: Araújo, J.C.R., Monte, A.F.G., Lora-Serrano, R., Iwamoto, W., Antunes, A., Brener, O., Foschini, M.
• Format: Article
• Language: English
• Subjects: Au nanoparticles; Chitosan phantoms; Mie and Rayleigh scatterings; Optical absorption; Optical phantoms; Optical scattering
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2021.110924

We systematically investigated and quantified how gold (Au) metal nanoparticles (NPs) optical spectra change upon introduction into the biological tissue phantoms environment, in which the AuNPs can agglomerate. Quantitative knowledge of how the AuNPs spectra and plasmon resonance wavelength change inside a phantom environment can provide many in-vitro and in-vivo plasmonic NPs-mediated applications. Because the plasmonic properties of metal NPs are dependent on their size, morphology, concentration, and local environment, tuning the incident photon wavelength may increase the AuNPs plasmonic properties. Plasmonic photothermal therapy and photonic gene circuits are among the many applications. Quantitatively analyzing optical absorption and scattering data, we may observe changes in the resonance peak positions and breadths, related to the distribution of the spherical AuNPs within the chitosan phantoms as a function of the particle size and concentration. The scattered irradiance with the wavelength for embedded AuNPs was registered for the optical scattering mechanisms, decreasing as λ−4 for Rayleigh scattering, and much more slowly for Mie scattering, λ−b, with b in the range of 1–3. •Quantification of AuNP absorption and scattering coefficients in chitosan phantom environment.•The effect of AuNP agglomeration with strong shift of plasmon peak position inside the phantoms was revealed.•Simulated scattered irradiance with the wavelength predicted Rayleigh scattering for embedded AuNPs smaller than 20 nm.•Simulations of Mie scattering for AuNPs revealed Mie coefficient ranging from 1 to 3 according to the nanoparticle size.