Smith Jacob W, Lam Royce K, Shih Orion, Rizzuto Anthony M, Prendergast David, Saykally Richard J
Department of Chemistry, University of California, Berkeley, California 94720, USA.
National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
J Chem Phys. 2015 Aug 28;143(8):084503. doi: 10.1063/1.4928867.
Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopy (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO3 (-) and NO2 (-). The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.
硝酸根离子和亚硝酸根离子备受关注，这既是因为它们在商业和研究领域有着广泛应用，也是由于它们在全球氮循环中发挥着核心作用。大气气溶胶的化学性质（其中硝酸盐含量丰富）已被发现取决于离子物种的界面行为。离子的界面行为很大程度上由其水合性质决定；因此，对硝酸根和亚硝酸根的水合及界面行为的研究构成了一个重要的研究领域。在这项工作中，我们描述了通过X射线吸收光谱法（XAS）对硝酸钠和亚硝酸钠水溶液的研究，并根据第一性原理密度泛函理论电子结构计算进行解释。本体溶液中氮K边XA光谱的实验和计算光谱显示，硝酸根和亚硝酸根的XA光谱之间存在3.7 eV的大位移，这是由于硝酸根中氮1s能级的更大稳定性所致。在NO3 (-)和NO2 (-)的氧K边XA光谱中未观察到类似的位移。发现硝酸根和亚硝酸根的水合性质相似，两种阴离子表现出相似的离子配对倾向。
