| Abstract: | Introduction: Plasmonic nanomaterials have rapidly emerged in multiple applications such as biomedicine, detection, catalysis, owing to their unique optical properties. Metal nanoparticles (NPs), especially gold with possible tunability of surface plasmon resonance over ultraviolet visible-near infrared band through shape, size, and structure adjustment offer remarkable characteristics as a photothermal agent. Thanks to the longitudinal surface plasmon resonance and the high absorption in near-infrared of the non-spherical nanoparticles, they possess photothermal performance than spherical NPs. For instance, gold nanorods (AuNRs) have been extensively investigated and have turned out a better photothermal agent than gold nanoparticles. In the same trends, gold nanobipyramids (AuNBPs) with sharp tips exhibited an outstanding photothermal conversion. In this work, we synthesized two photothermal agents with specific characteristics or features and examined their photothermal performances under 808 nm laser illumination.
Aims: This study aims to compare the photothermal efficiency of AuNRs and AuNBPs two non-spherical gold nanoparticles under near infra-red (NIR) 808 nm laser irradiation.
Materials and Methods: AuNRs and AuNBPs with transversal and longitudinal SPR of 520 and 808 nm respectively were obtained by the seed-mediated method. They were characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Photothermal performances of synthesized Au nanoparticles were carried out using NIR 808 laser illumination with 1W/cm2 like light intensity. We further investigated their antibacterial PPT on Escherichia coli (E. coli) and the density functional theory simulation.
Results: The synthesized nanoparticles through TEM images confirmed their rod and bipyramid shapes with a size of (107.59 ±3.98 / 31.31±1.63 nm) and (82.24 ±3.34 /24.90±1.75 nm) respectively. AuNBPs with (111) plane revealed a stronger photothermal effect than that of AuNRs with (200) plane under NIR laser irradiation. Density function theory (DFT) simulations indicated that water was easily desorbed from Au (111) surface for photothermal heating. For photothermal therapy against E. coli, AuNBPs also exhibited higher efficiency compared to that of AuNRs under NIR laser irradiation. Overall, our results demonstrated that AuNBPs with (111) planes are good candidates in terms of photothermal properties.
Conclusion: AuNBPs are more efficient photothermal agents (PTAs) compared to AuNRs and should be preferred for the design of gold-based photothermal agents for diverse applications. |
