Gas sensor and manufacturing method thereof

Abstract

A gas sensor and manufacturing method thereof. The gas sensor includes a substrate, a pair of electrodes disposed on the substrate, and a gas sensing thin film covering the electrodes, the gas sensing thin film is made up of carbon nanotubes and tin oxide.

1 . A gas sensor, comprising: 
 a substrate;    a pair of electrodes on the substrate; and    a gas sensing thin film covering the electrodes;    wherein the gas sensing thin layer comprises carbon nanotubes and SnOx, wherein x=1-2.    
     
     
         2 . The gas sensor as claimed in  claim 1 , wherein the substrate is insulating material or semiconductor material.  
     
     
         3 . The gas sensor as claimed in  claim 2 , wherein the substrate is ceramic material.  
     
     
         4 . The gas sensor as claimed in  claim 3 , wherein the ceramic material is glass, aluminum oxide, silicon oxide, quartz, or mica.  
     
     
         5 . The gas sensor as claimed in  claim 2 , wherein the semiconductor material is silicon.  
     
     
         6 . The gas sensor as claimed in  claim 1 , wherein the electrode is gold, platinum, or silver.  
     
     
         7 . The gas sensor as claimed in  claim 1 , wherein the carbon nanotubes are single-walled carbon nanotubes (SWCNTs).  
     
     
         8 . The gas sensor as claimed in  claim 1 , wherein the carbon nanotubes are multi-walled carbon nanotubes(MWCNTs).  
     
     
         9 . The gas sensor as claimed in  claim 1 , wherein the ratio of the carbon nanotubes to the SnO x  is 0.001-5:100 by weight.  
     
     
         10 . The gas sensor as claimed in  claim 9 , wherein the ratio of the carbon nanotubes to the SnO x  is 0.001-0.05:100 by weight.  
     
     
         11 . The gas sensor as claimed in  claim 1 , wherein the electrode has a comb, strip, or helix shapes.  
     
     
         12 . The gas sensor as claimed in  claim 1 , further comprising an Ag/Pd layer on the end of the electrode.  
     
     
         13 . The gas sensor as claimed in  claim 12 , further comprising a pair of signal lines separately connected to the electrodes by the Ag/Pd layer to transfer a signal.  
     
     
         14 . A manufacturing method of a gas sensor, comprising: 
 providing a substrate with a pair of electrodes thereon;    coating a mixture of carbon nanotubes and a tin-containing organo-metallic solution on the substrate to fully cover the electrode;    oxidizing the mixture to obtain a gas sensing thin film composed of carbon nanotubes and tin oxide.    
     
     
         15 . The manufacturing method as claimed in  claim 1 , wherein the substrate is insulating material or semiconductor material.  
     
     
         16 . The manufacturing method as claimed in  claim 15 , wherein the substrate is ceramic material.  
     
     
         17 . The manufacturing method as claimed in  claim 16 , wherein the ceramic material is glass, aluminum oxide, silicon oxide, quartz, or mica.  
     
     
         18 . The manufacturing method as claimed in  claim 15 , wherein the semiconductor material is silicon.  
     
     
         19 . The manufacturing method as claimed in  claim 14 , wherein the electrode is gold, platinum, or silver.  
     
     
         20 . The manufacturing method as claimed in  claim 14 , wherein the carbon nanotubes are single-walled carbon nanotubes (SWCNTs).  
     
     
         21 . The manufacturing method as claimed in  claim 14 , wherein the carbon nanotubes are multi-walled carbon nanotubes (MWCNTs).  
     
     
         22 . The manufacturing method as claimed in  claim 14 , wherein the tin-containing organo-metallic solution is formed by solubilizing tin (II)-2-ethylhexanoate in 2-ethylhexanoic acid.  
     
     
         23 . The manufacturing method as claimed in  claim 22 , wherein the tin (II)-2-ethylhexanoate in the tin-containing organo-metallic solution is 0.5 to 30% by weight.  
     
     
         24 . The manufacturing method as claimed in  claim 23 , wherein the tin (II)-2-ethylhexanoate in the tin-containing organo-metallic solution is 5 to 20% by weight.  
     
     
         25 . The manufacturing method as claimed in  claim 14 , wherein the carbon nanotubes in the organo-metallic solution are 0.0001 to 1% by weight.  
     
     
         26 . The manufacturing method as claimed in  claim 25 , wherein the carbon nanotubes in the organo-metallic solution are 0.0005 to 0.1% by weight.  
     
     
         27 . The manufacturing method as claimed in  claim 14 , wherein the carbon nanotubes are dispersed in the tin-containing organo-metallic solution by ultrasonic or mechanical vibration.  
     
     
         28 . The manufacturing method as claimed in  claim 14 , wherein the mixture application is performed by spin coating, dip coating, screen printing, or spraying.  
     
     
         29 . The manufacturing method as claimed in  claim 14 , wherein the oxidizing step is performed at 400 to 700° C. for 20 to 60 minutes.  
     
     
         30 . The manufacturing method as claimed in  claim 14 , wherein the electrode has a comb, strip, or helix shape.  
     
     
         31 . The manufacturing method as claimed in  claim 14 , further comprising coating an Ag/Pd layer on the end of each electrode.  
     
     
         32 . The manufacturing method as claimed in  claim 31 , further comprising connection of the Ag/Pd layer separately to a signal line.  
     
     
         33 . A manufacturing method of gas sensor, comprising: 
 providing a substrate with a pair of electrode thereon;    coating a mixture of carbon nanotubes and a tin oxide solution to the substrate on fully cover the pair of electrodes; and    oxidizing the mixture to obtain a gas sensing thin film comprising the carbon nanotubes and the tin oxide.