Aqueous Exfoliation Research Articles

Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2–5nm-thick tactoids with a radial dimension of 0.2–0.5μm.

Preparation of graphene oxide by solvent-free mechanochemical oxidation of graphite

Graphenes with different oxidation degrees are prepared by ultrasound assisted aqueous exfoliation of solvent-free mechanochemically treated graphite in the presence of solid oxidants, under comparatively mild conditions without using aggressive concentrated acids.

Thin Film Graphene Supercapacitor Electrodes Produced by Aqueous Exfoliation and Spray Deposition

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Homogeneous Precipitation by Formamide Hydrolysis: Synthesis, Reversible Hydration, and Aqueous Exfoliation of the Layered Double Hydroxide (LDH) of Ni and Al

Homogenous precipitation by formamide hydrolysis results in the formation of a formate-intercalated layered double hydroxide (LDH) of Ni(II) and Al(III). The formate-LDH is sensitive to the atmospheric humidity and reversibly exchanges its intercalated water with atmospheric moisture. The hydration/dehydration cycle is complete within a narrow range of 0-30% relative humidity with significant hysteresis and involves a randomly interstratified intermediate phase. When immersed in water, the formate ion grows its hydration sphere (osmotic swelling), eventually leading to the exfoliation of the metal hydroxide layers into lamellar particles having in-plane dimensions of 100-200 nm and a thickness of 9-12 nm. These nanoplatelets restack to thicker tactoids again upon evaporation of the dispersion. The intercalated formate ion can be exchanged with nitrate ions in solution but not with iodide ions. These observations have implications for many applications of LDHs in the area of carbon dioxide sorption and catalysis.