Eveline Popovici

In vitro controlled release of antihypertensive drugs intercalated into unmodified SBA-15 and MgO modified SBA-15 matrices

The use of nanotechnology in medicine and more specifically in drug delivery systems is set to spread rapidly. In order to broaden the range of matrices and implicitly to develop the class of drug delivery systems based on diffusion mechanism, in this study the starting materials, SBA-15 powder matrices, were engineered by MgO modification for antihypertensive drugs intercalation. Captopril and aliskiren were used as drug models. All powders, unmodified and MgO-modified silica matrices, and their corresponding drug-loaded samples were characterized by X-ray diffraction, N(2) adsorption and desorption, FTIR spectroscopy and scanning electron microscopy. The studied drug carriers were tested in the controlled drug release process and the influence of the silica pore morphology and geometry on drug release profiles was extensively studied. In order to analyze the data obtained from the in vitro release studies and to evaluate the kinetic release mechanism, the Korsmeyer and Peppas equation was used. The obtained drug delivery system based on MgO-SBA-15 matrix exhibits exciting structural features and is therefore promising for its use as antihypertensive drug delivery system, having potential therapeutic benefits resulting in safe and effective management of captopril and aliskiren adsorption and in vitro release.

Direct spectroscopic detection of framework-incorporated vanadium in mesoporous silica materials

Framework-incorporated vanadium mesoporous silica materials with different contents in vanadium were obtained by a facile, direct synthesis at room temperature, using VOSO4 x 5H2O as the vanadium precursor. The porous characteristics of the samples and the coordination environment of the vanadia in the structure were studied by a combination of techniques: X-ray diffraction, N2-adsorption/desorption, FT-Raman, FTIR-PAS and UV-Vis-DR, electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopy. A structural comparison is made using pulsed EPR and ENDOR spectroscopic techniques between vanadia deposited on the surface of MCM-41 by the Molecular Designed Dispersion method and as-synthesised samples of vanadia incorporated in the mesoporous silica framework using the above-mentioned synthesis method. The EPR study on the non-calcined samples proves the incorporation of a high amount of vanadium in the silica framework by the observation of a strong hyperfine coupling of the unpaired electron with 29Si. It demonstrates the feasibility for EPR to reveal structural information on true incorporation of metal ions in framework positions leading to metal oxides.

Preparation and thermal stability of Al2O3-clay and Fe2O3-clay nanocomposites, with potential application as remediation of radioactive effluents

In the last years metal/clays, aluminosilicates with properties and characteristics of microporous materials, have received more attention, due to the possibility of their use as matrix for nanoparticles encapsulation and stabilization processes. Some types of clays were comparatively evaluated for treating the simulated radioactive wastewater. The raw clay from Valea Chioarului Romania and its pillared forms with Al, Fe, pillars for decontamination of waste-waters with medium and low radioactivity were used. Characterization of the obtained materials was carried out using techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, BET analyses and thermogravimetric analysis (DTG-TG), respectively. Also, the thermal stability of nanocomposites was highly superior to native clay due to the presence of the well-dispersed clay nanolayer, which has a barrier property in a composite system. Clay nanocomposite sample materials were obtained with good thermal stability after calcination. Clay nanocomposites samples were evaluated for remediation of radioactive effluents by treating the radioactive wastes streams. The ion-exchange characteristics and the abilities to uptake radioisotopes of indigene clay from Valea Chioarului area-Romania were examined. The results showed that the precursor used in sample preparation influenced the structural and textural properties of nanocomposites and also capability of prepared modified clay samples by pillaring to be potential candidates for use in connection with environmental protection, remediation of radioactive effluents, respectively.

Preparation of Bi2Fe4O9 particles by hydrothermal synthesis and functional properties

In the present study, particles with different Bi2Fe4O9 micro/nanostructures with a few particular morphologies (flower-like nanoplatelets, hierarchical microstructures, perfectly square platelets single crystals, etc.) obtained under specific hydrothermal synthesis conditions were investigated. The role of the processing parameters (such as NaOH concentration, reaction temperature, and reaction duration time) on the phase formation mechanism and on the microstructural characteristics was investigated. All the Bi2Fe4O9 morphologies showed orthorhombic symmetry with space group Pbam. The photocatalytic properties and magnetic behavior as a function of the micro/nanostructural characteristics of various Bi2Fe4O9 powders were determined. In the presence of Bi2Fe4O9, a degradation rate of Rose Bengal in the range of 52–61% was determined after 180 min under UV light irradiation (λ = 254 nm). Magnetic activity with antiferromagnetic behavior and a transition at ∼240 K slightly dependent on the microstructures was found. The role of Bi2Fe4O9 microstructures in the photocatalytic activity and magnetic properties was discussed.

Zinc oxide-linen fibrous composites: morphological, structural, chemical and humidity adsorptive attributes:

The main result and characterizing aspect of the research consists of the effectiveness of novel ZnO-linen fibrous composites synthesized by means of hydrothermal deposition of zinc oxide onto linen fibers, with the assistance of two surfactants. This has a direct implication on the relationship between the morphological, structural and chemical attributes and water vapor sorption-desorption behavior. Methodology consists of the hydrothermal synthesis of zinc oxide onto linen fibrous substrates previously grafted with MCT-β-CD (MonoChloroTriazinyl–β-CycloDextrin) via a hydrothermal process. The morphological, structural and chemical properties of the samples were examined, in terms of a co-assisted investigation system: SEM images for the morphology, EDX analysis for surface composition, FTIR spectroscopy and X-ray diffractometry for structural samples features. Dynamic vapor sorption (DVS) analysis will complete this study. According to the results provided by the characterization technique, the uniformity of the fabric coated with ZnO powder hydrothermally synthesized with assistance of CTAB (Cetyl TrimethylAmmonium Bromide) is better than that of ZnO powder hydrothermally synthesized in the presence of Pluronic P123 and possesses good washing fastness. X-ray diffraction results have indicated that the composites exhibited a more ordered structure and higher water vapor sorption-desorption capacity (obtained by DVS analysis) compared with those of the reference fibrous linen supports.

Chromium(VI) Ion Removal from Aqueous Solutions Using a Zn-Al-type Layered Double Hydroxide

This paper deals with the structural and adsorptive characterisation of a Zn–Al-type layered double hydroxide to be used for the retention of chromate ions from aqueous media. Structural characterisation by X-ray diffraction and FT-IR spectroscopy showed that the material was a layered double hydroxide with carbonate in the interlayer; however, certain impurities were also identified. Thermogravimetric analysis allowed appropriate calcination temperatures to be chosen for the sorption studies. The equilibrium adsorption of the Cr(VI) ion was best described by the Langmuir–Freundlich equation. Calcining the material at 500 °C led to a product containing mostly stable zinc oxide with low adsorptive properties. The kinetics of Cr(VI) ion retention on the uncalcined layered double hydroxide obeyed the pseudo-first-order model as described by the Lagergren equation. Structural analysis of the product obtained after Cr(VI) ion sorption onto Zn–Al–CO3 showed that the carbonate anion was not replaced in the interlayer and that the Cr(VI) ion was adsorbed within cavities formed by three adjacent metal hydroxide octahedra situated at the edge of the brucite-like layer.

Calixarene-modified multi-wall carbon nanotubes

In order to improve the properties of carbon nanotubes, novel calixarene-modified multi-wall carbon nanotubes were prepared by using carbon nanotubes with carboxylic groups and various novel calixarene derivatives. This self-assembling process has allowed us to fabricate carbon nanotubes with functional organic molecules. The properties of the functionalized materials containing carbon nanotubes and calixarene derivatives were studied by using XRD, SEM, FTIR, DRS UV-VIS, and nitrogen adsorption isotherm at 77K.

Low magnetic field – assisted synthesis of MCM-41

Abstract The discovery that mixtures of network-forming inorganic species and surfactants self-assemble into mesostructured materials has considerably broadened synthesis strategies. Application of a magnetic field is one of potential methods to align and orient template molecules in view of specific pore structures and adsorption modification and may represent a new route for porous structure design. The present paper reports a micellar supramolecular templating approach for siliceous mesoporous MCM-41 in basic and acidic conditions under low steady magnetic field influence. The mesosilicates were prepared from aqueous mixtures containing TEOS and CTAB at 298 K under steady magnetic fields. All experimental results obtained both in basic and acid synthesis medium show the influence on the pore diameters and a 0 structural parameter as a consequence of the influence of magnetic field action on self-assembly of surfactant molecules in surfactant/silicate hybrids. The MCM-41 synthesis time under low magnetic field action was appreciably decreased.

Preparation and characterization of palladium supported on heulandite

Abstract Palladium modified heulandite single crystals by treatment with Pd(NH 3 ) 4 Cl 2 aqueous solutions under different experimental conditions were achieved. Pd nanoparticles with controlled size (d Pd ≈ 10 nm) were formed within the heulandite structure. The resulting materials were investigated by powder- XRD, AFM, TEM and UV-Vis techniques. Their particle size dimensions were determined by XRD using the Scherrer equation, and verified by AFM and TEM. The structure of the heulandite with channel form and dimensions at the molecular level was found to play the role of a template controlling the size and distribution of the formed Pd-nanoparticles.

Sorption of transient metal ions into clinoptilolite from waste water and recycling the used zeolite into a composite fertilizer

Abstract The natural clinoptilolite of Mârsid (Romania) is suitable for the treatment of certain waste waters to retain some metal cations. For the improvement of ion exchange capacity, the chemical activation by various methods was studied. The ion exchange process equilibrium for a series of cations in the clinoptilolite was studied. The exchange isotherm shape, as well as the value of the standard free enthalpy which characterizes the exchange with NH 4 + ion, indicated the clinoptilolite high affinity for this ion. For the exchange processes where Cu 2+ and Zn 2+ ions were involved, isotherms of the same type were obtained, which indicated the impossibility of reaching the exchange maximum degree because of the “ionic sieve” effect. The clinoptilolite low affinity towards Mn 2+ ion was explained by the high hydration capacity of Mn 2+ , owing to the fact that “d” orbitals on level 3 are semioccupied with electrons. The composite fertilizer samples were studied by X-ray diffraction and by thermogravimetric and thermodifferential analysis. Also, the agrochemical quality was evaluated by the hygroscopicity point and agglomeration capacity.