Multimodal characterization of horsetail-derived carbon quantum dots: from nanostructure to nonlinear optical behavior

• Carbon quantum dots (CQDs) were successfully synthesized from Horsetail plant extract using a hydrothermal method. • Iron and cobalt were loaded onto the CQDs to explore their adsorption potential. • Comprehensive characterization techniques such as TEM, DLS, FT-IR, UV–Vis, PL spectroscopy, and Z-scan aperture were employed to analyze the CQDs’ physical, chemical, and structural properties. • TEM imaging revealed that the synthesized CQDs have an average size of 5.27 nm. • Z-scan experiments demonstrated a high nonlinear optical response of CQDs, indicated by reversed saturation absorption and dense diffraction rings patterns. Carbon quantum dots (CQDs) have attracted significant attention due to their potential in various industrial applications. Extensive research has been dedicated to uncovering the complex and enigmatic nature of CQDs from a physicochemical perspective. In the present study, CQDs were synthesized from horsetail plant extract using the hydrothermal method. Iron and cobalt were then loaded onto the CQDs to investigate their adsorption potential. Transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), photoluminescence (PL) spectroscopy, and Z-scan aperture were used to investigate the physical, chemical, and structural properties of the synthesized CQDs. The results revealed changes in the FT-IR spectra of CQDs compared to the metals loaded CQDs. TEM imaging showed that the CQDs had an average size of 5.27 nm. Furthermore, reversed saturation absorption (RSA) and dense diffraction rings patterns were observed in Z-scan experiments, indicating a high nonlinear optical response of CQDs.