Tuning the linear and nonlinear optical absorption properties of ZnS/hydrochar nanocomposites by concentration of nanoparticles

Abstract In this article, the effects of nanoparticles aggregates and concentration on linear and nonlinear optical absorption properties of ZnS and ZnS/carbon-based materials in polymethyl methacrylate (PMMA) matrix have been investigated. Carbon-based materials were synthesized via the hydrothermal carbonization method. Hazelnut shell was preferred as a feedstock of carbon material due to its high production capacity in Turkey. Thin films consisting of 10, 20, and 30 wt % nanoparticles were obtained to discover the effect of weight concentration on optical properties. The linear and nonlinear absorption properties were characterized by UV–Vis spectroscopy technique and open aperture Z-scan measurements with 4 ns pulses at 532 nm. A theoretical model containing one photon, two photon and free carrier absorption and their saturations were used for the fitting of the experimental data. The band gap decreased with the increasing of the weight concentration of nanoparticles in PMMA. Z-scan experiment results showed that the highest effective nonlinear absorption coefficient was obtained for the thin films with 30 wt% nanoparticle concentration which had also the smallest bandgap energy. The effect of nanoparticles aggregates on the band gap energy and nonlinear absorption was also observed. The transmission electron microscopy (TEM) results indicated that the addition of carbon caused the aggregation.