Oxidizing gas sensing properties of the n-ZnO/p-Co3O4 composite nanoparticle network sensor

Park, Sunghoon; Kim, Soohyun; Kheel, Hyejoon; Lee, Chongmu

doi:10.1016/j.snb.2015.08.006

Cited by 109 publications

(41 citation statements)

References 30 publications

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“…Upon exposure to air, oxygen molecules are adsorbed onto the surface of semiconductor metal oxides, forming ions of O2 − (below 150 °C), O − (150-400 °C) and O 2− (above 400 °C) through trapping electrons from the conduction band. 35 As the sensing tests were carried out at 115 °C in this study, highly reactive oxygen species of O2 − (ads) ions may be predominately formed on the surface of p-type Co3O4 by capturing electrons from conduction band, and holes are generated at the valence band of Co3O4 according to equation 2, resulting in the formation of a hole accumulation layer in the surface region of Co3O4 nanoparticle. 33 On the other hand, upon exposure to air, oxygen molecules are adsorbed onto the surface of n-type TiO2 nanoparticle as well and transform into O2 − (ads) ions by capturing electrons from TiO2 conduction band according to equation 3, leading to a thicker electron depletion layer in the surface region of TiO2 (Fig.…”

Section: Gas Sensing Mechanismmentioning

confidence: 99%

“…5,27,[33][34][35] It is worth noting that the formation of p-n heterojunctions is an efficient and cost-effective technique to improve the activity and sensitivity of gas sensors 3,34,35 , and hierarchical structures offer abundant pores and large surface area which benefit the diffusion and adsorption of testing gases. 26 For example, Deng et al 16 prepared CuO-TiO2 heterostructure nanofibers and found that the formation of p-n heterojunctions considerably improved the sensitivity of TiO2 nanofibers to formaldehyde at 200 ºC.…”

Section: Introductionmentioning

confidence: 99%

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Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance

et al. 2017

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The development of highly active, sensitive and durable gas sensing materials for the detection of volatile organic compounds (VOCs) is extremely desirable in gas sensors. Herein, a series of mesoporous hierarchical Co3O4-TiO2 p-n heterojunctions have been prepared for the first time via the facile thermal conversion of hierarchical CoTi layered double hydroxides (CoTi-LDH) precursors at 300-400 ºC. The resulting Co3O4-TiO2 nanocomposites showed superior sensing performance towards toluene and xylene in comparison with Co3O4 and TiO2 at low temperature, and the sample with a Co/Ti molar ratio of 4 shows optimal response (Rg/Ra = 113, Rg and Ra denote the sensor resistance in a target gas and in air, respectively) to 50 ppm xylene at 115 ºC. The ultrahigh sensing activity of theses Co3O4-TiO2 p-n heterojunctions originates from their hierarchical structure, high specific surface area (>120 m 2 g −1 ), and the formation of numerous p-n heterojunctions, which results in full exposure of active sites, easy adsorption of oxygen and target gases, and large modulation of resistance. Importantly, hierarchical Co3O4-TiO2 heterojunctions possess advantages of simple preparation, structural stability, good selectivity and long-term durability. Therefore, this work provides a facile approach for the preparation of hierarchical Co3O4-TiO2 p-n heterojunctions with excellent activity, sensitivity and durability, which can be used as a promising material for the development of high-performance gas sensors.

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Section: Gas Sensing Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance

et al. 2017

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“…Functionalization of ZnO with metal oxide nanoparticles has found a great interest in recent years for the formation of semiconductive heterostructures with advanced optical, catalytic and electronic properties . Several p‐type metal oxide NPs like copper oxide (CuO), nickel oxide (NiO) or cobalt oxide (Co 3 O 4 ) have been deposited on n‐type ZnO nanostructures to form p‐n junction based devices. Heterostructures between semiconductors with different majority carrier type strongly enhanced photocatalytic efficiency.…”

Section: Surface‐engineering Of Zno Nanostructures With Nanoparticlesmentioning

confidence: 99%

Surface Engineering of Nanostructured ZnO Surfaces

Laurenti

Stassi

Canavese

et al. 2016

Adv Materials Inter

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are oriented in one direction and their assembly and stacking produces the wurtzite hexagonal symmetry. The noncentrosymmetric and anisotropic crystalline structure of wurtzite-like ZnO generates very interesting properties such as piezo-and pyro-electricity: the application of an external stimulus, like mechanical stress or temperature, deforms the tetrahedron structure. This deformation results in a separation between the positive and negative centers of charge, inducing the formation of a dipole moment. [7,8] The polar surface and anisotropic structure of ZnO can be usefully exploited to form different kinds of micro and nanostructures from 0D to 3D, [5] including, but not limited to nanowires, [9][10][11][12] nanotubes, [13,14] nanobelts, [15][16][17][18][19] nanorings, [20] flower-like morphologies, [21][22][23][24][25] multipods, [26,27] tetrapods, [28][29][30] sponge-like structures [31][32][33][34] and so on [29,[35][36][37][38][39] (Figure 1). Therefore, several research efforts have been invested in studying various preparation procedures for ZnO micro and nano-materials. Wet chemical approaches, like sol-gel, hydrothermal growths, electrodeposition and template-assisted routes, [40,41] as well as vapor-phase methods, for example chemical vapour deposition (CVD), physical vapour deposition (PVD) including sputtering and evaporation approaches, [42][43][44] and epitaxial growth methods [45] are among the most used ones. The great advantages of the wet chemical approaches are the high synthesis versatility, low temperature employed and low costs. [9] From the other side, dry methods take advantage of the high quality and excellent control over the level of crystallinity of the synthesized ZnO structures, as well as the absence of contamination and high purity of the final material. [46] The combination of different properties with the ease and high versatile synthesis of ZnO material in different micro and nanostructures offers a huge possibility of potential applications.For example, ZnO is already used as an efficient catalyst in the selective oxidation of involving oxygenates (i.e., alcohols, aldehydes, and carboxylic acids) and in methanol synthesis catalysts. It is also largely applied as protective, anti-corrosion layer in galvanized steel products, [49][50][51] as well as in paints and sunscreens as an UV absorber. Its biocompatibility makes this material suitable, in the form of microparticles, for paste formulations in cosmetic applications.The combination of the piezoelectric with the semiconducting properties of ZnO is found to result into new exciting physical properties, [52][53][54] and it has recently opened the research field to energy harvesting application. ZnO nanomaterials can be thus used as nanogenerators, able to convert the mechanical deformation from the surrounding environment into electrical Zinc Oxide (ZnO) nanostructures represent promising substrate materials for numerous applications, ranging from new generation solar cells, to bio-and chemical sensors. This interest is due ...

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“…For this, Co 3 O 4 nanostructures has found potential application in different fields such as supercapacitor [11], photo electrochemical water splitting [13], gas sensor [14], lithium ion batteries [15]. Till now, many studies have been assigned to investigate ZnO and Co 3 O 4 nanostructures separately, but there are limited research on investigation of Co 3 O 4 /ZnO nanocomposite [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Degradation of methylene blue and Rhodamine B as water pollutants via green synthesized Co3O4/ZnO nanocomposite

Hassanpour

Safardoust-Hojaghan

Salavati‐Niasari

2017

Journal of Molecular Liquids

194

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Methylene blue (MB) and Rhodamine B (RB) are produced as water pollutants in textile, plastic and dye industries. Many studies have investigated to remove RB and MB in wastewater of industries. At present work, Co 3 O 4 /ZnO nanocomposite is applied for removal of MB and RB dyes from water. Eco friendly, Co 3 O 4 /ZnO is synthesized via microwave assisted method. Results showed that uniform morphology and size particle is obtained at 10 min and 900W as optimum time and power. Synthesized Co 3 O 4 /ZnO is characterized with X-ray diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM) and vibrating sample magnetometers (VSM). Prepared nanocomposite shows excellent photo degradation behavior toward MB and RB under UV light. Photo degradation efficiency is calculated 80 and 90% for MB and RB respectively.

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Oxidizing gas sensing properties of the n-ZnO/p-Co3O4 composite nanoparticle network sensor

Cited by 109 publications

References 30 publications

Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance

Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance

Surface Engineering of Nanostructured ZnO Surfaces

Degradation of methylene blue and Rhodamine B as water pollutants via green synthesized Co3O4/ZnO nanocomposite

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Oxidizing gas sensing properties of the n-ZnO/p-Co3O4 composite nanoparticle network sensor

Cited by 109 publications

References 30 publications

Facile synthesis of mesoporous hierarchical Co3O4–TiO2 p–n heterojunctions with greatly enhanced gas sensing performance

Facile synthesis of mesoporous hierarchical Co3O4–TiO2 p–n heterojunctions with greatly enhanced gas sensing performance

Surface Engineering of Nanostructured ZnO Surfaces

Degradation of methylene blue and Rhodamine B as water pollutants via green synthesized Co3O4/ZnO nanocomposite

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Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance

Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance