Porous, 3D-hierarchical α-NiMoO4 rectangular nanosheets for selective conductometric ethanol gas sensors

Metal Organic Framework-Derived ZnO@GC Nanoarchitecture as an Effective Hydrogen Gas Sensor with Improved Selectivity and Gas Response

“…Terraces of the microcube-like polyhedrons also have appeared to be less agglomerated when compared with the ZnO@GC-550 sample; this might be attributed to the better grain refinement of the samples at elevated temperatures. 29 These observations are well supported by the HR-TEM measurement. Accordingly, the ZnO@GC-750 has been carefully chosen for further HR-TEM analysis, and the resultant images are displayed in Figure 1e−j.…”

“…Furthermore, the ZnO@GC-650 and ZnO@GC-750 samples have shown well-resolved microcube morphologies. Terraces of the microcube-like polyhedrons also have appeared to be less agglomerated when compared with the ZnO@GC-550 sample; this might be attributed to the better grain refinement of the samples at elevated temperatures . These observations are well supported by the HR-TEM measurement.…”

Current Trends in Nanomaterials for Metal Oxide-Based Conductometric Gas Sensors: Advantages and Limitations—Part 2: Porous 2D Nanomaterials

“…In addition, it should be kept in mind that, in most cases, the formation of porous metal oxide 2D nanostructures requires annealing at temperatures of 300–500 °C at the final stage to transfer hydroxyls to the metal oxide phase [ 79 , 81 , 85 , 86 ]. For example, Ryu et al [ 87 ] synthesized ZnO nanosheets by the hydrothermal method and found that the nanosheets became highly porous only after calcination at 350 °C for 5 h. This means that the formation of pores in such structures often occurs according to the mechanism corresponding to the phase-transition method.…”

“…For example, Ryu et al [ 87 ] synthesized ZnO nanosheets by the hydrothermal method and found that the nanosheets became highly porous only after calcination at 350 °C for 5 h. This means that the formation of pores in such structures often occurs according to the mechanism corresponding to the phase-transition method. For example, Sharma et al [ 86 ] showed that the formation of porous NiMoO 4 nanosheets requires annealing at 400 °C in the presence of air, during which there is a transition from NiMoO 4 ·xH 2 O, which has a 3D honeycomb structure, to NiMoO 4 porous nanosheets, which have 3D rectangular structures. When using other synthetic methods, such as sol-gel [ 88 ], electrodeposition [ 89 ], chemical bath deposition [ 90 ], and wet chemical method [ 91 ], designed for the synthesis of ZnO, WO 3 , SnO 2 , Co 3 O 4 , In 2 O 3 , NiMoO 4 , CeO 2, and other metal oxide-based porous 2D structures, post-processing high-temperature annealing is also generally required.…”

Structural formation of multifunctional NiMoO4 nanorods for thermoelectric applications

“…4 For CoMoO 4 , the Seebeck value is 0.4 to 1 mV K −1 between 300 and 1000 K and the electrical conductivity is 0.4712 S cm −1 to 0.9030 S cm −1 between 300 K and 1000 K. 5 The Seebeck value of MnMoO 4 is −250 μV K −1 to −10 μV K −1 between 300 K and 700 K and 120 μV K −1 to 5 μV K −1 between 700 K and 1000 K, and the electrical conductivity is 0.079 S cm −1 to 0.9030 S cm −1 between 300 K and 1000 K. 6 Among them, NiMoO 4 can be used for various crucial applications such as supercapacitors, 7 photocatalysts, 8 oxygen evolution 9 and sensors. 10 Monoclinic NiMoO 4 forms with a very high percentage of the α-NiMoO 4 phase at temperatures below 500 °C, and above 500 °C to 670 °C, the material forms with a very high percentage of the β-NiMoO 4 phase. α-NiMoO 4 exhibits the octahedral coordination of Mo 6+ ions with edge shared oxygen and β-NiMoO 4 exhibits the tetrahedral coordination of Mo 6+ ions with edge shared oxygen.…”