表面化学修饰对CdS纳米粒子三阶光学非线性的影响

Influence of Surface Chemical Modification on the Third-order Optical Nonlinearity of CdS Nanoparticles

用反胶束法制备了表面修饰 AOT-SO- 3(磺基琥珀酸双 -2 -乙基己酯钠盐的阴离子 )的 Cd S纳米粒子与表面修饰 Py(吡啶 )的 Cd S纳米粒子。采用背相简并四波混频 (DFWM)的方法研究了它们的三阶光学非线性。结果表明当 Cd S纳米粒子表面上的 AOT-SO- 3被 Py取代后 ,其三阶非线性极化率增加 ,这归于表面修饰 Py的Cd S纳米粒子具有长寿命的表面受陷电子 -空穴分离态 ,从而提高了对激子吸收的漂白效率 ,增加了三阶光学非线性。

CdS nanoparticles capped by AOT SO 3 -(anion of surfactant bis (2 ethylhexyl) sulfosuccinate, disodium salt) or pyridine were prepared using reverse micelle method. Their third order optical nonlinearities were studied via a Degenerate Four Wave Mixing (DFWM) technique. Results show that the third order nonlinearity of CdS nanoparticles increases when AOT SO 3 - on the particle surface is exchanged by pyridine. This is attributed to that the pyridine modified CdS nanoparticles possess a surface trapped electron hole separation state with long lifetime which is helpful for bleaching of exciton absorption and therefore enhancing the third order optical nonlinearity of CdS nanoparticles.