Elsevier

Acta Materialia

Volume 88, 15 April 2015, Pages 245-251
Acta Materialia

Structure-dependent gas detection ability of clustered ZnS crystallites with heterostructure and tube-like architecture

https://doi.org/10.1016/j.actamat.2015.01.036Get rights and content

Abstract

ZnS crystallites with a core–shell heterostructure (ZnO–ZnS core–shell rods) and tube-like architecture were synthesized through a facile chemical solution route. Many tiny ZnS particles were clustered and compacted to form the shell layer of the ZnO–ZnS core–shell rods and the wall of the ZnS tubes during sulfidation of vertically aligned ZnO rods. X-ray diffraction and transmittance electron microscopy images revealed that the ZnS shell layer of the ZnO–ZnS core–shell rods and the wall of the tubes were polycrystalline, and that many domains or grain boundaries were present in the ZnS layers. The sensitivities of ZnO–ZnS core–shell rods and ZnS tubes to reducing and oxidizing gases differed. The ZnO–ZnS core–shell rods were more sensitive to reducing gases, whereas the ZnS tubes were more sensitive to oxidizing gases. The different gas sensing properties of the ZnS-based heterostructures and tubes are further discussed in relation to their microstructures. The heterojunction at the ZnO/ZnS interfacial region resulted in the differing gas sensing properties of the ZnS-based heterostructures and tubes in this study.

Introduction

Core–shell heterostructures and tube-like nanomaterials have attracted considerable attention because their versatility renders them suitable for use in many devices [1], [2], [3]. As a major II–VI group semiconductor, zinc oxide (ZnO) has a wide band gap of approximately 3.3 eV at room temperature [4]. ZnO nanostructures can be prepared on a large scale by using a facile hydrothermal method [5], and ZnO nanostructures with various morphologies have been extensively studied for use in gas sensors [6], [7]. By contrast, zinc sulfide (ZnS), another II–VI group semiconductor, has a wider band gap (3.7 eV) and has been used in gas and ultraviolet (UV) light sensors [8], [9]. According to the relevant research, oxide and sulfide semiconductors with one-dimensional (1D) structures can potentially be applied in highly efficient nanodevices. One-dimensional semiconductors with a three-dimensional architecture exhibit a high surface-to-volume ratio and excellent physical and chemical properties [2], [6]. Experimental results have revealed that combining two wide band gap semiconductors can yield a novel material featuring improved functions compared with the individual semiconductor material [10], [11], [12]. In addition to heterostructures, 1D materials with a porous structure or a tube-like morphology have been demonstrated to exhibit superior gas sensing response and sensitivity [13], [14].

Although several studies have shown the superior gas sensing properties of oxide-based heterostructures and tubes, reports on the gas sensing property of ZnS-based heterostructures and tubes are limited [15]. Therefore, the gas sensing behavior of ZnS-based heterostructure and tubes toward various target gases requires further investigation for enhancing and optimizing the gas sensing characteristics of these materials. Several facile chemical approaches have been proposed for synthesizing various ZnS-based heterostructures and porous structures [16], [17], [18]. These studies revealed that different chemical solution routes led to various morphologies of ZnS-based heterostructures and porous structures. The microstructure of nanomaterials affects their gas sensing properties [19]. Although detailed methodology dependent structural characterizations of the ZnS-based heterostructures and porous structures have been performed, no studies have investigated the applications of these materials in gas-sensing devices. This insufficient information has hindered development of ZnS-based heterostructures and porous structures for applications in gas-sensing devices. In this paper, we report the synthesis of high-density ZnS-based heterostructures and tubes using ZnO rods as the sacrificial template for various durations of sulfidation. The ZnS-based heterostructures and tubes synthesized were structurally characterized. Moreover, the capabilities of the heterostructures and tubes to sense reducing and oxidizing gases were compared. The mechanisms associated with the gas-sensing responses were examined to determine the origin of the superior gas-sensing response of the ZnS-based heterostructures and tubes.

Section snippets

Experiments

Hydrothermally synthesized high density ZnO rods on the 200 nm-thick SiO2/Si (1 0 0) substrates were used as templates for further sulfidation treatment to growth of ZnO–ZnS core–shell rods and ZnS nanotubes. The synthesis of vertically aligned ZnO rods consisted of two steps corresponding to the formation of ZnO seed layer and the growth of rods. The detailed experiment on the synthesis of hydrothermally synthesized ZnO rods has been described elsewhere [20]. The as-synthesized ZnO rods were

Structural characterization

Fig. 1 (a) shows a SEM image of the as-prepared ZnO rods; the ZnO rods were covered homogeneously over the substrate. The diameter of the ZnO rods ranged from 70 nm to 100 nm, and the surface of the ZnO rods was smooth. Fig. 1(b) shows the SEM image of the ZnO rods subjected to a 5-h sulfidation treatment. After sulfidation, the hexagonal faces of the rods became rounded. The surface of the ZnO rods was covered with many granular particles, resulting in a rough surface. Density of the irregular

Conclusions

ZnO–ZnS core–shell rods and ZnS tubes were synthesized using ZnO rods as the sacrificial template during sulfidation. The experimental results showed that the duration of sulfidation affected the formation of the ZnS crystallites required for a core–shell heterostructure (ZnO–ZnS core–shell rods) or tube-like architecture. The structural analyses revealed that the surface of the ZnO–ZnS core–shell rods and ZnS tubes was rough because many tiny ZnS particles aggregated to form the ZnS shell

Acknowledgement

This work is supported by the Ministry of Science and Technology of Taiwan (Grant No. NSC 102-2221-E-019-006-MY3).

References (33)

  • Y.C. Liang

    J. Alloys Compd.

    (2010)
  • U. Alver et al.

    Appl. Surf. Sci.

    (2012)
  • Y.C. Liang et al.

    J. Alloys Compd.

    (2014)
  • J.J. Hassan et al.

    Sens. Actuators B

    (2013)
  • X. Fang et al.

    Prog. Mater. Sci.

    (2011)
  • H. Tang et al.

    Acta Mater.

    (2004)
  • B.R. Huang et al.

    Appl. Surf. Sci.

    (2013)
  • Y. Liu et al.

    Appl. Surf. Sci.

    (2011)
  • L. Dloczik et al.

    Sens. Actuators B

    (2002)
  • W. Zhang et al.

    Sens. Actuators B

    (2012)
  • X. Gao et al.

    Ceram. Int.

    (2013)
  • Y.C. Liang et al.

    Appl. Surf. Sci.

    (2012)
  • Y.C. Liang

    Ceram. Int.

    (2012)
  • Y.C. Liang et al.

    Appl. Surf. Sci.

    (2014)
  • X.J. Zhang et al.

    Appl. Surf. Sci.

    (2012)
  • C. Jin et al.

    Sens. Actuators B

    (2012)
  • Cited by (18)

    • Mechanism and characteristics of Au-functionalized SnO<inf>2</inf>/In<inf>2</inf>O<inf>3</inf> nanofibers for highly sensitive CO detection

      2020, Journal of Alloys and Compounds
      Citation Excerpt :

      Therefore, it is very important to develop a high response gas sensor that can detect gases at low concentrations. Many metal oxide semiconductor materials such as SnO2, TiO2, In2O3, and ZnO have been found to have good chemical stability and a high gas sensing response, and they have been widely studied by scholars in recent years [1–5]. Indium oxide (In2O3) has a direct band gap of about 3.6 eV and an indirect band gap of about 2.6 eV In2O3 materials with different morphologies, such as nanoparticles [6], nanofibers [7], nanowires [8], nanotubes [9], nanosheets [10], and nanorods [11], have received significant attention due to their potential applications for use in solar cells [12], photocatalytic applications [13], transparent conducting oxide [14], and gas sensors [15].

    • Hydrothermally derived zinc sulfide sphere-decorated titanium dioxide flower-like composites and their enhanced ethanol gas-sensing performance

      2018, Journal of Alloys and Compounds
      Citation Excerpt :

      For example, gold-functionalized ZnS nanowires were utilized to detect nitrogen dioxide (NO2) under ultraviolet illumination [16]. Elsewhere, hydrothermally derived ZnS nanocrystals were used to detect H2S with a visible gas-sensing behavior [17], and hydrothermally derived ZnS tubes were used to detect ethanol vapor and NO2 gas with a satisfactory sensing performance [18]. On the basis of the suitable application of ZnS in gas-sensing materials, the integration of ZnS into TiO2 to form a TiO2-based heterostructure can be a promising approach for improving the gas-sensing performance of TiO2.

    • Photoactivity enhancement of zinc sulfide ceramics thin films through ultrathin buffering engineering

      2016, Ceramics International
      Citation Excerpt :

      It possesses two stable cubic and hexagonal crystal structures, with bandgap values of approximately 3.54 eV and 3.80 eV, respectively [5,6]. ZnS has a variety of scientific applications such as photocatalysts, phosphors, and gas and humidity sensors because of its variety of physical properties [1,3,7,8]. Among its various material dimensions, ZnS in the form of two-dimensional thin film is highly desired for application in scientific devices.

    • Synthesis and microstructure-dependent photoactivated properties of three-dimensional cadmium sulfide crystals

      2016, Journal of Alloys and Compounds
      Citation Excerpt :

      Most photoactivated properties of binary semiconductors require ultraviolet (UV) light for promoting interaction between the semiconductors and their environment. Because UV light accounts for only a small fraction of solar radiation, this limits the efficiency of these semiconductors when they are used in photoactivated devices [1–3]. Recently, because of their capability to use solar energy, sulfide semiconductors with visible light band gaps have attracted considerable attention for use in photoactivated devices [4–7].

    View all citing articles on Scopus
    View full text