Surface characterization of 316L stainless steel for biomedical applications

Stainless steel alloys play an important role in the field of biomaterials due to their exceptional corrosion resistance and biocompatibility. These alloys have the capability to enhance the quality of a human life by altering various structures of human physiology. The close proximity these alloys have with destructive body fluids, ion dissolution is a detrimental cause from the corrosion initiative and may cause unfavorable reactions. A view on developing an improved compatible surface for the human body leads to implementation of different chemical surface modifications used for creating features that must be corrosion resistant and biologically active without changing the overall bulk property. In this study, multiple technics for chemical treatments of above and below enhanced oxidation evolution will undergo a process of electropolishing and magnetoelctropolishing produced on commercial 316 L stainless steel. These surface modifications attempt to refine and improve critical features: corrosion resistance, biocompatibility, morphology, wettability, and chemistry

In situ electrochemical cells to study the oxygen evolution reaction by near ambient pressure x-ray photoelectron spectroscopy

In this contribution, we report the development of in situ electrochemical cells based on proton exchange membranes suitable for studying interfacial structural dynamics of energy materials under operation by near ambient pressure X-ray photoelectron spectroscopy. We will present both the first design of a batch-type two-electrode cell prototype and the improvements attained with a continuous flow three-electrode cell. Examples of both sputtered metal films and carbon-supported metal nanostructures are included demonstrating the high flexibility of the cells to study energy materials. Our immediate focus was on the study of the oxygen evolution reaction, however, the methods described herein can be broadly applied to reactions relevant in energy conversion and storage devices

Investigation of single, binary, and ternary metal oxides of iridium, rhodium, and palladium for neural interfacing applications

In this dissertation, thin film single, binary, and ternary metal oxides of iridium (Ir), ruthenium (Ru), rhodium (Rh), and palladium (Pd) were synthesized for use as electrode/microelectrode coatings for neural interfacing applications using DC reactive magnetron sputtering. Synthesis conditions which enhanced the electrochemical properties of films as measured by cyclic voltammetry and electrochemical impedance spectroscopy in a phosphate buffered saline solution of the single metal oxides were identified to be 30 mTorr working pressure, 20% oxygen partial pressure, and cathode power densities ≤ 4.9 W/cm2. These parameters were then used to develop the binary and ternary metal oxide films. The binary metal oxides studied included Ir(1-x)Mx where M = Pd, Rh, Ru, and the ternary metal oxides studied included Ir(1-x-z)MxMz’, where M,M´ = Pd, Rh, and Ru. The binary metal oxide concentrations which produce robust microstructures and exceptional electrochemical performance have been identified to be x ≥ 0.5 for Ir(1-x)RhxOy, x ≥ 0.34 for Ir(1-x)RuxOy, and x ≥ 0.14 for Ir(1-x)PdxOy. Similar compositional ranges have been identified for the ternary metal oxides and include x ≥ 0.16 and z ≥ 0.05 for Ir(1-x-z)PdxRuzOy, x ≥ 0.13 and z ≥ 0.04 for Ir(1-x-z)PdxRhzOy, and x ≥ 0.2 and z ≥ 0.14 for Ir(1-x-z)RuxRhzOy

Butanediols production from erythritol on Rh promoted catalyst

The C-O hydrogenolysis of Erythritol to Butanodiols was studied in aqueous solution at 473 K and 25 bar of H2 using Rh/ReOx/TiO2 and the monometallic Rh/TiO2 and ReOx/TiO2 catalysts. The solids were characterized by temperature programmed reduc-tion (TPR), TEM and XPS. TPR and XPS showed that ReOx species are close to Rh particles leading to reduction at lower temperature than Re on mono-metallic catalyst. However, some segregated Rhenium species were suspected by TPR profile for the bimetallic catalyst and detected by TEM. Re/TiO2 exhibited low activity forming only products from dehydration and epimerization. Although Rh/TiO2 showed high activity (total conversion at 14 h), was more selective to C-C cleavage leading to lower car-bon products. Rh/ReOx/TiO2, showed instead, a good activity and selectivity towards C-O hydrogenolysis route yielding 37.5% of Butanodiols. Activation en-ergy and reaction orders on ERY (0.58) and H2 (0.53) were estimated from experiences made at dif-ferent reaction conditions.Fil: Virgilio, Emanuel Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Padro, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Sad, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

The synthesis and characterization of advanced functional properties of well-defined nanoscale building blocks

Nanotechnology is the science and engineering conducted at dimensions of 1–100 nanometers, where unique phenomena enable novel applications. In the last decade, engineered nanoparticles have become an important class of new materials with several properties that make them very attractive for commercial development. This MSc research successfully accomplished the synthesis of uniform AgDeNPs, IrO2-x core shells, 3-D hematite NPs, 1-D hematite NPs and subsequent creation of thin films of hematite NPs. These nanostructures were investigated for potential applications that included sensing, catalysis, water splitting and construction of pigments. This was accomplished by synthesizing uniform NPs of defined shape and structure and size. Control over these characteristics is crucial for the NPs at the nanoscale to function efficiently for their intended applications

Nanoscale Building Blocks: Bridging the Gap between Potential and Realized Applications

The vast potential of nanoparticles and nanotechnology remains largely untapped; the crucial bottleneck being the knowledge gap between making and using nanoparticles (NPs). This PhD work bridges this gap by focusing on synthesizing nanoparticles with applications at the forefront. Four peer-reviewed publications are presented in Chapters 3-6, a safety and toxicological perspective is given in Chapter 7, and current work and future progress are summarized in Appendix 1. Bimorphic silver nanoparticles were prepared, presenting an innovative method to synthesize diverse nanostructures using polymeric surface blocking to break symmetry in seeded regrowth (Chapter 3).1 Silver stars with D5h symmetry were also synthetized using seeded regrowth and polymeric surface blocking (Chapter 4).2 Both were proven to be beneficial in sensing applications, specifically surface plasmon resonance and surface enhanced Raman spectroscopy. To mediate the chemical stability of silver, gold coating and templating was used, which was also proven beneficial for sensing applications (Chapter 5).3 Using gold as a protective coating has enabled the development of metallodielectrics with a silver decahedral core, gold coating, and metal oxide shells. The method included in this work prepares shells of MnO2-x, FeOOH, IrOx, and SiO2, with varying porosities and advantages for sensing (Chapter 6).4 Reflecting on the contributions of this work, these four accounts present rational design pathways that are transferable to different systems, enabling properties to be tailored for the desired application. This bridges the gap between potential and realized applications. (1) Cathcart, N.; Kitaev, V. Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples. Sci. Rep. 2016, 6, 32561. (2) Cathcart, N.; Coombs, N.; Gourevich, I.; Kitaev, V. Synthesis and Sensing Properties of D5h Pentagonal Silver Star Nanoparticles. Nanoscale 2016, 8, 18282–18290. (3) Cathcart, N.; Chen, J. I. L.; Kitaev, V. LSPR Tuning from 470 to 800 nm and Improved Stability of Au–Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(Styrenesulfonate). Langmuir 2018, 34, 612–621. (4) Cathcart, N.; Murshid, N.; Campbell, P.; Kitaev, V. Selective Plasmonic Sensing and Highly Ordered Metallodielectrics via Encapsulation of Plasmonic Metal Nanoparticles with Metal Oxides. ACS Appl. Nano Mater. 2018, 1, 6514–6524

Nanoscale Building Blocks: Bridging the Gap between Potential and Realized Applications

The vast potential of nanoparticles and nanotechnology remains largely untapped; the crucial bottleneck being the knowledge gap between making and using nanoparticles (NPs). This PhD work bridges this gap by focusing on synthesizing nanoparticles with applications at the forefront. Four peer-reviewed publications are presented in Chapters 3-6, a safety and toxicological perspective is given in Chapter 7, and current work and future progress are summarized in Appendix 1. Bimorphic silver nanoparticles were prepared, presenting an innovative method to synthesize diverse nanostructures using polymeric surface blocking to break symmetry in seeded regrowth (Chapter 3).1 Silver stars with D5h symmetry were also synthetized using seeded regrowth and polymeric surface blocking (Chapter 4).2 Both were proven to be beneficial in sensing applications, specifically surface plasmon resonance and surface enhanced Raman spectroscopy. To mediate the chemical stability of silver, gold coating and templating was used, which was also proven beneficial for sensing applications (Chapter 5).3 Using gold as a protective coating has enabled the development of metallodielectrics with a silver decahedral core, gold coating, and metal oxide shells. The method included in this work prepares shells of MnO2-x, FeOOH, IrOx, and SiO2, with varying porosities and advantages for sensing (Chapter 6).4 Reflecting on the contributions of this work, these four accounts present rational design pathways that are transferable to different systems, enabling properties to be tailored for the desired application. This bridges the gap between potential and realized applications. (1) Cathcart, N.; Kitaev, V. Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples. Sci. Rep. 2016, 6, 32561. (2) Cathcart, N.; Coombs, N.; Gourevich, I.; Kitaev, V. Synthesis and Sensing Properties of D5h Pentagonal Silver Star Nanoparticles. Nanoscale 2016, 8, 18282–18290. (3) Cathcart, N.; Chen, J. I. L.; Kitaev, V. LSPR Tuning from 470 to 800 nm and Improved Stability of Au–Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(Styrenesulfonate). Langmuir 2018, 34, 612–621. (4) Cathcart, N.; Murshid, N.; Campbell, P.; Kitaev, V. Selective Plasmonic Sensing and Highly Ordered Metallodielectrics via Encapsulation of Plasmonic Metal Nanoparticles with Metal Oxides. ACS Appl. Nano Mater. 2018, 1, 6514–6524

Utilizing Copper(I) Catalyzed Azide-Alkyne Huisgen 1,3-Dipolar Cycloaddition for the Surface Modification of Colloidal Particles with Electroactive and Emissive Moieties

The development of charge–transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build “better” colloidally–based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the research, the particles that were developed were found to be better suited for medical applications. Nonetheless, the global objective envisioned at the onset of this research was consistent with its final outcomes. The research tasks pursued to accomplish this global objective included: (1) The design and synthesis of electroactive moieties and their conversion into organic light emitting devices; An electron–transporting monomer was synthesized that was structurally & energetically similar to the small molecule 2–biphenyl–4–yl–5–(4–tert–butylphenyl)–1,3,4–oxadiazole (tBu–PBD). The monomer was copolymerized with 2–(9H–carbazol–9–yl)ethyl 2–methylacrylate (CE) and the resulting copolymer was utilized in OLEDs which employed fluorescent coumarin 6 (C6) or phosphorescent tris(2–phenylpyridine)iridium(III) [Ir(ppy)3] emitters. The copolymer devices exhibited a mean luminance of ca. 400 and 3,552 cd/m2 with the C6 and Ir(ppy)3 emitters, that were stable with thermal aging at temperatures ranging from 23 °C to 130 °C. Comparable poly(9–vinyl–9H–carbazole)/tBu–PBD blend devices exhibited more pronounced variations in performance with thermal aging. (2) The surface–modication of colloids with electroactive & fluorescing moieties via “click” chemistry; Aqueous–phase 83 nm poly(propargyl acrylate) (PA) nanoparticles were surface–functionalized with sparingly water soluble fluorescent moieties through a copper(I)–catalyzed azide–alkyne cycloaddition (CuAAC) (i.e., “click” transformation) to produce fluoroprobes with a large Stokes shift. For moieties which could not achieve extensive surface coverage on the particles utilizing a standard click transformation procedure, the presence of β–cyclodextrin (β–CD) during the transformation enhanced the grafting density onto the particles. For an oxadiazole containing molecule (AO), an azide–modified coumarin 6 (AD1) and a polyethylene glycol modied naphthalimide–based emitter (AD2), respectively, an 84%, 17% and 5% increase in the grafting densities were observed, when the transformation was performed in the presence of β–CD. In contrast, a carbazolyl–containing moiety (AC) exhibited a slight retardation in the final grafting density when β–CD was employed. Photoluminescence studies indicated that AC & AO when attached to the particles form an exciplex. An efficient energy transfer from the exciplex to the surface attached AD2 resulted in a total Stokes shift of 180 nm for the modified particles. (3) The synthesis and characterization of near–infrared (NIR) emitting particles for potential applications in cancer therapy. PA particles were surface modified through the “click” transformation of an azide–terminated indocyanine green (azICG), an NIR emitter, and poly(ethylene glycol) (azPEG) chains of various molecular weights. The placement of azICG onto the surface of the particles allowed for the chromophores to complex with bovine serum albumin (BSA) when dispersed in PBS that resulted in an enhancement of the dye emission. In addition, the inclusion of azPEG with the chromophores onto the particle surface resulted in a synergistic nine–fold enhancement of the fluorescence intensity, with azPEGs of increasing molecular weight amplifying the response. Preliminary photodynamic therapy (PDT) studies with human liver carcinoma cells (HepG2) combined with the modified particles indicated that a minor exposure of 780 nm radiation resulted in a statistically signicant reduction in cell growth