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Abstract

ZnO/WS2 Hybrid Material, for NO2 Detection, via the Combination of AACVD and APCVD Techniques †

by
Shuja Bashir Malik
,
Eduard Llobet
and
Fatima Ezahra Annanouch
*
Departament d’Enginyeria Electronica, Universitat Rovira i Virgili, Països Catalans 26, 43007 Tarragona, Spain
*
Author to whom correspondence should be addressed.
Presented at the XXXV EUROSENSORS Conference, Lecce, Italy, 10–13 September 2023.
Proceedings 2024, 97(1), 133; https://doi.org/10.3390/proceedings2024097133
Published: 1 April 2024
(This article belongs to the Proceedings of XXXV EUROSENSORS Conference)

Abstract

:
We report for the first time the successful synthesis of ZnO/WS2 hybrid material using a combination of aerosol-assisted chemical vapor deposition (AA-CVD) and atmospheric pressure CVD techniques. The morphology and the composition of the grown films were investigated and the results confirm the co-existence of both materials. Moreover, gas-sensing results against 500 ppb of NO2 revealed the influence of WS2 material on the ZnO gas-sensing performance. The operating temperature shifted towards lower values, from 300 °C to 150 °C. Furthermore, at room temperature, the ZnO/WS2 sensor was able to detect NO2 at ppb level.

1. Introduction

Zinc oxide (ZnO) is an n-type semiconductor with a wide band gap of 3.3 eV and high chemical and thermal stability [1]. It has been extensively studied and employed in gas sensing applications due to its low cost, non-toxicity and excellent gas sensing response. However, ZnO-based gas sensors operate at high temperatures (300 °C to 500 °C) and suffer from lack of selectivity, which are issues that hinder their use in a range of real-time applications. In a quest to overcome these shortcomings, researchers have been drawn towards the synthesis of hybrid nanocomposites of metal oxides with two-dimensional (2D) nanomaterial, to create heterojunctions through the nanocomposite and achieve outstanding gas-sensing performance. In this context, tungsten disulfide (WS2) is one of the most studied 2D transition metal-dichalcogenides materials (TMDs). It is characterized by its high sensitivity, stability and low operating temperature. The co-deposition of these new materials (TMDs) with metal oxides is very challenging, due to the problems that face their synthesis, for instance: low production yield and difficulties around their integration in standard transducing substrates. Here, we report, for the first time, the successful synthesis of ZnO/WS2 nanocomposite for NO2 detection, using the combination of AACVD and APCVD.

2. Materials and Methods

WS2 synthesis: WS2 synthesis was performed by using two deposition steps: the first is the AACVD of tungsten hexacarbonyl (W(CO)6; 50 mg) dissolved in a mixture of acetone and methanol (20 mL) to form tungsten oxide nanoneedles. In the second step, the obtained nanoneedles were subjected to an ambient-pressure CVD sulfurization using a sulfur powder and argon as a carrier gas, which resulted in a homogenous film composed of WS2 nanotriangles, directly grown on alumina sensor transducer (Pt interdigitated electrode from one side and a resistive Pt heater at the back side). More details can be found in our previous reports [2]. ZnO/WS2 synthesis: herein, ZnO nanorods were directly grown on the top of WS2-based alumina substrate using AACVD of ZnCl2 dissolved in ethanol at 400 °C. Nitrogen was used as carrier gas and the deposition time was approximately 30 min.

3. Discussion

Figure 1a and b illustrates the morphology of bare ZnO nanorods and WS2 nanotriangles, respectively. Figure 1c and d shows the morphology of the obtained ZnO/WS2 nanocomposite. As we can observe, ZnO nanorods were successfully grown on top of WS2 nanotriangles, using a simple combination of AACVD and APCVD techniques. To confirm the structure and the composition, we analyzed our samples (ZnO and ZnO/WS2) with Raman (Figure 1e,f) and energy-dispersive spectroscopy (EDX) techniques (Figure 1g). The results confirm the simultaneous presence of multilayers of WS2 and ZnO materials.
Furthermore, we have tested bare ZnO and ZnO/WS2 gas sensors against 500 ppb of NO2 at different working temperatures. According to the results (Figure 2a,b), bare ZnO showed no response below 200 °C and its optimal working temperature was considered at 300 °C. In contrast, the hybrid ZnO/WS2 sensor was quite responsive at very low temperatures, especially at 150 °C where it shows stable and reproducible responses with good sensitivity (Figure 2c). This shift in the optimal working temperature demonstrates the effect of the addition of TMDs nanomaterials to the ZnO host matrix.

Author Contributions

S.B.M.: Methodology, Formal analysis, Investigation, Data curation, Writing—original draft, Visualization. F.E.A: Methodology, Validation, Resources, Writing—review & editing, Supervision, E.L: Conceptualization, Methodology, Validation, Resources, Writing—review & editing, Supervision, Funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

S.B.M. is supported by Martí-Franquès Research grants Programme, Doctoral grants—2019, (2019PMF-PIPF-14).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this research work.

References

  1. Vallejos, S.; Pizúrová, N.; Gràcia, I.; Sotelo-Vazquez, C.; Čechal, J.; Blackman, C.; Parkin, I.; Cané, C. ZnO Rods with Exposed {100} Facets Grown via a Self-Catalyzed Vapor–Solid Mechanism and Their Photocatalytic and Gas Sensing Properties. Appl. Mater. Interfaces 2016, 8, 33335–33342. [Google Scholar] [CrossRef]
  2. Alagh, A.; Annanouch, F.E.; Colomer, J.F.; Llobet, E. 3D Assembly of WS2 Nanomaterial for H2S Gas Sensing Application. In Proceedings of the 2020 IEEE SENSORS, Rotterdam, The Netherlands, 25–28 October 2020; IEEE: Piscataway, NJ, USA, 2020. [Google Scholar] [CrossRef]
Figure 1. FESEM images of (a) ZnO, (b) WS2, (c,d) ZnO/WS2, (e,f) Raman spectra and (g) EDX anaysis of ZnO/WS2.
Figure 1. FESEM images of (a) ZnO, (b) WS2, (c,d) ZnO/WS2, (e,f) Raman spectra and (g) EDX anaysis of ZnO/WS2.
Proceedings 97 00133 g001
Figure 2. Sensor response as a function of temperature (a) ZnO, (b) ZnO/WS2 and (c) example of ZnO/WS2 resistance change in response to 500 ppb of NO2.
Figure 2. Sensor response as a function of temperature (a) ZnO, (b) ZnO/WS2 and (c) example of ZnO/WS2 resistance change in response to 500 ppb of NO2.
Proceedings 97 00133 g002
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Share and Cite

MDPI and ACS Style

Malik, S.B.; Llobet, E.; Annanouch, F.E. ZnO/WS2 Hybrid Material, for NO2 Detection, via the Combination of AACVD and APCVD Techniques. Proceedings 2024, 97, 133. https://doi.org/10.3390/proceedings2024097133

AMA Style

Malik SB, Llobet E, Annanouch FE. ZnO/WS2 Hybrid Material, for NO2 Detection, via the Combination of AACVD and APCVD Techniques. Proceedings. 2024; 97(1):133. https://doi.org/10.3390/proceedings2024097133

Chicago/Turabian Style

Malik, Shuja Bashir, Eduard Llobet, and Fatima Ezahra Annanouch. 2024. "ZnO/WS2 Hybrid Material, for NO2 Detection, via the Combination of AACVD and APCVD Techniques" Proceedings 97, no. 1: 133. https://doi.org/10.3390/proceedings2024097133

APA Style

Malik, S. B., Llobet, E., & Annanouch, F. E. (2024). ZnO/WS2 Hybrid Material, for NO2 Detection, via the Combination of AACVD and APCVD Techniques. Proceedings, 97(1), 133. https://doi.org/10.3390/proceedings2024097133

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