The ZnO NWs were grown on carbon fibers and
paper substrates using a two-step hydrothermal
growth approach [20]. Firstly, a ZnO seed layer film
was coated on surface of substrates. Then the
seeded substrates were placed in an aqueous
solution to grow ZnO NWs. The seed layers
fabricated on two kinds of substrate are also by
coating and thermally decomposing. The carbon
fibers and papers were cleaned ultrasonically in
acetone, ethanol and deionized water. The carbon
fibers were immersed in the seed solution of 0.05 M
zinc acetate in ethanol for 2 min and pulled up.
Then ZnO seeds were deposited on carbon fibers by
thermally decomposing zinc acetate at 350 ℃ for
15 min in air [21]. This step was repeated 3~4 times
and the carbon fiber was completely covered by
ZnO seed layer. For the fabrication of seed layer on
papers, paper substrate was immersed in the seed
solution (0.08 M zinc acetate in ethanol) and the
solution spread across paper [18]. Then the paper
was dried completely for 10 minutes at 100 ℃in air.
This step was repeated 5~6 times to ensure
complete coverage of the paper fibers with a ZnO
seed layer. Finally, the paper was annealed at
160 ℃ for 6 h in air, which made zinc acetate
convert to the ZnO completely.