Joanna Breczko

Preparation and characterization of composites that contain small carbon nano-onions and conducting polyaniline

Small multilayer fullerenes, also known as carbon nano-onions (CNOs; 5-6 nm in diameter, 6-8 shells), show higher reactivity than other larger carbon nanostructures. Here we report the first example of an in situ polymerization of aniline on phenyleneamine-terminated CNO surfaces. The green, protonated, conducting emeraldine polyaniline (PANI) was directly synthesized on the surface of the CNO. The functionalized and soluble CNO/PANI composites were characterized by TEM, SEM, DSC, Raman, and infrared spectroscopy. The electrochemical properties of the conducting CNO/PANI films were also investigated. In comparison with pristine CNOs, functionalized carbon nanostructures show dramatically improved solubility in protic solvents, thus enabling their easy processing for coatings, nanocomposites, and biomedical applications.

Electrochemical properties of composites containing small carbon nano-onions and solid polyelectrolytes

The preparation and electrochemical properties of a novel type of composite made of small carbon nano-onions (CNOs) with poly(diallyldimethylammonium chloride) (PDDA) or chitosan (Chit) were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Composite films on glassy carbon electrode surfaces were deposited by a coating method, applying a drop of solution containing the suspended CNOs and filler, PDDA or Chit. Composites form relatively porous structures on the electrode surface and exhibit typical capacitive behavior, as well as excellent mechanical and electrochemical stability over a wide potential window, from +600 to −600 mV. The capacitance of the films is primarily related to the amount of CNOs incorporated into the layer of the filler. The capacitance ranges between 20 and 30 F g−1 of incorporated CNOs. The composites also show a low relaxation time from resistive to capacitive behavior, therefore indicating that they can operate as capacitors in short time windows.

STM‐Based Molecular Junction of Carbon Nano‐Onion

was almost concurrent with that of the CNTs, progress in thisfield has been very slow. Our current research has been cen-tered mainly on carbon-based materials, such as CNOs, whichrepresent a structural link between the fullerenes and themulti-wall carbon nanotubes. The CNO structures consist ofa hollow spherical fullerene core surrounded by concentric andcurved graphene layers with increasing diameters. The dis-tance between the layers is very close to the interlayer dis-tance in bulk graphite (0.34 nm).

The Electrochemical Properties of Nanocomposite Films Obtained by Chemical In Situ Polymerization of Aniline and Carbon Nanostructures

Interactions between the π bonds in the aromatic rings of polyaniline (PANI) with carbon nanostructures (CNs) facilitate charge transfer between the two components. Different types of phenyleneamine-terminated CNs, including carbon nano-onions (CNOs) and single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively), were prepared as templates, and the CN/PANI nanocomposites were easily prepared with uniform core-shell structures. By varying the ratio of the aniline monomers relative to the CNs in the in situ chemical polymerization process, the thickness of the PANI layers was effectively controlled. The morphological and electrical properties of the nanocomposite were determined and compared. The thickness and structure of the PANI films on the CNs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and infrared spectroscopy. TEM and SEM revealed that the composite films consisted of nanoporous networks of CNs coated with polymeric aniline. The electrochemical properties of the composites were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. These studies showed that the CN/PANI composite films had lower resistance than pure polymeric films of PANI, and the presence of CNs much improved the mechanical stability. The specific electrochemical capacitance of the CNO/PANI composite films was significantly larger than for pure PANI.

Carbon Nano-Onions and Biocompatible Polymers for Flavonoid Incorporation

In recent years, nanotechnology, which is defined as the creation and control of the properties of nanometric-scale objects, has been playing an increasingly significant role in medicine, material engineering, and pharmacology. The potential applications of carbon nanostructures in biotechnology and nanomedicine is particularly noteworthy. Carbon nanotubes (CNTs) are useful materials in a variety of biomedical applications, particularly in biosensing and optical imaging, and also in novel therapeutic strategies. Using CNTs as signal transducers in biosensors has resulted in improved detection limits and signal amplification because they possess multiple biorecognition elements attached to a single tube. Despite the progress, there are still many challenges related to issues of the reproducible synthesis of CNTs with well-defined structures and physicochemical properties. Some of these problems include the prevention of nanotube aggregation during electrode modification, the effective separation of semiconducting and conducting CNTs, and separation of nanotubes with uniform lengths. It has been previously observed that the reactivity of fullerene-like structures decreases with increasing size owing to a decrease of the curvature of the molecule. While the various forms of CNTs are chemically inert, their ends and sidewalls can be functionalized by a variety of chemical groups. Small carbon nano-onions (CNOs) are potentially better systems for some of these applications, because they show higher reactivity and solubility in many solvents. Various reactions have been reported for CNOs using strategies such as oxidation of defects, fluorination, radical addition, 1,3-dipolar cycloaddition, or polymerization. Our studies have shown that small carbon nano-onions can also be used as components of conductive nanocomposites, increasing the specific capacity of the layers on the surface of the elecACHTUNGTRENNUNGtrodes.[10–13] Nanostructures with conductive polymers (polyaniline) and polyelectrolytes have also been prepared and used in the detection of neurohormones, such as dopamine. In addition, the good biocompatibility and low cytotoxicity of CNOs are also very promising. Studies of normal cells (human skin fibroblasts), conducted with the MTT method using CNOs, confirm the low toxicity and good biocompatibility of these carbon nanostructures over a wide range of concentrations. Additionally, it is possible to modify the surfaces of CNOs with biomolecules without loss of their activity. We have worked specifically with the avidin–biotin model system. Polyphenolic compounds, such as flavonoids, exhibit protective effects on humans, for instance, in the prevention of cardiovascular diseases. It has been shown that flavonoids could be successfully applied in traditional medicine for the treatment of inflammations, wounds, certain forms of cancer, infections, diarrhea, diabetes mellitus, and other ailments. Polyphenolic compounds interact with proteins mainly by hydrophobic/ionic interactions. Quercetin (Q, 3,3’,4’,5,7-pentahydroxyflavone; Scheme 1) is a polyphenolic

Surface Plasmon Resonance Imaging biosensor for cystatin determination based on the application of bromelain, ficin and chymopapain

A Surface Plasmon Resonance Imaging (SPRI) sensor based on bromelain or chymopapain or ficin has been developed for specific cystatin determination. Cystatin was captured from a solution by immobilized bromelain or chymopapain or ficin due to the formation of an enzyme-inhibitor complex on the biosensor surface. The influence of bromelain, chymopapain or ficin concentration, as well as the pH of the interaction on the SPRI signal, was investigated and optimized. Sensor dynamic response range is between 0–0.6 μg/ml and the detection limit is equal to 0.1 μg/ml. In order to demonstrate the sensor potential, cystatin was determined in blood plasma, urine and saliva, showing good agreement with the data reported in the literature.

Bis(2,2':6',2''-terpyridine)-ruthenium(II) bis-(perchlorate) hemihydrate.

The asymmetric unit of the title compound, [Ru(C15H11N3)2](ClO4)2·0.5H2O, contains one ruthenium–terpiridine complex cation, two perchlorate anions and one half-molecule of water. Face-to-face and face-to-edge π-stacking interactions between terpyridine units [centroid–centroid distances = 3.793 (2) and 3.801 (2)  Å] stabilize the crystal lattice The partially occupied water molecule interacts with two perchlorate ions via O—H⋯O hydrogen bonds. In the crystal lattice, the complex cations, perchlorate ion-water pairs and the second perchlorate anions are arranged into columns along b direction.