Robust low resistance vapor sensor materials

• US 20080017507A1
• Filed: 07/18/2006
• Published: 01/24/2008
• Est. Priority Date: 07/18/2006
• Status: Active Grant

• Current Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Original Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Inventors: Amadio, Blase S., Ramamurthy, Praveen C.
• Granted Patent: US 8,012,420 B2
• Time in Patent Office: Days
• US Class Current: 204/400
• CPC Class Codes: G01N 27/126 comprising organic polymers
• CPC Class Codes: G01N 27/127 comprising nanoparticles

Abstract

Compositions for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e., conductometric sensors) are provided. Robust sensor film compositions that have low resistance, high conductivity, and greater temperature stability and sensitivity to chemical analytes are provided, as well as methods of making these sensor films. Such sensor film compositions include a matrix having a polymer resin and a plurality of conductive particles comprising an axial-geometry conductive particle. Exemplary axial-geometry conductive particles comprise graphene, such as a carbon nanotube. Blends of conductive particles are also contemplated, including blends of axial-geometry conductive particles, such as carbon nanotubes, and carbon black.

Claims

1. A conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a crosslinked polymer and a plurality of particles comprising a conductive axial-geometry particle species homogeneously distributed within said matrix; and

wherein the sensor film exhibits a change in resistance when in the presence of the one or more chemical analytes.

2. The sensor film according to claim 1 wherein said conductive axial-geometry particle species is selected from the group consisting of:

whiskers, fibers, rods, filaments, tubes and mixtures thereof.

3. The sensor film according to claim 1 wherein said conductive axial-geometry particle species comprises carbon.

4. The sensor film according to claim 3 wherein said conductive axial-geometry particle species comprises graphene.

5. The sensor film according to claim 4 wherein at least one of said conductive axial-geometry particle species is a carbon nanotube.

6. The sensor film according to claim 5 wherein said carbon nanotube is selected from the group consisting of:

single walled nanotubes, multiwalled nanotubes, and mixtures thereof.

7. The sensor film according to claim 5 wherein said carbon nanotube has a bulk electrical conductivity of greater than or equal to about 100 S/cm.

8. The sensor film according to claim 1 wherein said axial-geometry conductive particle species has an aspect ratio of greater than about 500.

9. The sensor film according to claim 1 wherein said plurality of particles further comprises a conductive carbon black particle species having an N₂ adsorption of between about 8 to about 25 m²/g and a DBP of about 1 to about 180 ml/100 g.

10. The sensor film according to claim 1 wherein the sensor film is a low resistance sensor film and has a base resistance is less than or equal to about 10 Ohm.

11. The sensor film according to claim 1 wherein said cross-linked polymer comprises a siloxane monomer having at least one hydrocarbon side group with greater than or equal to two carbon atoms.

12. The sensor film according to claim 1 wherein said crosslinked polymer comprises an octylmethylsiloxane monomer.

13. A low resistance conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a crosslinked polymer comprising siloxane and a plurality of particles including a conductive particle species comprising graphene that is homogeneously distributed within said matrix; and

wherein the film exhibits a base resistance that is less than or equal to about 10 Ohm.

14. The sensor film according to claim 13 wherein said conductive particle comprising graphene is selected from the group consisting of:

nanotubes, nanofibers, whiskers, rods, filaments, caged structures, buckyballs, and mixtures thereof.

15. The sensor film according to claim 13 wherein at least one of said conductive particles comprising graphene is a nanotube.

16. The sensor film according to claim 15 wherein said nanotube is selected from the group consisting of:

single walled nanotubes, multiwalled nanotubes, and mixtures thereof.

17. The sensor film according to claim 13 wherein said plurality of particles further comprises conductive carbon black particles having an N₂ adsorption of between about 8 to about 25 m²/g and a DBP of about 1 to about 180 ml/100 g.

18. The sensor film according to claim 13 wherein said cross-linked polymer comprises a siloxane monomer having at least one hydrocarbon side group with greater than or equal to two carbon atoms.

19. A low resistance conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a crosslinked polymer comprising siloxane and a plurality of particles homogeneously distributed within said matrix, wherein said particles comprise a first species selected from carbon nanotubes, nanofibers, nanofilaments, and mixtures thereof, and a second species comprising carbon black; and

wherein the sensor film exhibits a change in resistance when in the presence of the one or more chemical analytes.

20. The sensor film according to claim 19 wherein said carbon black has an N₂ adsorption of between about 8 to about 25 m²/g and a DBP of about 1 to about 180 ml/100 g.