Tailoring the Self-assembly of Melamine on Au(111) via Doping with Cu Atoms

Abstract

The doping effect of Cu on the self-assembly film of melamine on an Au(111) surface has been investigated with scanning tunneling microscopy (STM). The evaporated Cu adatoms occupy the positions underneath the amino groups and change the hydrogen bonding pattern between the melamine molecules. Accordingly, the self-assembly structure has changed stepwise from a well-defined honeycomb into a track-like and then a triangular structure depending on the amount of Cu adatoms. The interaction between Cu adatom and melamine is moderate thus the Cu adatoms can be released upon mild heating to around 100 °C. These findings are different from previous observations of either the coordination assembly or the physically trapped metal adatoms.

Structure and Reactivity of Cu-doped Au(111) Surfaces

“…1(d). Recently, dark features were attributed to embedded copper atoms, rather than to missing gold atoms [18]. The dark appearance of the copper atoms is tentatively explained on the basis of both electronic and geometrical considerations.…”

“…This behavior, along with atomically resolved STM images, was taken as an indication that the copper and gold layers are defective and intermixed. When copper is evaporated on a melamine self-assembled monolayer (SAM) on Au(111), incorporation under the amine groups of melamine is reported [18]. The Cu-melamine interaction is regarded as moderate, as melamine doesn't appear to favour the segregation of copper atoms from subsurface to the top surface layer, yet sufficiently strong to disrupt locally the ordering of the hydrogen bonded supramolecular assembly.…”

“…The Cu-melamine interaction is regarded as moderate, as melamine doesn't appear to favour the segregation of copper atoms from subsurface to the top surface layer, yet sufficiently strong to disrupt locally the ordering of the hydrogen bonded supramolecular assembly. Such metal-organic structure has suggested to potentially act as a reservoir for supplying reactive atoms, if the chemistry of the system is tuned appropriately [18].…”

Understanding of Structure and Thermodynamics of Melamine Association in Aqueous Solution from a Unified Theoretical and Experimental Approach

“…The determinants of cyanuric acid and melamine assembly in water were also observed . The supramolecular frameworks of melamine by extensive hydrogen bonds between different sites have been proposed − in solvents as well as upon solid surfaces − due to having its hydrogen donor–acceptor property. Single component-assembled melamine structures on various surfaces like Cu/Au(111) were shown both experimentally and theoretically. − …”

Copper Adatoms Mediated Adsorption of Benzotriazole on a Gold Substrate

“…Often the presence of adatoms is inferred from the spacing between STM features, without a direct observation [7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Single adatoms can seldom be identified when isolated [18][19][20], in an organometallic compound [17,19,21], or when they form small clusters [12].…”