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Incorporating Electrochemistry and X-ray Diffraction Experiments Into an Undergraduate Instrumental Analysis Course

Description: Experiments were designed for an undergraduate instrumental analysis laboratory course, two in X-ray diffraction and two in electrochemistry. Those techniques were chosen due their underrepresentation in the Journal of Chemical Education. Paint samples (experiment 1) and pennies (experiment 2) were characterized using x-ray diffraction to teach students how to identify different metals and compounds in a sample. in the third experiment, copper from a penny was used to perform stripping analyses at different deposition times. As the deposition time increases, the current of the stripping peak also increases. the area under the stripping peak gives the number of coulombs passed, which allows students to calculate the mass of copper deposited on the electrode surface. the fourth experiment was on the effects of variable scan rates on a chemical system. This type of experiment gives valuable mechanistic information about the chemical system being studied.
Date: May 2012
Creator: Molina, Cathy
Partner: UNT Libraries

Preparation and characterization of praseodymium oxide films and powders.

Description: Nanocrystalline praseodymium oxide films have been successfully generated on stainless steel substrates. The electrochemical deposition was performed in the cathode compartment of a divided electrochemical cell with a regular three-electrode configuration. The green films obtained by electrodeposition were then annealed at high temperatures for 1-3 hours. X-ray diffraction revealed the fluorite structure of Pr6O11 and the crystallite size was calculated. X-ray photoelectron spectroscopy was employed to study the composition of the oxide films and also the oxidation state of Pr. Scanning electron microscopy was utilized to study the surface texture and microstructure of deposits. Fourier transform infrared spectrometery was used to investigate the composition of the films. The effects of different conditions on the green films were also studied such as different pH values of the electrolyte solution, different deposition modes, different supporting electrolytes and different applied current densities. Sintering experiments were conducted to investigate the properties of the green films. Praseodymium oxide powders were also successfully prepared by combining electrochemical methods with sintering processes. The praseodymium oxide powders were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The crystallite sizes of the powders were evaluated.
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Date: May 2004
Creator: Shang, Yajuan
Partner: UNT Libraries

Molecular Structure Analyses of Asymmetric Hydrocarbon Liquid Compounds in the Gas Phase Using Chirped-pulse Fourier Transform Microwave Spectroscopy: Acyl Chlorides and Perfluorinated Acyl Chlorides

Description: Examinations of the effects of (a.) alkyl carbon chain length and (b.) perfluorination of acyl chlorides; propionyl chloride, butyryl chloride, valeroyl chloride, and perfluorinated acyl chlorides; perfluoropropionyl chloride and perfluorobutyryl chloride, are reported and compared using CP-FTMW spectroscopy. All of these molecules are already published in various journals except for valeroyl chloride. The chapters are organized by molecule alkyl chain length and include some background theory. Conformational stability, internal rotation, helicity, and ionic character of the C-Cl bond via the nuclear electric quadrupole coupling constant (χzz) are analyzed. Results show syn, syn-anti/syn-gauche, and syn-anti-anti/syn-gauche-anti stable conformations. Internal rotation was only seen in propionyl chloride. Helicity was not observed. (χzz) was observed to be inert to alkyl chain length, ~ 60 MHz and ~ 65 MHz for the nonfluorinated and fluorinated acyl chlorides. Partial fluorination and varying functional groups are recommended.
Date: August 2011
Creator: Powoski, Robert A.
Partner: UNT Libraries

Experimental Determination of L, Ostwald Solubility Solute Descriptor for Illegal Drugs By Gas Chromatography and Analysis By the Abraham Model

Description: The experiment successfully established the mathematical correlations between the logarithm of retention time of illegal drugs with GC system and the solute descriptor L from the Abraham model. the experiment used the method of Gas Chromatography to analyze the samples of illegal drugs and obtain the retention time of each one. Using the Abraham model to calculate and analyze the sorption coefficient of illegal drugs is an effective way to estimate the drugs. Comparison of the experimental data and calculated data shows that the Abraham linear free energy relationship (LFER) model predicts retention behavior reasonably well for most compounds. It can calculate the solute descriptors of illegal drugs from the retention time of GC system. However, the illegal drugs chosen for this experiment were not all ideal for GC analysis. HPLC is the optimal instrument and will be used for future work. HPLC analysis of the illegal drug compounds will allow for the determination of all the solute descriptors allowing one to predict the illegal drugs behavior in various Abraham biological and medical equations. the results can be applied to predict the properties in biological and medical research which the data is difficult to measure. the Abraham model will predict more accurate results by increasing the samples with effective functional groups.
Date: May 2012
Creator: Wang, Zhouxing
Partner: UNT Libraries

Characterization of Ionic Liquid As a Charge Carrier for the Detection of Neutral Organometallic Complexes Using Electrospray Ionization Mass Spectrometry

Description: A novel application of ionic liquid as a charge carrier for the analysis and detection of neutral organometallic complexes using a mass spectrometer has been presented. The mass spectrometer detects only charged compounds which raise a difficulty in analyzing a neutral molecule that lacks a basic site to associate with charge. Therefore, an effective way of providing charge has always been an area of keen interest in the field of mass spectrometry. Ionic liquids have a very fascinating property of forming a cation-? interaction with other molecules to give a charged complex. In order to take advantage of this, it is important to know the geometric structure of the complex. Advanced methodologies like hydrogen-deuterium exchange and computational calculations have been used assisting in better understanding of the structure of the ionic liquid complexes.
Date: August 2012
Creator: Joshi, Ubisha
Partner: UNT Libraries

Copper Electrodeposition on Iridium, Ruthenium and Its Conductive Oxide Substrate

Description: The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. The results show that the Cl- , SO42- , Br- will affect the position of stripping bulk peak and stripping UPD peak: the stripping bulk peak will shift and decrease if the concentration of halide ions is increasing, and the monolayer of UPD will increase at the same time.
Date: December 2003
Creator: Huang, Long
Partner: UNT Libraries

Explorations with optically active, cage-annulated crown ethers.

Description: A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these crown ethers to recognize the enantiomers of guest salts, i.e., (+) a-methyl benzylamine and to transport them enantioselectively in W-tube transport experiments were studied. The ability of these crown ethers to perform as chiral catalysts in an enantioselective Michael addition was studied. The extent of asymmetric induction, expressed in terms of the enantiomeric excess (%ee), was monitored by measuring the optical rotation of the product and comparing to the literature value.
Date: May 2003
Creator: Ji, Mingzhe
Partner: UNT Libraries

Improvement of Homogeneity and Adhesion of Diamond-Like Carbon Films on Copper Substrates

Description: Electrodeposition method is used to deposit diamond-like carbon (DLC) films on copper substrates via anodic oxidation at low temperature. These films are characterized using Raman spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. Homogeneity of these films is studied using Raman spectroscopy and scanning electron microscopy. Scotch tape peel tests indicate adherent film on copper substrate. Carbon phase transformation is studied using thermal annealing experiments in conjunction with Raman spectroscopy and scanning electron microscopy. A cathodic electrochemical method is also studied to deposit diamond-like carbon films on copper substrates. However, films deposited by the cathodic route have poor adhesion and quality compared to anodically deposited films. It is also possible to grow diamond phase on copper substrates using acetylene in liquid ammonia via electrodeposition route. An electrochemical method is proposed for boron doping into DLC films.
Date: August 2004
Creator: Vavilala, Suma
Partner: UNT Libraries

Study of Copper Electrodeposition on Ruthenium Oxide Surfaces and Bimetallic Corrosion of Copper/Ruthenium in Gallic Acid Solution

Description: Ruthenium, proposed as a new candidate of diffusion barrier, has three different kinds of oxides, which are native oxide, electrochemical reversible oxide and electrochemical irreversible oxide. Native oxide was formed by naturally exposed to air. Electrochemical reversible oxide was formed at lower anodic potential region, and irreversible oxides were formed at higher anodic potential region. In this study, we were focusing on the effect of copper electrodeposition on each type of oxides. From decreased charge of anodic stripping peaks and underpotential deposition (UPD) waves in cyclic voltammetry (CV), efficiency of Cu deposition dropped off indicating that interfacial binding strength between Cu and Ru oxides was weakened when the Ru surface was covered with irreversible oxide and native oxide. Also, Cu UPD was hindered by both O2 and H2 plasma modified Ru surfaces because the binding strength between Cu and Ru was weakened by O2 and H2 plasma treatment. Cu/Ru and Cu/Ta bimetallic corrosion was studied for understanding the corrosion behavior between diffusion barrier (Ta and Ru) and Cu interconnects under the post chemical mechanical planarization (CMP) process in semiconductor fabrication. Gallic acid is used in post CMP slurry solution and is known well as antioxidant which is supposed to oxidize itself to prevent other species from oxidizing. However, in this study under the observation of Cu microdot corrosion test, copper was corroded only in gallic acid at specific pH region of alkaline condition which is close to the pH region for post CMP solution formula. With different pH alkaline condition, gallic acid formed different oxidized products which are characterized by cyclic voltammetry and UV-Vis spectroscopy. Therefore, the specific oxidized product from particular pH region condition caused the Cu corrosion. Also, the corrosion rate of Cu microdots was influenced by substrate effect (Cu/Ru and Cu/Ta) and ambient control, which was included ...
Date: August 2007
Creator: Yu, Kyle K.
Partner: UNT Libraries

Effects of Web-based Instruction in High School Chemistry.

Description: The intent of this study is to identify correlations that might exist between Web-based instruction and higher assessment scores in secondary education. The study framework was held within the confines of a public high school chemistry classroom. Within this population there were students identified as gifted and talented (GT) as well as those without this designation. These two classifications were examined for statistically higher assessment scores using a two-tailed t-test. Results indicated that females outperformed males on pre- and post- instructional unit tests. All subgroups improved their logical-thinking skills and exhibited positive attitudes towards Web-based instruction. In general, Web-based instruction proved beneficial to improving classroom performance of all GT and non-GT groups as compared to traditional classroom instruction.
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Date: May 2003
Creator: Stratton, Eric W.
Partner: UNT Libraries

The Performance of Silicon Based Sensor and its Application in Silver Toxicity Studies

Description: The silicon based sensor is able to detect part per trillion ionic silver in 0.0098% hydrofluoric acid based on the open circuit potential (OCP) measurement. The OCP jump of 100 ppt ionic silver solution is up to 120 mV. The complex agent can effectively suppress the ionic silver concentration and suppress the OCP signal. The ability of complex agent to suppress the OCP signal depends on the formation constant of the complex with silver. The complex adsorbed on the sensor surface induces a second OCP jump, the height of the second jump depends on the formation constant of the complex. The MINEQL chemical equilibrium modeling program is used to calculate the ionic silver concentration when complex agent presents, a discrepancy is found between the MINEQL simulation result and the OCP signal of the silicon based sensor. The toxicity of ionic silver to C. dubia is studied parallel to the OCP signal of silicon based sensor. Less toxicity is found when the complex agent is present similar to the OCP signal. Another discrepancy is found between the MINEQL simulation and the toxicity test when MINEQL simulation is used to predict and control the ionic silver concentration. The data from both biosensor C. dubia and silicon based sensor support each other and both are not in agreement with MINEQL simulation prediction.
Date: August 2000
Creator: Peng, Haiqing
Partner: UNT Libraries

Forensic Analysis of Ink on Documents Using Direct Analyte-Probed Nanoextraction Coupled Techniques

Description: Analzying questioned documents in a nondestructive nature has been an issue for the forensic science community. Using nondestructive techniques such as video spectral comparator does not give reliable information due to the variations in gray or color levels that are distinguished differently by analysts. Destructive techniques such as chromatography give dependable, qualitative and quantitative, information but involves altering the evidentiary value of these questioned documents. The paradox of document examination becomes a problem when document evidence is involved, especially when trying to preserve its evidentiary value and critical data is needed. Thus, a nondestructive technique has been developed to solve the loopholes in document examinations. Direct analyte-probed nanoextraction (DAPNe) is a nanomanipulation technique that extracts ink directly off the document for further examination. A watermark is left, at most, post-extraction. DAPNe utilizes a tip emitter, pre-filled with a solvent, which is controlled in x-, y-, and z-coordinates via joystick controller and aspirates/extracts using a pressure injector. The versatility of this technique lies within the solvent chemistry and its capability to be coupled to various types of instrumentation. The extraction solvent can be altered to target specific components in the ink. For example, a chelator may be added to target metal ions found in ancient inks or methanol may be added to target certain organic resins and binding agents found in modern inks. In this study, DAPNe has been coupled to nanospray ionization mass spectrometry, fluorescence microscopy, Raman spectroscopy, matrix-assisted laser desorption ionization mass spectrometry, and laser ablation to solve questioned document concerns in the area of falsified or forged documents, redacted documents, and aging studies.
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Date: May 2016
Creator: Huynh, Vivian
Partner: UNT Libraries

A Study of Silver: an Alternative Maldi Matrix for Low Weight Compounds and Mass Spectrometry Imaging

Description: 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.
Date: May 2014
Creator: Walton, Barbara Lynn
Partner: UNT Libraries

Chemistry, Detection, and Control of Metals during Silicon Processing

Description: This dissertation focuses on the chemistry, detection, and control of metals and metal contaminants during manufacturing of integrated circuits (ICs) on silicon wafers. Chapter 1 begins with an overview of IC manufacturing, including discussion of the common aqueous cleaning solutions, metallization processes, and analytical techniques that will be investigated in subsequent chapters. Chapter 2 covers initial investigations into the chemistry of the SC2 clean - a mixture of HCl, H2O2, and DI water - especially on the behavior of H2O2 in this solution and the impact of HCl concentration on metal removal from particle addition to silicon oxide surfaces. Chapter 3 includes a more generalized investigation of the chemistry of metal ions in solution and how they react with the silicon oxide surfaces they are brought into contact with, concluding with illumination of the fundamental chemical principles that govern their behavior. Chapter 4 shows how metal contaminants behave on silicon wafers when subjected to the high temperature (≥ 800 °C) thermal cycles that are encountered in IC manufacturing. It demonstrates that knowledge of some fundamental thermodynamic properties of the metals allow accurate prediction of what will happen to a metal during these processes. Chapter 5 covers a very different but related aspect of metal contamination control, which is the effectiveness of metal diffusion barriers (e.g. Ru) in holding a metal of interest, (e.g. Cu), where it is wanted while preventing it from migrating to places where it is not wanted on the silicon wafer. Chapter 6 concludes with an overview of the general chemical principles that have been found to govern the behavior of metals during IC manufacturing processes.
Date: May 2005
Creator: Hurd, Trace Q.
Partner: UNT Libraries

Interfacial Study of Copper Electrodeposition with the Electrochemical Quartz Crystal Microbalance (EQCM)

Description: The electrochemical quartz crystal microbalance (EQCM) has been proven an effective mean of monitoring up to nano-scale mass changes related to electrode potential variations at its surface. The principles of operation are based on the converse piezoelectric response of quartz crystals to mass variations on the crystal surface. In this work, principles and operations of the EQCM and piezo-electrodes are discussed. A conductive oxide, ruthenium oxide (RuO2) is a promising material to be used as a diffusion barrier for metal interconnects. Characterization of copper underpotential deposition (UPD) on ruthenium and RuO2 electrodes by means of electrochemical methods and other spectroscopic methods is presented. Copper electrodeposition in platinum and ruthenium substrates is investigated at pH values higher than zero. In pH=5 solutions, the rise in local pH caused by the reduction of oxygen leads to the formation of a precipitate, characterized as posnjakite or basic copper sulfate by means of X-ray electron spectroscopy and X-ray diffraction. The mechanism of formation is studied by means of the EQCM, presenting this technique as a powerful in-situ sensing device.
Date: May 2005
Creator: Ojeda Mota, Oscar Ulises
Partner: UNT Libraries

Metal Oxide Reactions in Complex Environments: High Electric Fields and Pressures above Ultrahigh Vacuum

Description: Metal oxide reactions at metal oxide surfaces or at metal-metal oxide interfaces are of exceptional significance in areas such as catalysis, micro- and nanoelectronics, chemical sensors, and catalysis. Such reactions are frequently complicated by the presence of high electric fields and/or H2O-containing environments. The focus of this research was to understand (1) the iron oxide growth mechanism on Fe(111) at 300 K and 500 K together with the effect of high electric fields on these iron oxide films, and (2) the growth of alumina films on two faces of Ni3Al single crystal and the interaction of the resulting films with water vapor under non-UHV conditions. These studies were conducted with AES, LEED, and STM. XPS was also employed in the second study. Oxidation of Fe(111) at 300 K resulted in the formation of Fe2O3 and Fe3O4. The substrate is uniformly covered with an oxide film with relatively small oxide islands, i.e. 5-15 nm in width. At 500 K, Fe3O4 is the predominant oxide phase formed, and the growth of oxide is not uniform, but occurs as large islands (100 - 300 nm in width) interspersed with patches of uncovered substrate. Under the stress of STM induced high electric fields, dielectric breakdown of the iron oxide films formed at 300 K occurs at a critical bias voltage of 3.8 ± 0.5 V at varying field strengths. No reproducible result was obtained from the high field stress studies of the iron oxide formed at 500 K. Ni3Al(110) and Ni3Al(111) were oxidized at 900 K and 300 K, respectively. Annealing at 1100 K was required to order the alumina films in both cases. The results demonstrate that the structure of the 7 Å alumina films on Ni3Al(110) is k-like, which is in good agreement with the DFT calculations. Al2O3/Ni3Al(111) (γ'-phase) and Al2O3/Ni3Al(110) (κ-phase) ...
Date: August 2005
Creator: Qin, Feili
Partner: UNT Libraries

Study of Ruthenium and Ruthenium Oxide's Electrochemical Properties and Application as a Copper Diffusion Barrier

Description: As a very promising material of copper diffusion barrier for next generation microelectronics, Ru has already obtained a considerable attention recently. In this dissertation, we investigated ruthenium and ruthenium oxide electrochemical properties and the application as a copper diffusion barrier. Cu under potential deposition (UPD) on the RuOx formed electrochemically was first observed. Strong binding interaction, manifesting by the observed Cu UPD process, exists between Cu and Ru as well as its conductive ruthenium oxide. Since UPD can be conformally formed on the electrode surface, which enable Ru and RuOx has a potential application in the next generation anode. The [Cl-] and pH dependent experiment were conducted, both of them will affect UPD Cu on Ru oxide. We also found the Cu deposition is thermodynamically favored on RuOx formed electrochemically. We have studied the Ru thin film (5nm) as a copper diffusion barrier. It can successfully block Cu diffusion annealed at 300 oC for 10min under vacuum, and fail at 450 oC. We think the silicidation process at the interface between Ru and Si. PVD Cu/Ru/Si and ECP Cu/Ru/Si were compared each other during copper diffusion study. It was observed that ECP Cu is easy to diffuse through Ru barrier. The function of RuOx in diffusion study on Cu/Ru/Si stack was discussed. In pH 5 Cu2+ solution, Ru and Pt electrochemical behavior were investigated. A sharp difference was observed compared to low pH value. The mechanism in pH 5 Cu2+ solution was interpreted. An interesting compound (posnjakite) was obtained during the electrochemical process. An appropriate formation mechanism was proposed. Also Cu2O was formed in the process. We found oxygen reduction reaction is a key factor to cause this phenomenon.
Date: August 2005
Creator: Zhang, Yibin
Partner: UNT Libraries

Layered Double Hydroxides as Anion- and Cation-Exchanging Materials

Description: Layered double hydroxides (LDH) have been principally known as anion-exchanging, clay-like materials for several decades, and continues to be the main driving force for current and future research. The chemical interactions of LDH, with transition metallocyanides, have been a popular topic of investigation for many years, partly due to the use of powder x-ray diffraction and infrared spectroscopy as the main characterization tools. Each transition metallocyanide has a characteristic infrared stretching frequency that can be easily observed, and their respective sizes can be observed while intercalated within the interlayer of the LDH. The ability of LDH to incorporate metal cations or any ions/molecules/complexes, that have a postive charge, have not been previously investigated, mainly due to the chemical and physical nature of LDH. The possibility of cationic incorporation with LDH would most likely occur by surface adsorption, lattice metal replacement, or by intercalation into the LDH interlayers. Although infrared spectroscopy finds it main use through the identification of the anions incorporated with LDH, it can also be used to study and identify the various active and inactive bending and stretching modes that the metal hydroxide layers have.
Date: May 2007
Creator: Richardson, Mickey Charles
Partner: UNT Libraries