Search

Recently, spinel cobalt oxide (Co 3 O 4 ) structure has been widely investigated due to its excellent sensitivity towards various noxious gases and good response/recovery speed at low concentration. In this work, we designed and synthesized two kinds of different Co 3 O 4 micro-structure (cube and octahedron) with a similar size. After fabricating them into gas sensors, we found that the crystal plane structure of Co 3 O 4 has an important effect on its gas sensing performance. Furthermore, the {111} planes of Co 3 O 4 may be more sensitive than {100} planes to various testing gases. Co 3 O 4 octahedrons micro-structure exhibits an excellent sensitivity (about 12.6), good response/recovery speed and cycling stability (no decline even after 2 days) under 50 ppm ethanol gases at working temperature of 200 °C. As such, thisCo 3 O 4 octahedrons micro-structure is a promising candidate for a high-performance gas sensing material. [ABSTRACT FROM AUTHOR]

The NiO nanoflowers were prepared by a facile surfactant assisted hydrothermal method using Ni(NO 3 ) 2 –6H 2 O or NiCl 2 –6H 2 O as precursor compound. The microstructure of the samples was characterized by SEM and XRD. The gas sensing properties of the NiO nanoflowers toward ethanol was also investigated. The results show that surfactant plays a key role in the synthesis of flower-like NiO. The NiO nanoflowers show excellent sensing performances to ethanol gas. This morphology holds substantial promise for applying NiO as a potential gas sensing material for future sensor application. [ABSTRACT FROM AUTHOR]

Cu 2 O microspheres with hollow and solid features were successfully prepared via a convenient liquid phase reducing method. Interestingly, we found that the discrepancy in morphology arose from a simply changing on the adding sequence of aqueous sodium dodecyl sulfate (SDS) and CuCl 2 with other conditions unchanged. Based on experimental results, the feasible formation mechanisms of both morphologies were deduced, where the relative concentration of SDS and CuCl 2 was a crucial factor that effect the resultant morphologies. In comparison with the solid microspheres, the hollow Cu 2 O exhibited superior gas sensing performance. The significant performance might ascribe to its unique hollow structure, contributing to plenty of active sites existed on both the inner and outer surface and unrestricted gas diffusion in the hollow microspheres. In this work, hollow and solid cuprous oxide microspheres were successfully synthesized by liquid phase reducing method and the gas sensing performance of the samples was investigated. In addition, we also explore the effect of the adding sequence of aqueous sodium dodecyl sulfate (SDS) and CuCl 2 on the resultant morphologies of Cu 2 O and propose the growth formation mechanism. Image 1 • Cu 2 O microspheres with hollow and solid features were successfully prepared. • The hollow structure exhibited superior gas sensing performance than the solid microspheres. • The adding sequence played a vital role on the morphology of materials. [ABSTRACT FROM AUTHOR]

Monoclinic scheelite BiVO 4 nanoplates have been prepared via a facile hydrothermal method with monoethanolamine as a surfactant. The obtained BiVO 4 nanoplates were characterized by XRD, SEM, Raman microscope and N 2 adsorption-desorption analysis. The BiVO 4 prepared with MEA is monoclinic scheelite plates which is composed of nanocrystallite with the average size of 100 nm. The sensors based on BiVO 4 nanoplates show good sensitivity to alcohols gases, especially to n-butanol. The sensitivity to 100 ppm n-butanol gas is 61.6 at 260 °C, and the sensors exhibit low sensitivity to xylene, formaldehyde and toluene. The BiVO 4 nanoplates could be a promising candidate for high selectivity and high sensitivity n-butanol gas-sening materials. [ABSTRACT FROM AUTHOR]

In this work, gas-sensing materials based on Co 3 O 4 /Fe 2 O 3 nanocubes were prepared via a MOF hybrid-assisted approach with the aid of ion-exchange. Structural characterizations proved the as-prepared Co 3 O 4 /Fe 2 O 3 nanocubes possessed hollow porous structures. The formation mechanisms were also investigated. Gas-sensing measurements revealed that the Co 3 O 4 /Fe 2 O 3 nanocubes showed high response (R g /R a = 3.27) towards acetone, which was 3.06 times higher than that of Co 3 O 4 nanocubes (R g /R a = 1.07). The enhanced sensing mechanism of Co 3 O 4 /Fe 2 O 3 nanocubes were also discussed, which could be explained by synergistic effects aroused by the as-formed p-n heterojunctions and hollow porous structures that offered numerous diffusion channels and an additional modulation in resistance. Our studies shed a new light to design p-n naoncomposites by a facile MOF hybrid-assisted method. Moreover, the as-designed Co 3 O 4 /Fe 2 O 3 nanocubes have potential application for fabricating high performance acetone sensors. • A novel Co 3 O 4 /Fe 2 O 3 nanocubes were successfully prepared via a MOF hybrid-assisted approach. • Co 3 O 4 /Fe 2 O 3 nanocubes have potential application for fabricating high performance acetone sensors. • Our studies shed a new light to design arrays in-situ on sensor devices by a facile method. [ABSTRACT FROM AUTHOR]

In this work, novel n-type heterostructures of ZnSnO 3 modified p-type Co 3 O 4 (Co 3 O 4 –ZnSnO 3) nanowire arrays were fabricated in-situ on flat alumina substrates via a simple hydrothermal method without seed layers. SEM and TEM characterizations revealed that the Co 3 O 4 nanowire arrays were fully covered by ZnSnO 3 nanosheets. The gas-sensing measurement revealed that the Co 3 O 4 –ZnSnO 3 composite arrays showed the highest response 5.57 (R g /R a) towards ethanol, which was 2.04 times higher than that of Co 3 O 4 nanowire arrays (R g /R a = 2.73). Meanwhile, the enhanced sensing mechanism of Co 3 O 4 –ZnSnO 3 composite arrays was also discussed, which could be explained by the special heterojunction structure arrays that offered an additional modulation in resistance. Our studies shed a new light to design p-n heterostructure arrays in-situ sensing device by a facile method. Moreover, the as-designed Co 3 O 4 –ZnSnO 3 composite arrays have potential application for fabricating high performance ethanol sensors. • Co 3 O 4 –ZnSnO 3 arrays were fabricated in-situ on alumina substrates without seed layers. • The Co 3 O 4 –ZnSnO 3 arrays showed the highest response towards ethanol than pristine Co 3 O 4. • The enhanced gas-sensing mechanism was ascribed to the p-n heterojunction structures. [ABSTRACT FROM AUTHOR]