We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density functional theory framework, with additional calculations utilizing Hartree-Fock plus second-order Møller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G > T ≈ C ≈ A > U, with the equilibrium configuration being very similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step towards a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally. PACS numbers: 68.43.-h, 81.07.De, 82.37.RsDNA-coated carbon nanotubes represent a hybrid system which unites the biological regime and the nanomaterials world. They possess features which make them attractive for a broad range of applications, e.g., as an efficient method to separate carbon nanotubes (CNTs) according to their electronic properties [1, 2, 3], as highly specific nanosensors, or as an in vivo optical detector for ions. Potential applications of single-stranded DNA (ss-DNA) covered CNTs range from electron sensing of various odors [4], to probing conformational changes in DNA triggered by shifts in the surrounding ionic concentration [5], and detection of hybridization between complementary strands of DNA [6,7]. The interaction of DNA with CNT is not limited to the outer surface of the tube; it has also been experimentally demonstrated that ssDNA can be inserted into a CNT [8], further enhancing the potential applications of this nano-bio system.The details of the interaction of DNA with CNTs have not yet been fully understood, though it is generally assumed to be mediated by the π-electron networks of the base parts of DNA and the graphene-like surface of CNTs. One would like to obtain a better understanding of the binding mechanism, and the relative strength of base-CNT binding as it is indicated experimentally from sequence-dependent interactions of DNA with CNTs [3,4]. In this Letter, we present the results of our first-principles study of the interaction of nucleobases with a graphene sheet as a significant step towards a deeper understanding of the interaction of ssDNA with * Corresponding authors. CNTs.Previous theoretical studies focused on the adsorption of the nucleobase adenine on graphite [9]. In the present study, we have considered all five nucleobases of DNA and RNA, namely the two purine bases adenine (A) and guanine (G), and the three pyrimidine bases cytosine (C), thymine (T), and uracil (U). Our specific interest is to assess the subtl...

No abstract

We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a (5,0) metallic CNT possessing one of the smallest diameters possible. Compared to CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths, and the calculated binding energies follow the hierarchy G > A > T > C > U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) on their interactions with carbon nanotubes of varying diameters.

Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite while the effect on the axial properties is shown to be insignificant.

We investigate the adsorption of the nucleic acid bases-adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U)-on the outer wall of a high curvature semiconducting single-walled boron nitride nanotube (BNNT) by first-principles density functional theory calculations. The calculated binding energy shows the order: G > A approximately C approximately T approximately U, implying that the interaction strength of the high curvature BNNT with the nucleobases, G being an exception, is nearly the same. A higher binding energy for the G-BNNT conjugate appears to result from hybridization of the molecular orbitals of G and the BNNT. A smaller energy gap predicted for the G-BNNT conjugate relative to that of the pristine BNNT may be useful in the application of this class of biofunctional materials to the design of next-generation sensing devices.

The influence of monomer functionality on the mechanical properties of epoxies is studied using molecular dynamics (MD) with the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. Comparison between the network structures of distinct epoxies is further advanced by the monomeric degree index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli. Therefore, ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 255–264

No abstract

The structure, bonding, vibrational, and electronic properties of small clusters of gallium oxide, Ga m O n (m, n ) 1, 2) are studied here with a focus on the changes induced by the addition or removal of an electron from the neutral species. It is found that the addition of an electron introduces relatively larger structural changes than the removal of an electron from the neutral cluster. The values of ionization potential and electron affinity of these clusters are calculated, for the first time, in this study. Analysis of the atomic charges and electronic properties predicts a kind of instability in Ga 2 O -. In Ga 2 O 2 , the linear Ga-O-Ga-O isomer forms the ground state of the neutral cluster. The cationic structure also prefers the linear configuration, since the ionized electron comes out of an antibonding molecular orbitals of the neutral Ga 2 O 2 . The anionic Ga 2 O 2 , on the other hand, prefers the rhombus structure as a ground state since LUMO of the neutral Ga 2 O 2 consists of a Ga-O bonding orbital.