Langmuir monolayers can be employed as simple model systems to study interactions at surfaces. Such investigations are important to fields ranging from biology to materials science. Herein, several aspects of these films and their associated water structure have been examined with vibrational sum frequency spectroscopy (VSFS). This second order nonlinear optical spectroscopy is particularly well suited for simultaneous investigations of the monolayer and the associated water structure with unprecedented surface specificity. The structures of these systems were altered through the control of experimental parameters including monolayer pressure, subphase temperature, pH and ionic content. Thermodynamic information about structural changes in a fatty amine monolayer's hydrophobic region was obtained by observation of the pressure and temperature dependence of the monolayer's solid to liquid phase transition. Further studies used the coordination of divalent cations to acid monolayers to perturb the water layers nearest to the film which enabled a better understanding of the water related VSFS features from these hydrophilic interfaces. Information from both the monolayer and water structure was then combined in order to examine the role of water in mediating ion-biomaterial interactions, often expressed in terms of the Hofmeister series.

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

Langmuir monolayers can be employed as simple model systems to study interactions at surfaces. Such investigations are important to fields ranging from biology to materials science. Herein, several aspects of these films and their associated water structure have been examined with vibrational sum frequency spectroscopy (VSFS). This second order nonlinear optical spectroscopy is particularly well suited for simultaneous investigations of the monolayer and the associated water structure with unprecedented surface specificity. The structures of these systems were altered through the control of experimental parameters including monolayer pressure, subphase temperature, pH and ionic content. Thermodynamic information about structural changes in a fatty amine monolayer's hydrophobic region was obtained by observation of the pressure and temperature dependence of the monolayer's solid to liquid phase transition. Further studies used the coordination of divalent cations to acid monolayers to perturb the water layers nearest to the film which enabled a better understanding of the water related VSFS features from these hydrophilic interfaces. Information from both the monolayer and water structure was then combined in order to examine the role of water in mediating ion-biomaterial interactions, often expressed in terms of the Hofmeister series.

Atmospheric corrosion indoors is of great practical importance for the degradation of metals, for example in electronics, military equipment, and cultural heritage items. It involves a wide range of chemical, electrochemical, and physical processes occurring in gas, liquid, and solid phases, and at the interfaces between them. Hence, a molecular understanding of the fundamental interactions during atmospheric corrosion is of utmost importance. Copper is one of the most used metals in electrical contacts, power generators, heat exchangers, etc. and is prone to indoor atmospheric corrosion. Although corrosion and oxidation of copper in the presence of corrosion stimulators is thermodynamically inevitable, there are ways to reduce the kinetics of corrosion and oxidation reactions. Self assembled monolayers (SAMs) of organic molecules, when adsorbed on copper surfaces, have proven to be efficient barriers against copper corrosion. However, understanding at the molecular level of the initial stages of corrosion of SAM covered copper in atmospheric corrosion conditions is lacking. The main reason is the inability of the conventional analytical methods to detect and characterize very thin corrosion products formed during the initial stages (from seconds to days) of atmospheric corrosion of SAM covered copper. To overcome this situation a highly surface sensitive technique, vibrational sum frequency spectroscopy (VSFS), has been utilized in situ and ex situ in this thesis to detect and follow the oxidation of alkanethiol SAM covered copper in dry air as well as to assess the conformational changes of SAM molecules during oxidation.  A very sensitive gravimetric method, quartz crystal microbalance with dissipation monitoring (QCM-D), and a highly sensitive and versatile optical technique, nanoplasmonic sensing (NPS), were combined in situ with VSFS to quantify this very slow oxidation process. This combination allowed the heterogeneity of the oxidation process as well as the mass and the rigidity of the corrosion products to be detected simultaneously. To address indoor atmospheric corrosion conditions where carboxylic acids play an important role we next studied the interaction between SAM covered copper and humidified air, to which formic acid was added. The in situ identification of the corrosion products and their formation kinetics was done using near surface sensitive infrared reflection/absorption spectroscopy (IRAS), and the effect of hydrocarbon chain length in alkanethiol SAMs on their corrosion protection efficiency was investigated. The effect of the anchoring group in the SAMs on their corrosion protection efficiency was studied for hexaneselenol using -SeH as the anchoring group, and the results were compared with its thiol counterpart, hexanethiol, with -SH as the anchoring group. Complementary in situ and ex situ VSFS measurements were performed to assess the quality of the SAMs before, during, and after exposure. It was shown that the SAMs of alkanethiols greatly inhibited the formation of copper (I) oxide and slowed down the formation of other corrosion products, i.e. copper formate and copper hydroxid. This was due to a selective hindrance of the corrosion stimulators, oxygen, water, and formic acid molecules reaching the copper-SAM interface. The corrosion inhibiting effect increased with the hydrocarbon chain length. The SAMs of hexaneselenols, on the other hand, exhibited an accelerated formation of copper (I) oxide, copper formate and copper hydroxide compared to an unprotected surface as a result of the partial removal of hexaneselenol molecules from the copper surface during prolonged exposure. The experience gained in characterizing and quantifying thin copper oxides was further used to explore the influence of gamma (γ) radiation on copper corrosion in anoxic water. This multi-analytical approach included IRAS, cathodic reduction, confocal Raman microscope, atomic force microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, and inductively coupled plasma - atomic emission spectroscopy. The results clearly showed that copper dissolution as well as the oxide layer thickness increase with gamma radiation under the exposure conditions. / Atmosfärisk korrosion under inomhusförhållanden är av stor praktisk betydelse på grund av dess inverkan på exempelvis vårt kulturarv i museimiljöer, tillförlitligheten hos elektronik i olika industriella sammanhang, eller militär utrustning förvarad i olika förråd. Den atmosfäriska korrosionen styrs av ett brett spektrum av kemiska, elektrokemiska och fysikaliska processer som äger rum i tre faser: atmosfären, den tunna fuktfilmen på objektytan och den fasta fasen, samt i de bägge fasgränserna mellan de tre faserna. För att kunna hitta motmedel mot korrosionen är det av yttersta vikt att öka den molekylära förståelsen för dessa processer. Koppar är en mycket använd metall i elektriska eller elektroniska komponenter, i värmeväxlare eller VVS-sammanhang, som beslag och i en rad olika dekorer. Metallen korroderar eller oxiderar spontant i många korrosiva miljöer, men det finns ett brett spektrum av metoder för att minska korrosions- eller oxidationshastigheten. Monoskikt av tätpackade självassocierande organiska molekyler (engelska: self assembled monolayers, förkortat SAM) adsorberade på kopparytan har visat sig vara effektiva barriärer för kopparkorrosion. Den molekylära insikten i dessa monoskikts funktionssätt för att minska den atmosfäriska korrosionen är dock ännu rätt så begränsad. Den främsta orsaken är oförmågan hos mer etablerade analytiska metoder att kunna karakterisera de ytterst små mängder av korrosionsprodukter som bildas under den atmosfäriska korrosionens inledande skeenden upp till några dagars exponering. Den extremt ytkänsliga och i korrosionssammanhang fortfarande relativt oprövade analysmetoden summafrekvensspektroskopi (engelska: vibrational sum frequency spectroscopy, förkortat VSFS) har därför använts för att under pågående exponering följa det mycket långsamma oxidationsförlopp som uppstår när koppar, skyddat av något organiskt monoskikt, exponeras för torr luft. VSFS har även kunnat användas för att under pågående oxidation följa strukturella förändringar hos monoskiktet. För att kvantifiera en så långsam oxidationsprocess har även en annan extremt masskänslig metod kunnat kombineras med VSFS, en kvartskristallmikrovåg med s.k. dissipationsövervakning, förkortat QCM-D. Ytterligare en i korrosionssammanhang oprövad men lika masskänslig teknik har kunnat kombineras med VSFS. Den metoden besitter än så länge bara ett engelskt namn, nanoplasmonic sensing (NPS). Kombinationen VSFS–QCM-D–NPS har utnyttjats i en serie unika försök, där inte bara de ytterst långsamma oxidationshastigheterna kunnat mätas upp, utan även andra viktiga faktorer såsom graden av heterogenitet i den bakomliggande oxidationsprocessen. För att närma sig en miljö som kan efterlikna korrosiva inomhusförhållanden har atmosfären i nästa steg befuktats och dessutom har låga halter av myrsyra tillsats. Just tillsatsen av karboxylsyror har visat sig generera korrosionsprodukter med en sammansättning som på koppar och vissa andra metaller efterliknar de som bildas under atmosfärisk korrosion inomhus. Identifiering av korrosionsprodukter och deras tillväxthastighet på koppar, skyddat av olika långa tätpackade kolkedjor med en tiolgrupp i ena ändan som binder till kopparsubstratet, har kunnat ske med infraröd reflektions-absorptionsspektroskopi (IRAS) under in situ-förhållanden. Ju längre kolvätekedjor desto större korrosionsinhibieringsförmåga kunde påvisas. När den på koppar förankrade tiolgruppen ersattes med en selenolgrupp blev korrosionsinhibieringsförmågan sämre. Kompletterande mätningar in situ och ex situ  utfördes med hjälp av VSFS för att undersöka kvaliteten på de tätpackade kolvätekedjorna, varvid kunde påvisas att graden av tätpackning hos kolkedjorna försämrades med ökad exponeringstid. Förutom den allmänna nedbromsningen av korrosionshastigheten på koppar blev sammansättningen av bildade korrosionsprodukter på oskyddat koppar en annan än på  koppar skyddat av tioler. I det förra fallet detekterades korrosionsprodukterna koppar(I)oxid, koppar(II)format och koppar(II)hydroxid, under det att ingen koppar(I)oxid påvisades på skyddat koppar, endast små mängder koppar(II)format och koppar(II)hydroxid kunde detekteras. De adsorberade kolkedjorna tycks hindra de korrosionsstimulerande molekylerna vatten, myrsyra och syrgas från att nå kopparytan lika effektivt. När de tiolförankrade kolvätekedjorna ersattes med selenolförankrade kolvätekedjor desorberades en del kolvätekedjor från kopparsubstratet vid längre exponeringstider. Resultatet blev att mängden korrosionsprodukter nu blev signifikant större än på oskyddat koppar, sannolikt på grund av galvanisk korrosion. Erfarenheterna från detta doktorsarbete vad gäller kvantifiering av små mängder kopparoxider har även utnyttjats för att undersöka inverkan av g-strålning på kopparkorrosion i rent vatten. Härvid användes ett multianalytiskt angreppssätt bestående av IRAS, katodisk reduktion, konfokal Ramanmikroskopi, atomkraftsmikroskopi, svepelektronmikroskopi, fotoelektronspektroskopi, samt analys av utlöst mängd koppar i vattenlösningen med induktivt kopplad plasmaatomemissionsspektroskopi. Resultaten visar tydligt att utlösningen av koppar, liksom det bildade oxidskiktets tjocklek, ökar med g-strålningen under rådande exponeringsförhållanden. / <p>QC 20131206</p>

Very specific protein-salt interactions are involved in a multitude of biological phenomena such as protein folding/stability, enzymatic activity, and signal transduction events. In this work, we used two very simple, protein-mimic model biopolymers to obtain a better understanding of specific cation effects operating in aqueous protein environments. The two biopolymers used were Elastin-like Polypeptides (ELPs) and poly(N-isopropylacrylamide) (PNIPAM). ELPs are an especially an ideal model system as these polypeptides can be easily genetically engineered to observe the effect of specific amino acid residues and peptide chain length on these salt interactions. Both of these biopolymers are also highly thermoresponsive as their aqueous solutions undergo a hydrophobic collapse/aggregation induced phase transition process above a lower critical solution temperature (LCST). Thermodynamic measurements of these biopolymers were carried out under various salt solution conditions. Additionally, both of these biopolymers are suitable for making surface specific spectroscopic measurements. Vibrational sum frequeny spectroscopy (VSFS), a non-linear interface sensitive spectroscopic technique, was employed here to investigate biologically relevant cation interactions which occur at peptide/protein surfaces. First, the LCST response of a non-polar ELP and a neutral biopolymer, PNIPAM, was investigated in the presence of 12 different alkali, alkaline-earth metal and transition metal chloride salts. Even though the salt interactions for uncharged proteins are dominated by anions, subtle specific cation effects were also observed. The results followed a direct Hofmeister series for cations. Most alkali cations are excluded from the polar amide regions of proteins. More polarizable cations, however, can solvate the hydrophobic moieties and somewhat counter the salting-out effect of the chloride anion. More charged and hydrated ions like lithium and divalent cations showed a weak interaction to the amide moiety through their hydration shell. The role of acidic amino acid residues in inducing cation specificities was investigated using an aspartate-rich ELP system. Both thermodynamic and spectroscopic data conclusively proved that the negative charge on protein surfaces is the main driving force for cation partitioning and specificity under physiological relevant concentration regimes. Apparent binding constants of carboxylate moieties with cations were determined. This is the first quantitative and thoroughly systematic study of such biologically relevant cation-carboxylate interactions prevalent in enzyme active sites and protein surfaces.

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

xv, 116 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Aqueous solutes next to hydrophobic interfaces arc prevalent in a multitude of chemical and biological systems throughout the world. Their presence ranges from environmental processes such as soil and water remediation to biological processes such as ion transport, membrane formation, and enzyme activity. In these and other examples, the interface is an integral part of the system. Understanding these chemically complex systems requires that a molecular level picture be built as a starting basis. In this dissertation, vibrational sum-frequency spectroscopy (VSFS), a surface selective non-linear optical technique, is used to obtain a fundamental understanding of the interfacial properties of carboxylic acid based surfactants and polymers at the oil-water interface. Interfacial studies of the solvating environment around a carboxylate headgroup surfactant are presented first. By utilizing different VSFS polarization schemes, the carboxylate vibrational stretching region was used to monitor the headgroup environment. Results showed the oil-water interface provides a unique environment for adsorption and structuring, and distinct differences exist from the air-water and solid-water interface. With the information gained in the first study, the binding of metal ions to carboxylate headgroups is investigated using VSFS. Mg 2+ , Ca 2+ , Mn 2+ , Ni 2+ , Cu 2+ , and Zn 2+ were used to perturb the headgroup vibrations to further our understanding of the types of interactions and the binding strength between the ion and headgroup. The results show each ion to have a different interaction characteristics with the strongest being bi-dentate in nature and the weakest having ionic character. The final work presented involves moving VSFS studies towards macromolccular assemblies at the oil-water interface to model inherently complex biomolecular systems. These studies present adsorption structure and dynamics of poly(acrylic-acid) as a function of pH, molecular weight, concentration, and the presence of mono and divalent salts. Poly(acrylic-acid) was found to have ordered adsorption characteristics that were highly dependent on the pH and the presence of aqueous salts. This dissertation includes unpublished co-authored materials. / Committee in charge: Thomas Dyke, Chairperson, Chemistry; Geraldine Richmond, Advisor, Chemistry; John Hardwick, Member, Chemistry; Jeffrey Cina, Member, Chemistry; 1. Andrew Berglund, Member, Chemistry; John Conery, Outside Member, Computer & Information Science

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

No description available.