Group Of Carbon Atoms Research Articles

Characterization and experimental evaluation of cow dung biochar + dolomite for heavy metal immobilization in solid waste from silica sand purification

The synergy of biochar and dolomite for handling heavy metals (Cd and Ba) in solid waste was evaluated by physically mixing cow dung biochar (CDB), prepared via pyrolysis method, and agricultural dolomite. The morphology of biochar and dolomite was fine with uneven grains and pores. The materials contained metal oxides such as MgO, CaO, Fe2O3, SiO2, K2O, and Al2O3, which play an important role in enhancing the adsorption process because of their high porosity for absorbing heavy metals. The Fourier-transform infrared spectroscopy spectrum of biochar contained carbon atom groups such as aromatics, ethers, ketones, and alcohols. By contrast, amine elements (NH2) in dolomite played a role in immobilizing heavy metals with a complexation process between the ligand and the central atom (Cd and Ba).

Visualizing NMR‐shielding effect in fullerene‐ZnPc aggregates: Characteristic patterns of ZnP‐based hosts and encapsulation nature from DFT calculations

AbstractThe formation of supramolecular aggregates incorporating C60 fullerenes can be followed and characterized by nuclear magnetic resonance (NMR) measurements. Here, we unravel the particular patterns provided by zinc‐porphyrin (ZnP)‐bridged dimers, where the aromatic character of each ZnP unit leads to an enhanced shielding region for the closest fullerene atoms, denoting a slight shielding effect for the equatorial atoms. The nature of the stabilization is discussed and compared to a single ZnPC60 aggregate and a ZnP‐dimer (ZnP2C60) model, with a significant contribution from noncovalent ππ interactions, allowing us to address the role of bridging chains. The experimental 13C‐NMR spectrum of C60 in a bridged ZnP dimer shows a single peak owing to the constant tumbling inside the host, which averages the different groups of carbon atoms. The calculations in a static scenario reveal information concerning the local chemical environment underlying the observed shift in relation to isolated C60. We expect that the current approach can be useful to rationalize and predict the origin of the NMR shift upon the formation of host‐guest aggregates involving small and large host species.

Toxicity studies of 1020 Long Multiwalled Carbon Nanotubes (L-MWNT-1020) administered by inhalation to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice.

Multiwalled carbon nanotubes (MWCNTs) are highly ordered hexagonal lattices of carbon atoms arranged into cylinders by hydrogen bonding, dipolar forces, hydrophilic or hydrophobic interactions, gravity, and other forces. MWCNTs are synthesized by applying energy to a carbon source, which produces individual or groups of carbon atoms that reassemble into tubes. One of the primary uses of MWCNTs is in nanotube-reinforced polymer composite materials that take advantage of their low-density and high load-bearing capacity. Nanoscale materials were nominated by the Rice University Center for Biological and Environmental Nanotechnology to the National Toxicology Program for toxicologic testing. Because long-term inhalation toxicity and carcinogenicity studies were being conducted on a relatively short, rigid MWCNT, a representative long and thin MWCNT was selected for these studies. Following an evaluation of 24 different long, thin MWCNTs, the 1020 Long Multiwalled Carbon Nanotube (L-MWNT-1020) (Sun Innovations, Fremont, CA) was selected for study based on availability, high purity (97%), and the low amount of residual nickel catalyst (0.52% by weight). The average L-MWNT-1020 nanotube length was 2,600 nm and the average width was 15.3 nm. Because nickel was shown to be tightly bound to L-MWNT-1020, tissue nickel content was measured to determine lung burden. (Abstract Abridged).

Three-dimensional model of nonsteroidal estrogen receptor ligand binding/electron topological method.

Three-dimensional quantitative structure-activity relationship (3D-QSAR) models have been obtained using the electron topological method (ETM) for estrogen (estrone, CAS 53-16-7) receptor (ER) affinities. This method was used to identify regions of the enzyme and inhibitors where steric and electrostatic effects correlate strongly with biological activity. Thirty compounds belong to a series of diethylstilbestrol (CAS 56-53-1, DES) and indenestrol (CAS 24643-94-5) analogues whose affinities for ER have been, theoretically, investigated. After energy minimizations and molecular dynamics calculations were performed to find the ground state conformer for each molecule, quantum chemical properties of each molecule were defined and in ETM their matrices were compared with those of the reference molecule. It is shown that the molecular fragments responsible for this affinity possess fixed electronic and geometric characteristics associated with a distinct arrangement and steric accessibility of an oxygen atom and a group of carbon atoms. Several parameters were modified in order to analyze their influence onto the correlation between binding affinities. The highest correlation coefficient (R2 = 0.930, SE = 0.403) was obtained with the structure of the active fragment and the orientation of aliphatic and phenolic substituents.

Valence electron structure analysis of diamond crystal growth from Fe–C system

Based on the empirical electron theory of solid and molecules (EET) the valence electron structures (VESs) of diamond, graphite, Fe 3C and γ-Fe crystal were constructed, and the relative electron density differences (REDDs) of the diamond growth interfaces were calculated. It was found that the REDDs of graphite/diamond interfaces were all great, while three among those of Fe 3C/diamond interfaces were little enough that the electron densities were continuous at the first order of approximation, which means that the carbon atom groups are easier to decompose from Fe 3C than from graphite and to transform into diamond structure. Moreover, two of the REDDs of γ-Fe/Fe 3C interfaces were continuous. Accordingly, it can be reasonably suggested that the carbon source for diamond crystal growth may come from the decomposition of Fe 3C instead of graphite, γ-Fe plays a role of catalysis to promote the decomposition of Fe 3C, and the diamond transformation should be finished on the diamond/film interface.

The Microstructures and Catalysis of Metallic Films Covering Diamond Single Crystals Synthesized from Fe-Ni-C System

The metallic films covering diamond play a very important role in the course of diamond nucleation and growth from Fe-Ni-C system at high-temperature and high-pressure (HTHP). The microstructures and surface morphologies of the metallic films are investigated by field-emission scanning electron microscope (FESEM) in this paper. It is shown that there are large numbers of small particles and a series of serrations on the inner surface of the films. It is calculated that the metallic film is mainly composed of (Fe, Ni) 3C, (Fe, Ni)2 3C6, but no diamond structure. The results by energy dispersive spectrometer (EDS) analysis are in good agreement with these by transmission electron microscopy (TEM). It can be concluded that the carbon atom groups coming from the decomposition of Fe-C compound rich in carbon in the film are deposited on the diamond surface directly and diamonds grow in the model of sandwich.

Study of the binding affinity for corticosteroid-binding globulin (CBG) using the electron topological method (ETM) as three-dimensional quantitative structure–activity relationship (3D QSAR)

The Electron Topological Method, called ETM, is a descriptor for predicting the biological activities of molecules based on three-dimensional quantitative structure–activity relations (3D QSAR). ETM uses a modified electron topological state index to substitute for electronic properties and a topological distance for the relative distance in the molecule. It is shown that the molecular fragments responsible for this activity possess fixed electronic and geometric characteristics associated with a distinct arrangement and the steric accessibility of an oxygen atom and a group of carbon atoms. After that, it is essential to employ a linear regression analysis technique to derive a 3D QSAR model relating the biological activities to the ETM. The ETM is used to study the 3D QSAR of the corticosteroid-binding globulin (CBG) binding affinity to 31 steroids, and resulting models have a comparable to current 3D methods such as CoMFA. Though the ETM is a descriptor based on 3D topological information obtained by quantum chemical derived descriptors, give the best answer for both the similarity analysis and the statistical fitting.

Microstructures of metallic film and diamond growth from Fe-Ni-C system

The microstructures of metallic film surrounding diamond have been systemically studied using the transmission electron microscopy (TEM) and the atom force microscopy (AFM). The film can be divided into three layers (inner layer near diamond, external layer near graphite and middle layer). The graphite cannot be directly transformed into diamond in the film at HTHP; there exists a parallel relationship between (−111) of γ-(Fe,Ni) and (110) of Fe3C in the inner layer; the sawtooth-like step morphology found by AFM on the film is similar to that of corresponding diamond surface. A new model for diamond growth at HPHT is proposed from the parallel relationship and sawtooth-like step morphology. It is believed that Fe3C may be a transitional phase in the course of diamond growth, γ-(Fe,Ni) in the inner layer can absorb carbon atom groups with lamella structure from Fe3C, and then the carbon groups stack on growing diamond.

Electron spin resonance spectra: geometrical and electronic structure of endohedral fullerenes

, M = Sc, Y, La) are discussed. The first 13C hyperfine structure has been analyzed in detail and at least seven electronically different groups of carbon atoms could be assigned by simulations of the ESR spectra. The strong similarity of the 13C satellite structure suggests the preference of one cage isomer for the scandium group C82 endohedrals. The geometric structure and the electronic structure of all nine fullerene cage isomers of La@C82 were studied by approximate density-functional-based theoretical calculations. A C3v isomer was found as the most stable one. The manifold of 13C hyperfine coupling constants could be interpreted on the basis of the calculated spin density distributions.

Investigation of the relationship between the inhibitory activity of glycolic acid oxidase (GAO) and its chemical structure: electron-topological approach

Rules for the occurrence of the inhibitory activity of glycolic acid oxidase are formulated and discussed in terms of the socalled electron-topological approach. It is shown that the molecular fragment responsible for this kind of activity possesses fixed electronic and geometrical characteristics caused by a definite spatial arrangement of an oxygen atom and a group of carbon atoms. A series of 85 compounds including 36 active and 49 inactive compounds was studied.

Bond structure and electron states of charged C 60

In the alkali-metal doped C60, the charge transfer induces the distortion of the bond structure and forms the self-trapping electronic bound states. Our theory manifests: 1, the charge transfer reduces the symmetry of C60 from Ih to D5d. 2, Both the bond distortion and the self-trapping states possess layer structures and are localized in the equatorial area. 3, The carbon atoms in charged C60 are divided into eight layers with an inversion center, then there exist four nonequivalent groups of carbon atoms. It makes the NMR line split into a fine structure with strength ratio 1: 1: 2: 2. 4, The charged C60 has two self-trapping bound states, one is 0.06 eV above HOMO with odd parity and the other is 0.05 eV below LUMO with even parity.

Laminar structure of bond distortion and electronic states in charged C60

For doped C 60, the charge transfer distorts the bond structure of C 60 and forms some self-trapping electronic states. The present theory shows that the charged C 60 possesses following remarkable features: 1). Both the bond distortion and the self-trapping states have laminar structure and are localized in the equatorial area. 2). The symmetry is reduced from I h of the pristine C 60 to D 5 d of the charged C 60. 3). The carbon atoms in charged C 60 are divided into eight layers with an inversion center, and there appear four groups of carbon atoms. The atoms in different groups are nonequivalent, then the spectral line in the NMR gets a fine structure consisting of four sub-lines with the strength ratio 1:1:2:2. 4). The charged C 60 has two self-trapping electronic states, one is 0.06eV above HOMO with odd parity, another is 0.05eV below the LUMO with even parity.

The quantitative analysis of solution- and CPMAS-C-13 NMR spectra of humic material

The conditions for obtaining quantitative high resolution C-13 NMR spectra of humic substances in solution and in the solid state are evaluated by determining the relevant relaxation times of the various groups of carbon atoms. Solution spectra at 75 MHz of fulvic and humic acids extracted by standard procedures from 9 German soils were obtained under quantitative conditions in 0.05 M NaOD solution. These are compared to solid state spectra obtained in the cross polarization magic angle spinning (CPMAS) mode at 25 and 75 MHz. In addition to CPMAS spectra of the complete soils and the extracted soils were obtained at the same frequencies. The integration of the spectra obtained for the extracted material shows that the distribution of signal intensity in the various regions of chemical shift is identical for the three types of spectra within experimental error. A different series of measurements comprising various soils with an unusually high content of aromatic carbons showed, however, that for these substances the concentration of aromatic carbon is always found to be too low in the solid state spectra. Comparison of native whole soil solid state spectra with the spectra of the extracts and the solid residues of the extraction procedure casts considerable doubt upon the ability of the standard aqueous sodium hydroxide method to separate defined fractions of humic material.