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Vibrational sum frequency and Raman ...

The Ohio State University.

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Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies./
作者:	Xu, Man.
面頁冊數:	149 p.
附註:	Adviser: Heather C. Allen.
Contained By:	Dissertation Abstracts International69-01B.
標題:	Environmental Sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3300136
ISBN:	9780549444978

Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies.
Xu, Man.

Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies. - 149 p.

Adviser: Heather C. Allen.

Thesis (Ph.D.)--The Ohio State University, 2008.

Nitrate ions are ubiquitous in aqueous-phase atmospheric aerosols as well as surface and ground waters, and are involved in a variety of reactions in the atmosphere, hydrosphere, and biosphere. A fundamental understanding of nitrate ions at the air-aqueous interface is of prime importance with respect to understanding heterogeneous atmospheric chemistry and geochemistry. Surface activity at the air-aqueous interface may have consequences for diffusion rates and reaction pathways within the interface. Although numerous arguments have been proposed concerning the nature of nitrate ions at aqueous interfaces, there is a lack of detailed molecular-scale experimental evidence. In the studies presented in this dissertation, vibrational sum frequency generation (VSFG) spectroscopy, an interface specific technique that provides direct molecular-level interfacial information, was employed as the primary investigational technique to elucidate the nature of nitrate ions and formation of ion pairs at the air-aqueous interface, and to reveal their influence on the interfacial water structure. Raman and infrared spectroscopies were utilized in addition to VSFG spectroscopy.

ISBN: 9780549444978Subjects--Topical Terms:

676987
Environmental Sciences.

Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies.
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020 $a 9780549444978
035 $a (UMI)AAI3300136
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100 1 $a Xu, Man. $3 1028870
245 1 0 $a Vibrational sum frequency and Raman spectroscopic studies of air-aqueous interfaces and solutions of nitrate salts, and air-silica surface adsorption studies.
300 $a 149 p.
500 $a Adviser: Heather C. Allen.
500 $a Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0199.
502 $a Thesis (Ph.D.)--The Ohio State University, 2008.
520 $a Nitrate ions are ubiquitous in aqueous-phase atmospheric aerosols as well as surface and ground waters, and are involved in a variety of reactions in the atmosphere, hydrosphere, and biosphere. A fundamental understanding of nitrate ions at the air-aqueous interface is of prime importance with respect to understanding heterogeneous atmospheric chemistry and geochemistry. Surface activity at the air-aqueous interface may have consequences for diffusion rates and reaction pathways within the interface. Although numerous arguments have been proposed concerning the nature of nitrate ions at aqueous interfaces, there is a lack of detailed molecular-scale experimental evidence. In the studies presented in this dissertation, vibrational sum frequency generation (VSFG) spectroscopy, an interface specific technique that provides direct molecular-level interfacial information, was employed as the primary investigational technique to elucidate the nature of nitrate ions and formation of ion pairs at the air-aqueous interface, and to reveal their influence on the interfacial water structure. Raman and infrared spectroscopies were utilized in addition to VSFG spectroscopy.
520 $a Investigations of ion pairing in a series of divalent metal-nitrate solutions were carried out using Raman and infrared spectroscopies. The spectral features of the nitrate vibrational modes indicate that the ion pairing in the metal-nitrate aqueous solutions are concentration and cation dependent. Pb2+ has a strong tendency to form ion pairs with nitrate anions, and the formation of contact ion pairs decreases with decreasing cation size and increasing cation charge density: Pb2+ > Sr2+ > Ca 2+ > Mg2+.
520 $a At the air-aqueous interface, the vibrational symmetric stretch mode of nitrate ions was directly probed by VSFG. Analysis of the VSFG spectra reveals the perturbation from cation-anion interactions on interfacial nitrate ions. Mg(NO3)2 is particularly interesting at the air-aqueous interface. At low bulk concentration of Mg(NO3)2, interfacial nitrate anions are relatively free from Coulombic effects of Mg2+ cations, which indicates that the number of water molecules available for solvation significantly affects the extent of interfacial ion pairing. This finding and the associated spectral identification shed additional light on the level of interaction between Mg2+ and nitrate in the bulk solution. That is, in previous bulk studies, it has been accepted that Mg 2+ causes negligible perturbation on nitrate and therefore, no significant ion pairing interactions were concluded. With the results from this dissertation, although the frequency of the nitrate symmetric stretch does not change significantly in bulk aqueous Mg(NO3)2 systems with concentration, the bulk frequency is in fact evidence of Mg2+-nitrate interaction, solvent-shared or solvent-separated ion pairing most likely. This is clear only after the completion of our interfacial studies that reveal a never before observed frequency from aqueous Mg(NO3)2 systems.
520 $a The addition of nitrate salts also has considerable effects on the interfacial water structure, as observed in our VSFG studies of the OH stretching modes. The sum frequency spectral features reveal that the presence of nitrate anions, metal cations, and the ion pairs perturbs the water hydrogen-bonding network at the air-aqueous interface, and the perturbation varies with cation. We propose an increasing interfacial depth as the cation size increases: Mg 2+ < Ca2+ < Sr2+. Interfacial depth is defined by non-bulk behavior. That is, the cation and anion concentrations are not constant in the first few layers of the air-aqueous interface. Alternatively, concentrations are changing deeper into what is traditionally called the bulk liquid.
520 $a In additional studies, distinct from the ion-pairing work at the air-aqueous interface, the surface acidity of silica, which is also atmospherically and geochemically important, was determined by using a surface acidity probe molecule, ethylenediamine (H2N(CH2)2NH2, EDA). The VSFG study of EDA adsorption onto silica surfaces indicate that the adsorption occurs via protonation of an amine group by a silica surface silanol site. The surface acidity of silica is therefore in the range of two pKa values of EDA: 7.56 to 10.71.
590 $a School code: 0168.
650 4 $a Environmental Sciences. $3 676987
650 4 $a Geochemistry. $3 539092
690 $a 0768
690 $a 0996
710 2 $a The Ohio State University. $3 718944
773 0 $t Dissertation Abstracts International $g 69-01B.
790 $a 0168
790 1 0 $a Allen, Heather C., $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3300136