Transformation of Residual Açai Fruit (Euterpe oleracea) Seeds into Porous Adsorbent for Efficient Removal of 2,4-Dichlorophenoxyacetic Acid Herbicide from Waters

Brazil’s production and consumption of açai pulp (Euterpe oleracea) occur on a large scale. Most of the fruit is formed by the pit, which generates countless tons of residual biomass. A new purpose for this biomass, making its consumption highly sustainable, was presented in this study, where activated carbon (AC) was produced with zinc chloride for later use as an adsorbent. AC carbon formed by carbon and with a yield of 28 % was satisfactorily used as an adsorbent in removing the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Removal efficiency was due to the highly porous surface (Vp = 0.467 cm³ g⁻¹; Dp = 1.126 nm) and good surface área (SBET = 920.56 m² g⁻¹). The equilibrium data fit the Sips heterogeneous and homogeneous surface model better. It was observed that the increase in temperature favored adsorption, reaching a maximum experimental capacity of 218 mg g⁻¹ at 328 K. The thermodynamic behavior indicated a spontaneous, favorable, and endothermic behavior. The magnitude of the enthalpy of adsorption was in agreement with the physical adsorption. Regardless of the herbicide concentration, the adsorbent displayed fast kinetics, reaching equilibrium within 120 min. The linear driving force (LDF) model provided a strong statistical match to the kinetic curves. AC with zinc chloride (ZnCl₂), created from leftover açai biomass, is a potential alternative as an adsorbent for treating effluents containing 2,4-D.     

Revisiting the structure of Heliannuol L: A computational approach

Recently, structural elucidation of natural products has undergone a revolution. The combined use of different modern spectroscopic methods has allowed obtaining a complete structural assignment of natural products using small amounts of sample. However, despite the extraordinary ongoing advances in spectroscopy, the mischaracterization of natural products has been and remains a recurrent problem, especially when the substance presents several stereogenic centers. The misinterpretation of nuclear magnetic resonance (NMR) data has resulted in frequent reports addressing structural reassignment. In this context, a great effort has been devoted to developing quantum chemical calculations that simulate NMR parameters accurately, allowing to achieve a more precise spectral interpretation. In this work, we employed a protocol for theoretical calculations of ¹H NMR chemical shifts and coupling constants using density functional theory (DFT), followed by the application of the DP4+ method to revisit the structure of Heliannuol L, a member of the Heliannuol class, isolated from Helianthus annuus. Our results indicate that the originally proposed structure of Heliannuol L needs a stereochemical reassignment, placing the hydroxyl bonded to C10 in the opposite side of the methyl and hydroxyl groups bonded to C7 and C8, respectively.     

The outstanding ability of nanosilica to stabilize dispersions of Nylon 6 droplets in a polypropylene matrix

The effectiveness of hydrophobically modified nanosilica (NS) as interfacial modifying agent for immiscible polymer blends is evaluated. Blends of polypropylene (PP) with 20% of polyamide 6 (PA) and 5% hydrophobic NS were prepared by melt mixing. Compression molded sheets and extruded films were evaluated by scanning electron microscopy, transmission electron microscopy, tensile testing, and rheological measurements. Hydrophobic NS particles strongly reduce the polydispersity and droplet size of the dispersed phase, as a result of their preferential location at the interface. NS promotes outstanding stability of blend dispersion regardless of the processing or post‐processing technique employed. The viscoelastic terminal zone shows a plateau for PP/PA/NS, which corresponds to a suspension‐like behavior. Under large amplitude oscillatory shear, the increment in the non‐linearity parameter Q evidences the interactions between NS and blend components. Therefore, NS is an excellent morphological stabilizer that prevents coalescence, but cannot promote interfacial adhesion between immiscible PP and PA phases. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1567–1579     

Fast single-photon avalanche diode arrays for laser Raman spectroscopy

We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128×128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic.     

Influence of the Sb dopant distribution on far infrared photoconductivity in Ge:Sb blocked impurity band detectors

Extended long wavelength response to 200 μm (50 cm⁻¹) has been observed in Ge:Sb blocked impurity band (BIB) detectors with N_D1×10¹⁶ cm⁻³. The cut-off wavelength increases from 150 μm (65 cm⁻¹) to 200 μm (50 cm⁻¹) with increasing bias. The responsivity at long wavelengths was lower than expected. This can be explained by considering the observed Sb diffusion profile in a transition region between the blocking layer and active layer. BIB modeling is presented which indicates that this Sb concentration profile increases the electric field in the transition region and reduces the field in the blocking layer. The depletion region consists partially of the transition region between the active and blocking layer, which could contribute to the reduced long wavelength response. The field spike at the interface is the likely cause of breakdown at a lower bias than expected.     

Effects of synthesis variables on the magnetic properties of CoFe2O4 nanoparticles

Cobalt ferrite nanoparticles (CoFe₂O₄) have been synthesized using precipitation in water solution with polyethylene glycol as surfactant. Influence of various synthesis variables included pH, reaction time and annealing temperature on the magnetic properties and particle sizes has also been studied. Structural identification of the samples was carried out using Thermogravimetric and Differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, High resolution transmission electron microscopy. Vibrating sample magnetometer was used for the magnetic investigation of the samples. Magnetic properties of nanoparticles show strong dependence on the particle size. The magnetic properties increase with pH of the precipitating medium and annealing temperature while the coercivity goes through a maximum, peaking at around 25 nm.     

Copper content of vineyard soils at Sremski Karlovci (Vojvodina Province,Serbia) as affected by the use of copper-based fungicides

The present study investigated the copper content of nine vineyard plots soils and four control plots as affected by the application of copper-based fungicides. The study was carried out at the site of Sremski Karlovci in the Serbian province of Vojvodina. The results showed that Cu soil concentrations are increased at the site and that there is a tendency towards soil contamination by this element. Of the 27 total samples studied, only one had Cu concentration above the maximum allowable concentration of 100?mg?kg^?1. That sample's concentration was 111.7?mg?kg^?1. All the samples from the 0–15?cm layer had copper levels that were above the critical value of 60?mg?kg^?1. The mean value of the samples was 79.4?mg?kg^?1, contrasting with the background concentration of 19.8?mg?kg^?1. The results obtained for the studied vineyard soils indicate that these soils are potentially at risk and call for reduced application of Cu-based fungicides along with soil monitoring.     

FWM in silicon nanocrystal-based sandwiched slot waveguides

The observation of four-wave mixing in a 6 mm long sandwiched slot waveguide filled with Si-nc/SiO₂ is reported for optical powers usually employed in telecommunication systems. A −47 dB conversion efficiency is measured in fabricated waveguides for input signal powers around 12 dBm on chip and a waveguide length of 6 mm. Furthermore, the calculated non-linear coefficient is found to be n₂ = 2.67 × 10⁻¹⁷ m²/W. It is also expected that, by using longer waveguides, it would be possible to achieve wavelength conversion.     

The effect of Er3+ and Sm3+ on phase separation and crystallization in Na2O/K2O/BaF2/BaO/Al2O3/SiO2 glasses

Thermal annealing of Sm⁺³ or Er⁺³ doped Na₂O/K₂O/BaF₂/BaO/Al₂O₃/SiO₂ glasses led to the precipitation of nanocrystalline BaF₂. The mean crystallite sizes were in the range from 9 to 15 nm as shown by XRD line broadening. Whereas glasses without rare earth oxides showed crystallites homogenously dispersed in the amorphous matrix, those doped with 0.05 mol% ErF₃ or SmF₃ showed highly agglomerated crystals. The latter was due to droplet phase separation in the rare earth doped glasses as proved by transmission electron microscopy while in the undoped glasses phase separation did not occur. Furthermore, the size of the droplets depended on the BaO-concentration. Fluorescence emission spectra of a samarium doped sample showed higher intensities than in the glasses they were prepared from.     

Effect of Pluronic P103 Concentration on the Simple Synthesis of Ag and Au Nanoparticles and Their Application in Anatase-TiO2 Decoration for Its Use in Photocatalysis

Silver and gold nanoparticles were synthesized under environmentally-friendly reaction conditions by using a biodegradable copolymer and water as a solvent. The triblock copolymer Pluronic P103 was utilized as a stabilizing agent or soft template to produce Ag and Au nanoparticles (NPs) of different sizes. Moreover, in the synthesis of Au NPs, the polymer acted as a reducing agent, decreasing the number of reagents used and consequently the residues produced, hence, rendering the procedure less complicated. It was observed that as the concentration of the polymer increased, the size of the metallic NPs augmented as well. However, AgNPs and AuNPs prepared with 1 and 10 wt% Pluronic P103, respectively, showed a significant decrease in particle size due to the presence of polymeric soft templates. The hybrid materials (metal/polymer) were characterized by UV-Vis spectroscopy, DLS, and TEM. The pre-synthesized nanoparticles were employed to decorate anatase-TiO₂, and the composites were characterized by DRS, XRD, BET surface area measurements, the TEM technique with the EDS spectrum, and XPS spectroscopy to demonstrate NPs superficial incorporation. Finally, methylene blue was used as a probe molecule to evidence the effect of NPs decoration in its photocatalytic degradation. The results showed that the presence of the NPs positively affected methylene blue degradation, achieving 96% and 97% removal by utilizing TAg0.1 and TAu10, respectively, in comparison to bare anatase-TiO₂ (77%).