Electrospun Nanofibers of Acrylonitrile and Itaconic Acid Copolymers and their Stabilization

(APS) as an oxidant in the aqueous medium,and nanofibers produced by electrospinning . Electrospun nanofiber mats were by treated heat under air atmosphere to be stabilized. Nanofiber production from AN-IA copolymers and suitability of the nanofiber as carbon nanofiber precursor is discussed. Copolymer are characterized using Fourier Transform Infrared - Attenuated Total Reflectance spectrometer (FTIR-ATR), Nuclear Magnetic Resonance Spectroscopy (1H-NMR), differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The effect of IA content on the spectroscopic and thermal properties of AN-IA copolymers was investigated. Increasing IA content confirmed by spectroscopic methods seriously affects thermal properties which is important for carbon nanofiber production. IA provides a catalytic effect on stabilization process by decreasing initiation cyclization reaction temperature from 202 to 195 oC. Elecrospinning from the AN-IA copolymer solutions in dimethyl foramide (DMF) was performed, morphology of nanofibers was monitored using Scanning Electron Microscopy (SEM). Bead free nanofibers were produced from AN-IA copolymer solutions under same conditions. Average nanofiber diameter decreases from 878±18 to 376±7 nm according to increasing IA content in copolymers. The nanofiber mats produced were treated at high temperature under air atmosphere for oxidative stabilization. Stabilized nanofibers were characterized using FTIR-ATR spectrometer and a new structure was monitored as a result of cyclization reactions. The stabilized nanofibers were also characterized mophologically using SEM. Volume loss occurring after heat treatment calculated based on the nanofiber diameter changes. Consequently, electrospun nanofibers can be suggested as a carbon nanofiber precursor due to suitability for electrospinning and stabilization process

In vivo biosensing via tissue-localizable near-infrared-fluorescent single-walled carbon nanotubes

Single-walled carbon nanotubes are particularly attractive for biomedical applications, because they exhibit a fluorescent signal in a spectral region where there is minimal interference from biological media. Although single-walled carbon nanotubes have been used as highly sensitive detectors for various compounds, their use as in vivo biomarkers requires the simultaneous optimization of various parameters, including biocompatibility, molecular recognition, high fluorescence quantum efficiency and signal transduction. Here we show that a polyethylene glycol ligated copolymer stabilizes near-infrared-fluorescent single-walled carbon nanotubes sensors in solution, enabling intravenous injection into mice and the selective detection of local nitric oxide concentration with a detection limit of 1 µM. The half-life for liver retention is 4 h, with sensors clearing the lungs within 2 h after injection, thus avoiding a dominant route of in vivo nanotoxicology. After localization within the liver, it is possible to follow the transient inflammation using nitric oxide as a marker and signalling molecule. To this end, we also report a spatial-spectral imaging algorithm to deconvolute fluorescence intensity and spatial information from measurements. Finally, we demonstrate that alginate-encapsulated single-walled carbon nanotubes can function as implantable inflammation sensors for nitric oxide detection, with no intrinsic immune reactivity or other adverse response for more than 400 days.National Institutes of Health (U.S.) (T32 Training Grant in Environmental Toxicology ES007020)National Cancer Institute (U.S.) (Grant P01 CA26731)National Institute of Environmental Health Sciences (Grant P30 ES002109)Arnold and Mabel Beckman Foundation (Young Investigator Award)National Science Foundation (U.S.). Presidential Early Career Award for Scientists and EngineersScientific and Technological Research Council of Turkey (TUBITAK 2211 Research Fellowship Programme)Scientific and Technological Research Council of Turkey (TUBITAK 2214 Research Fellowship Programme)Middle East Technical University. Faculty Development ProgrammeSanofi Aventis (Firm) (Biomedical Innovation Grant

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Preparation and characterization of nano-sized Pt-Ru/C catalysts and their superior catalytic activities for methanol and ethanol oxidation

Carbon-supported PtRu nanoparticles (Ru/Pt: 0.25) were prepared by three different methods; simultaneous reduction of PtCl(4) and RuCl(3) (catalyst I) and changing the reduction order of PtCl4 and RuCl3 (catalysts II and III) to enhance the performance of the anodic catalysts for methanol and ethanol oxidation. Structure, microstructure and surface characterizations of all the catalysts were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results of the XRD analysis showed that all catalysts had a face-centered cubic (fcc) structure with different and smaller lattice parameters than that of pure platinum, showing that the Ru incorporates into the Pt fcc structure by different ratios in all the catalysts. The typical particle sizes of all catalysts were in the range of 2-3 nm. The most active and stable catalyst for methanol and ethanol oxidation is catalyst III, in which a large amount (more than 90%) of PtRu alloy formation was observed. It has been found that this catalyst is about 8.0 and 33.4 times more active at similar to 0.60 V towards the methanol and ethanol oxidation reactions, respectively, compared to the commercial Pt catalyst

Efficiency enhancement of methanol/ethanol oxidation reactions on Pt nanoparticles prepared using a new surfactant, 1,1-dimethyl heptanethiol

In this study, carbon-supported platinum nanoparticle catalysts were prepared using PtCl(4) and H(2)PtCl(6) as starting materials and 1-heptanethiol, 1,1-dimethyl heptanethiol, 1-hexadecanethiol and 1-octadecanethiol as surfactants. These nanoparticles can be used as catalysts for methanol and ethanol oxidation reactions in methanol and ethanol fuel cells. 1,1-Dimethyl heptanethiol was used for the first time in this type of synthesis; other surfactants were used to synthesize nanoparticles for comparison of the catalyst's performance. Cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to characterize the catalysts. It should also be stressed that AFM was employed for the first time in determining the surface topography of these catalysts. XRD, TEM and AFM height results indicate that the platinum crystallizes into a face-centered cubic structure and the surfactant plays an important role in determining the size of the platinum nanoparticles. XPS data revealed that the platinum was found in two different oxidation states, Pt(0) and Pt(IV) with a ratio of about 7.5 : 2.5, respectively. Electrochemical studies showed catalyst IIa to be the most active sample towards methanol/ethanol oxidation reactions (similar to 342 A g(-1) Pt at 0.612 V for methanol (4.6 times more active than the commercial catalyst), similar to 309 A g(-1) Pt at 0.66 V for ethanol, (15.4 times more active than the commercial catalyst))

The preparation and characterization of nano-sized Pt-Pd/C catalysts and comparison of their superior catalytic activities for methanol and ethanol oxidation

In this study, two groups of carbon supported PtPd samples with different percentages of metals were prepared to examine the effects of Pd and stabilizing agents on the catalytic activity towards methanol and ethanol oxidation reactions. As a stabilizing agent, 1-hexanethiol and 1,1-dimethyl hexanethiol were used for group "a" and "b" catalysts, respectively. Cyclic voltammetry, chronoamperometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to understand the nature of the prepared catalysts. TEM and XRD results indicated a similar size distribution of the metal nanoparticles with a narrow average crystallite size of 3.0-3.7 nm. XPS data revealed the presence of two different oxidation states for both platinum and palladium, being Pt(0), Pt(IV), Pd(0), and Pd(II). Electrochemical studies indicated that the group "b" type catalysts have a higher catalytic activity than group "a". The most active catalyst was found to be a carbon supported 88 %Pt/12 %Pd prepared with 1,1-dimethyl hexanethiol, which has an activity of similar to 5 times (similar to 0.450 A/mg Pt at 0.57 V for methanol) and similar to 14 times (similar to 0.350 A/g Pt at 0.56 V for ethanol) greater than the commercial E-TEK catalyst

High performance Pt nanoparticles prepared by new surfactants for C-1 to C-3 alcohol oxidation reactions

In this study, platinum nanoparticles have been prepared using PtCl4 as a starting material and 1-hexylamine, N-methylhexylamine, N,N-dimethylhexylamine, 1-heptylamine, N-methylheptylamine, and N, N-dimethylheptylamine as surfactants. All these surfactants were used in this synthesis, for the first time, to explore the effect of primary, secondary, and tertiary amine and chain length on the size and catalytic activity toward C1-C3 alcohol electro-oxidation. The electrochemical performance of all catalysts was determined using cyclic voltammetry and chronoamperometry. These techniques indicate that the highest electrocatalytic performance was generally observed when electrochemical surface area (ECSA), percent platinum utility, roughness factor, and the number of CH3 groups attached to the nitrogen atom is higher and the chain length shorter (C6H13). In addition, other important properties such as the crystal structure of platinum, size, and distribution of the platinum nanoparticles on the carbon support, and Pt(0) to Pt(IV) ratio, were determined using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. It was found that increasing ECSA, Pt(0)/Pt(IV) ratio, % Pt utility, and roughness factor improves the C1-C3 alcohol oxidation catalytic performance

Effect of Reductive Dithiothreitol and Trolox on Nitric Oxide Quenching of Single-Walled Carbon Nanotubes

Semiconducting single-walled carbon nanotubes (SWCNTs) fluoresce in the near-IR and are promising as optical sensors when functionalized to enable analyte recognition. SWCNT sensors with enhanced fluorescence emission have been hypothesized to have greater sensitivities, and reductive brightening reagents, such as dithiothreitol (DTT) and Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), enhance SWCNT brightness. The authors examine the effect of Trolox and DTT on the sensitivity of a nitric oxide (NO) sensor and report that the NO sensitivity is reduced. The NO adsorption rate decreases from 0.0007 ± 0.00003 to 0.000 3± 0.00003 and 0.0004 ± 0.0001 s-1 μM-1 upon pretreatment of 1 mM Trolox and 1 mM DTT, resp. These results are consistent with a model where Trolox and DTT are competitive binding agents with NO, occupying one of a finite no. of available SWCNT binding sites and altering the NO binding strength. In the use of brightening agents, a trade-off is predicted between signal intensity and analyte sensitivity. [on SciFinder(R)