Enhancing photocatalytic tetracycline degradation through the fabrication of high surface area CeO2 from a cerium-organic framework.

Water pollution is a global environmental issue, and the presence of pharmaceutical compounds, such as tetracyclines (TCs), in aquatic ecosystems has raised growing concerns due to the potential risks to both the environment and human health. A high surface area CeO2 was prepared via atmospheric thermal treatment of a metal-organic framework of cerium and benzene-1,3,5-tricarboxylate. The effects of calcination temperature on the morphology, structure, light absorption properties and tetracycline removal efficiency were studied. The best activity of the photocatalysts could be achieved when the heat treatment temperature is 300 °C, which enhances the photocatalytic degradation performance towards tetracycline under visible light. The resulting CeO2 particles have high capacity for adsorbing TCs from aqueous solution: 90 mg g-1 for 60 mg L-1 TCs. As a result, 98% of the initial TC can be removed under simulated sunlight irradiation. The cooperation of moderate defect concentration and disordered structure showed tetracycline removal activity about 10 times higher than the initial Ce-MOF. An embryotoxicity assessment on zebrafish revealed that treatment with CeO2 particles significantly decreased the toxicity of TC solutions.

Voltammetric analysis of luminescent markers in gunshot residues.

Currently, SEM-EDS is used to detect gunshot residue (GSR) from the presence of Ba, Pb, and Sb in the sample. However, the development of new nontoxic ammunition (NTA) has prevented conventional metals from being found. In this work, we aim to determine the presence of an inorganic luminescent chemical marker based on rare earth in gunshot residues using the technique of squarewave voltammetry (SWV). After firing, the luminescent complex [(Eu2 Zr)(btc)3 (Hbtc)0.5 .6H2 O], which is used as a chemical marker, can be detected under a UV lamp. An aqueous solution with 0.1 mol L-1 KCl as supporting electrolyte can be easily collected on carbon paste electrode surfaces for SWV analysis A = 100 mV, f = 10 Hz, and step potential of 5 mV are required. The luminescent marker incorporated into the carbon paste electrode showed two anodic peak currents in the region of 0.4 V (vs Ag/AgCl) and at 0.75 V (vs Ag/AgCl) and also a cathodic one in 0.4 V (vs Ag/AgCl). SEM-EDS was able to analyze the same voltammetric results for conventional and nontoxic ammunition containing the luminescent marker. Therefore, voltammetry and SEM-EDS are valid for detecting the new residue marker in GSR. Despite this, the electrochemical method is still more advantageous because of its low cost and lack of expensive equipment and supplies in forensic laboratories.

Investigation of the preparation and reactivity of metal-organic frameworks of cerium and pyridine-2,4,6-tricarboxylate.

The synthesis of three coordination polymers of cerium(III) and the ligand pyridine-2,4,6-tricarboxylate (PTC) is reported. Two of the materials crystallise under hydrothermal conditions at 180 °C, with [Ce(PTC)(H2O)2]·1.5H2O, (1), being formed on extended periods of reaction time, 3 days or longer, and Ce(PTC)(H2O)3, (2), crystallising after 1 day. Both phases contain Ce(III) but are prepared using the Ce(IV) salt Ce(SO4)2·4H2O as reagent. Under solvothermal conditions (mixed water-N,N-dimethylformamide (DMF)), the phase [Ce(PTC)(H2O)(DMF)]·H2O (3) is crystallised. The structures of the three materials are resolved by single crystal X-ray diffraction, with the phase purity of the samples determined by powder X-ray diffraction and thermogravimetric analysis. (1) is constructed from helical chains cross-linked by the PTC linkers to give a three-dimensional structure that contains clusters of water molecules in channels that are hydrogen-bonded to each other and to additional waters that are coordinated to cerium. (2) also contains nine-coordinate cerium but these are linked to give a dense framework, in which water is directly coordinated to cerium. (3) contains corner-shared nine-coordinate cerium centres, linked to give a framework in which Ce-coordinated DMF fills space. Upon heating the material (1) in air all water is irreversibly lost to give a poorly crystalline anhydrous phase Ce(PTC), as deduced from X-ray thermodiffractometry and thermogravimetric analysis. The material (1), however, is hydrothermally stable, and is also stable under oxidising conditions, where immersion in 30% H2O2 gives no loss in crystallinity. Oxidation of around 50% of surface Ce to the +4 oxidation state is thus possible, as evidenced by X-ray photoelectron spectroscopy, which is accompanied by a colour change from yellow to orange. Photocatalytic activity of (1) is screened and the material shows effective degradation of methyl orange.

Experimental and Theoretical Studies of Glyphosate Detection in Water by an Europium Luminescent Complex and Effective Adsorption by HKUST-1 and IRMOF-3.

Designing an effective and simple detection method to quantify glyphosate (GLY) herbicide is desirable. Current chromatography-mass spectrometry and electrochemical methods can be used for this purpose, but these methods are difficult to be made portable and need high-cost equipment. Here, we evaluate a luminescent ß-diketonate-Eu-ethylenediaminetetraacetic acid complex for GLY quantification in aqueous media on the basis of the luminescent quenching process. This complex successfully measured GLY at concentrations ranging from 5 × 10-7 to 10-5 mol L-1. Theoretical methods (LUMPAC) are also performed to identify the complex most probable structure in solution. We also demonstrate that the metal-organic frameworks HKUST-1 and IRMOF-3, easily synthesized, effectively adsorb GLY in water in about 30 min of contact.

Influence of surface treatment on the fluorescence of composite resins subjected to in situ bleaching.

OBJECTIVE: Use fluorescence analysis to evaluate the effect of polishing and surface sealant on the color of composite resin bleached with carbamide peroxide and subjected to staining. MATERIALS AND METHODS: Forty-eight composite resin specimens (Z250/Z350XT) were fabricated. After 24 hours stored in distilled water, all specimens were submitted to in situ bleaching with 16% home peroxide for 8 hours daily for a period of 14 days. Subsequently specimens were separated in three groups according to surface treatment proposed (group 1-polishing Sof-Lex; group 2-BisCover; group 3-control). After this, all the specimens were stained with red wine. A spectrofluorometer was used to evaluate the fluorescence in two readouts (L0-after surface treatment and L1-after staining).Data were analyzed by applying ANOVA using a statistical software program. RESULTS: No differences were shown for the factor treatment and other interactions. The lowest mean fluorescence value was found for Z350XT resin (1759.18 ± 0.13) when compared with Z250 (6863.92 ± 0.13). There was significant difference in the mean fluorescence values for all surface treatments between the two different readouts L0 (4820.93 ± 0.05) and L1 (3802.17 ± 0.05). CONCLUSION: The results suggested that all surface treatments proposed did not influenced the results of wine staining of bleached resins when compared with the control evaluated by the fluorescence method. CLINICAL SIGNIFICANCE: The purposes of this research was to find solutions, by means of surfaces treatment, to achieve restorations with a satisfactory and similar final aspect in relation to the teeth, and avoid discrepancies related to the esthetics and longevity of the restoration.

Ion-exchange resin as a new tool for characterisation of coordination compounds and MOFs by NMR spectroscopy.

1H and 13C NMR spectroscopy is used to investigate the organic constituents of metal complexes, MOFs and coordination compounds synthesised under solvothermal and precipitation conditions. The elucidation of the ligands in paramagnetic compounds bearing Cu2+ (d9), Gd3+ (f7), Eu3+ (f6), Fe3+ (d5), ions after treatment with a cationic exchange resin is possible. We prove the efficiency of two post-synthesis linker modifications on diamagnetic IRMOF-3 Zn2+ (d10) with ethyl isocyanate and benzyl bromide.

Effect of lanthanum loading on nanosized CeO2-ZnO solid catalysts supported on cordierite for diesel soot oxidation.

We report the application of a solid lanthanum-ceria-zinc catalyst in the catalytic regeneration of diesel particulate filters (DPF) in diesel engines. We synthesized a CeO2-ZnO-La2O3 (Ce-Zn-La) mixed oxide by a lactic acid-mediated sol-gel method, which efficiently coated cordierite substrates for soot capture and combustion. We studied the effects of La loading on the physicochemical and catalytic properties of Ce-Zn mixed oxide during low-temperature soot combustion processes. We characterized the synthesized catalysts by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N2 adsorption, Raman spectroscopy, oxygen storage capacity (OSC), and scanning and transmission electron microscopy (SEM and TEM). Thermogravimetric and differential thermal analysis (TGA/DTA) confirmed that the catalysts effectively reduced the soot oxidation temperature. The ternary Ce-Zn-La mixed oxide catalyst with Ce/Zn/La atomic ratio of 2:1:0.5 had the highest catalytic activity and promoted soot oxidation at temperatures below 390°C. This indicated that the large number of oxygen vacancies in the catalyst structure generated oxygen species at low temperatures. Raman spectroscopy measurements revealed the presence of oxygen vacancies and lattice defects in Ce-Zn-La samples, which were key parameters concerning the stability and redox properties of the prepared catalysts.

Lanthanoid-Doped Phosphate/Vanadate Mixed Hollow Particles as Ratiometric Luminescent Sensors.

Rare earth (RE) phosphates and vanadates are structurally similar compositions that display distinct but complementary luminescent properties. The properties of these phosphors can be combined in REPO4-REVO4 heterostructures during the development of new sensing technologies for biological applications. This work presents the synthesis of hollow RE phosphate/vanadate colloidal particles and evaluates their applicability as luminescent markers. Hydrothermal treatments of RE hydroxycarbonate particles in the presence of the PO43- and VO43- precursors afforded the final REPO4-REVO4 solids in a two-step template synthesis. We converted precursor hydroxycarbonate particles into the final heterostructures and characterized their structure and morphology. According to our detailed study into the spectroscopic properties of Eu3+-doped particles and their luminescence response to several species, the presence of the phosphate and vanadate phases in a single particle provided different chemical environments and enabled the design of a ratiometric approach to detect H2O2. These results open new perspectives for the development of new intracellular luminescent markers.

Metalloporphyrins immobilized in Fe3O4@SiO2 mesoporous submicrospheres: Reusable biomimetic catalysts for hydrocarbon oxidation.

We successfully immobilized metalloporphyrins (MeP) in mesoporous silica coating magnetite spheres. In this sense, we prepared two different classes of core@shell supports, which comprise aligned (Fe3O4-AM-MeP, MeP=FeP or MnP) and non-aligned (Fe3O4-NM-MeP, MeP=FeP or MnP) mesoporous magnetic structures. X-ray diffractometry and energy dispersive X-ray spectroscopy confirmed the mesoporous nature of the silica shell of the materials. Magnetization measurements, scanning and transmission electron microscopies (SEM/TEM), electrophoretic mobility (ζ-potential), and infrared spectroscopy (FTIR) also confirm the composition and structure of the materials. The catalysts maintained their catalytic activity during nine reaction cycles toward hydrocarbon oxidation processes without detectable catalyst leaching. The catalysis results revealed a biomimetic pattern of cytochrome P450-type enzymes, thus confirming that the prepared materials are can effectively mimic the activity of such groups.

Improved green coffee oil antioxidant activity for cosmetical purpose by spray drying microencapsulation

AbstractThe oil extracted by cold pressing unroasted coffee beans, known as green coffee oil, has been widely used for cosmetic purposes. The objective of this work was to prepare and characterize microcapsules containing green coffee oil and to verify its antioxidant activity under the effect of light, heat and oxygen. The encapsulating material was arabic gum and the microcapsules were obtained by spray drying an oil-in-water emulsion containing green coffee oil. The characterization of the microcapsules was performed by laser diffraction, scanning electron microscopy, differential scanning calorimetry and the antioxidant activity. The antioxidant activity was determined by a modified active oxygen method with light irradiation, heating and oxygen flux. The microparticles were effectively produced by the proposed spray drying method, which resulted in green coffee oil loads of 10 and 30%. The morphological evaluation of microcapsules showed spherical shape with smooth and non-porous surfaces, demonstrating the adequacy of arabic gum as encapsulating material. Calorimetric analysis of individual components and microcapsules with 10 and 30% green coffee oil showed diminished degradation temperatures and enthalpy, suggesting a possible interaction between arabic gum and green coffee oil. The antioxidant activities for pure green coffee oil and its microcapsules with loads of 10 and 30% showed high activity when compared to the reference antioxidant alfa-tocopherol. Microcapsules containing 10 and 30% of oil showed 7-fold and 3-fold increase in antioxidant activity when compared to pure green coffee oil. The new method for antioxidant activity determination proposed here, which applies heat, light and oxygen simultaneously, suggests a high improvement in encapsulated green coffee oil when compared to this active alone. The results showed herein indicate a promising industrial application of this microencapsulated green coffee oil.

Catalytic combustion of soot over ceria-zinc mixed oxides catalysts supported onto cordierite.

Modified substrates as outer heterogeneous catalysts was employed to reduce the soot generated from incomplete combustion of diesel or diesel/biodiesel blends, a process that harms the environment and public health. The unique storage properties of ceria (CeO2) makes it one of the most efficient catalysts available to date. Here, we proposed that ceria-based catalysts can lower the temperature at which soot combustion occurs; more specifically, from 610°C to values included in the diesel exhausts operation range (300-450°C). The sol-gel method was used to synthesize mixed oxide-based catalysts (CeO2:ZnO); the resulting catalysts were deposited onto cordierite substrates. In addition, the morphological and structural properties of the material were evaluated by XRD, BET, TPR-H2, and SEM. Thermogravimetric (TG/DTA) analysis revealed that the presence of the catalyst decreased the soot combustion temperature by 200°C on average, indicating that the oxygen species arise at low temperatures in this situation, promoting highly reactive oxidation reactions. Comparative analysis of soot emission by diffuse reflectance spectroscopy (DRS) showed that catalyst-impregnated cordierite samples efficiently oxidized soot in a diesel/biodiesel stationary motor: soot emission decreased by more than 70%.

Stability of sunscreens containing CePO4: proposal for a new inorganic UV filter.

Inorganic UV filters have become attractive because of their role in protecting the skin from the damage caused by continuous exposure to the sun. However, their large refractive index and high photocatalytic activity have led to the development of alternative inorganic materials such as CePO4 for application as UV filters. This compound leaves a low amount of white residue on the skin and is highly stable. The aim of this study was to evaluate the physical and chemical stability of a cosmetic formulation containing ordinary organic UV filters combined with 5% CePO4, and, to compare it with other formulations containing the same vehicle with 5% TiO2 or ZnO as inorganic materials. The rheological behavior and chemical stability of the formulations containing these different UV filters were investigated. Results showed that the formulation containing CePO4 is a promising innovative UV filter due to its low interaction with organic filters, which culminates in longer shelf life when compared with traditional formulations containing ZnO or TiO2 filters. Moreover, the recognized ability of CePO4 to leave a low amount of white residue on the skin combined with great stability, suggests that CePO4 can be used as inorganic filter in high concentrations, affording formulations with high SPF values.

Effect of the vanadium(V) concentration on the spectroscopic properties of nanosized europium-doped yttrium phosphates.

Nanosized rare earth phosphovanadate phosphors (Y(P,V)O(4):Eu(3+)) have been prepared by applying the organic-inorganic polymeric precursors methodology. Luminescent powders with tetragonal structure and different vanadate concentrations (0%, 1%, 5%, 10%, 20%, 50%, and 100%, with regard to the phosphate content) were then obtained for evaluation of their structural and spectroscopic properties. The solids were characterized by scanning electron microscopy, X-ray diffractometry, vibrational spectroscopy (Raman and infrared), and electronic spectroscopy (emission, excitation, luminescence lifetimes, chromaticity, quantum efficiencies, and Judd-Ofelt intensity parameters). The solids exhibited very intense (5)D(0)→(7)F(J) Eu(3+) transitions, and it was possible to control the luminescent characteristics, such as excitation maximum, lifetime and emission colour, through the vanadium(V) concentration. The observed luminescent properties correlated to the characteristics of the chemical environments around the Eu(3+) ions with respect to the composition of the phosphovanadates. The Eu(3+) luminescence spectroscopy results indicated that the presence of larger vanadium(V) amounts in the phosphate host lattice led to more covalent and polarizable chemical environments. So, besides allowing for control of the luminescent properties of the solids, the variation in the vanadate concentration in the obtained YPO(4):Eu(3+) phosphors enabled the establishment of a strict correlation between the observable spectroscopic features and the chemical characteristics of the powders.

Chlorin photosensitizers sterically designed to prevent self-aggregation.

The synthesis and photophysical evaluation of new chlorin derivatives are described. The Diels-Alder reaction between protoporphyrin IX dimethyl ester and substituted maleimides furnishes endo-adducts that completely prevent the self-aggregation of the chlorins. Fluorescence, resonant light scattering (RLS) and (1)H NMR experiments, as well as X-ray crystallographic have demonstrated that the configurational arrangement of the synthesized chlorins prevent π-stacking interactions between macrocycles, thus indicating that it is a nonaggregating photosensitizer with high singlet oxygen (Φ(Δ)) and fluorescence (Φ(f)) quantum yields. Our results show that this type of synthetic strategy may provide the lead to a new generation of PDT photosensitizers.

Chitosan as a bioadhesive agent between porphyrins and phospholipids in a biomembrane model.

Porphyrins are currently used in photodynamic therapy as photosensitizers. In this paper we studied the interaction of two charged porphyrins, 5, 10, 15, 20-mesotetrakis(N-metyl-4-pyridyl) porphyrin, (TMPyP/chloride salt) cationic, and 5, 10, 15, 20-meso-tetrakis(sulfonatophenyl) porphyrin, (TPPS4/sodium salt) anionic, nanoassembled in phospholipid Langmuir monolayers and Langmuir-Blodgett films. Furthermore, we used chitosan to mediate the interaction between the porphyrins and the model membrane, aiming to understand the role of the polysaccharide in a molecular level. The effect of the interaction of the photosensitizers on the fluidity of the lipid monolayer was investigated by using dilatational surface elasticity. We also used photoluminescence (PL) spectroscopy to identify the porphyrins adsorbed in the phospholipid films. We observed an expansion of the monolayer promoted by the adsorption of the porphyrins into the lipid-air interface which was more pronounced in the case of TMPyP, as a consequence of a strong electrostatic interaction with the anionic monolayer. The chitosan promoted a higher adsorption of the porphyrins on the phospholipid monolayers and enabled the porphyrin to stay in its monomeric form (as confirmed by PL spectroscopy), thus demonstrating that chitosan can be pointed out as a potential photosensitizer delivery system in photodynamic therapy.

Synthesis and study of the photophysical properties of a new Eu3+ complex with 3-hydroxypicolinamide.

This work reports on the synthesis and characterization of a new complex of Eu(3+) with the 3-hydroxypicolinamide ligand (Hhpa). Here we present an approach for obtaining bis[2-carbamoyl(κO)pyridin-3-olato(κO')] lanthanide complexes, which were characterized through elemental analysis, thermal analysis, infrared and photoluminescence spectroscopies (emission, excitation, luminescence lifetimes, quantum efficiencies, Judd-Ofelt parameters and quantum yields). Although hpa can act as a bidentate ligand in different conformations, the results attest for the occurrence of a unique coordination site of low symmetry for the Eu(3+) ions, in which two anionic hpa ligands coordinate the cations through an O/O chelating system. The phosphorescence of the synthesized gadolinium complex provides the energy of the triplet state, which is determined to be at 20,830 cm(-1) over the ground state. This makes the Hhpa ligand very adequate for sensitizing the Eu(3+) luminescence, which leads to a very efficient antenna effect and opens a wide range of applications for the complex in light emitting organic-inorganic devices.

Efficient phosphodiester hydrolysis by luminescent terbium(III) and europium(III) complexes.

The synthesis and structures of two new isostructural mononuclear [Ln(L)(NO(3))(H(2)O)(3)](NO(3))(2) complexes, with Ln = Tb (complex 1) and Eu (complex 2), which display high activity in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate, are reported. These complexes displayed catalytic behavior similar to the mononuclear gadolinium complex [Gd(L)(NO(3))(H(2)O)(3)](NO(3))(2) previously reported by us (Inorg. Chem. 2008, 47, 2919-2921); one hydrolysis reaction in two stages where the diesterase and monoesterase activities could be monitored separately, with the first stage dependent on and the second independent of the complex concentration. Through potentiometric studies, electrospray ionization mass spectrometry (ESI-MS) analysis, and determination of the kinetic behaviors of 1 and 2 in acetonitrile/water solution, the species present in solution could be identified and suggested a dinuclear species, with one hydroxo group, as the most prominent catalyst under mild conditions. The complexes show high activity (k(1) = 7 and 18 s(-1) for 1 and 2, respectively) and catalytic efficiency. Complexes 1 and 2 were found to be active toward the cleavage of plasmid DNA, and complete kinetic studies were carried out. Studies with a radical scavenger (dimethylsulfoxide) confirmed the hydrolytic action of 1 and 2 in the cleavage of DNA. Studies on the incubation of distamycin with plasmid DNA suggested that 1 and 2 are regio-specific, interacting with the minor groove of DNA. These complexes displayed luminescent properties. Complex 1 showed higher emission intensity than 2 due to a more efficient energy transfer between triplet and emission levels of terbium (T --> (5)D(4)), along with nonradiative deactivation mechanisms of the excited states of europium via multiphonon decays and the ligand-to-metal charge transfer state. Lifetime measurements of the (5)D(4) and (5)D(0) excited levels for 1 and 2, respectively, indicated the numbers of coordinated water molecules for the complexes.

Luminescence in colorless, transparent, thermally stable thin films of Eu3+ and Tb3+ beta-diketonates in hybrid inorganic-organic zinc-based sol-gel matrix.

Luminescent zinc-based hybrid inorganic-organic films with rare-earth (RE) complexes have been prepared using a non-alkoxide sol-gel process. The films were fabricated by the dip-coating method starting from zinc acetate dihydrate, rare earth chloride, lactic acid as hydrolytic catalyst, and anhydrous ethanol. The beta-diketones thenoylltrifluoroacetone (Httfa) and dibenzoylmethane (Hdbm) were used as ligands to Eu(3+) and Tb(3+), respectively. After deposition of the first layer, the films were fired at temperatures between 50 and 300 degrees C, in air. Photophysical properties such as excitation, emission and emission, lifetimes were determined for the films obtained in different conditions. Eu(3+)/ttfa and Tb(3+)/dbm films fired at 300 and 250 degrees C, respectively, are still transparent and gave rise to intense emission when excited through the ligand (antenna effect).

Synthesis of phthalocyanines-ALA conjugates: water-soluble compounds with low aggregation.

Syntheses of two water-soluble phthalocyanines (Pc) containing 5-aminolevulinic acid (ALA) linked to the core structure are described. These compounds were prepared by using original functionalizations, and they present remarkable structural and photophysical features, indicating that they could be applied to photodynamic therapy (PDT).

Dextrin-microencapsulated porphyrin: luminescent properties.

Photophysical properties of porphyrins in aqueous solutions are strongly affected by aggregation. One possible solution to this problem is to encapsulate the porphyrin into polymeric spheres, to provide an environment where the photosensitizer can be administered in its monomeric form in such treatments as photodynamic therapy. Here we report the microencapsulation of the meso-tetrakis(4-sulphonatophenyl) porphyrin (TPPS(4)) photosensitizer by the ultrasonic spray-drying technique. The encapsulated TPPS(4) was morphologically characterized by scanning electron microscopy, and its photophysical properties were studied and compared with those of a physical blend of dextrin and TPPS(4). We successfully encapsulated TPPS(4) into dextrin microspheres, and the encapsulated photosensitizer displays higher luminescence intensity than that of the prepared physical blends.