Analysis of graphene-coated and uncoated gold nanostars for enhanced photothermal therapy: experimental and...

Objective: This study aims to evaluate and compare the photothermal responses of gold nanostars (AuNSs) and graphene-coated gold nanostars (G-AuNSs), which are considered promising photothermal agents due to their high plasmonic absorption and efficient light-to-heat conversion.Method: A combined experimental and numerical approach was employed to assess the photothermal behavior of AuNSs and G-AuNSs under tissue-mimicking phantom conditions. A three-dimensional finite element method (FEM)-based optical-thermal model was developed and validated using a multilayer liver-mimicking phantom. Star-shaped AuNSs and G-AuNSs with sizes of approximately 80-250 nm were synthesized via seed-mediated growth and subsequent graphite oxide coating. Each nanoparticle system was examined at its respective plasmon-matched excitation wavelengths: 810 nm for AuNSs and 1064 nm for G-AuNSs.Results: The FEM predictions were found to be in good agreement with infrared thermography measurements, with maximum temperature differences below 2 °C under the tested conditions. Under the irradiation conditions (1 W·cm-2 for 700 seconds), AuNSs achieved peak temperatures of approximately 44-45 °C, while G-AuNSs produced temperature elevations of approximately 57-58 °C. Cumulative thermal dose (CEM43) analysis indicated significantly higher thermal dose accumulation for G-AuNSs compared to AuNSs. Additionally, cooling-curve analysis revealed higher photothermal conversion efficiencies for G-AuNSs (67.8% experimentally and 71.1% from phantom-matched FEM estimation) in contrast to AuNSs (51.2% experimentally and 55.4% from FEM estimation).Conclusion: The findings of this study demonstrate that G-AuNSs exhibit superior photothermal heating performance compared to AuNSs under the investigated NIR-I and NIR-II irradiation conditions. This highlights the potential of graphene-coated gold nanostars for improved photothermal applications in the NIR-II range, while also acknowledging the limitations associated with phantom-based validation and wavelength-dependent excitation effects.