The effect of the atmosphere on the optical properties of as-synthesized colloidal indium tin oxide.
The optical properties of indium tin oxide (ITO) have often been explored when it is in the form of deposited thin films. In this study, a colloidal chemistry approach is taken to investigate the influence of the atmosphere on the optical properties of ITO nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), absorption spectroscopy and photoluminescence (PL) were used to characterize colloidal ITO samples, synthesized under aerated and inert conditions, with the same composition. In both cases, the ITO can be completely dispersed in a non-polar solvent without any evidence of agglomeration. For the ITO made in air, the nanoparticle-solvent solution exhibits a pale green color, and XRD and TEM indicate an average particle size of approximately 7 nm and small shrinkage in the lattice structure. When the ITO is synthesized under inert conditions, the solution turns blue, and XRD and TEM indicate an average particle size of approximately 8 nm and even less strain in the lattice than for the ITO synthesized under aerated conditions. The change in color and lattice strain is attributed to the difference in oxygen vacancy concentration for the ITO nanoparticles synthesized under aerated and inert conditions, which exhibit different optical band gap values of 3.89 eV and 4.05 eV, respectively. Our work here shows that thin film deposition or sintering steps may not be required for studying the optical properties of as-synthesized ITO nanoparticles.
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA.
Charles J
CJ
Capozzi
Ilia N
IN
Ivanov
Salil
S
Joshi
Rosario A
RA
Gerhardt