目的　研究表面化学修饰对纳料粒子光学非线性的影响 .方法　采用简并四波混频 (DFWM)方法测量了表面用 2 ,2 ’ -联吡啶 (bpy)进行化学修饰的 Cd S纳米粒子 (记为Cd S/ bpy)有机深胶的三阶非线性光学响应 ,并考虑一个双光子吸收的修正因子 ,用最小二乘法对实验结果进行了拟合 .结果　求得每个 Cd S/ bpy粒子的三阶超极化率的实部γIR=-0 .42× 1 0 -2 7esu,虚部 γ1 I=2 .0 2× 1 0 -2 7esu.结论　较大的虚部表明双光子吸收导致的共振增强作用对 DFWM信号有重要贡献 .另外 ,还用表面效应解释了表面修饰 Cd S纳米粒子相对于裸的 Cd S纳料粒子 (水溶胶 )三阶非线性增强的原因 Aim To investigate the effect of surface chemical modification on the optical nonlinearity of nanoparticles.METHODS The degenerated four-wave mixing (DFWM) method was used to measure the optical nonlinearities of CdS nanoparticles modified by 2, 2’-dipyridyl (bpy) Which is denoted as Cd S / bpy), and taking into account the correction factor of two-photon absorption, the experimental results were fitted by the least-squares method. Results Each Cd S / bpy particle The real part of the third-order hyperpolarizability γIR = -0.42 × 10 -2 7esu, the imaginary part γ1 I = 2.02 × 10 -2 7esu.Conclusion The larger imaginary part indicates that the two-photon absorption results in Enhances the DFWM signal significantly.Furthermore, surface effect is used to explain the reason of the third-order non-linear enhancement of surface-modified CdS nanoparticles relative to bare CdS nanoparticles