The liquid-phase adsorption of n-octylamine onto the graphite basal surface studied by tapping-mode atomic force microscopy

Solid-like structures formed on the graphite basal surface following the li quid-phase adsorption of n-octylamine have been studied using tapping-mode atomic force microscopy. Following deposition of a 1 mu l droplet and subse quent annealing at 100 degrees C, the amine formed randomly distributed isl ands categorised into two types based upon the morphology at the vapour int erface. Evidence was found for the parallel orientation of the molecular ax is at the basal plane, the orientation anticipated from studies of other al iphatic molecules. The results suggest the formation of vertically oriented molecular clusters at the vapour interface. Similarities were found with p revious results of the adsorption of n-alkanes at the basal surface, highli ghting the importance of n-alkyl chain interactions. Similarities and diffe rences were observed between amine and alkane behaviour at the graphite ste ps. Annealing at 200 degrees C reduced the island coverage, particularly at steps, and at 300 degrees C no decoration was observed on the surface. The activation energy for surface diffusion and the energy difference between surface and vapour molecules are estimated. Upon deposition of a 5 mu l dro plet of amine onto graphite, an aggregate morphology decorated terraces and steps. Measurements suggest that the aggregate surface consisted of molecu lar clusters oriented towards the surface normal. (C) 2000 Elsevier Science B.V. All rights reserved.