Interaction of double-stranded polynucleotide poly(A:U) with graphene/graphene oxide

Hybrids formed by DNA/RNA and graphene family nanomaterials are considered as potentially useful multifunctional agents in biosensing and nanomedicine. In this work, we study the noncovalent interaction between double-stranded (ds) RNA, polyadenylic:polyuridylic acids (poly(A:U)) and graphene oxide/graphene (GO/Gr) using UV absorption spectroscopy and molecular dynamics (MD) simulations. RNA melting showed that relatively long ds-RNA is adsorbed onto GO (at an ionic strength of $$\sim 0.1~\hbox {M}$$) at that a large fraction of RNA maintains the duplex structure. It was revealed that this fraction decreases over long time (during a few days), indicating a slow adsorption process of the long polymer. MD simulations showed that the adsorption of duplex (rA)$$_{15}$$: (rU)$$_{15}$$ or (rA)$$_{30}$$: (rU)$$_{30}$$ on graphene starts with the interaction between $$\pi$$-systems of graphene and base pairs located at a duplex tail. In contrast to relatively long duplex (rA)$$_{30}$$: (rU)$$_{30}$$ which keeps parallel arrangement along the graphene surface, the shorter one ((rA)$$_{15}$$: (rU)$$_{15}$$) always adopts a perpendicular orientation relative to graphene even in case of the initial parallel orientation. It was found out that (rA)$$_{30}$$: (rU)$$_{30}$$ forms the stable hybrid with graphene keeping essential fraction of the duplex, while (rA)$$_{15}$$: (rU)$$_{15}$$ demonstrates the duplex unzipping into two single strands with time. The interaction energies between adenine/uracil stacked with graphene as well between nucleotides in water environment were determined

Photophysics of Carbon Nanotubes Interfaced with Organic and Inorganic Materials

Photophysics of Carbon Nanotubes Interfaced with Organic and Inorganic Materials describes physical, optical and spectroscopic properties of the emerging class of nanocomposites formed from carbon nanotubes (CNTs)  interfacing with organic and inorganic materials. The three main chapters detail novel trends in  photophysics related to the interaction of  light with various carbon nanotube composites from relatively simple CNT/small molecule assemblies to complex hybrids such as CNT/Si and CNT/DNA nanostructures.   The latest experimental results are followed up with detailed discussions and scientific and technological perspectives to provide a through coverage of major topics including: ·   Light harvesting, energy conversion, photoinduced charge separation  and transport  in CNT based nanohybrids · CNT/polymer composites exhibiting photoactuation; and ·         Optical  spectroscopy  and structure of CNT/DNA complexes. Including original data and a short review of recent research, Photophysics of Carbon Nanotubes Interfaced with Organic and Inorganic Materials makes this emerging field of photophysics and its applications available to academics and professionals working with carbon nanotube composites in fundamental and applied field

Photophysics of Carbon Nanotubes Interfaced with Organic and Inorganic Materials

VIII, 163 p. 58 illus.online resource

Achieving high mid-IR bolometric responsivity for anisotropic composite materials from carbon nanotubes and polymers

An anisotropic carbon nanotube (CNT)-polymer composite for bolometric applications in the mid-IR spectral range (2.5-20 μm) is studied. Composite alignment in conjunction with non-uniform distribution of CNTs in the polymer matrix allows for a significant enhancement of the temperature coefficient of resistance (0.82% K -1) with respect to uniform composite (0.24% K -1). As a result a responsivity of ≈ 500 V W -1 is reached, which is the highest for CNT-based bolometers reported to date. Such remarkable optical and thermal characteristics are explained in terms of fluctuation tunneling theory taking into account the composite anisotropy and the gradient of the CNT concentration. Flatness of the photoresponse in the broad spectral mid-IR range and enhanced responsivity provide a great potential for the use of such novel composite for applications in IR spectroscopy and thermal imaging. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Noncovalent Interaction of Single-Walled Carbon Nanotubes with 1-Pyrenebutanoic Acid Succinimide Ester and Glucoseoxidase

Peculiarities of the interface interactions of 1-pyrenebutanoic acid <i>N</i>-hydroxysuccinimide ester (PSE) with single-walled carbon nanotubes (SWCNTs) and enzyme glucoseoxidase (GOX) have been studied with the resonance Raman spectroscopy and theoretical calculations employing the DFT method and the molecular dynamics (MD) simulation. The interaction of a nanotube with PSE leads to a downshift of the band assigned in the Raman spectrum to the tangential mode of the hybrid with respect to the position of this mode in the spectrum of the pristine SWCNT. The MD simulation demonstrates that the direct interaction between SWCNT and GOX is very strong. This interaction can be expected to change the structure of the enzyme and to significantly affect its activity. The MD simulation also shows that only one PSE molecule used as a linker between SWCNT and GOX is enough to keep GOX near the nanotube surface in the water surrounding and to prevent strong interaction between SWCNT and GOX. However, to stabilize this nanobiohybrid in water at least two PSE linkers are needed. The molecular structure of PSE is determined using the density functional theory approach (DFT/B3LYP/6-31++G(d,p). The geometries and the relative stabilities of all possible PSE conformers are characterized in the calculations. High structural flexibility of the PSE molecule is demonstrated. Calculations (at the M05-2X level of theory) have also been performed on the structures and the interaction energies of complexes formed by various SWCNTs with PSE and pyrene. Pyrene interacts strongly with the surface of carbon nanotubes with different chiralities, but the interaction with zigzag nanotubes is stronger than with armchair ones of the same diameter. Increasing the diameter of the SWCNTs leads to a higher adsorption energy, reaching the maximum value for graphene (−20.8 kcal/mol)

Binding of Polycitydylic Acid to Graphene Oxide: Spectroscopic Study and Computer Modeling

Hybridization of nucleic acids with graphene nanomaterials is of great interest due to its potential application in genosensing and nanomedicine. In this work we study the interaction between polyribocytidylic acid (poly­(rC)) and graphene oxide (GO). The study involves comparing the UV absorption spectra of the free polymer and the polymer bonded to graphene oxide and analyzing the vibrational structure of the systems and their components using FTIR spectroscopy. Spectral shifts of the electronic and vibrational bands of the poly­(rC) and changes of their thermostability due to the adsorption on GO are observed. Molecular dynamics simulation of the adsorption process of the r­(C)₁₀ and r­(C)₃₀ oligomers on graphene demonstrates their disordering due to the π–π stacking of cytosines on graphene and shows that the longer oligomer adsorbs slower. The binding energies of a single cytosine stacked with graphene in water and in vacuum were determined. The calculated IR lines of the stacked cytosine with graphene are red-shifted by up to 20 cm^–1 compared to free cytosine. A strong decrease of the intensities of the cytosine vibrations in the 1800–1400 cm^–1 range resulting from the interaction with graphene is revealed in the spectra. When cytosine is adsorbed to graphene oxide, their complex is additionally stabilized by H-bonding. It leads to an increase of the red shifting of the cytosine lines

Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization

Noncovalent interaction of methylene blue dye cation (MB⁺) with single walled carbon nanotubes (CNT) is characterized by molecular dynamics (MD) simulation, quantum chemical calculations, and laser desorption/ionization (LDI) mass spectrometry. The MD simulation of the (MB⁺)_<i>n</i>–CNT (<i>n</i> = 1–10) complexes in water demonstrates that the MB⁺ cations are adsorbed on the nanotube surface in the monomeric form. MD reveals both parallel and perpendicular orientations of the MB⁺ tricyclic plane in relation to the long axis of CNT when placed in the water environment. The interaction energy between the components of the complex in the perpendicular conformation, as determined by quantum chemical calculations at the DFT/M05-2X/6-31++G­(d,p) level of theory, explains why the bending of the MB⁺ cation at the sulfur atom weakens the π-system of bonds and allows for the perpendicular orientation to occur. It is also found that the adsorbed MB⁺ induces positive electrostatic potential around the adjacent semicylindrical segment of the nanotube. The mainly monomolecular adsorption of the MB⁺ cations at the CNT surface leads to the absence in the LDI mass spectra of (MB⁺)_<i>n</i>–CNT of features corresponding to products of the reduction of MB⁺ commonly observed in the LDI mass spectra of crystalline dyes

Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization

Noncovalent interaction of methylene blue dye cation (MB⁺) with single walled carbon nanotubes (CNT) is characterized by molecular dynamics (MD) simulation, quantum chemical calculations, and laser desorption/ionization (LDI) mass spectrometry. The MD simulation of the (MB⁺)_<i>n</i>–CNT (<i>n</i> = 1–10) complexes in water demonstrates that the MB⁺ cations are adsorbed on the nanotube surface in the monomeric form. MD reveals both parallel and perpendicular orientations of the MB⁺ tricyclic plane in relation to the long axis of CNT when placed in the water environment. The interaction energy between the components of the complex in the perpendicular conformation, as determined by quantum chemical calculations at the DFT/M05-2X/6-31++G­(d,p) level of theory, explains why the bending of the MB⁺ cation at the sulfur atom weakens the π-system of bonds and allows for the perpendicular orientation to occur. It is also found that the adsorbed MB⁺ induces positive electrostatic potential around the adjacent semicylindrical segment of the nanotube. The mainly monomolecular adsorption of the MB⁺ cations at the CNT surface leads to the absence in the LDI mass spectra of (MB⁺)_<i>n</i>–CNT of features corresponding to products of the reduction of MB⁺ commonly observed in the LDI mass spectra of crystalline dyes