Study Of Preparation And Properties Of Graphene-based Conductive Paper

Graphene, a one-atom-thick 2D carbon sheet with the sp2 hybridized carbon atoms densely packed in a honeycomb crystal lattice, has stimulated a large amount of researches due to its outstanding electrical, mechanical, optical, and thermal properties since it was found by Novoselov and Geim in 2004. Cellulose, a natural polymer abounded in the earth, which possesses special advantages such as degradable, renewable, green and environmentally friendly, etc. Integrating the miracle materialgraphene and the natural material-cellulos or cellulose derivative to prepare the conductive paper possesses excellence electrical property and mechanical property, which has a promising application in the eletronic field such as supercapacitor, smart wearable devices and flexble displays, etc.In this study, tea polyphenols and aluminum flakes, zinc sheets was first utilized as the reductants to reduce graphene oxide and then synthesize graphene possessing better conducitivity. The influence of reductants and dosage to the graphene’s structure and conductivity were discussed. We adopted vacuum filtration and simple pendrawing method to prepare graphene-based conductive paper and flexible paper-based conducting circuit, the performance of the cellulose/graphene conductive paper, cellulose oxide/graphene conductive paper and nanocellulose/graphene conductive paper were studied, the conductivity of the flexible paper-based conducting circuit was also characterized. Besides, the surface tension and viscosity of the graphene dispersion were adjusted by sodium dodecyl sulfate(SDS) to prepare graphene-based conductive ink, the ink was applied in the process of inkjet priting. Here are the research contents and results in details:1. Adopting tea polyphenos as reductant to prepare graphene, the influence of reaction time, graphene oxide to tea polyphenols ratio and reaction temperature to the graphene’s conductivity were studied. The results show that the optimal conditions is reaction time 2h, graphene oxide to tea polyphenols ratio 1:1 and the reaction temperature 80℃. The sheet resistance of the as-prepared graphene is 371.76Ω/sq.2. Adopting tea polyphenos/zinc sheets and tea polyphenols/aluminum flake as reductants to prepare graphene, the influence of aluminum flakes, zinc sheets added ratio in the tea polyphenols reduction system to the reduction effect were studied. In the recombination reduction system of tea polyphenols and zinc sheets, the optimal ratio between graphene oxide, tea polyphenols and zinc sheets is 1:1:2, the sheet resistance of the as-prepared graphene is 209.11Ω/sq. In the recombination reduction system of tea polyphenols and aluminum flakes, the optimal ratio between graphene oxide, tea polyphenols and aluminum flakes is 1:0.5:4, the sheet resistance of the as-prepared graphene is 61.75Ω/sq, the graphene height is 0.821 nm, which suggests graphene possesses a single layer structure.3. The influence of composite ratio between cellulose and graphene and the cellulose dosage to the conductive paper’s electrical property and mechanical property were discussed. The optimal conditions is composite ratio between cellulose and graphene 1:1, the cellulose dosage 0.0500 g. The sheet resistance, elasticity modulus and specific capacitance of the as-prepared conductive paper is 66.33Ω/sq, 1234.00 MPa and 5.47mF/cm2, respectively. The conductive paper reserved good conductivity after 500 times folding and possessed of excellent hydrophobic property and flame resistance.4. The influence of the cellulose oxide degree to the conductive paper’s electrical property and mechanical property was discussed. As the increasing of the cellulose oxide degree, the elasticity modulus increased while the conductivity decreased. When the cellulose oxide degree is low(NaClO added 1.5 mmol/g), the elasticity modulus and sheet resistance of the cellulose oxide/graphene conductive paper is 1571.71 MPa, 78.57Ω/sq respectively, which increasing by 27.4%, 18.5% contrasted to the cellulose/graphene conductive paper.5. The influence of the nanocellulose oxide degree and composite ratio between nanocellulose and graphene to the conductive paper’s electrical property and mechanical property were discussed. The nanocellulose/graphene conductive paper possesses perfect mechanical property, the elasticity modulus is as high as 13154.72 MPa. On the same composite ratio, the sheet resistance of the conductive paper decreases with the increasing of oxide degree.6. The influence of SDS dosage to the graphene dispersion’s surface tension and viscosity were discussed. When SDS dosage is 0.2mg/ml, the surface tension, viscosity, sheet resistance and particle size of the graphene-based conductive ink is 39.889mN/m, 9.025 mPa.s, 179.81Ω/sq and 200-300 nm, respectively. Besides, the graphene-based ink possesses excellent adhesive force and chemical resistance, which meet the standards of inkjet priting and can form complete graphs and text after printing.7. Adopting pen-drawing method to prepare flexible paper-based conducting circuit, the conductivity is 2.81 × 102S/m, which can still light the LED in the conductive path after curlating, indicating the good flexibility and stable conductive performance.