Mirzazadeh Saeed, Sharifi Soheil
Department of Physics, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
J Fluoresc. 2025 Apr 22. doi: 10.1007/s10895-025-04324-9.
The nonlinear absorption coefficient (β) and nonlinear refractive index (n) of citrate-capped gold nanoparticles (CC-AuNPs) encapsulated and stabilized within a composition of water, n-heptane, and anionic AOT surfactant were studied by z-scan technique which includes a laser with a wavelength of 532nm and a power of 80mW. Encapsulation of AuNPs (Cap-CC-AuNPs) consists of aqueous droplets uniformly dispersed in the continuous phase of n-heptane, which enables the effective Cap-CC-AuNPs that exhibited significant nonlinear absorption despite their lower concentration, attributed to the reduced dielectric constant of the bulk medium. The aggregation of CC-AuNPs in aqueous solutions, which is the result of the increase of ions, has increased the value of β and elastic scattering. While, in the water-ethanol binary mixture, even with low aggregation along with the reduction of light scattering, the β value was enhanced with a reduction of the dielectric constant of the solution. The source of increase in nonlinear optical properties and elastic scattering of gold nanoparticles in solutions is increase in polarizability. Quantum perturbation theory was employed to calculate the dipole moment of AuNPs, it is distinguished that the ground state dipole moment of AuNPs increase with encapsulation. Cap-CC-AuNPs can serve as a photosensitizer in photodynamic therapy or other optical devices.
通过z扫描技术研究了包裹并稳定在水、正庚烷和阴离子AOT表面活性剂组成体系中的柠檬酸盐包覆金纳米颗粒（CC-AuNPs）的非线性吸收系数（β）和非线性折射率（n），该技术使用波长为532nm、功率为80mW的激光。金纳米颗粒的包裹体（Cap-CC-AuNPs）由均匀分散在正庚烷连续相中的水滴组成，这使得有效的Cap-CC-AuNPs即使在浓度较低时也表现出显著的非线性吸收，这归因于本体介质介电常数的降低。CC-AuNPs在水溶液中的聚集是离子增加的结果，这增加了β值和弹性散射。而在水-乙醇二元混合物中，即使聚集程度较低且光散射减少，β值也会随着溶液介电常数的降低而增大。溶液中金纳米颗粒非线性光学性质和弹性散射增加的原因是极化率的增加。采用量子微扰理论计算金纳米颗粒的偶极矩，结果表明金纳米颗粒的基态偶极矩随着包裹而增加。Cap-CC-AuNPs可作为光动力疗法或其他光学器件中的光敏剂。
