# US 8,465,647 B2 · Isolation of single-walled carbon nanotubes from double and multi-walled carbon nanotubes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,465,647 B2 - Document ID: US8465647B2 - Status: Granted - Kind: B2 - Application number: 12/636,426 - Filed: 2009-12-11 - Published: 2011-06-16 - Granted: 2013-06-18 - Earliest claimed: 2009-12-11 - Assignees: International Business Machines Corporation - Applicants: Ageeth A. Bol; George S. Tulevski - Inventors: Ageeth A. Bol; George S. Tulevski - Web page: https://patentgrep.com/patent/US8465647B2 ## CPC - B01D 21/262: {by using a centrifuge} - B01D 17/0217: {by centrifugal force} - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - B82Y 40/00: Manufacture or treatment of nanostructures - C01B 32/17: Purification - C01B 32/172: Sorting - C01B 2202/02: Single-walled nanotubes - Y10S 977/845: Purification or separation of fullerenes or nanotubes - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A method and system are disclosed for separating single-walled carbon nanotubes from double and multi-walled carbon nanotubes by using the difference in the buoyant density of Single-Walled versus Multi-Walled carbon nanotubes. In one embodiment, the method comprises providing a vessel with first and second solutions. The first solution comprises a quantity of carbon nanotubes, including single-walled carbon nanotubes and double and multi-walled carbon nanotubes. The single walled nanotubes have a first density, the double and multi-walled nanotubes having a second density. The second solution in the vessel has a third density between said first and second densities. The vessel is centrifuged to form first and second layers in the vessel, with the second solution between said first and second layers. The single-walled carbon nanotubes are predominantly in the first layer, and the second and multi-walled carbon nanotubes are predominantly in the second layer. ## Claims ### Claim 1 A method of separating single-walled carbon nanotubes from double and multi-walled carbon nanotubes, the method comprising: providing a vessel with first and second solutions, said first solution comprising a quantity of carbon nanotubes, including single-walled carbon nanotubes dispersed in the first solution and having a first density, and double and multi-walled carbon nanotubes dispersed in the first solution and having a second density, and wherein said second solution has a third density between said first and second densities; centrifuging the vessel to separate the single-walled carbon nanotubes from the double and multi-walled carbon nanotubes by forming first and second separate layers of the nanotubes in the vessel with the second solution between and separating said first and second layers, wherein the single-walled carbon nanotubes are predominantly in the first layer, and the second and multi-walled carbon nanotubes are predominantly in the second layer; and after the centrifuging, removing at least some of the first layer from the vessel to remove at least some of the single-walled carbon nanotubes from the vessel; and wherein the first solution has a combined density less than said third density to cause the single-walled carbon nanotubes to sediment during said centrifuging at an interface of the first layer of the nanotubes and the second solution. ### Claim 2 (depends on 1) The method according to claim 1, wherein the providing includes depositing the quantity of carbon nanotubes in the vessel. ### Claim 3 (depends on 1) The method according to claim 1, wherein the providing includes dispersing a starting material including said quantity of carbon nanotubes, in an aqueous solution. ### Claim 4 (depends on 3) The method according to claim 3, further comprising sonicating said quantity of carbon nanotubes. ### Claim 5 (depends on 4) The method according to claim 4, wherein the sonicating includes sonicating said quantity of carbon nanotubes before dispersing the starting material in the aqueous solution. ### Claim 6 (depends on 3) The method according to claim 3, wherein the providing includes depositing said starting material in the vessel above the second solution. ### Claim 7 (depends on 6) The method according to claim 6, wherein the first solution has a combined density less than said third density. ### Claim 8 (depends on 1) The method according to claim 1, wherein the providing includes providing the vessel with the first solution above the second solution. ### Claim 9 (depends on 1) The method according to claim 1, wherein the first density is less than said third density. ### Claim 10 (depends on 1) The method according to claim 1, wherein said first layer is above the second solution, and the second layer is below the second solution. ### Claim 11 (depends on 1) The method according to claim 1, wherein the depositing includes dispersing a starting material including said quantity of carbon nanotubes, in an aqueous solution. ### Claim 12 (depends on 11) The method according to claim 11, further comprising the step of sonicating said aqueous material before dispersing the starting material in said aqueous solution. ### Claim 13 (depends on 11) The method according to claim 11, wherein the depositing includes depositing said starting material in the vessel above the second solution. ### Claim 14 A method of obtaining single-walled carbon nanotubes, the method comprising: depositing a first solution including a quantity of carbon nanotubes in a vessel, said quantity including single-walled carbon nanotubes dispersed in the first solution and having a first density, and double and multi-walled carbon nanotubes dispersed in the first solution and having a second density; providing the vessel with a second solution having a density between said first and second densities; centrifuging the vessel to separate the single-walled carbon nanotubes from the double and multi-walled carbon nanotubes by forming in the vessel a first layer predominantly of the single-walled carbon nanotubes, and a separate, second layer predominantly of the double and multi-walled carbon nanotubes, with said second solution between and separating the first single-walled carbon nanotubes layer and the second double and multi-walled carbon nanotubes layer; after the centrifuging, removing a portion of the single-walled carbon nanotubes from the vessel; and wherein the first solution has a combined density less than said third density to cause the single-walled carbon nanotubes to sediment during said centrifuging at an interface of the first layer of the nanotubes and the second solution. ### Claim 15 (depends on 14) The method according to claim 14, wherein the centrifuging includes forcing the double and multi-walled carbon nanotubes to a level in the vessel below the second solution. ### Claim 16 A method of isolating single-walled carbon nanotubes from double and multi-walled carbon nanotubes, the method comprising: providing a vessel with a first solution including a quantity of carbon nanotubes, including single-walled carbon nanotubes dispersed in the first solution and having a first buoyant density, and double and multi-walled carbon nanotubes dispersed in the first solution and having a second buoyant density, wherein said first and second buoyant densities are different; and using the difference in said first and second buoyant densities to separate the single-walled carbon nanotubes from the double and multi-walled carbon nanotubes in the vessel by forming in the vessel a first layer predominantly of the single-walled carbon nanotubes, and a separate, second layer predominantly of the double and multi-walled carbon nanotubes with a second liquid solution having a third density, between the first and second buoyant densities, between and separating said first and second layers; and wherein the first solution has a combined density less than said third density to cause the single-walled carbon nanotubes to sediment during said centrifuging at an interface of the first layer of the nanotubes and the second solution. ### Claim 17 (depends on 16) The method according to claim 16, wherein said using includes centrifuging the vessel to form first and second layers therein, wherein the single-walled carbon nanotubes are predominantly in the first layer, and the second and multi-walled carbon nanotubes are predominantly in the second layer. ### Claim 18 (depends on 17) The method according to claim 17, wherein the using includes using the second liquid solution to separate the first layer from the second layer. ### Claim 19 (depends on 18) The method according to claim 18, wherein the second liquid solution has a buoyant density between said first and second buoyant densities. ### Claim 20 (depends on 19) The method according to claim 19, wherein the single walled carbon nanotubes and the double and multi-walled carbon nanotubes have a combined buoyant density less than the buoyant density of said second liquid solution.