Analysis And Optimization Of Photothermal Properties Of Au Nanoshells And Nanospheroids

Due to the photothermal properties of nanoparticles,they are used in photothermal therapy.photothermal therapy has been widely explored as a minimally invasive cancer treatment.Near-infrared(700 nm-1100 nm)light is chosen for photothermal therapy,because of the high penetration and low light scattering of biological tissues in this wavelength range.Gold(Au)nanoparticles have antibacterial,antioxidant and anti-corrosive properties,making them of increasing interest in photothermal therapy.With their extraordinary optical properties,they are considered as an ideal material for cancer therapy.Au nanoparticles can effectively absorb nearinfrared light and convert it into heat.Many researches have been investigated theoretically and experimentally in these years to analyze the photothermal properties of nanoparticles.However,the investigations on the photothermal properties of nanoparticles present the following two problems:(1)Approximate models and theories are used to calculate the optical properties of nanoparticles.Many studies were found,using Quasi-static approximation theory or Rayleigh approximation to solve the particle absorption cross section.It contains more approximate conditions and is more suitable for smaller nanoparticles,but with the increase of nanoparticle size,it leads to large calculation errors.Therefore,it is necessary to use strict small particle light scattering theory.(2)At present,many studies discuss the influence of particle shape,concentration,incident light intensity and other factors on its photothermal properties,the optimal size parameters of the nanoparticles that correspond to the best photothermal properties are not given.To solve the above-mentioned problems,the effects of the light wavelength and the particle size on the photothermal properties of Au nanoshells and nanospheroids were analyzed by using the time-dependent heat transfer equation and the accurate light scattering theory(Mie theory and T-matrix).The intensity and position of the resonance peak can be adjusted by changing the particle size of the Au nanoshells and nanospheroids.The required particle surface and medium temperature variation also can be obtained.Then,the maximum particle surface and medium temperature change per unit incident light intensity at four typical wavelengths(800,808,820,and 1064 nm)in the near-infrared region and the corresponding optimal particle size were obtained to analyze the application of the photothermal properties of the particles.Finally,the particle size distribution with a particle surface and medium temperature change per unit incident light intensity greater than 90% maximum temperature change at the above wavelengths was given.The optimized Au particles can be used as ideal therapeutic agents in photothermal therapy.