This study uses the ACS first-term general chemistry exam to determine if one curriculum approach is more effective in increasing student success than the other based on their performance on the ACS exam. Two chemistry curriculum approaches were evaluated in this study; the traditional curriculum (TC) and the Atoms First (AF) approach. The sample population was first-semester general chemistry students at Collin College in Frisco, TX. An independent sample t-test was used to determine if there were differences in overall performance between the two curriculum approaches on two different versions of the ACS exam. The results from this study show that AF approach may be a better alternative to the TC approach as they performed statistically significantly better on the 2005 exam version. Factor analysis was used to determine if there were differences between the two curriculum approaches by topic on the ACS exam. Eight different topics were chosen based on topics listed on the ACS Examinations Institute Website. The AF students performed better at a statistically significant level than the TC students on the topics of descriptive chemistry and periodicity, molecular structure, and stoichiometry. Item response theory was used to determine the chemistry content misconceptions held by the students …

A series of 28 square-planar dithiol(diimine)platinum(II) chromophoric complexes have been synthesized, characterized, and evaluated for potential efficacy in sensitization of solid state photovoltaic devices to the near-infrared regions of the electromagnetic spectrum. The effect of molecular stacking in the solid state and self-association in solution are shown to influence spectral, electronic, and magnetic properties of the chromophores. Such properties are investigated in the pure form and as partners in donor-acceptor charge transfer adducts. Finally, selected chromophores have been incorporated into single layer schottky diodes as neat films and as dopants in multi-layer organic photovoltaic devices. Evaluation of the devices internal quantum efficiency and voltage-current was measured as proof of concept.

The reactions of atomic hydrogen with methanethiol and that of atomic hydrogen with carbon disulfide were studied experimentally using flash-photolysis resonance-fluorescence techniques. Rate constants were determined over a range of temperatures and pressures, and through analysis and comparison to theoretical work details of the reactions were ascertained.

Nonlinear organic liquids that exhibit two-photon absorption (TPA) function as good optical limiters for sensor protection from laser pulses. L34 (4-butyl-4'-propyl-diphenylethyne) is a liquid organic compound exhibiting nonlinear optical absorption. A thiol- derivatized analog of L34 (“thiol-L34”) was prepared to bind the molecules to the surface of gold nanoparticles. Surface binding is necessary to investigate synergy between nonlinear optical absorption of gold nanoparticles and thiol-L34. Thiol-L34 was prepared in a six-step organic synthesis starting from 3-(4-bromophenyl) propionic acid. Au nanoparticles with <15 nm diameter have been prepared and sensitized with the thiol-L34 compound for assessment of their nonlinear optical behavior. Diazolylmethenes a class of metal-coordinating dyes that are similar to dipyrrins with some substitutions of nitrogen atoms in place of carbon atoms. Modification in the framework of dipyrrinoid dyes via this replacement of nitrogen for carbon atoms may lead to compounds that serve as effective agents for bioimaging and/or photodynamic therapy. Several routes to the synthesis of di-(1,2,3)-triazolylmethenes, di-(1,2,4)-triazolylmethenes, and ditetrazolylmethenes are presented.

The reaction of 1-(diphenylphosphino)-2-(diphenylphosphito)benzene (PP*) and Os3(CO)10(ACN) has been investigated. A combined experimental and computational study on the isomerization of 1,2-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (A) and 1,1-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (B) and reversible ortho-metalation exhibited by the triosmium cluster B are reported. The subsequent conversion of cluster B to the hydrido cluster HOs3(CO)9[μ-1,2-PhP(C6H4-η1)C6H4P(OPh)2] (E) and the benzyne-substituted cluster HOs3(CO)8(µ3-C6H4)[μ-1,2-PhP(C6H4)P(OPh)2] (N) has been established. All of these new clusters have been isolated and fully characterized in solution by IR and NMR spectroscopy; in addition, X-ray diffraction analyses have been performed on the clusters A, B, J, and N. The ortho-metalation reaction that gives cluster E is shown to be reversible, and the mechanism has been probed using selectively deuterated PP* isotopomers. Kinetic and thermodynamic isotope data, in conjunction with DFT calculations, are presented that support the existence of an intermediate unsaturated cluster in the ortho-metalation reaction. Due to interest in the coordination chemistry of formamidines, the non-symmetric amidine ligands PhNC(Me)NHPri, PhNC(Et)NHPri, and (2,4,6-Me3C6H2)NC(Me)NHPri, have been synthesized, and their reaction with Os3(CO)10(MeCN)2 has been investigated. Of the twelve new clusters prepared in section, seven have been structurally characterized by X-ray crystallography.

This is my thesis research on the preparation of borylazadipyrromethene (azaBODIPY) dyes bearing an anchoring group, such as a carboxylic acid group, at the β-pyrrolic position of the azadipyrromethene scaffold. Carboxylate groups form covalent bonds to oxide semiconductors such as TiO2 (n-type) or Cu2O (p-type) in dye-sensitized solar cells (DSCs) or photogalvanic dye-sensitized solar cells (P-DSCs). Oxide-binding azaBODIPY dyes can be used to investigate the rate and mechanism of electron injection from the dyes to the semiconductors. Two different types of azaBODIPY (difluoroboryl and dialkynylboryl) were prepared by following previously developed methods. To convert difluoroborylazaBODIPY to the final dyes having a carboxylic acid in the β-pyrrolic position, several distinct synthetic routes were designed, adopting various reactions, such as halogenation, Sonogashira coupling, Knoevenagel condensation, Grignard reagents, Vilsmeir-Haack, and Steglich esterification. Some of these reactions were successful, but the overall synthesis to the targeted final molecule couldn’t be accomplished. Even though further studies on the synthesis of oxide-binding azaBODIPYs are needed, at least my thesis research suggests what reactions can be implemented to complete this synthesis in the future. Proton NMR (nuclear magnetic resonance) and carbon NMR were commonly used to confirm the synthesized compounds, and sometimes crystallographic information was obtained by …

The effects of direct plasma chemistries on carbon removal from silicon nitride (SiNx) and oxynitride (SiOxNy ) surfaces and Cu have been studied by x-photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O2,NH3 and He capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiNx) and Silicon oxynitride (SiOxNy ) surfaces. O2plasma and He plasma treatment results in the formation of silica overlayer. In contrast, the exposure to NH3 plasma results in negligible additional oxidation of the SiNx and SiOxNy surface. Ex-situ contact angle measurements show that SiNx and SiOxNy surfaces when exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH3 plasma and He plasma, indicating that the O2 plasma-induced SiO2 overlayer is highly reactive towards ambient corresponding to increased roughness measured by AFM. At longer ambient exposures (>~10 hours), however surfaces treated by either O2, He or NH3 plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in the contact angle upon the exposure to ambient. The results suggest a practical route to enhancing …

Experimental data for the logarithm of the gas-to-ionic liquid partition coefficient (log K) have been compiled from the published literature for over 40 ionic liquids over a wide temperature range. Temperature independent correlations based on the Gibbs free energy equation utilizing known Abraham solvation model parameters have been derived for the prediction of log K for 12 ionic liquids to within a standard deviation of 0.114 log units over a temperature range of over 60 K. Temperature independent log K correlations have also been derived from correlations of molar enthalpies of solvation and molar entropies of solvation, each within standard deviations of 4.044 kJ mol-1 and 5.338 J mol-1 K-1, respectively. In addition, molar enthalpies of solvation and molar entropies of solvation can be predicted from the Abraham coefficients in the temperature independent log K correlations to within similar standard deviations. Temperature independent, ion specific coefficients have been determined for 26 cations and 15 anions for the prediction of log K over a temperature range of at least 60 K to within a standard deviation of 0.159 log units.

Organic dyes are examined in photoelectrochemical systems wherein they engage in thermal (rather than photoexcited) electron donation into metal oxide semiconductors. These studies are intended to elucidate fundamental parameters of electron transfer in photoelectrochemical cells. Development of novel methods for the structure/property tuning of electroactive dyes and the preparation of nanostructured semiconductors have also been discovered in the course of the presented work. Acceptor sensitized polymer oxide solar cell devices were assembled and the impact of the acceptor dyes were studied. The optoelectronic tuning of boron-chelated azadipyrromethene dyes has been explored by the substitution of carbon substituents in place of fluoride atoms at boron. Stability of singlet exited state and level of reduction potential of these series of aza-BODIPY coumpounds were studied in order to employ them as electron-accepting sensitizers in solid state dye sensitized solar cells.

The new nickel/layered silicate nanocomposites were electrodeposited from different pHs to study the influence on the metal ions/layered silicate plating solution and on the properties of the deposited films. Nickel/layered silicate nanocomposites were fabricated from citrate bath atacidic pHs (1.6−3.0), from Watts’ type solution (pH ~4-5), and from citrate bath at basic pH (~9). Additionally, the new nickel/molybdenum/layered silicate nanocomposites were electrodeposited from citrate bath at pH 9.5. The silicate, montmorillonite (MMT), was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The preferred crystalline orientation and the crystalline size of nickel, nickel/layered silicate, nickel/molybdenum, and nickel/molybdenum/layered silicate films were examined by X-ray diffraction. The microstructure of the coatings and the surface roughness was investigated by scanning electron microscopy and atomic force microscopy. Nickel/molybdenum/layered silicate nanocomposites containing low content of layered silicate (1.0 g/L) had increase 32 % hardness and 22 % Young’s modulus values over the pure nickel/molybdenum alloy films. The potentiodynamic polarization and electrochemical impedance measurements showed that the nickel/molybdenum/layered silicate nanocomposite layers have higher corrosion resistance in 3.5% NaCl compared to the pure alloy …

In this work, copper bimetallic corrosion and inhibition in ultra large scale interconnect fabrication process is explored. Corrosion behavior of physical vapor deposited (PVD) copper on ruthenium on acidic and alkaline solutions was investigated with and without organic inhibitors. Bimetallic corrosion screening experiments were carried out to determine the corrosion rate. Potentiodynamic polarization experiments yielded information on the galvanic couples and also corrosion rates. XPS and FTIR surface analysis gave important information pertaining inhibition mechanism of organic inhibitors. Interestingly copper in contact with ruthenium in cleaning solution led to increased corrosion rate compared to copper in contact with tantalum. On the other hand when cobalt was in contact with copper, cobalt corroded and copper did not. We ascribe this phenomenon to the difference in the standard reduction potentials of the two metals in contact and in such a case a less noble metal will be corroded. The effects of plasma etch gases such as CF4, CF4+O2, C4F8, CH2F2 and SF6 on copper bimetallic corrosion was investigated too in alkaline solution. It was revealed that the type of etching gas plasma chemistry used in Cu interconnect manufacturing process creates copper surface modification which affects corrosion behavior in alkaline solution. The learning …

Soft-landing ion mobility has applicability in a variety of areas. The ability to produce material and collect a sufficient amount for further analysis and applications is the key goal of this technique. Soft-landing ion mobility has provided a way to deposit material in a controllable fashion, and can be tailored to specific applications. Changing the conditions at which soft-landing ion mobility occurs effects the characteristics of the resulting particles (size, distribution/coverage on the surface). Longer deposition times generated more material on the surface; however, higher pressures increased material loss due to diffusion. Larger particles were landed when using higher pressures, and increased laser energy at ablation. The utilization of this technique for the deposition of silver clusters has provided a solvent free matrix application technique for MALDI-MS. The low kinetic energy of incident ions along with the solvent free nature of soft-landing ion mobility lead to a technique capable of imaging sensitive samples and low mass analysis. The lack of significant interference as seen by traditional organic matrices is avoided with the use of metallic particles, providing a major enhancement in the ability to analyze low mass compounds by MALDI.

Graphene receives enormous attention owing to its distinctive physical and chemical prosperities. Growing and transferring graphene to different substrates have been investigated. The graphene growing on the copper substrate has an advantage of low solubility of carbon on the copper which allow us to grow mostly monolayer graphene. Graphene sheet of few centimeters can be transferred to 300nm silicon oxide and quartz crystal pre-deposited with metal like Cu and Ru. Characterization of the graphene has been done with Raman and contact angle measurement and recently quartz crystal microbalance (QCM) has been employed. The underpotential deposition (UPD) process of Bi on Ru metal surface is studied using electrochemical quartz crystal microbalance (EQCM) and XPS techniques. Both Bi UPD and Bi bulk deposition are clearly observed on Ru in 1mM Bi (NO3)3/0.5M H2SO4. Bi monolayer coverage calculated from mass (MLMass) and from charge (MLCharge) were compared with respect to the potential scanning rates, anions and ambient controls. EQCM results indicate that Bi UPD on Ru is mostly scan rate independent but exhibits interesting difference at the slower scan. Bi UPD monolayer coverage calculated from cathodic frequency change (ΔfCathodic) is significantly smaller than the monolayer coverage derived from integrated charge under the cathodic …

The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. …