Design of α-Fe2O3 nanorods functionalized tubular NiO nanostructure for discriminating toluene molecules

Abstract

A novel tubular NiO nanostructure was synthesized by a facile and low-cost hydrothermal strategy and then further functionalized by decorating α-Fe2O3 nanorods. The images of electron microscopy indicated that the α-Fe2O3 nanorods were assembled epitaxially on the surfaces of NiO nanotubes to form α-Fe2O3/NiO nanotubes. As a proof-of-concept demonstration of the function, gas sensing devices were fabricated from as-prepared α-Fe2O3/NiO nanotubes, and showed enhanced gas response and excellent selectivity toward toluene, giving a response of 8.8 to 5 ppm target gas, which was about 7.8 times higher than that of pure NiO nanotubes at 275 °C. The improved gas sensing performance of α-Fe2O3/NiO nanotubes could be attributed to the unique tubular morphology features, p-n heterojunctions and the synergetic behavior of α-Fe2O3 and NiO.

Synergetically Selective Toluene Sensing in Hematite‐Decorated Nickel Oxide Nanocorals

“…Polar plot for responses of a) bare NiO nanorods and b) α‐Fe 2 O 3 ‐decorated NiO nanocorals to various gases (5 ppm for NO 2 and 50 ppm for other gases) at 350 °C. c) Response ratio of various nanostructures based on NiO and α‐Fe 2 O 3 to several gases, as reported in the literature and the present study.…”

“…Multiple‐step GAD was already found in our previous study to be a very effective method to decorate the surface of nanorods . Vertically ordered NiO nanorods are a very efficient structure for accessibility to target gas molecules (utility factor) and interaction between NiO and α‐Fe 2 O 3 , which both have catalytic effects on the selective oxidation of methyl groups, especially for C 7 H 8 , contributing to the enhanced gas sensing properties (receptor function). However, we attribute the observed dramatic enhancement mainly to the increased potential barrier induced by the above‐mentioned morphological changes (transducer function).…”

“…The response ratio S a /S b , where S b and S a are responses of the bare NiO nanorods and the α‐Fe 2 O 3 ‐decorated NiO nanocorals, respectively, varied with the target gas, although C 7 H 8 showed an extremely high response ratio, allowing selective detection of C 7 H 8 . Compared to previous studies of gas sensors based on NiO and α‐Fe 2 O 3 , such a strong selective detection of a single target gas among various gases, as shown in Figure c, has not been shown before . To investigate the selectivity in more detail, we examined the sensing results to three consecutive pulses of various gases (Figure S5, Supporting Information) based on PCA.…”

“…Heterostructures with metal or metal oxide decorations can enhance gas sensing properties by promoting the adsorption of target gases (chemical sensitization) or by resistance modulation upon gas adsorption (electronic sensitization) . Recently, a wide variety of heterostructures based on p ‐type NiO with n ‐type α‐Fe 2 O 3 was studied, such as hollow spheres, nanofibers, and tubular structures, for use in highly sensitive and selective VOC gas sensors, because α‐Fe 2 O 3 promotes selective oxidation of methyl groups (CH 3 ) at elevated temperatures under oxidizing atmospheric conditions . Despite reasonable results, achieving well‐established and reproducible processes has remained as a problems to overcome.…”

Effect of Sensitization on the Electrochemical Properties of Nanostructured NiO

“…p-type nickel oxide (NiO) [1,2]; is widely employed as electrodic material in photoelectrochemical cells [3][4][5][6][7][8][9], electrochromic windows [10][11][12][13][14], and charge storage systems [15][16][17], among others [18][19][20]. The wide range of NiO applicability derives from the fact that NiO can constitute a functional material in both bulk [21] and nanostructured [22,23] versions.…”