Search

The combination of different nanomaterials to achieve particular applications is a topic with an increasing impact on diverse areas of nanotechnology. In particular, the material of La2Zr2O7 (LZO) and NiO could be employed as a source of catalyst for carbon nanotube fabrication. In this work, the Ni/LZO material was utilized to fabricate nitrogen-doped multiwalled carbon nanotube (N-MWCNTs). The N-MWCNTs were produced at 850 °C by the aerosol assisted catalytic chemical vapor deposition method using benzylamine as the sole carbon and nitrogen precursor. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry. Before the synthesis of N-MWCNTs, NiO was reduced to Ni to act as a catalyst and LZO as support. N-MWCNTs exhibited the typical feature bamboo shape morphology with small nanoparticles anchored inside and on its surface. The electrochemical studies show interesting results about charge capacity and a hydroquinone/quinone redox process of oxygen functionalities. The magnetic properties of N-MWCNTs showed a ferromagnetic behavior with a saturated magnetization of 43 emu/g at 0.2 T.

The creation of films formed by the incorporation of ZnO or TiO2 in poly(methylmethacrylate) PMMA matrices was proposed in order to improve their properties as resistance to high temperatures. ZnO and TiO2 nanoparticles were synthesized by the sol-gel method, which does not require the use of surfactants and is easily scalable. In the present work, zinc oxide (ZnO) or titanium oxide (TiO2) incorporations were carried out in a polymeric matrix of Poly(methylmethacrylate) PMMA. Both oxides were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and diffuse reflectance UV-Vis spectroscopy. PMMA was obtained by the suspension free radical polymerization method and PMMA composites containing ZnO or TiO2 were obtained. Polymer characterization was performed using Fourier transform infrared spectroscopy (FTIR). The composites were analyzed by thermogravimetric analysis (TGA) and its thermal resistance was found to be the best incorporation of TiO2 in 1%.

Due to continuous use and environmental factors (humidity and continuous exposure to the sun), the leather upholstery experiences cracking, discoloration and possible yellowing. The above factors significantly decrease the life of leather upholstery in cars. The objective of this work is to synthesize zinc oxide nanoparticles, which have optical properties that allow it to absorb UV radiation and then incorporate them into a polymeric matrix to develop a coating with UV protection for leather finishing in the automobile industry. The particles of zinc oxide were synthesized by the sol-gel method to obtain a nanometric particle size, the method represent a low-cost synthesis method, without the use of surfactants and easily scalable. With monoethylene glycol was formed a stable colloid with the zinc oxide nanoparticles and the polymer matrix. Finally, the final leather finishing obtained for the automotive industry has greater resistance to bending, also thermal stability was improved. In consequence, the lifetime of the leather finishing has improved.

In this work, electrochemical sensors were developed for the detection of artificial sweeteners such as D-sorbitol and Maltitol in aqueous solutions. These compounds are classified as polyalcohols and are widely used in the food and beverage industry to replace common sugar. However, their consumption is not currently regulated, and excessive use leads to consequences in the body such as increased blood glucose levels. Graphene oxide (OG) inks were prepared, which were deposited on vitreous carbon (CV) electrodes, followed by enzymatic immobilization. The detection capacity of the biosensors was evaluated applying electrochemical techniques. The biosensor with the best levels of detection, reproducibility and durability for the analytes under study for the detection of D-Sorbitol turned out to be that measured at a working voltage of 0.86 V vs Ag / AgCl / KCl (3 M), depositing 20 μL of OG ink and using a dilution of 0.5 μL / 100 μL of (alcohol oxidase / PBS). In the case of Maltitol the best designed biosensor was worked at 1.06 V vs Ag / AgCl / KCl (3 M), depositing 20 μL of OG ink and using a dilution of 2.0 μL / 100 μL of (alcohol oxidase / phosphate buffer).

The research aims were to construct an air-breathing paper-based microfluidic fuel cell (paper-based μ FC) and to evaluated it with different soft drinks to provide energy for their prospective use in portable devices as an emergency power source. First, in a half-cell configuration, cyclic voltammetry showed that glucose, maltose, and fructose had specific oxidation zones in the presence of platinum-ruthenium on carbon (PtRu/C) when they were individual. Still, when they were mixed, glucose was observed to be oxidized to a greater extent than fructose and maltose. After, when a paper-based μ FC was constructed, PtRu/C and platinum on carbon (Pt/C) were used as anode and cathode, the performance of this μ FC was mostly influenced by the concentration of glucose present in each soft drink, obtaining maximum power densities at room temperature of 0.061, 0.063, 0.060, and 0.073 mW cm − 2 for Coca Cola ® , Pepsi ® , Dr. Pepper ® , and 7up ® , respectively. Interestingly, when the soft drinks were cooled, the performance was increased up to 85%. Furthermore, a four-cell stack μ FC was constructed to demonstrate its usefulness as a possible power supply, obtaining a power density of 0.4 mW cm − 2 , using Coca Cola ® as fuel and air as oxidant. Together, the results of the present study indicate an alternative application of an μ FC using soft drinks as a backup source of energy in emergencies.

Polyfluorene materials have demonstrated to be important components in the fabrication of organic solar cell devices, in both: the active and electron transport layers. The oxidative synthesis as well as optical and electrical properties of new polyfluorene copolymers containing 2,2′-(9,9-dioctyl-9H-fluorene-2,7-diyl) bistiophene and 3-alkylthiophene, alkyl = hexyl (PA1) and octyl (PA2) or 3,4-ethylenedioxythiophene (EDOT) (PM) were investigated. Changes in the HOMO–LUMO energy gap promoted for the insertion of EDOT ring were studied in thick film by using cyclic-voltammetry measurements and compared with the optical properties analyzed by UV–Visible spectroscopy. DFT calculations were used to investigate the possible electronic density distribution and conformational parameter for repetition units into the polymeric structure. Finally, these polymer were preliminary evaluated as donor materials into organic solar cells with architecture ITO/PEDOT:PSS/co-polymer:PC71BM/Field’s metal. Photovoltaic devices showed a very acceptable open circuit voltage (Voc) value, up to 0.92 V.

We investigated the effects of long-time thermal oxidation (LTO) of nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) at 330 °C in air. By scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, Raman spectroscopy and cyclic voltammetry we characterize the oxidized N-MWCNTs (Ox-NMWCNTs). SEM and TEM characterizations revealed that LTO promoted structural damages driven by Fe-based nanoparticles, producing holey N-MWCNTs. The XRD patterns showed that short times of oxidation process, encapsulated Fe3C, and α-Fe nanoparticles in N-MWCNTs cut or perforate their graphite layers. For LTO (>300 h), Fe3C and α-Fe nanoparticles are transformed into Fe3O2 (hematite structure). Deconvolution analysis of the (0 0 2) crystallographic planes allows us to monitor the graphitization evolution of the Ox-NMWCNTs. XPS characterization demonstrated that the surface composition of Ox-N-MWCNTs is influenced by the LTO, while carbon and nitrogen decrease in percentage, the oxygen increases. We have found that LTO favored the formation of pyrrolic nitrogen doping. The holey N-MWCNTs are a porous material with a moderate surface area. According to the voltammetry studies, when the Ox-N-MWCNTs are acid-treated, the surface area is doubled and presents a double layer capacitance that could be advantageous for energy applications.

Natural catalysts are important for the low-cost and large-scale production of carbon nanostructures. In this study, we used a natural material obtained from thin bands of sedimentary rocks known as Banded Iron Formation (BIF). BIF powders (pristine and ball-milled) were used as catalysts for the large-scale production of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) via an aerosol-assisted catalytic chemical vapor deposition (AACCVD) experiment. The morphology and composition profiles of the BIF powders and N-MWCNT samples were analyzed by scanning and transmission electron microscopies, X-ray diffraction, X-ray photoelectron (XPS) and Raman spectroscopies, and thermogravimetric analysis. XRD characterizations revealed that the BIF powders were mainly composed of quartz and hematite. This result was also confirmed by Raman spectroscopy. The production efficiency of 340% wt./wt. of the N-MWCNTs was obtained by 1 h ball-milled BIF powders. The specific surface area of the N-MWCNTs reached 37.87 m2/g. The type of nitrogen doping, oxygen functional groups, silicon, and carbon species (sp2 and sp3) hosted at the surface of the N-MWCNTs were quantified by XPS. The electrochemical response of electrodes composed of the N-MWCNTs were studied via cyclic voltammetry, electrochemical impedance, and coulombic efficiency determination to assess the possible applications of our synthesized materials as energy storage or sensor systems. The magnetic properties and effects of acid and thermal treatments on the morphology of the N-MWCNTs are also presented.