Carbon Atoms In Chain Research Articles

Interstitial carbon defects in silicon. A quantum mechanical characterization through the infrared and Raman spectra.

The Infrared (IR) and Raman spectra of various interstitial carbon defects in silicon are computed at the quantum mechanical level by using an all electron Gaussian type basis set, the hybrid B3LYP functional and the supercell approach, as implemented in the CRYSTAL code (Dovesi et al. J. Chem. Phys. 2020, 152, 204111). The list includes two 〈100〉 split interstitial IXY defects, namely ICC and ICSi , a couple of related defects that we indicate as IX IY , the so called in its A and B form, as well as SiCi Si and Cs Ci Cs , in which the interstitial carbon atom is twofold coordinated. The second undergoes a large relaxation, and the final configuration is close to ICC Cs . Geometries, relative stabilities, electronic, and vibrational properties are analysed. All these defects show characteristic features in their IR spectrum (above 730 cm- 1 ), whereas the Raman spectrum is dominated, in most of the cases, by the pristine silicon peak at 530 cm-1 , that hides the defect peaks.

Solubility and mass transfer coefficient of oxygen through gas- and water-lipid interfaces.

The solubility of oxygen and its transfer rate to the lipid phase play important roles in lipid oxidation, which affects the taste and safety of lipid-containing foods. In this study, we measured the Henry's constants (solubility) of oxygen for fatty acids, fatty acid esters, and triacylglycerols (TAGs; vegetable oils), as well as the mass transfer coefficients of oxygen at the gas- and water-lipid interfaces. The constants and coefficients were estimated by analyzing the change over time in the oxygen partial pressure or concentration in the closed container based on the mass balance equations of oxygen in the gas and liquid phases. The constant for water obtained by the method used in this study was in agreement with the previously reported value to confirm the validity of the method. The constants for lipids depended on the lipid type, and were higher in the order of fatty acid ester, fatty acid, and TAG. That is, the solubility of oxygen decreased in this order. For all lipids, the constant increased as the number of carbon atoms in the fatty acid chain increased. The constants for fatty acids and their esters were linearly correlated with the enthalpies of evaporation of the lipids. The mass transfer coefficients of oxygen at the gas-liquid interface were on the order of 10-5 m/s for water and methyl dodecanoate and of 10-6 m/s for TAG (rapeseed oil). The coefficient at the water-lipid interface was on the order of 10-6 m/s. PRACTICAL APPLICATION: The Henry's constants (solubility) and transfer rate of oxygen to the lipid phase, fatty acids, fatty acid esters, and triacylglycerols (TAG) were measured. The lipids solubilized three to five times more oxygen than water, and mass transfer rate of oxygen at gas- and water-lipid interfaces were almost same. The constants for fatty acids and fatty acid esters were linearly correlated to their enthalpies of evaporation, and this correlation is expected to be useful for estimating the Henry's constants for other fatty acids and their esters.

N-Alkanes and n-Alkenes in Virgin Olive Oil from Calabria (South Italy): The Effects of Cultivar and Harvest Date.

n-Alkanes and n-alkenes are components of the unsaponifiable fraction of an olive oil. These were analysed by GC on-column analysis and are here proposed as an additional tool to certify the origin, authenticity, traceability and chemical quality of olive oil produced in the Reggio Calabria province (South Italy). Nine cultivars were studied: Cassanese, Coratina, Itrana, Leccino, Nociara, Ottobratica, Pendolino, Picholine and Sinopolese grown in the region of Calabria (South Italy). n-Alkanes in the range from 21 to 35 chain carbon atoms and alkenes in the range from 23:1 to 25:1 chain carbon atoms were found with the following elution order: heneicosane (C21), docosane (C22), tricosene (C23:1), tricosane (C23), tetracosene (C24:1), tetracosane (C24), pentacosene (C25:1), pentacosane (C25), hexacosane (C26), eptacosane (C27), octacosane (C28), nonacosane (C29), triacontane (C30), entriacontane (C31), dotriacontane (C32), tritriacontane (C33), tetratriacontane (C34), pentatriacontane (C35). The oil of all cultivars showed a decreasing trend in total n-alkane and n-alkene content, with the oil of Sinopolese showing the highest content, varying from 328.50 to 214.00 mg/kg. Odd-chain alkanes predominated over even-chain n-alkanes, and tricosane, tetracosane and pentacosane were the most represented alkanes. Cultivar and harvest date significantly influenced the n-alkane and n-alkene content. These findings can be useful to distinguish different olive cultivars and to decide the fruit harvest date for the oil of the Reggio Calabria province (South Italy). A daily quantity of 30 g of olive oil of the Sinoplese cv (the one with the highest n-alkane and n-alkene content) was found to be in accordance with the suggestions of the European Agency for the evaluation of medicinal products Committee for veterinary medicinal products and biogenic hydrocarbons intake for the human diet.

Molecular Dynamics Simulation of Methyl Ester Sulfonates at the Water/Chloroform Interface

Molecular dynamics simulation method was used to investigate distribution properties of methyl ester sulfonates (MES) with different carbon numbers at the chloroform/water interface. We consider a series of surfactant isomers in the family of methyl ester sulfonates, denoted by CnMES, where n is the number of carbon atoms in the alkyl chain. According to the simulation results, a well-stable interface between the chloroform and water phases could form in the presence of MES surfactants. The simulation results show that stability of interface with C18MES is relatively high comparing to C14MES and C16MES. From the comparison of the interfacial thickness obtained by the density profiles, we could realize that the surfactant C16MES cause the lowest interfacial thickness. Furthermore, we found that the system containing C14MES has the largest interfacial thickness as it shows the best miscibility with chloroform among the other surfactants.

Atomic chain of carbon atoms: Smallest negative differential resistance device

In the present work, we report giant negative differential resistance action in probably the simplest molecular nanoelectronic device comprising of carbon chain placed between two ferromagnetic electrodes named as graphitic carbon nitride (g-C4N3). The negative differential resistance action is spin polarized and only evident at spin down channel. Spin polarized quantum transport studies using Keldysh non-equilibrium Green's function based density functional theory reports very high negative differential resistance over the bias range of ±0.1 V to ±0.3 V. This symmetric negative differential resistancec feature has been explained by an analysis of transmission spectrum across the Fermi energy level and Molecular Projected Self-Consistent Hamiltonian states (MPSH) of the system. Role of in-phase and out of phase electron waves in ensuring negative differential resistance feature has been justified through transmission pathways of the system. The simplicity of the molecular system added with robust spin polarized negative differential action added with experimental relevance certainly establishes the uniqueness of the device in respect of modern spintronic research.

HELICAL STRUCTURE OF POLYUNSATURATED FATTY ACIDS: GAUSSIAN G4 THERMODYNAMIC FUNCTIONS

Molecular modeling of lipids has been hampered by the size of these complex, biologically important molecules. Yet, understanding the structure and energy (enthalpy) of large molecules is critical to identifying their function in chemical equilibrium and transition state theory. In this work, we use both experimental data and G4 computed results, to show that cis polyunsaturated lipids have helical conformers. We present linear functions for the enthalpy of formation ΔfH°298 and the Gibbs free energy of formation ΔfG°298 as a function of n, where n is the number of carbon atoms in a linear carboxylic acid chain. Taking ΔfH°298 of a saturated acid as a starting point, we add the enthalpy of hydrogenation ΔhydH°298 at appropriate locations on the carbon chain to model polyunsaturated fatty acids. For example, taking eicosanoic acid (C20) as a saturated starting point, we add four enthalpies of cis-dehydrogenation (ΔhydH°298) to obtain arachidonic acid (eicosa-5Z,8Z,11Z,14Z-tetraenoic acid). We compare Gaussian-4 computational results, to show evidence of helical structure. We conclude that fatty acids can have helical conformers facilitating a broad range of biological functions. Keywords: G4 Calculations, Helix, Lipid, Molecular Structure, Thermochemistry

Reactivity of poly(alkoxycarbonylmethylene)s under basic conditions: alkylation of main chain carbon atoms via a ketene silyl acetal-type intermediate and cleavage of the carbon–carbon main chain

We report the alkylation of main chain carbon atoms and cleavage of the carbon–carbon main chain of poly(alkoxycarbonylmethylene)s.

Effects of anion and alkyl chain length of cation on the thermophysical properties of imidazolium-based ionic liquid

Abstract This study focused on the effects of anions and the alkyl chain length of cations on the thermophysical properties of imidazolium-based ionic liquid (ILs). The data were obtained from references and the NIST database. The studied parameters include the melting temperature (Tm), glass transition temperature (Tg), decomposition temperature (Td), enthalpy of fusion (ΔHm), and thermal conductivity ( λ ). The variations of Tm with the anions in [C16MIM][A] where A = Br, Cl, BF4, PF6, and TFO, generally decreased with increasing anion radius, except for A = PF6, due to strong hydrogen bonds for the sake of an F atom. The values of the critical temperatures (Tm, Tg, and Td) generally show a strong variation with the number of carbon atom or alkyl chain length (the number of n in [CnMIM][A] for A = BF4, NTf2, and PF6). The variation of Tm corresponding to n shows non-monotonous variations. This characteristic is the result of the combination of interaction potentials in the crystalline and liquid phases. The variation of Tg corresponding to n shows even–odd alternation, presumably due to the competition between the electrostatic and van der Waals forces. Many types of ILs have a relatively high Td value, enabling them to remain in the liquid state above 400 °C, they have excellent catalytic activity and dynamic properties. The variation of Td with n appears different to that of Tm. Furthermore, the variation of ΔHm with n seems to follow that of Tm. This behaviour is in accordance with the thermodynamic relation between ΔHm, Tm, and the entropy of the system. The values of λ varied weakly with the alkyl chain length, and strongly depend on the type of anion.

Synergistic inhibition behavior between rhodamine blue and cationic gemini surfactant on mild steel corrosion in 1 M HCl medium

This paper describes corrosion resistance action of Rhodamine blue (RhB) dye in the presence of gemini surfactant (GS) namely, 1,2-ethanediyl-bis(dimethyldecylammonium bromide), (referred to as 10-2-10, where 10 and 2 is the count of carbon atoms in alkyl chain and the spacer part, respectively) for mild steel (MS) in 1 M HCl medium. A combination of experimental and theoretical studies such as mass loss, potentiodynamic polarization method, electrochemical impedance spectroscopy, Ultraviolet-visible (UV-Vis) analysis, Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and molecular dynamic (MD) simulations study were used to investigate the inhibiting features of investigated compounds. Individual RhB and 10-2-10 GS showed low to moderate inhibition efficiency, however, inhibition efficacy of RhB was substantially increased at all studied concentrations when it was synergized with a minimum concentration of 10-2-10 GS (1 × 10−6 M). RhB (1 × 10−3 M) and 10-2-10 (1 × 10−6 M) mixed system offered the highest resistance to acid corrosion (97.5%) at 30°C. MD simulation method evidenced the binding of the studied system onto the MS surface.

Spin-resolved transport properties of atomic carbon chain between sawtooth zigzag-edge graphene nanoribbons electrodes

ABSTRACT We investigate the magnetic transport properties for a molecular device model constructed by a carbon atomic chain embedding in two hydrogen-passivated graphene nanoribbons (GNRs) electrodes with sawtooth zigzag edges. The spin-dependent transport simulation is carried out by the first-principles approach based on the density functional theory combing with nonequilibrium Green's function formalism. It is found that the dual spin-filtering effect with the perfect efficiency up to 100, high-performance dual-spin diode effect with the rectification ratio reaches about and obvious negative differential resistance behaviour with a peak-to-valley ratio near are numerically observed in such proposed molecular device. Particularly, a giant magnetoresistance ratio approaching is also observed, which is two orders magnitude higher than the value of a zigzag-edge GNR. These findings suggest that our proposed device has multifunction with highly effective spin-filter, spin-diode, spin-valve performance.

The effect of the n-alkane evenness on structural phase transitions

The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of odd tricosane C23H48 and even tetracosane C24H50 was studied by FTIR spectroscopy. The initial nuclei location of the new phase was revealed. The process of crystal structure rearrangement is initiated in the interlayers between neighboring lamellar for odd tricosane, while the nanonuclei in even tetracosane arise in the crystalline lamellas cores. Thus, the influence of the number evenness of carbon atoms in the n-alkanes chains on the first-order structural phase transition has been proved.

Influence of calophyllum inophyllum and Jojoba oil methyl ester blended with n-pentanol additive upon overall performance, combustion and emission characteristics of a TDI engine operated in natural aspirated mode

The present manuscript briefly elaborates the performance, combustion and emission behaviour of a turbocharged direct injection diesel engine operated in dual mode where calophyllum inophyllum and Jojoba oil methyl ester are the injected fuel while in second case the above said test fuel blends were mixed homogeneously with n-pentanol that acts as an additive during the experimentation. The main objective of using n-pentanol is its five straight chain carbon atoms that has better possibility of homogeneous blending with biodiesel blends due to its high cetane number, stability and density in contrast to other alcohol based additives helping in improving engine performance and diminished exhaust emissions. During the experimentation, engine parameters like compression ratio (17.5:1), injection timing (21°bTDC), injector opening pressure (220 bar), speed (1500 rpm) were kept constant. Results concluded CIME20–P20 blend to be reliable and potential alternative fuel to partially replace conventional diesel fuel. Considering performance and emission characteristics calophyllum inophyllum oil methyl ester and pentanol blend (CIME20–P20) depicts a higher brake specific fuel consumption of 3.41% while lower exhaust gas temperature and brake thermal efficiency of 13.46% and 1.18% in contrast to diesel fuel. Moving on to emission analysis, carbon dioxide, hydrocarbon, oxides of nitrogen and smoke opacity for CIME20–P20 were 57.02%, 59.37%, 17.39% and 41.53% lower than conventional diesel fuel. Hence, coming to the overall summary, CIME20–P20 depicts better performance and diminished exhaust emission thereby making it more potential to substitute the conventional fuel without any engine alteration for better environmental sustainability and energy security.

A fresh-bias photoresponse of graphene field-effect transistor: An electrical tunable fast dipole moment generation

A unique extra photoresponse of graphene field-effect transistor to the first laser pulse after a switch of back-gate voltage (VBG) is reported and explored here. It is referred as fresh-bias photoresponse (FBPR). FBPR suggests a unique prompt charge transfer process triggered by laser illumination with the help of the VBG and the transferred charge holds as far as the VBG holds unchanged. The responsible charge transfer process is proposed between ester oxygen and carbonyl carbon atoms in the ester side chains of poly(methyl methacrylate) (PMMA) molecule. The proposed mechanism explains perfectly all of the features of FBPR. The charge transfer process generates an inter-molecular dipole moment of PMMA. Such dipole moment generation is much fast than that introduced by a photo-triggered isomerization reaction of photochromic molecule, which have been used in graphene based photodetectors. This mechanism is further confirmed by the test result of a control device with mechanically exfoliated graphene channel and a control device fabricated on hexagonal boron nitride substrate. The mechanism behind FBPR may provide a new way of developing phototransistors, photodetectors or photoelectronic memory devices in the future.

Structural and optical properties of pillared Eu3+-containing layered double hydroxides intercalated by 2- to 12-carbon aliphatic dicarboxylates

While the versatile composition of layered double hydroxides (LDHs) allows the introduction of almost any polyvalent cation in their structure, the exchangeable negatively charged ions intercalated between the plates increase their vast range of functionalities. Here we report on the preparation and optical properties of pillared Eu3+-substituted ZnAl LDHs intercalated by aliphatic dicarboxylates: ‒OOC‒(CH2)n–2‒COO‒. The basal distance in these materials is dependent on the size and packing of the intercalated anions. By varying the number (n) of carbon atoms in the aliphatic chain from 2 to 12, the interlayer gallery of these ZnAlEu LDHs is considerably expanded from 0.9 to 2.1 nm. In the interlayer gallery, the aliphatic dicarboxylates form a monolayer, with the aliphatic chain inclined by an angle α ≈ 63° with the hydroxide layers. The carbon atom in the COO– group is 0.43 nm far from the metal plane, showing that these carboxylates are not grafted in the brucite-like layers. These LDHs are thermally stable up to around 150 °C, after which dehydroxylation of the hydroxide layers is observed. The Judd-Ofelt intensity parameters were obtained and compared to the Eu3+-containing complexes with the same ligand series indicating a more symmetrical and less polarizable chemical environment around the rare earth ion.

Structure of tetra-kis-(μ-deca-noato-κ2 O:O')bis-[(4-methyl-pyridine-κN)copper(II)], a dimeric copper(II) complex.

The 4-methyl-pyridine (4-Mepy) based dimeric copper(II) carboxyl-ate complex [Cu2(C10H19O2)4(C6H7N)2] or [Cu2(μ-O2CC9H19)4(4-Mepy)2] crystallizes with triclinic (P ) symmetry. The two CuII ions exhibit a distorted square-pyramidal environment and are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6472 (8) Å] via four bridging carboxyl-ate ligands arranged in the syn-syn coordination mode. The apical positions around the paddle-wheel copper centers are occupied by the N atoms of the 4-methyl-pyridine ligands. The structure exhibits disorder of the terminal alkyl carbon atoms in the deca-noate chains.

Langmuir-Blodgett Films of Chiral Perfluorinated Gelators: Effects of Chirality and Chain Length on Two-Dimensional Behavior

Abstract Surface pressure versus molecular area (π-A) curves were measured on pure water as a subphase for a series of N,N′-diperfluoroalkanoyl-1,2(R,R)-diaminocyclohexanes. A molecule is denoted as RR-CFn, where n is the number of carbon atoms in a perfluoroalkanoyl chain (or n − 2 = the number of difluoromethylene units). The chain length was varied for n = 4, 5, 6, 8, 9, and 10. The results for n = 7 were reported previously. The effects of chain length and optical purity on film formation were investigated. The surface morphology of a film deposited onto a hydrophilic glass plate was observed using an atomic force microscope (AFM). For n = 4, 5, and 6, the floating films were already multilayered before compression and the deposited films were composed of rectangular or rod-like aggregates. For n = 7, 8, 9, and 10, monolayered films were formed and underwent structural transformation upon compression. From the AFM images, the films deposited after the transformation were composed of fiber-like aggregates. For a racemic mixture, no monolayer film was formed, and the film transfer was impossible irrespective of the chain length. p-Polarized infrared multiple angle incidence resolution spectrometry (pMAIRS) measurements were carried out on a film of RR-CF8 deposited onto a silicon wafer to determine the orientation of the composite molecules. The results were compared with the monolayer behavior reported for a compound having a single perfluoroalkyl chain. The relation to their gelation behavior is also discussed.

A Track-Based Molecular Synthesizer that Builds a Single-Sequence Oligomer through Iterative Carbon-Carbon Bond Formation

Summary We report an artificial molecular machine that moves along a track, iteratively joining building blocks to form an oligomer of single sequence with a continuous backbone of carbon-carbon bonds. The rotaxane features a macrocycle bearing an aldehyde-terminated chain and an axle containing different phosphonium ylides separated by rigid spacers. Each ylide is large enough to block the passage of the macrocycle, trapping the ring between the stopper at the terminus of original threading and the next ylide along the track. Once a building block is reachable, it is removed from the track through a Wittig reaction that adds it to the terminus of the growing chain. Operation on a four-barrier tetra(phosphonium salt) track produces a tetra(diphenylpropane) of single sequence linked through alkene bonds. The prototype extends the principle for molecular machines that build polymers by moving along tracks to the synthesis of sequence-encoded chains with continuous carbon backbones.

Controlled single-spin transport in thermally driven molecular devices containing graphene electrodes modulated by quantum resonance

Resonance effects play an important role in the transport properties of low-dimensional systems. Here, we investigate the thermally driven spin-transport properties of ruthenium-terpyridine molecular devices, where the molecule is linked to graphene electrodes by the carbon atomic chains from two sides. The results show that an odd-even oscillating behavior of the transmission spectra and a perfect spin-filtering effect at the Fermi level are observed in the ruthenium-terpyridine molecular devices. Furthermore, the negative differential thermoelectric resistance more easily appears in the long even-numbered carbon atomic chains, and the sign of the thermally driven single-spin current can be tuned via the temperature. Such a behavior is attributed to the competition between the Breit-Wigner and Fano resonances in the vicinity of the Fermi level for the contributions of the thermally driven current. In brief, here we present an alternative to control the thermally driven single-spin current in molecular devices via quantum effect.

Graphene-based monoatomic chain spintronics: contact-derived half-metallicity, sp2 vs sp

Because of the remarkable semi-metallicity and edge states, graphene-based nanoelectronics has become an intense arena in low-dimensional atomic device science and technology. Nowadays, various single atomic chains have been successfully fabricated, which can serve as multi-functional interconnects to bridge atomic devices. Using first principles approach, the spintronic applications of graphene-based carbon atomic chains and boron nitride atomic chains MTJs (magnetic tunnelling junctions) are systematically investigated in this work. The results show that the half-metallicity is only contact-dominated ( sp and sp 2 contacts), which cannot be switched by gate voltages, strain, the length of atomic chains, or the width of zigzag graphene nanoribbon leads. The intrinsic physics is that the electronic coupling in sp junctions provides partial transmission states for both spin currents, while one spin state is completely blocked by the electronic coupling in sp 2 junctions. Therefore, the sp 2 junctions present half-metallicity and remarkable tunnelling magneto-resistance (10 5 %–10 6 %), demonstrating the potential applications as spin-valve. This work discloses the origin of the contact-dominated effect in graphene-based spintronics which is unknown before. • The half-metallicity of graphene-ACs/BNACs junctions is dominated by contacts. • The sp 2 junctions are fully polarzied and not the case in sp junctions. • The tunnelling magneto-resistance of sp 2 junctions can remarkably reach 10 5 %-10 6 %.

Tight-binding analysis of helical states in carbyne.

Carbyne is a linear allotrope of carbon that is composed of a chain of sp-hybridized carbon atoms. Through appropriate engineering of the chain termination, carbyne can harbor helical states where the π-electron delocalization twists along the axis of the chain. Herein, we present a comprehensive analysis of these helical states at the tight-binding level. We demonstrate that, in general, the molecular orbital coefficients of the helical states trace out an ellipse, in analogy to elliptically polarized light. Helical states can be realized in a model, inspired by the structure of cumulene, which considers a chain terminated by sp2-hybridized atoms oriented at a nontrivial dihedral angle. We provide a complete analytic solution for this model. Additionally, we present a variation of the model that yields perfect helical states that trace out a circle as opposed to an ellipse. Our results provide a deeper understanding of helical states and lay a foundation for more advanced levels of theory.