Compositions comprising diatom frustules and applications thereof

Abstract

Disclosed embodiments concern a composition comprising a diatom frustule and two or more photocatalytic nanoparticles dispersed on the surface of the frustule. Also disclosed are embodiments of a method for making the composition. The nanoparticles are dispersed such that they are separate and not in physical contact with each other. An average distance between the nanoparticles may be from greater than 0 nm to 100 nm. The nanoparticles may comprise a dopant material. Paint compositions comprising the diatom frustule compositions are also contemplated. The diatom frustule composition may be useful for removing and/or degrading volatile organic compounds, such as those present in the atmosphere.

We claim: 
     
         1 . A composition, comprising:
 a diatom frustule; and   two or more photocatalytic metal oxide nanoparticles dispersed on a surface of the diatom frustule such that each nanoparticle is separate and not in direct physical contact with another nanoparticle;   wherein a portion of the surface of the diatom frustule is free from metal oxide.   
     
     
         2 . The composition of  claim 1 , wherein the two or more nanoparticles are not connected by a metal oxide film. 
     
     
         3 . The composition of  claim 1 , wherein the two or more nanoparticles are separated from each other by an average distance of from greater than 0 nm to 100 nm. 
     
     
         4 . The composition of  claim 1 , wherein the photocatalytic nanoparticles have a size of from greater than 0 to less than 100 nm. 
     
     
         5 . The composition of  claim 1 , wherein the photocatalytic nanoparticles comprise a transition metal. 
     
     
         6 . The composition of  claim 1 , wherein the photocatalytic nanoparticles comprise titanium, iron, copper, cobalt, nickel, chromium, silver, platinum, zinc, magnesium, calcium, vanadium, tin, cerium, scandium, manganese, copper, or a combination thereof. 
     
     
         7 . The composition of  claim 5 , wherein the photocatalytic nanoparticles comprise titanium oxide nanoparticles. 
     
     
         8 . The composition of  claim 5 , wherein the transition metal oxide nanoparticles further comprise a dopant. 
     
     
         9 . A paint composition, comprising:
 the composition of  claim 1 ; and   paint selected from polymer paint, stucco-like paint, dry powder paint, suspension paint, or emulsion paint, or a combination thereof.   
     
     
         10 . A method, comprising:
 mixing diatom frustules with a nanoparticle precursor in the absence of a solvent and at a first temperature to form a mixture; and   heating the mixture at a second temperature to form two or more photocatalytic metal oxide nanoparticles dispersed on a surface of each of the diatom frustules such that each nanoparticle is separate and not in direct physical contact with another nanoparticle;   wherein a portion of the surface of each of the diatom frustules is free from metal oxide.   
     
     
         11 . The method of  claim 10 , wherein combining the diatom frustules and the nanoparticle precursor, and forming the mixture are performed in the absence of a surfactant. 
     
     
         12 . The method of  claim 10 , wherein the nanoparticle precursor comprises a metal alkoxide, metal chloride, metal bromide, metal iodide, metal fluoride, metal sulfate, metal nitrate, metal oxide, metal hydroxide, metal carbonate or a combination thereof. 
     
     
         13 . The method of  claim 10 , further comprising adding a dopant precursor to the mixture prior to heating at the second temperature. 
     
     
         14 . The method of  claim 13 , wherein the dopant precursor comprises iron, zinc, magnesium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, or a combination thereof. 
     
     
         15 . The method of  claim 13 , wherein the dopant precursor is dissolved in a solvent. 
     
     
         16 . A method, comprising:
 exposing the composition of  claim 1  to a volatile organic compound; and   exposing the composition and volatile organic compound to visible light, UV light or any combination thereof such that the composition degrades the volatile organic compound to a non-toxic product.   
     
     
         17 . The method of  claim 14 , wherein exposing the composition comprises exposing the composition to a stream of air comprising the volatile organic compound. 
     
     
         18 . The method of  claim 14 , wherein exposing the composition comprises exposing the composition to a stream of water comprising the volatile organic compound. 
     
     
         19 . The method of  claim 14 , wherein exposing the composition comprises applying the composition to a surface. 
     
     
         20 . The method of  claim 19 , wherein the surface is an interior or exterior wall.