1,721,208 research outputs found
Exploring Rapid Photocatalytic Degradation of Organic Pollutants with Porous CuO Nanosheets: Synthesis, Dye Removal, and Kinetic Studies at Room Temperature
Get PDFIn this work, we report the facile, environmentally friendly, room-temperature (RT) synthesis of porous CuO nanosheets and their application as a photocatalyst to degrade an organic pollutant/food dye using NaBH4 as the reducing agent in an aqueous medium. Ultrahigh-resolution field effect scanning electron microscopy images of CuO displayed a broken nanosheet-like (a length of ∼160 nm, a width of ∼65 nm) morphology, and the lattice strain was estimated to be ∼1.24 × 10-3 using the Williamson-Hall analysis of X-ray diffraction plots. Owing to the strong quantum size confinement effect, CuO nanosheets resulted in an optical energy band gap of ∼1.92 eV, measured using Tauc plots of the ultraviolet-visible (UV-vis) spectrum, resulting in excellent photocatalytic efficiency. The RT synthesized CuO catalyst showed a high Brunauer-Emmet-Teller surface area of 30.88 ± 0.2313 m2/g (a correlation coefficient of 0.99972) with an average Barrett-Joyner-Halenda pore size of ∼20.385 nm. The obtained porous CuO nanosheets exhibited a high crystallinity of 73.5% with a crystallite size of ∼12 nm and was applied as an efficient photocatalyst for degradation of the organic pollutant/food dye, Allura Red AC (AR) dye, as monitored by UV-vis spectrophotometric analysis and evidenced by a color change from red to colorless. From UV-vis spectra, CuO nanosheets exhibited an efficient and ultrafast photocatalytic degradation efficiency of ∼96.99% for the AR dye in an aqueous medium within 6 min at RT. According to the Langmuir-Hinshelwood model, photodegradation reaction kinetics followed a pseudo-first-order reaction with a rate constant of k = 0.524 min-1 and a half-life (t1/2) of 2.5 min for AR dye degradation in the aqueous medium. The CuO nanosheets showed an outstanding recycling ability for AR degradation and would be highly favorable and an efficient catalyst due to the synergistic effect of high adsorption capability and photodegradation of the food dye. © 2021 The Authors. Published by American Chemical Society1
Actuators Based on Hydrogels
No full textMany electronic actuators of different dimensions, such as motors, relays, pumps, and mixers, have evolved rapidly, and many are commercially available. Its application into soft environments such as biological tissues is desirable to develop automated biomedical devices. However, they present innate difficulties. Limitations are mainly due to its structural rigidity and chemical composition. To address this need, soft‐actuators are under development. These devices have great mechanical and chemical similarity with biological tissues and, as a consequence, many have a high biocompatibility. Soft‐actuators are capable of mimicking the behavior of muscles or other tissues that are involved in locomotion in biological organisms. Most of them are hydrogels which are polymers structured in three‐dimensional networks, capable of harboring large amounts of water. Hydrogels can reversibly change its volume up to 50, 100 times, or more, from a dried or collapsed state to a hydrated state. This shape shifting can be triggered by external stimuli such as: pH, temperature, humidity, light, presence of specific molecules, among others. In this work, we present important concepts of the properties, synthesis and characterization of hydrogels. Subsequently, the main characteristics of actuators are detailed, and the results of these works are explained with to the previously described properties.Fil: Wolfel Sánchez, Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Romero, Marcelo Ricardo. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentin
Al-Doped CoP nanoarray: a durable water-splitting electrocatalyst with superhigh activity
No full textThe scalable production of hydrogen fuel through electrochemical water reduction needs efficient Earth-abundant electrocatalysts to make the whole water-splitting process more energy efficient. In this Article, we report that an Al-doped CoP nanoarray on carbon cloth (Al-CoP/CC) behaves as a durable hydrogen evolution electrocatalyst with superhigh activity in 0.5 M H2SO4. It demands a pretty low overpotential of 23 mV to drive a geometrical catalytic current density of 10 mA cm(-2), outperforming all reported non-precious metal catalysts. Density functional theory calculations reveal that Al-CoP has a more thermo-neutral hydrogen adsorption free energy than CoP. Notably, this Al-CoP/CC is also superior in activity and durability as a bifunctional catalyst for alkaline water electrolysis, and its two-electrode water electrolyser delivers 10 mA cm(-2) water-splitting current at a cell voltage of 1.56 V in 1.0 M KOH. This work offers us an attractive cost-effective catalyst electrode in water-splitting devices for large-scale production of hydrogen fuels
Nanofiber Research
No full textThis book titled Nanofiber Research - Reaching New Heights contains a number of latest research results on growth and developments on material fibers in nanoscale. It is a promising novel research area that has received a lot of interest in recent years. This book includes interesting reports on cutting-edge science and technology related to synthesis, morphology, control, self-assembly and prospective application of nanofibers. I hope that the book will lead to systematization of nanofiber science, creation of new nanofiber research field and further promotion of nanofiber technology. This potentially unique work offers various approaches on the implementation of nanofibers. As it is widely known, nanotechnology presents the control of matter at the nanoscale and nano-dimensions within few nanometers, whereas this exclusive phenomenon enables us to regulate and control novel applications with nanofibers. This book presents an overview of recent and current nanofibers fundamental, significant applications and implementation research worldwide. It examined the methods of nanofiber synthesis, types of fibers used and potential applications associated with nanofiber researches. It is an important booklet for research organizations, governmental research centers, academic libraries and R&D affianced in recent research and development of nanofibers
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Efficient Hydrogen Evolution Electrocatalysis at Alkaline pH by Interface Engineering of Ni2P-CeO2
No full textIt is of significant importance to develop effective non-noble-metal catalysts for hydrogen evolution electrocatalysis under basic conditions. In this study, we demonstrate the facile construction of a Ni2P-CeO2 interface based on the central point that low-temperature phosphidation of the NiO-CeO2 precursor only converts NiO into Ni2P selectively. The resulting Ni2P-CeO2 nanosheet array on Ti mesh behaves as a durable catalyst for alkaline hydrogen evolution reaction (HER) electrocatalysis, and it can reach 20 mA cm(-2) at an overpotential of 84 mV in 1.0 M KOH, outperforming all reported Ni phosphide HER catalysts. Density functional theory calculations reveal that the Ni2P-CeO2 interface can promote water dissociation and optimize hydrogen adsorption free energy
Benzoate Anion-Intercalated Layered Cobalt Hydroxide Nanoarray: An Efficient Electrocatalyst for the Oxygen Evolution Reaction
No full textEfficient oxygen evolution reaction (OER) catalysts are highly desired to improve the overall efficiency of electrochemical water splitting. We develop a benzoate anion-intercalated layered cobalt hydroxide nanobelt array on nickel foam (benzoate-Co(OH)(2)/NF) through a one-pot hydrothermal process. As a 3D electrode, benzoate-Co(OH)(2)/NF with an expanded interlayer spacing (14.72 angstrom) drives a high OER catalytic current density of 50mAcm(-2) at an overpotential of 291mV, outperforming its carbonate anion-intercalated counterpart with a lower interlayer spacing of 8.81 angstrom (337mV overpotential at 50mAcm(-2)). Moreover, this benzoate-Co(OH)(2)/NF can maintain its catalytic activity for 21h
Synthesis, spectroscopic (UV-vis and GIAO NMR), crystallographic and theoretical studies of triazine heterocyclic derivatives
No full textThis work presents the synthesis and characterization of triazine heterocyclic derivatives. The spectroscopic properties like nuclear magnetic resonance [NMR, (1H and 13C)] were recorded in CDCl3 solution and Ultraviolet-Visible (UV-vis) absorption spectrums of compounds, 5,6-diphenyl-[1,2,4]triazin-3-ylamine (1), (5,6-diphenyl-[1,2,4]triazin-3-yl)-hydrazine (2) and 5,6-diphenyl-4H-[1,2,4] triazine-3-thione (3), were recorded in the range of 200-800 nm, using chloroform as base solvent. Molecular geometry of compounds with triazine heterocyclic derivative in the ground state have been calculated using the density functional theory (DFT) with 6-31G(d,p) basis set and compared with the X-ray experimental data. The calculated results show that the optimized geometry can well reproduce the crystal structures. Total static dipole moment (?), the average linear polarizability (?) and the first hyperpolarizability (?) values of the investigated molecules have been computed using the same methods. The energetic behavior of compounds in solvent media has been examined using B3LYP method with the 6-31G(d,p) basis set by applying the polarizable continuum model (PCM). The total energy of compounds decreases with increasing polarity of the solvent. Frontier molecular orbitals and the molecular electrostatic potential (MEP), 1H-NMR, and 13C-NMR of three triazine derivatives were investigated using theoretical calculations. The linear polarizabilities and first hyperpolarizabilities of the studied molecules indicate that the compounds 1-3 can be used as a good nonlinear optical material (NLO). Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method. Comparison of the NMR chemical shifts, absorption wavelengths with the experimental values revealed that DFT and time dependent-density functional theory (TD-DFT) method produce generally closer to good results
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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