The effect of nitrogen-doped carbon nano-onions on the third order nonlinear optical responses of CoWO4-MnO2 nanocomposites

Abstract

CoWO4, CoWO4-MnO2, and CoWO4-MnO2-NCNO nanostructures were prepared via precipitation method followed by calcination at 450 °C. The nitrogen-doped carbon nano-onions (NCNOs) were synthesized by annealing the ultra-dispersed aminated-nanodiamond solution under He gas at 1150 °C followed by calcination at 400 °C. The morphological, structural, and optoelectronic responses of the samples were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Z-scan methods. The order of the nonlinear absorption (NLA) and nonlinear refraction (NLR) of samples are 10−3 (cm/W) and 10−8 (cm2/W), respectively. In different incident intensity of laser, all synthesized samples showed positive and negative sign of NLA and NLR indices, respectively. The NLA coefficient originates from two photon absorption effect and NLR indices indicate the self-defocusing effect. The lowest nonlinear optical response belonged to CoWO4 nanoparticles. CoWO4-MnO2-NCNO nanocomposite showed the higher nonlinear optical responses than CoWO4 and CoWO4-MnO2 nanocomposites. The large ratio of the surface area of NCNO and oxygen reduction activity of NCNO due to high incident intensity are the main reasons for increasing nonlinearity. The nonlinearity results are promising candidate for using in optical and photonic devices.