Peculiar nonlinear optical absorption and optical limiting behaviors of bismuth-based binary and ternary nanostructures

Abstract

A single-beam Z-Scan experiment was used to investigate the nonlinear optical absorption and optical limiting properties of pristine Bi2O3, binary rGO/Bi2O3, Bi2O3/WO3 and ternary rGO/Bi2O3/WO3 nanostructures. These nanostructures were synthesized using a facile hydrothermal method. The crystallite size, interplanar spacing, allotropes of carbon and functional groups were characterized using XRD, Raman and FTIR. The morphology of the synthesized compounds was confirmed by SEM and TEM analyses. EDS analysis confirmed the existence of elements such as C, O, Bi and W. A linear optical study illustrates that the pristine Bi2O3 exhibited absorption within the UV range of 200 nm and 400 nm, whereas the binary and ternary nanostructures displayed absorption in the UV–Visible range from 200 nm to 800 nm. The synthesized nanostructures shows exciting nonlinear absorption such as genuine 2PA (pristine Bi2O3), W-type SA to RSA (binary rGO/Bi2O3, Bi2O3/WO3) and sequential 2PA (ternary rGO/Bi2O3/WO3). Bismuth-based nanostructures exhibit the lowest optical limiting (OL) threshold and a greater two-photon absorption coefficient. The extended conjugation for charge transfer and the presence of high defect-induced states in rGO, along with the strong UV–Visible absorption of Bi2O3 and WO3 which leads to a unique nonlinear optical response. This response holds promise for potential applications in energy stabilizers and laser safety devices operating at 532 nm and 9 ns laser domain.