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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Charge injection barriers at a ribonucleic acid/inorganic material contact determined by photoemission spectroscopy
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Charge injection barriers at a ribonucleic acid/inorganic material contact determined by photoemission spectroscopy

机译：通过光发射光谱法确定核糖核酸/无机材料接触时的电荷注入势垒

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摘要

Ribonucleic acid (RNA) homopolymer thin films on highly oriented pyrolytic graphite (HOPG) were prepared in ultrahigh vacuum (UHV) directly from aqueous solution by electrospray (ES) injection. The polyadenosine (poly rA) films were prepared in several steps of increasing thickness without breaking the vacuum. Before deposition and between deposition steps, the samples were characterized with photoemission spectroscopy (PES). Both X-ray and ultraviolet photoemission spectroscopy (XPS and UPS) were employed. XPS enabled the detailed measurement of core level peaks, giving insight into the chemical interaction at the interface and the layer morphology. The corresponding UP-spectra sequence allowed us to directly follow the transition from HOPG valence bands to the poly rA highest occupied molecular orbital (HOMO) structure. This enabled the determination of the poly rA ionization energy and work function as well as the charge injection barriers between the Fermi level of the HOPG substrate and the poly rA HOMO. The injection barrier between the lowest unoccupied molecular orbital (LUMO) and the HOPG Fermi level was determined using the HOMO-LUMO gap value determined by optical absorption. The results indicate that significant injection barriers exist between HOPG and the poly rA overlayer, limiting conductivity across this interface.
机译：在超高真空（UHV）中直接通过电喷雾（ES）注射从水溶液中制备高度取向的热解石墨（HOPG）上的核糖核酸（RNA）均聚物薄膜。聚腺苷（poly rA）膜是通过增加厚度而不破坏真空的几个步骤来制备的。在沉积之前和沉积步骤之间，用光发射光谱法（PES）对样品进行表征。 X射线和紫外光发射光谱法（XPS和UPS）均被使用。 XPS可以对核心能级峰进行详细测量，从而深入了解界面处的化学相互作用和层形貌。相应的UP光谱序列使我们可以直接追踪从HOPG价带到poly rA最高占据分子轨道（HOMO）结构的跃迁。这样就可以确定poly rA电离能和功函数，以及HOPG衬底的费米能级和poly rA HOMO之间的电荷注入势垒。最低的未占据分子轨道（LUMO）和HOPG费米能级之间的注入势垒是使用由光吸收确定的HOMO-LUMO间隙值确定的。结果表明，HOPG和poly rA覆盖层之间存在明显的注入势垒，从而限制了该界面的电导率。

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