Supplementary Material Chemiresistive hydrogen gas sensors from gold-palladium nanopeapods Chung Hee Moon1, Nosang V. Myung2, Elaine D. Haberer1,3 1 Materials Science and Engineering Program University of California, Riverside, CA 92521 (USA) 2 Department of Chemical and Environmental Engineering University of California, Riverside, CA 92521 (USA) 3 Department of Electrical and Computer Engineering University of California, Riverside, CA 92521 (USA) Fig. S1. Energy dispersive spectroscopy spectrum of thick Au-Pd nanopeapods. Au and Pd were present in addition to Si and O from the substrate and Ag from the silver paste for grounding. Fig. S2 (a) Scanning electron microscopy image and (b-d) energy dispersive spectroscopy elemental mapping of thick Au-Pd nanopeapods with an average diameter of 50 ± 11 nm on a Si/SiO2 substrate. SEM image is overlapped with elemental mapping of (b) both Au and Pd, (c) Au only, and (c) Pd only. Yellow and magenta are used to indicate the presence of Au and Pd, respectively. Fig. S3. Energy dispersive spectroscopy spectrum of thin Au-Pd nanopeapods. Au and Pd were present in addition to Si and O from the substrate and Ag from the silver paste for grounding. Fig. S4. (a) Scanning electron microscopy image and (b-d) energy dispersive spectroscopy elemental mapping of thin Au-Pd nanopeapods with an average diameter of 29 ± 8 nm on a Si/SiO2 substrate. SEM image is overlapped with elemental mapping of (b) both Au and Pd, (c) Au only, and (c) Pd only. Yellow and magenta are used to indicate the presence of Au and Pd, respectively.