<p> 1</p><p>Supplementary information</p><p>A nanostructured Cr2O3/WO3 p-n junction sensor for highly sensitive detection of butanone</p><p>Qian Zhang a, Mingkun Xu a, Zhurui Shen a*, Qiang Wei b*</p><p> a Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300350, PR China b Key Laboratory of Composite and Function Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300350, PR China</p><p>*Corresponding authors: Prof. Dr. Zhurui Shen, E-mail: [email protected], Tel: +86 13702014847. Key Laboratory of Advanced Ceramic and Machining Technology, School of Materials Science and Engineering, Tianjin University, Yaguan Road 135, Haihe Education Park, Tianjin 300350, PR China. Prof. Dr. Qiang Wei, E-mail: [email protected], Tel: +86 13212077725. Key Laboratory of Composite and Function Materials, School of Materials Science and Engineering, Tianjin University, Yaguan Road 135, Haihe Education Park, Tianjin 300350, PR China. 2 3</p><p>Fig. S1. Comparation of the standard patterns of monoclinic WO3 (JCPDS No. 72-1465) and Cr2O3 (PDF card No. 38-1479).</p><p>Fig. S2. EDX element mapping of as-synthesized W-Cr-40 sample.</p><p>Fig. S3. EDX spectrum of as-synthesized W-Cr-40 sample. 4</p><p>Fig. S4. The response of WO3 nanosheets and Cr2O3/ WO3 nanocomposite compostion to 100 ppm ethanol from 180 °C to 340 °C. Oxygen adsorption process (1) (2) (3) (4)</p>