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The huge challenge for detection of formaldehyde (HCHO), a toxic volatile organic compound for human health, with ppb level at low working temperature lies in the activation of surface oxygen species of sensing materials. Herein, we have designed in-plane SnO 2 -Sn 3 O 4 heterojunctions with hierarchical nanoflower morphology for efficient HCHO sensing, and the lattice strains, surface properties as well as the electronic structure around the SnO 2 -Sn 3 O 4 phase boundaries can be finely optimized. Notably, lattice strain and Schottky junction dual regulation ensures the in-plane SnO 2 -Sn 3 O 4 heterojunctions with excellent HCHO sensing performance at low working temperature of 120 °C. Particularly, Sn 3 O 4 –400 displays high sensing response (R a /R g = 621.83, 50 ppm), high repeatability and excellent selectivity to HCHO. Furthermore, geometric phase analysis, multiple structural analysis and DFT calculations demonstrate the lattice strain and Schottky junction dual regulation tunes the surface oxygen properties and electron structure, which facilitate the formation of rich surface O−(ad) species and enhance the interaction between materials and HCHO around the abundant SnO 2 -Sn 3 O 4 phase boundaries, thus enhancing the HCHO sensing performance. This research provides novel ideas for selecting high-tech sensing materials for the detection of dangerous volatile organic chemicals. We have designed in-plane SnO 2 -Sn 3 O 4 heterojunctions with hierarchical nanoflower morphology for efficient HCHO sensing, which is a harmful VOCs for human healthy. The Sn 3 O 4 –400 sensors exhibited high sensing response (Ra/Rg = 637.94, 50 ppm), high repeatability and excellent selectivity to HCHO. Both the lattice strain and Schottky junction dual regulation tunes the electron density and surface oxygen properties of in-plane SnO 2 -Sn 3 O 4 heterojunctions, and contributed to the excellent HCHO sensing performance. [Display omitted] • In-plane SnO 2 -Sn 3 O 4 with finely modulation of active sites is constructed. • Gas sensor is fabricated to detect HCHO, a harmful VOC. • The sensor exhibits high response and selectivity at low temperature. • Lattice strain and Schottky junction dual regulation improve sensing performance. [ABSTRACT FROM AUTHOR]

We have designed hollow Co 3 O 4 /ZnO nanocage by MOFs derived method for detection of H 2 S, which seriously threatens human health. The Co 3 O 4 /ZnO-1 sensor exhibit superior sensing response (R a /R g = 546.2) to 5 ppm H 2 S at 110 °C, which is 32 folds than ZnO sensors with low detection limit (9 ppb), fast recovery (35 s) and high selectivity. Both theoretical and experimental results illustrate the enhanced sensing performance can be attributed to the Co sites induced synergistic effect. [Display omitted] • The hollow Co 3 O 4 /ZnO nanocages have been successfully synthesized. • The state of Co sites in Co 3 O 4 /ZnO can be finely tuned. • The sensor exhibits high response and selectivity at low temperature. • Co sites induced synergistic effect improve sensing performance. Metal organic frameworks (MOFs) derived Co 3 O 4 /ZnO heterostructure has been widely investigated to achieve the high sensing performance. However, the synergistic effects generated from the Co sites and the relationship between the surface structure and sensing performance is still ambiguous. Herein, the hollow Co 3 O 4 /ZnO nanocage heterojunctions have been successfully synthesized, and the state of Co sites can be modulated by finely tuning the coordination environment of Co species. Notably, the Co 3 O 4 /ZnO-1 materials exhibit superior sensing response (R a /R g = 546.2, 32 folds than ZnO sensors) to 5 ppm H 2 S at 110 °C, with low detection limit (9 ppb), fast recovery (35 s) and high selectivity. Detail structural analysis illustrates O 2 can be easily activated around the Co 3 O 4 /ZnO hetero-interface, and the formation of O− species with high mobility improves the surface reaction rate. Additionally, the catalytic reaction between highly dispersed Co species and H 2 S also facilitates the formation of CoS, which can synergistically enlarge the sensing response of sensors. Our work illustrates the state of Co species can greatly affect the sensing performance and pave the way for design of high performance sensing materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual functionalized Ni substitution in shuttle-like In 2 O 3 nanoparticles (NPs) has been synthesized. • The 2 wt% Ni-doped In 2 O 3 NPs exhibit high sensitivity (R a /R g = 2569.42 towards 50 ppm NH 3 at 140 °C), achieving 34 folds improvement compared with pristine In 2 O 3 NPs. • Ni substitution in rh-In 2 O 3 NPs can effectively modulate the electronic structure and surface acidity of material and further improve the adsorption of NH 3. • The substitution of Ni in rh-In 2 O 3 phase and surface O−(ad) species neighboring the substitution sites are recognized as the active sites. Hetero-atom doping is an effective way to improve the sensing performance of metal oxide semiconductor gas sensors. However, the synergistic effects generated from hetero-atom substitution in In 2 O 3 lattice and the relationship between the fine surface structure and sensing performance is still ambiguous. Here, Ni substitution in shuttle-like In 2 O 3 nanoparticles have been successfully synthesized, and the materials are fabricated as gas sensor to detect ammonia, which is a toxic molecule that is harmful for human healthy. We find the 2 wt% Ni-doped In 2 O 3 NPs exhibit high sensitivity (R a /R g = 2569.42 towards 50 ppm NH 3 at 140 °C), achieving 34 folds improvement compared with pristine In 2 O 3 NPs. The sensor also shows good long-term stability, high selectivity and fast response/recovery (23/10 s). Detail structural analysis illustrate the substitution of Ni in rh-In 2 O 3 phase and surface O−(ad) species neighboring the substitution sites are recognized as the active sites, and the reactive oxygen species and surface Bronster acidity can be dramatically enhanced after Ni modification, which contribute to the improvement of sensing performance. Our work illustrate the synergistic effects of hetero-atom doping on the sensing performance and pave the way for design of high performance sensing materials. [ABSTRACT FROM AUTHOR]