Thermally Controlled Bonding of Adenine to Cerium Oxide: Effect of Substrate Stoichiometry, Morphology, Composition, and Molecular Deposition Technique

Abstract

The adsorption of adenine, one of the structural units of DNA and RNA, on nanostructured cerium oxide was studied using synchrotron radiation based techniques: photoelectron and X-ray absorption spectroscopies. Using a systematic approach, we studied this biomolecule's bonding to the inorganic surface and examined the effects of different stoichiometry, morphology and composition of cerium oxide films, as well as two methods of molecular deposition (evaporation in vacuum and deposition from aqueous solution). The adenine molecule chemisorbs on the stoichiometric (IV) cerium oxide intact via nitrogen atoms, independent of the oxide morphology and deposition technique. Annealing of the adenine adlayer at 250 °C causes CeO 2 surface partial reduction, along with the partial deprotonation of the nitrogen. The reaction of adenine with ex situ prepared CeO 2 films (nanostructured compact and porous) activates Ce 4+ cation reduction not only on the surface but also in the subsurface layers accompanied by water desorption. The adenine molecule was found to oxidize and decompose on a reduced surface of the cerium oxide, and for a higher degree of oxide reduction, the temperature of decomposition is lower. The concentration of oxygen vacancies on the surface determines the degree of adenine stability on cerium oxide.

Electrochemical activity of the polycrystalline cerium oxide films for hydrogen peroxide detection

“…A detailed description of the beamline end station can be found in Ref. [26]. The Ce 3d core levels were acquired with 1486.6 eV (Al Kα radiation) photon energy and total resolution of 1.00 eV.…”

“…The Ce 3d core levels were acquired with 1486.6 eV (Al Kα radiation) photon energy and total resolution of 1.00 eV. The valence band (VB) spectra measured at photon energies of 121.4, 124.8 and 115 eV, with total resolution of 0.17 eV, provided resonant spectra of cerium [26]. The emission from Ce 4f states at binding energy about 1.4 eV (photon energy 121.4 eV) and emission from hybridized oxygen-cerium states at about 4.0 eV (photon energy 124.8 eV) relative to the off-This item was downloaded from IRIS Università di Bologna (https://cris.unibo.it/)…”

“…The resonance enhancement ratio (RER), i.e. D(Ce 3+ ) to D(Ce 4+ ) signal ratio [26], was analysed and used as a measure of reduction of surface cerium cations (see Results section for details).…”

“…2a) corresponds well to a fully oxidized ceria film with a minor contribution of Ce 3+ centres. The average oxide stoichiometry of CeO1.96 was determined by fitting of the Ce 3d spectrum [26]. The analysis of resonant processes in the VB spectra excited by photon energies 121.4 and 124.5 eV (Fig.…”

Role of the redox state of cerium oxide on glycine adsorption: an experimental and theoretical study

“…18,21,50 The BE of the photoemission features for the adlayers on Ce 2 O 3 was systematically higher than that for the glycine/CeO 2 system, which was attributed to the different band bending of the semiconducting oxide films. 40,51 The integral intensities of the N 1s and C 1s signals after annealing at each temperature are shown in Fig. 4a.…”