Fig. 1

Spectral characterization of GO, Hep-rGO, PDA-rGO and Hep-PDA-rGO: A UV–visible absorption spectra, B Raman spectra, and C FT-IR spectra; D Thermal stability of GO and Hep₂₀-PDA_0.8-rGO was evaluated via TGA in the temperature range of 0–800 °C at 10 °C/min; E AFM images and the corresponding height measurements of GO (I), Hep₂₀-rGO (II), PDA_0.8-rGO (III) and Hep₂₀-PDA_0.8-rGO (IV). The subscript represents the weight multiples relative to rGO