Synthesis of heteroatom Doped-Carbon dot graphene oxide nanocomposites and investigation of nonlinear optical properties

A series of carbon dot graphene oxide (CDGO) nanocomposites and heteroatom doped-carbon dot graphene oxide (HD-CDGO) nanocomposites were prepared by one-step electrochemical exfoliation methods, where heteroatom represents P, N and S atoms. TEM, FT-IR and XPS were performed to confirm the structure of HD-CDGO. The Z-scan tests were used to investigate the nonlinear optical (NLO) properties of HD-CDGO, and the estimation of the band gap was performed using UV-vis and Tauc plots. The results demonstrate that the energy gaps of the prepared HD-CDGO were reduced, and the NLO properties were improved compared with those of CDGO. The nonlinear absorption coefficient (beta(eff)) of S-CDGO is 9.3 times higher than that of CDGO, and the imaginary part of the third-order nonlinear susceptibility (Im chi((3))) increases from 23 x 10(-12) esu to 213 x 10(-12) esu. Furthermore, different sulfur element concentration doped CDGO (Sx-CDGO, x = 0.05, 0.10, 0.20, 0.40, S-0.10-CDGO equals S-CDGO) were prepared, and the energy gap of Sx-CDGO decreases from 4.5 eV to 2.5 eV as the surface sulfur atomic concentration of Sx-CDGO increases from 0.6 % to 1.8 %, the beta(eff) value of Sx-CDGO increases from 15 x 10(-10) to 65 x 10(-10) m/W. Moreover, HD-CDGO/polymethyl methacrylate (HD-CDGO/PMMA) composites were prepared for practical applications. S-CDGO/PMMA composites exhibit the best NLO property, with the initial threshold value and limiting threshold of 0.05 and 0.40 J cm(-2), respectively, and the minimum transmittance of 21 %. Our work provides a promising design strategy to synthesize high-performance optical limiting (OL) materials.