Krzysztof Fitzner

Corrosion resistance of Ti and Ti–Pd alloy in phosphate buffered saline solutions with and without H2O2 addition

Abstract Corrosion resistance of pure titanium (Grade 2) and Ti-Pd alloy (Grade 7) was studied using the electrochemical techniques of potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). Measurements were performed at the temperature of 36.6 °C in two solutions: PBS solution with pH of 7.4 simulating conditions of healthy human body, and PBS solution with pH of 5.2 and with the addition of hydrogen peroxide (0.015 mol/L) simulating the inflammatory state. It is found that, Ti Grade 7 can be a good candidate as a material for orthopedic implant application, because its corrosion resistance in the PBS solution containing H 2 O 2 is better (lower corrosion current densities) than that of pure titanium.

Tissue distribution of gold nanoparticles after single intravenous administration in mice

BACKGROUND Nanoparticles (a part of matter which size is less than 100 nm) have numerous potential applications in biomedicine, due to their unique surface, electronic and optical properties. The goal of the present study was to examine the distribution of gold nanoparticles (GNPs) in mice after single intravenous administration. METHODS Spherical GNPs were synthesized by chemical reduction of tetrachloroauric acid with ascorbic acid as a reductant. GNPs were stabilized using polyvinyl alcohol (PVA, m.w. = 67000Da) a substance approved for use in the pharmaceutical industry. The size of colloidal gold particles (diameter equals 25 ± 8 nm) was determined using HR SEM and DLS techniques; ζ potential of GNPs was determined using Malvern Zetasizer Nano ZS and it equals -5.2 ± 5.4 mV. An aqueous dispersion of GNPs was administered to mice in a dose of about 10 cm(3)/kg and 24 h later the amount of gold in different organs was determined using the inductively coupled plasma mass spectrometer (ICP MS). Initial concentration of GNPs equals 29.55 mg/l. RESULTS GNPs after single intravenous administration preferentially accumulated in the liver (12.7% of the applied dose), while the other organs accumulated around 0.1% or less. CONCLUSION Colloidal GNPs of the used size (about 25 ± 8 nm) provide new potential route for direct delivery system to the liver, which may be important e.g., in liver cancer diagnosis.

The use of experimental thermodynamic data in the phase equilibria verification

Abstract This presentation summarises shortly the following experimental techniques: emf with liquid and solid electrolytes, vapour pressure measurements and calorimetric studies in application to metallic alloys. It is shown that usually one experimental technique is not sufficient for a reliable separation of the Gibbs energy into appropriate entropy and enthalpy contributions, which is necessary if one seeks the correlation between thermodynamic properties and phase equilibria. Critical assessment of the data available from different sources must be performed to get the proper thermodynamic information. Several specific examples will be analysed for systems with the miscibility gap and with intermetallic compounds to demonstrate this point of view. In some cases the correlation will be extended on the physical properties of alloys as well as the structure. There are, however, some cases for which new experimental data are still needed to clarify the phase equilibria. Two examples from the field of calorimetry and emf measurements will be discussed to show how thermodynamic information must be coupled with the phase diagram investigations to obtain proper results: • Calorimetric measurements . Results obtained in Cu–As and Ge–As systems will be shown and compared with existing binary phase diagrams. New data on the enthalpy of formation of solid and liquid Ge–As alloys let the description of the thermodynamic representation of the binary system be improved and express some doubts about the shape of the Ge–As phase diagram. • emf studies . Results of electrochemical measurements with solid CaF 2 electrolytes on Yb–Ba–Cu–O systems are analysed. This example indicates how emf results can be misinterpreted if simultaneous investigations of phase equilibria are not conducted.

Kinetics of SrSO4 reduction with CO

Abstract It has been found that the process of SrSO4 reduction with CO results in SrS formation. Increasing the oxygen content of the reducing gas by adding CO2 results in SrCO3 formation. Using a 5% CO + 95% CO2 mixture, SrCO3 was formed during experiments conducted in the temperature range 1240–1420 K. This process was controlled by nucleation and growth with an activation energy of 115 ± 10 kJ mol−1. Application of a 10% CO + 90% N2 gas mixture resulted in SrS formation. In this case, two stages of the reduction process were distinguished, the first connected with the nucleation and growth and the second apparently controlled by diffusion. Values of the activation energy for both processes are given.

Catalytic Properties of Platinum Nanoparticles Obtained in a Single Step Simultaneous Reduction of Pt(IV) Ions and Graphene Oxide

A composite material consisting of metallic platinum nanoparticles and reduced graphene oxide was successfully obtained in microflow reactor. Moreover, subnanometric platinum particles were observed. Reduced graphene oxide plays an important role as a stabilizing agent for platinum nanoparticles. Reduced graphene oxide coverage and platinum particle size as well as size distribution depend mainly on initial concentration of platinum(IV) ions. High level of reduced graphene oxide coverage by platinum nanoparticles (PtNPs) was obtained and is equal to 71%. This in turn effects significantly the mass ratio of reduced graphene oxide to PtNPs which is equal to 49% (w/w). Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis of the obtained materials were performed. Also, catalytic properties of the obtained composite material consisting of PtNPs at reduced graphene oxide surface, towards electrochemical glucose oxidation, were investigated. It was found that the studied materials exhibit high catalytic activity for glucose electro-oxidation process.

EXAFS Studies on the Reaction of Gold (III) Chloride Complex Ions with Sodium Hydroxide and Glucose

EXAFS and QEXAFS experiments were carried out at Hasylab laboratory in DESY center (X1 beamline, Hamburg, Germany) to monitor the course of the hydrolysis reactions of [AuCl(4)](-) complex ions as well as their reduction using glucose. As a result, changes in the spectra of [AuCl(4)](-) ions and disappearance of absorption Au-L(3) edge were registered. From the results of the experiments we have carried out, the changes in bond lengths between Au(3+) central ion and Cl(-) ligands as well as the reduction of Au(3+) to metallic form (colloidal gold was formed in the system) are evident. Good quality spectra obtained before and after the reactions gave a chance to determine the bond length characteristic of Au-Cl, Au-OH and Au-Au pairs. Additionally, the obtained results were compared with the simulated spectra of different gold (III) complex ions, possibly present in the solution. Finally, the mechanism of these reactions was suggested. Unfortunately, it was not possible to detect the changes in the structure of gold (III) complex ions within the time of reaction, because of too high rates of both processes (hydrolysis and reduction) as compared with the detection time.

Thermodynamic properties of liquid silver–indium–antimony alloys determined from e.m.f. measurements

Abstract The thermodynamic properties of liquid Ag–Sb–In alloys were determined using solid oxide galvanic cells with zirconia electrolyte. The following galvanic cells were employed: (I) Re + kanthal, Ag x − Sb ( 1 − x − y ) , In 2 O 3 / / ZrO 2 + ( Y 2 O 3 ) / / Ni O , Ni , Pt in the temperature range from 973 to 1200K. Thermodynamic properties of the liquid phase were described by the Redlich–Kister–Muggianu formula and the phase relations in the ternary system were calculated. The results of the calculations were compared with experimental data available from different literature sources.

Electromotive Force Measurements in High-Temperature Systems

Stability of phases existing in chemical systems is determined by its Gibbs free energy designated as G. The relative position of Gibbs free energy surfaces in the G–T–X (composition) space determines stability ranges of respective phases yielding a map called the phase diagram. Since the knowledge of phase equilibria is essential in designing new materials, determination of Gibbs free energy for respective phases is being continued on both theoretical as well as experimental ways. While in principle chemical potentials of pure substances are needed to derive Gibbs free energy of formation of the stoichiometric phases, it is not the case for the phase ( solid or liquid) with variable composition. As an example, in Fig 1, Gm for three different systems is shown. Fig.1a shows free energy of formation of the intermetallic, stoichiometric Mg2Si phase recalculated per one mole of atoms (Turkdogan, 1980). Fig1b illustrates Gibbs energy of formation of one mole of liquid In-Pb solution (Hultgren, 1973). Finally, Fig.1c demonstrates Gibbs energy of formation of the solid phase, wustite ( ‘FeO’) (Spencer & Kubaschewski, 1978).

Kinetic Studies of Gold Nanoparticles Formation in the Batch and in the Flow Microreactor System

In this study, synthesis of gold nanoparticles (Au NP’s) in the batch and flow reacting systems was carried out either in the presence or in the absence of PVA (polyvinyl alcohol) used as stabilizing agent. As the reductant of gold(III) chloride complex ions, the ascorbic acid was used. To determine the rate equation of the reduction process, the kinetic measurments based on spectrophotometry UV-Vis and DLS were carried out. Consequently, the rate equations of gold(III) complex ions reduction and Au NP’s formation were determined. To synthesize gold nanoparticles in the flow microreactor system the cartridge with T–type geometry of microchannels was used. Next, to calculate the parameters of the flow which enable precipitation of the gold clusters, obtained kinetic equations were applied. This type of microreactor, as well as different reagents flow rates, gave us the chance to inject Au NP’s stabilizer (PVA) at the proper instant of time. It was found that applied method is promising one for the preparation of gold nanoparticles with well defined shape (spheres) and with narrow size distribution (98 % of the Au NP’s with diameter ranged from 1 to 3 nm). Morphology of obtained Au NP’s was characterized using DLS and TEM.

Kinetic Studies of Gold Recovery from Diluted Chloride Aqueous Solutions Using Activated Carbon Organosorb 10 CO

The kinetic studies of gold(iii) chloride complex ions recovery from acidic solution using activated carbon (AC) were carried out using spectrophotometry. AC samples were characterized in terms of surface area, porosity, and zeta potential. The surface functional groups were also identified. It was found that adsorption of AuCl4– onto AC was followed by reduction of the ions to the metallic form. The process obeyed the first order reaction model, but the reaction was controlled by diffusion. Arrhenius and Eyring–Polanyi equations were used for determination of the activation parameters. Distribution of gold across the AC pellets was also determined and discussed according to the porous material theory.