Optical properties of Nd3+ doped ionic liquid immobilized on mesoporous silica support.

The synthesis of a new material based on Nd3+ ions doped into an imidazolium-type ionic liquid with further immobilization on a mesoporous silica support is reported. The material was investigated by DR-UV/VIS, FT-IR, thermogravimetric analysis, N2 adsorption measurements and time-resolved photoluminescence spectroscopy. The intensity of the near-infrared emission of Nd3+ was weak and the lifetime measured at about 910 nm was 7 micros.

Europium3+: an efficient luminescence probe for the Si to Al ratio and silylation effects in the microporous-mesoporous Zeogrid materials.

The optical response of europium ions in the parent (non-silylated) and silylated microporous-mesoporous Zeogrid materials was investigated in detail in relation to Zeogrid structure. All materials were characterized using nitrogen adsorption isotherms, powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry, and time-resolved photoluminescence spectroscopy. A two europium species distribution with distinct luminescence spectra and lifetimes was found for both parent and silylated Zeogrid. In the parent Zeogrid, the short-lived europium species is characterized by the intensity ratio R=I(5D0-(7)F2)/I(5D0-(7)F1) or asymmetry values of approximately 0.4-0.7 and photoluminescence (PL) lifetimes of 110-125 micros and therefore is assigned to an almost fully hydrated europium species. In the silylated Zeogrid, the short-lived europium species is characterized by asymmetry values of 1.0-2.4 and lifetimes of 160-180 micros suggesting a relatively distorted europium environment. The long-lived europium species exhibits similar asymmetry ratios in the parent and silylated Zeogrid, which vary between 5.0 and 6.2 with increasing Si to Al ratio from 25 to 150 and slightly different PL lifetimes. The mechanism responsible for the intensity of the electric and magnetic forbidden 5D0-(7)F0 transition was determined to be J-mixing of the 7F2 into the 7F0 state through the axial second-order crystal-field potential. The comparison between the photoluminescence properties of europium in the parent and silylated Zeogrid demonstrates that the effects of rehydration were strongly suppressed following silylation.

Degradation of the chlorophenoxyacetic herbicide 2,4-D by plasma-ozonation system.

A novel advanced oxidation process based on the combination of ozonation with non-thermal plasma generated in a pulsed corona discharge was developed for the oxidative degradation of recalcitrant organic pollutants in water. The pulsed corona discharge in contact with liquid, operated in oxygen, produced 3.5mgL-1 ozone, which was subsequently introduced in the ozonation reactor. The solution to be treated was continuously circulated between the plasma reactor and the ozonation reactor. The system was tested for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and considerably improved performance as compared to ozonation alone, both with respect to the removal of the target compound and to mineralization. The apparent reaction rate constant for 2,4-D removal was 0.195min-1, more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60min treatment and the chlorine balance confirms the absence of quantifiable amounts of chlorinated by-products. The energy efficiency was considerably enhanced by shortening the duration of the discharge pulses, which opens the way for further optimization of the electrical circuit design.

Using chiral ionic liquid additives to enhance asymmetric induction in a Diels-Alder reaction.

A bis-oxazoline ligand has been complexed using Cu(ii) and Zn(ii) trifluoromethanesulfonate and a range of chiral ionic liquid (CIL) additives based on natural products were used as a co-catalyst for a Diels-Alder reaction. The catalytic performance of these systems was compared for the asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene with and without the presence of a CIL additive. In the absence of the CIL, both catalysts resulted in low enantioselectivities in conventional solvents and ionic liquids. However, whilst only a minor effect of the CIL was observed for the Cu based catalyst, in the case of the Zn based catalyst, significant enhancements in endo enantioselectivity of up to 50% were found on the addition of a CIL.

New evidence on the formation of oxidizing species in corona discharge in contact with liquid and their reactions with organic compounds.

The objective of these investigations is to understand in more detail how organic compounds in water are degraded during plasma treatment. The formation of oxidizing species (ozone (O3), hydrogen peroxide (H2O2) and hydroxyl radicals (OH)) in a pulsed corona discharge in contact with liquid is investigated. The degradation of a target organic compound (methylparaben) in aqueous solution was increased when combining plasma treatment with ozonation, using the O3 generated in the discharge. Enhanced mass transfer of O3 obtained in this plasma+O3 configuration leads to a six fold increase of MeP oxidation rate. The evolution of oxidants concentration during treatment of MeP solutions provides information on their consumption in reactions with MeP and its oxidation products. The correlation of MeP degradation results (MeP removal and mineralization) with O3 consumption and the identified reaction products confirms that although O3 plays an important role in the degradation, for the mineralization OH radicals have an essential contribution. The concentration of OH radicals is diminished in the solutions containing MeP as compared to plasma-treated water, indicating OH consumption in reactions with the target compound and its degradation products. The concentration of H2O2 in the liquid can be either increased or reduced in the presence of MeP, depending on its initial concentration. On the one hand, decomposition of H2O2 by OH or O3 is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation.

Degradation of methylparaben in water by corona plasma coupled with ozonation.

The degradation of methylparaben (MeP) in water was investigated using a pulsed corona discharge generated in oxygen, above the liquid. A comparison was made between results obtained in semi-batch corona (SBC) configuration (stationary solution, continuous gas flow) and results obtained in a semi-batch corona with recirculation combined with ozonation (SBCR + O3), where the liquid is continuously circulated between a solution reservoir and the plasma reactor and the effluent gas containing ozone is bubbled through the solution in the reservoir. It was found that MeP was completely degraded after 10-15 min of treatment in both configurations. Oxidation by ozone alone, in the absence of plasma, was a slower process. The energy efficiency for MeP removal (Y MeP) and for mineralization (Y TOC) was significantly higher in the SBCR + O3 configuration (Y MeP = 7.1 g/kWh at 90 % MeP removal and Y TOC = 0.41 g/kWh at 50 % total organic carbon (TOC) removal) than in the SBC configuration (Y MeP = 0.6 g/kWh at 90 % MeP removal and Y TOC = 0.11 g/kWh at 50 % TOC removal).

Degradation of antibiotics in water by non-thermal plasma treatment.

The decomposition of three ß-lactam antibiotics (amoxicillin, oxacillin and ampicillin) in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration. Solutions of concentration 100 mg/L were made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gas-liquid interface. The electrical discharge was operated in pulsed regime, at room temperature and atmospheric pressure, in oxygen. Amoxicillin was degraded after 10 min plasma treatment, while the other two antibiotics required about 30 min for decomposition. The evolution of the degradation process was continuously followed using liquid chromatography-mass spectrometry (LC-MS), total organic carbon (TOC) and chemical oxygen demand (COD) analyses.

Synphos modified Pt nanoclusters, their heterogenization by silica sol-gel entrapment, and catalytic activity in hydrogenolysis of bicyclo[2.2.2]oct-7-enes and hydrogenation of ethyl pyruvate.

Platinum (Pt) colloids modified by the chiral ligand synphos were prepared with the goal of obtaining a catalytic nanomaterial and were subsequently embedded in silica to form a heterogeneous catalyst. The systems were characterized by (31)P-NMR, x-ray diffraction, molecular modeling and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) measurements. These colloids, both as 'quasi-homogeneous catalysts' (or soluble heterogeneous catalysts) and embedded in silica (heterogeneous catalysts) were employed in the selective hydrogenolysis of highly sterically constrained bicyclo[2.2.2]oct-7-enes and hydrogenation of ethyl pyruvate.