Nanomaterial-based gas sensors

Abstract

A gas sensing device (nanosensor) includes a substrate with at least a pair of conductive electrodes spaced apart by a gap, and an electrochemically functionalized semiconductive nanomaterial bridging the gap between the electrodes to form a nanostructure network. The nanomaterial may be single-walled carbon nanotubes (SWNTs) functionalized by the deposition of nanoparticles selected from the group consisting of an elemental metal (e.g., gold or palladium), a doped polymer (e.g., camphor-sulfonic acid doped polyaniline), and a metal oxide (e.g. tin oxide). Depending on the nanoparticles employed in the functionalization, the nanosensor may be used to detect a selected gas, such as hydrogen, mercury vapor, hydrogen sulfide, nitrogen dioxide, methane, water vapor, and/or ammonia, in a gaseous environment.

1 - 5 . (canceled) 
   
   
       6 . The method of  claim 31 , wherein the metal nanoparticles are selected from the group consisting of palladium nanoparticles and gold nanoparticles. 
   
   
       7 . The method of  claim 31 , wherein the nanomaterial is selected from the group consisting of at least one of nanowires, single-walled carbon nanotubes, multi-walled carbon nanotubes, silicon nanowires, zinc oxide nanostructures, tin oxide nanowires, indium oxide nanowires, carbon boride nanotubes, carbon nitride nanotubes, and general B x C y N z  nanotube structures. 
   
   
       8 . The method of  claim 31 , wherein the nanoparticles are metal nanoparticles, and the step of electrodepositing the nanoparticles on the nanomaterial includes electrolytically depositing the metal nanoparticles on the nanomaterial. 
   
   
       9 . The method of  claim 31 , wherein the nanoparticles are doped polyaniline nanoparticles, and the step of electrodepositing the nanoparticles on the nanomaterial includes electrolytically depositing the doped polyaniline nanoparticles on the nanomaterial. 
   
   
       10 . The method of  claim 31 , wherein the nanoparticles are metal oxide nanoparticles, and the step of electrodepositing the nanoparticles on the nanomaterial includes electrolytically depositing the metal oxide nanoparticles on the nanomaterial. 
   
   
       11 . The method of  claim 31 , wherein the step of forming the nanostructure network comprises the step of forming a pattern of conductive electrodes on a substrate. 
   
   
       12 . The method of  claim 11 , wherein the step of forming the nanostructure network further comprises the steps of placing a nanomaterial suspension on the electrodes and drying the suspension to leave a nanomaterial structure on the electrodes. 
   
   
       13 . The method of  claim 12 , wherein the step of forming the nanostructure network further comprises the step of annealing the nanomaterial structure. 
   
   
       14 . The method of  claim 12 , wherein the nanomaterial suspension comprises single walled carbon nanotubes (SWNTs) dispersed in a solvent in a concentration in the range of 0.01 μg/mL to 1.0 μg/mL. 
   
   
       15 . The method of  claim 9 , wherein the doped polyaniline particles are made from polyaniline and a dopant selected from the group consisting of camphor-sulfonic acid (CSA), chloride (Cl − ), perchlorate (ClO 4   − ), acrylic acid (C 3 H 4 O 2 ), tetraethylammonium perfluorooctane sulfonate (TEAPFOS), and para-toluene sulfonic acid (CH 3 C 6 H 4 SO 3 H). 
   
   
       16 . The method of  claim 15 , wherein the nanoparticles are made of camphor-sulfonic acid (CSA)-doped polyaniline, and wherein the step of electrodepositing the nanoparticles includes the steps of applying an aqueous solution of deoxygenated 0.01 M to 1 M aniline and 0.01 M to 1 M CSA on the nanostructure, and applying electrolysis to the solution to electrolytically deposit CSA-doped polyaniline nanoparticles onto the nanostructure. 
   
   
       17 . A method of detecting a specific gas in a gaseous environment, comprising:
 (a) providing a gas sensor as defined in  claim 24 ;   (b) measuring the value of an electrical parameter of the sensor when the sensor is exposed to the gaseous environment including the specific gas; and   (c) comparing the measured value of the parameter to a predetermined baseline value of the parameter.   
   
   
       18 . The method of  claim 17 , wherein the parameter is resistance. 
   
   
       19 . The method of  claim 17 , wherein the specific gas is hydrogen, and wherein the nanoparticles are made of palladium. 
   
   
       20 . The method of  claim 17 , wherein the specific gas is selected from the group consisting of at least one of hydrogen sulfide and mercury vapor, and wherein the nanoparticles are made of gold. 
   
   
       21 . The method of  claim 17 , wherein the specific gas is selected from the group consisting of at least one of ammonia, nitrogen dioxide, and water vapor, and wherein the nanoparticles are made of doped polyaniline. 
   
   
       22 . The method of  claim 21 , wherein the specific gas is selected from the group consisting of at least one of ammonia and nitrogen dioxide, and wherein the nanoparticles are made of camphor-sulfonic acid-doped polyaniline. 
   
   
       23 . The method of  claim 17 , wherein the specific gas is selected from the group consisting of at least one of ammonia and methane, and wherein the nanoparticles are made of tin oxide. 
   
   
       24 . A device for sensing a specific gas in a gaseous environment, comprising:
 a substrate having a pair of conductive electrodes formed thereon and defining a gap therebetween;   a nanomaterial structure bridging the gap between the electrodes; and   a plurality of gas-sensitive nanoparticles applied to the nanomaterial structure, wherein the nanoparticles are of a material selected that renders the nanomaterial structure sensitive to the specific gas, and wherein the nanoparticles are made of a material selected from the group consisting of gold, palladium, camphor-sulfonic acid-doped polyaniline, chloride-doped polyaniline, perchlorate-doped polyaniline, acrylic acid-doped polyaniline, tetraethylammonium perfluorooctane sulfonate (TEAPFOS)-doped polyaniline, para-toluene sulfonic acid-doped polyaniline, and tin oxide.   
   
   
       25 . The device of  claim 24 , wherein the specific gas is hydrogen, and wherein the nanoparticles are made of palladium. 
   
   
       26 . The device of  claim 24 , wherein the specific gas is selected from the group consisting of at least one of hydrogen sulfide and mercury vapor, and wherein the nanoparticles are made of gold. 
   
   
       27 . The device of  claim 24 , wherein the specific gas is selected from the group consisting of at least one of ammonia, nitrogen dioxide and water vapor, and wherein the nanoparticles are made of doped polyaniline. 
   
   
       28 . The device of  claim 27 , wherein the specific gas is selected from the group consisting of at least one of ammonia and nitrogen dioxide, and wherein the nanoparticles are made of camphor-sulfonic acid-doped polyaniline. 
   
   
       29 . The device of  claim 24 , wherein the specific gas is selected from the group consisting of at least one of ammonia and methane, and wherein the nanoparticles are made of tin oxide. 
   
   
       30 . The device of  claim 24 , wherein the nanomaterial of the nanomaterial structure is selected from the group consisting of at least one of nanowires, single-walled carbon nanotubes, multi-walled carbon nanotubes, silicon nanowires, zinc oxide nanostructures, tin oxide nanowires, indium oxide nanowires, carbon boride nanotubes, carbon nitride nanotubes, and general B x C y N z  nanotube structures. 
   
   
       31 . A method of manufacturing a device for sensing a specific gas in a gaseous environment, the method comprising the steps of:
 forming at least two separate conductive contacts on a substrate;   forming a structure of nanomaterial having a specified electrical parameter onto the substrate so as to connect the at least two contacts;   selecting nanoparticles made of a material that, when applied to the nanomaterial, alters the selected electrical parameter in the presence of the specific gas, wherein the material of the nanoparticles is selected from the group consisting of metal nanoparticles, doped polyaniline nanoparticles, and metal oxide nanoparticles; and   electrodepositing the selected nanoparticles on the nanomaterial.