Rheological behavior of thermoreversible k-carrageenan/nanosilica gels

The rheological behavior of silica/κ-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.FCT - PTDC/QUI/67712/2006FEDE

"Soft and rigid" dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate

Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiols (1, 2-ethanedithiol (ED) or 4, 4'-biphenyldithiol) to create the thiol (-SH) groups on polymer surface. This "short" dithiols are expected to be fixed via one of -SH groups to radicals created by the plasma treatment on the PET surface. "Free" -SH groups are allowed to interact with Au nanoparticles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrokinetic analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the modified PET were studied by atomic force microscopy (AFM). The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on the modified surface only in the case of biphenyldithiol pretreatment. The possible explanation is that the "flexible" molecule of ethanedithiol is bounded to the activated PET surface with both -SH groups. On the contrary, the "rigid" molecule of biphenyldithiol is bounded via only one -SH group to the modified PET surface and the second one remains "free" for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface

A review on development and application of plant-based bioflocculants and grafted bioflocculants

Flocculation is extensively employed for clarification through sedimentation. Application of eco-friendly plant-based bioflocculants in wastewater treatment has attracted significant attention lately with high removal capability in terms of solids, turbidity, color, and dye. However, moderate flocculating property and short shelf life restrict their development. To enhance the flocculating ability, natural polysaccharides derived from plants are chemically modified by inclusion of synthetic, nonbiodegradable monomers (e.g., acrylamide) onto their backbone to produce grafted bioflocculants. This review is aimed to provide an overview of the development and flocculating efficiencies of plant-based bioflocculants and grafted bioflocculants for the first time. Furthermore, the processing methods, flocculation mechanism, and the current challenges are discussed. All the reported studies about plant-derived bioflocculants are conducted under lab-scale conditions in wastewater treatment. Hence, the possibility to apply natural bioflocculants in food and beverage, mineral, paper and pulp, and oleo-chemical and biodiesel industries is discussed and evaluated

Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents

A new electronic tongue to monitor the presence of glyphosate (a non-selective systemic herbicide) has been developed. It is based on pulse voltammetry and consists in an array of three working electrodes (Pt, Co and Cu) encapsulated on a methacrylate cylinder. The electrochemical response of the sensing array was characteristic of the presence of glyphosate in buffered water (phosphate buffer 0.1 mol·dm-3, pH 6.7). Rotating disc electrode (RDE) studies were carried out with Pt, Co and Cu electrodes in water at room temperature and at pH 6.7 using 0.1 mol·dm-3 of phosphate as a buffer. In the presence of glyphosate, the corrosion current of the Cu and Co electrodes increased significantly, probably due to the formation of Cu2+ or Co2+ complexes. The pulse array waveform for the voltammetric tongue was designed by taking into account some of the redox processes observed in the electrochemical studies. The PCA statistical analysis required four dimensions to explain 95% of variance. Moreover, a two-dimensional representation of the two principal components differentiated the water mixtures containing glyphosate. Furthermore, the PLS statistical analyses allowed the creation of a model to correlate the electrochemical response of the electrodes with glyphosate concentrations, even in the presence of potential interferents such as humic acids and Ca2+. The system offers a PLS prediction model for glyphosate detection with values of 098, -2.3 ¿ 10-5 and 0.94 for the slope, the intercept and the regression coefficient, respectively, which is in agreement with the good fit between the predicted and measured concentrations. The results suggest the feasibility of this system to help develop electronic tongues for glyphosate detection. © 2012 by the authors; licensee MDPI, Basel, Switzerland.Financial support from the Spanish Government (Project MAT2009-14564-C04-01 and PCI-Mediterraneo A/024590/09/A/ 03044/10), the Generalitat Valenciana (Project PROMETEO/2009/016), the UPV (project PAID-05-10) and its Centre de Cooperacio al Desenvolupament (Programa ADSIDEO-COOPERACIO 2010) is gratefully acknowledged.Bataller Prats, R.; Campos Sánchez, I.; Laguarda Miró, N.; Alcañiz Fillol, M.; Soto Camino, J.; Martínez Mañez, R.; Gil Sánchez, L.... (2012). Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents. Sensors. 12:17553-17568. https://doi.org/10.3390/s121217553S175531756812Sierra, E. V., Méndez, M. A., Sarria, V. M., & Cortés, M. T. (2008). Electrooxidación de glifosato sobre electrodos de níquel y cobre. 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Determination of glyphosate, glyphosate metabolites, and glufosinate in human serum by gas chromatography–mass spectrometry. Journal of Chromatography B, 875(2), 509-514. doi:10.1016/j.jchromb.2008.10.003De Llasera, M. P. G., Gómez-Almaraz, L., Vera-Avila, L. E., & Peña-Alvarez, A. (2005). Matrix solid-phase dispersion extraction and determination by high-performance liquid chromatography with fluorescence detection of residues of glyphosate and aminomethylphosphonic acid in tomato fruit. Journal of Chromatography A, 1093(1-2), 139-146. doi:10.1016/j.chroma.2005.07.063Coutinho, C. F. B., Coutinho, L. F. M., Mazo, L. H., Nixdorf, S. L., & Camara, C. A. P. (2008). Rapid and direct determination of glyphosate and aminomethylphosphonic acid in water using anion-exchange chromatography with coulometric detection. Journal of Chromatography A, 1208(1-2), 246-249. doi:10.1016/j.chroma.2008.09.009Yoshioka, N., Asano, M., Kuse, A., Mitsuhashi, T., Nagasaki, Y., & Ueno, Y. (2011). Rapid determination of glyphosate, glufosinate, bialaphos, and their major metabolites in serum by liquid chromatography–tandem mass spectrometry using hydrophilic interaction chromatography. Journal of Chromatography A, 1218(23), 3675-3680. doi:10.1016/j.chroma.2011.04.021SILVA, A. S., TÓTH, I. V., PEZZA, L., PEZZA, H. R., & LIMA, J. L. F. C. (2011). Determination of Glyphosate in Water Samples by Multi-pumping Flow System Coupled to a Liquid Waveguide Capillary Cell. Analytical Sciences, 27(10), 1031. doi:10.2116/analsci.27.1031Amelin, V. G., Bol’shakov, D. S., & Tretiakov, A. V. (2012). Determination of glyphosate and aminomethylphosphonic acid in surface water and vegetable oil by capillary zone electrophoresis. Journal of Analytical Chemistry, 67(4), 386-391. doi:10.1134/s1061934812020037Da Silva, A. S., Fernandes, F. C. B., Tognolli, J. O., Pezza, L., & Pezza, H. R. (2011). A simple and green analytical method for determination of glyphosate in commercial formulations and water by diffuse reflectance spectroscopy. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 79(5), 1881-1885. doi:10.1016/j.saa.2011.05.081Chiu, H.-Y., Lin, Z.-Y., Tu, H.-L., & Whang, C.-W. (2008). Analysis of glyphosate and aminomethylphosphonic acid by capillary electrophoresis with electrochemiluminescence detection. Journal of Chromatography A, 1177(1), 195-198. doi:10.1016/j.chroma.2007.11.042Jin, J., Takahashi, F., Kaneko, T., & Nakamura, T. (2010). Characterization of electrochemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with glyphosate as coreactant in aqueous solution. Electrochimica Acta, 55(20), 5532-5537. doi:10.1016/j.electacta.2010.04.031Yang, G., Xu, X., Shen, M., Wang, W., Xu, L., Chen, G., & Fu, F. (2009). Determination of organophosphorus pesticides by capillary electrophoresis-inductively coupled plasma mass spectrometry with collective sample-introduction technique. ELECTROPHORESIS, 30(10), 1718-1723. doi:10.1002/elps.200800387Oliveira, G. C., Moccelini, S. K., Castilho, M., Terezo, A. J., Possavatz, J., Magalhães, M. R. L., & Dores, E. F. G. C. (2012). Biosensor based on atemoya peroxidase immobilised on modified nanoclay for glyphosate biomonitoring. Talanta, 98, 130-136. doi:10.1016/j.talanta.2012.06.059Songa, E. A., Somerset, V. S., Waryo, T., Baker, P. G. L., & Iwuoha, E. I. (2009). Amperometric nanobiosensor for quantitative determination of glyphosate and glufosinate residues in corn samples. Pure and Applied Chemistry, 81(1), 123-139. doi:10.1351/pac-con-08-01-15Khenifi, A., Derriche, Z., Forano, C., Prevot, V., Mousty, C., Scavetta, E., … Tonelli, D. (2009). Glyphosate and glufosinate detection at electrogenerated NiAl-LDH thin films. Analytica Chimica Acta, 654(2), 97-102. doi:10.1016/j.aca.2009.09.023Sánchez-Bayo, F., Hyne, R. V., & Desseille, K. L. (2010). An amperometric method for the detection of amitrole, glyphosate and its aminomethyl-phosphonic acid metabolite in environmental waters using passive samplers. Analytica Chimica Acta, 675(2), 125-131. doi:10.1016/j.aca.2010.07.013Aquino Neto, S., & de Andrade, A. R. (2009). Electrooxidation of glyphosate herbicide at different DSA® compositions: pH, concentration and supporting electrolyte effect. Electrochimica Acta, 54(7), 2039-2045. doi:10.1016/j.electacta.2008.07.019Méndez, M. A., Súarez, M. F., Cortés, M. T., & Sarria, V. M. (2007). Electrochemical properties and electro-aggregation of silver carbonate sol on polycrystalline platinum electrode and its electrocatalytic activity towards glyphosate oxidation. Electrochemistry Communications, 9(10), 2585-2590. doi:10.1016/j.elecom.2007.08.008COUTINHO, C., SILVA, M., CALEGARO, M., MACHADO, S., & MAZO, L. (2007). Investigation of copper dissolution in the presence of glyphosate using hydrodynamic voltammetry and chronoamperometry. Solid State Ionics, 178(1-2), 161-164. doi:10.1016/j.ssi.2006.10.027Songa, E. A., Arotiba, O. A., Owino, J. H. O., Jahed, N., Baker, P. G. L., & Iwuoha, E. I. (2009). Electrochemical detection of glyphosate herbicide using horseradish peroxidase immobilized on sulfonated polymer matrix. Bioelectrochemistry, 75(2), 117-123. doi:10.1016/j.bioelechem.2009.02.007Bratskaya, S., Golikov, A., Lutsenko, T., Nesterova, O., & Dudarchik, V. (2008). Charge characteristics of humic and fulvic acids: Comparative analysis by colloid titration and potentiometric titration with continuous pK-distribution function model. Chemosphere, 73(4), 557-563. doi:10.1016/j.chemosphere.2008.06.014De Paolis, F., & Kukkonen, J. (1997). Binding of organic pollutants to humic and fulvic acids: Influence of pH and the structure of humic material. Chemosphere, 34(8), 1693-1704. doi:10.1016/s0045-6535(97)00026-xWang, S., Hu, J., Li, J., & Dong, Y. (2009). Influence of pH, soil humic/fulvic acid, ionic strength, foreign ions and addition sequences on adsorption of Pb(II) onto GMZ bentonite. Journal of Hazardous Materials, 167(1-3), 44-51. doi:10.1016/j.jhazmat.2008.12.079Chen, C., & Wang, X. (2007). Sorption of Th (IV) to silica as a function of pH, humic/fulvic acid, ionic strength, electrolyte type. Applied Radiation and Isotopes, 65(2), 155-163. doi:10.1016/j.apradiso.2006.07.003Heineke, D., Franklin, S. J., & Raymond, K. N. (1994). Coordination Chemistry of Glyphosate: Structural and Spectroscopic Characterization of Bis(glyphosate)metal(III) Complexes. Inorganic Chemistry, 33(11), 2413-2421. doi:10.1021/ic00089a017Woertz, K., Tissen, C., Kleinebudde, P., & Breitkreutz, J. (2010). Performance qualification of an electronic tongue based on ICH guideline Q2. Journal of Pharmaceutical and Biomedical Analysis, 51(3), 497-506. doi:10.1016/j.jpba.2009.09.029Vlasov, Y., Legin, A., & Rudnitskaya, A. (2002). Electronic tongues and their analytical application. Analytical and Bioanalytical Chemistry, 373(3), 136-146. doi:10.1007/s00216-002-1310-2Masot, R., Alcañiz, M., Fuentes, A., Schmidt, F. C., Barat, J. M., Gil, L., … Soto, J. (2010). Design of a low-cost non-destructive system for punctual measurements of salt levels in food products using impedance spectroscopy. Sensors and Actuators A: Physical, 158(2), 217-223. doi:10.1016/j.sna.2010.01.010Campos, I., Alcañiz, M., Aguado, D., Barat, R., Ferrer, J., Gil, L., … Vivancos, J.-L. (2012). A voltammetric electronic tongue as tool for water quality monitoring in wastewater treatment plants. Water Research, 46(8), 2605-2614. doi:10.1016/j.watres.2012.02.029Campos, I., Masot, R., Alcañiz, M., Gil, L., Soto, J., Vivancos, J. L., … Martínez-Mañez., R. (2010). Accurate concentration determination of anions nitrate, nitrite and chloride in minced meat using a voltammetric electronic tongue. Sensors and Actuators B: Chemical, 149(1), 71-78. doi:10.1016/j.snb.2010.06.028García-Breijo, E., Barat, J. M., Torres, O. L., Grau, R., Gil, L., Ibáñez, J., … Fraile, R. (2008). Development of a puncture electronic device for electrical conductivity measurements throughout meat salting. Sensors and Actuators A: Physical, 148(1), 63-67. doi:10.1016/j.sna.2008.07.013Gil, L., Barat, J. M., Garcia-Breijo, E., Ibañez, J., Martínez-Máñez, R., Soto, J., … Toldrá, F. (2008). Fish freshness analysis using metallic potentiometric electrodes. Sensors and Actuators B: Chemical, 131(2), 362-370. doi:10.1016/j.snb.2007.11.052Labrador, R. H., Masot, R., Alcañiz, M., Baigts, D., Soto, J., Martínez-Mañez, R., … Barat, J. M. (2010). Prediction of NaCl, nitrate and nitrite contents in minced meat by using a voltammetric electronic tongue and an impedimetric sensor. 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Hierarchy of hybrid materials — the place of inorganics-in-organics in it, their composition and applications

Hybrid materials, or hybrids incorporating both organic and inorganic constituents, are emerging as a very potent and promising class of materials due to the diverse, but complementary nature of the properties inherent of these different classes of materials. The complementarity leads to a perfect synergy of properties of desired material and eventually an end-product. The diversity of resultant properties and materials used in the construction of hybrids, leads to a very broad range of application areas generated by engaging very different research communities. We provide here a general classification of hybrid materials, wherein organics–in-inorganics (inorganic materials modified by organic moieties) are distinguished from inorganics–in–organics (organic materials or matrices modified by inorganic constituents). In the former area, the surface functionalization of colloids is distinguished as a stand-alone sub-area. The latter area—functionalization of organic materials by inorganic additives—is the focus of the current review. Inorganic constituents, often in the form of small particles or structures, are made of minerals, clays, semiconductors, metals, carbons, and ceramics. They are shown to be incorporated into organic matrices, which can be distinguished as two classes: chemical and biological. Chemical organic matrices include coatings, vehicles and capsules assembled into: hydrogels, layer-by-layer assembly, polymer brushes, block co-polymers and other assemblies. Biological organic matrices encompass bio-molecules (lipids, polysaccharides, proteins and enzymes, and nucleic acids) as well as higher level organisms: cells, bacteria, and microorganisms. In addition to providing details of the above classification and analysis of the composition of hybrids, we also highlight some antagonistic yin-&-yang properties of organic and inorganic materials, review applications and provide an outlook to emerging trends

Chitosan and Its Derivatives as Highly Efficient Polymer Ligands

The polyfunctional nature of chitosan enables its application as a polymer ligand not only for the recovery, separation, and concentration of metal ions, but for the fabrication of a wide spectrum of functional materials. Although unmodified chitosan itself is the unique cationic polysaccharide with very good complexing properties toward numerous metal ions, its sorption capacity and selectivity can be sufficiently increased and turned via chemical modification to meet requirements of the specific applications. In this review, which covers results of the last decade, we demonstrate how different strategies of chitosan chemical modification effect metal ions binding by O-, N-, S-, and P-containing chitosan derivatives, and which mechanisms are involved in binding of metal cation and anions by chitosan derivatives