Graphene Oxide-Assisted Liquid Phase Exfoliation of Graphite into Graphene for Highly Conductive Film and Electromechanical Sensors

Abstract

Here, we report a new method to prepare graphene from graphite by the liquid phase exfoliation process with sonication using graphene oxide (GO) as a dispersant. It was found that GO nanosheets act a as surfactant to the mediated exfoliation of graphite into a GO-adsorbed graphene complex in the aqueous solution, from which graphene was separated by an additional process. The preparation of isolated graphene from a single to a few layers is routinely achieved with an exfoliation yield of up to higher than 40% from the initial graphite material. The prepared graphene sheets showed a high quality (C/O ∼ 21.5), low defect (ID/IG ∼ 0.12), and high conductivity (6.2 × 10(4) S/m). Moreover, the large lateral size ranging from 5 to 10 μm of graphene, which is believed to be due to the shielding effect of GO avoiding damage under ultrasonic jets and cavitation formed by the sonication process. The thin graphene film prepared by the spray-coating technique showed a sheet resistance of 668 Ω/sq with a transmittance of 80% at 550 nm after annealing at 350 °C for 3 h. The transparent electrode was even greater with the resistance only 66.02 Ω when graphene is deposited on an interdigitated electrode (1 mm gap). Finally, a flexible sensor based on a graphene spray-coating polydimethylsiloxane (PDMS) is demonstrated showing excellent performance working under human touch pressure (<10 kPa). The graphene prepared by this method has some distinct properties showing it as a promising material for applications in electronics including thin film coatings, transparent electrodes, wearable electronics, human monitoring sensors, and RFID tags.

A Review of Passive RFID Tag Antenna-Based Sensors and Systems for Structural Health Monitoring Applications

“…Conductive inks generally contain at least one kind of binder to form a continuous film, however, adding insulating binders such as polymeric or siloxane will reduce the ink conductivity [124]. For example, a graphene oxide (GO) assisted liquid-phase exfoliation process was demonstrated for the preparation of high-quality graphene from graphite, which is a little sacrifice of the conductivity, reported as 6.2 × 10 4 S/m) [125]. The other effective operating parameters on the film formation are surface temperatures, surface energy of the substrate, surface tension, and viscosity of the ink [126].…”

Graphene‐Based Transparent Conductive Films: Material Systems, Preparation and Applications

“…Interestingly, GO nanosheets can act as a surfactant to the mediated exfoliation of graphite into a GO‐adsorbed graphene complex in the aqueous solution ( Figure ) . In this approach, after ground with NaCl, EG powder is dispersed in the suspension of GO in water.…”

“…GO‐mediated exfoliation of graphene in aqueous solution. Reproduced with permission . Copyright 2016, American Chemical Society.…”

Recent Advances in Sensing Applications of Graphene Assemblies and Their Composites

“…Many approaches have been explored to address this problem using macroscopic graphene films, graphene fibers, graphene aerogels, graphene‐based composites as potential solutions for enhancing the sensitivity. In these cases, the sensing mechanism is more complicated when disconnectivity, microcrack propagation, and tunneling effects are included . Conductive fibers (1D), conductive films (2D), and macroscopic structures (3D) made of graphene platelets can allow electrons to flow through the overlapped graphene sheets within the percolation network .…”

“…Based on Simmons's model, the tunneling resistance between two neighboring graphene sheets is related to the shortest distance ( d ) between two graphene sheets defined in Equation . This model is popular for explaining the sensing mechanism of conductive polymer composite sensorswhere J is the tunneling current density, V is the electrical potential difference, A is the cross‐sectional area of the tunnel, e is the quantum of electricity, m is the mass of an electron, h is the Plank's constant, d is the distance between conductive particles, and λ is the height of the energy barrier.…”