An efficient method for the carboxylation of few-wall carbon nanotubes with little damage to their sidewalls

We report a novel method that is able to efficiently functionalize carbon nanotubes (few-walled: from 1 to 6 layers and multiwalled) with a high yield of carboxyl groups, based on treatments with H₂O₂ in the presence of UV light. The amount of carboxylic groups was quantified by X-ray photoelectron spectroscopy and back-titration, showing both measurements reasonable agreement. According to the zeta potential values and to the amount of suspended nanotubes, we demonstrate that the method is able to produce uniform and stable suspensions of carbon nanotubes in water. With the aid of scanning and transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy, we show that the surfaces of the tubes are not damaged by the treatment and that the functionalized tubes have an enhanced reactivity toward oxygen. This route is efficient and could now be used to fabricate polymer composites using few-walled and multiwalled carbon nanotubes.O. Martín and J. Baselga acknowledge support from Ministerio de Ciencia e Innovación (Spain) under grants MAT2010-17091 and MAT2009-06296E. M. Terrones acknowledges support from the Research Center for Exotic Nanocarbons, Japan regional Innovation Strategy Program by the Excellence, JST. T. Blanco acknowledges support from CDTI under the project NANOMULFUN (SAE-20081035)

Morphological, chemical and electrical characterization of a family of commercial nanofiltration polyvinyl alcohol coated polypiperazineamide membranes

Three AFC membranes from PCI, of the thin film composite (TFC) nanofiltration type, have been characterized by using XPS, AFM, Contact angles, Zeta potential and permeation experiments. This plethora of complimentary methods portrays a deep and exhaustive description of these membranes that could be used to tune fabrication and modification of nanofiltration membranes to get better properties. Morphological properties, including porosity, water permeability, fractal dimension, Wenzel parameter and roughness, correlate well with pore sizes. While functional characteristics as, for example wettability correlate well with the O/N ratio. Increasing O/N ratios should be interpreted as caused by increasing PVA coverages. The charge on the membrane's surface is ordered in a different way for different pH but are quite similar anyway. The effect of charges on retention of 1:1, 1:2 and 2:1 salts (as tested with NaCl, Na2SO4 and CaCl2) increases with increasing O/N and wettability. Consequently, the trend of salt retentions can be explained in terms of the PVA coverage and the details of the amphoteric behavior of the three AFC membranes studied.This work was supported by the Spanish Ministry of through project MAT2016-76413-C2-1-R and the Regional Government of Castilla y León and the EU-FEDER (CLU2017-09, UIC082 and VA088G19)

Morphological, Electrical, and Chemical Characteristics of Poly(sodium 4-styrenesulfonate) Coated PVDF Ultrafiltration Membranes after Plasma Treatment

A commercial ultrafiltration (UF) membrane (HFM-183 de Koch Membrane Systems) made of poly(vinylidene fluoride) (PVDF), was recovered with a negatively-charged polyelectrolyte (poly(sodium 4-styrenesulfonate)) (PSS), and the effects on its electric, chemical, and morphological properties were analyzed. Atomic force microscopy (AFM), liquid-liquid displacement porometry, Electrical Impedance Spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to investigate the modifications induced by the deposition of PSS on the PVDF positively-charged membrane and after its treatment by a radio frequency Ar-plasma. These techniques confirmed a real deposition and posterior compaction of PSS with increasing roughness and decreasing pore sizes. The evolution of the electric resistances of the membranes confirmed crosslinking and compaction with shielding of the sulfonated groups from PSS. In this way, a membrane with a negatively-charged active layer and a pore size which was 60% lower than the original membrane was obtained. The composition of the additive used by manufacturers to modify PVDF to make it positively charged was obtained by different procedures, all of which depended upon the results of X-ray photoelectron spectroscopy, leading to fairly consistent results. This polymer, carrying positive charges, contains quaternary nitrogen, as confirmed by XPS. Moreover, Raman spectroscopy confirmed that PVDF changes from mostly the β to the α phase, which is more stable as a substrate for the deposited PSS. The aim of the tested modifications was to increase the retention of divalent anions without reducing permeability.Fil: Sandoval Olvera, Ivette G.. Universidad de Guanajuato; MéxicoFil: González Muñoz, Pilar. Universidad de Guanajuato; MéxicoFil: Diaz, Dario Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Maroto Valiente, Ángel. Universidad de Guanajuato; MéxicoFil: Ochoa, Nelio Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Carmona, Francisco J.. Universidad de Extremadura; EspañaFil: Palacio, Laura. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Calvo, José I.. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Hernández, Antonio. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Ávila Rodríguez, Mario. Universidad de Guanajuato; MéxicoFil: Prádanos, Pedro. Universidad de Valladolid. Facultad de Ciencias; Españ

Spectroscopic study of rock art paintings from the Cueva de Tito Bustillo (Ribadesella, Asturias)

Tres pictografías de la Cueva de Tito Bustillo se han estudiado por microespectroscopía Raman, espectroscopía infrarroja, difracción de rayos X, espectroscopía fotoelectrónica y microscopía electrónica y espectrometría de dispersión de energía de rayos X. Todas ellas se relacionan con las fases antiguas de la decoración de la cueva. Hematites de dos tamaños de grano (<1 y <10 µm) es el principal componente de las pictografías. Hidroxiapatito, anatasa y carbón amorfo aparecen como componentes adicionales en algunas de ellas. Calcita, cuarzo-α y minerales arcillosos se usan como materiales de relleno. No se han detectado aglutinantes orgánicos. Considerando los componentes principales, tamaño de grano y fases secundarias de los materiales pictóricos, se concluye que la veta de ocre de la cueva no se usó para hacer las pinturas de esta cronología. Dos de las pictografías analizadas parecen haber sido pintadas con un mismo tipo de pintura.Three pictographs from the Tito Bustillo cave have been studied by Raman microspectroscopy, infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X-ray spectrometry. All the samples can be associated with the oldest cave decoration phases. Haematite of two granular sizes (<1 and <10 µm) is the main component of the pictographs. Hydroxyapatite, anatase and amorphous carbon appear as additional components in some of them. Calcite, α-quartz and clay minerals are used as filler materials. No organic binders have been detected. Considering the main components, granular size, and secondary phases of the pigments it is concluded that the ochre quarry of the cave was not used to make the paintings of this chronology. Two of the analysed figures of this cave seem to have been painted with the same type of paint

3D solid supported inter-polyelectrolyte complexes obtained by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate)

This work addresses the formation and the internal morphology of polyelectrolyte layers obtained by the layer-by-layer method. A multimodal characterization showed the absence of stratification of the films formed by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). Indeed the final organization might be regarded as threedimensional solid-supported inter-polyelectrolyte films. The growth mechanism of the multilayers, followed using a quartz crystal microbalance, evidences two different growth trends, which show a dependency on the ionic strength due to its influence onto the polymer conformation. The hydration state does not modify the multilayer growth, but it contributes to the total adsorbed mass of the film. The water associated with the polyelectrolyte films leads to their swelling and plastification. The use of X-ray photoelectron spectroscopy has allowed for deeper insights on the internal structure and composition of the polyelectrolyte multilayers

First Phenol Carboxylation with CO2 on Carbon Nanostructured C@Fe-Al2O3 Hybrids in Aqueous Media under Mild Conditions

Novel hybrid materials with integrated catalytic properties and hydrophobic response, C@Fe-Al2O3 hybrid samples, were presented and tested as catalysts for phenol reaction in aqueous solutions at atmospheric pressure and mild temperature conditions, using CO2 as a feedstock. A series of carbon-coated gamma-alumina pellets (C@Fe-Al2O3) were synthesized and characterized by TGA, Brunauer-Emmett-Teller (BET) method, Raman spectroscopy, SEM, TEM, and XPS in order to get comprehensive knowledge of their properties at the nanoscale and relate them with their catalytic behavior. The results obtained correlated their catalytic activities with their carbon surface compositions. The application of these materials as active catalysts in the Kolbe-Schmitt reaction for CO2 conversion in aqueous media was proposed as an alternative reaction for the valorization of exhausts industrial effluents. In these early tests, the highest conversion of phenol was observed for the hybrid samples with the highest graphitic characteristic and the most hydrophobic behavior. Carboxylation products such as benzoic acid, p-hydroxybenzoic acid, and salicylic acid, have been identified under these experimental conditions