State of the Surface of Antibacterial Copper in Phosphate Buffered Saline

The state was investigated of the copper surface in phosphate buffered saline (PBS; 140 mM Cl-, 10 mM phosphate; pH 7) by a combination of cyclic voltammetry (CV) and chronoamperometry (CA) with in situ spectroscopic ellipsometry and Raman spectroscopy. After polarization, samples were analyzed ex situ. In agreement with expectations on the basis of the Pourbaix diagram, Cu2O and Cu4O3 were observed when polarizing the system above approximate to-0.05 V vs. Ag vertical bar AgCl vertical bar 3M KCl. The formation of Cu2O did not lead to a passivation of the system. Rather, the system dissolved under formation of soluble square planar CuCl42-, identified by its strong Raman peak approximate to 300 cm(-1). During dissolution, spectroscopic ellipsometry showed a film with a stable steady state thickness. Energy electron loss spectroscopy (EELS) analysis of a cross section of the oxide after removal from the electrolyte showed that the oxide was Cu2O. It is suggested that Cl-replaces oxygen vacancies in the oxide layer. As soon as oxidation to Cu-II becomes dominant, the dissolution proceeds to soluble CuII species. The outer surface of copper under these conditions is hence a Cu2O-like surface, with CuII complexes present in solution. (C) The Author(s) 2017. Published by ECS. All rights reserved

State of the Surface of Antibacterial Copper in Phosphate Buffered Saline

The state was investigated of the copper surface in phosphate buffered saline (PBS; 140 mM Cl-, 10 mM phosphate; pH 7) by a combination of cyclic voltammetry (CV) and chronoamperometry (CA) with in situ spectroscopic ellipsometry and Raman spectroscopy. After polarization, samples were analyzed ex situ. In agreement with expectations on the basis of the Pourbaix diagram, Cu2O and Cu4O3 were observed when polarizing the system above approximate to-0.05 V vs. Ag vertical bar AgCl vertical bar 3M KCl. The formation of Cu2O did not lead to a passivation of the system. Rather, the system dissolved under formation of soluble square planar CuCl42-, identified by its strong Raman peak approximate to 300 cm(-1). During dissolution, spectroscopic ellipsometry showed a film with a stable steady state thickness. Energy electron loss spectroscopy (EELS) analysis of a cross section of the oxide after removal from the electrolyte showed that the oxide was Cu2O. It is suggested that Cl-replaces oxygen vacancies in the oxide layer. As soon as oxidation to Cu-II becomes dominant, the dissolution proceeds to soluble CuII species. The outer surface of copper under these conditions is hence a Cu2O-like surface, with CuII complexes present in solution. (C) The Author(s) 2017. Published by ECS. All rights reserved

Production Of Fenico Alloy Nano Particles With Ultrasonic Spray Pyrolysis And Hydrogen Reduction (usp-hr) Method

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Manyetik nanopartiküller ferroakışkanlar, manyetik malzemeler, katalizör, tıbbi teşhiş ürünleri ve yüksek yoğunluğa sahip manyetik veri depolama cihazları gibi önemli uygulama alanlarına sahiptir ve bu yüzden son yıllarda, manyetik nano partiküllerin üretimi üzerine çalışmalar hız kazanmıştır. Günümüzde daha çok bilgiyi çok daha küçük alanlara depolamak hedeflenmektedir. Bu nedenle son yıllarda literatürde konu üzerine yapılan çalışmalar NiFe ikili alaşımlarına alternatif olarak daha yüksek doyurma akış yoğunluğu ve daha düşük manyetik enerjiyi koruyabilirlilik değerlerine sahip CoNiFe gibi yeni yumuşak manyetik malzemeler üretmeyi konu kalmaktadır. Bu araştırmaların yanı sıra FeNiCo alaşım nanopartiküllerinin yakıt pillerinde katalizör olarak ve ferromanyetik karaktere sahip olmaları sebebiyle kanser tanı ve tedavisinde kullanımı yoğun araştırılmaktadır. Ancak yapılan çalışmalar incelendiğinde FeNiCo alaşım nanopartiküllerinin ultrasonik sprey piroliz ve hidrojen redüksiyonu yöntemi (USP-HR) ile üretimi üzerine çalışma bulunmadığı tespit edilmiştir. Yapılan çalışmalarda bu nano yapılı malzemeleri üretmek için kullanılan tekniklerin iki veya daha aşamalı olduğu, katkı ajanları kullanıldığı dolayısıyla ekonomik olmadığı görülmektedir. Bu tez çalışmasında; FeNiCo üçlü alaşım nanopartiküllerinin yüksek safiyetteki tuzlarından hareketle USP-HR tekniği ile üretimi, üretim koşullarının optimizasyonunu ve manyetik özelliklerinin araştırılmasını hedeflenmiştir. Bu amaçla araştırma faaliyetlerinin ilk aşamasını FeNiCo alaşım nanopartiküllerinin üretim parametrelerinin belirlenmesi oluşturmaktadır. Başlangıç malzemesi olarak kullanılacak olan yüksek safiyetteki metal tuzlarından farklı konsantrasyonlarda çözeltiler (0,05-0,4 M) hazırlanarak USP-HR tekniği ile FeNiCo alaşım nano partiküllerinin üretilmesi gerçekleştirilmiştir. FeNiCo nano partiküllerinin üretiminde; çözelti konsantrasyonu ve redüksiyon sıcaklığı gibi farklı parametreler incelenerek optimum üretim koşulları belirlenmiştir. Üretilen nano partiküllerin karakterizasyon çalışmalarında; boyut, morfoloji, kristal yapı ve kristal boyutu gibi partikül özelliklerinin üretim parametrelerine bağlı olarak değişimi araştırılmıştır.X-ışınları ile faz analizi yapılmış FeNiCo nanopartiküllerinin yapısının FCC ve BCC yapının karışımından oluştuğu belirlenmiştir. Taramalı elektron mikroskopu (SEM) ile morfoloji ve boyut analizi gerçekleştirilmiş ve çözelti konsantrasyonun 0,4 M’dan 0,05 M’a azalması ile alaşım partiküllerinin ortalama boyutunun 695 nm’den 280 nm’ye düştüğü gözlemlenmiştir. FeNiCo alaşım partiküllerinin manyetik analizi oda sıcaklığında titreşimli numune magnetometresi (VSM) kullanılarak belirlenmiştir. 0,1 M konsantrasyona sahip başlangıç çözeltisinden 600°C’de üretilen partiküllerin koersivite değeri 48.24 Oe , aynı koşullarda 1000°C redüksiyon sıcaklığında üretilen partiküllerin koersivite değeri 11.15 Oe bulunmuştur.Binary and ternary alloy ferromagnetic nanoparticles have gained great attention because of their modified magnetic and catalytic properties comparing with monometallic nanoparticles as a result, many kinds of compositions including Fe, Ni, and Co such as FeNi and FeCo, CoNi and FeNiCo have been investigated during recent years. FeNiCo ternary alloys have had many important applications not only due to their remarkable magnetic properties, but also because of their suitable catalytic properties. Using nanoparticles of FeNiCo ternary alloys or coatings of FeNiCo are widely investigated since it is known that FeNiCo nanoparticles have good soft magnetic features. In addition to this, using as excellent catalysts for hydrogen generation and synthesis of carbon nanotubes are some of their catalytic applications. Therefore scienctist has been working on the production of FeNiCo ternary alloy nanoparticles for magnetic recording media and catalyst application. The production and production techniques of these alloys are really significant both in industry and in scientific researches because of these important applications. Therefore production of FeNiCo ternary alloy nanoparticles in a simple and single step process is a significant field to investigate the magnetic and catalytic properties . Our previos papers present the production of nanocrystalline particles of FeNi, FeCo with ultrasonic spray pyrolysis method which is a simple and single method and found that the nanoparticles of these binary alloys can be successfully prepared with uniform particle size and desired compositions. The main goal of this study is that production of nanostructured FeNiCo ternary alloy particles with USP-HR method and optimization of the production parameters. FeNiCo nanoparticles are generally used as soft magnet materials and their technological application has a significant role in the electronic industry. Affect of the precursor and temperature will be examined to production and optimization of the production process. Crystallite size, chemical composition, crystal structure, morphology, size and size distribution of particles will be studied. Characterization of FeNiCo nanoparticles will be carried on parallel with the production of particles. The crystallite sizes were calculated by Scherer formula using XRD data. The chemical compositions of particles were analyzed by the energy dispersive spectroscopy (EDS) instrument. Particle size and morphology of the samples were investigated by field emission scanning electron microscopy (FE-SEM, JEOL JSM 700F). In this step, optimization of the production parameters will be determined. After characterization of general properties of particles, optimum parameters for production process will be determined. Then, the magnetic properties of samples will be measured by Vibrating Sample Magnetometer. The magnetic hysteresis loop measurements will be carried at room temperature with an applied magnetic field up to 20,000 Oe. The coercive force of the samples will be derived from the magnetic hysteresis loop. Temperature and concentration dependence of Hc of the samples will be examined by taking this test. Potential application area of the particles will be specified after magnetic characterization.Yüksek LisansM.Sc

Preparation and magnetic characterization of Fe/metal oxide nanocomposite particles by means of hydrogen reduction assisted ultrasonic spray pyrolysis (USP-HR)

Fe/metal oxide nanocomposite particles were produced by means of hydrogen reduction assisted ultrasonic spray pyrolysis. Fe/Fe0.761Mg0.2390O and Fe/MgO nanocomposite particles were obtained at 600 and 800 degrees C, respectively. The thermodynamics of the formation reactions were investigated. Increasing the reaction temperature allowed efficient reduction of the precursor to metallic iron that induces the formation of pure MgO phase. The crystallite sizes of the Fe in the composite structures slightly increased, and also the crystallite sizes of the oxides decreased with elevating temperature. The nanocomposite particles exhibited spherical morphology and their particle sizes were slightly different. All of the samples showed ferromagnetic characteristics and the results indicate that the amount of metal and metal oxide phases most affected the saturation magnetizations of the composite particles which were lower than pure iron

Electrochemical Performance of (MgCoNiZn)(1-x)LixO High-Entropy Oxides in Lithium-Ion Batteries

High-entropy oxides (HEOs), which are a new class of single-phase solid solution materials, have recently attracted significant attention as an anode material for lithium-ion batteries (LIBs). In this study, (MgCoNiZn)(1-x)LixO (x = 0.05, 0.15, 0.25, and 0.35) HEOs were synthesized and their electrochemical performances as the anode material were observed in LIBs. X-ray photoelectron spectroscopy (XPS) analysis showed that the increase in the lithium cation concentration causes generation of more oxygen vacancies, which greatly affected the electrochemical performance of (MgCoNiZn)(1-x)LixO HEO anodes, in the structure. The more the oxygen vacancy concentration in the anode, the higher the discharge capacity in the LIB. The (MgCoNiZn)(0.65)Li0.35O anode had 1930 mA h g(-1) initial and 610 mA h g(-1) stable (after 130 cycles) discharge capacities at a current density of 1000 mA g(-1). This work clearly indicated that designing a HEO with abundant oxygen vacancies in the structure was a very efficient strategy to improve the electrochemical performance of the HEO electrode for LIBs

Synthesis, structural and magnetic characterization of soft magnetic nanocrystalline ternary FeNiCo particles

The present study focuses on the synthesis, microstructural and magnetic properties of ternary FeNiCo nanoparticles. Nanocrystalline ternary FeNiCo particles were synthesized via hydrogen reduction assisted ultrasonic spray pyrolysis method in single step. The effect of precursor concentration on the morphology and the size of particles was investigated. The syntheses were performed at 800 degrees C. Structure, morphology and magnetic properties of the as-prepared products were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. Scherer calculation revealed that crystallite size of the ternary particles ranged between 36 and 60 nm. SEM and TEM investigations showed that the particle size was strongly influenced by the precursor concentration and Fe, Ni, Co elemental composition of individual particles was homogeneous. Finally, the soft magnetic properties of the particles were observed to be a function of their size

Preparation and magnetic characterization of Fe/metal oxide nanocomposite particles by means of hydrogen reduction assisted ultrasonic spray pyrolysis (USP-HR)

Fe/metal oxide nanocomposite particles were produced by means of hydrogen reduction assisted ultrasonic spray pyrolysis. Fe/Fe0.761Mg0.2390O and Fe/MgO nanocomposite particles were obtained at 600 and 800 degrees C, respectively. The thermodynamics of the formation reactions were investigated. Increasing the reaction temperature allowed efficient reduction of the precursor to metallic iron that induces the formation of pure MgO phase. The crystallite sizes of the Fe in the composite structures slightly increased, and also the crystallite sizes of the oxides decreased with elevating temperature. The nanocomposite particles exhibited spherical morphology and their particle sizes were slightly different. All of the samples showed ferromagnetic characteristics and the results indicate that the amount of metal and metal oxide phases most affected the saturation magnetizations of the composite particles which were lower than pure iron

A new look at oxide formation at the copper/electrolyte interface by in situ spectroscopies

The widely used engineering material copper is a prototype of an electrochemically passive metal. In this work, the passive films on evaporated copper in 0.1 M NaOH are investigated in situ and operando by spectroscopic ellipsometry and Raman spectroscopy, both conducted during oxidation in potentiostatic step experiments. Oxide growth is initiated by jumping from a potential at which the surface is oxide-free to -0.1 V vs. Ag vertical bar AgCl vertical bar 3 M KCl (+0.11 V vs. standard hydrogen electrode, SHE). At subsequent electrode potential jumps, no corresponding jumps in the thickness are observed; instead, oxide growth proceeds steadily. Above +0.3 V vs. Ag vertical bar AgCl vertical bar 3 M KCl (+0.51 V vs. SHE), the oxide layer thickness remains constant at approximate to 7 nm. Raman spectra show a peak at 530 cm(-1), which agrees with the dominant peak in spectra of copper mixed oxide, Cu4O3 ((Cu2Cu2O3)-Cu-I-O-II). Crystalline Cu4O3 nucleates from a precursor state showing strong photoluminescence (PL), which hints at the involvement of Cu2O. Overall, the PL spectra of the growing oxide and absorption spectra indicate the presence of Cu2O in the thin films. Absorption spectra cannot be understood as a superposition of the spectra from different well-described copper oxides, which points to defect-rich oxides that show rather different spectra. Raman spectra also point to an involvement of both crystalline and amorphous oxides that coexist. The results show that the passive layers on copper are more complex than the duplex layers described in the literature; they do contain an oxide with a mixed valency of copper

In situ and operando observation of surface oxides during oxygen evolution reaction on copper

Formation and dissolution of oxide on copper under transpassive conditions, i.e. during OER and transpassive dissolution, in alkaline electrolyte was investigated by a combination of electrochemical techniques and in situ and operando Raman and photoluminescence (PL) spectroscopy, as well as spectropscopic ellipsometry. Experiments were conducted under potentiodynamic and potentiostatic polarisation in 0.1M NaOH. In chronoamperometry experiments with steps between potentials, oxide thickness continued increasing beyond the onset of OER. The thickness dropped significantly from >10 nm to <5 nm approximate to 400 mV above the OER onset. The presence of CuO, Cu2O and Cu4O3 was observed by Raman spectroscopy after the onset of OER. Correlating with the thickness drop, strong PL was observed at 1.55 eV, indicating the formation of singly charged oxygen vacancies V-O(+), following the classical PL spectrum interpretation from the literature. PL observation speaks against vacancy pair coalescence as mechanism of dissolution. After electrochemical experiments, the films were n-type semiconductors, not p-type conductors as expected for copper oxides. Results indicate that transpassive dissolution may be triggered by the instability of the oxide with respect to defect formation. (C) 2017 Elsevier Ltd. All rights reserved

Multi-Foulant-Resistant Material Design by Matching Coating-Fluid Optical Properties

The buildup of corrosion deposits, known as fouling, seriously hinders large-scale energy production. From nuclear power plants to geothermal reservoirs, fouling increases system pressure drops, impedes heat transfer, and accelerates corrosion, leading to derating and early failure. Here, we investigate the collodial interactions between multiple foulants and coated surfaces, with the aim of discovering principles for minimizing the adhesion of foulants to them. We hypothesize that matching the full refractive index spectrum of a coating to its surrounding fluid minimizes the adhesion of all foulants entrained within and that the Lifshitz theory is sufficient to predict which materials will be multi-foulant-resistant. First-principle calculations of Hamaker constants and refractive indices of six foulants on six coatings in water correlate well to direct measurements of adhesion by atomic force microscopy (AFM)-based force spectroscopy. Amorphous 2% fluorine-doped tin oxide, crystalline SiO2, CaF, and Na(3)AIF(6), which all nearly match the refractive index spectrum of water, successfully resisted adhesion of six diverse foulant materials in aqueous AFM measurements. The validation of this design principle may be expanded to design multi-fouling-resistant coatings for any system in which van der Waals forces are the dominant adhesion mechanism