Peter Majewski

Functionalized Magnetite Nanoparticles—Synthesis, Properties, and Bio-Applications

Nanotechnology has generated tremendous hopes in recent years toward the design of advanced functional materials, especially in the bio-medical field. Nano-sized-materials such as magnetite nanoparticles display indeed fascinating physico-chemical properties that, if tuned properly, can be exploited to design new bio-diagnostic and therapeutic strategies as well as innovative biotechnology methodologies. Owing to their biocompatibility and excellent magnetic properties, magnetite nanocrystals have been the object of a tremendous amount of research in the last decade and numerous (bio)applications have been reported. Importantly, advances in the synthesis of magnetite nanoparticles enable excellent control over their size, shape, and composition. Despite these remarkable progresses, many issues remain to be overcome for these nanotechnology products to revolution the medical practice. The fine control and application of colloidal nanostructures such as magnetite nanoparticles in complex biological systems remains especially challenging. This article attempts to review the current status of magnetite nanoparticles preparation and use, with a special emphasis on bio-medical applications, but also to outline the promises and challenges associated to this emerging technology.

Materials aspects of the high-temperature superconductors in the system Bi2O3–SrO–CaO–CuO

Ten years after the discovery of high-T c superconductivity in the system Bi–Sr–Ca–Cu–O, the superconducting compounds have been identified, and their structures, crystal chemistry, phase equilibria, and properties have been extensively investigated. In this review, the results of studies of crystal chemistry and phase equilibria are presented to give materials scientists a comprehensive insight into the phase equilibria and crystal chemistry of these challenging materials.

Hydrophobic plasma polymer coated silica particles for petroleum hydrocarbon removal.

In recent years, functionalized hydrophobic materials have attracted considerable interest as oil removal agents. This investigation has applied plasma polymerization as a novel method to develop hydrophobic and oleophilic particles for water purification. 1,7-Octadiene was plasma polymerized onto silica particles using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerized 1,7-octadiene (ppOD) films were deposited using plasma power of 40 W and monomer flow rate of 2 sccm, while polymerization time was varied from 5 to 60 min. The surface chemistry of ppOD coated particles was investigated via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy, while Washburn capillary rise measurements were applied to evaluate the hydrophobicity and oleophilicity of the particles. The effectiveness of ppOD coated particles for the removal of hydrophobic matter from water was demonstrated by adsorption of motor oil, kerosene, and crude oil. Petroleum hydrocarbon removal was examined by varying removal time and particle mass. The morphology of oil-loaded ppOD coated particles was examined via environmental scanning electron microscopy observations. Increasing the polymerization time increased the concentration of hydrocarbon functionalities on the surface, thus also increasing the hydrophobicity and oil removal efficiency (ORE). The ppOD coated particles have shown to have excellent ORE. These particles were capable of removing 99.0-99.5% of high viscosity motor oil in 10 min, while more than 99.5% of low viscosity crude oil and kerosene was adsorbed in less than 30 s. Plasma polymerization has shown to be a promising approach to produce a new class of materials for a fast, facile, and efficient oil removal.

Processing of (La, Sr)(Ga, Mg)O3 solid electrolyte

The preparation of La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) powders by the mixed oxide route requires significantly longer annealing times of about 60 h compared to the combustion synthesis and Pechini method which requires less than 6 h. In comparison to the mixed oxide route the soft chemical synthesis methods produce significantly smaller grain sizes after solid-state reactive sintering, which is due to the significantly shorter annealing times in order to achieve well crystallized ceramics. It is emphasized that at 1400°C in air single phase LSGM samples with the composition La0.8Sr0.2Ga0.8Mg0.2O3 could be prepared neither by the mixed oxide route nor the combustion synthesis or the Pechini method, but only at higher temperatures, for example 1500°C. Taking the results of the dilatometric studies for processing of LSGM ceramics into account, it is obviously that sinter temperatures of above 1300°C in air are required in order to prepare dense LSGM ceramics.

Phase diagram studies in the systems La2O3–SrO–MgO–Ga2O3 at 1350–1400°C in air with emphasis on Sr and Mg substituted LaGaO3

Abstract The ternary systems La 2 O 3 –SrO–Ga 2 O 3 , La 2 O 3 –MgO–Ga 2 O 3 , and the quaternary system La 2 O 3 –SrO–Ga 2 O 3 –MgO were studied at 1350–1400°C in air with emphasis on the solid solubility of Sr and Mg in LaGaO 3 . In both ternary systems the solid solubility of Sr substituting for La and that of Mg substituting for Ga, respectively, is rather small. However, when Sr and Mg are present simultaneously, the solid solubility of Sr and Mg in LaGaO 3 increases significantly. In addition, several phases of the quaternary system exhibit a pronounced variation of their La:Sr ratio and a high solid solubility of Mg, as for example LaSrGa 3 O 7 and LaSrGaO 4 . The structure LaGaO 3 containing Sr and Mg has been determined to be orthorhombic, space group Pbnm , a =5.53443 A, b =5.49523 A, and c =7.78320 A. In the quaternary system, extended four phase regions exist between LaGaO 3 , MgO and the La–Sr–Ga–O compounds. Quaternary phases were not observed.

Elastomeric composites based on carbon nanomaterials

Carbon nanomaterials including carbon black (CB), carbon nanotubes (CNTs) and graphene have attracted increasingly more interest in academia due to their fascinating properties. These nanomaterials can significantly improve the mechanical, electrical, thermal, barrier, and flame retardant properties of elastomers. The improvements are dependent on the molecular nature of the matrix, the intrinsic property, geometry and dispersion of the fillers, and the interface between the matrix and the fillers. In this article, we briefly described the fabrication processes of elastomer composites, illuminated the importance of keeping fillers at nanoscale in matrices, and critically reviewed the recent development of the elastomeric composites by incorporating CB, CNTs, and graphene and its derivatives. Attention has been paid to the mechanical properties and electrical and thermal conductivity. Challenges and further research are discussed at the end of the article.

Plasma Polymer-Functionalized Silica Particles for Heavy Metals Removal

Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

Rapid synthesis of the Bi-2212 phase by a polymer matrix method

A method that leads to the Bi-2212 phase after a short thermal treatment of metal acetates is presented. The thermal treatment consists in a calcination (2 h at + 2 h at ), pressing and sintering (1 or 3 h at ). TGA and DTA provide valuable data about the decomposition of the polymer and metal - polymer complex and the formation and decomposition of the carbonates in the intermediate compounds. In contrast with the most common sol - gel methods, the use of polyethylenimine yields relatively large particles (ca ).

The Pb solubility of the Bi-based high-Tc superconductors “Bi2Sr2CaCu2O8” and “Bi2Sr2Ca2Cu3O10” as a function of temperature

Abstract The Pb solubility of the 2212 and 2223 phase has been determined as a function of the temperature, and phase relations within the quasiquinary system Bi 2 O 3 -PbO-SrO-CaO-CuO with emphasis on the high-temperature superconducting compounds 2212 and 2223 have been obtained. The Pb solubility exhibits a distinct maximum at about 860°C and 840°C for the 2212 and 2223 phase, respectively. With increasing and decreasing temperature the Pb content of both phase decreases resulting in a charge of the content of the superconducting phases. The Pb content of the 2223 phase has no influence on the T c of the phase.

Phase diagram studies in the system Ag-“Bi2Sr2CaCu2O8”

Abstract The phase relations in the system of Ag and the high-temperature superconducting phase “Bi 2 Sr 2 CaCu 2 O 8 ” (2212) are studied up to a Ag content of 50 mol percent in air. The most significant observation is that the temperature of the complete melting of 2212 decreases significantly from about 895°C to some 865°C with increasing Ag content. Therefore, at constant sinter temperature between 895°C and 865°C the amount of liquid in the sample depends significantly on the Ag concentration.