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The emerging in-plane heterostructures exhibit unique structure properties, attracting considerable attention in the gas sensors. However, the insight of the structure difference between in-plane and out-plane heterojunctions as well as the structure-activity relationship are still ambiguous. Herein, a novel in-plane ZnFe 2 O 4 /ZnO heterojunction (ZnFe 2 O 4 /ZnO-1) is designed for the efficient detection of triethylamine, which exhibits superior sensing performance with high selectivity and fast response/recovery, and the sensing response (R a /R g =424.07, 50 ppm) is 3.66 folds higher than the out-plane ZnFe 2 O 4 /ZnO heterojunction (ZnFe 2 O 4 /ZnO-2). Moreover, multiple structure analysis and DFT calculations reveal numerous grain boundaries form in ZnFe 2 O 4 /ZnO-1, and the lattice strain, d -band electronic structure, surface oxygen species as well as the surface acidity exhibit great difference with ZnFe 2 O 4 /ZnO-2. Notably, the formation of in-plane heterojunctions facilitates the generation of abundant surface O 2 - (ad) species and large amounts of Lewis acid sites, as well as the upshift of d -band center, which contributes to the enhanced triethylamine sensing performance. Our work illustrates the structure-activity relationship between in-plane and out-plane heterojunctions, and paves the way for the design of novel heterostructure for detecting harmful volatile organic compounds. • The in-plane ZnFe 2 O 4 /ZnO heterostructures have been successfully synthesized. • The in-plane material exhibits superior sensing performance to TEA at 120 °C. • The structural differences between in-plane and out-plane are investigated. • The structure-activity relationship of ZnFe 2 O 4 /ZnO-1 to TEA sensing is illustrated. • The surface O 2 -(ad) species, Lewis acid and the upshift of d -band center contribute to the sensing performance. [ABSTRACT FROM AUTHOR]

The local environment of active sites and the number of oxygen vacancies can greatly affect the reactivity of semiconductor metal oxides (SMOs). However, rare work has been reported to investigate the relationship between the state of oxygen vacancies and sensing performance of SMOs. Herein, a series of porous CeO 2 -SnO 2 hetero-structure nanosheets with fine modulation of the local environment active sites and oxygen defect activity have been successfully constructed. We have investigated their sensing performance towards 3-hydroxy-2-butanone, which is a biomarker of food pathogenic microbe Listeria monocytogenes. We found that the amount of asymmetric Ce-O-Sn sites rather than total oxygen vacancies amount of CeO 2 /SnO 2 materials can greatly affect their sensing performance. Impressively, the porous CeO 2 /SnO 2 -400 nanosheets, which possessed abundant active O-(ad) species originated from the asymmetric Ce-O-Sn sites, exhibited high sensitivity (R a /R g =637.94 to 50 ppm), fast response (29 s) and recovery (172 s), excellent selectivity and high stability toward 3-hydroxy-2-butanone at a working temperature of 160 °C. Both the surface O-(ad) species associated with the asymmetric oxygen sites and porous nanosheet hetero-structure contribute to the enhanced gas adsorption and diffusion process, further boosting their sensing performance. Our work provides new sights for identification of active sites in sensing materials as well as paves the way for detection of pathogenic microbes in food. [Display omitted] • Porous CeO 2 -SnO 2 nanosheets with finely modulation of active sites is constructed. • Gas sensor is fabricated to detect 3-hydroxy-2-butanone, a biomarker of microorganisms. • The sensor exhibits high sensitivity, selectivity, fast response and recovery rate. • Asymmetric Ce-O-Sn site is recognized as active site to improve sensing performance. [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]