Optoelectronic properties of triphenylamine based dyes for solar cell applications. A DFT study

Indexación: Scopus.GSM thanks to the Department of Chemistry at the Universidad Andres Bello, Concepcion, Chile. LHMH gratefully acknowledges financial support from CONACYT (Projects CB2015-257823) and to the Universidad Autónoma del Estado de Hidalgo.Dye-sensitized solar cells (DSSCs) based on triphenylamine (TPA) as a donor group linked with the acceptor cyanoacrylic acid electron acceptor by 2,2'-bithiophene as π-bridged (D-π-A) has been investigated by Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level of theory, to establish the conformational orientation of cyanoacrylic acid group as well as evaluate the effect of planarizing the 2,2'-bithiophene unit in position 3 and 3' by electron withdrawing or donor groups on the electronic structure properties of ground and doping(n,p) states. Also, the Time Dependent Density Functional Theory (TD-DFT) at the CPCM-TD-CAM-B3LYP//CAM-B3LYP/6-311G(d,p) level of theory were selected to modulate the electronic absorption spectra and charge-transfer capabilities of the molecules analyzed in the present work. The results indicate that adding an auxiliary donor or withdrawing group to the 2,2'-bithiophene in the (D-π-A) arrangement allow to modify the LUMO's energy of the dyes, while the HOMO's energy is slightly affected. © 2018 Sociedade Brasileira de Quimica. All rights reserved.http://quimicanova.sbq.org.br/imagebank/pdf/AR20170232.pd

Exactly Marginal Operators and Duality in Four Dimensional N=1 Supersymmetric Gauge Theory

We show that manifolds of fixed points, which are generated by exactly marginal operators, are common in N=1 supersymmetric gauge theory. We present a unified and simple prescription for identifying these operators, using tools similar to those employed in two-dimensional N=2 supersymmetry. In particular we rely on the work of Shifman and Vainshtein relating the \bt-function of the gauge coupling to the anomalous dimensions of the matter fields. Finite N=1 models, which have marginal operators at zero coupling, are easily identified using our approach. The method can also be employed to find manifolds of fixed points which do not include the free theory; these are seen in certain models with product gauge groups and in many non-renormalizable effective theories. For a number of our models, S-duality may have interesting implications. Using the fact that relevant perturbations often cause one manifold of fixed points to flow to another, we propose a specific mechanism through which the N=1 duality discovered by Seiberg could be associated with the duality of finite N=2 models.Comment: 35 pages, 7 Postscript figures, uses revtex.sty (revised version corrects some important details, tex problems

Tuning the electronic, photophysical and charge transfer properties of small D-A molecules based on Thienopyrazine-terthienyls by changing the donor fragment: A DFT study

Indexación: Scopus.Four acceptor-donor organic conjugated molecules based on thieno[3,4-b]pyrazine-terthienyls were analyzed in order to explore the effect of the donor substituent on their molecular structures, electronic and optical properties. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD/DFT) calculations were carried out employing the B3LYP hybrid functional in combination with the 6-31G(d,p) basis set. The results suggests that the addition of electron-donating substituents to the conjugated molecules can diminish their energy gap value, which is beneficial to the photon harvesting. The lowest-lying absorption spectra of compounds substituted with electron donor groups exhibited a red-shift and a high oscillation factor compared with the unsubstituted molecule. Additionally, the ionization potential (IP), electron affinity (EA), reorganization energy (λ) and open-circuit voltage (Voc) of the molecules were evaluated. According to these values, the molecules show good photovoltaic properties, and efficient charge transfer for hole and electron and balanced charges.https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0717-97072017000303637&lng=en&nrm=iso&tlng=e

Orexin 1 receptors in the anterior cingulate and orbitofrontal cortex regulate cost and benefit decision-making

Abstract Orexin neurons are discretely localized within the lateral hypothalamus and have widespread projections into all areas of the brain. In addition, several lines of evidence specify that orexins may also participate in the regulation of a variety of affective and cognitive processes. The Orexin-1 receptor (OX1r) is distributed extensively throughout the prefrontal cortex (PFC). Delay-based decision- making is mediated largely by the orbitofrontal cortex (OFC) while effort- based decision-making is controlled by the anterior cingulated cortex (ACC). Hence, in the present study, a series of experiments were conducted to clarify the role of OX1r in the mPFC (ACC and/or OFC) in cost and benefit decision-making. The rats were trained in a delay and/or effort-based form of cost-benefit T-maze decision-making task. Two goal arms were different in the amount of accessible reward and cost. Before surgery, all animals were selecting the high reward arm and pay the cost on almost every trial. During the test days, the rats received local injections of either DMSO 20% /0.5 μl, as a vehicle, or SB334867 (3, 30 and 300 nM/0.5 μl), as a selective OX1r antagonist, within the ACC and/or OFC. The results of this study showed that the bilateral microinjection of SB334867 into ACC and/or OFC changed the preference to a low reward arm with no cost, indicating the role of OX1 receptors in cost and benefit decision- making. From these results, it can be implied that OX1 receptors in the mPFC play a crucial role for allowing the animal to evaluate and pay the cost to acquire greater rewards. Keywords Delay-based decision-making Effort-based decision-making Orexin Orbitofrontal cortex Anterior cingulate cortex Ra

The role of fatty acid structure in various pure vegetable oils on flame characteristics and stability behavior for industrial furnace

This study investigates the effects of the fatty acid composition of various vegetable oils on the behavior of flames in the combustion process. The research is important for the substitution of fossil fuel using environmentally friendly vegetable oil. Five oils were tested including coconut oil, palm kernel oil, cotton seed oil, ceiba petandra oil and jatropha curcas oil. The oils were burned on an open tray at various air speeds performing three combustion regions, i. e., premixed combustion at the upstream region followed by transition region and diffusion combustion region at the downstream. Flame stability was tested at an air speed of 49 cm/s, 55 cm/s, and 64 cm/s. The image of the flame was recorded using a high-speed video camera at the rate of 200 frames per second. The flame temperature was measured by the K-type thermocouple. The results show that the higher saturated fatty acid content makes the flame brighter and more wavelet numbers present at the flame front maintaining the flame stability at a wide range of air speeds. The saturated fatty acid has a high flash point which is difficult to be burned at the flame front and escaping to burn as diffusion flame at the downstream region. The fatty acid content also affects the flame color which is evident in jatropha curcas oil with mostly a premixed/blue flame color and producing the highest thermal energy, while coconut oil is mostly a diffusion flame/yellow color. The longer ignition delay is shown in coconut oil because of the high saturated fatty acid content. The higher the unsaturated fatty acid content makes the flame more unstable. This shows that the bright yellow diffusion flame color is a good source of radiation thermal energy for flame stability. The flame color and the flame stability data are very valuable for designing efficient and stable industrial furnace with vegetable oil. This study gives insight into the influence of fatty acid chemical structure and physical properties on the combustion characteristics for thermal energy production. When high-temperature gas is needed in the industrial furnace, vegetable oil with unsaturated fatty acids is the choice by keeping the lower air speed. But when the industrial furnace with stable combustion process is the goal, the oil with saturated fatty acids is the best for a wide range of air speeds

The cell biologist's guide to super-resolution microscopy

Fluorescence microscopy has become a ubiquitous method to observe the location of specific molecular components within cells. However, the resolution of light microscopy is limited by the laws of diffraction to a few hundred nanometers, blurring most cellular details. Over the last two decades, several techniques – grouped under the ‘super-resolution microscopy’ moniker – have been designed to bypass this limitation, revealing the cellular organization down to the nanoscale. The number and variety of these techniques have steadily increased, to the point that it has become difficult for cell biologists and seasoned microscopists alike to identify the specific technique best suited to their needs. Available techniques include image processing strategies that generate super-resolved images, optical imaging schemes that overcome the diffraction limit and sample manipulations that expand the size of the biological sample. In this Cell Science at a Glance article and the accompanying poster, we provide key pointers to help users navigate through the various super-resolution methods by briefly summarizing the principles behind each technique, highlighting both critical strengths and weaknesses, as well as providing example images

The role of fatty acid structure in various pure vegetable oils on flame characteristics and stability behavior for industrial furnace

This study investigates the effects of the fatty acid composition of various vegetable oils on the behavior of flames in the combustion process. The research is important for the substitution of fossil fuel using environmentally friendly vegetable oil. Five oils were tested including coconut oil, palm kernel oil, cotton seed oil, ceiba petandra oil and jatropha curcas oil. The oils were burned on an open tray at various air speeds performing three combustion regions, i. e., premixed combustion at the upstream region followed by transition region and diffusion combustion region at the downstream. Flame stability was tested at an air speed of 49 cm/s, 55 cm/s, and 64 cm/s. The image of the flame was recorded using a high-speed video camera at the rate of 200 frames per second. The flame temperature was measured by the K-type thermocouple. The results show that the higher saturated fatty acid content makes the flame brighter and more wavelet numbers present at the flame front maintaining the flame stability at a wide range of air speeds. The saturated fatty acid has a high flash point which is difficult to be burned at the flame front and escaping to burn as diffusion flame at the downstream region. The fatty acid content also affects the flame color which is evident in jatropha curcas oil with mostly a premixed/blue flame color and producing the highest thermal energy, while coconut oil is mostly a diffusion flame/yellow color. The longer ignition delay is shown in coconut oil because of the high saturated fatty acid content. The higher the unsaturated fatty acid content makes the flame more unstable. This shows that the bright yellow diffusion flame color is a good source of radiation thermal energy for flame stability. The flame color and the flame stability data are very valuable for designing efficient and stable industrial furnace with vegetable oil. This study gives insight into the influence of fatty acid chemical structure and physical properties on the combustion characteristics for thermal energy production. When high-temperature gas is needed in the industrial furnace, vegetable oil with unsaturated fatty acids is the choice by keeping the lower air speed. But when the industrial furnace with stable combustion process is the goal, the oil with saturated fatty acids is the best for a wide range of air speeds

Nonlinear photonics properties of porphyrins nanocomposites and self-assembled porphyrins

Two major reasons limit porphyrins photonic applications: (i) the difficulty of handling them in liquid solutions and (ii) their degradation with long exposure to light. This necessitates the use of appropriate solid matrices to host the porphyrin compounds such as Nafion (117), a stable and inert ion exchange polymer. The first part of this publication confirms such a possibility. In addition to their effective NLO properties, an enhancement of the Soret and Q-bands absorbance width have been observed by blending three different porphyrin molecules in the Nafion column matrix membrane. This is an important development towards achieving efficient photon-harvesting medium for possible application in photonic devices. The second part of this contribution reports on the self-assembly/molecular recognition of a specific class of porphyrins giving rise to tubular nano-systems with potential THG nonlinear properties