Background: Graphene Oxide (GO) is a type of two-dimension carbon nanomaterial with promising environmental application due to its good solubility in water

high absorbability and catalytic activity. Humic Acid (HA) is the main component of Natural Organic Matter (NOM) in water

which could be adsorbed on the surface of GO nanosheets via π-π interaction and then affect the physicochemical properties of GO in aqueous system. Purpose: Investigating the interaction between GO and HA will provide some insights for environmental application of GO. Methods: We employed Synchrotron Radiation Circular Dichroism spectroscopy (SRCD)

Ultraviolet-Visible spectroscopy (UV-Vis) and Fourier Transform Infrared spectroscopy (FTIR) to explore the interaction between GO and HA under different mass ratio of HA to GO

environmental pH and temperature. Results & Conclusion: UV-Vis spectroscopy of GO-HA showed that the intensity of the absorption peak at 228 nm gradually increased when the mass ratio of HA to GO increased to 4:1 from 1:4 and the FTIR C-O stretching vibration shifted and decreased

indicating the strong π-π interaction and hydrogen bonding between GO and HA. GO showed a broad peak at about 240 nm in SRCD spectra which origin from its surface O-containing functional groups

folding or curl of the nanosheets. SRCD indicated the interaction between GO and HA could change the dispersion behavior of GO and then affect CD activity of GO-HA

depending on the mass ratio of HA to GO

environmental pH and temperature. GO-HA showed higher CD activity with the increased pH and decreased temperature (4 °C) due to the increase of folding state. Abstract