聚乙烯基咔唑共价接枝还原氧化石墨烯的制备及其宽带光限幅性能

Preparation and Broadband Optical Limiting Performance of Reduced Graphene Oxide Covalently Functionalized with Poly(N-vinylcarbazole)

用表面带负电荷的还原氧化石墨烯(RGO)作为阴离子聚合引发剂,在RGO表面使N-乙烯基咔唑(NVK)原位聚合,生成可溶性聚乙烯基咔唑(PVK)共价功能化的RGO非线性光学材料(RGO-PVK)。采用红外光谱、X光电子能谱和紫外-可见吸收光谱等对RGO-PVK进行了表征。将RGO-PVK嵌埋在非光学活性的聚甲基丙烯酸甲酯(PMMA)中制备了具有良好光学性能的RGO-PVK/PMMA薄膜,并利用开孔Z-扫描技术研究了RGO、RGO-PVK、退火处理的RGOPVK薄膜在532、1 064 nm激光辐照下的非线性光学(NLO)和光限幅(OL)性能。结果表明:与RGO相比,PVK在RGO表面的共价键合显著增强了材料的宽带NLO性能和OL效应。与没有经过退火处理的RGO-PVK/PMMA薄膜相比,退火后的RGO-PVK/PMMA薄膜展现出更加优良的NLO性能。在532、1 064 nm的激光激发下,退火后的RGO-PVK/PMMA薄膜的非线性吸收系数(β_(eff))分别为306.17、350.32 cm/GW,相应的光限幅阈值分别为0.37、0.31 GW/cm^(2)。

Graphene shows ultrafast carrier relaxation dynamics and ultra-broadband resonate nonlinear optical(NLO)response due to its extended π-conjugate system and the linear dispersion relation holding for its electronic band structure. In comparison with graphene, functionalized graphene derivatives would be expected to show more excellent NLO and optical limiting(OL) performance. By using as-synthesized graphene carbanions as initiator in the anionic polymerization, poly(Nvinylcarbazole)-covalently functionalized reduced graphene oxide(RGO) derivative(RGO-PVK) was in situ synthesized.RGO-PVK was characterized by infrared spectroscopy, X-ray electron spectroscopy and UV-Vis absorption spectroscopy.This soluble material was embedded into an optically nonactive transparent polymethylmethlacrylate(PMMA) matrix to produce the PMMA-based RGO-PVK film. The NLO and OL properties of RGO, RGO-PVK, and annealed RGO-PVK films under 532 nm and 1 064 nm laser irradiation were also investigated using the open-aperture Z-scan technique.The results show that in contrast to RGO, the covalent grafting of PVK chains to the RGO surface significantly improve NLO and broadband OL performance of the resultant material. Upon excitation with laser light, the achieved nonlinear coefficients and OL thresholds of the annealed RGO-PVK/PMMA film are 306.17 cm/GW and 0.37 GW/cm^(2) at 532 nm, and 350.32 cm/GW and 0.31 GW/cm^(2) at 1 064 nm, respectively. These findings would make it suitable for protecting the human eyes, optical sensors and optoelectronic devices from the laser beam in the visible and near-infrared spectral region.