Cupric Oxide Nanowires Formed on Single-walled Carbon
Nanotube Substrate: Synthesis and Gas Sensing Properties
Nguyen Duc Hoa, Nguyen Van Quy, Yousuk Cho, Dojin Kim*
i
Department of Materials Science and Engineering, Chungnam National University, Daejeon,
305-764 Republic of Korea
Among the metal oxides used for gas sensors application, researchers have focused on
improving the gas sensing performance of n-type semiconductor. Contrary to other n-type
semiconductor metal oxides, cupric oxide (CuO) is a p-type semiconductor with band gap energy
of ~1.7 eV and reported to be suitable for catalysis, lithium-copper oxide electrochemical cells,
and gas sensors applications. The nanoparticles, plates and nanowires of CuO were found to
respond to NO2, H2S and CO gases. The nanowire of CuO can be synthesized by low temperature
solid-phase process, heating copper substrates in air, and template-assisted electrodeposition
methods. The cuprous oxide nanoparticles could also be coated on multi-walled carbon
nanotubes (MWNTs) by chemical method. However, the gas sensing properties of CuO
nanowire structure deposited on carbon nanotubes have not been reported yet.
In this work, we report about the synthesis, characterization and gas sensors application
of nanowire structured CuO deposited on single-walled carbon nanotubes (SWNTs). The
nanowire structured CuO is synthesized by deposition of metal Cu layer on a porous thin film of
SWNTs substrate flowed by thermal oxidation. The oxidation process is performed in air and the
SWNTs substrate was removed during the oxidation process. The nanostructure and electrical
properties of synthesized materials are investigated by SEM, TEM, XRD, Raman, XPS
spectroscopy and electrical property measurements
The SEM, TEM, XRD and Raman spectroscopy data indicated that nanowires structured CuO
was successfully synthesized. The nanowires CuO have a diameter of 25 nm with the length up
to several micrometers. The electrical and gas sensing properties of nanowires structured CuO
was tested with H2 gas at temperature of 250 oC. Gas sensing properties of synthesized
nanostructured materials showed very high sensing to hydrogen with fast and reversible response
at operating temperature of 250 oC. The nanowires CuO oxidized at 400 oC showed the highest
sensitivity. The oxidation temperature effects on morphology, quality, and gas sensing properties
of CuO are investigated and discussed.
We have developed a simple method to synthesized nanowires structured CuO by
deposition Cu on SWNTs substrate followed by oxidation process. The nanowire structured
materials showed a very high sensitivity and could detect the concentration of H2 down to ppm
level.
*
E-mail: dojin@cnu.ac.kr