Effect of oxidation debris on spectroscopic and macroscopic properties of graphene oxide

Oxidation debris (OD) and graphene oxide (GO) before and after OD removal were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, mass spectroscopy, X-ray diffraction, transmission electron microscopy and potentiometric titration, respectively. OD removal decreased GO absorption intensity in UV/Vis spectra, caused changes in peak position and absorption intensity in FTIR spectra, and resulted in the decrease of ID/IG in Raman spectra. OD was amorphous and had higher content of acidic groups than purified GO. OD contributed 10-25% of overall surface charge density to unpurified GO in spite of small amount (ca. 1% mass). OD removal decreased significantly GO dispersibility in aqueous solution, but increased obviously the electrical conductivity of reduced graphene oxide (rGO) and the apparent density of compacted rGO. The removal of OD was necessary because of its striking effects on both GO spectroscopic and macroscopic properties. Batch desorption in NaOH solution was recommended for OD removal from as-prepared graphite oxide because of slow OD desorption kinetics.