Modified Carbon Nanotubes and Methods of Forming Carbon Nanotubes

Abstract

In this invention, electrolytic, photochemical, chemical, and encapsulation processes can be used to achieve substantially completely stable doped carbon nanotubes. Preferred CNT structures and morphologies for achieving maximum doping effects are also described. Dopant formulations and methods for achieving doping of a broad distribution of tube types are also described.

We claim: 
     
         1 . A solid carbon nanotube (CNT) composition, comprising:
 carbon nanotubes,   at least 0.5 wt % S and at least 0.5 wt % Cl,   and exhibiting a tangential mode (TM) position with a peak maximum between 1593 to 1605 cm −1  in the Raman spectrum.   
     
     
         2 . The CNT composition of  claim 1 , further exhibiting a substantially bleached v s   1 →c s   1  in the optical absorbance spectrum. 
     
     
         3 . The CNT composition of any of the preceding claims having a bulk conductivity greater than 300 S/cm. 
     
     
         4 . The CNT composition of any of the preceding claims having a bulk conductivity in the range 300 S/cm to 50,000 S/cm. 
     
     
         5 . The CNT composition of any of the preceding claims having a bulk conductivity in the range of 300 to 10,000 S/cm. 
     
     
         6 . The CNT composition of any of the preceding claims having a bulk conductivity in the range of 2000 to 5000 S/cm. 
     
     
         7 . The CNT composition of any of the preceding claims wherein the composition is a network film. 
     
     
         8 . The CNT composition of any of the preceding claims having a volume fraction of CNTs greater than 0.40. 
     
     
         9 . The CNT composition of any of the preceding claims having a film thickness greater than 20 nm. 
     
     
         10 . The CNT composition of any of the preceding claims having a film thickness less than 500 nm. 
     
     
         11 . The CNT composition of any of the preceding claims comprising a mixture of single and multiwalled CNTs. 
     
     
         12 . The CNT composition of any of the preceding claims comprising at least 10 mass % bundles. 
     
     
         13 . The CNT composition of any of the preceding claims having G/D greater than 8 
     
     
         14 . The CNT composition of any of the preceding claims having G/D in the range of 8 to 40. 
     
     
         15 . The CNT composition of any of the preceding claims having G/D in the range of 14 to 18. 
     
     
         16 . The CNT composition of  claim 1  wherein the carbon nanotubes consist essentially of DWNT and/or MWNT. 
     
     
         17 . The CNT composition of  claim 1  wherein the carbon nanotubes consist essentially of SWNT. 
     
     
         18 . The CNT composition of any of the preceding claims comprising at least 10 mass % belts. 
     
     
         19 . A method of treating CNTs, comprising:
 providing CNTs, and   contacting the CNTs with a doping agent   
       and further characterized by at least one of the following:
 exposing the CNTs to a UV treatment; or 
 introducing defects into the CNTs such that they exhibit a G/D ratio in the range of about 14 to about 22 prior to adding a doping agent; or 
 exposing the CNTs to oxidative plasma treatment prior to or simultaneous with adding the doping agent; or 
 exposing the CNTs to electron beam irradiation prior to or simultaneous with adding the doping agent; or 
 using a doping catalyst to catalyze the doping step. 
 
     
     
         20 . The method of  claim 19  comprising exposing the CNTs to UV ozonation. 
     
     
         21 . The methods of any of  claims 19 - 20  comprising treating sequentially with different dopants to achieve preferred depletion levels in nanotubes with different bandgaps. 
     
     
         22 . The methods of any of  claims 19 - 21  wherein the CNTs are in the form of a film having a thickness less than 500 nm. 
     
     
         23 . The method of any of  claim 22  wherein the CNTs are in the form of a film having a thickness less then 200 nm 
     
     
         24 . The methods of any of  claims 19 - 23  comprising treating the CNTs with liquid doping agent. 
     
     
         25 . The method of any of  claims 19 - 23  comprising treating the CNTs with a solution containing at least 60% doping agent. 
     
     
         26 . The method of  claim 24  comprising contacting the CNTs with liquid thionyl chloride. 
     
     
         27 . The method of any of  claims 24 - 26  comprising treating the CNTs with a liquid containing a catalyst that increases the doping effect. 
     
     
         28 . The method of any of  claims 19 - 27  wherein the CNTs are in the form of a film and further wherein the treatment decreases sheet resistance by at least 8 times and the resulting film is air-stable—meaning that its conductivity does not degrade by more than 5% after 1 week of exposure of the treated CNTs to room temperature air. 
     
     
         29 . The method of any of  claims 19 - 27  wherein the CNTs are in the form of a film and further wherein the treatment decreases sheet resistance by about 10 to about 30 times, and the resulting film is air-stable—meaning that its conductivity does not degrade by more than 5% after 1 week of exposure of the treated CNTs to room temperature air. 
     
     
         30 . The method of any of  claims 19 - 29  wherein the treatment increases transmittance in the near infrared. 
     
     
         31 . The method of any of  claims 19 - 30  wherein catalysts to increase the doping effect are preferentially absorbed to the CNTs, and the CNTs are then treated with doping liquid. 
     
     
         32 . The method of  claim 19  wherein the CNTs are treated by UV light in the presence of oxygen. 
     
     
         33 . The method of any of  claims 19 - 32  wherein defects are introduced into CNT, such that the G/D ratio is in the range of 8 to 30. 
     
     
         34 . The method of any of  claims 19 - 32  wherein defects are introduced into CNT, such that the G/D ratio is in the range of 12 to 25. 
     
     
         35 . The method of any of  claims 19 - 32  wherein defects are introduced into CNT, such that the G/D ratio is in the range of 14 to 18. 
     
     
         36 . The method of any of  claims 19 - 23  comprising treating the CNTs with a gaseous dopant. 
     
     
         37 . The method of any of  claims 19 - 36  comprising treating the CNTs sequentially with multiple dopants. 
     
     
         38 . The method of any of  claims 19 - 37 , further comprising a step of encapsulating the doped CNT structures by overcoating with a polymer. 
     
     
         39 . The method of any of  claims 19 - 38  wherein the doping agent comprises thionyl chloride. 
     
     
         40 . The method of any of  claims 19 - 39  wherein the CNTs are contacted with excess doping agent for 10 minutes or less. 
     
     
         41 . A film prepared by any of  claims 19 - 40 . 
     
     
         42 . A multi-layer structure comprising a substrate, a storage layer, and a doped CNT layer in direct contact with the storage layer. 
     
     
         43 . The multi-layer structure of  claim 40  wherein the substrate is transparent and comprises glass, poly(ethylene terephthalate), poly(ethylene napthalate), polycarbonate, and poly(methyl methacrylate), high performance engineered films such as polyethersulfones, poly(ether ether ketone), polyarylenes, poly(cyclic olefin copolymer), or combinations thereof. 
     
     
         44 . The multi-layer structure of  claim 42  wherein the substrate is transparent in NIR or IR. 
     
     
         45 . The multi-layer structure of  claim 42  wherein the substrate comprises ZnS, ZnSe, sapphire, Ge, Si, or combinations thereof. 
     
     
         46 . The multi-layer structure of any of  claims 42 - 45  wherein the doped CNT layer comprises thionyl chloride. 
     
     
         47 . The multi-layer structure of any of  claims 42 - 46  wherein the storage layer comprises thionyl chloride. 
     
     
         48 . The multi-layer structure of any of  claims 42 - 47  wherein the storage layer comprises less than 0.01 wt % of dopant. 
     
     
         49 . The multi-layer structure of any of  claims 42 - 48  wherein the storage layer comprises a polymer. 
     
     
         50 . The multi-layer structure of  claim 49  wherein the storage layer comprises dopant plus the same polymer as the substrate. 
     
     
         51 . The multi-layer structure of any of  claims 42 - 50  wherein the storage layer and the substrate do not contain the same material. 
     
     
         52 . The multi-layer structure of any of  claims 42 - 51  wherein the storage layer comprises polyester resin, acrylic resin, epoxy resin, poly(ethylene terephthale), poly(butylene terephthalate), poly(methyl methacylate), polycarbonate, poly(ether ether ketone), or a composite filled with absorbent particles. 
     
     
         53 . The multi-layer structure of any of  claims 42 - 52 , further an encapsulating layer over the doped CNT layer such that the doped CNT layer is sandwiched between the storage layer and the encapsulant. 
     
     
         54 . The multi-layer structure of any of  claims 42 - 53  wherein the storage layer has a thickness of 50 nm or less. 
     
     
         55 . The multi-layer structure of any of  claims 42 - 54  wherein the doped CNT layer has a thickness of 500 nm or less. 
     
     
         56 . The multi-layer structure of any of  claims 42 - 55  wherein the trapped dopant interacts with the CNTs. 
     
     
         57 . The multi-layer structure of any of  claims 42 - 55  wherein the trapped dopant is latent until it is released into the CNT layer. 
     
     
         58 . A process of making the multi-layer structure of any of  claims 42 - 56  comprising providing a substrate and coating the substrate with a storage layer that absorbs less than 0.01 wt % of a dopant. 
     
     
         59 . A process of making the multi-layer structure of any of  claims 42 - 55  comprising providing a substrate and modifying the first 50 nm of the surface of the substrate by incorporating less than 0.01 wt % of dopant in the first 50 nm of the surface. 
     
     
         60 . The multi-layer structure of  claim 53  wherein the encapsulant comprises a polymer.