Iron Oxides/Graphene Composites:Synthesis, Electromagnetic Wave Absorption And Self-cleanable SERS Application

Graphene/iron oxides composites play a key role in energy and environmental science area, such as Li-ions batteries、supercapacitors、photocatalysts and electromagnetic wave absorption materials et al. Much effort has been devoted to the development of graphene/iron oxides composites, which have shown promising applicatioin in sustainable energy and the protection of environment. So, the development of new synthesis method of graphene/iron oxides composites with high performance for various applications has become an active research area. Electromagnetic wave absorption, analytic techniques based on surface-enhanced Raman spectroscopy (SERS) and photocatalytic degradation of organic contaminants are three important topics in environmental science. In the thesis, we reported that some kinds of iron oxides/graphene composite were synthesized via simultaneous thermal decomposition and thermal reduction method and hydrothermal synthesis techniques, which is beneficial to the reduction of production cost and the tailoring of physical and chemical properties. What is more, the obtained composites may find its applications in electromagnetic wave absorption and water treatment. The main results are included as follows.1. By using simultaneous thermal decomposition and thermal reduction of FeSO4·7H2O and graphene oxide mixture at different temperatures, α-Fe2O3/reduced graphene oxide (rGO) and Fe3O4/rGO composites were synthesized successfully, whose phase can be regulated among α-Fe2O3, γ-Fe2O3 and Fe3O4. Through analyzing the TG/DTG and FT-IR data of graphene oxide/FeSO4·7H2O composite treated at different temperature points, it is found that hydroxyl groups at edges and surface of graphene oxide sheets and H2 orignated from the thermal reduction of graphene oxide process induced the transformation of α-Fe2O3 into γ-Fe2O3 in the 540℃～700℃ range. The reducing agents such as CO, H2 and CH4 produced from the thermal reduction of graphene oxide reacted with α-Fe2O3 and γ-Fe2O3, forming the phase of Fe3O4 in the 700℃～800℃ range. Electromagnetic wave absorption tests showed that the samples synthesized at different temperatures possessed good electromagnetic wave absorption performance, which is better than the mixuture of separately produced Fe3O4 and rGO and commerical absorber [Fe, Ni]. Especially, the product obtained at 700℃ showed a maximum reflection loss values-17.1dB at 6.72 GHz. More importantly, the electromangnetic wave absorbing performance can be adjusted by changing the content of graphene oxide in the strarting materials.2. α-Fe2O3/rGO composites were synthesized by hydrothermal technique and the composites can be used as SERS (surface-enhanced Raman scattering) substrates and recyclable photocatalysts to detect and remove organic contaminants in the aqueous solution. The experimental results showed that the detection limit of rhodamine 6G on α-Fe2O3/rGO composite substrates can reach as low as 10-6 mol/L. In addition, the composites showed excellent recyclable photodegradation abilities for some organic containments, such as rhodamine 6G, methyl orange, methylene blue and bisphenol A.