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Highlights • SnO 2 /NaNbO 3 nanocomposite humidity sensor was prepared by hydrothermal synthesis. • SnO 2 /NaNbO 3 had a high surface area because of a micro-sized urchin-like structure. • SnO 2 /NaNbO 3 exhibited remarkable sensitivity much higher than that of pure SnO 2. • SnO 2 /NaNbO 3 showed rapid response and recovery times and excellent selectivity. • SnO 2 /NaNbO 3 sensors have potential applications in the humidity-sensing field. Abstract An urchin-like nano-composite of SnO 2 /NaNbO 3 was fabricated by the hydrothermal method and the influence of the Sn/Nb ratio in the samples on their humidity-sensing properties was investigated. The phases and morphologies of these composites and their elemental distributions were analyzed by X-ray diffraction scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The sensor based on the optimum Sn/Nb ratio of 1:0.4 exhibited remarkable humidity-sensing properties, including a good response (S = 4823.8) that was 8.72 times higher than that of the pure SnO 2 sensor (S = 553.01). The composites showed rapid response and recovery times (3/9 s), as well as good stability, linearity, and excellent selectivity. The fabrication and humidity-sensing mechanisms were systematically analyzed using analog computations and Nyquist diagrams, respectively. Compared with pure NaNbO 3 and SnO 2 sensors, our easily prepared SnO 2 /NaNbO 3 sensor demonstrates good sensing properties and holds great promise for use in humidity-sensing applications. [ABSTRACT FROM AUTHOR]

Graphical abstract One dimensional Au nanoparticles-functionalized magnetic N-doped carbon nanotubes have been fabricated, which was employed as a novel matrix for enzyme immobilization to develop highly sensitive biosensors. Highlights • A convenient and efficient method was developed to prepare magnetic NCNTs@Fe 3 O 4 supported Au NPs. • One-dimensional NCNTs@Fe 3 O 4 @Au composite was exploited as a biosensing scaffold to entrap cyt c. • The magnetic NCNTs@Fe 3 O 4 @Au based sensor could avoid the modification on the electrode and realize the direct detection in the solution. • The resultant biosensors displayed good performance for the detection of H 2 O 2 with a low detection limit of 0.3 μM. Abstract In recent years, the fabrication of noble metal functionalized magnetic carbon nanotubes for a variety of novel biosensors has aroused considerable interest owing to their synergistic improved sensitivity. In the paper, the Fe 3 O 4 and Cu nanoparticles (NPs) were integrated into the NCNTs to obtain N-doped carbon@Fe 3 O 4 -Cu nanotubes (NCNTs@Fe 3 O 4 @Cu) through a one-pot high temperature decomposition procedure. Then, Au NPs were assembled on the magnetic NCNTs to obtain NCNTs@Fe 3 O 4 @Au composite by galvanic replacement with Cu NPs. The resultant composite had provided a friendly platform for enzyme immobilization to develop highly sensitive biosensors. After the cytochrome c(cyt c) was accumulated by NCNTs@Fe 3 O 4 @Au composite, the cyt c/NCNTs@Fe 3 O 4 @Au gathered to the surface of electrode with an external magnet. Thus, the sensitivity of designed biosensor could be further improved, and most of electrochemical interferences could be excluded. Benefiting from the unique hybrid structure of the composite, the direct electron transfer of cyt c was highly facilitated and the constructed biosensors exhibited good performance for the detection of H 2 O 2 with an extraordinary low detection limit of 0.3 μM, which revealed potential application for fabricating novel electrochemical biosensors. [ABSTRACT FROM AUTHOR]

• SnO 2 /MoS 2 nanocomposite ammonia sensor was prepared by hydrothermal synthesis. • SnO 2 /MoS 2 had a flower-like structure with SnO 2 nanocrystals decorated on MoS 2 nanosheets. • SnO 2 /MoS 2 exhibited remarkable sensitivity much higher than that of pure MoS 2. • SnO 2 /MoS 2 showed rapid response and recovery times and excellent selectivity. • SnO 2 /MoS 2 sensors have potential applications in the NH 3 gas-sensing field. In this work, MoS 2 nanosheets decorated with SnO 2 nanoparticles were prepared via a facile two-step hydrothermal method, which possesses a proposed sensing composite structure of supporting layer/sensitive dots. The SnO 2 /MoS 2 nanocomposites exhibited an excellent sensing response (2080.36) toward 200 ppm NH 3 , which was ∼27.5 times higher than that of pristine MoS 2 films, a fast response/recovery time (23/1.6 s) toward 50 ppm at room temperature (22℃), and outstanding selectivity to NH 3 against CH 4 , H 2 , CO, H 2 S, and NO 2 and good repeatability. The excellent gas sensing properties could be dominated by the unique thin layers assembled flower-like structures of 2D MoS 2 , which foster the carrier charge transfer process and the reaction to SnO 2 /MoS 2 and NH 3. These results present the SnO 2 /MoS 2 nanocomposites promising candidate materials for high-performance NH 3 gas sensing at room temperature. [ABSTRACT FROM AUTHOR]

• SnO 2 /DE nanocomposite was prepared by hydrothermal synthesis. • SnO 2 /DE had a high surface area because of a micro-sized embedded structure. • SnO 2 /DE exhibited remarkable sensitivity much higher than that of pure DE. • SnO 2 /DE showed rapid response and recovery times, excellent water adsorption and desorption properties. • SnO 2 /DE sensors have potential applications in the humidity sensing and controllable field. A tin oxide/diatomaceous earth (DE) composite was synthesized via the hydrothermal method without using a template or surfactant, and its humidity-sensing and controlling properties were investigated. The SnO 2 /DE composites have a special embedded structure, in which SnO 2 nanoparticles are embedded in the DE porous frame. The optimal composites exhibit short response and recovery times (T = 3 and 8 s, respectively), and their response (S = 35.64) is 11.88 times higher than that of DE (S = 3). Furthermore, the optimal composite C-1:3 was tested to determine its humidity-controlling properties, which revealed that it possessed absorption (27 h, 12.04%) and desorption (5 h, 8.56%) characteristics. Regarding the selectivity, the C-1:3 sensor showed better sensing behavior to humidity than to NO 2 , NH 3 and other gases. These beneficial properties of the composites are due to a honeycomb structure that endows the composite with a large specific surface area for adsorption of H 2 O molecules and allows charge transfer between the embedded SnO 2 nanoparticles. The humidity-sensing mechanism is explained in detail by the Grotthuss proton transfer theory and density functional theory (DFT), which were used together with a Nyquist diagram to analyze the conditions of H 2 O adsorption. This study demonstrates a novel strategy for designing a material that can rapidly sense and control humidity and provides insights into the application of the composite in sensing and controlling environmental humidity at room temperature. [ABSTRACT FROM AUTHOR]