Langmuir−Blodgett Assembly of Graphite Oxide Single Layers

Abstract

Single-layer graphite oxide can be viewed as an unconventional type of soft material and has recently been recognized as a promising material for composite and electronics applications. It is of both scientific curiosity and technical importance to know how these atomically thin sheets assemble. There are two fundamental geometries of interacting single layers: edge-to-edge and face-to-face. Such interactions were studied at the air-water interface by Langmuir-Blodgett assembly. Stable monolayers of graphite oxide single layers were obtained without the need for any surfactant or stabilizing agent, due to the strong electrostatic repulsion between the 2D confined layers. Such repulsion also prevented the single layers from overlapping during compression, leading to excellent reversibility of the monolayers. In contrast to molecular and hard colloidal particle monolayers, the single layers tend to fold and wrinkle at edges to resist collapsing into multilayers. The monolayers can be transferred to a substrate, readily creating a large area of flat graphite oxide single layers. The density of such films can be continuously tuned from dilute, close-packed to overpacked monolayers of interlocking single layers. For size-mismatched single layers, face-to-face interaction caused irreversible stacking, leading to double layers. The graphite oxide monolayers can be chemically reduced to graphene for electronic applications such as transparent conducting thin films.

A low-temperature method to produce highly reduced graphene oxide

“…A typical broad peak near 10.21°(d-spacing B8.67 A) was observed for the GO powder. Compared with the parent GO, the peak of RGO Na-NH3 shows a obvious shift to higher 2y angles (25.04°; d-spacing B3.56 A) and is narrower than that of highly RGO (B23°; d-spacing B3.86 A) obtained previously 22 , suggesting that RGO Na-NH 3 was well ordered with two-dimensional sheets with more thorough removal of surface functional groups.…”

“…GO was prepared from natural graphite powder (Bay Carbon; SP-1 graphite) using the modified Hummers method 22,41 .…”

“…The reduction of GO by pure hydrazine in the solution phase is particularly interesting because it can produce RGO of relative high quality with relatively small oxygen content 18 . Direct reduction of GO film has also been reported by exposure to hydrazine vapour and/or annealing at high temperature [19][20][21][22] . However, these approaches often involve highly toxic chemicals, require long reduction time, or require hightemperature treatment that are incompatible with flexible plastic substrates, and produce RGO with a relatively high oxygen content (B49%) to give rise to high sheet resistance 23 .…”

Self‐Assembled Graphene‐Based Architectures and Their Applications

“…Considering that amphiphilic GO sheets are able to be readily dispersed in aqueous solution and certain organic solvents, GO has now been considered as a popular precursor for fabricating large‐area graphene films 12, 13. Huang and co‐workers demonstrated that stable monolayer GO films could be achieved without using any stabilizing agent by the LB technique, as shown in Figure 1 14. The monolayers are easy to form a large‐area, and flat GO film with adjustable density from dilute close‐packed to overpacked monolayers.…”

“…Scale bars in panels (a)–(d) represent 20 µm. Reproduced with permission 14. Copyright 2009, American Chemical Society.…”