Multi wavelength measuring of the gold nanoparticles by the optical fiber interferometerAgrež, Vid (Avtor) Kramar, Julij (Avtor) Petkovšek, Rok (Avtor) optical fiber interferometerphotothermal detectiongold nanoparticlesAn optical fiber-based Mach–Zehnder interferometer was developed for photothermal detection of gold nanoparticles in aqueous suspensions. The excitation laser locally heats the suspension, inducing a refractive index change that is detected as a phase shift in the interferometer's measuring arm. By employing excitation wavelengths of 450 nm and 525 nm, the wavelength-dependent absorption was analyzed and compared to Mie theory predictions, enabling simultaneous determination of particle size and concentration. The absorption cross-section ratio, calculated from measurements at both wavelengths, depends only on particle size and provides the basis for size determination without prior knowledge of concentration. The system demonstrated high sensitivity, with detection limits as low as 8 × 10⁶ particles per milliliter for 100 nm gold nanoparticles. The optical fiber-based architecture offers simplicity, robustness, and potential for integration into portable sensing systems for nanoparticle characterization and biosensing applications.20262026-05-29 13:02:10Bibliografija182960sl