Physicochemical Characterization of a Cellulosic Film Modified with Two Room-Temperature Ionic Liquids

Changes in the physicochemical characteristics of a regenerated cellulose (RC) film due to a surface modification with room-temperature ionic liquids (ILs) are determined. Two ILs (1-butyl-3-metylimidazolium hexafluorophosphate and tricaprylmethylammonium chloride) were selected, and film surface modification was performed by a dip-coating process (1 h) in the corresponding IL. The surface characterization of the RC/IL films was carried out by XPS at various take-off angles (from 15° to 75°), while the modification of mechanical properties was established by tensile analysis, obtaining a significant increase for the Young modulus of both RC/IL films when compared with the RC-support. Optical characteristics of the RC/IL films were determined by transmittance and reflectance measurements for wavelengths covering visible and near-infrared regions, while impedance spectroscopy (IS) measurements allow us to estimate the electrical changes in the RC/IL films. These results show the high transmittance of both RC/IL films (>90%) with slight differences depending on the IL in both optical regions, while the IS data analysis indicated a conductivity reduction and dielectric constant increase in the dielectric constant for both eco-friendly RC/IL filmsPartial funding for open access charge: Universidad de Málag

Optical characterization of ALD-coated nanoporous alumina structures: effect of sample geometry or coated layer material

Optical characterization of nanoporous alumina-based structures (NPA-bSs), obtained by ALD deposition of a thin conformal SiO2 layer on two alumina nanosupports with different geometrical parameters (pore size and interpore distance), was performed by two noninvasive and nondestructive techniques such as spectroscopic ellipsometry (SE) and photoluminescence (Ph) spectra. SE measurements allow us to estimate the refraction index and extinction coefficient for the studied samples and their dependence with wavelength for the 250–1700 nm interval, showing the effect of sample geometry and cover-layer material (SiO2, TiO2, or Fe2O3), which significantly affect the oscillatory character of both parameters, as well as changes associated with the light incidence angle, which are attributed to surface impurities and inhomogeneity. Photoluminescence curves exhibit a similar shape independently of sample pore-size/porosity, but they seem to affect intensity values. This analysis shows the potential application of these NPA-bSs platforms to nanophotonics, optical sensing, or biosensing.Partial funding for open access charge: Universidad de Málag

Modification of the Physical Properties of a Nafion Film Due to Inclusion of n-Dodecyltriethylammonium Cation: Time Effect.

This study investigates the effects of modifying commercial Nafion-212 thin films with dodecyltriethylammonium cation (DTA+) on their electrical resistance, elastic modulus, light transmission/reflection and photoluminescence properties. The films were modified through a proton/cation exchange process for immersion periods ranging from 1 to 40 h. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the crystal structure and surface composition of the modified films. The electrical resistance and the different resistive contributions were determined via impedance spectroscopy. Changes in the elastic modulus were evaluated using stress–strain curves. Additionally, optical characterization tests, including light/reflection (250–2000 nm) and photoluminescence spectra, were also performed on both unmodified and DTA+-modified Nafion films. The results reveal significant changes in the electrical, mechanical and optical properties of the films, depending on the exchange process time. In particular, the inclusion of the DTA+ into the Nafion structure improved the elastic behavior of the films by significantly decreasing the Young modulus. Furthermore, the photoluminescence of the Nafion films was also enhanced. These findings can be used to optimize the exchange process time to achieve specific desired properties.Partial funding for open access charge: Universidad de Málag

Influence of TiO2-Coating Layer on Nanoporous Alumina Membranes by ALD Technique

Geometrical, chemical, optical and ionic transport changes associated with ALD of TiO2-coating on the porous structure of two nanoporous alumina membranes (NPAMs), which were obtained by the two-step aluminum anodization method but with different pore size and porosity, are presented. Chemical and morphological changes were determined by analyzing XPS spectra and SEM images, showing practically total coverage of the NPAMs surface and leading to a reduction in the geometrical parameters of both samples, while SAED and high resolution TEM measurements allowed us to determine the crystalline structure and thickness of the TiO2-coating, with the latter confirmed by depth-profile XPS analysis. Spectroscopic ellipsometry measurements were also carried out in order to detect changes in characteristic optical parameters (refractive index, n, and extinction coefficient, k), due to the TiO2-coating of NPAMs. Considering the common application of NPAMs in solute/ion diffusion processes, the effect of the TiO2-coverage on electrochemical parameters was analyzed by measuring the concentration potential with a typical model electrolyte (KCl solutions), leading to an increase of the electropositive character for both kinds of samples

Chemical and electrochemical characterization of Nafion containing silver nanoparticles in stripe-like distribution

The particular chemical structure of Nafion with nanostructured and segregated hydrophilic and hydrophobic domains enables its use as a model structure for the manufacture of polymer–Metal nanocomposites. Among such nanocomposites, samples of Nafion-117 containing Ag-NPs of ca.10 nm prepared by Intermatrix Synthesis exhibited a particular distribution in the form of stripes, a regularpattern that could reveal the real morphology of the polymer. To evaluate the potential application of this engineered material (e.g.in electrochemical devices), these new nanocomposite membranes were characterized by different techniques: microscopic, surface chemical analysis, mechanical and electrical/electrochemical. X-ray (XRD and XPS) analyses combined with synchrotron experiments (XANES) were used to determine the chemical speciation of Ag in the membrane. Membrane potential and impedance spectroscopy measurements showed that such Ag-NPs did not hinder the diffusive transport of protons in the membrane bulk, moreover, they slightly reduced the electrical resistance in fully hydrated state samples. The mechanical evaluation of the nanocomposite evidenced a reduction of the elastic character when compared with the unmodified Nafion-117 samplePostprint (author's final draft

Caracterización electroquímica fisicoquímica de un nanomaterial híbrido Nafion/Ag-NPs

La particular estructura química de la matriz perfluorosulfónica del Nafion, con dominios hidrofílicos e hidrofóbicos segregados formando canales nanoscópicos, ha dado pie a su uso como modelo de estructura para la fabricación de nanocompuestos polímero-metal mediante el crecimiento de nanopartículas metálicas en su interior. En particular, mediante la técnica de síntesis intermatrical se ha conseguido el crecimiento de nanopartículas de plata (de un tamaño medio próximo a los 10 nm), las cuales presentan una distribución particular en forma de líneas casi paralelas, que difiere de la distribución más habitual de mayor concentración en la superficie. Para evaluar posibles aplicaciones de este nuevo material se ha realizado su caracterización mediante diferentes técnicas: microscop1ca, análisis químico superficial, mecánica, eléctrica/electroquímica. Los resultados obtenidos muestran que la presencia de nanopartículas no parece afectar significativamente al transporte de protones en la membrana, pero sí modifican la superficie de la misma. Además, la resistencia mecánica del nuevo material es inferior a la del Nafion no modificado debido a la interacción de las partículas con las cadenas de polímero. También se ha observado que algunas de estas propiedades varían de forma importante en/unción del grado de hidratación de la muestra. The particular chemical structure of Nafion, a perfluorosulfonic matrix with segregated hydrophilic and hydrophobic domains forming nanoscale channels, has led to its use as a model structure for the manufacture of polymer-metal nanocomposites by growing in it metal nanoparticles. in particular, using the technique of intermatrix synthesis, the growth of silver nanoparticles (with an average diameter close to 10 nm) has been achieved Moreover, samples exhibit a particular distribution of such nanoparticles in the form of nearly para/le/ fines, what differs from the usual major distribution on the membrane surface. To evaluate the potential application of this new material in electrochemical applications, we proceeded to their characterization by different techniques: microscopic, surface chemical analysis, mechanical and electrical/electrochemical. These results show that the presence of nanoparticles does not seem to significantly affect the transport of protons in the membrane bulk, but it modifies its surface. Furthermore, the mechanical strength of the new material is lower than the unmodified Nafion due to the high interaction between nanoparticles and polymer chains. Moreover, it was a/so observed that some of the mentioned properties significantly varied depending on the degree of hydration of the samplePostprint (published version

Caracterización electroquímica fisicoquímica de un nanomaterial híbrido Nafion/Ag-NPs

La particular estructura química de la matriz perfluorosulfónica del Nafion, con dominios hidrofílicos e hidrofóbicos segregados formando canales nanoscópicos, ha dado pie a su uso como modelo de estructura para la fabricación de nanocompuestos polímero-metal mediante el crecimiento de nanopartículas metálicas en su interior. En particular, mediante la técnica de síntesis intermatrical se ha conseguido el crecimiento de nanopartículas de plata (de un tamaño medio próximo a los 10 nm), las cuales presentan una distribución particular en forma de líneas casi paralelas, que difiere de la distribución más habitual de mayor concentración en la superficie. Para evaluar posibles aplicaciones de este nuevo material se ha realizado su caracterización mediante diferentes técnicas: microscop1ca, análisis químico superficial, mecánica, eléctrica/electroquímica. Los resultados obtenidos muestran que la presencia de nanopartículas no parece afectar significativamente al transporte de protones en la membrana, pero sí modifican la superficie de la misma. Además, la resistencia mecánica del nuevo material es inferior a la del Nafion no modificado debido a la interacción de las partículas con las cadenas de polímero. También se ha observado que algunas de estas propiedades varían de forma importante en/unción del grado de hidratación de la muestra. The particular chemical structure of Nafion, a perfluorosulfonic matrix with segregated hydrophilic and hydrophobic domains forming nanoscale channels, has led to its use as a model structure for the manufacture of polymer-metal nanocomposites by growing in it metal nanoparticles. in particular, using the technique of intermatrix synthesis, the growth of silver nanoparticles (with an average diameter close to 10 nm) has been achieved Moreover, samples exhibit a particular distribution of such nanoparticles in the form of nearly para/le/ fines, what differs from the usual major distribution on the membrane surface. To evaluate the potential application of this new material in electrochemical applications, we proceeded to their characterization by different techniques: microscopic, surface chemical analysis, mechanical and electrical/electrochemical. These results show that the presence of nanoparticles does not seem to significantly affect the transport of protons in the membrane bulk, but it modifies its surface. Furthermore, the mechanical strength of the new material is lower than the unmodified Nafion due to the high interaction between nanoparticles and polymer chains. Moreover, it was a/so observed that some of the mentioned properties significantly varied depending on the degree of hydration of the sampl

Caracterización electroquímica fisicoquímica de un nanomaterial híbrido Nafion/Ag-NPs

La particular estructura química de la matriz perfluorosulfónica del Nafion, con dominios hidrofílicos e hidrofóbicos segregados formando canales nanoscópicos, ha dado pie a su uso como modelo de estructura para la fabricación de nanocompuestos polímero-metal mediante el crecimiento de nanopartículas metálicas en su interior. En particular, mediante la técnica de síntesis intermatrical se ha conseguido el crecimiento de nanopartículas de plata (de un tamaño medio próximo a los 10 nm), las cuales presentan una distribución particular en forma de líneas casi paralelas, que difiere de la distribución más habitual de mayor concentración en la superficie. Para evaluar posibles aplicaciones de este nuevo material se ha realizado su caracterización mediante diferentes técnicas: microscop1ca, análisis químico superficial, mecánica, eléctrica/electroquímica. Los resultados obtenidos muestran que la presencia de nanopartículas no parece afectar significativamente al transporte de protones en la membrana, pero sí modifican la superficie de la misma. Además, la resistencia mecánica del nuevo material es inferior a la del Nafion no modificado debido a la interacción de las partículas con las cadenas de polímero. También se ha observado que algunas de estas propiedades varían de forma importante en/unción del grado de hidratación de la muestra. The particular chemical structure of Nafion, a perfluorosulfonic matrix with segregated hydrophilic and hydrophobic domains forming nanoscale channels, has led to its use as a model structure for the manufacture of polymer-metal nanocomposites by growing in it metal nanoparticles. in particular, using the technique of intermatrix synthesis, the growth of silver nanoparticles (with an average diameter close to 10 nm) has been achieved Moreover, samples exhibit a particular distribution of such nanoparticles in the form of nearly para/le/ fines, what differs from the usual major distribution on the membrane surface. To evaluate the potential application of this new material in electrochemical applications, we proceeded to their characterization by different techniques: microscopic, surface chemical analysis, mechanical and electrical/electrochemical. These results show that the presence of nanoparticles does not seem to significantly affect the transport of protons in the membrane bulk, but it modifies its surface. Furthermore, the mechanical strength of the new material is lower than the unmodified Nafion due to the high interaction between nanoparticles and polymer chains. Moreover, it was a/so observed that some of the mentioned properties significantly varied depending on the degree of hydration of the sampl

Chemical and electrochemical characterization of Nafion containing silver nanoparticles in stripe-like distribution

The particular chemical structure of Nafion with nanostructured and segregated hydrophilic and hydrophobic domains enables its use as a model structure for the manufacture of polymer–Metal nanocomposites. Among such nanocomposites, samples of Nafion-117 containing Ag-NPs of ca.10 nm prepared by Intermatrix Synthesis exhibited a particular distribution in the form of stripes, a regularpattern that could reveal the real morphology of the polymer. To evaluate the potential application of this engineered material (e.g.in electrochemical devices), these new nanocomposite membranes were characterized by different techniques: microscopic, surface chemical analysis, mechanical and electrical/electrochemical. X-ray (XRD and XPS) analyses combined with synchrotron experiments (XANES) were used to determine the chemical speciation of Ag in the membrane. Membrane potential and impedance spectroscopy measurements showed that such Ag-NPs did not hinder the diffusive transport of protons in the membrane bulk, moreover, they slightly reduced the electrical resistance in fully hydrated state samples. The mechanical evaluation of the nanocomposite evidenced a reduction of the elastic character when compared with the unmodified Nafion-117 sampl