Here we report a drastic enhancement of nonlinear absorption behaviour and exceptional optical limiting action of two core-shell systems (Au@graphite and Ag@graphite) prepared by adopting a fairly easy way in which we did not use any graphitic substrate. We carried out pulsed laser ablation of Au and Ag targets in toluene, monosubstituted benzene from which graphite layers of nanometer thickness has emerged as a result of photochemical reactions. The prepared samples were characterized and analyzed by UV/Vis spectroscopy, Raman spectroscopy, and TEM. Theoretical simulations of the core-shell nanostructures were done by the finite-difference time-domain method underlined the quenching of SPR in the case of both Au and Ag NPs by the graphitic layers evolved from toluene. Au and/or Ag@graphite core-shell structure exhibited a huge improvement in the nonlinear absorption behaviour and the optical limiting efficiency of these systems is found to be better than that of many benchmark optical limiters. The enhancement in nonlinear absorption property and the limiting actions of these systems were attributed to the enhanced excited-state absorption as well as free-carrier absorption arose as a result of the modification in the electronic structure of graphite on core-shell formation. Moreover, the metallic NPs also enhances nonlinear absorption through free-carrier absorption free-carrier absorption. So we believe these results are quite useful for guiding the characterization, monitoring the synthesis of similar nanostructures and for, the development of nanohybrids with desired properties for nonlinear optical, optoelectronic and photocatalytic applications.

在这里，我们报告了通过采用一种相当简单的方法制备的两种核 - 壳系统（Au@graphite 和 Ag@graphite）的非线性吸收行为和特殊光学限制作用的显着增强，其中我们不使用任何石墨基材。我们在甲苯中对 Au 和 Ag 目标进行脉冲激光烧蚀，甲苯是单取代苯，由于光化学反应，从甲苯中出现了纳米厚度的石墨层。通过紫外/可见光谱、拉曼光谱和透射电镜对制备的样品进行表征和分析。核壳纳米结构的理论模拟是通过有限差分时域方法进行的，强调了在 Au 和 Ag NPs 的情况下，由甲苯演变而来的石墨层对 SPR 的猝灭。Au 和/或 Ag@graphite 核壳结构在非线性吸收行为方面表现出巨大的改进，并且发现这些系统的光学限制效率优于许多基准光学限制器的光学限制效率。非线性吸收特性的增强和这些系统的限制作用归因于增强的激发态吸收和自由载流子吸收，这是由于核壳形成石墨电子结构的改变而引起的。此外，金属纳米粒子还通过自由载流子吸收自由载流子吸收增强非线性吸收。因此，我们相信这些结果对于指导表征、监测类似纳米结构的合成以及开发具有所需非线性光学特性的纳米混合物非常有用，