Enric Bertran

Bio: Enric Bertran is an academic researcher from University of Barcelona. The author has contributed to research in topics: Thin film & Plasma-enhanced chemical vapor deposition. The author has an hindex of 34, co-authored 234 publications receiving 4133 citations. Previous affiliations of Enric Bertran include Pennsylvania State University.

Wettability, ageing and recovery process of plasma-treated polyamide 6

Abstract: The wetting properties of polyamide 6 rods treated with radiofrequency (RF) low-temperature plasma (LTP) using three different non-polymerizing gases (air, nitrogen and water vapour) were determined using the Wilhelmy contact-angle technique. Information on the acidic or basic nature of the ionizable groups generated on the rod surface was obtained using contact-angle titration. The wettability obtained depends on the plasma gas used, and it tends to decrease with time elapsed after the treatment when the samples are kept in an air environment. However, the wettability can be recovered by immersion of the aged samples in water. The degree of recovery depends on the plasma gas used and the highest recovery was obtained with water vapour plasma treated samples. Both ageing and recovery behaviour can be attributed to the reorganisation of hydrophilic groups which tend to reversibly migrate or orient towards the bulk phase depending on the storage conditions, although other factors can also have influence.

Mueller matrix microscope with a dual continuous rotating compensator setup and digital demodulation

Abstract: In this paper we describe a new Mueller matrix (MM) microscope that generalizes and makes quantitative the polarized light microscopy technique. In this instrument all the elements of the MU are simultaneously determined from the analysis in the frequency domain of the time-dependent intensity of the light beam at every pixel of the camera. The variations in intensity are created by the two compensators continuously rotating at different angular frequencies. A typical measurement is completed in a little over one minute and it can be applied to any visible wavelength. Some examples are presented to demonstrate the capabilities of the instrument.

Particle agglomeration study in rf silane plasmas: In situ study by polarization-sensitive laser light scattering

Abstract: To determine self-consistently the time evolution of particle size and their number density in situ multi-angle polarization-sensitive laser light scattering was used. Cross-polarization intensities (incident and scattered light intensities with opposite polarization) measured at 135 degrees and ex situ transmission electronic microscopy analysis demonstrate the existence of nonspherical agglomerates during the early phase of agglomeration. Later in the particle time development both techniques reveal spherical particles again. The presence of strong cross-polarization intensities is accompanied by low-frequency instabilities detected on the scattered light intensities and plasma emission. It is found that the particle radius and particle number density during the agglomeration phase can be well described by the Brownian free molecule coagulation model. Application of this neutral particle coagulation model is justified by calculation of the particle charge whereby it is shown that particles of a few tens of nanometer can be considered as neutral under our experimental conditions. The measured particle dispersion can be well described by a Brownian free molecule coagulation model including a log-normal particle size distribution. (C) 1996 American Institute of Physics.

A review of electrode materials for electrochemical supercapacitors

Abstract: In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

Water‐Soluble Fluorescent Carbon Quantum Dots and Photocatalyst Design

Abstract: Carbon nanostructures are attracting intense interest because of their many unique and novel properties. The strong and tunable luminescence of carbon materials further enhances their versatile properties; in particular, the quantum effect in carbon is extremely important both fundamentally and technologically. Recently, photoluminescent carbonbased nanoparticles have received much attention. They are usually prepared by laser ablation of graphite, electrochemical oxidation of graphite, electrochemical soaking of carbon nanotubes, thermal oxidation of suitable molecular precursors, vapor deposition of soot, proton-beam irradiation of nanodiamonds, microwave synthesis, and bottom-up methods. Although small (ca. 2 nm) graphite nanoparticles show strong blue photoluminescence (PL), definitive experimental evidence for luminescence of carbon structure arising from quantum-confinement effects and size-dependent optical properties of carbon quantum dots (CQDs) remains scarce. Herein, we report the facile one-step alkali-assisted electrochemical fabrication of CQDs with sizes of 1.2– 3.8 nm which possess size-dependent photoluminescence (PL) and excellent upconversion luminescence properties. Significantly, we demonstrate the design of photocatalysts (TiO2/CQDs and SiO2/CQDs complex system) to harness the use of the full spectrum of sunlight (based on the upconversion luminescence properties of CQDs). It can be imagined that judicious cutting of a graphite honeycomb layer into ultrasmall particles can lead to tiny fragments of graphite, yielding CQDs, which may offer a straightforward and facile strategy to prepare high-quality CQDs. Using graphite rods as both anode and cathode, and NaOH/EtOH as electrolyte, we synthesized CQDs with a current intensity of 10–200 mAcm . As a reference, a series of control experiments using acids (e.g. H2SO4/EtOH) as electrolyte yielded no formation of CQDs. This result indicates that alkaline environment is the key factor, and OH group is essential for the formation of CQDs by the electrochemical oxidation process. Figure 1a shows a trans-

Boron Nitride Nanotubes and Nanosheets

Abstract: Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments.

Nanostructured carbon–metal oxide composite electrodes for supercapacitors: a review

Abstract: This paper presents a review of the research progress in the carbon–metal oxide composites for supercapacitor electrodes. In the past decade, various carbon–metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon–metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.