Disentangling Light- and Temperature-Induced Thermal Effects in Colloidal Au Nanoparticles

Area of Science:

• Nanotechnology
• Materials Science
• Physical Chemistry

Background:

• Gold/silica core-shell nanoparticles exhibit unique optical properties.
• Temperature influences nanoparticle behavior and optical responses.
• Understanding these effects is crucial for applications in optics and sensing.

Purpose of the Study:

• To investigate the temperature-dependent absorption spectra of Au/SiO2 core-shell nanoparticles.
• To analyze the influence of temperature on localized surface plasmon resonance (LSPR) and interband transitions.
• To compare experimental findings with theoretical models and photoinduced transient absorption (TA) spectra.

Main Methods:

• Measurement of absorption spectra of Au/SiO2 NPs in water from room temperature to 80 °C.
• Experimental determination of temperature-dependent dielectric constants (real and imaginary parts) of gold nanoparticles and the surrounding medium.
• Theoretical calculations of absorption spectra based on measured dielectric properties.
• Modeling of photoinduced response and comparison with ultrafast transient absorption (TA) spectra.

Main Results:

• A consistent decrease in absorption was observed across the spectral range (1.5–4.5 eV) as temperature increased.
• The decrease in absorption was more pronounced at the LSPR band.
• Theoretical calculations accurately reproduced the experimental temperature-dependent absorption spectra.
• Transient absorption (TA) spectra confirmed LSPR excitation as a reliable indicator of NP heating.

Conclusions:

• Temperature significantly impacts the optical absorption of Au/SiO2 NPs, particularly their LSPR.
• Theoretical modeling based on temperature-dependent dielectric properties provides accurate predictions.
• While LSPR monitoring is effective for assessing heating, the interband region's response is complex, influenced by both heating and charge carrier dynamics.