Elucidation of Different Steps Involved in Allylamine Functionalization of the Diamond Surface and Its Polymerization by Time-of-Flight Secondary Ion Mass Spectrometry

The H-terminated polycrystalline diamond thin film surface is photochemically functionalized using allylamine. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) aided by principal components analysis (PCA) is then employed to systematically elucidate (i) the photochemical grafting of trifluoroacetamide group protected allylamine (TFAAA) onto the diamond thin film surface and (ii) the deprotection of the amine group. PCA of the SIMS shows that the diamond surface is fully covered by TFAAA after 24 h of UV illumination. SIMS spectra (in the high mass range) show that TFAAA cross-polymerizes on the diamond surface before the whole surface is covered by TFAAA. PCA of the SIMS also shows that the deprotection reaction follows approximately an exponential law with a time constant of 1 h. Additionally, the unchanged CN- intensity in the deprotection step shows that the allylamine linkage to diamond is stable. A shadow mask was employed during the photochemical grafting of allylamine, leaving the masked region unfunctionalized. The SIMS mapping shows high intensities and homogeneous distribution of CN- in the region which is UV illuminated. On the basis of the overall SIMS analysis a modified chain reaction grafting model which illustrates a competition between TFAAA bonding and its cross-polymerization is discussed.