56. B. Y. Kim, J. S. Cho, J. W. Yoon, C. W. Na, C. S. Lee, J. H. Ahn, Y. C. Kang, J. H. Lee, Extremely sensitive ethanol sensor using Pt-doped SnO2 hollow nanospheres prepared by Kirkendall diffusion, Sensors and Actuators B: Chemical, 234(2016)353-360