Ionization energy and electronic structure of polycytidine.
Ribonucleic acid (RNA) polycytidine (poly rC) homopolymer thin films were prepared on highly oriented pyrolytic graphite (HOPG) substrates. The films were grown from aqueous solution directly in a vacuum in multiple steps with use of an electrospray (ES) deposition system. Before poly rC deposition and after each deposition step the sample was characterized with X-ray and ultraviolet photoemission spectroscopy (XPS, UPS). Evaluation of the UP-spectra sequence allowed the determination of ionization energy and highest occupied molecular orbital (HOMO) electronic structure, as well as the charge injection barriers between HOPG and poly rC. Comparison with earlier results on polyadenosine (poly rA) indicates significant differences between ionization energies (poly rC: 8.1 eV; poly rA: 6.8 eV) and orbital alignment at the graphite interface. The larger ionization energy of poly rC results in a larger hole injection barrier and a smaller electron injection barrier relative to the HOPG Fermi level.
Magulick
J
J
Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620, USA.
Beerbom
M M
MM
Lägel
B
B
Schlaf
R
R
D004583:Electrons; D006108:Graphite / Q000737:chemistry; D007700:Kinetics; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods; D010316:Particle Size; D011066:Poly C / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties; D014965:X-Rays
D008567:Membranes, Artificial; D011066:Poly C; D012313:RNA; D006108:Graphite