In this work, Au@NiO core-shell nanoparticles (C-S NPs) as a p-type gas sensing material was synthesized by a facile wet-chemical method, and evaluated their gas sensing properties as compared to the pristine NiO NPs gas sensors. Transmission electron microscope (TEM) results exhibited the well-dispersed formation of Au@NiO C-S NPs having the total size of 70-120 nm and NiO shells having 30-50 nm thickness. The C-S morphology as well as the overall particle sizes are unchanged even at 500 °C. The gas sensing result reveals that the response of Au@NiO C-S NPs gas sensor is higher than pristine NiO NPs gas sensor for 100 ppm of ethanol at 200 °C operating temperature. The baseline resistance in the air for Au@NiO C-S NPs sensor is lowered as compared to pristine NiO NPs, which is due to the increased number of holes as charge carriers in Au@NiO C-S NPs. The high response of Au@NiO core-shell NPs as compared to pristine NiO NPs is attributed to electronic and chemical sensitization effects of Au. In Au@NiO C-S structure, the contact between metal (Au) and semiconductor (NiO) formed a Schottky junction since Au metal acted as electron acceptor, a withdrawal of electrons from NiO by Au metal core leaved behind number of holes as charge carriers in Au@NiO C-S NPs. Therefore, the baseline resistance of Au@NiO C-S NPs greatly decreased than pristine NiO NPs, as a result the Au@NiO C-S NPs showed higher response. On the other hand, in chemical sensitization effect, Au NPs catalyzed to dissociate O2 molecules into ionic species. This work will give some clue to the researchers for the further development of p-type based C-S NPs sensors.
Bibliographical noteFunding Information:
This work was supported by (1) BK21 plus program from the Ministry of Education and Human Resource Development , (2) National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (BRL No. 2015042417, 2016R1A2B4014090), (3) Business for Academic-industrial Cooperative establishments funded by Korea Small and Medium Business Administration in 2016 (Grant No. C0396231 ), and (4) Centre for University Research Facility (CURF), CBNU, and Korean Basic Science Institute (KBSI), CBNU branch are acknowledged for the analysis of TEM and HR-TEM, respectively.
In-Hwan Lee received his Ph.D. degree in Materials Science and Engineering in 1997 from Korea University in South Korea. During 1997–1999, he was a postdoctoral fellow at Northwestern University. Then, he joined Samsung Advanced Institute of Technology, where he led an epitaxial team and developed InGaN/GaN violet LDs. From 2002 to 2017, he was a professor in Divison of Advanced Materials Engineering at Chonbuk National University in South Korea. With the sabbatical grant from LG foundation, he was at Yale University during 2008–2009. In 2017 March, he joined Department of Materials Engineering, Korea University, Korea as a full professor. His current research focuses on the development of nanotechnology-inspired novel optoelectronic devices including LEDs, photovoltaic devices, and sensors.
© 2018 Elsevier B.V.
- Baseline resistance
- Core-shell NPs
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry