Preparation And Properties Of Graphene/titanium Dioxide/nanocrystalline Cellulose Electro-conductive Film

Nanocrystalline cellulose（NCC）, one kind of cellulose crystals, is mainly derived from the hydrolysis of native cellulose. It is well-known that the amorphous area of cellulose was easy to be removed in the presence of the attack of strong acid, which provides opportunities for the production of NCC. Due to its high strength, low thermal expansion rate, good biodegradable and biocompatibility, NCC shows a great promise in the application and development of flexible transparent film. Graphene is known as the thinnest two-dimensional materials in the world that possesses a thickness of only 0.335 nm. It exhibits attractive characteristics, e.g., high mechanical strength（1060 Gpa）, great specific surface area（2600 m2/g）, and ultra high electron mobility（2×105 cm2/V·s）. Due to its unique two-dimensional honeycomb lattice structure, graphene displays very excellent mechanical, optical, electrical, and thermal performance, holding a great application prospect in super capacitors, solar cells, display, biological detection and fuel cell. In this sense, in the present work, the concept of the production of flexible electro-conductive films using NCC as base material and graphene as conductive filler was proposed/demonstrated. This work may provide an effective approach for the efficient production of flexible transparent electro-conductive film.For the above purpose, NCC was firstly extracted from microcrystalline cellulose（MCC） of cotton material by sulphuric acid hydrolysis process. The obtained NCC exhibited a diameter of 30-80 nm and a length of 300-600 nm. Subsequently, a modified Hummers method was introduced and used to prepare graphene oxide（GO）. Afterwards, photocatalytic reduction of graphene oxide was achieved in the presence of titanium dioxide as a catalyst. Also, the obtained RGO/TiO₂ nanocomposites were characterized by FT-IR, TEM, XRD and TG techniques. The results showed that the RGO/TiO₂ nanocomposites experienced a significant decrease in dispersion stability largely due to the removal of oxygen-containing groups, e.g.,-OH,-COOH and C=O groups as a result of the reduction process, which was confirmed by FT-IR analysis. The intensity of GO peak was reduced obviously according to XRD results. TG curves confirmed that the RGO/TiO₂ nanocomposites showed an improvement in thermal stability properties. TEM images showed that a small amount of nanosized TiO₂ particle located on the single-layer RGO.Eventually, the production of transparant electro-conductive film was performed by vacuum filtration using RGO/TiO₂ as electro-conductive filler and NCC as base material, respectively. The desired technological conditions for transparent electro-conductive film were achieved. The microstructure, electrical conductivity, mechanical properties and optical properties of the obtained products were studied. The results showed that when the ratio of RGO/TiO₂ was 9:1 and RGO/TiO₂ nanocomposites addition was 1%, the produced electro-conductive film exhibited a desired conductivity, optical properties and mechanical properties. Its conductivity reached 9.3 S/m, and light transmittance was 31.5%. When the applied maximum tension and tensile strain of conductive film reached 32.5 MPa and 1.25%, respectively, RGO/TiO₂/NCC composite conductive films became fracture. The elastic modulus and tensile strength of RGO/TiO₂/NCC composite conductive film reached 3998 and 18.1 MPa, which was increased by 14% and 13% as compared to the controlled NCC film. SEM images showed that the produced RGO/TiO₂/NCC composite conductive film exhibited a smooth surface. TG results indicated that the RGO/TiO₂/NCC composite conductive film showed an improvement in thermal stability properties as compared to the controlled one.