Green Preparation And Structural Control Of Graphene Oxide

Graphene oxide（GO）is an important graphene derivative that has been widely studied and applied due to its excellent properties.Usually,GO is obtained by chemical oxidation method,which uses strong oxidants to intercalate with graphite under strong acid conditions and exfoliate.However,the oxidation system used in the conventional method has environmental risks and safety hazards,which limit the green and scale up preparation of GO.In this thesis,we propose a new method for GO preparation using the green and safe potassium periodate（KIO₄）as the oxidant,and investigate the reaction mechanism to clarify the differences between this method and the conventional method in GO structure regulation.The main research contents and progress of the paper are as follows.1.GO（GO-I）was prepared by the KIO₄/H₂SO₄ oxidation system with KIO₄ as the oxidant,and two different sizes of GO-I were obtained by using natural scaled graphite of two sizes,325 mesh and 6000 mesh,as raw materials,and their morphological features were characterized by SEM,TEM,AFM,and optical microscopy,and their structural features were characterized by XRD,Raman,FT-IR,XPS,and devices to characterize their structural features,and compare their structures with those of GO（GO-Mn）prepared by the conventional KMnO₄/H₂SO₄ oxidation system using KMnO4 as the oxidant.The results show that GO-I has more abundant carbonyl and carboxyl functional groups（C=O,O=C-O）and lower content of epoxy functional groups（C-O）.2.The mechanism of the reaction process was investigated by monitoring the preparation process of GO-I and characterizing and analyzing the oxidation products at different reaction times.The structural change characteristics and reduction products of GO-I were characterized by XRD,FT-IR,XPS,UV-vis,and the results showed that the oxidant IO₄^-was reduced to IO₃^-and I^-.And the morphological characteristics of GO at different reaction stages were observed by optical microscopy and scanning electron microscopy.Unlike the oxidation mechanism of the conventional KMnO₄/H₂SO₄oxidation system in which the oxidant is oxidized from the edge to the middle of the graphite sheet,the oxidant in the KIO₄/H₂SO₄ oxidation system starts oxidation by randomly finding sites on the graphite sheet,which is a completely different oxidation mechanism from the conventional method.3.Based on the special oxidation mechanism of the KIO₄/H₂SO₄ oxidation system,a simple and rapid preparation of GOQDs was designed.The size of GOQDs can be regulated by controlling the reaction time,reaction temperature and the ratio of graphite and oxidant.The longer the reaction time,the higher the reaction temperature and the lower the graphite/oxidizer ratio,the smaller the size of GOQDs obtained;GOQDs emitting blue,green,yellow and orange fluorescence can be obtained under different experimental conditions,and the smallest average size can reach 2.31 nm.This low-cost,simple and rapid preparation method brings the possibility of large-scale preparation of GOQDs.