Intercalation of Organic Ammonium Ions into Layered Graphite Oxide

The intercalation of large organic ammonium ions (tetramethylammonium ions (TMA + ), tetraethylammonium ions (TEA + ), tetrapropylammonium ions (TPA + ), and tetrabutylammonium ions (TBA + )) into layered graphite oxide (GO) was systematically investigated. The intercalation reactions were completed at 25 °C after 3 days, and stable colloidal suspensions were obtained at TAA l /H s = 5 (molar ratio of tetraalkylammonium ions (TAA + ) over exchangeable protons in GO). The sediments after centrifuging the colloidal suspensions showed amorphous phase X-ray diffraction patterns, indicating that exfoliation of the layered structure into nanosheets took place in the suspension. When the sediments were dried at 70 °C for 3 days, layered structures of TAA + -intercalated GO materials with basal spacings of 1.56, 1.67, 1.84, and 2.37 nm, respectively, appeared. The basal spacing of the layered compounds decreased with a decrease of relative humidity during drying. When the dried TAA + -intercalated GO compounds were exposed to a humid saturated atmosphere, the basal spacing increased gradually, finally becoming an amorphous structure. The maximum saturation of intercalated TAA + ions into GO decreased with the increase in alkyl chain length. When the TAA + -intercalated materials were washed with distilled water and acid-treated, a process of deintercalation of TAA + ions from the interlayer occurred. A schematic model for the deintercalation−intercalation involving a exfoliation process is proposed. The layered structure of TAA + -intercalated GO materials is discussed in terms of the dimension of the GO layer and the sizes of H 2 O molecules and TAA + ions.