Visual hydrogen sensors using chemochromic metal oxide microparticles or nanoparticles superficially coated with catalyst nanoparticles

Abstract

Pigments comprising chemochromic metal oxide microparticles or nanoparticles the surfaces of which are superficially coated with nanoparticles of catalyst material. The pigments are prepared by mechanical or wet chemical processes.

1 . A hydrogen sensing pigment comprising a powder of chemochromic metal oxide microparticles or nanoparticles, wherein each of the chemochromic microparticles or nanoparticles has a surface and the surfaces are superficially coated with multiple discrete nanoparticles of noble metal catalyst that are smaller than the chemochromic metal oxide microparticles or nanoparticles. 
     
     
         2 . The hydrogen sensing pigment of  claim 1 , wherein the microparticles or nanoparticles of chemochromic metal oxide are less than 100 microns in diameter. 
     
     
         3 . The hydrogen sensing pigment of  claim 1 , wherein the nanoparticles of noble metal catalyst are sized in a range of a few nanometers to a few tens of nanometers. 
     
     
         4 . (canceled) 
     
     
         5 . The hydrogen sensing pigment of  claim 1 , wherein the nanoparticles of noble metal catalyst are sized in a range of a 2 nanometers to 30 nanometers. 
     
     
         6 . The hydrogen sensing pigment of  claim 1 , wherein the chemochromic metal oxide is selected from a group consisting of tungsten oxide, molybdenum oxide, and niobium oxide. 
     
     
         7 . The hydrogen sensing pigment of  claim 1 , wherein the metal catalyst is selected from a group consisting of platinum, palladium, and ruthenium. 
     
     
         8 .- 12 . (canceled) 
     
     
         13 . A paint, dye, ink, or other coating material capable of detecting hydrogen gas, comprising:
 a chemochromic pigment that changes color upon exposure to hydrogen gas suspended in a medium that is permeable to hydrogen gas, wherein said pigment comprises: (i) multiple discrete microparticles or nanoparticles of a transition metal oxide that changes color upon reduction by hydrogen, each of the discrete microparticles or nanoparticles of the transition metal oxide having a surface; and (ii) multiple discrete catalyst nanoparticles, which are smaller than the microparticles nanoparticles of the transition metal oxide, superficially coated on the surfaces of the microparticles or nanoparticles of the transition metal oxide.   
     
     
         14 . The paint, dye, ink, or other coating material of  claim 13 , wherein the medium is selectively permeable to hydrogen gas as compared to oxygen and atmospheric contaminants. 
     
     
         15 . The paint, dye, ink, or other coating material of  claim 13 , wherein the microparticles or nanoparticles of the transition metal oxide superficially coated with the catalyst nanoparticles are encapsulated in a polymer that is selectively permeable to hydrogen gas as compared to oxygen and atmospheric contaminants. 
     
     
         16 . The paint, dye, ink, or other coating material of  claim 13 , wherein the microparticles or nanoparticles of the transition metal oxide superficially coated with the catalyst nanoparticles are combined with conventional color pigment material that does not change color. 
     
     
         17 . A chemochromic hydrogen sensor material, comprising:
 a pigment comprising powder particles of a transition metal oxide with a catalyst on surfaces of said powder particles to make the pigment chemochromically sensitive to hydrogen; and   a medium in which said pigment is suspended to provide a protective layer for said catalyst.   
     
     
         18 . The chemochromic hydrogen sensor material of  claim 17 , wherein said medium with the suspended pigment is at least one of the group consisting of paints, dyes, inks, and coatings. 
     
     
         19 . The chemochromic hydrogen sensor of  claim 17 , wherein said transition metal oxide comprises tungsten oxide. 
     
     
         20 . The sensor of  claim 17 , wherein said catalyst comprises platinum. 
     
     
         21 . The sensor of  claim 17 , wherein the transition metal oxide powder particles are microparticles or nanoparticles and the catalyst comprises metal catalyst powder nanoparticles.