Titanate and titania nanostructures and nanostructure assemblies, and methods of making same
The invention relates to nanomaterials and assemblies including, a micrometer-scale spherical aggregate comprising: a plurality of one-dimensional nanostructures comprising titanium and oxygen, wherein the one-dimensional nanostructures radiate from a hollow central core thereby forming a spherical aggregate.
1. A method of making anatase nanomaterials comprising:
(a) mixing titania powder and an alkali metal hydroxide solution to form a mixture;
(b) heating the mixture thereby forming a precipitate comprising one-dimensional alkali metal hydrogen titanate nanomaterials,
(c) neutralizing the alkali metal hydrogen titanate nanomaterials thereby forming hydrogen titanate nanomaterials; and
(d) hydrothermally processing the formed hydrogen titanate nanomaterials thereby forming anatase nanomaterials, wherein hydrothermal processing comprises dispersing the hydrogen titanate nanomaterials in water under neutral conditions, and heating at about 100° C. to about 200° C.
2. The method of claim 1 wherein the ratio, based on relative mass, of the hydrogen titanate nanomaterials:water is about 2:1 to about 10:3.
3. The method of claim 1 wherein the alkali metal hydroxide is lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, or combinations thereof.
4. The method of claim 1 wherein the temperature to which the mixture is heated in step (b) is about 100° C. to about 145° C., whereby the formed hydrogen titanate nanomaterials are at least 99% nanotubes.
5. The method of claim 4 wherein the formed anatase nanomaterials are single crystalline anatase nanoparticles.
6. The method of claim 1 wherein the temperature to which the mixture is heated in step (b) is about 150° C. to about 200° C., whereby the formed hydrogen titanate nanomaterials are at least 99% nanowires, wherein nanowires with diameters less than 200 nm are designated as small, and wherein nanowires with diameters of greater than about 200 nm are designated as large.
7. The method of claim 6 wherein the formed anatase nanomaterials are single crystalline anatase nanowires which are formed from the small hydrogen titanate nanowires.
8. The method of claim 6 wherein the formed anatase nanomaterials are anatase nanocrystal aggregates which are formed from the large hydrogen titanate nanowires.