Graphene Oxide Nanocolloids

Abstract

Graphene oxide (GO) nanocolloids-sheets with lateral dimension smaller than 100 nm-were synthesized by chemical exfoliation of graphite nanofibers, in which the graphene planes are coin-stacked along the length of the nanofibers. Since the upper size limit is predetermined by the diameter of the nanofiber precursor, the size distribution of the GO nanosheets is much more uniform than that of common GO synthesized from graphite powders. The size can be further tuned by the oxidation time. Compared to the micrometer-sized, regular GO sheets, nano GO has very similar spectroscopic characteristics and chemical properties but very different solution properties, such as surface activity and colloidal stability. Due to higher charge density originating from their higher edge-to-area ratios, aqueous GO nanocolloids are significantly more stable. Dispersions of GO nanocolloids can sustain high-speed centrifugation and remain stable even after chemical reduction, which would result in aggregates for regular GO. Therefore, nano GO can act as a better dispersing agent for insoluble materials (e.g., carbon nanotubes) in water, creating a more stable colloidal dispersion.

Tunable sieving of ions using graphene oxide membranes

“…GO membranes with different IL spacing were prepared by storing them in a sealed container with different RH of 0%, 12%, 33%, 75%, 84% and 100%. To this end, we used saturated solutions of LiCl (12% RH), MgCl 2 (33%), NaCl (75%) and KCl (84%), which were prepared by dissolving excess amounts of salts in deionised water 30,36 . A humidity meter was used inside the container to check that the salts provided the literature values of RH.…”

“…Graphene oxide (GO) has previously been suggested as a 2D-surfactant to prepare stable dispersions of graphite and carbon nanotubes (CNTs) in water 29,30 . Here, graphene oxidegraphene (GO-Gr) aqueous dispersions were prepared by exfoliating graphite in water using GO as a surfactant.…”

“…The laminates were cut into rectangular strips (4 mm × 10 mm) and stored for one to two weeks at different relative humidities (RH), achieved using saturated salt solutions 18,30 . The resulting interlayer spacing was measured by X-ray diffraction as shown in Fig.…”

Control of size and physical properties of graphene oxide by changing the oxidation temperature

“…Therefore, control of graphite oxidation is necessary for various applications of graphene oxide sheets. It was recently reported that graphene oxide sheets with different oxygen content amounts can be prepared simply by changing the starting graphite, oxidation time, and amount of oxidant, providing variation in the size distribution, electrical conductivity, and energy band gap [21][22][23][24]. However, no correlation between the properties or size of graphene oxide sheets and the oxidation temperature has been reported thus far.…”

Nanoscale assembly into extended and continuous structures and hybrid materials

“…72 These structures are 2-3 nm in diameter, have two or three p-stacked PAH moieties comprising the core, and an oxygen-rich corona. 73 The optical properties of these structures are highly dependent on particle size; the absorption maxima red-shifts with increased particle size, while emission wavelength depends on the excitation energy, possibly due to variation in the density of defect sites associated with sp 2 carbons.…”