2D nanosheet-assembled PdZnO microflowers for acetone sensor with enhanced performances

doi:10.1016/j.jpcs.2018.09.006

Journal of Physics and Chemistry of Solids

Volume 124, January 2019, Pages 330-335

https://doi.org/10.1016/j.jpcs.2018.09.006 Get rights and content

Highlights

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2D porous nanosheet-assembled ZnO microflowers were prepared.
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PdZnO was obtained by injecting Pd²⁺ solution onto the surface of thin film.
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The Pd-doped ZnO sensors show enhanced performance for acetone vapor.

Abstract

Hierarchical microflowers architecture assembled with 2D porous ZnO nanosheets were fabricated by a one-step solvothermal method and subsequent annealing process. A series of Pd single bond ZnO have been produced by injecting various volumes of Pd(NO₃)₂·2H₂O solution. The ZnO and PdZnO microflowers are applied to fabricate gas sensors to investigate their sensing characteristics for various gases at different operating temperatures. The 0.05 wt% PdZnO exhibit the highest selective enhancement of acetone (165%) than ammonia (0.9%), methanal (38%), methanol (71%), H₂ (35%) and CO (15%). In addition, it possesses the lower operating temperature and shorter response/recovery times (11s, 5s) toward acetone gas compared with the pure ZnO microflowers.

Graphical abstract

Introduction

Acetone is an important raw material for organic synthesis, the good organic solvents and the extracting agent of industry. In particular, the concentration of acetone in breath could be a vital index for diabetes mellitus [1,2]. Hence, it is urgent to find an easier, more effective solution to detect the acetone. Recently, acetone chemical sensor based on the metal-oxide semiconductors has been widely investigated for its high sensitivity, excellent selectivity and long-time stability [3,4].

Zinc oxide (ZnO), with a band gap (3.37eV), has been widely applied in photocatalysis, solar cell, transistor devices, water splitting and gas sensors [2,[5], [6], [7], [8]]. Till now, diverse morphologies of ZnO, such as nanoparticle, nanowire, nanorod, and nanosheet [[9], [10], [11], [12], [13]], have been carried out by using various synthesis methods. ZnO nanosheet, for example, has been extensively used to detect chemicals such as acetone (CH₃COCH₃), ethanol (C₂H₅OH), nitrogen dioxide (NO₂), methanal (HCHO) and carbonic oxide (CO) [[14], [15], [16], [17], [18]]. In recent years, the high level 3D supercrystals evolved from low dimensional nano-architectures has caused great attention [[19], [20], [21]]. Due to the large specific surface areas, 3D porous architectures or hollow microspheres materials were always applied to fabricate sensors and exhibited enhanced responses for toxic gas [22,23]. However, gas sensors still meet testing requirements under some rigorous conditions like low selectivity and high operating temperature [24]. To overcome the issues, many efforts to improve the sensitivity of ZnO sensors have been made for examples, preparation of nanostructures with different morphologies [17,25], metal oxide heterostructures [20,26], and noble metals adding (such as Ag, Au, Pd, Pt) [[27], [28], [29]]. Pd nanoparticles (NPs) is one of the best gas sensor candidate owing to their excellent chemical stability, high surface area and low orbital energy [[30], [31], [32]]. Hence, Pd single bond ZnO materials could improve the sensing response, selectivity, response time and recovery of chemical sensors. However, only a few articles have been concerned with the synthesis of PdZnO microflowers and focused on the selective enhancement to acetone vapor.

In this paper, porous nanosheet-assembled hierarchical ZnO microflowers are synthesized via a novel one-step solvothermal route and subsequently a calcination procedure. Pd nanoparticles in size of 10 nm are uniformly decorated on the surface of ZnO through injecting the solutions of Pd(NO)₃·2H₂O. Sensing performance based on pristine ZnO and Pd single bond ZnO are systematically investigated.

Section snippets

Synthesis of ZnO microflowers

1 mmol of ZnCl₂ and 1 mmol of urea were dissolved into 40 mL of mixture solution which containing ethanol and deionized water with a ratio of 3:1. After the solution became homogeneous, PVP (0.2000 g) was added which acting as an surfactant to help the structure forming of ZnO precursors. The mixtures were transferred into 50 mL teflon-lined stainless steel autoclaves and kept at 180 °C for 4 h. The white precipitates were obtained after hydrothermal reaction and washing several times, dried at

Results and discussion

XRD was firstly applied to investigate the phase structure of precursor. All the peaks match well with Zn₅(OH)₆(CO₃)₂ (JCPDS card No. 72-1100) in Fig. 1a. The product of Zn₅(OH)₆(CO₃)₂ after annealing is indexed as hexagonal wurtzite ZnO (JCPDS card No. 36-1451) shown in Fig. 1a. No peak for other impurities can be detected, indicating a complete conversion of the precursor into pure ZnO. Sharp diffraction peaks indicate the high degree crystalline of ZnO after dealing with higher temperature.

Conclusions

In summary, the porous Pd single bond ZnO microflowers were successfully synthesized by injecting the solution of Pd²⁺ onto the surface of ZnO thin films. In particular, the method can effectively control the concentration of the Pd NPs by adding various volumes of the Pd²⁺ solutions. Compared with the pure ZnO sensors and Pd single bond ZnO, the gas sensing performances of PdZnO (0.05 wt%) sensors demonstrated excellent sensitivity, low operation temperature, and the superior selectivity toward acetone.

Acknowledgements

The authors are grateful to the National Nature Science Foundation of China (21771166, 21301158), Outstanding Young Scholars Program of Henan Province (164100510011).

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View full text

2D nanosheet-assembled PdZnO microflowers for acetone sensor with enhanced performances

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Synthesis of ZnO microflowers

Results and discussion

Conclusions

Acknowledgements

Sensor. Actuator. B Chem.

Thin Solid Films

Sensor. Actuator. B Chem.

Sensor. Actuator. B Chem.

Sensor. Actuator. B Chem.

J. Alloy. Comp.

J. Phys. Chem. Solid.

Mater. Chem. Phys.

J. Mol. Catal. Chem.

Acetone gas sensors based on ZnO nanostructures decorated with Pt and Nb

Ceram. Int.

Nonlinear optical rod indium-imidazoledicarboxylate framework as room-temperature gas sensor for butanol isomers

Cryst. Growth Des.

Fabrication of a highly sensitive single aligned TiO2 and gold nano-particle embedded TiO2 nano-fiber gas sensor

ACS Appl. Mater. Interfaces

GaN: ZnO solid solution as a photocatalyst for visible-light-driven overall water splitting

J. Am. Chem. Soc.

Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO

Nat. Mater.

Nitrogen-doped ZnO nanowire arrays for photoelectrochemical water splitting

Nano Lett.

ZnO nanostructures for dye-sensitized solar cells

Adv. Mater.

Fabrication and gas-sensing properties of porous ZnO nanoplates

Adv. Mater.

Fabrication of a highly sensitive single aligned TiO₂ and gold nano-particle embedded TiO₂ nano-fiber gas sensor