Porous metal oxide microspheres

Abstract

Porous metal oxide microspheres are prepared via a process comprising forming a liquid dispersion of polymer nanoparticles and a metal oxide; forming liquid droplets of the dispersion; drying the droplets to provide polymer template microspheres comprising polymer nanospheres; and removing the polymer nanospheres from the template microspheres to provide the porous metal oxide microspheres. The porous microspheres exhibit saturated colors and are suitable as colorants for a variety of end-uses.

1 . A bulk sample of porous microspheres having:
 an average diameter of from about 1 μm to about 75 μm; and   an average pore diameter of from about 50 nm to about 800 nm,   wherein the porosity of each porous microsphere is distributed throughout the volume of the porous microsphere.   
     
     
         2 . The bulk sample of  claim 1 , wherein the porous microspheres have an average diameter of from about 1 μm to about 50 μm. 
     
     
         3 . The bulk sample of  claim 1 , wherein the porous microspheres have an average pore diameter of from about 50 nm to about 500 nm. 
     
     
         4 . The bulk sample of  claim 1 , wherein the porous microspheres have an average porosity of from about 0.45 to about 0.65. 
     
     
         5 . The bulk sample of  claim 1 , wherein the porous microspheres have:
 an average diameter of from about 4.5 μm to about 9.9 μm;   an average porosity of from about 0.45 to about 0.65; and   an average pore diameter of from about 220 nm to about 300 nm.   
     
     
         6 . The bulk sample of  claim 1 , further comprising a matrix of a metal oxide, wherein the metal oxide is selected from the group consisting of silica, titania, alumina, zirconia, ceria, iron oxide, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof. 
     
     
         7 . The bulk sample of  claim 6 , wherein the metal oxide is present from about 60.0 wt % to about 99.9 wt %, based on the total weight of the porous microspheres. 
     
     
         8 . The bulk sample of  claim 1 , wherein the bulk sample exhibits a color observable by the human eye. 
     
     
         9 . The bulk sample of  claim 1 , wherein the bulk sample exhibits angle-independent color. 
     
     
         10 . A bulk sample of metal oxide porous microspheres exhibiting a color observable by the human eye, the porous microspheres having an average diameter of from about 1 μm to about 75 μm, and wherein the porous microspheres comprise one or more light absorbers. 
     
     
         11 . The bulk sample of  claim 10 , wherein the light absorbers are present from about 0.1 wt % to about 40.0 wt %, based on the total weight of the porous microspheres. 
     
     
         12 . The bulk sample of  claim 10 , wherein the porosity of each porous microsphere is distributed throughout the volume of the porous microsphere. 
     
     
         13 . The bulk sample of  claim 10 , wherein the metal oxide is selected from the group consisting of silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof. 
     
     
         14 . The bulk sample of  claim 10 , further comprising a substrate. 
     
     
         15 . The bulk sample of  claim 10 , wherein the porous microspheres have an average pore diameter from about 50 nm to about 999 nm. 
     
     
         16 . The bulk sample of  claim 10 , wherein the metal oxide is present from about 60.0 wt % to about 99.9 wt %, based on the total weight of the porous microspheres. 
     
     
         17 . A composition selected from an aqueous formulation, an oil-based formulation, an ink, a coating formulation, a food, a plastic, a cosmetic formulation, or a material for a medical application or a security application, the composition comprising porous microspheres having an average diameter of from about 1 μm to about 75 μm, wherein the porosity of each porous microsphere is distributed throughout the volume of the porous microsphere. 
     
     
         18 . The composition of  claim 17 , wherein the porous microspheres have an average pore diameter of from about 50 nm to about 800 nm. 
     
     
         19 . The composition of  claim 17 , wherein the composition exhibits angle-independent color. 
     
     
         20 . The composition of  claim 17 , wherein the porous microspheres have an average porosity of from about 0.45 to about 0.65.