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 degreesC after 3 days, and stable colloidal suspensions were obtained at TAA(l)/H-8 = 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 degreesC for 3 days, layered structures of TAA(+)-intercalated GO materials with basal spacings of 1.56, 1.67, 1.84, and 2.37 =, 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 H2O molecules and TAA(+) ions.