Wavelength-dependence of the photothermal efficiency of gold nanoparticles in solution by Z-scan photothermal lens spectroscopy

Using continuous-wave (cw) single-beam Z-scan technique, the absorption and scattering efficiencies of spherical gold nanoparticles (NPs) of varying diameter are determined experimentally through the thermal lens (TL) effect for three different wavelengths in the blue, the green and the red. The main characteristics of the measurement method are detailed, extending the usual experimental procedure for weak absorption with Gaussian beams to higher absorption with top-hat beams. To confirm the validity of our approach, the experimental TL data were compared to the theoretical values from Mie theory and found to be in good agreement within the experimental errors. As expected, the photothermal efficiency of spherical gold NPs increases with lower diameters and to-wards shorter wavelengths.

Automated summary

Using the continuous-wave single-beam Z-scan technique, the absorption and scattering efficiencies of spherical gold nanoparticles of varying diameter were experimentally determined for three different wavelengths. The experimental procedure was modified to accommodate higher absorption rates by using top-hat beams instead of Gaussian beams. The obtained thermal lens data were in good agreement with the theoretical values from Mie theory, confirming the validity of the approach. The results showed an increase in photothermal efficiency with smaller particle diameters and shorter wavelengths.