Dariusz Łukowiec

A Structure and Morphology of Nanocomposites Composed of Carbon Nanotubes with a Varying Fraction of Platinum Nanoparticles

A structure of nanocomposite materials consisting of carbon nanotubes with a varying fraction of platinum nanoparticles (5, 10 and 20 wt %) is compared in the paper. High-quality CNTs obtained in the CVD process, 100-200 mm long with a standard deviation of below 20% and with a diameter of 10-20 nm, with a standard deviation of below 30%, were used in the research. Raw CNTs did not contain metallic impurities or amorphous carbon deposits. An indirect method of bonding the earlier produced platinum nanoparticles to the surface of functionalised carbon nanotubes was employed to deposit platinum nanoparticles onto the surface of carbon nanotubes. A full array of changes in the loading of carbon nanotubes’ surface with platinum nanoparticles was achieved as a result of the experiments performed, starting with homogenous deposition to the clearly developed large agglomerations of platinum nanoparticles. The studies carried out using scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and X-ray structural analysis have confirmed differences in the morphology, homogeneity and density of coating the carbon nanotubes’ surface with variedly concentrated platinum nanoparticles. Differences were also revealed in the structure of the newly formed nanocomposites. A nanocomposite with a 5% fraction of platinum nanoparticles demonstrates the best structure-related properties for the materials obtained.

Drug delivery via anion exchange of salicylate decorating poly(meth)acrylates based on a pharmaceutical ionic liquid

Amphiphilic polymer carriers were designed for the delivery of ionically bonded drugs. The ionic liquid, trimethylammonium methacrylate monomer, containing biologically active salicylate anions was selected for the preparation of copolymers via atom transfer radical polymerization (ATRP) with methyl methacrylate (MMA) or methyl acrylate (MA). The resulting polymers varied in the content and arrangement of ionic units in the chain. The self-assembly of polymers in aqueous solution yielded particles at critical micelle concentration (CMC) values below 0.1 mg ml−1 and with hydrodynamic diameters in the range of 170–290 nm, which were also visualized by TEM. Drug release studies indicated the exchange of 42–52% of salicylate anions with phosphate anions using dialysis in PBS, which corresponded to 0.15–0.25 mg of salicylate released from 1 mg of polymeric carrier.

Structure of Nanocomposites Based on Carbon Nanotubes Decorated with Platinum Nanoparticles

A structure and morphology of the fabricated nanocomposite materials composed of carbon nanotubes and platinum nanoparticles is reported in the paper. High quality CNTs obtained in the CVD process with a long of 100-200 mm and diameter of 10-20 nm were used in the research. Raw CNTs did not contain metallic impurities or amorphous carbon deposits. An indirect method of bonding the earlier produced platinum nanoparticles to the surface of functionalised carbon nanotubes was used to produce carbon nanotubes – platinum nanoparticles system. The main aim of current research was structure and morphology investigation of obtained nanocomposite using Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and X-ray structure analysis (XRD).

Electrical Conduction Mechanism and Dielectric Properties of Spherical Shaped Fe3O4 Nanoparticles Synthesized by Co-Precipitation Method

On the basis of dielectric measurements performed in a wide temperature range (173–373 K), a comprehensive analysis of the dielectric and electrical properties of magnetite nanoparticles electrical conduction mechanism of compressed spherical shaped Fe3O4 nanoparticles was proposed. The electrical conductivity of Fe3O4 nanoparticles was related to two different mechanisms (correlated barrier hopping and non-overlapping small polaron tunneling mechanisms); the transition between them was smooth. Additionally, role of grains and grain boundaries with charge carrier mobility and with observed hopping mechanism was described in detail. It has been confirmed that conductivity dispersion (as a function of frequencies) is closely related to both the long-range mobility (conduction mechanism associated with grain boundaries) and to the short-range mobility (conduction mechanism associated with grains). Calculated electron mobility increases with temperature, which is related to the decreasing value of hopping energy for the tunneling of small polarons. The opposite scenario was observed for the value of electron hopping energy.

Rare earth-doped lead titanate zirconate grown on carbon fibers by microwave-assisted hydrothermal synthesis

This study aimed to develop a flexible carbon fiber/oxide layer coating composite with improved electrical properties for use in electronic devices. For this, lead titanate zirconate, cerium-doped lead titanate zirconate, and yttrium-doped lead titanate zirconate were grown on carbon fibers via microwaves-assisted hydrothermal synthesis. The performed synthesis presented advantages when compared to conventional routes used in nanoparticles obtention since it allows the morphological control even at low temperatures. Carbon fiber was selected as substrates due to their thermal stability, excellent mechanical properties, chemical characteristics that allow the creation of functional groups on their surface, and good microwave radiation absorption. The composites were investigated by X-ray diffraction, spectroscopy Raman, and field emission scanning electron microscopy. The electrochemical evaluations were made by four-point probe method, cyclic voltammetry, and electrochemical impedance spectroscopy. The syntheses were successful and the carbon fiber coated with lead zirconate titanate had promissory results, with a boost in the electrical conductivity and better capacitance behavior when compared to the undoped carbon fiber, showing to be a good alternative for applications in electrical devices.

The structure and formation mechanism of FeS2/Fe3S4/S8 nanocomposite synthesized using spherical shaped Fe3O4 nanoparticles as the precursor

Abstract Synthesis of a nanocomposite containing iron sulfides and sulfur was carried out in ethylene glycol. Spherical-shaped Fe3O4 nanoparticles were used as the precursor. The structure of the FeS2/Fe3S4/S8 nanocomposite, as well as the mechanism of formation, are described with X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. Strong interaction between sulfur and oxygen was confirmed. Formation of the FeS2/Fe3S4/S8 nanocomposite was associated with the reaction between Fe3O4 and H2S, and the reaction between greigite and H2S produced by the decomposition of thioacetamide. Highly crystalline pyrite was formed in these reactions, while the sulfur and greigite appearing on the edges formed a highly disordered structure.

Modified halloysite nanoclay as a vehicle for sustained drug delivery

This paper presents the effect of modified halloysite nanotubes on the sustained drug release mechanisms of sodium salicylate. Acid treatment and composite polymer-halloysite modification techniques were adopted in this study. After each modification, sodium salicylate drug was loaded, and in vitro release properties were evaluated and compared with the raw unmodified halloysite nanotubes. The results obtained from SEM, TEM and FTIR analyses indicate that both acid treatment and composite formation have no effect on the tubular structure and morphology of halloysite. However, modification of the halloysite nanotubes did influence the drug release rate. In the acid treatment modification, there was an improved loading of sodium salicylate drug which resulted in the sustain release of large amount of the sodium salicylate. In the polymer/halloysite composite formation, a consistent layer of polymer was formed around the halloysite during the composite formation and thus delayed release providing sustained release of sodium salicylate drug over a longer period of time as compared to the acid treated and unmodified halloysite. The results from the invitro release were best fitted with the Higuchi and the Koresymer-Peppas models.

Silver nanoparticles synthesized by UV-irradiation method using chloramine T as modifier: structure, formation mechanism and catalytic activity

Ultrasmall Ag NPs with different optical properties were synthesized by UV-irradiation method using chloramine T as an organic modifier. Two different formation mechanisms were identified for low and high concentration of chloramine T. It was confirmed that the use of low concentration of chloramine T allows the synthesis of highly reactive Ag NPs, whereas the use of high concentration of chloramine T results in the formation of crystalline AgCl. The performed catalytic investigation confirms that the proposed method can be used to synthesize nanoparticles with high catalytic activity for the reduction of methylene blue. It was noted that the rate constant over the total weight of the catalyst was equal to 8.34 g−1 s−1, which is significantly high in comparison with the literature data. This high catalytic activity was related to the defects on the surface of Ag NPs.

Characteristics of multiwalled carbon nanotubes-rhenium nanocomposites with varied rhenium mass fractions

The purpose of the article is to discuss the process of oxidation of carbon nanotubes subsequently subjected to the process of decoration with rhenium nanoparticles. The influence of functionalization in an oxidizing medium is presented and the results of investigations using Raman spectroscopy and infrared spectroscopy are discussed. Multiwalled carbon nanotubes rhenium-type nanocomposites with the weight percentage of 10%, 20% and 30% of rhenium are also presented in the article. The structural components of such nanocomposites are carbon nanotubes decorated with rhenium nanoparticles. Microscopic examinations under transmission electron microscope and scanning transmission electron microscope using the bright and dark field confirm that nanocomposites containing about 20% of rhenium have the most homogenous structure.

Nanocomposites Consisting of Carbon Nanotubes and Nanoparticles of Noble Metals

In the framework of the made researches nanocomposite of CNT-NPs type (Carbon Nanotube-Nanoparticles) consisting of multiwalled carbon nanotubes coated by rhodium nanoparticles and/or palladium using the two-step indirect method: chemical reduction have been produced. In the researches high-quality multi-walled carbon nanotubes MWCNTs with a length of 100 to 500 nm and a diameter of 8 to 20 nm previously obtained in the catalytic-chemical vapour deposition CCVD have been used. Nanotubes produced within the framework of own researches contain minor amounts of metallic impurities and amorphous carbon deposits. In order to deposit the noble metal nanoparticles on the surface of carbon nanotubes functionalization of multi-walled carbon nanotubes in a mixture of H2SO4 and HNO3 acids have been used. The prepared material has been subjected chemical reduction using noble metal precursors (RhCI3, PdCl2). The characterization of the produced material including the examination of the structure, morphology, chemical composition and evaluation of the size and distribution of rhodium and/or palladium nanoparticles on the surface of carbon nanotubes has been performed using: scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS). The produced nanomaterials may be used as the active layer of sensors of chemical/biological agents.