New organic-inorganic hybrid compounds based on sodium peroxidomolybdates (VI) and derivatives of pyridine acids : structure determination and catalytic properties

Two organic-inorganic hybrids based on sodium peroxidomolybdates(VI) and 3,5-dicarboxylic pyridine acid (Na-35dcpa) or N-oxide isonicotinic acid (Na-isoO) have been synthesized and characterized. All compounds contain inorganic parts: a pentagonal bipyramid with molybdenum center, and an organic part containing 3,5-dicarboxylic pyridine acid or N-oxide isonicotinic acid moieties. The type of organic part used in the synthesis influences the crystal structure of obtained compounds. This aspect can be interesting for crystal engineering. Crystal structures were determined using powder X-ray diffraction or single crystal diffraction for compounds Na-35dcpa and Na-isoO, respectively. Elemental analysis was used to check the purity of the obtained compounds, while X-ray Powder Diffraction (XRPD) vs. temp. was applied to verify their stability. Moreover, all the compounds were examined by Infrared (IR) spectroscopy. Their catalytic activity was tested in the Baeyer–Villiger (BV) oxidation of cyclohexanone to ε-caprolactone in the oxygen-aldehyde system. The highest catalytic activity in the BV oxidation was observed for Na-35dcpa. The compounds were also tested for biological activity on human normal cells (fibroblasts) and colon cancer cell lines (HT-29, LoVo, SW 620, HCT 116). All compounds were cytotoxic against tumor cells with metastatic characteristics, which makes them interesting and promising candidates for further investigations of specific anticancer mechanisms

Composites of Montmorillonite and Titania Nanoparticles Prepared by Inverse Microemulsion Method: Physico-Chemical Characterization

TiO2/montmorillonite composites were synthesized using inverse micellar route for the preparation of titania nanoparticles (4–6 nm diameter) in 1-hexanol and for the dispersion of one of the clay components. Two series of composites were obtained: one derived from cetyltrimethylammonium organomontmorillonite (CTA-Mt), exfoliated in 1-hexanol, and the other from sodium form of montmorillonite (Na-Mt) dispersed by formation of an inverse microemulsion in 1-hexanol. The TiO2 content ranged from 16 to 64 wt.%. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, thermal analysis, and N2 adsorption-desorption isotherms. The Na-Mt-derived component was shown to undergo transformation to CTA-Mt, as indicated by basal spacing of 17.5 nm, due to the interaction with the CTABr surfactant in inverse microemulsion. It was also better dispersed and intermixed with TiO2 nanoparticles. As a result, the TiO2/Na-Mt series displayed superior textural properties, with specific surface area up to 256 m2g−1 and pore volume up to 0.247 cm3g−1 compared with 208 m2g−1 and 0.231 cm3g−1, respectively, for the TiO2/CTA-Mt counterpart. Members of both series were uniformly mesoporous, with the dominant pore size around 5 nm, i.e., comparable with the dimensions of titania nanoparticles. The advantage of the adopted synthesis method is discussed in the context of other preparative procedures used for manufacturing of titania-clay composites

Synthesis of Nanocrystalline Mg-Al Hydrotalcites in the Presence of Starch—the Effect on Structure and Composition

The study describes the synthesis of Mg-Al hydrotalcite (Ht) with the use of starch as a structure controlling biotemplate. Syntheses were carried out at room temperature, by co-precipitation at pH = 10. The investigated synthesis parameters included the nature of the precipitating agent (NaOH/Na2CO3 or NH3aq/(NH4)2CO3), the nature of starch (potato, corn and cassava), the method of starch addition to reagents, the method of drying and the effect of washing. The materials were examined with X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and infrared spectroscopy. The data show that synthesis of Ht materials in the presence of starch, with use of the ammonia-based precipitant, enabled preparation of nanocrystalline Ht with very fine (<50 nm) particle size. All investigated starches had a similar effect on the crystallinity and the grain size of Ht precipitates. Ht with the smallest nanocrystals was obtained when starch was present in all solutions used for synthesis, and the final product subjected to freeze drying. Washing with water was found to enhance recrystallization and exchange of nitrates for carbonates. Infrared spectra showed that an interaction exists between the biopolymer template and the Ht particles, resulting in a higher degree of order within the Ht-adhering starch component

Fine Crystalline Mg-Al Hydrotalcites as Catalysts for Baeyer-Villiger Oxidation of Cyclohexanone with H2O2

The catalytic activity of Mg-Al hydrotalcite (HT) materials in base-catalyzed reactions is known to be promoted by the low crystallinity of the HT solid. In the present work, two routes enabling the preparation of finely crystalline Mg-Al HT materials were explored: (1) the inverse microemulsion technique, and (2) co-precipitation in the presence of starch. Carbonate, chloride and bromide forms of HT were prepared, examined with X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and infrared spectroscopy, and used as catalysts in the Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone with a H2O2/acetonitrile system. The bromide forms proved significantly less active than the chlorides and carbonates, as they promoted nonselective consumption of H2O2. The fine crystalline materials were more active than the more crystalline HT references obtained by conventional co-precipitation. Catalysts prepared by inverse microemulsion were less crystalline and more active than the starch-templated ones, but suffered stronger deactivation by the acidic reaction environment. Alkalization of the reaction medium with NaHCO3 stabilized the HT materials and increased the ε-caprolactone yield, which became comparable for both types of fine crystalline catalysts—thus pointing to the synthesis involving a simple and cheap starch templating approach as being a particularly attractive one

Removal of amoxicillin and ampicillin using manganese dioxide/montmorillonite composite

BACKGROUND Clay-based materials represent great potential for the development of efficient and environmentally friendly sorbents. The study focuses on a laboratory-obtained manganese dioxide/montmorillonite (MnO2/MMT) composite for removal of two types of antibiotics - amoxicillin (AMX) and ampicillin (AMP) - from aqueous solution. RESULTS The composite was successfully prepared using a reduction procedure involving the reaction between potassium permanganate (KMnO4) and hydrochloric acid (HCl) to form MnO2 followed by the addition of MMT. X-ray analysis, scanning electron microscopy, X-ray fluorescence and Fourier transform infrared spectroscopy were performed for characterization of physicochemical and structural properties, simultaneous thermogravimetry and differential scanning calorimetry for estimation of thermal stability and high-performance liquid chromatography for determination of antibiotic equilibrium concentrations in aqueous solution. The precipitated MnO2 component, manifested by long fibers, corresponded to the tunnel structure of cryptomelane. In the case of MnO2/MMT it is evident that MnO2 developed short fibers with the participation of the MMT matrix. The thermal data suggested that the MnO2 phase upon contact with the clay support showed better thermal stability. The final decomposition of Mn2O3 was shifted to higher temperature of 985 degrees C. Adsorption procedure in a batch regimen showed sufficient sorption ability for both antibiotics with over 90% efficiency. For AMP the value of q(max) was about 45 mg g(-1) and for AMX it was only 21 mg g(-1). CONCLUSIONS The results provided valuable information for the design of a potentially inexpensive clay-based adsorbent and demonstrated the removal of two types of broad-spectrum beta-lactam antibiotics from aqueous solution to a sufficient degree.Web of Scienc