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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]

The tannic acid induced assembly strategy was used to synthesize the Ni-doped SnO 2 nanosheets. The fabricated TA-Ni/SnO 2 sensors exhibited superior sensing performance to HCHO at working temperature of 80 °C (R a /R g = 184.3) and excellent sensing selectivity. The experimental and DFT results illustrated that the highly dispersed Ni substitution sites in SnO 2 crystals can be regarded as the active sites, which not only facilitated the generation of surface active O 2 –(ad) species, but also modified the electronic structure of SnO 2 crystals, contributing to superior sensing performance of TA-Ni/SnO 2 to HCHO. [Display omitted] • Tannic acid (TA) induced surface functional strategy is applied to synthesize Ni-doped SnO 2 nanosheets. • Ni ions can be highly dispersed on the SnO 2 nanosheets via TA. • The obtained materials exhibit superior sensing performance to HCHO. • The synergistic effects between O 2 –(ad) species and modified electronic structure contribute to the excellent sensing performance. Surface functionalization is a promising strategy to modulate the electronic and surface properties of metal oxide semiconductors. Here, we report a tannic acid (TA) induced surface functional strategy to synthesize Ni-doped SnO 2 nanosheets. Benefiting from the abundant polyphenolic and catechol groups, the linkage of TA not only exhibit high affinity to various substrate, but also show powerful chelating ability to metal ions. Hence, Ni ions can be highly dispersed on the SnO 2 nanosheets via TA, TA linkage also can prevent the aggregation of Ni ions during pyrolysis, and Ni substitution in SnO 2 crystals can be obtained. As a proof-of-concept demonstration, the TA-Ni/SnO 2 sensor is fabricated to detect HCHO, and exhibit superior sensing performance at low working temperature of 80 °C (R a /R g = 184.3), excellent sensing selectivity and long-term stability. Detail experimental and theoretical calculation demonstrate the highly dispersed Ni substitution active sites facilitate the generation of surface O 2 –(ad) species, and the electronic structure also can be modulated to exhibit high affinity to HCHO, hence, the synergistic effects contribute to the enhanced sensing performance. Our work paves the way for versatile surface functionalization to synthesize advanced materials for application in catalysis and sensing field. [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]

Abstract: ZnO:Ga thin films were deposited by DC magnetron sputtering using two facing Ga-doped ZnO ceramic targets at room temperature. Polyethylene naphthalate (PEN) and Eagle2000 glass were used as substrates. The influence of PEN and glass substrates on the properties of ZnO:Ga thin films has been investigated. The distance between substrate and plasma dependence of micro-structure and electrical properties was also studied. The lowest resistivity obtained was 6.65×10−4 Ωcm with a Hall mobility of 17.1cm2 V−1 s−1 and a carrier concentration of 5.5×1020 cm−3. When those ZnO:Ga thin films were applied to low-temperature flexible a-Si:H solar cells, an initial conversion efficiency of 5.91% was achieved. [Copyright &y& Elsevier]