View source for Chemistry:Carbon nanothread

{{Nanomat}}
A '''carbon nanothread''' (also called '''diamond nanothread''') is a [[Physics:Orbital hybridisation#sp3|sp<sup>3</sup>-bonded]], one-dimensional carbon crystalline nanomaterial. The tetrahedral sp<sup>3</sup>-bonding of its carbon is similar to that of [[Chemistry:Diamond|diamond]]. Nanothreads are only a few atoms across, more than 20,000 times thinner than a human hair. They consist of a stiff, strong carbon core surrounded by hydrogen atoms. [[Physics:Carbon nanotube|Carbon nanotube]]s, although also one-dimensional nanomaterials, in contrast have [[Physics:Orbital hybridisation#sp2|sp<sup>2</sup>-carbon]] bonding as is found in [[Chemistry:Graphite|graphite]]. The smallest carbon nanothread has a diameter of only 0.2 nanometers, much smaller than the diameter of a single-wall carbon nanotube. <ref>{{cite journal |last1=Huang |first1=Haw-Tyng |last2=Zhu |first2=Li |last3=Ward |first3=Matthew D. |last4=Wang |first4=Tao |last5=Chen |first5=Bo |last6=Chaloux |first6=Brian L. |last7=Wang |first7=Qianqian |last8=Biswas |first8=Arani |last9=Gray |first9=Jennifer L. |last10=Kuei |first10=Brooke |last11=Cody |first11=George D. |last12=Epshteyn |first12=Albert |last13=Crespi |first13=Vincent H. |last14=Badding |first14=John V. |last15=Strobel |first15=Timothy A. |title=Nanoarchitecture through Strained Molecules: Cubane-Derived Scaffolds and the Smallest Carbon Nanothreads |journal=Journal of the American Chemical Society |date=21 January 2020 |volume=142 |issue=42 |pages=17944–17955 |doi=10.1021/jacs.9b12352 |pmid=31961671 |s2cid=210870993 |issn=0002-7863}}</ref>

== Synthesis ==

Nanothreads are synthesized by compressing liquid [[Chemistry:Benzene|benzene]] to an extreme pressure of 20 GPa (around 200,000 times the air pressure at the surface of the [[Astronomy:Earth|Earth]]), and then slowly relieving that pressure.<ref name="tcfitz2014"/> The mechanochemical<ref name=":1" /> synthesis reaction can be considered a form of [[Chemistry:Organic chemistry|organic]] [[Chemistry:Solid-state chemistry|solid state]] chemistry. The benzene chains form extremely thin, tight rings of carbon that are structurally similar to diamonds.<ref>[https://finance.yahoo.com/news/scientists-might-accidentally-solved-hardest-155000475.html Scientists Might Have Accidentally Solved The Hardest Part Of Building Space Elevators], Business Insider, 13 October 2014, Ajai Raj</ref> Researchers at [[Organization:Cornell University|Cornell University]] have traced pathways from benzene to nanothreads, which may involve a series of organic [4+2] [[Chemistry:Cycloaddition|cycloaddition]] reactions along stacks of benzene molecules, followed by further reactions of unsaturated bonds.<ref name=":7">{{Cite journal|last1=Chen|first1=Bo|last2=Hoffmann|first2=Roald |last3=Ashcroft|first3=N. W.|last4=Badding|first4=John|last5=Xu|first5=Enshi|last6=Crespi|first6=Vincent|date=2015-11-18|title=Linearly Polymerized Benzene Arrays As Intermediates, Tracing Pathways to Carbon Nanothreads|journal=Journal of the American Chemical Society|volume=137|issue=45|pages=14373–14386|doi=10.1021/jacs.5b09053|pmid=26488180|issn=0002-7863}}</ref> Recently synthesis of macroscopic [[Earth:Single crystal|single crystal]] arrays of nanothreads hundreds of microns in size has been reported.<ref name=":1">{{Cite journal|last1=Li |first1=Xiang|last2=Baldini|first2=Maria|last3=Wang|first3=Tao|last4=Chen|first4=Bo|last5=Xu|first5=En-shi|last6=Vermilyea |first6=Brian|last7=Crespi |first7=Vincent H.|last8=Hoffmann|first8=Roald|last9=Molaison|first9=Jamie J.|date=2017-11-15 |title=Mechanochemical Synthesis of Carbon Nanothread Single Crystals|journal=Journal of the American Chemical Society |volume=139 |issue=45|pages=16343–16349|doi=10.1021/jacs.7b09311|pmid=29040804|issn=0002-7863}}</ref> The order and lack of grain boundaries in single crystals is often very desirable because it facilitates both applications and characterization. In contrast, [[Physics:Carbon nanotube|carbon nanotube]]s form only thin crystalline ropes. Control of the rate of compression and/or decompression appears to be important to the synthesis of polycrystalline and single crystal nanothreads.<ref name="tcfitz2014" /><ref name=":1" /> Slow compression/decompression may favor low energy reaction pathways.<ref name=":1" /> If the synthesis pressure for nanothreads can be reduced to 5 to 6 GPa, which is the pressure used for [https://minerals.usgs.gov/minerals/pubs/commodity/diamond/mcs-2016-diamo.pdf synthesis of industrial diamond],  production on a large scale of >10<sup>6</sup> kg/yr would be possible. Recent advance on using strained cage-like molecules such as [[Chemistry:Cubane|cubane]] as a precursor has successfully brought down the synthesis pressure to 12 GPa. Expanding the precursor library to non-aromatic, strained molecules offers new avenues to explore scalable production of carbon nanothreads.<ref>{{cite journal |last1=Huang |first1=Haw-Tyng |last2=Zhu |first2=Li |last3=Ward |first3=Matthew D. |last4=Wang |first4=Tao |last5=Chen |first5=Bo |last6=Chaloux |first6=Brian L. |last7=Wang |first7=Qianqian |last8=Biswas |first8=Arani |last9=Gray |first9=Jennifer L. |last10=Kuei |first10=Brooke |last11=Cody |first11=George D. |last12=Epshteyn |first12=Albert |last13=Crespi |first13=Vincent H. |last14=Badding |first14=John V. |last15=Strobel |first15=Timothy A. |title=Nanoarchitecture through Strained Molecules: Cubane-Derived Scaffolds and the Smallest Carbon Nanothreads |journal=Journal of the American Chemical Society |date=21 January 2020 |volume=142 |issue=42 |pages=17944–17955 |doi=10.1021/jacs.9b12352 |pmid=31961671 |s2cid=210870993 |issn=0002-7863}}</ref>  

The formation of nanothread crystals appears to be guided by [[Stress–strain analysis#Uniaxial stress|uniaxial stress]] (mechanical stress in a particular single direction), to which the nanothreads consistently align.<ref name=":1" /> Reaction to form the crystals is not topochemical,<ref>{{Cite journal|last1=Lauher|first1=Joseph W.|last2=Fowler|first2=Frank W.|last3=Goroff|first3=Nancy S.|date=2008-09-16|title=Single-Crystal-to-Single-Crystal Topochemical Polymerizations by Design|journal=Accounts of Chemical Research|volume=41|issue=9|pages=1215–1229|doi=10.1021/ar8001427|issn=0001-4842|pmid=18712885}}</ref> as it involves a major rearrangement from a lower symmetry [[Physics:Monoclinic crystal system|monoclinic]] benzene crystal to a higher symmetry [[Physics:Hexagonal crystal family|hexagonal]] nanothread crystal.  Topochemical reactions generally require commensuration between the periodicities and interatomic distances between reactant and product. The distances between benzene molecules with [[Physics:Van der Waals force|van der Waals]] separations between them must shrink by 40% or more as the short, strong [[Chemistry:Covalent bond|covalent]] carbon-carbon bonds between them form during the nanothread synthesis reaction. Such large changes in geometry usual break up crystal order, but the nanothread reaction instead creates it.  Even [[Earth:Crystallite|polycrystalline]] benzene reacts to form macroscopic single crystal packings of nanothreads hundreds of microns across.<ref name=":1" />  Topochemical solid state reactions such as the formation of single crystal [[Chemistry:Polydiacetylenes|polydiacetylenes]] from diacetylenes usually require a single crystal reactant to form a single crystal product.

The impetus for the formation of a hexagonal crystal appears to be the packing of circular cross section threads.<ref name=":1" />  The details of how it is possible to transform from a monoclinic benzene crystal to a hexagonal nanothread crystal are not yet fully understood. Further development of the theory of the effect of pressure on reactions may help.<ref>{{Cite journal|last1=Chen|first1=Bo|last2=Hoffmann|first2=Roald|last3=Cammi|first3=Roberto|date=2017-09-04|title=The Effect of Pressure on Organic Reactions in Fluids—a New Theoretical Perspective|journal=Angewandte Chemie International Edition|language=en|volume=56|issue=37|pages=11126–11142|doi=10.1002/anie.201705427|pmid=28738450|issn=1521-3773|doi-access=free}}</ref>

Organic synthesis efforts towards polytwistane nanothreads have been reported.<ref>{{Cite journal|last1=Olbrich|first1=Martin|last2=Mayer |first2=Peter|last3=Trauner|first3=Dirk|date=2015-02-20|title=Synthetic Studies toward Polytwistane Hydrocarbon Nanorods|journal=The Journal of Organic Chemistry|volume=80|issue=4|pages=2042–2055|doi=10.1021/jo502618g|pmid=25511971|issn=0022-3263}}</ref> 
[[File:Polytwistane.gif|thumb|left|Rotating polytwistane, a prototypical  nanothread structure.<ref name=":5" /><ref name=":4" /> Black atoms are carbon.  Light grey atoms are hydrogen.]]
[[File:Polytwistane Crystal.png|thumb|Polytwistane crystal viewed down its hexagonal c axis.  Black atoms are carbon and pink atoms are hydrogen.  The length of the threads is going into the page, showing their circular cross section and hexagonal packing that (experimentally) extends over hundreds of microns in crystals. The outline of the hexagonal unit cell is shown in blue.  These crystals exfoliate into bundles of nanothreads.<ref name=":1" />]]

== History ==
In popular culture, diamond threads were first described by Arthur C. Clarke in his sci-fi novel ''[[Unsolved:The Fountains of Paradise|The Fountains of Paradise]]'' set in the 22nd century, written in 1979.

Nanothreads were first investigated theoretically in 2001 by researchers at [[Organization:Pennsylvania State University|Penn State University]]<ref name=":2">{{Cite journal|last=Stojkovic|first=Dragan|date=2001|title=Smallest Nanotube: Breaking the Symmetry of|journal=Physical Review Letters|volume=87|issue=12|pages=125502|doi=10.1103/physrevlett.87.125502|pmid=11580519|bibcode=2001PhRvL..87l5502S}}</ref> and later by researchers at [[Organization:Cornell University|Cornell University]].<ref name=":3">{{Cite journal|last1=Wen|first1=Xiao-Dong|last2=Hoffmann|first2=Roald |last3=Ashcroft|first3=N. W.|date=2011-06-15|title=Benzene under High Pressure: a Story of Molecular Crystals Transforming to Saturated Networks, with a Possible Intermediate Metallic Phase|journal=Journal of the American Chemical Society|volume=133 |issue=23|pages=9023–9035|doi=10.1021/ja201786y|pmid=21524117|issn=0002-7863}}</ref> In 2014, researchers at Penn State University created the first sp<sup>3</sup>-carbon nanothreads in collaboration with [[Organization:Oak Ridge National Laboratory|Oak Ridge National Laboratory]] and the [[Organization:Carnegie Institution for Science|Carnegie Institution for Science]].<ref name="tcfitz2014">T.C.Fitzgibbons et al., [http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4088.html Benzene-derived carbon nanothreads], [[Physics:Nature Materials|Nature Materials]], September 21, 2014</ref> Prior to 2014, and despite a century of investigation, benzene was thought to produce only hydrogenated amorphous carbon when compressed.<ref>{{Cite journal|last1=Ciabini|first1=Lucia|last2=Santoro|first2=Mario|last3=Gorelli|first3=Federico A.|last4=Bini|first4=Roberto|last5=Schettino |first5=Vincenzo|last6=Raugei|first6=Simone|date=2007|title=Triggering dynamics of the high-pressure benzene amorphization|journal=Nature Materials|language=En|volume=6|issue=1|pages=39–43 |doi=10.1038/nmat1803|pmid=17160003 |issn=1476-4660|bibcode=2007NatMa...6...39C}}</ref> As of 2015, threads at least 90 nanometers in length had been created (compared to .5 meters for CNTs).

== Structure ==
Since “diamond nanothreads” are sp<sup>3</sup>-bonded and one-dimensional they are unique in the matrix of [[Physics:Orbital hybridisation|hybridization]] (sp<sup>2</sup>/sp<sup>3</sup>) and dimensionality (0D/1D/2D/3D) for carbon nanomaterials.<ref>{{Cite journal|last1=Badding|first1=John V.|last2=Crespi|first2=Vincent H.|title=Synthesizing carbon nanothreads from benzene|url=http://www.spie.org/x112253.xml|journal=SPIE Newsroom|doi=10.1117/2.1201501.005713|year=2015}}</ref>

Assuming a topological unit cell of one or two benzene rings with at least two bonds interconnecting each adjacent pair of rings, 50 topologically distinct nanothreads have been enumerated.  15 of these are within 80 meV/carbon atom of the most stable member.<ref name=":4">{{Cite journal|last1=Xu|first1=En-shi|last2=Lammert|first2=Paul E.|last3=Crespi|first3=Vincent H.|date=2015-08-12|title=Systematic Enumeration of sp3 Nanothreads|journal=Nano Letters|volume=15|issue=8|pages=5124–5130 |doi=10.1021/acs.nanolett.5b01343|pmid=26207926|issn=1530-6984|bibcode=2015NanoL..15.5124X}}</ref> Some of the more commonly discussed nanothread structures are known informally as polytwistane, tube (3,0), and Polymer I.  Polytwistane is chiral.<ref name=":4" /><ref name=":5">{{Cite journal|last1=Barua|first1=Shiblee R.|last2=Quanz|first2=Henrik|last3=Olbrich|first3=Martin|last4=Schreiner|first4=Peter R.|last5=Trauner|first5=Dirk|last6=Allen|first6=Wesley D.|date=2014-02-03|title=Polytwistane|journal=Chemistry – A European Journal|language=en|volume=20|issue=6|pages=1638–1645|doi=10.1002/chem.201303081|pmid=24402729|issn=1521-3765}}</ref> Tube (3,0) can be thought of as the thinnest possible thread that can be carved out of the diamond structure, consisting of stacked cyclohexane rings.<ref name=":2" />  Polymer I was predicted to form from benzene at high pressure.<ref name=":3" />

Although there is compelling evidence from two dimensional X-ray diffraction patterns, [[Physics:Electron diffraction#Electron diffraction in a TEM|transmission electron diffraction]], and [[Physics:Solid-state nuclear magnetic resonance|solid-state nuclear magnetic resonance]] (NMR) for a structure consisting of hexagonally packed crystals of 6.5 Angstrom diameter nanothreads with largely (75 to 80%) sp<sup>3</sup>-bonding,<ref name="tcfitz2014" /><ref name=":1" /> the atomic structure of nanothreads is still under investigation. Nanothreads have also been observed by [[Engineering:Transmission electron microscopy|transmission electron microscopy]].<ref name="tcfitz2014" /> Individual threads have been observed to pack in hexagonal crystals and layer-lines indicative of order along their length have been observed.<ref>{{Cite journal|last1=Juhl|first1=Stephen J.|last2=Wang|first2=Tao|last3=Vermilyea|first3=Brian|last4=Li|first4=Xiang|last5=Crespi|first5=Vincent H.|last6=Badding|first6=John V.|last7=Alem|first7=Nasim|date=2019-04-05|title=Local Structure and Bonding of Carbon Nanothreads Probed by High-Resolution Transmission Electron Microscopy|journal=Journal of the American Chemical Society|volume=141|issue=17|pages=6937–6945|language=en|doi=10.1021/jacs.8b13405|pmid=30951295|s2cid=96449645 |issn=0002-7863|url=https://authors.library.caltech.edu/94559/1/jacs.8b13405.pdf}}</ref>

Nanothreads have also been classified by their degree of saturation.<ref name=":7" /> Fully [[Chemistry:Saturated and unsaturated compounds|saturated]] degree 6 nanothreads have no [[Chemistry:Double bond|double bond]]s remaining. Three bonds form between each pair of benzene molecules. Degree 4 nanothreads have a double bond remaining from benzene and thus only two bonds formed between each pair of benzene molecules.  Degree 2 have two double bonds remaining. Unless otherwise specified the term nanothread is assumed to refer to a degree six structure.

NMR has revealed that nanothread crystals consist of both degree 6 and degree 4 threads.<ref>{{Cite journal|last1=Duan|first1=Pu|last2=Li|first2=Xiang|last3=Wang|first3=Tao|last4=Chen|first4=Bo|last5=Juhl|first5=Stephen J.|last6=Koeplinger|first6=Daniel|last7=Crespi|first7=Vincent H.|last8=Badding|first8=John V.|last9=Schmidt-Rohr|first9=Klaus|date=2018-05-29|title=The Chemical Structure of Carbon Nanothreads Analyzed by Advanced Solid-State NMR|journal=Journal of the American Chemical Society|volume=140|issue=24|pages=7658–7666|language=en|doi=10.1021/jacs.8b03733|pmid=29808673|s2cid=207190929 |issn=0002-7863}}</ref> Moreover, spin diffusion experiments show that the sections of the threads that are fully saturated degree 6 must be at least 2.5&nbsp;nm long, if not longer.  NMR also shows that no second hydrocarbon or carbon phase is present in nanothread crystals.  Thus all of the sp<sup>2</sup> carbon is either in degree 4 nanothreads or small amounts of aromatic linker molecules, or even smaller amounts of C=O groups. NMR provides the chemical structural information necessary to refine syntheses towards pure degree 6 nanothreads, which are stronger than the partially saturated ones.<ref name="Demingos2019">{{Cite journal|last1=Demingos|first1=P. G.|last2=Muniz|first2=A. R.|date=2018|title=Electronic and mechanical properties of partially saturated carbon and carbon nitride nanothreads|journal=Journal of Physical Chemistry C|language=en|volume=123|issue=6|pages=3886–3891|doi=10.1021/acs.jpcc.8b11329|s2cid=104424307 |url=https://figshare.com/articles/Electronic_and_Mechanical_Properties_of_Partially_Saturated_Carbon_and_Carbon_Nitride_Nanothreads/7670465}}</ref>

==Carbon nitride nanothreads==
Pyridine compressed slowly under pressure forms carbon nitride C<sub>5</sub>H<sub>5</sub>N nanothread crystals.<ref>{{Cite journal|last1=Li|first1=Xiang|last2=Wang|first2=Tao|last3=Duan|first3=Pu|last4=Baldini|first4=Maria|last5=Huang|first5=Haw-Tyng|last6=Chen|first6=Bo|last7=Juhl|first7=Stephen J.|last8=Koeplinger|first8=Daniel|last9=Crespi|first9=Vincent H.|date=2018-03-23|title=Carbon Nitride Nanothread Crystals Derived from Pyridine|journal=Journal of the American Chemical Society|volume=140|issue=15|pages=4969–4972|doi=10.1021/jacs.7b13247|pmid=29569919|issn=0002-7863}}</ref> They exhibit the six-fold diffraction "signature" of nanothread formation.  NMR, chemical analysis and infrared spectroscopy provide further evidence for the synthesis of nanothreads from pyridine. Pyridine nanothreads incorporate significant amounts of nitrogen directly into their backbone. In contrast sp2 carbon nanotubes can only be doped with a small amount of nitrogen. A wide range of other functionalized nanothreads may be possible,<ref name=":9" /> as well as nanothreads from polycyclic aromatic hydrocarbon molecules.<ref name="Demingos2018">{{Cite journal|last1=Demingos|first1=P. G.|last2=Muniz|first2=A. R.|date=2019|title=Carbon nanothreads from polycyclic aromatic hydrocarbon molecules|journal=Carbon|language=en|volume=140|pages=644–652|doi=10.1016/j.carbon.2018.09.022|s2cid=105107235 }}</ref>

==Smallest nanothreads==
Extending the ability to design and create nanothread architecture from a non-aromatic, saturated molecule has been a recent interest in order to achieve an entirely sp3-bonded nanothread structure. Hypothetical nanothread architectures built from the smallest diamondoids ([[Chemistry:Adamantane|adamantane]]) have been proposed to have higher mechanical strength than [[Chemistry:Benzene|benzene]] nanothreads.<ref>{{cite journal |last1=Marutheeswaran |first1=S. |last2=Jemmis |first2=Eluvathingal D. |title=Adamantane-Derived Carbon Nanothreads: High Structural Stability and Mechanical Strength |journal=The Journal of Physical Chemistry C |date=15 March 2018 |volume=122 |issue=14 |pages=7945–7950 |doi=10.1021/acs.jpcc.7b12603 |issn=1932-7447}}</ref> The first experimental synthesis of a novel purely sp3 bonded one-dimensional carbon nanomaterial is realized via an endogenous solid-state polymerization of [[Chemistry:Cubane|cubane]]. Pre-arranged [[Chemistry:Cubane|cubane]] monomers in the bulk crystal undergo diradical polymerization guided by applied uniaxial stress, similar to [[Chemistry:Benzene|benzene]], produce a single-crystalline carbon nanomaterial. The [[Chemistry:Cubane|cubane]]-derived nanothread exhibits a linear [[Chemistry:Diamond|diamond]] structure with subnanometre-diameter of 0.2 nm, which is considered as the smallest member in the carbon nanothread family; thus, they promise to form the stiffest one-dimensional system known.<ref>{{cite journal |last1=Huang |first1=Haw-Tyng |last2=Zhu |first2=Li |last3=Ward |first3=Matthew D. |last4=Wang |first4=Tao |last5=Chen |first5=Bo |last6=Chaloux |first6=Brian L. |last7=Wang |first7=Qianqian |last8=Biswas |first8=Arani |last9=Gray |first9=Jennifer L. |last10=Kuei |first10=Brooke |last11=Cody |first11=George D. |last12=Epshteyn |first12=Albert |last13=Crespi |first13=Vincent H. |last14=Badding |first14=John V. |last15=Strobel |first15=Timothy A. |title=Nanoarchitecture through Strained Molecules: Cubane-Derived Scaffolds and the Smallest Carbon Nanothreads |journal=Journal of the American Chemical Society |date=10 February 2020 |volume=142 |issue=42 |pages=17944–17955 |doi=10.1021/jacs.9b12352 |pmid=31961671 |s2cid=210870993 }}</ref> 

== Properties ==
Every type of nanothread has a very high [[Physics:Young's modulus|Young's modulus]] (stiffness). The value for the strongest type of nanothread is around 900 GPa compared to steel at 200 GPa and diamond at over 1,200 GPa.<ref name=":0">{{Cite web|title = Super-Strong Diamond Nanothread Has People Dreaming Of A Space Elevator|url = http://www.iflscience.com/technology/super-strong-diamond-nano-thread-could-make-your-carbon-nanotubes-dreams-reality|website = IFLScience|access-date = 2015-11-29|date = November 28, 2015|first = Alfredo|last = Carpineti}}</ref> The strength of carbon nanothreads may rival or exceed that of carbon nanotubes (CNTs). [[Physics:Molecular dynamics|Molecular dynamics]] and [[Density functional theory]] simulations have indicated a stiffness on the order of carbon nanotubes (approx. 850 GPa) and a specific strength of approx. 4 × 10<sup>7</sup> N·m/kg.<ref name=":6">Roman, R. Kwan, K., and Cranford, S.W., [http://pubs.acs.org/doi/full/10.1021/nl5041012 Mechanical Properties and Defect Sensitivity of Diamond Nanothreads], [[Engineering:Nano Letters|Nano Letters]], Feb. 18, 2015, 15 (3), pp 1585–1590</ref><ref name="Demingos2019" />

Much as graphite [[Chemistry:Intercalation#Exfoliation|exfoliates]] into sheets and ultimately [[Physics:Graphene|graphene]], nanothread crystals exfoliate into fibers, consistent with their structure consisting of stiff, straight threads with a persistence length of ~100&nbsp;nm<ref name=":6" /> that are held together with van der Waals forces. These fibers exhibit [[Physics:Birefringence|birefringence]], as would be expected from their low dimensional character.<ref name=":1" /> In contrast, most polymers are much more flexible and often fold into crystalline lamella (see [[Physics:Crystallization of polymers|Crystallization of polymers]]) rather than forming into crystals that readily exfoliate.

Modeling suggests certain nanothreads may be auxetic, with a negative [[Physics:Poisson's ratio|Poisson ratio]].<ref>{{Cite journal|last1=Saha|first1=Biswajit|last2=Pratik|first2=Saied Md.|last3=Datta|first3=Ayan|date=2017-09-18|title=Coexistence of Normal and Auxetic Behavior in a Thermally and Chemically Stable sp3 Nanothread: Poly[5]asterane|journal=Chemistry – A European Journal|language=en|volume=23|issue=52|pages=12917–12923|doi=10.1002/chem.201702775|pmid=28683158|issn=1521-3765}}</ref> The [[Physics:Thermal conductivity|thermal conductivity]] of nanothreads has been modeled.<ref name=":8">{{Cite book|last1=Zhan|first1=Haifei|last2=Gu|first2=Yuantong|pages=185–204|doi=10.1016/b978-0-32-346240-2.00007-8|title = Thermal Transport in Carbon-Based Nanomaterials|year = 2017|isbn = 9780323462402|arxiv = 1803.06435|s2cid=4946467}}</ref><ref>{{Cite journal|last1=Zhan|first1=Haifei|last2=Zhang|first2=Gang|last3=Zhang|first3=Yingyan|last4=Tan|first4=V.B.C.|last5=Bell|first5=John M.|last6=Gu|first6=Yuantong|title=Thermal conductivity of a new carbon nanotube analog: The diamond nanothread|journal=Carbon|volume=98|pages=232–237|doi=10.1016/j.carbon.2015.11.012|year=2016|s2cid=55959962|url=https://eprints.qut.edu.au/90466/1/accepted_version.pdf}}</ref><ref>{{Cite journal|last1=Zhu|first1=Taishan|last2=Ertekin|first2=Elif|date=2016-04-11|title=Generalized Debye-Peierls/Allen-Feldman model for the lattice thermal conductivity of low-dimensional and disordered materials|journal=Physical Review B|volume=93|issue=15|pages=155414|doi=10.1103/PhysRevB.93.155414|arxiv=1602.02419|bibcode=2016PhRvB..93o5414Z|s2cid=119287470}}</ref> Modeling indicates their [[Physics:Band gap|Bandgaps]]  are tunable with strain over a wide range.<ref>{{Cite journal|last1=Wu|first1=Weikang|last2=Tai|first2=Bo|last3=Guan|first3=Shan|last4=Yang|first4=Shengyuan A.|last5=Zhang|first5=Gang|date=2018-02-08|title=Hybrid Structures and Strain-Tunable Electronic Properties of Carbon Nanothreads|journal=The Journal of Physical Chemistry C|volume=122|issue=5|pages=3101–3106|doi=10.1021/acs.jpcc.7b11549|issn=1932-7447|arxiv=1803.04694|s2cid=54707528}}</ref> The electrical conductivity of fully saturated nanothreads, driven by topology, may be much higher than expected.<ref>{{Cite journal|last1=Gryn’ova|first1=Ganna|last2=Corminboeuf|first2=Clémence|date=2019-02-21|title=Topology-Driven Single-Molecule Conductance of Carbon Nanothreads|journal=The Journal of Physical Chemistry Letters|language=en|volume=10|issue=4|pages=825–830|doi=10.1021/acs.jpclett.8b03556|issn=1948-7185|pmid=30668127|s2cid=58949557 }}</ref>

== Potential applications==
Nanothreads can be thought of essentially as "flexible diamond". The extremely high [[Engineering:Specific strength|specific strength]] predicted for them by modeling has attracted attention for applications such as [[Astronomy:Space elevator|space elevator]]s and would be useful in other applications related to transportation, aerospace, and sports equipment.  They may uniquely combine extreme strength, flexibility, and resilience.<ref name=":6" /><ref>{{Cite journal|last1=Zhan|first1=Haifei|last2=Zhang|first2=Gang|last3=Tan|first3=Vincent B. C.|last4=Cheng|first4=Yuan|last5=Bell|first5=John M.|last6=Zhang|first6=Yong-Wei|last7=Gu|first7=Yuantong|date=2016-05-26|title=From brittle to ductile: a structure dependent ductility of diamond nanothread|journal=Nanoscale|language=en|volume=8|issue=21|pages=11177–11184|doi=10.1039/c6nr02414a|pmid=27181833|issn=2040-3372|arxiv=1511.01583|bibcode=2016Nanos...811177Z|s2cid=18849867}}</ref> Chemically substituted nanothreads may facilitate load transfer between neighbors through covalent bonding to transfer their mechanical strength to a surrounding matrix.<ref name="tcfitz2014" /> Modeling also suggests that the kinks associated with Stone-Wales transformations in nanothreads may facilitate interfacial load transfer to a surrounding matrix, making them useful for high strength composites.<ref>{{Cite journal|last1=Zhan|first1=Haifei|last2=Zhang|first2=Gang|last3=Tan|first3=Vincent B. C.|last4=Gu|first4=Yuantong|date=2017-03-17|title=The best features of diamond nanothread for nanofibre applications|journal=Nature Communications|language=En|volume=8|pages=14863|doi=10.1038/ncomms14863|pmid=28303887|pmc=5357841|issn=2041-1723|arxiv=1709.08326|bibcode=2017NatCo...814863Z}}</ref> In contrast to carbon nanotubes, bonds to the exterior of nanothreads need not disrupt their carbon core because only three of the four tetrahedral bonds are needed form it. The “extra” bond usually formed to hydrogen could be instead be linked to another nanothread or another molecule or atom.<ref name="tcfitz2014" /> Nanothreads may thus be thought of as "hybrids" that are both hydrocarbon molecules and carbon nanomaterials. Bonds to carbon nanotubes require their carbon to change from near planar sp<sup>2</sup>-bonding to tetrahedral sp<sup>3</sup>-bonding, thus disrupting their tubular geometry and possibly weakening them.  Nanothreads may be less susceptible to loss of strength through defects than carbon nanotubes.<ref name=":6" /> Thus far the extreme strength predicted for carbon nanotubes has largely not been realized in practical applications because of issues with load transfer to the surroundings and defects at various length scales from that of atoms on up.

Exfoliation into individual nanothreads may be possible, facilitating further functionalization and assembly into functional materials.<ref name=":1" /> Theory indicates that "caged saturated hydrocarbons offering multiple σ-conductance channels (such as nanothreads) afford transmission far beyond what could be expected based upon conventional superposition laws, particularly if these pathways are composed entirely from quaternary carbon atoms."<ref>{{Cite journal|last1=Corminboeuf|first1=Clémence|last2=Gryn'ova|first2=Ganna|date=2019-01-22|title=Topology-Driven Single-Molecule Conductance of Carbon Nanothreads|journal=The Journal of Physical Chemistry Letters|volume=10|issue=4|pages=825–830|doi=10.1021/acs.jpclett.8b03556|pmid=30668127|s2cid=58949557 |issn=1948-7185}}</ref>

The carbon core of nanothreads is very stiff relative to the backbone of conventional polymers. They should thus be able to precisely orient molecular functions attached along their length (by substitution of hydrogen) relative to each other and to heteroatoms or unsaturated bonds in their backbone. These features may enable biological applications,<ref>{{Cite journal|last1=Hong|first1=Guosong|last2=Diao|first2=Shuo|last3=Antaris|first3=Alexander L.|last4=Dai|first4=Hongjie|date=2015-10-14|title=Carbon Nanomaterials for Biological Imaging and Nanomedicinal Therapy|journal=Chemical Reviews|volume=115|issue=19|pages=10816–10906|doi=10.1021/acs.chemrev.5b00008|pmid=25997028|issn=0009-2665}}</ref> for example. Defects, functional groups, and/or [[Chemistry:Heteroatom|heteroatom]]s<ref name=":9">{{Cite journal|last1=Silveira|first1=J. F. R. V.|last2=Muniz|first2=A. R.|date=2017|title=Functionalized diamond nanothreads from benzene derivatives|journal=Physical Chemistry Chemical Physics|language=en|volume=19|issue=10|pages=7132–7137|doi=10.1039/c6cp08655a|pmid=28229141|issn=1463-9084|bibcode=2017PCCP...19.7132S}}</ref> incorporated either into or exterior to the backbone of nanothreads with controlled orientation and distance between them may allow for robust, well controlled fluorescence. Doping and incorporation of heteroatoms such as nitrogen or boron into the nanothread backbone may allow for enhanced conducting or semiconducting properties<ref name="Demingos2019" /> of nanothreads that allow for application as photocatalysts, electron emitters,<ref name="tcfitz2014" /> or possibly superconductors.

Modeling suggests carbon nanothread resonators exhibit low dissipation and may be useful as chemical sensors that can detect very small mass changes.<ref>{{Cite journal|last1=Duan|first1=Ke|last2=Li|first2=Yijun|last3=Li|first3=Li|last4=Hu|first4=Yujin|last5=Wang|first5=Xuelin|title=Diamond nanothreads based resonators: ultrahigh sensitivity and low dissipation|journal=Nanoscale|volume=10|issue=17|pages=8058–8065|language=en|doi=10.1039/C8NR00502H|pmid=29671436|issn=2040-3372|date=2018-05-03}}</ref>

===Energy storage===
Simulations show some achiral nanothread bundles may have specific energy density (when twisted) higher than lithium batteries.<ref>{{cite journal | doi=10.1038/s41467-020-15807-7 | title=High density mechanical energy storage with carbon nanothread bundle | year=2020 | last1=Zhan | first1=Haifei | last2=Zhang | first2=Gang | last3=Bell | first3=John M. | last4=Tan | first4=Vincent B. C. | last5=Gu | first5=Yuantong | journal=Nature Communications | volume=11 | issue=1 | page=1905 | pmid=32312980 | pmc=7171126 }}</ref>

==See also==
{{div col|colwidth=22em}}
* [[Physics:Carbon nanotube|Carbon nanotube]]
* [[Chemistry:Boron nitride#Boron nitride nanotubes|Boron nitride nanotube]]
* [[Chemistry:Buckypaper|Buckypaper]]
* [[Physics:Carbide-derived carbon|Carbide-derived carbon]]
* Carbon nanocone
* Carbon nanofibers
* Carbon nanoparticles
* Carbon nanoscrolls
* [[Chemistry:Carbon nanotube chemistry|Carbon nanotube chemistry]]
* [[Chemistry:Colossal carbon tube|Colossal carbon tube]]
* [[Chemistry:Filamentous carbon|Filamentous carbon]]
* [[Chemistry:Graphene oxide paper|Graphene oxide paper]]
* [[Physics:List of software for nanostructures modeling|List of software for nanostructures modeling]]
* [[Biology:Molecular modelling|Molecular modelling]]
* Nanoflower
* [[Chemistry:Diamondoid|Diamondoid]]
* [[Physics:Graphene|Graphene]]
* [[Chemistry:Graphane|Graphane]]
* [[Software:Ninithi|Ninithi]] (nanotube modelling software)
* [[Chemistry:Organic semiconductor|Organic semiconductor]]
* [[Chemistry:Selective chemistry of single-walled nanotubes|Selective chemistry of single-walled nanotubes]]
* Silicon nanotubes
* [[Physics:Timeline of carbon nanotubes|Timeline of carbon nanotubes]]
* [[Chemistry:Vantablack|Vantablack]], a substance produced in 2014; the blackest substance known
{{div col end}}

== External links ==
* [http://www.technologyreview.com/view/543631/forget-graphene-and-carbon-nanotubes-get-ready-for-diamond-nanothread/ Forget Graphene and Carbon Nanotubes, Get Ready for Diamond Nanothread] technologyreview.com
* [http://www.spie.org/newsroom/5713-synthesizing-carbon-nanothreads-from-benzene?SSO=1/ Synthesizing Carbon Nanothreads from Benzene] spie.org
* [https://www.scientificamerican.com/article/liquid-benzene-squeezed-to-form-diamond-nanothreads/ Liquid Benzene Squeezed to Form Diamond Nanothreads] Scientific American
* [https://bg.chem.psu.edu/nanothreads.html Carbon Nanothread Bibliography]
*[http://cci.chem.psu.edu Center for Nanothread Chemistry]

==References==
{{Reflist|30em}}
{{Allotropes of carbon}}
{{emerging technologies|topics=yes|robotics=yes|manufacture=yes|materials=yes}}

{{DEFAULTSORT:Carbon Nanotube}}
[[Category:Refractory materials]]

{{Sourceattribution|Carbon nanothread}}