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retrieving aristotle in an age of crisis：（检索亚里士多德的时代危机）
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When Performance Lost Control Making Rock History …：当性能失去控制，使岩石的历史….pdf13页
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When Performance Lost Control Making Rock History …：当性能失去控制，使岩石的历史…
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Liminalities: A Journal of Performance Studies Vol. 9, No. 4, November 2013 When Performance Lost Control: Making Rock
History out of Ian Curtis and Joy Division
J. Rubén Valdés Miyares 1.
“Who is right, who can tell, and who gives a damn right now”1
This is a case study of the continuities between living, performing and writing. When
Ian Curtis hanged himself at the age of 23, tortured by epilepsy, medication, fear and
having just started a promising career as singer and songwriter for the band
intriguing
Will Tear Us Apart”, and about to embark on their first American tour, he was stag-
ing his ultimate performance. The act turned him into a cult figure, as it gave an eerie
resonance to the increasingly gloomy lyrics he had written for his band. Music journalists began to write about Joy Division in a more vivid, dramatic way.
People who had never seen the band perform live, or even heard of them while Curtis
was alive, became fans. Joy Division was hailed in their native Manchester, England,
as youthful symbols of the postmodern city, and in the rest of the world as founders
of the gothic rock scene. They were subsequently the subject of biographies, biopics
documentaries
particularly
personality,
webpage devoted to the band
lists about twenty Joy Division
tribute bands performing their songs, while Youtube enables fans and critics to watch
the band perform at several gigs on very low quality footage, and much more visually
appealing clips of actor Sam Riley performing as Ian Curtis in the biopic about him, Control
2007 . At present the hyperreal Curtis of
Control seems to be on the verge of
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帝国主义世界没有真正的英雄_《黑暗的心脏》和《吉姆爷》主题分析.pdf53页
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正在加载中，请稍后...CitationsSee all >82 ReferencesSee all >4 Figures7.56 · University of Duisburg-Essen+ 230.08 · Fraunhofer Institute for Ceramic Technologies and Systems IKTS47.05 · Technische Universit?t DresdenShow
more authorsAbstractHere we present a hybrid approach to functionalize multi-walled carbon nanotubes in aqueous solution, exploring a non-covalent binding strategy. We focus on formation of hybrid complexes consisting of carbon nanotubes decorated by single stranded DNA, non-covalently attached using surfactants as intermediate layers. Unlike single walled carbon nanotubes, revealing easy side wall wrapping of DNA, we observe that wrapping of nucleic acids around multi-walled carbon nanotubes is diameter dependent.Discover the world's research12+ million members100+ million publications700k+ research projects
Physical Chemistry Chemical Physics c3cp51844bBio-functionalizationQ1 Q2of multi-walled carbonnanotubesAnindya Majumder, Maryam Khazaee, Joerg Opitz,Eckhard Beyer, Larysa Baraban* andGianaurelio CunibertiWe focus on functionalizationQ3of multi-walled carbonnanotubes in aqueous solution and investigate formationof hybrid complexes representing carbon nanotubes,decorated by noncovalently attached single strandedDNA. Possibility to use surfactants as intermediate layersis also discussed.Please check this proof carefully. Our staff will not read it in detail after you have returned it.Translation errors between word-processor files and typesetting systems can occur so the whole proof needs to be read.Please pay particular attention to: tabulated
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Queries for the attention of the authorsJournal: PCCPPaper: c3cp51844bTitle: Bio-functionalization of multi-walledcarbonnanotubesEditor’s queries are marked on your proof like thisQ1, Q2, etc. and for your convenience line numbers areindicated like this 5, 10, 15, ...Please ensure that all queries are answered wh en returning your proof corrections so that publication of yourarticle is not delayed.QueryreferenceQuery RemarksQ1 For your information: You can cite this article before youreceive notification of the page numbers by using thefollowing format: (authors), Phys. Chem. Chem. Phys.,(year), DOI: 10.844b.Q2 Please carefully check the spelling of all author names.This is important for the correct indexing and futurecitation of your article. No late corrections can be made.Q3 Please check that the GA text fits within the allocatedspace indicated on the front page of the proof. If theentry does not fit between the two horizontal lines, thenplease trim the text and/or the title.Q4 Ref. 4: Can this reference be updated?Q5 Ref. 28 and 39: Please provide the journal title and page(or article) number(s).Q6 Ref. 42: Please provide the page (or article) number(s).
Bio-functionalization Q1 Q2of multi-walled carbonnanotubes+Anindya Majumder,zaMaryam Khazaee,zaJoerg Opitz,abEckhard Beyer,cLarysa Baraban*aand Gianaurelio CunibertiadHere we present a hybrid approach to functionalize multi-walled carbon nanotubes in aqueoussolution, exploring a non-covalent binding strategy. We focus on formation of hybrid complexesconsisting of carbon nanotubes decorated by single stranded DNA, non-covalently attached usingsurfactants as intermediate layers. Unlike single walled carbon nanotubes, revealing easy side wallwrapping of DNA, we observe that wrapping of nucleic acids around multi-walled carbon nanotubes isdiameter dependent.IntroductionCarbon nanotubes (CNTs) as multi-functional nano materialshave attracted much attention from both academics and indus-try due to their unique electronic,1optical2and mechanicalproperties.3These unique properties make them ideal candi-dates for various applications ranging from bio-inspired tonanoelectronics and sensorics to biomedical applications, e.g.drug delivery.4–11One of the main challenges for integration ofCNTs into the biological environment is their uniform disper-sion in physiologically relevant liquid medium, i.e. water basedbuffers and stable biochemical functionalization. It is wellknown that CNTs exhibit poor solubility both in aqueous andnon-aqueous solutions due to their hydrophobicity.12Van derWaals (VDW) interaction between tubes in aqueous solutionresults in their aggregation into micrometer-sized bundles.Significant efforts have been devoted to find appropriatemethodologies to solubilize pristine nanotubes in differentsolutions to prepare individually dispersed tubes.13–16Functio-nalization of nanotubes and their stable dispersions can beachieved using surface active agents covalently17,18or non-covalently19,20attached to CNT surfaces. In contrast to thecovalent methodology that leads to disruption of the surfacechanges and the mechanical and electrical performance of thenanotubes, the non-covalent one represents a versatile, quickand straight forward technique for dispersion of CNTs.21Mostly single-walled carbon nanotubes (SWCNTs) have beeninvestigated for high end application in electronics and biol-ogy, while the multi-walled carbon nanotubes (MWCNTs) havebeen largely limited to bulk composites.22,23Whereas a lot ofwork was dedicated to investigate non-covalent bio-modifica-tion of SWCNTs, e.g. by nucleic acids,19,24,25bio-functionaliza-tion studies of MWCNTs have been limited, which restrictedthe range of their potential applications. Remarkably, MWCNTscould represent an alternative solution for biomedical andnano electronic application since they are cheap, highly pure,less toxic26and have higher electrical conductivity.27Non-covalent functionalization of MWCNTs can be realizedusing various surfactants or flexible polymers such as singlestranded DNA (ssDNA), which get adsorbed on the sidewalls ofCNTs without disturbing the p-system of the walls.28Here wefocus on developing a hybrid non-covalent strategy for functio-nalization of MWCNTs, which combines the use of both surfaceactive agents and DNA strands assembled as a sandwich at thesurface of nanotubes. Our approach is conceptually summar-ized in Fig. 1. Once dispersed (Fig. 1a) in solution thesecomponents interact with each other forming small stable nanoassemblies (Fig. 1b). MWCNTs are functionalized by adsorptionof surfactants (Fig. 1c) and ssDNA (Fig. 1d) on their outer walls.Simultaneous interaction of MWCNTs with surfactants andssDNA molecules leads to formation of hybrid structures(Fig. 1e) with biochemical functionality to the CNT complexes.While the strategies presented in Fig. 1c and d were reportedpreviously,19,20a hybrid approach to functionalize MWCNTs by15101520253035404550551510152025303540455055Cite this: DOI: 10.844baMax Bergmann Center of Biomaterials, Dresden University of Technology,Budapester Strasse 27, D-01069 Dresden, Germany.E-mail: larysa.baraban@nano.tu-dresden.debFraunhofer Institute IZFP Dresden, 01109 Dresden, GermanycChair for Laser and Surface Technology, Dresden University of Technology,George-Ba¨hr-str. 3c, D-01069 Dresden, GermanydDivision of IT Convergence Engineering, POSTECH, Pohang, Korea+ Electronic supplementary information (ESI) available. See DOI: 10.1039/c3cp51844b? These authors share equal contribution in this work.Received 30th April 2013,Accepted 26th June 2013DOI: 10.844bwww.rsc.org/pccpThis journal is?cthe Owner Societies 2013 Phys. Chem. Chem. Phys ., 2013, 00,1–7 | 1PCCPPAPER
immobilizing ssDNA on the top of the surfactant layer (Fig. 1d)represents a new technological step29,30and still requiresdeeper analysis and optimization.In our investigations of MWCNT hybrid complexes consist-ing of surfactants and nucleic acids, we make an emphasis onthe following aspects: (i) investigation and optimization of non-covalent dispersion of MWCNTs by ionic surfactants, (ii) func-tionalization of dispersed MWCNTs with nucleic acid. Firstly,in order to determine the parameters governing the de-bund-ling and solubilization process, a systematic study for solubilityof MWNTs in a variety of surfactants was performed. Further,we investigate the interactions of ssDNA fragments with theMWCNT surface with different parameters using microscopytechniques. We report that ssDNA has poor wrapping abilityaround MWCNTs due to large diameter of the tubes31,32andsurplus inter-wall VDW forces31inhibiting the wrapping ofssDNA around them.Materials and methodsWe employed MWCNTs in powder form purchased from Nano-cylTM (Belgium) with an average diameter and an averagelength of 9.5 nm and 1.5 mm respectively (for more details onstatistical analysis see ESI+). Optimized preparation of CNTsolution was achieved by comparison of the dispersive effects ofvarious ionic surfactants (Sigma Aldrich) including sodiumdodecyl sulfate (SDS), sodium dodecylbenzenesulfonate(SDDBS), sodium cholate (SC), dodecyltrimethylammoniumbromide (DTAB) and decyltrimethylammonium bromide(CTAB) (for more details see section ESI+). For this purposedeionized water with 1% wt/wt of the surfactant was used todisperse MWCNTs (1 mg ml?1). Dispersion of CNTs in theaqueous solution was carried out using a horn sonicator for10 min at 8% amplitude. The sonication process was followedby a centrifugation step for 45 min at 15 000 rpm to separate thelarger aggregates from the dispersion. After centrifugation, theupper 80% of the supernatant was decanted for laterinvestigations.For the biofunctionalization experiments long chainedM13mp18 ssDNA (7249 bp) with 110 nM (New England Bio-Labs) was dispersed in tris-acetate-EDTA (TAE) buffer with pHadjusted to 8. To facilitate dispersion of MWCNTs and attachthe ssDNA on its side walls, the CTAB surfactant (1% wt/wt) wasadded to TAE buffer. Suspension of 1 mg ml?1of MWCNTs inCTAB/TAE buffer was prepared and 50 ml of M13mp18 wasadded to the solution. Thus, DNA chains were attached to theCTAB covered MWCNT surface. Supernatants of these solutionscontaining hybrid complexes of MWCNT–CTAB–DNA werecharacterized using UV-vis spectrometry, transmission electronmicroscopy (TEM) and atomic force microscopy (AFM) toinvestigate the dispersion quality of MWCNTs and characterof their interactions with nucleic acids.Adsorption spectra of MWCNTs dispersed in aqueoussolution by means of different surfactants were measured usinga UV-vis spectrometer (Cary 50 BioVarian Inc.) in the wave-length range between 200 and 1100 nm. The absorption spectraof these samples were measured by subtracting the absorbancebackground values of 1 wt% surfactants. High resolution TEMmeasurements were carried out uaing a JEOL 2010F system.Samples for TEM investigations were prepared by dropping 10ml MWCNT suspension onto a copper grid with a carbon filmand dried in air before examination. In order to visualizeMWCNTs dispersed and functionalized by DNA, AFM investiga-tions (Nanoscope IIIa of Digital Instruments) were carried outin tapping mode.Results and discussionOptimization of sonication parameters was done using SDS bytuning the effects of duration and amplitude. Table 1 sum-marizes the parameters for sonication with the final length anddiameter of the tubes after centrifugation. Two samples with15101520253035404550551510152025303540455055Fig. 1 (a) Schematic representation of MWCNTs, ssDNA, surfactant moleculesand their interaction with solution, (b) interaction of MWCNTs with cationicsurfactant molecules, (c) probable interaction of MWCNTs with ssDNA and (d)simultaneous interaction of all three components which form hybrid structurethrough attachment of ssDNA to the hydrophilic head of the cationic surfactant,while the surfactant’s hydrophobic tail is adsorbed on the MWCNT side walls.Table 1 Comparison of length and diameter of dispersed MWCNTs underdifferent sonication conditionsFig. 2SonicationLength (nm) Diameter (nm)Amplitude (%) Time (min)a 22 20 100–800 2.5–5b 8 20 300–1500 7–9c 8 10 500–2000 9–112 | Phys. Chem. Chem. Phys., 2013, 00, 1–7 This journal is?cthe Owner Societies 2013Paper PCCP
the same sonication time of 20 min were prepared withdifferent amplitudes of 22% and 8% followed by centrifugationat 15 000 rpm for 45 min. Fig. 2a and b displays AFM images ofsamples investigated in Table 1 showing the resultingMWCNTs obtained after processing steps described above.With higher sonication amplitude, the tubes turned out to beshorter with an average diameter of approximately 3 nm, whilefor lower amplitude (Fig. 2b) longer tubes with larger diameterwere obtained. The reduced diameter is due to the exfoliationof the outer shells of the nanotube. Finally, Fig. 2c shows thenanotubes with the resulting average length greater than 1 mmand an average diameter of 10 nm, which were obtained undergentle sonication conditions (8% amplitude and duration of10 min). These parameters were found to be optimal and wereused in the following experiments, since they do not lead to themassive destruction of the nanotubes during the preparationphase.Adsorption spectra of MWCNTs dispersed in aqueoussolution are measured using a UV-vis spectrometer (Fig. 3a).Direct comparison of MWCNTs solubility is not feasible, asbundles of MWCNTs are not active in the wavelength regionbetween 200–1100 nm and only individual CNTs exhibit char-acteristic bands.13In order to compare efficiency of the disper-sion by different surfactants, the absorbance values at 500 nmwavelength are plotted in Fig. 3b showing that SDDBS revealsthe best ability to solubilize nanotubes. At the same time, DTABwas found to have the lowest dispersibility of MWCNTs inaqueous solution compared to other surfactants used for thisexperiment. This trend is found to be reproducible upon multi-ple repetition of the UV-vis spectra measurements. According tothe previous reports, such property was ascribed to theirchemical structures.20,33As depicted in Fig. 1d, ssDNA chains are also used todisperse CNTs non-covalently in aqueous solution.30This canbe attributed to the VDW interactions between ssDNA basesand CNT sidewalls. However the hybrid approach developedhere represents a sandwich of the cationic CTAB film combinedwith ssDNA, which enhances the dispersion of MWCNTs onone hand and facilitates the DNA binding to the CNT surface onthe other hand. In this case positively charged head groups ofthe surfactant and negatively charged phosphate groups of DNAattach together by electrostatic interactions. The first step ofthe functionalization scheme, i.e. the coating of MWCNT by theCTAB surfactant was verified by TEM measurements (Fig. 4a).One can see that the surface of MWCNTs is covered by theCTAB layer, as indicated by the red arrow, which is approxi-mately 2 nm thick. The yellow arrow shows the walls constitut-ing MWCNTs. Once ssDNA was added to CTAB–MWCNTsolution the nucleic acid molecules start to interact with thinfilms of the surfactants and modify the dispersion of thenanotubes. To investigate the effect of the DNA addition,optical absorbance of the functionalized MWCNTs was mea-sured using UV-vis spectroscopy. Fig. 4b summarizes the mea-surements of the adsorption spectra of the hybrid DNA–CTAB–MWCNT system. Obviously, adsorption values for the dispersedMWCNTs with DNA–CTAB are higher than that of only CTAB.This confirms the facts of the interaction of DNA with thesurfactant layer and enhanced dispersibility of MWCNTs in thepresence of DNA molecules. The insets show the images takento compare suspensions of these samples. By visual compar-ison of two samples, one can see that suspension of DNA–CTAB–MWCNTs appears to be much darker than solution ofCTAB–MWCNTs.15101520253035404550551510152025303540455055Fig. 2 AFM images of SDS–MWCNTs after sonication with different amplitudeand sonication time (a) 22%–20 min, (b) 8%–20 min, (c) 8%–10 min.Fig. 3 (a) UV-Vis spectra of CNTs in different surfactants and (b) calculatednanotube dispersibility of these dispersed MWCNTs by SDDBS, SC, CTAB, SDS andDTAB at 500 nm wavelength.This journal is?cthe Owner Societies 2013 Phys. Chem. Chem. Phys ., 2013, 00,1–7 | 3PCCP Paper
Furthermore, binding of DNA molecules to the dispersedMWCNTs with CTAB was visualized using AFM. Fig. 5a and cexhibit the AFM images of CTAB–MWCNT and DNA–CTAB–MWCNT complexes on the silicon surface respectively. In orderto understand the interactions between ssDNA and surfactantmodified CNTs, we analysed the height profiles along the tubesin the AFM images as shown in Fig. 5b and d respectively. Thestraight black line and the red dashed lines in each heightprofile image correspond to the mean value of the nanotubeheight and standard deviations calculated for the CTAB–MWCNT complexes. These values for the CTAB–MWCNT arefound to be 8.7 nm and 1.7 nm, respectively, which is inagreement with the data provided by the nanotube supplier.On the other hand, the analysis of DNA–CTAB–MWCNT com-plexes (Fig. 5c and d) reveals the increased average height andstandard deviations up to 10.4 nm and 2.8 nm respectively. Theindicated characteristic spikes in this height profile imageconfirm the existence of small fragments of DNA moleculeson CTAB–CNT hybrid structure which is in agreement with thecomplementary AFM image (Fig. 5c). In contrast to known inthe literature ‘‘wrapping’’ of the DNA molecules aroundSWCNTs, we did not observe any reproducible wrapping ofssDNA around MWCNTs during our experiments.According to the reported results12,19,29,30,34and our ownexperimental observations, the dispersion of MWCNTs usingssDNA is not as effective as for SWCNTs. The probable reasonfor this could be related to the intrinsic difference in thephysical conditions during wrapping. The Hamaker constantthat defines the pair potential between nanoparticles andnanotubes is experimentally shown to be c.a. 6 ? 10?21J(3.8 eV), which is associated with the Van der Waals forces.35It has been reported that interaction between MWCNTs has amore significant dependence on VDW constants as comparedto SWCNTs.36For instance, nanotube and nanoparticle inter-actions controlled by VDW forces have pronounced effects ontheir geometrical shape and sizes.31Both MWCNTs and thessDNA carry negative surface charges associated with ?COOHgroups due to partial oxidation for CNT edges from purificationsteps and those that comprise the sugar phosphate backbone ofssDNA. Therefore the ssDNA should overcome a potentialenergy barrier to get adsorbed on the tube surface. Typicallydozens of atoms make the circumference of each nanotubeshell, and the –COOH groups, which are predominantly presenton nanotube ends, have a spatial density that is dependent onthe number of nanotube shells. This makes the quantitativedifference in terms of energy advantage for the interactionsbetween ssDNA with SWCNTs and MWCNTs. Furthermore,since CNTs are spatially extended, one-dimensional, electricallyconducting structures with plasmonic electrons, VDW interac-tions with other nanoscale and molecular species are likely to15101520253035404550551510152025303540455055Fig. 4 (a) TEM micrograph of the surfactant-coated MWCNTs (CTAB–MWCNTs).(b) UV-vis spectra of MWCNTs dispersed in aqueous solutions using CTAB (redcurve), and DNA–CTAB (black curve) (inset images indicating these curves showthe supernatant of the respective curves).Fig. 5 AFM images (a) CTAB—MWCNT, (b) height profile of CTAB—MWCNT, (c)ssDNA–CTAB–MWCNT and (d) height profile of CTAB–ssDNA–MWCNT (peaksmarked in red show the attachments of ssDNA to CTAB). The height profilerepresented by white dotted lines in the images depicts the plots for standarddeviation represented by red dotted lines.4 | Phys. Chem. Chem. Phys., 2013, 00, 1–7 This journal is?cthe Owner Societies 2013Paper PCCP
be more long-ranged (B1/r3) than those typically observed, forexample, between microscopic colloidal species (B1/r6).31Finally, it has been shown that the binding energy of themolecular species to the nanotubes is increased with tubediameter, but is reduced with an increase in the number ofinner shells.37These arguments are important for understand-ing the interactions of the ssDNA with MWCNTS covered bypositively charged surfactants (see Fig. 5 and 6). The presenceof the cationic surfactant decreases the potential barrier forssDNA binding to the nanotube surface however the multiwallstructure of the tubes reduces the binding of the molecule.Fig. 6a shows the AFM image of dispersed MWCNTs usingssDNA in TAE buffer where a certain periodicity of the DNAwrapping around the tube was still observed. Surprisingly, themeasured average diameter of the nanotube (Fig. 6b) was foundto be around 1 nm (see green frame and black baseline inFig. 6b), which is nearly ten times smaller than the averagediameter of the nanotubes as mentioned before. The red arrowsin Fig. 6b indicate the peaks above the CNT line, depicting theheight profile of the ssDNA wrapped around the nanotube.From the measured spacing of the peak profile, we find aperiodicity in the range of 40–80 nm, which can be consideredas the pitch of the ssDNA wrapped helically. It has beenreported that depending on the tube diameter and the numberof shells, the interaction within nanotubes bound to substratesor into bundles in solution can lead to substantial axial andradial deformations of adsorbed nanotubes destroying theiridealized shape.37,38Thus an experimentally found nanotube with a wrappedssDNA molecule could be an example of the disrupted MWCNTstructure. Since the number of shells of this MWCNT wasdiminished as compared to the initial one, the ability of ssDNAto bind has increased.37In order to understand the consequence of sonication letus consider the carbon bonds in the nanotube structure.The difference in bond lengths depends on the chirality andradius of the nanotube.39Unlike in graphite where one bondlength determines its structure, in the case of nanotubes,folding of the graphene sheet introduces two different direc-tions i.e. the radial direction and the length direction, whichlikely dictate through two different bond lengths. The stackingsequence of the layers is generally of ABAB type with aninterlayer {002} spacing of typically 0.334 nm, which resultsin a circumference difference of 2.1 nm between two successivetubes. The p-orbitals provide the weak VDW bonds between theplanes. The increase in total surface area due to the nano scaledimensions enhances the attractive forces between them tre-mendously. The nanotubes assemble in bundles, which con-tain hundreds of closely packed CNTs tightly bound by a VDWattraction energy of 500 eV mm?1of the tube–tube contact.40At high intensity of ultrasonication the acoustic cavitationprocess appearing in the liquid environment results in agileformation, growth and collapse of bubbles. Upon bubbleimplosion, temperatures and pressures of up to 15 000 K and1000 bar can be created.41,42The physical conditions in such anenvironment are aggressive enough for exfoliation and peelingof MWCNT graphene layers, which are initiated at the externallayers. As a result, tubes become thinner with time undergoinga layer by layer unwrapping process.34,43This leads us toconclude that the ssDNA wrapped tube in this case is a singlewalled tube that could have metamorphosed from MWCNTsdue to breaking of bonds, exfoliation and probably sliding ofthe large nanotube shells.The representation in Fig 6c shows the possible mechan-isms of metamorphosis of MWCNTs into SWCNTs duringsonication. The yellow arrows depict the inter wall VDW forcespresent within MWCNT walls, while the blue arrows showpossible exfoliation of the outer walls. It has been reportedthat the nanotube layers seem to be quite independent, soMWNTs would not only get shorter, but also thinner with time15101520253035404550551510152025303540455055Fig. 6 (a) AFM image of MWCNTs dispersed with M13mp18 DNA in buffer (yellow frame indicates the region of the plot for the height profile along the tube). Greenand yellow arrows point the height level of CNT and DNA, respectively. (b) Height profile of the nanotube wrapped by ssDNA: green frame indicates the height profilelevel of carbon
black baseline represents a level of the average height of the tube B1
red arrows demonstrate the regions, associated with wrappedDNA. (c) Representation of the inner tube VDW forces (yellow arrows) in MWCNTs, exfoliation of outer walls (blue arrows) and sliding motion of the inner wall fromthe outer walls along the tube axis (white arrow).This journal is?cthe Owner Societies 2013 Phys. Chem. Chem. Phys ., 2013, 00,1–7 | 5PCCP Paper
going through a layer by layer unwrapping process.34,43Thesonication energy provided during sonication is enough toinitiate the breaking of bonds easily overcoming VDW energywithin the tube walls, leading to the exfoliation of the outerwalls. The white arrow parallel to the inner most tube axisdepicts the probable possibility of the nanotube sliding outfrom the outer shells, which could be energetically morefavorable. It has been reported that VDW interaction can causean extruded core of MWNTs to retract into the outer shells44andweak load transfer was observed between the inner and outerlayers of MWCNTs with an interfacial shear strength of less than1 MPa arising from weak VDW.45As reported by Takahashi et al.32aMWCNTwithadiameterassmallas4nmhasmorecapabilityfor wrapping DNA around it, than a larger diameter tube. Thepoor wrapping ability of the MWCNTs could be attributed to theinner wall surplus VDW interaction present in the case ofMWCNTs. However, single walled tubes or tubes with lowerdiameter formed due to the propo sed mechanisms are readilywrapped by ssDNA as observed in our investigations. Thus weconfirm experimentally the statement proposed by Takahashi thatwrapping of DNA around MWCNTs is diameter dependent.ConclusionsWe investigated the optimum dispersion parameters ofMWCNTs using different surfactants. Non-covalent functiona-lization of MWCNTs was successfully investigated. Further weshow possibility to make hybrid structure functionalization byattaching ssDNA backbone to the positively charged head groupof CTAB by ionic interaction. Finally, we ascertained themetamorphosis of MWCNTs during sonication, its bindingeffects with ssDNA and comparison of this system with theSWCNT case. Shorter fragments of ssDNA can be attached toCTAB modified MWCNT surfaces and metamorphosed CNTswith narrow diameter are able to facilitate more complexinteractions of CNTs with ssDNA, i.e. so-called ‘‘wrapping’’.These phenomena were attributed to the diameter dependenceand surplus energy during sonication. We believe that moreinsights into functionalization of MWCNTs by ssDNA mole-cules can help boost the utilization of the MWCNTs for realbiomedical applications, which could be relevant in the field ofnanomedicine for novel methods of drug and gene delivery.AcknowledgementsThis work was funded by ‘‘European Center for EmergingMaterials and Processes Dresden’’ (ECEMP), European Union(ERDF) and the Free State of Saxony via the ESF project‘‘InnovaSens’’. We gratefully acknowledge support from theGerman Excellence Initiative via the Cluster of Excellence EXC1056 ‘‘Center for Advancing Electronics Dresden’’ (cfAED). Thisresearch was supported by World Class University programfunded by the Ministry of Education, Science and Technologythrough the National Research Foundation of Korea (R31-10100). We acknowledge Markus Poetschke, Dr Imad Ibrahimand Dr Viktor Bezugly for fruitful discussions.Notes and references1 M. Yu, O. Lourie, M. Dyer, K. Moloni, T. Kelly and R. Ruoff,Science, 2000, 287, 637–640.2 X. Liu, J. Si, B. Chang, G. Xu, Q. Yang, Z. Pan, S. Xie,P. Ye, J. Fan and M. Wan, Appl. Phys. Lett., 1999, 74,164–166.3 E. Wong, P. Sheehan and C. Lieber, Science, 1997, 277,.4 R. Mendes, A. Bachmatiuk, B. Buechner, G. Cuniberti andM. Ru¨mmeli, J. MaterQ4. Chem. B, 2013.5 Z. Guo, P. Sadler and S. Tsang, Adv. Mater., 1999, 10,701–703.6 Z. Liu, S. Tabakman, K. Welsher and H. Dai, Nano Res.,2009, 2, 85–120.7 M. Foldvari and M. Bagonluri, Nanomed.: Nanotechnol., Biol.Med., 2008, 4, 173–182.8 K. Kostarelos, A. Bianco and M. Prato, Nat. Nanotechnol.,2009, 4, 627–633.9 K. Balasubramanian and M. Burghard, Anal. 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ABSTRACT: The formation of liquid crystalline phases or isotropic clusters is observed in carbon nanotubes systems experiencing repulsive and attractive interactions, respectively. ssDNA-stabilized nanotubes act as strongly repulsive charged rods, showing nematic phases in (pseudo)-binary and ternary systems, in the presence of a nonadsorbing polymer. Switching between purely repulsive and attractive regime has not been investigated yet. For this reason, dispersions of ssDNA-stabilized nanotubes were added with an oppositely charged additive (i.e., protein or surfactant), and the resulting systems were investigated. In both phase diagrams a strong associative behavior was observed. At additive charge excess, a redispersion of the complex was obtained. The phenomenon was substantial in the case of surfactant system, where a charge inversion was also observed. A fine-tuning of attractive and repulsive interactions promoted aggregation and redispersion of carbon nanotube complexes. The introduction of weak attractive forces may promote the formation a cluster phase of ssDNA-stabilized nanotubes, with possible application as “multicompartimental” delivery systems. Full-text · Article · Apr 2014 Article · Jan 2015 ABSTRACT: Processing carbon nanotubes (CNT) into functional materials requires usage of multi-component systems. Additives such as ionic surfactants, complex macromolecules (i.e. DNA, proteins) or colloidal nanoparticles are used at the purpose. Unfortunately, the high intrinsic non-ideality of these systems makes predictions and simulations on their behavior challenging. That is why experimental investigations on the overall colloidal behavior are fundamental in developing CNT-based technologies. To that purpose, we have recently started a systematic characterization of (pseudo)-ternary systems containing carbon nanotubes. In a previous study, we have characterized the reentrant behavior of single-stranded DNA (ssDNA)/CNT in presence of an oppositely-charged surfactant. The ratio between ssDNA/nanotubes and surfactant defines the overall associative behavior. Irreversible aggregation is found close to t while negatively- or positively-charged surfactant-ssDNA/nanotubes complexes appear at DNA or surfactant (re-dispersion) excess, respectively. Here, we present a detailed investigation on the effects of chain length and ionic strength on the nanotubes associative behavior by considering an approach involving different and complementary experimental techniques. The associative behavior is related to the micellization ability of surfactant. Interestingly, no re-dispersion is found for short chains with n&14. The phase behavior is analyzed in comparison with the one of polyelectrolyte-surfactant-water system. Full-text · Article · Jan 2016 ABSTRACT: this work focuses on the design of an engineered thermoplastic polymer containing pyrrole units in the main chain and hydroxyl pendant groups (A-PPy-OH), which help in achieving nanocomposites containing well-distributed, exfoliated and undamaged MWCNTs. The thermal annealing at 100 [degree]C of the pristine nanocomposite promotes the redistribution of the nanotubes in terms of a percolative network, thus converting the insulating material in a conducting soft matrix (60 [small mu ] [capital Omega].m). This network remains unaltered after cooling to r.t. and to successive heating cycles up to 100 [degree]C thanks to the effective stabilization of MWCNTs provided by the functional polymer matrix. Notably, the resistivity-temperature profile is very reproducible and with a negative temperature coefficient of -0.002 K-1, which suggests the potential application of the composite as a temperature sensor. Overall, the industrial scale by which A-PPy-OH can be produced offers a straightforward alternative forArticle · Sep 2016 +1 more author...ABSTRACT: Antimicrobial activity of surfactant-modified multi-walled carbon nanotubes (MWCNTs) was investigated by analyzing the growth curves of an Escherichia coli (E. coli) population in ionic and non-ionic surfactant-modified MWCNTs in Luria Bertani (LB) broth. The ionic surfactants (sodium dodecylbenzenesulfonate (SDBS), sodium cholate (SC), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB)) as well as a non-ionic polyvinylpyrrolidone (PVP) were used to test the dispersion and resulting antimicrobial effect of MWCNTs by means of UV–vis spectroscopy and optical density (OD) measurement. Among these surfactants, SDBS and DTAB provided maximum and minimum MWCNT dispersion, respectively. Furthermore, the biocompatibility issues with respect to dispersion capabilities of the ionic and non-ionic surfactants is discussed in detail, as a source of potential misinterpretation of the obtained growth curves of E. coli and thus, their antimicrobial effect. Finally, scanning electron microscopy was used to study the interaction of well-dispersed MWCNTs with the E. coli cells. Full-text · Article · Sep 2016 +1 more author...DataMay 2013ArticleMay 2013 · Nano Research · Impact Factor: 7.01ArticleAugust 2013 · Nanotechnology · Impact Factor: 3.82Lotta R?mhildt+1 more author…ArticleSeptember 2016+2 more authors…Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.This publication is from a journal that may support self archiving.
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