Method for synthesis of titanium dioxide nanotubes using ionic liquids

Abstract

The invention is directed to a method for producing titanium dioxide nanotubes, the method comprising anodizing titanium metal in contact with an electrolytic medium containing an ionic liquid. The invention is also directed to the resulting titanium dioxide nanotubes, as well as devices incorporating the nanotubes, such as photovoltaic devices, hydrogen generation devices, and hydrogen detection devices.

1 . A method for producing titanium dioxide nanotubes, the method comprising
 anodizing titanium metal in contact with an electrolytic medium comprised of an ionic liquid.   
     
     
         2 . The method of  claim 1 , wherein the ionic liquid has the formula: 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are each independently a saturated or unsaturated, straight-chained, branched, or cyclic hydrocarbon group having at least one carbon atom, and optionally substituted with one or more oxygen, nitrogen, and/or fluorine atoms; and X −  is a counteranion. 
       
     
     
         3 . The method of  claim 2 , wherein R 1  and R 2  each contain up to six carbon atoms. 
     
     
         4 . The method of  claim 2 , wherein R 1  and R 2  are straight-chained, branched, or cyclic alkyl groups. 
     
     
         5 . The method of  claim 4 , wherein said alkyl groups contain up to six carbon atoms. 
     
     
         6 . The method of  claim 1 , wherein said ionic liquid contains a fluorine-containing counteranion. 
     
     
         7 . The method of  claim 2 , wherein said counteranion is a fluorine-containing anion. 
     
     
         8 . The method of  claim 6 , wherein said fluorine-containing anion is selected from the group consisting of BF 4   − , PF 6   − , N[SO 2 CF 3 ] 2   − , N[SO 2 CF 2 CF 3 ] 2 , and CF 3 SO 3   − . 
     
     
         9 . The method of  claim 1 , wherein the electrolytic medium further comprises an amount of water. 
     
     
         10 . The method of  claim 9 , wherein said amount of water is at least about 25 wt % by total weight of ionic liquid and water. 
     
     
         11 . The method of  claim 9 , wherein said amount of water is at least about 50 wt % by total weight of ionic liquid and water. 
     
     
         12 . The method of  claim 9 , wherein said amount of water is at least about 75 wt % by total weight of ionic liquid and water. 
     
     
         13 . The method of  claim 1 , wherein said titanium dioxide nanotubes possess an outer diameter of or less than 45 nm. 
     
     
         14 . The method of  claim 1 , wherein said titanium dioxide nanotubes possess an outer diameter of or less than 40 nm. 
     
     
         15 . The method of  claim 1 , wherein said titanium dioxide nanotubes possess an outer diameter of or less than 35 nm. 
     
     
         16 . The method of  claim 1 , wherein said titanium metal is in the form of a foil. 
     
     
         17 . A composition comprising titanium dioxide nanotubes having an outer diameter of or less than 45 nm. 
     
     
         18 . A composition comprising titanium dioxide nanotubes having an outer diameter of or less than 40 nm. 
     
     
         19 . A composition comprising titanium dioxide nanotubes having an outer diameter of or less than 35 nm. 
     
     
         20 . The composition of  claim 17 , wherein said titanium dioxide nanotubes are in the form of an ordered array arranged substantially perpendicular on a substrate. 
     
     
         21 . The composition of  claim 17 , wherein said titanium dioxide nanotubes possess a length-to-diameter aspect ratio of at least 100. 
     
     
         22 . A photovoltaic device containing the titanium dioxide nanotubes of  claim 17 . 
     
     
         23 . A photovoltaic device containing the titanium dioxide nanotubes of  claim 21 . 
     
     
         24 . A hydrogen generation device containing the titanium dioxide nanotubes of  claim 17 . 
     
     
         25 . A hydrogen generation device containing the titanium dioxide nanotubes of  claim 21 .