Search results for "Chemical engineering"
showing 10 items of 5892 documents
In Situ Synthesis of Polythiophene and Silver Nanoparticles within a PMMA Matrix: A Nanocomposite Approach to Thermoelectrics
2022
The processability of organic thermoelectric materials plays a crucial role due to their clear advantages of applicability in large-scale areas compared to traditional inorganic counterparts. A promising way to process thermoelectric materials based on conductive polymers is through in situ polymerization in an insulating polymer matrix. This work shows an interpenetrating polymeric network based on polythiophene, silver nanoparticles (Ag NPs), and poly(methyl methacrylate) (PMMA) produced by the oxidative polymerization of terthiophene by an oxidizing silver salt in a PMMA matrix. Ag NPs are in situ synthesized simultaneously as a byproduct. The reaction occurs very fast in the solid state…
¿La esquizofrenia empieza en la adolescencia?
2005
La esquizofrenia es una grave enfermedad mental que se encuentra asociada a una importante morbilidad, a diferencia de otras enfermedades, los síntomas esquizofrénicos en general no se presentan por décadas. En la mayoría de los pacientes, el inicio manifiesto de la enfermedad está precedido por los síntomas prodrómicos, que incluyen síntomas positivos, negativos, afectivos y aislamiento social. Existen diversas teorías sobre la etiopatogenia de la esquizofrenia, algunas de ellas basadas en factores genéticos, ambientales (por ejemplo, stress), disfunciones moleculares y alteraciones en el desarrollo y en la migración neuronal. Una interesante hipótesis sostiene la influencia de…
Enhanced Thin-Film Transistor Performance by Combining 13,6-N-Sulfinylacetamidopentacene with Printed PEDOT:PSS Electrodes
2011
Bottom-contact/bottom-gate organic thin-film transistors (OTFTs) are fabricated using a soluble pentacene precursor (13,6-N-sulfinylacetamidopentacene; SAP) and inkjet printed PEDOT:PSS electrodes on bare SiO2 dielectrics. Saturation mobility, Ion/Ioff ratio, and threshold voltage parameters, respectively, of 0.27 cm2 V−1 s−1, 105, and −4.25 V were measured under ambient conditions after the thermal conversion of SAP to pentacene in 100 μm long channel OTFT devices. The results obtained by the above solution approach are comparable to that of vapor-phase grown pentacene-based OTFTs with photolithographic gold contacts and organic buffer layers and/or inorganic injection layers. The present …
More than a Confinement: “Soft” and “Hard” Enzyme Entrapment Modulates Biological Catalyst Function
2019
Catalysis makes chemical and biochemical reactions kinetically accessible. From a technological point of view, organic, inorganic, and biochemical catalysis is relevant for several applications, from industrial synthesis to biomedical, material, and food sciences. A heterogeneous catalyst, i.e., a catalyst confined in a different phase with respect to the reagents’ phase, requires either its physical confinement in an immobilization matrix or its physical adsorption on a surface. In this review, we will focus on the immobilization of biological catalysts, i.e., enzymes, by comparing hard and soft immobilization matrices and their effect on the modulation of the catalysts’ function. Indeed, …
On the Complexation of Cu(II) and Cd(II) With Polycarboxyl Ligands. Potentiometric Studies With ISE-H+, ISE-Cu2+, and ISE-Cd2+
2009
The interaction of Cu2+ and Cd2+ ions with polyacrylates (PAA, 2 kDa and 100 kDa), polymetacrylate(PMA, 5.4 kDa), and alginate (AA, 70 kDa to 100 kDa) was studied by potentiometry, using ISE-Cu2+, ISE-Cd2+, and ISE-H+ electrodes. The investigations were performed in NaNO3 aqueous solutions, in the ionic strength range 0.10 e I (mol ·L-1) e 0.75, at T ) 298.15 K. The “diprotic-like model” was used to explain the acid-base behavior of the polycarboxylates under investigation (for this model, the monomeric unit of the polyelectrolyte is considered as a dicarboxylate). The results give evidence for the formation of the ML species in all the systems investigated. In addition, the MLH species was…
Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides
2015
Nickel(II) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and…
A new application for nickel foam in alkaline fuel cells
2009
The use of nickel foam as an electrode substrate in alkaline fuel cells (AFCs) has been investigated for bi-polar cells incorporating an electrically conducting gas diffusion layer. This contribution focuses on the cathode, and draws comparisons between nickel foam and nickel mesh substrates. One of the principal electrocatalysts for the cathodic reduction of oxygen is silver, so an improvement in electrochemical performance was obtained by electroplating the nickel foam with silver. The electrodeposition process was optimised to maximise electrochemical performance with a minimum of silver deposited. Nickel foam, which is less expensive than the usual nickel mesh, appears to be a good subs…
Atomic Layer Deposition of Aluminum Oxide on TiO2 and Its Impact on N3 Dye Adsorption from First Principles
2011
The atomic layer deposition of aluminum oxide on an OH-terminated TiO2(101) anatase surface was studied employing density functional theory calculations. The formation of the Al2O3−TiO2 interface during the first atomic layer deposition cycle was modeled by studying the dissociative adsorption of an Al(CH3)3 precursor, followed with a H2O-pulse reaction step that changes the surface termination. Calculations provide evidence for the formation of a discontinuous, atomically rough aluminum oxide layer after the first cycle. To explore the role of the aluminum oxide layer on adsorption of a ruthenium-based N3 dye molecule, various adsorption geometries were investigated. Calculations show that…
The different catalytic behaviour in the propane total oxidation of cobalt and manganese oxides prepared by a wet combustion procedure
2013
Abstract Cobalt oxide and manganese oxide catalysts have been prepared through aqueous synthesis using a wet combustion procedure. These materials have been tested as catalysts for the total oxidation of propane. It has been observed a different catalytic behaviour between cobalt and manganese oxides although for both oxides a very high catalytic activity has been obtained. Cobalt oxides prepared by the wet combustion procedure are less reactive than a simple cobalt oxide prepared without the addition of organic acids. However, in the case of manganese oxide the use of organic acids highly increases the catalytic activity. The different catalytic behaviour has been related to the variation …
A step forward in the development of superoxide dismutase mimetic nanozymes: the effect of the charge of the surface on antioxidant activity
2019
Two binucleating hezaaza macrocycles containing a pyridinol spacer have been prepared and characterised. Protonation studies indicate the deprotonation of the phenol group at relatively low pH values with the concomitant occurrence of a keto-enolic equilibrium. These ligands readily form binuclear Cu2+ and Zn2+ complexes as denoted by potentiometric and spectroscopic studies. The binding of the metals yields to the ready deprotonation of the phenol with the stabilisation of the keto form that results in complexes of greater stabilities than the analogous ones containing pyridine as spacer instead of pyridine. Mixed Cu2+–Zn2+-complexes were also detected in aqueous solutions containing equim…