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Descriptors and quantitative structure property relationships (QSPR) were investigated for mechanical property prediction of carbon nanotubes (CNTs). 78 molecular dynamics (MD) simulations were carried out, and 20 descriptors were calculated to build quantitative structure property relationships (QSPRs) for Young's modulus and Poisson's ratio in two separate analyses: vacancy only and vacancy plus methyl functionalization. In the first analysis, C(N2)/C(T) (number of non-sp2 hybridized carbons per the total carbons) and chiral angle were identified as critical descriptors for both Young's modulus and Poisson's ratio. Further analysis and literature findings indicate the effect of chiral angle is negligible at larger CNT radii for both properties. Raman spectroscopy can be used to measure C(N2)/C(T), providing a direct link between experimental and computational results. Poisson's ratio approaches two different limiting values as CNT radii increases: 0.23-0.25 for chiral and armchair CNTs and 0.10 for zigzag CNTs (surface defects3%). In the second analysis, the critical descriptors were C(N2)/C(T), chiral angle, and M(N)/C(T) (number of methyl groups per total carbons). These results imply new types of defects can be represented as a new descriptor in QSPR models. Finally, results are qualified and quantified against experimental data.

The thermal conductivity (TC) of isolated graphene with different concentrations of isotopes (C13) is studied with equilibrium molecular dynamics method at 300K. In the limit of pure C12 or C13 graphene, TC of graphene in zigzag and armchair directions are ~630 W/mK and ~1000W/mK, respectively. We find that the TC of graphene can be maximally reduced by ~80%, in both armchair and zigzag directions, when a random distribution of C12 and C13 is assumed at different doping concentrations. Therefore, our simulation results suggest an effective way to tune the TC of graphene without changing its atomic and electronic structure, thus yielding a promising application for nanoelectronics and thermoelectricity of graphene based nano-device., 8 pages, 4 figures, to be published in Journal of Nanomaterials

Experimental solubilities are reported for anthracene dissolved in seven binary alkane+3-methoxy-1-butanol solvent mixtures at 25°C. The alkane cosolvents studied were hexane, heptane, octane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane and tert-butylcyclohexane (also called (1,1-dimethylcyclohexane). Results of these measurements are used to test two mathematical representations based upon the combined Nearly Ideal Binary Solvent (NIBS)/Redlich-Kister and Modified Wilson equations. For the seven systems studied, both equations were found to provide an accurate mathematical representation of the experimental data, with an overall average absolute deviation between measured and calculated values being 0.6% and 0.9% for the Combined NIBS/Redlich-Kister and Modified Wilson equations, respectively.

Experimental solubilities are reported for pyrene in ten binary alkane+alcohol solvent mixtures containing either 1-butanol or 2-methyl-1-propanol with hexane, heptane, octane, cyclohexane and methylcyclohexane. Results of these measurements, along with published anthracene and pyrene solubility data, are used to test predictive expressions based upon the mobile order theory. For the 59 systems studied, the best predictive equation was found to predict the observed solubility data to within an overall average deviation of about 3% using numerical values of 125 cm 3 mol −1 and 175 cm 3 mol −1 for the anthracene–alcohol and pyrene–alcohol stability constants, respectively. Alcohol self-association constants and binary interaction parameters were obtained by regressing vapor–liquid equilibria (VLE) data for alkane+alcohol mixtures.

Experimental solubilities are reported for anthracene dissolved in seven binary alkane+2-isopropoxyethanol solvent mixtures at 25°C. The alkane ccsolvents studied were hexane, heptane, octane, cyclohexarie, methylcyclohexane, 2,2,4-trimethylpentane and tert-butylcyclohexane (also called (1,1-dimethylethyl)cyclohexane). Results of these measurements are used to test two mathematical representations based upon the combined Nearly Ideal Binary Solvent (NIBS)/Redlich-Kister and Modified Wilson equations. For the seven systems studied, both equations were found to provide an accurate mathematical representation of the experimental data, with an overall average absolute deviation between measured and calculated values being 0.5% and 0.7% for the Combined NIBS/Redlich-Kister and Modified Wilson equations, respectively.

The reactive empirical bond order (REBO) potential developed by Brenner et al. [Phys. Rev. B 42, 9458 (1990); J. Phys. Condens. Matter 14, 783 (2002)] for molecular dynamics (MD) simulations of hydrocarbons, and recently extended to include interactions with oxygen atoms by Ni et al. [J. Phys. Condens. Matter 16, 7261 (2004)], is modified for graphene-oxide (GO). Based on density-functional-theory (DFT) calculations, we optimized the REBO-CHO potential (in which CHO denotes carbon, hydrogen, and oxygen) to improve its ability to calculate the binding energy of an oxygen atom to graphene and the equilibrium C-O bond distances. In this work, the approach toward the optimization is based on modifying the bond order term. The modified REBO-CHO potential is applied to investigate the properties of some GO samples.

Cross links between inner and outer walls of multiwalled carbon nanotubes are believed to increase nanotube modulus and therefore nanotube effectiveness for reinforcing composites. In order to investigate changes in the Young's modulus of individual double-walled nanotubes (DWNTs) as a function of cross-link density and type, molecular-dynamics simulations are employed to evaluate strain coupling and corresponding load transfer from outer to inner walls. Results show that interwall $s{p}^{3}$ bonds and interstitial carbon atoms can increase load transfer between DWNT walls and that interwall $s{p}^{3}$ bonds are most effective. However, the maximum size of the modulus increase is limited to about 25% for the investigated small-diameter, short DWNTs because the defects decrease the stiffnesses of the nanotube walls.

Article on a comparison of analytical methods and a direct emission versus first-derivative fluorometric methods for quinine determination in tonic waters.