Fotoánodos modificados con óxido de grafeno reducido para mejorar el rendimiento fotoelectrocatalítico de B-TiO2 bajo luz visible

"The effect of reduced graphene oxide (rGO) content in boron-modified TiO2 nanocrystalline films on their photocatalytic activity in phenol oxidation is investigated. Visible-light-active TiO2 modified photoanodes were prepared by incorporating graphene sheets into the sol-gel reaction of B-TiO2, followed by depositing the reaction products on 304 stainless steel plates by dip-coating technique. Thin films obtained by in situ sol-gel synthesis were characterized by FESEM, GIXRD and UV–vis diffuse reflectance spectroscopy. FESEM examination showed cracked films due to the tensile stress generated by solvent evaporation. GIXRD results showed that boron in the films inhibits the growth of crystallites. Comparing to unmodified TiO2, B-TiO2/rGO showed a red shift in the band gap. The potentiodynamic anodic polarization measurements showed that graphene incorporation improved the photogenerated electron transport within the film, hence increasing the photocurrent. These enhancements are explained on the basis of the ability of graphene in promoting the charge carrier separation by transferring the photogenerated electrons from the illuminated photoanode to the substrate. The film B-TiO2/rGO obtained from the sol solution containing 0.03 wt/v% boron and 3 wt/v% graphene exhibited the highest photocurrent, which was 30 times larger compared with the photocurrent of TiO2 film.""Se investiga el efecto del contenido de óxido de grafeno reducido (rGO) en películas de TiO2 modificadas con boro sobre su actividad fotocatalítica en la oxidación de fenol. Fotoánodos modificados de TiO2 activos a la luz visible fueron preparados incorporando hojas de grafeno en la reacción sol-gel de B-TiO2, seguido por el depósito de los productos de la reacción sobre láminas de acero inoxidable 304 por la técnica dip-coating. Las películas delgadas obtenidas por síntesis sol-gel in-situ fueron caracterizadas por FESEM, GIXRD y espectroscopia de reflectancia difusa UV-vis. La observación por FESEM mostró películas agrietadas debido al estrés mecánico generado por la evaporación del solvente. Los resultados de GIXRD mostraron que el boro en las películas inhibe el tamaño de los cristalitos. Comparando con el TiO2, el dióxido de titanio modificado presentó un desplazamiento de la banda de energía prohibida hacia el rojo. Las mediciones de polarización anódica potenciodinámica mostraron que la incorporación de grafeno mejora el transporte de electrones fotogenerados dentro de las películas compuestas incrementando así la fotocorriente. Estas mejoras se explican en base a la habilidad del grafeno para facilitar la separación de portadores de carga, transfiriendo los electrones fotogenerados desde la película iluminada de B-TiO2 hasta el sustrato. La película compuesta B-TiO2/rGO obtenida a partir de la solución con 0.03 % p/v de boro y 3 % p/v de grafeno presentó la fotocorriente más alta, la cual fue 30 veces mayor comparada con la fotocorriente de la película de TiO2.

Airy pattern on narrow photoluminescence spectrum of band to band recombination in CdTe: Te thin films

Semiconductor CdTe:Te films were deposited by means of rf sputtering on glass substrates. The excess of Te gave place to a high number of Cd-vacancies (VCd) producing p-type CdTe films. The density of carriers produced a high strength surface electric field which allowed obtain the bandgap value employing modulated transmittance spectroscopy. The obtained bandgap value of 1.40 ± 0.01 eV was confirmed by absorption spectroscopy measures. The density of holes is so high that bandgap renormalization is observed. Photoluminescence (PL) measurements were carried out with the down-converted 883.2 nm (1.403 eV) line of the 441.6 nm wavelength of a He-Cd laser. This energy allows to produce a resonant excitation of the CdTe:Te films, in such a way that electrons from the conduction band (CB) can be just excited to the valence band (VB). The resonant excitation produced a PL spectrum of band to band electron-hole recombination showing discrete energy emissions that follow the pattern of oscillations corresponding to the Airy model for a quantum triangular potential well. The average width of signals of the higher energy oscillations is 12 ± 3 μeV and separation between energy levels is of the order of 12 ± 3 μeV

Community-based (rooted) research for regeneration: understanding benefits, barriers, and resources for Indigenous education and research

For researchers and educators working to engage Indigenous knowledges, colonial legacies, including assimilation-driven education curriculum, form challenging and complex pathways to navigate. To address such legacies and support Indigenous education efforts, we developed a participatory research model exploring benefits, barriers, and resources for engaging Indigenous knowledges in science education and research. This article details methods and findings from an inter-island knowledge exchange describing the experiences of seven Indigenous scholars and practitioners working in the Caribbean. We drew from Indigenous research methodologies, participatory action research, and constructivist grounded theory. Our research findings describe how individual experiences weave into a larger collective, intergenerational story of survival, adaptation, resilience, and regeneration. Findings from this study deepen understandings regarding how underlying socio-political challenges manifest at different scales of space and time, from immediate to intergenerational, and practitioner-identified resources to overcome them, such as Indigenous language, community action, and creating support systems.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Changes in phytochemical composition, bioactivity and in vitro digestibility of guayusa leaves (Ilex guayusa Loes.) in different ripening stages

BACKGROUND: Guayusa (Ilex guayusa Loes.) leaves, native of the Ecuadorian Amazon, are popularly used for preparing teas. This study aimed to assess the influence of leaf age on the phenolic compounds and carotenoids and the bioactivity and digestibility (in vitro) of aqueous and hydroalcoholic leaf extracts. RESULTS: In total, 14 phenolic compounds were identified and quantified. Chlorogenic acid and quercetin-3-O-hexose were the main representatives of the hydroxycinnamic acids and flavonols respectively. Seven carotenoids were quantified, lutein being the main compound. Ripening affected phenolic content significantly, but there was no significant difference in carotenoid content. Antioxidant capacity, measured by the DPPH• method, was also significantly affected by leaf age. The measurement of in vitro digestibility showed a decrease in phenolic content (59%) as well as antioxidant capacity, measured by the ABTS•+ method, in comparison with initial conditions of the guayusa infusion. Antibacterial and anti-inflammatory activities were assayed with young leaves owing to their higher phenolic contents. Guayusa did not show any antibacterial activity against Escherichia coli ATCC 25922 or Staphylococcus aureus ATCC 25923. Finally, the hydroalcoholic and aqueous extracts exhibited high in vitro anti-inflammatory activity (>65%). CONCLUSION: Young guayusa leaves have potential applications as a functional ingredient in food and pharmaceutical industries. © 2017 Society of Chemical Industry. © 2017 Society of Chemical IndustryBACKGROUND: Guayusa (Ilex guayusa Loes.) leaves, native of the Ecuadorian Amazon, are popularly used for preparing teas. This study aimed to assess the influence of leaf age on the phenolic compounds and carotenoids and the bioactivity and digestibility (in vitro) of aqueous and hydroalcoholic leaf extracts. RESULTS: In total, 14 phenolic compounds were identified and quantified. Chlorogenic acid and quercetin-3-O-hexose were the main representatives of the hydroxycinnamic acids and flavonols respectively. Seven carotenoids were quantified, lutein being the main compound. Ripening affected phenolic content significantly, but there was no significant difference in carotenoid content. Antioxidant capacity, measured by the DPPH• method, was also significantly affected by leaf age. The measurement of in vitro digestibility showed a decrease in phenolic content (59%) as well as antioxidant capacity, measured by the ABTS•+ method, in comparison with initial conditions of the guayusa infusion. Antibacterial and anti-inflammatory activities were assayed with young leaves owing to their higher phenolic contents. Guayusa did not show any antibacterial activity against Escherichia coli ATCC 25922 or Staphylococcus aureus ATCC 25923. Finally, the hydroalcoholic and aqueous extracts exhibited high in vitro anti-inflammatory activity (>65%). CONCLUSION: Young guayusa leaves have potential applications as a functional ingredient in food and pharmaceutical industries. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industr

Biological underpinnings for lifelong learning machines

Biological organisms learn from interactions with their environment throughout their lifetime. For artificial systems to successfully act and adapt in the real world, it is desirable to similarly be able to learn on a continual basis. This challenge is known as lifelong learning, and remains to a large extent unsolved. In this Perspective article, we identify a set of key capabilities that artificial systems will need to achieve lifelong learning. We describe a number of biological mechanisms, both neuronal and non-neuronal, that help explain how organisms solve these challenges, and present examples of biologically inspired models and biologically plausible mechanisms that have been applied to artificial systems in the quest towards development of lifelong learning machines. We discuss opportunities to further our understanding and advance the state of the art in lifelong learning, aiming to bridge the gap between natural and artificial intelligence

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

non present