IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA2
Two Dimensional Crystallisation of Nucleic Acid Bases on Cu{110}

Wednesday, October 31, 2001, 2:20 pm, Room 121

Session: Adsorption on Metal Surfaces
Presenter: N.V. Richardson, University of St Andrews, UK
Authors: N.V. Richardson, University of St Andrews, UK
D.J. Frankel, University of St Andrews, UK
Q. Chen, University of St Andrews, UK
Correspondent: Click to Email
There is considerable interest in the characterisation and control of biomaterial surfaces. An important step towards this goal is a better, molecular level understanding of model systems based on two dimensional arrays of biorelevant molecules. In this presentation, the adsorption of the nucleic acid bases, uracil (U), thymine (T), cytosine (C), guanine (G) and adenine (A), on Cu{110} has been studied in depth by scanning tunneling microscopy, electron energy loss spectroscopy and low energy electron diffraction. In general, all the molecules form well-ordered 2D structures when vacuum deposited on a room temperature Cu{110} crystal, or at least after moderate annealing. A variety of ordered structures are found for each molecule dependent on coverage and temperature. The pyrimidine bases U, C and T form related structures involving upright molecules and, following loss of hydrogen, adsorbed species in well ordered structures are stable to over 700K. Further heating, results in major re-faceting of the uppermost (ca. ten) layers of the copper substrate giving rise to major new one or two dimensional features. In contrast the purine bases, A and G, form large, two dimensionally ordered domains based on flat-lying molecules without faceting. Hydrogen bonding is a key feature of all the networks. Models of the surface structures will be presented. We also note that although these planar molecules are optically inactive, the single mirror plane is destroyed by adsorption and the resulting surface species is then chiral. This is important in the 2D crystal structures and can result in chiral domains on the surface. .