Structural determination, characterization and computational studies of doped semiconductors base silicon phthalocyanine dihydroxide and dienynoic acids.

The chemical doping of silicon phthalocyanine dihydroxide (SiPc(OH)2), with (2E, 4Z)-5, 7-diphenylhepta-2, 4-dien-6-ynoic acids (DAc) with electron-withdrawing (BrDAc) and electron-donating (MeODAc) substituents is the main purpose of this work. Theoretical calculations were carried out on Gaussian16 software, with geometrical optimization of all involved species, and obtention of the highest occupied molecule orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the respective energy gaps. The theoretical calculations show two hydrogen bridge formations: the first one as a peripheral interaction between the terminal oxygen atoms from the acid unit and hydrogen atoms from the phthalocyanine aromatic rings. The second one as the interaction at the nitrogen atoms of the phthalocyanine, which are compelled to form a new flat plane far from the original flat phthalocyanine deck. These organic semiconductors were deposited as thin films and characterized by IR spectroscopy, atomic force microscopy (AFM), and the optical parameters were gathered from UV-Vis studies. The indirect and direct optical band gap, the onset gap and the Urbach energy were obtained. In order to compare the effect of the acids as dopants of the silicon phthalocyanine, the SiPc(OH)2-DAc films were electrically characterized. The SiPc(OH)2-DAc films exhibit an ambipolar electrical behavior, which is influenced by the incidence of different lighting conditions at voltages above 0.3V. The glass/ITO/SiPc(OH)2-MeODAc/Ag reaches a maximum current of 5.68 × 10-5 A for natural light condition, while the glass/ITO/SiPc(OH)2-BrDAc/Ag, reaches a maximum current of 9.21 × 10-9 A for white illumination condition.

Using Recycled Tetrapak and Doped Titanyl/Vanadyl Phthalocyanine to Make Solid-State Devices.

In this work we studied the semiconductor behavior of titanyl phthalocyanine (TiOPc) and vanadyl phthalocyanine (VOPc), doped with anthraflavic acid and deposited on Tetrapak/graphite as flexible electrodes. The molecular structure was approached using the density functional theory and astonishingly, it was found that the structure and electronic behavior can change depending on the metal in the phthalocyanine. Experimentally, the Root Mean Square was found to be 124 and 151 nm for the VOPc-Anthraflavine and TiOPc-Anthraflavine films, respectively, and the maximum stress was 8.58 MPa for the film with VOPc. The TiOPc-Anthraflavine film presents the smallest fundamental gap of 1.81 eV and 1.98 eV for indirect and direct transitions, respectively. Finally, the solid-state devices were fabricated, and the electrical properties were examined. The tests showed that the current-voltage curves of the devices on Tetrapak and VOPc-Anthraflavine on a rigid substrate exhibit the same current saturation behavior at 10 mA, which is achieved for different voltage values. Since the current-voltage curves of the TiOPc-Anthraflavine on a rigid substrate presents a defined diode model behavior, it was approximated by nonlinear least squares, and it has been determined that the threshold voltage of the sample for the different lighting conditions is between 0.6 and 0.8 volts.

Synthesis and Characterization of a Photocatalytic Material Based on Raspberry-like SiO2@TiO2 Nanoparticles Supported on Graphene Oxide.

A raspberry-like SiO2@TiO2 new material supported on functionalized graphene oxide was prepared to reduce titania's band gap value. The material was characterized through different analytical methods such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The band gap value was studied via UV-Vis absorption spectra and determined through the Kubelka-Munk equation. A theoretical study was also carried out to analyze the interaction between the species.

A Route to Understanding the Ethane Adsorption Selectivity of the Zeolitic Imidazolate Framework-8 in Ethane-Ethylene Mixtures.

Ethylene production has a negative environmental impact, with its separation step being one of the major contributors of pollution. This has encouraged the search for energy-efficient alternatives, among which the adsorptive separation of ethane and ethylene stands out. ZIF-8 is a molecular sieve that is potentially useful for this purpose. It is selective to ethane, an exceptional property that remains unexplained. Furthermore, the adsorption of ethane and ethylene above room temperature, such as at steam cracking process outlet temperatures, has not been addressed either. This work aims to fill this knowledge gap by combining experiments at very low volumetric fillings with density-functional theory modelling methods. Adsorption isotherms of ethane and ethylene on ZIF-8 at pressures below 0.3 bar and 311 K, 333 K, and 363 K were measured using zero-length column chromatography. The low-pressure domain of the isotherms contains information on the interactions between the adsorbate molecules and the adsorbent. This favors the understanding of their macroscopic behavior from simulations at the atomic level. The isosteric enthalpy of adsorption of ethane remained constant at approximately -10 kJ/mol. In contrast, the isosteric enthalpy of adsorption of ethylene decreased from -4 kJ/mol to values akin to those of ethane as temperature increased. ZIF-8 selectivity to ethane, estimated from ideal adsorbed solution theory, decreased from 2.8 to 2.0 with increasing pressure up to 0.19 bar. Quantum mechanical modelling suggested that ethylene had minimal interactions with ZIF-8, while ethane formed hydrogen bonds with nitrogen atoms within its structure. The findings of this research are a platform for designing new systems for the adsorptive separation of ethane and ethylene and thus, reducing the environmental impact of ethylene production.

Preparation of Hybrid Films Based in Aluminum 8-Hydroxyquinoline as Organic Semiconductor for Photoconductor Applications.

In the present work, we have investigated an organic semiconductor based on tris(8-hydroxyquinoline) aluminum (AlQ3) doped with tetracyanoquinodimethane (TCNQ), which can be used as an organic photoconductor. DFT calculations were carried out to optimize the structure of semiconductor species and to obtain related constants in order to compare experimental and theoretical results. Subsequently, AlQ3-TCNQ films with polypyrrole (Ppy) matrix were fabricated, and they were morphologically and mechanically characterized by Scanning Electron Microscopy, X-ray diffraction and Atomic Force Microscopy techniques. The maximum stress for the film is 8.66 MPa, and the Knoop hardness is 0.0311. The optical behavior of the film was also analyzed, and the optical properties were found to exhibit two indirect transitions at 2.58 and 3.06 eV. Additionally, photoluminescence measurements were carried out and the film showed an intense visible emission in the visible region. Finally, a photoconductor was fabricated and electrically characterized. Applying a cubic spline approximation to fit cubic polynomials to the J-V curves, the ohmic to SCLC transition voltage VON and the trap-filled-limit voltage VTFL for the device were obtained. Then, the free carrier density and trap density for the device were approximated to n0=4.4586×10191m3 and Nt=3.1333×10311m3, respectively.

CO2 capture and a route to transform it in formic acid: a theoretical approach.

New organic frameworks (COFs) employing two coronene molecules forced to adopt a parallel conformation thus forming a molecular reactor are proposed. These COFs exhibit different distances between the coronene units, thus creating diverse electronic environments. The simulation of the trapping of CO2 and H2 molecules in the reactor hollow having distinct anchor fragments yields in the two cases formic acid. The analysis of the reaction profile allowed us to propose a thermodynamically favored process. The nature of the frontier molecular orbitals in the involved processes is also discussed. Reaction profile of CO2 and H2 process to yield formic acid.

Feedlot pens with greenhouse roofs improve beef cattle performance in temperate weather.

Muddy pens can negatively affect welfare and performance of feedlot beef cattle. In some regions with temperate weather, plastic greenhouse covers, above the entire pens are used to fatten cattle in a clean and dry environment. The objective of this research was to investigate effects of greenhouse roofed pens on beef cattle feedlot performance in temperate weather. Data were collected from a feedlot located in Central Mexico between 2016 and 2019. The study included 1,062 closeouts of pens with 68,305 crossbred bulls fed in pens with or without a greenhouse roof. Feeding ranged from 82 to 210 d, depending on the initial weight of cattle, which ranged from 255 to 511 kg. For each pen, average daily dry matter intake (DMI; kg of DMI·animal-1·d-1), average daily gain (ADG, kg·animal-1·d-1), and feed efficiency (G:F, ADG/DMI) were measured. Factorial analyses were performed to test the interaction and main effects of initial weight grouping (light, medium, and heavy), roof, and season as fixed effects, and year as a random effect. None of the three-way interactions were significant (P > 0.51). There was no initial weight grouping × roof interactions for DMI and ADG (P > 0.31). There was (P = 0.03) an initial weight grouping × roof interaction for G:F, as pens of all initial weight groups had greater (P < 0.01) G:F in pens with greenhouse roof than its counterpart in pens without greenhouse roof, but the advantage was greater for pens with light cattle (0.178 vs. 0.166; P < 0.01). There was no initial weight grouping × season interactions for all variables (P > 0.39). There was no roof × season interaction for DMI (P = 0.47), but there were interactions for ADG and G:F (P < 0.01). The ADG was not different (P > 0.13) during summer and autumn based on the roofing system, but pens with greenhouse roofs had greater ADG during spring (1.70 vs. 1.61) and winter (1.68 vs. 1.64; P ≤ 0.01). The G:F was greater (P < 0.01) in all seasons for pens with a greenhouse roof, with the most prominent advantage during spring (0.173 vs. 0.160). There were main effects for cattle initial weight grouping and roof for all variables (P < 0.01). Season affected DMI and G:F (P < 0.01). Pens with greenhouse roofs had decreased DMI (9.70 vs. 9.86), greater ADG (1.67 vs. 1.63), and increased G:F (0.173 vs. 0.166) compared to pens without greenhouse roofs (P < 0.01). Pens with greenhouse roofs in feedlots located in temperate regions positively affect beef cattle performance.

Open surgery for in utero repair of spina bifida: Microneurosurgery versus standard technique - A systematic review.

BACKGROUND/OBJECTIVES: Prenatal myelomeningocele (MMC) repair has been shown to improve neurological outcomes. It has been suggested that decreases in the hysterotomy diameter during surgery can improve perinatal outcomes without altering neurologic outcomes. The objective of this study is to describe and compare the main maternal and fetal outcomes of fetuses undergoing open surgery for MMC repair, through the different modifications (standard-classical, mini-hysterotomy, and microneurosurgery). DATA SOURCE: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Ovid, SciELO, LILACS, PROSPERO. RESULTS: From a total of 112 studies, seven case series were selected including 399 fetuses with open fetal surgery, five studies using the classical technique (n = 181), one with mini-hysterotomy (n = 176), and one with the microneurosurgery technique (n = 42). The mini-hysterotomy and microneurosurgery techniques presented a lower risk of preterm delivery (21.4% and 30%, respectively) compared to the classic technique (47.3%), premature rupture of membranes (78%, 62%, and 72.5 %, respectively), oligohydramnios (0% and 72.5%, respectively), dehiscence of hysterotomy, maintaining the same frequency of Chiari reversion (78%, 62%, and 72.5%, respectively), postnatal correction requirement (0%, 4.8%, and 5.8%, respectively), and lower frequency of requirement for a ventriculoperitoneal shunt placement (13.0%, 7.5%, and 29.1%, respectively). CONCLUSION: The least invasive techniques (minihysterotomy-microneurosurgery) are possible and reproduceable, as they are associated with better maternal and perinatal outcomes.

Capture of Fullerenes in Cages and Rings by Forming Metal-π Bond Arene Interactions.

Nowadays, the task of the selectively capture of fullerene molecules from soot is the subject of several studies. The low solubility of fullerenes represents a drawback when the goal is to purify them and to carry out chemical procedures where they participate. There are different molecules that can act as a kind of cocoon, giving shelter to the fullerene cages in such a way that they can be included in a solution or can be extracted from a mix. In this work, a theoretical study of some known and new proposed organic molecules of this kind is presented. In all cases, the interaction occurs with the help of a metallic atom or ion which plays the role of a bridge, providing a place for a metallocene like interaction to occur. The thermodynamic arguments favoring the formation of this adduct species are addressed as well as the nature of the bond by means QTAIM parameters and frontier molecular orbitals analysis.

A Comparative Study of the Semiconductor Behavior of Organic Thin Films: TCNQ-Doped Cobalt Phthalocyanine and Cobalt Octaethylporphyrin.

The structure formed by cobalt phthalocyanine (CoPc) and cobalt octaethylporphyrin (CoOEP) with electron-acceptor tetracyano-π-quinodimethane (TCNQ), was studied by Density Functional Theory (DFT) methods. According to theoretical calculations, both cobalt systems can establish dispersion forces related to TCNQ and also in both cases the link between them is built by means of hydrogen bonds. Based on the results of these DFT calculations, we developed experimental work: the organic semiconductors were doped, and the thermal evaporation technique was used to prepare semiconductor thin films of such compounds. The structure of the films was studied by FTIR and Raman spectroscopy. The optical properties of the CoPc-TCNQ and CoOEP-TCNQ films were investigated by means of UV-Vis measurements. The results obtained were used to estimate the type of transitions and the optical bandgap. The results were compared to the previously calculated theoretical bandgap. The CoOEP-TCNQ film presented the smallest theoretical and experimental bandgap. Finally, the electrical properties of the organic semiconductors were evaluated from a PET (polyethylene terephthalate)/indium tin oxide (ITO)/cobalt macrocycle-TCNQ/silver (Ag) device we prepared. The CoOEP-TCNQ-based device showed an ohmic behavior. The device manufactured from CoPc-TCNQ also showed an ohmic behavior at low voltages, but significantly changed to SCLC (space-charge limited conductivity) at high voltage values.

Comparative Study of Conduction Mechanisms in Disodium Phthalocyanine-Based Organic Diodes for Flexible Electronics.

In the current work, flexible diodes with flat heterojunction and dispersed heterojunction architecture were manufactured with to study the behavior of thin films of disodium phthalocyanine (Na2Pc). The thin film devices, using the electronic acceptor tetracyano-π-quinodimethane (TCNQ), were fabricated by high-vacuum thermal evaporation with annealing post-treatment in order to optimize their behavior. Theoretical calculations based on density functional theory (DFT) with dispersion force analysis were carried out in order to simulate molecular interactions and to establish the nature of the weak interactions between the Na2Pc and TCNQ fragments. In the optimized structure of the coupled Na2Pc-TCNQ, the electronic relationship between phthalocyanine and TCNQ was observed to be through hydrogen bonds with bond lengths of 2.94 and 3.13 Å. Dispersed heterojunction device current density values were considerably larger than those of the flat heterojunction device. Barrier heights of 1.024 and 0.909 eV and charge mobilities of 10-10 and 10-9 m2/Vs for the flat heterojunction device and the dispersed heterojunction device, respectively, were observed. A small effect was observed on the electrical properties by thermal annealing on the flat heterojunction device. The threshold voltage decreased from 1.203 to 1.147 V and φb decreased by 0.001 eV.

Erratum: Del Castillo, R.M., et al. Electronic Peculiarities of a Self-Assembled M12L24 Nanoball (M = Pd+2, Cr, or Mo). Molecules 2019, 24, 771.

The author wishes to make the following correction to this paper [...].

Molecular knot with nine crossings: Structure and electronic properties from density functional theory computation.

The electronic structure of a molecule with nine-crossing composite knots 973 link denoted by the Alexander-Briggs notation (complex-1) are studied by means of theoretical methods (DFT). The most interesting feature of this kind of molecules is their capability to capture anion spices inside the cage. Stability and chemical reactivity were evaluated taking advantage of the criteria chemical hardness and chemical potential. The simulation of the infrared spectra is also included and shows the characteristic signal of the molecule in a range 1000-1600 cm-1. The frontier molecular orbitals were also analyzed. Whereas the capability to capture chlorine ion into the cavity of the complex-1 is explored by means the analysis of bond energy. Also, the electron density distribution of the chlorine complex was studied by means the quantum theory of atoms in molecules (QTAIM) formalism in order to stablish its bonding properties as well as the electron transfer between chlorine ion and complex-1 which was approached by the natural bonding orbital (NBO) and Hirshfeld charge. Ours results revels semiconductor behaviors for both compounds.

Organometallic complexes of carbon nanotori.

New organometallic complexes of carbon nanotori were designed and theoretically described by means of density functional theory. After a systematic structural search, it was found that energetically favorable complexes were formed by the metal atoms Cr and Ni, both located at the center of a nanotorus with diameter around 5 Å and 120 carbon atoms. The nature of the metal-nanotorus interaction shows a partial polar-covalent character, different from those found in other well-known organometallic compounds. Interactions were studied through molecular orbitals and thermodynamic stability. Ten bonds are set up between the metal atom and nanotorus, confirmed by electron density topology analysis, showing ten bond critical points among the metal atoms and the surrounding carbon atoms. The response of the induced electron current caused by a magnetic field perpendicular to the nanotorus was analyzed to explain the electron delocalization and aromaticity of the complexes. Only in the case of the chromium complex, the electron density is fully delocalized on the whole complex. According to a geometry-based index of aromaticity, interaction with the metal atom only changes the aromatic character of the carbon rings slightly. Also, induced currents were used to elucidate the presence of a ferrotoroidal behavior. The isolated nanotorus and its compound with a single Ni atom have well-defined ferrotoroidal behavior because they present broken symmetries and could help to design a topological insulator. Meanwhile, the nanotorus with a Cr atom at the center lacks ferrotoroidal behavior as a consequence of the absence of magnetic vortices. Graphical abstract Organometallic complex of carbon nanotorus with chromium and induced currents on it by applying an external magnetic field.

Rotaxane and pseudo-rotaxane molecules from molecular wires. Theoretical description.

Some rotaxane molecules were designed, and their electronic capabilities were studied by means of DFT calculations. The original molecular wire consists of an iron complex that comprises aromatic substituents that constitute linear chains, and this system is complemented by the addition of fullerene C60 unities at both extremes of the chain, which act as the stoppers of the chain. Another modification was to add a link that gives way to the mechanical bond; this link is a square molecule of bis-pyrydyl-pyridinium tetraion. An interesting effect was observed as a result of these modifications; the conductivity of the systems rises with the first substitution and even more with the second in such a way that the original semiconductor material changes to give a conductor one.

CuPc: Effects of its Doping and a Study of Its Organic-Semiconducting Properties for Application in Flexible Devices.

This study refers to the doping of organic semiconductors by a simple reaction between copper phthalocyanine and tetrathiafulvalene or tetracyanoquinodimethane. The semiconductor films of copper phthalocyanine, doped with tetrathiafulvalene donor (CuPc-TTF) and tetracyanoquinodimethane acceptor (CuPc-TCNQ) on different substrates, were prepared by vacuum evaporation. The structure and morphology of the semiconductor films were studied with infrared (IR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The absorption spectra for CuPc-TTF, recorded in the 200⁻900 nm UV⁻vis region for the deposited films, showed two peaks: a high energy peak, around 613 nm, and a second one, around 695 nm, with both peaks corresponding to the Q-band transition of the CuPcs. From the spectra, it can also be seen that CuPc-TTF has a B-band at around 330 nm and has a bandgap of approximately 1.4 eV. The B-band in the CuPc-TCNQ spectrum is quite similar to that of CuPc-TTF; on the other hand, CuPc-TCNQ does not include a Q-band in its spectrum and its bandgap value is of approximately 1.6 eV. The experimental optical bandgaps were compared to the ones calculated through density functional theory (DFT). In order to prove the effect of dopants in the phthalocyanine semiconductor, simple devices were manufactured and their electric behaviors were evaluated. Devices constituted by the donor-acceptor active layer and by the hollow, electronic-transport selective layers, were deposited on rigid and flexible indium tin oxide (ITO) substrates by the vacuum sublimation method. The current⁻voltage characteristics of the investigated structures, measured in darkness and under illumination, show current density values of around 10 A/cm² for the structure based on a mixed-PET layer and values of 3 A/cm² for the stacked-glass layered structure. The electrical properties of the devices, such as carrier mobility (µ) were obtained from the J⁻V characteristics. The mobility values of the devices on glass were between 1.59 × 108 and 3.94 × 1010 cm²/(V·s), whereas the values of the devices on PET were between 1.84 × 108 and 4.51 × 108 cm²/(V·s). The different behaviors of the rigid and flexible devices is mainly due to the effect of the substrate.

Electronic Peculiarities of a Self-Assembled M12L24 Nanoball (M = Pd+2, Cr, or Mo).

We use molecular mechanics and DFT calculations to analyze the particular electronic behavior of a giant nanoball. This nanoball is a self-assembled M12L24 nanoball; with M equal to Pd+2; Cr; and Mo. These systems present an extraordinarily large cavity; similar to biological giant hollow structures. Consequently, it is possible to use these nanoballs to trap smaller species that may also become activated. Molecular orbitals, molecular hardness, and Molecular Electrostatic Potential enable us to define their potential chemical properties. Their hardness conveys that the Mo system is less reactive than the Cr system. Eigenvalues indicate that electron transfer from the system with Cr to other molecules is more favorable than from the system with Mo. Molecular Electrostatic Potential can be either positive or negative. This means that good electron donor molecules have a high possibility of reacting with positive regions of the nanoball. Each of these nanoballs can trap 12 molecules, such as CO. The nanoball that we are studying has large pores and presents electronic properties that make it an apposite target of study.

Cycloaddition reactions of pristine and endohedral fullerene molecules: possible anticancer activity.

Epoxide of oestradiol is one of the main risk factors for the genesis and evolution of breast cancer; hence, in recent years there has been considerable interest in the investigation of new inhibitors capable of reducing its carcinogenic activity. The aim of this article is to study the [2 + 2] cycloaddition reaction of epoxide of oestradiol in different pristine (C76 and D5h-C80) and endohedral metallofullerene (C72@Sc2C2, C76@Sc2 and C80@Sc2) by means of molecular electrostatic potential (MEP) topological analysis. Different from other molecular scalar fields, MEP topology enables to find minima related to lone pairs and π electrons, therefore, this molecular scalar field is appropriate to identify the most reactive sites. In consonance with our results, it was found that C80 was the best candidate to carry out the epoxide of oestradiol cycloaddition since more stable adducts were obtained. Furthermore, it is expected that more than one oestradiol epoxide molecule will be added to C80, forasmuch as C80 reactivity is enhanced once the adduct is formed. The study was carried through DFT framework included in the Gaussian 09 package (MPWB95/6-31G(d,p)).

Schiff base complexes that form sandwich compounds.

In this article, we explore the capacity of formed Schiff base complexes to trap metal atoms or ions, using their aromatic ends. The intrinsic geometry of each complex defines the process of substitution. Two cases were studied; one involving a trans Schiff base complex and the other considering how a salen ligand, with nickel systems traps chromium. We also assessed the nature of the new bonds and the frontier molecular orbitals. Graphical abstract Two salen nickel compounds are joint by a Cr(0) atom forming an organometallic interaction.

Exohedral complexes of large fullerenes, a theoretical approach.

The possibility of existence of exohedral organometallic complexes of fullerenes larger than C60 in which their coordination can have η6 hapticity was studied from a theoretical point of view. Complexes containing C70, C74 or C60 cages, as well as cyclopentadienyl (Cp), pentamethyl-cyclopentadienyl (Me5Cp), benzene rings and hexamethyl-phenyl (Me6Ph) fragments as ligands, were designed and studied. The results show that many of these molecules can be thermodynamically stable and can have electronic interesting behavior.