Method of making controlled morphology metal-oxides
A method of making metal oxides having a preselected morphology includes preparing a suspension that includes a solvent, polymeric nanostructures having multiplicities of hydroxyl surface groups and/or carboxyl surface groups, and a metal oxide precursor. The suspension has a preselected ratio of the polymeric nanostructures to the metal oxide precursor of at least 1:3, the preselected ratio corresponding to a preselected morphology. Subsequent steps include depositing the suspension onto a substrate, removing the solvent to form a film, removing the film from the substrate, and annealing the film to volatilize the polymeric nanostructures and convert the metal oxide precursor to metal oxide nanoparticles having the preselected morphology or to a metal oxide nanosheet including conjoined nanoparticles having the preselected morphology.
1. A method of making metal oxides having a preselected morphology comprising the steps of:
a. preparing an aqueous suspension comprising water, polymeric nanostructures having multiplicities of surface groups including at least one surface group selected from the group consisting of a hydroxyl surface group and a carboxyl surface group, and a metal oxide precursor, said suspension having a preselected ratio of said polymeric nanostructures to said metal oxide precursor of at least 1:3, said preselected ratio corresponding to a preselected morphology;
b. depositing said suspension onto a substrate;
c. removing said water to form a film;
d. removing said film from said substrate; and
e. annealing said film to volatilize said polymeric nanostructures and convert said metal oxide precursor to at least one metal oxide selected from the group consisting of metal oxide nanoparticles having said preselected morphology and a metal oxide nanosheet comprising conjoined nanoparticles having said preselected morphology.
2. A method in accordance with claim 1 wherein said polymeric nanostructures comprise 0.001% to less than 1% of said suspension and wherein said metal oxide comprises metal oxide nanoparticles having said preselected morphology.
3. A method in accordance with claim 1 wherein said polymeric nanostructures comprise at least 1% of said suspension and wherein said metal oxide comprises a metal oxide nanosheet comprising conjoined nanoparticles having said preselected morphology.
4. A method in accordance with claim 1 wherein said polymeric nanostructures comprise 0.01 to 0.5 weight % of said suspension.
5. A method in accordance with claim 1 wherein said polymeric nanostructures comprise 0.05 to 0.25 weight % of said suspension.
6. A method in accordance with claim 1 wherein said polymeric nanostructures comprise at least one of the group consisting of cellulose nanofibrils and cellulose nanocrystals.
7. A method in accordance with claim 1 wherein said metal oxide precursor comprises at least one metal oxide precursor selected from the group consisting of: an indium-tin-oxide precursor, a zinc oxide precursor, a titanium dioxide precursor, and an iron oxide precursor.
8. A method in accordance with claim 7 wherein said indium-tin-oxide precursor comprises a mixture of indium trichloride and tin (II) chloride.
9. A method in accordance with claim 1 wherein said preselected ratio is in the range of 1:3 to 1:7 and wherein said preselected morphology comprises predominantly nanowires.
10. A method in accordance with claim 1 wherein said preselected ratio is in the range of 1:17 to 1:23 and wherein said preselected morphology comprises predominantly nanorods.
11. A method in accordance with claim 1 wherein said preselected ratio is in the range of 1:27 to 1:33 and wherein said preselected morphology comprises predominantly nanospheres.
12. A method in accordance with claim 1 wherein said preselected ratio is at least 1:70 and wherein said preselected morphology comprises predominantly nanocrystals.
13. A method in accordance with claim 1 wherein said nanocrystals are predominantly octahedral.