**4. Conclusions**

In summary, the flower-like CeO2-doped SnO2 nanostructures were successfully synthesized by a facile one-step hydrothermal synthesis reaction using Na3C6H5O7·2H2O as stabilizer, SnCl2·2H2O

and Ce(NO3)3·6H2O as precursors. Various characterizations indicate that flower-like SnO2 is a rutile structure with high crystallinity and CeO2 well modified the surface of the flower-like SnO2. The response of 5 wt.% CeO2-SnO2 sensor to 200 ppm TEA at the optimal working temperature of 310 ◦C is 252.2, which is about 3.8 times higher than that of undoped one. Moreover, SC-5 sensor displayed better selectivity for triethylamine. The improved gas-sensing performances of the composite were explained possibly due to the formation of n-n heterojunctions between CeO2 and SnO2 and the presence of Ce4+/Ce3+ species in SnO2 facilitates the interaction of electrons. Therefore, the CeO2-doped SnO2 sensors can be an ideal candidate for the detection of triethylamine gas.

**Author Contributions:** D.X. conceived and designed the experiments; J.C. performed the experiments; Y.W. and Z.Z. provided the concept of this research and managed the writing process as the corresponding authors.

**Funding:** This work was funded by the National Natural Science Foundation of China (U1704255), Program for Science & Technology Innovation Talents in Universities of Henan Province (19HASTIT042), the Fundamental Research Funds for the Universities of Henan Province (NSFRF170201, NSFRF1606, NSFRF1614), the Research Foundation for Youth Scholars of Higher Education of Henan Province (2017GGJS053) and Program for Innovative Research Team of Henan Polytechnic University (T2018-2).

**Conflicts of Interest:** The authors declare no conflict of interest.
