Multipodal nanotubes and process for making same

Abstract

Nanostructures, nanostructure arrays and a method of forming same are provided, wherein the nanostructures comprise ordered, self-organized, anodically formed single nanotubes, multipodal nanotubes or a combination thereof.

1 . An electrochemical anodization method for producing a nanostructure array having single nanotubes, multipodal nanotubes, or a combination thereof, the method comprising:
 a. providing a substrate capable of undergoing anodization,   b. providing an electrolytic solution for receiving the substrate,   c. providing means for restricting the mobility of ions in the electrolytic solution, and   d. anodizing the substrate to produce single nanotubes, multipodal nanotubes or a combination thereof.   
     
     
         2 . The method of  claim 1 , wherein the means for restricting mass transport comprises providing an electrolytic solution having a mixture of:
 e. a solvent having a viscosity sufficient to restrict the mobility of ions,   f. a halide-bearing species, and   g. de-ionized water.   
     
     
         3 . The method of  claim 2 , wherein the solvent viscosity is between 3 and 1000 cP. 
     
     
         4 . The method of  claim 3 , wherein the solvent is selected from a group consisting of diethylene glycol (DEG) and ethylene glycol. 
     
     
         5 . The method of  claim 4 , wherein the electrolyte is DEG. 
     
     
         6 . The method of  claim 1 , wherein the concentration of the halide-bearing species is less than 0.5%. 
     
     
         7 . The method of  claim 6 , wherein the concentration of the halide-bearing species is between 0.25% and 0.3%. 
     
     
         8 . The method of  claim 6 , wherein the halide-bearing species is a fluoride-bearing or a chloride-bearing species. 
     
     
         9 . The method of  claim 8 , wherein the halide-bearing species is HF. 
     
     
         10 . The method of  claim 1 , wherein the anodization occurs at a voltage of at least 70V. 
     
     
         11 . The method of  claim 10 , wherein the anodization occurs at a voltage of between 120V to 150V. 
     
     
         12 . The method of  claim 1 , wherein the anodization occurs for a duration of at least 40 hours. 
     
     
         13 . The method of  claim 12 , wherein the anodization occurs for a duration of 45 to 47 hours. 
     
     
         14 . The method of  claim 1 , wherein the substrate is titanium. 
     
     
         15 . The method of  claim 1 , wherein the substrate may contain pre-existing nanostructures. 
     
     
         16 . The method of  claim 1 , wherein the means for restricting the mobility of ions comprises providing a substrate having pre-existing nanostructures. 
     
     
         17 . The method of  claim 16 , wherein the electrolytic solution comprises a mixture of:
 h. a solvent,   i. a halide-bearing species, and   j. de-ionized water.   
     
     
         18 . The method of  claim 17 , wherein the solvent has a viscosity between 3 and 1000 cP. 
     
     
         19 . The method of  claim 18 , wherein the solvent is formamide. 
     
     
         20 . The method of  claim 17 , wherein the concentration of the halide-bearing species is less than 0.5%. 
     
     
         21 . The method of  claim 20 , wherein the halide-bearing species is a fluoride-bearing species or a chloride-bearing species. 
     
     
         22 . The method of  claim 21 , wherein the fluoride-bearing species is NH4F. 
     
     
         23 . The method of  claim 17 , wherein the anodization occurs at a voltage of at least 10V. 
     
     
         24 . The method of  claim 17 , wherein the anodization occurs for a duration of at least 40 hours. 
     
     
         25 . The method of  claim 24 , wherein the anodization occurs for a duration of 45 to 47 hours. 
     
     
         26 . The method of  claim 17 , wherein the method further comprises:
 k. Rinsing the nanostructure array,   l. Performing at least one subsequent anodization.   
     
     
         27 . The method of  claim 26 , wherein the subsequent anodization comprises providing a second electrolytic solution comprising a mixture of:
 i. A solvent,   ii. A halide-bearing species, and   iii. De-ionized water.   
     
     
         28 . The method of  claim 27 , wherein the solvent viscosity is between 3-1000 cP. 
     
     
         29 . The method of  claim 28 , wherein the solvent is formamide. 
     
     
         30 . The method of  claim 27 , wherein the concentration of the halide-bearing species is less than 0.5%. 
     
     
         31 . The method of  claim 30 , wherein the halide-bearing species is a fluoride-bearing or chloride-bearing species. 
     
     
         32 . The method of  claim 31 , wherein the fluoride-bearing species is NH4F. 
     
     
         33 . The method of  claim 26 , wherein the subsequent anodization occurs at a voltage of at least 10V. 
     
     
         34 . The method of  claim 33 , wherein the subsequent anodization occurs at a voltage of 35V. 
     
     
         35 . The method of  claim 26 , wherein the voltage is increased to a voltage of at least 50V at a predetermined rate. 
     
     
         36 . The method of  claim 26 , wherein the subsequent anodization occurs for a duration of at least 3 hours. 
     
     
         37 . An electrochemical anodization method for producing a nanostructure array having complex hierarchical structure, comprising:
 a. providing a titanium substrate capable of undergoing anodization,   b. providing an electrolytic solution for receiving the substrate comprising a mixture of:
 i. a solvent having a viscosity of at least 32 cP, 
 ii. a fluoride-bearing species, wherein the concentration of the fluoride-bearing species is less than 0.5%, and de-ionized water, and 
   c. anodizing the substrate at a voltage of between 120V-150 V for at least 40 hours.   
     
     
         38 . An electrochemical anodization method for producing a nanostructure array having a complex hierarchical structure, comprising:
 a. Providing a titanium substrate capable of undergoing anodization, wherein the substrate comprises pre-existing nanostructures,   b. Providing an electrolytic solution for receiving the substrate comprising a mixture of:
 i. A solvent having a viscosity of between 3-1000 cP, 
 ii. A fluoride-bearing species, wherein the concentration of the fluoride bearing species is less than 0.5%, and 
 iii. De-ionized water, 
   c. Anodizing the substrate in a first step at a voltage of at least 10V,   d. Rinsing the nanostructure array, and   e. Anodizing the substrate in at least one subsequent step at a voltage of at least 35V.   
     
     
         39 . A nanostructure array comprising:
 a plurality of oriented, tapered nanostructures, wherein some or all of the nanostructures may be at least bipodal.   
     
     
         40 . The nanostructure array of  claim 39 , wherein the plurality of nanostructures may comprise a pore size of at least 150 nm.