A hydrogen peroxide (H2O2) sensor and biosensor based on modified multi-walled carbon nanotubes (CNTs) with titanium dioxide (TiO2) nanostructures was designed and evaluated. The construction of the sensor was performed using a glassy carbon (GC) modified electrode with a TiO2–CNT film and Prussian blue (PB) as an electrocalatyzer. The same sensor was also employed as the basis for H2O2 biosensor construction through further modification with horseradish peroxidase (HRP) immobilized at the TiO2–fCNT film. Functionalized CNTs (fCNTs) and modified TiO2–fCNTs were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray DifFraction (XRD), confirming the presence of anatase over the fCNTs. Depending on the surface charge, a solvent which optimizes the CNT dispersion was selected: dimethyl formamide (DMF) for fCNTs and sodium dodecylsulfate (SDS) for TiO2–fCNTs. Calculated values for the electron transfer rate constant (ks) were 0.027 s−1 at the PB–fCNT/GC modified electrode and 4.7 × 10−4 s−1 at the PB–TiO2/fCNT/GC electrode, suggesting that, at the PB–TiO2/fCNT/GC modified electrode, the electronic transfer was improved. According to these results, the PB–fCNT/GC electrode exhibited better Detection Limit (LD) and Quantification Limit (LQ) than the PB–TiO2/fCNT/GC electrode for H2O2. However, the PB film was very unstable at the potentials used. Therefore, the PB–TiO2/fCNT/GC modified electrode was considered the best for H2O2 detection in terms of operability. Cyclic Voltammetry (CV) behaviors of the HRP–TiO2/fCNT/GC modified electrodes before and after the chronoamperometric test for H2O2, suggest the high stability of the enzymatic electrode. In comparison with other HRP/fCNT-based electrochemical biosensors previously described in the literature, the HRP–fCNTs/GC modified electrode did not show an electroanalytical response toward H2O2.
In this investigation, a hydrogen peroxide (H2O2) electrochemical sensor was evaluated. Prussian blue (PB) was electrodeposited at a glassy carbon (GC) electrode modified with titanium dioxide– and zirconia-doped functionalized carbon nanotubes (TiO2.ZrO2-fCNTs), obtaining the PB/TiO2.ZrO2-fCNTs/GC-modified electrode. The morphology and structure of the nanostructured material TiO2.ZrO2-fCNTs was characterized by transmission electron microscopy, the specific surface area was determined via Brunauer–Emmett–Teller, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The electrochemical properties were studied by cyclic voltammetry and chronoamperometry. Titania-zirconia nanoparticles (5.0 ± 2.0 nm) with an amorphous structure were directly synthesized on the fCNT walls, aged during periods of 20 days, obtaining a well-dispersed distribution with a high surface area. The results indicated that the TiO2.ZrO2-fCNT–nanostructured material exhibits good electrochemical properties and could be tunable by enhancing the modification conditions and method of synthesis. Covering of the nanotubes with TiO2-ZrO2 nanoparticles is one of the main factors that affected immobilization and sensitivity of the electrochemical biosensor. The electrode modified with TiO2-ZrO2 nanoparticles with the 20-day aging time was superior regarding its reversibility, electric communication, and high sensitivity and improves the immobilization of the PB at the electrode. The fabricated sensor was used in the detection of H2O2 in whey milk samples, presenting a linear relationship from 100 to 1,000 μmol L−1 between H2O2 concentration and the peak current, with a quantification limit (LQ) of 59.78 μmol L−1 and a detection limit (LD) of 17.93 μmol L−1.
Esta publicación presenta tres grandes resultados de la aplicación del Modelo de Modernización para la Gestión de Organizaciones – MMGO- en 127 PyMEs colombianas: el análisis estadístico y psicométrico de los instrumentos utilizados en el MMGO, la evidencia empírica de la aplicación del Modelo en las 127 empresas y las recomendaciones para desarrollar una gestión empresarial de excelencia para la PyME colombiana.
In the search of new materials for bone regeneration, the materials with piezoelectric properties look very promising. It has been reported that piezoelectric materials induce bone growth and enhance implant integration. Additionally, it has been found that bioactivity increases in negatively charge surfaces such as polarized BaTiO3 (BT) and polarized hydroxyapatite (HAp). Additionally, it is known that BaSO4 (BS) increases biocompatibility. Therefore, in this work, composites materials of 80BT/20BS (BTS) in different proportions with HAp (HAp/BTS: 10/90, 30/70, 50/50, 70/30 y 90/10) were prepared by a mixture of nanometric powders and then they were sintered at 1000 °C for a period of 5 h. The materials were polarized at 130, 300 and 400 °C applying a DC electric field of 1 kV/mm, during 1 h. The electric field was maintained until the material was cooled down to room temperature. The electric and piezoelectric response were measured immediately after cooling, after 1 h and after 24 h. The dielectric measurements of materials were performed at different frequencies (0.1 to 100 kHz). The polarized and unpolarized materials were immersed in simulated body fluid (1.5 SBF) for 7 and 19 days. The deposition and growth of hydroxyapatite using the biomimetic method was followed by FTIR and SEM. The polarization effect on the crystalline growth of hydroxyapatite formed from the SBF solution has been demonstrated. The process of biomineralization of HAp on HAp/BTS composites increased considerably with the addition of barium titanate, this effect greatly improved in polarized materials. The typical coral-like morphology characteristic of HAp formation from SBF deposition was observed after 7 days of SBF immersion for polarized composites. Excellent dielectric properties were determined by adding 30% Of BaTiO3, obtaining for these composites dielectric constant values of the order of 20 to 10 kHz, values similar to that of human bones. Therefore, these materials look very promising for bone regeneration.
Para el sector cerámico europeo resulta natural reconocer y distinguir dentro de una mina o afloramiento de mineral arcilloso, propiedades similares y determinar correspondencias beneficiosas entre la naturaleza mineral y las propiedades. Así, es posible prever el potencial de uso de un lote, concertar su influencia en producción y prevenir las variaciones que generan pérdidas, minimizan la productividad y la calidad en los productos. En Latinoamérica y en especial en el Ecuador es escasa la información que se tiene sobre las propiedades tecnológicas de las materias primas utilizadas en el sector cerámico, pocos industriales, artesanos y centros de investigación realizan estudios formales para minimizar y controlar el efecto de las materias primas en la productividad. Dada la falta de conocimiento que se tiene para abordar esta problemática, en este trabajo se sugiere el uso de un protocolo de caracterización y valoración de minerales arcillosos, a fin de que sea útil tanto para el sector cerámico artesanal, como el industrial. De esta forma, este trabajo se ha centrado en exponer las características tecnológicas y cerámicas de minerales arcillosos pertenecientes a la Sierra del Ecuador, establecer su clasificación y presentar su potencial de aplicación dentro del sector cerámico, a partir del protocolo de categorización propuesto.
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