Editing Carbon nanotube (section)

== Variants ==
There is no consensus on some terms describing carbon nanotubes in the scientific literature: both "-wall" and "-walled" are being used in combination with "single", "double", "triple", or "multi", and the letter C is often omitted in the abbreviation, for example, multi-walled carbon nanotube (MWNT). The [[International Standards Organization]] typically uses "single-walled carbon nanotube (SWCNT)" or "multi-walled carbon nanotube (MWCNT)" in its documents.<ref>{{cite web |title=Nanotechnologies — Vocabulary — Part 3: Carbon nano-objects |url=https://www.iso.org/obp/ui/es/#iso:std:iso:ts:80004:-3:ed-2:v1:en |website=www.iso.org |access-date=22 October 2024}}</ref>

=== Multi-walled ===
[[File:Multi-walled Carbon Nanotube.png|thumb|Triple-walled armchair carbon nanotube]]

Multi-walled nanotubes (MWNTs) consist of multiple rolled layers (concentric tubes) of graphene. There are two models that can be used to describe the structures of multi-walled nanotubes. In the ''[[Matryoshka doll|Russian Doll]]'' model, sheets of [[graphite]] are arranged in concentric cylinders, e.g., a (0,8) single-walled nanotube (SWNT) within a larger (0,17) single-walled nanotube. In the ''[[Scroll (parchment)|Parchment]]'' model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.4 Å. The Russian Doll structure is observed more commonly. Its individual shells can be described as SWNTs, which can be metallic or semiconducting.<ref name=Hamada /><ref name=wildoer /> Because of statistical probability and restrictions on the relative diameters of the individual tubes, one of the shells, and thus the whole MWNT, is usually a zero-gap metal.<ref>{{cite journal | vauthors = Das S |title=A review on Carbon nano-tubes – A new era of nanotechnology |journal=International Journal of Emerging Technology and Advanced Engineering |volume=3 |issue=3 |date=March 2013 |pages=774–781 |url=https://ijetae.com/files/Volume3Issue3/IJETAE_0313_132.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ijetae.com/files/Volume3Issue3/IJETAE_0313_132.pdf |archive-date=2022-10-09 |url-status=live |citeseerx=10.1.1.413.7576 }}</ref>

Double-walled carbon nanotubes (DWNTs) form a special class of nanotubes because their [[Morphology (biology)|morphology]] and properties are similar to those of SWNTs but they are more resistant to attacks by chemicals.<ref>{{cite journal | vauthors = Piao Y, Chen CF, Green AA, Kwon H, Hersam MC, Lee CS, Schatz GC, Wang Y |title=Optical and Electrical Properties of Inner Tubes in Outer Wall-Selectively Functionalized Double-Wall Carbon Nanotubes |journal=The Journal of Physical Chemistry Letters |date=7 July 2011 |volume=2 |issue=13 |pages=1577–1582 |doi=10.1021/jz200687u }}</ref> This is especially important when it is necessary to graft chemical functions to the surface of the nanotubes ([[Surface functionalization|functionalization]]) to add properties to the CNT. Covalent functionalization of SWNTs will break some C=C [[double bond]]s, leaving "holes" in the structure on the nanotube and thus modifying both its mechanical and electrical properties. In the case of DWNTs, only the outer wall is modified. DWNT synthesis on the gram-scale by the [[CCVD]] technique was first proposed in 2003<ref>{{cite journal | vauthors = Flahaut E, Bacsa R, Peigney A, Laurent C | title = Gram-scale CCVD synthesis of double-walled carbon nanotubes | journal = Chemical Communications | issue = 12 | pages = 1442–1443 | date = June 2003 | pmid = 12841282 | doi = 10.1039/b301514a | url = https://hal.archives-ouvertes.fr/hal-00926035/file/Flahaut_10551.pdf | url-status = live | s2cid = 30627446 | archive-url = https://ghostarchive.org/archive/20221009/https://hal.archives-ouvertes.fr/hal-00926035/file/Flahaut_10551.pdf | archive-date = 2022-10-09 }}</ref> from the selective reduction of oxide solutions in methane and hydrogen.

The telescopic motion ability of inner shells, allowing them to act as low-friction, low-wear nanobearings and nanosprings, may make them a desirable material in [[nanoelectromechanical systems]] (NEMS) .<ref>{{cite journal | vauthors = Cumings J, Zettl A | title = Low-friction nanoscale linear bearing realized from multiwall carbon nanotubes | journal = Science | volume = 289 | issue = 5479 | pages = 602–604 | date = July 2000 | pmid = 10915618 | doi = 10.1126/science.289.5479.602 | citeseerx = 10.1.1.859.7671 | bibcode = 2000Sci...289..602C }}</ref> The retraction force that occurs to telescopic motion is caused by the [[Lennard-Jones interaction]] between shells, and its value is about 1.5&nbsp;nN.<ref>{{cite journal | vauthors = Zavalniuk V, Marchenko S | year = 2011 | title = Theoretical analysis of telescopic oscillations in multi-walled carbon nanotubes | journal = Low Temperature Physics | volume = 37 | issue = 4 | pages = 337–342 | arxiv = 0903.2461 | doi = 10.1063/1.3592692 | bibcode = 2011LTP....37..337Z | s2cid = 51932307 | url = http://dspace.nbuv.gov.ua/xmlui/bitstream/123456789/118539/1/12-Zavalniuk.pdf | archive-url = https://ghostarchive.org/archive/20221009/http://dspace.nbuv.gov.ua/xmlui/bitstream/123456789/118539/1/12-Zavalniuk.pdf | archive-date = 2022-10-09 | url-status = live }}</ref>

=== Junctions and crosslinking ===

[[File:Nanotube junction.jpg|thumb|Transmission electron microscope image of carbon nanotube junction]] Junctions between two or more nanotubes have been widely discussed theoretically.<ref name=Chernozatonskii>{{cite journal | vauthors = Chernozatonskii LA |year=1992 |title=Carbon nanotube connectors and planar jungle gyms |journal=[[Physics Letters A]] | volume = 172 | issue = 3 | pages = 173–176 | doi=10.1016/0375-9601(92)90978-u| bibcode = 1992PhLA..172..173C}}</ref><ref name= Menon>{{cite journal | vauthors = Menon M, Srivastava D |title=Carbon Nanotube 'T Junctions': Nanoscale Metal-Semiconductor-Metal Contact Devices |journal=Physical Review Letters |date=1 December 1997 |volume=79 |issue=22 |pages=4453–4456 |doi=10.1103/physrevlett.79.4453 |bibcode=1997PhRvL..79.4453M }}</ref> Such junctions are quite frequently observed in samples prepared by [[electric arc|arc discharge]] as well as by [[chemical vapor deposition]]. The electronic properties of such junctions were first considered theoretically by Lambin et al.,<ref name=Lambin>{{cite journal | vauthors = Lambin P | year = 1996| title = Atomic structure and electronic properties of bent carbon nanotubes | journal = [[Synth. Met.]] | volume = 77 | issue = 1–3 | pages = 249–1254 | doi=10.1016/0379-6779(96)80097-x}}</ref> who pointed out that a connection between a metallic tube and a semiconducting one would represent a nanoscale heterojunction. Such a junction could therefore form a component of a nanotube-based electronic circuit. The adjacent image shows a junction between two multiwalled nanotubes.
Junctions between nanotubes and graphene have been considered theoretically<ref name=Ma>{{cite journal | vauthors = Ma KL | year = 2011| title = Electronic transport properties of junctions between carbon nanotubes and graphene nanoribbons| journal = [[European Physical Journal B]] | volume = 83 | issue = 4 |pages=487–492 | doi=10.1140/epjb/e2011-20313-9| bibcode = 2011EPJB...83..487M| s2cid = 119497542 }}</ref> and studied experimentally.<ref name=Harris>{{cite journal | vauthors = Harris PJ, Suarez-Martinez I, Marks NA | title = The structure of junctions between carbon nanotubes and graphene shells | journal = Nanoscale | volume = 8 | issue = 45 | pages = 18849–18854 | date = December 2016 | pmid = 27808332 | doi = 10.1039/c6nr06461b | s2cid = 42241359 | url = http://centaur.reading.ac.uk/67327/1/NANOSCALE%20FOR%20CENTAUR.pdf | url-status = live | archive-url = https://ghostarchive.org/archive/20221009/http://centaur.reading.ac.uk/67327/1/NANOSCALE%20FOR%20CENTAUR.pdf | archive-date = 2022-10-09 }}</ref> Nanotube-graphene junctions form the basis of [[pillared graphene]], in which parallel graphene sheets are separated by short nanotubes.<ref name= Dimitrakakis>{{cite journal | vauthors = Dimitrakakis GK, Tylianakis E, Froudakis GE | title = Pillared graphene: a new 3-D network nanostructure for enhanced hydrogen storage | journal = Nano Letters | volume = 8 | issue = 10 | pages = 3166–3170 | date = October 2008 | pmid = 18800853 | doi = 10.1021/nl801417w | bibcode = 2008NanoL...8.3166D }}</ref> Pillared graphene represents a class of [[#Three-dimensional carbon nanotube architectures|three-dimensional carbon nanotube architectures]].
[[File:3D carbon scaffolds.PNG|thumb|3D carbon scaffolds]]
Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic (>100&nbsp;nm in all three dimensions) all-carbon devices. Lalwani et al. have reported a novel radical-initiated thermal crosslinking method to fabricate macroscopic, free-standing, porous, all-carbon scaffolds using single- and multi-walled carbon nanotubes as building blocks.<ref name="PMID 23436939">{{cite journal | vauthors = Lalwani G, Kwaczala AT, Kanakia S, Patel SC, Judex S, Sitharaman B | title = Fabrication and Characterization of Three-Dimensional Macroscopic All-Carbon Scaffolds | journal = Carbon | volume = 53 | pages = 90–100 | date = March 2013 | pmid = 23436939 | pmc = 3578711 | doi = 10.1016/j.carbon.2012.10.035 }}</ref> These scaffolds possess macro-, micro-, and nano-structured pores, and the porosity can be tailored for specific applications. These 3D all-carbon scaffolds/architectures may be used for the fabrication of the next generation of energy storage, supercapacitors, field emission transistors, high-performance catalysis, photovoltaics, and biomedical devices, implants, and sensors.<ref name="PMID 25788440">{{cite journal | vauthors = Lalwani G, Gopalan A, D'Agati M, Sankaran JS, Judex S, Qin YX, Sitharaman B | title = Porous three-dimensional carbon nanotube scaffolds for tissue engineering | journal = Journal of Biomedical Materials Research. Part A | volume = 103 | issue = 10 | pages = 3212–3225 | date = October 2015 | pmid = 25788440 | pmc = 4552611 | doi = 10.1002/jbm.a.35449 }}</ref><ref name="noyce2">{{cite journal | vauthors = Noyce SG, Vanfleet RR, Craighead HG, Davis RC | title = High surface-area carbon microcantilevers | journal = Nanoscale Advances | volume = 1 | issue = 3 | pages = 1148–1154 | date = March 2019 | pmid = 36133213 | pmc = 9418787 | doi = 10.1039/C8NA00101D | doi-access = free | bibcode = 2019NanoA...1.1148N }}</ref>

=== Other morphologies ===
[[File:NanoBud.JPG|thumb|A stable [[Carbon nanobud|nanobud]] structure]]
[[Carbon nanobud]]s are a newly created material combining two previously discovered allotropes of carbon: carbon nanotubes and [[fullerene]]s. In this new material, fullerene-like "buds" are covalently bonded to the outer sidewalls of the underlying carbon nanotube. This hybrid material has useful properties of both fullerenes and carbon nanotubes. In particular, they have been found to be exceptionally good [[field electron emission|field emitters]].<ref name="Nasibulin">{{cite journal | vauthors = Nasibulin AG, Pikhitsa PV, Jiang H, Brown DP, Krasheninnikov AV, Anisimov AS, Queipo P, Moisala A, Gonzalez D, Lientschnig G, Hassanien A, Shandakov SD, Lolli G, Resasco DE, Choi M, Tománek D, Kauppinen EI | title = A novel hybrid carbon material | journal = Nature Nanotechnology | volume = 2 | issue = 3 | pages = 156–161 | date = March 2007 | pmid = 18654245 | doi = 10.1038/nnano.2007.37 | doi-access = free | bibcode = 2007NatNa...2..156N }}</ref> In [[composite material]]s, the attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite's mechanical properties.

A [[carbon peapod]]<ref>{{cite journal| vauthors = Smith BW, Monthioux M, Luzzi DE |year=1998 |title= Encapsulated C-60 in carbon nanotubes |journal=Nature |volume=396 |issue=6709 |pages=323–324 |bibcode=1998Natur.396R.323S|doi=10.1038/24521 |s2cid=30670931}}</ref><ref>{{cite journal| vauthors = Smith BW, Luzzi DE |year=2000|title=Formation mechanism of fullerene peapods and coaxial tubes: a path to large scale synthesis|journal=Chem. Phys. Lett.|volume=321|issue=1–2|pages=169–174|bibcode=2000CPL...321..169S|doi=10.1016/S0009-2614(00)00307-9 }}</ref> is a novel hybrid carbon material which traps fullerene inside a carbon nanotube. It can possess interesting magnetic properties with heating and irradiation. It can also be applied as an oscillator during theoretical investigations and predictions.<ref>{{cite journal | vauthors = Su H, Goddard WA, Zhao Y |year=2006 |title= Dynamic friction force in a carbon peapod oscillator |journal=Nanotechnology |volume=17 |issue=22 |pages=5691–5695 |arxiv=cond-mat/0611671|bibcode=2006Nanot..17.5691S|doi=10.1088/0957-4484/17/22/026 |s2cid=18165997|url=https://authors.library.caltech.edu/6289/1/SUHnanotech06.pdf |archive-url= https://ghostarchive.org/archive/20221009/https://authors.library.caltech.edu/6289/1/SUHnanotech06.pdf |archive-date=2022-10-09 |url-status=live}}</ref><ref>{{cite journal | vauthors = Wang M, Li CM | title = An oscillator in a carbon peapod controllable by an external electric field: a molecular dynamics study | journal = Nanotechnology | volume = 21 | issue = 3 | page = 035704 | date = January 2010 | pmid = 19966399 | doi = 10.1088/0957-4484/21/3/035704 | s2cid = 12358310 | bibcode = 2010Nanot..21c5704W }}</ref>

In theory, a nanotorus is a carbon nanotube bent into a [[torus]] (doughnut shape). Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than that previously expected for certain specific radii.<ref name="nanotori">{{cite journal | vauthors = Liu L, Guo GY, Jayanthi CS, Wu SY | title = Colossal paramagnetic moments in metallic carbon nanotori | journal = Physical Review Letters | volume = 88 | issue = 21 | page = 217206 | date = May 2002 | pmid = 12059501 | doi = 10.1103/PhysRevLett.88.217206 | bibcode = 2002PhRvL..88u7206L | url = http://ntur.lib.ntu.edu.tw//handle/246246/163841 }}</ref> Properties such as [[magnetic moment]], thermal stability, etc. vary widely depending on the radius of the torus and the radius of the tube.<ref name="nanotori" /><ref>{{cite journal| vauthors = Huhtala M, Kuronen A, Kaski K |year=2002|title=Carbon nanotube structures: Molecular dynamics simulation at realistic limit |url= http://www.princeton.edu/~msammalk/publications/cpc146_02.pdf |journal= [[Computer Physics Communications]] | volume=146|issue=1|pages=30–37 |bibcode=2002CoPhC.146...30H |doi=10.1016/S0010-4655(02)00432-0 |archive-url=https://web.archive.org/web/20080627183309/http://www.princeton.edu/~msammalk/publications/cpc146_02.pdf|archive-date=27 June 2008}}</ref>

[[Graphenated carbon nanotube]]s are a relatively new hybrid that combines [[Graphite|graphitic]] foliates grown along the sidewalls of multiwalled or bamboo-style CNTs. The foliate density can vary as a function of deposition conditions (e.g., temperature and time) with their structure ranging from a few layers of [[graphene]] (< 10) to thicker, more [[graphite]]-like.<ref>{{cite journal| vauthors = Parker CB, Raut AS, Brown B, Stoner BR, Glass JT |title=Three-dimensional arrays of graphenated carbon nanotubes|journal=J. Mater. Res.|year=2012|volume=27|series=7|pages=1046–1053 |doi=10.1557/jmr.2012.43|issue=7|bibcode = 2012JMatR..27.1046P|s2cid=137964473 }}</ref> The fundamental advantage of an integrated [[graphene]]-CNT structure is the high surface area three-dimensional framework of the CNTs coupled with the high edge density of graphene. Depositing a high density of graphene foliates along the length of aligned CNTs can significantly increase the total [[Capacitance|charge capacity]] per unit of nominal area as compared to other carbon nanostructures.<ref>{{cite journal| vauthors = Stoner BR, Glass JT |title=Carbon nanostructures: a morphological classification for charge density optimization|journal=Diamond and Related Materials|year=2012|volume=23|pages=130–134|doi=10.1016/j.diamond.2012.01.034|bibcode = 2012DRM....23..130S}}</ref>

Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures, which normally behave as quasi-metallic conductors of electrons. CSCNTs exhibit semiconducting behavior because of the stacking microstructure of graphene layers.<ref>{{cite journal| vauthors = Liu Q, Ren W, Chen ZG, Yin L, Li F, Cong H, Cheng HM |year=2009|title=Semiconducting properties of cup-stacked carbon nanotubes |url= http://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdf |journal= Carbon |volume=47 |issue=3 |pages=731–736 |doi=10.1016/j.carbon.2008.11.005 |bibcode=2009Carbo..47..731L |archive-url= https://web.archive.org/web/20150109002837/http://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdf |archive-date=2015-01-09}}</ref>