| AVS 63rd International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Monday Sessions |
| Session NS-MoA |
| Session: | Nanophotonics, Plasmonics, and Energy |
| Presenter: | Karthik Shankar, University of Alberta and The National Institute for Nanotechnology, Canada |
| Authors: | K. Shankar, University of Alberta and The National Institute for Nanotechnology, Canada M.H. Zarifi, University of Alberta, Canada S. Farsinezhad, University of Alberta, Canada M. Daneshmand, University of Alberta, Canada |
| Correspondent: | Click to Email |
Nanostructures made of semiconducting metal oxides such as TiO2, ZnO, SnO2, WO3, etc. have a remarkably versatile application spectrum, serving applications in sensing, catalysis, photocatalysis and solar cells. Metal oxide nanostructures abound in electronic defects originating in their high surface area and the method of fabrication. Such defects include dangling bonds, grain boundaries and color centers which in turn may act as shallow or deep trapping sites for electrons and/or holes. These defects have been more or less uniformly been viewed negatively in the literature for their deleterious effects on light harvesting and charge transport. However, a recently emerging view is that the defects also provide an opportunity to engineer sensitivity and much-needed selectivity in sensor designs, particularly with regards to the detection and quantification of small molecules.
We used highly ordered TiO2 nanotube arrays (TNA) grown by low-cost electrochemical anodization as platforms to perform the selective sensing of alcohols without the use of external binding receptors. TNA membranes were placed in the active coupling gap of a microwave ring-type resonator [1]. By monitoring the resonator's Quality factor (Q) and resonance frequency (f0) as a function of time following light illumination of the nanotube membrane, we were able to distinguish between the methanol, ethanol and isopropanol [2].
Our work also brings in focus a hitherto underexplored topic in nanomaterials - namely the leveraging of the interactions of microwaves and semiconductor nanostructures to build better sensors and diagnostic platforms [2]. Extension of this concept enabled us to detect a molecular monolayer by monitoring the interactions of microwaves with semiconductors, and also enabled us to use the molecular monolayer to tune the electronic interactions of the surface of wide bandgap TiO2 with external analytes in the service of VOC sensing as well as extremely low-level photodetection.
REFERENCES
1. Zarifi MH, Mohammadpour A, Farsinezhad S, Wiltshire BD, Nosrati M, Askar AM, Daneshmand M and Shankar K, TRMC Using Planar Microwave Resonators: Application to the Study of Long-lived Charge Pairs in Photoexcited Titania Nanotube Arrays, Journal of Physical Chemistry C, 119 (25), 14358-14365, 2015.
2. Zarifi MH, Farsinezhad S, Abdolrazzaghi M, Daneshmand M and Shankar K, Selective microwave sensors exploiting the interaction of analytes with trap states in TiO2 nanotube arrays, Nanoscale, DOI: 10.1039/c5nr06567d, 2016.