Linking the Defective Structure of Boron-Doped Carbon Nano-Onions with Their Catalytic Properties: Experimental and Theoretical Studies.

Defects are widely present in nanomaterials, and they are recognized as the active sites that tune surface properties in the local region for catalysis. Recently, the theory linking defect structures and catalytic properties of nanocatalysts has been most commonly described. In this study, we prepared boron-doped carbon nano-onions (B-CNOs) by applying an annealing treatment of ultradispersed nanodiamond particles and amorphous boron. These experimental conditions guarantee doping of CNOs with boron atoms in the entire carbon nanostructure, thereby ensuring structural homogeneity. In our research, we discuss the correlations between defective structures of B-CNOs with their catalytic properties toward SO2 and tert-butanol dehydration. We show that there is a close relationship between the catalytic properties of the B-CNOs and the experimental conditions for their formation. It is not only the mass of the substrates used for the formation of B-CNOs that is crucial, that is, the mass ratio of NDs to amorphous B, but also the process, including temperature and gas atmosphere. As it was expected, all B-CNOs demonstrated significant catalytic activity in HSO3- oxidation. However, the subsequent annealing in an air atmosphere diminished their catalytic activity. Unfortunately, no direct relationship between the catalytic activity and the presence of heteroatoms on the B-CNO surface was observed. There was a linear dependence between catalytic activity and Raman reactivity factors for each of the B-CNO materials. In contrast to SO2 oxidation, the B-CNO-a samples showed higher catalytic activity in tert-butanol dehydration due to the presence of Brønsted and Lewis acid sites. The occurence of three types of boron-Lewis sites differing in electron donor properties was confirmed using quantitative infrared spectroscopic measurements of pyridine adsorption.

IR and NMR studies of hierarchical material obtained by the treatment of zeolite Y by ammonia solution.

Ammonia treatment of ultrastable zeolite Y has a great impact on its features. XRD showed a partial loss of crystallinity coupled with a loss of long-distance zeolite ordering. However, a typical short-range zeolite ordering, in the light of 29Si NMR studies, was largely preserved. 27Al MAS NMR spectra evidenced that most of Al was located in zeolitic tetrahedral positions, but some of them adopted a distorted configuration. Evolution of zeolites acidity was followed quantitatively by using IR. In particular, such studies revealed the presence of strongly acidic SiOHAl groups. IR studies suggest also heterogeneity of these OH groups. The heterogeneity of SiOHAl groups was a consequence of the less ordered structure of zeolites treated with ammonia solutions. It was also found that the treatment with ammonia solutions yields hierarchical material. The samples revealed promising catalytic properties in the liquid phase isomerization of α-pinene. Zeolites desilicated with ammonia may constitute an inexpensive route yielding viable hierarchical catalysts.

Boron-Doped Polygonal Carbon Nano-Onions: Synthesis and Applications in Electrochemical Energy Storage.

Doping of carbon nanostructures with heteroatoms, such as boron or nitrogen, is one of the most effective ways to change their properties to make them suitable for various applications. Carbon nano-onions (CNOs) doped with boron (B-CNOs) were prepared by annealing (1650 °C) nanodiamond particles (NDs) under an inert He atmosphere in the presence of B. Their physicochemical properties were measured using transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), 10 B and 11 B solid-state magic-angle spinning (MAS) NMR spectroscopy, X-ray powder diffraction (XRD), Raman spectroscopy, porosimetry, and differential-thermogravimetric analyses (TGA-DTG). These properties were systematically discussed for the undoped and B-doped CNO samples. The amount of substitutional B in the CNO samples varied from 0.76 to 3.21 at. %. The TEM, XRD, and Raman analyses revealed that the increased amount of B doping resulted in decreased interlayer spacing and polygonization of the structures, which in turn led to their unusual physicochemical properties. All synthesized materials were tested as electrodes for electrochemical capacitors. The B-CNOs with low concentration of doping agent exhibited higher reversible capacitances, mainly owing to the formation of hydrophilic polygonal nanostructures and higher porosity.

Silicone-stabilized liposomes as a possible novel nanostructural drug carrier.

Development of silicone stabilized liposomes which can serve as novel drug nanocarriers is presented. Silicone precursor 1,3,5,7-tetramethylcyclotetrasiloxane (D4(H)) was introduced into the bilayer of the cationic liposomes prepared from egg yolk phosphatidylocholine (PC) and double-tailed dimethyldioctadecylammonium bromide (DODAB). The silicone material was created inside of the liposomal bilayer in the base-catalyzed polycondensation process of the D4(H) what was confirmed employing (29)Si solid-state MAS NMR and FTIR measurements. Surfactant lysis experiments revealed that resulted systems can be effectively stabilized. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements demonstrated that the silicone-stabilized liposomes have typical lipid vesicle's morphology and mean hydrodynamic diameters in the range of about 110nm. They have considerably lower tendency for aggregation than the pristine liposomes. The permeability of vesicles can be tuned by introducing various amounts of silicone precursor into the liposome bilayer, as confirmed in calcein-release studies. The effect of fetal bovine serum (FBS) on the stability of liposomes was also tested in in vitro studies. Biological studies revealed that resulted liposomes can be considered as possible drug nanocarriers because they are not toxic to human skin fibroblasts (HSFs) and mouse embryonic fibroblasts (MEFs).

Synthesis of novel perfluoroalkylglucosides on zeolite and non-zeolite catalysts.

Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state 27Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 °C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts.

Conversion of rice husk ash to zeolite beta.

White rice husk ash (RHA), an agriculture waste containing crystalline tridymite and alpha-cristobalite, was used as a silica source for zeolite Beta synthesis. The crystallization of zeolite Beta from RHA at 150 degrees C in the presence of tetraethylammonium hydroxide was monitored by XRD, FTIR and (29)Si MAS NMR techniques. It was found that zeolite Beta started to form after 12h and the complete crystallization of zeolite Beta phase was achieved after 2d. XRD, (29)Si MAS NMR and solid yield studies indicate that the transformation mechanism of silica present in RHA to zeolite Beta involves dissolution of the ash, formation of an amorphous aluminosilicate after 6h of crystallization, followed by dissolution in the mother liquor and final transformation to pure zeolite Beta crystals.