Flexible and low power CO gas sensor with Au-functionalized 2D WS2 nanoflakes
Introduction
Air pollution consists of particulate matter (PM), CO, NO2 O3, and SO2 [1]. It has been reported that 92% of the world’s population live in areas with poor air quality, which are in risk of premature death due to air pollution [2]. In fact, pollution which is the world's largest cause of disease and premature death, is responsible for 16% of total deaths worldwide [3]. Accordingly, air pollution is an active area of sensing research nowadays.
Among different developed sensing devices for detection of pollutant gases, soft gas sensors which are flexible and stretchable are of importance, due to the fact that such sensors can be easily implemented in portable, wearable, and low-power consumption electronics [4,5]. Generally, development of flexible gas sensors is a difficult challenge, since they should have comparable sensing performance with respect to sensitivity, selectivity and fast dynamics with other sensors on rigid substrates at low working temperatures. Furthermore, it should have an excellent stability and repeatability under tilting or stretching conditions for several times [6].
Thus far, gas sensors with flexible substrates such as plastics [7], polymers [8] and paper [9] have been reported. In particular, plastic substrates such as polyamide are very popular for realization of flexible gas sensors. In addition to flexibility, they have low cost and availability [6]. However, the success of flexible gas sensors, greatly depends on low operating temperature conditions. High temperatures are needed for both fabrication and operation of traditional gas sensors [10], seriously limiting the possibility of their application to flexible gas sensors. Accordingly, development of low power consuming gas sensors using self-heating technique is vital for the realization of flexible gas sensors. Such gas sensors not only have great flexibility to be installed in different places, but also their energy consumption is extremely low, enabling them to be used in instruments and electronic devices with low power consumption.
Based on the literature, resistive-based gas sensor generally need high temperatures for gas sensing which increases their power consumption. Self-heating mode-operation can decrease the power consumption, where the applied voltage for measuring of electrical resistance will generate heat inside the sensing layer and will provide the energy needed for adsorption of target gas [11]. To realize self-heated gas sensors, one dimension and two-dimensional (2D) morphologies often are preferred since they offer good surface area, where electrons in their pathways can be scattered by different obstacles, resulting in high heat generation.
Earth-abundant, layered transition metal dichalcogenides (TMDs) with two-dimensional structures, can be synthesized with large surface-area, and owing to possibility of tuning the band gaps and high mobility of charge carriers, they are considered as good materials for sensing studies [[12], [13], [14], [15], [16]]. Tungsten disulfide (WS2) as a TMD, has some unique properties including excellent thermal stability, low cost and tunable band structure [17]. Weak van der Waals forces connect vertically-stacked layers, facilitating diffusion of the target gas among the layers [18]. Accordingly, WS2 can be used for low temperature gas sensors [[19], [20], [21]]. Nonetheless, pristine WS2 gas sensors show low sensitivity, selectivity and long recovery time, limiting their applications for practical usages [22,23]. Noble metal functionalization is a promising avenue to enhancing the sensing properties of WS2 owing to the catalytic effect of Au. These improvements ultimately enhance the response, and selectivity of a gas sensor [24,25].
As a highly toxic gas, carbon monoxide (CO) has no signs such as color, taste, and odor [26]. It can be produced by incomplete combustion of fuels: a burning wood or stove and even a candle in a closed space are potential sources for the release of CO gas. Despite seemingly benign sources, CO is an invisible, silent killer, and at high concentrations death is likely. Exposure to 0.5 % of CO for 10 min can cause death [27]. Currently, over 15,000 intentional CO poisoning occurs annually [28]. Many people are poisoned by CO the home, due gasoline-powered engines like cooking appliances [29]. Also, CO is a biomarker, where the CO concentration in the exhaled breath of the sick people is higher than those of normal people [30,31]. Therefore, selective sensing of CO in a flexible and low-power consumption sensing device is useful for many applications.
In this wok, we realized Au-functionalized WS2 gas sensors for low power consumption CO gas sensing studies. It was found that selective and low-power CO gas sensor with good flexibility can be easily realized using combination of Au and 2D WS2 nanoflakes. While the sensing application of 2D metal oxide nanoflakes was previously reported [32], there has been rare report on the 2D WS2 nanoflakes. We demonstrated the possibility of sensing enhancement in TMDs in a simple way, which can be extended to the similar TMDs for fabrication of reliable gas sensors.
Section snippets
Fabrication of pristine and Au-functionalized of WS2 NSs gas sensors
Fig. 1a,b schematically illustrates the process for fabrication of the gas sensors. Polyamide substrate, (width: 15 mm, thickness: 25 μm, length: 20 mm) equipped with a bi-layered (Ti/Pt) electrode was used. First, a 0.005 g WS2 powder (ACS Materials) was uniformly dispersed in 0.01 ml 2-propanol under magnetic stirring. Then, using a micropipette, 0.075 μl (three drops) of the solution was coated onto the polyamide substrates and it was dried at 60 °C for 10 min. To realize the preparation of
Morphological, compositional and structural studies
SEM image of pristine 2D WS2 nanoflakes on the polyamide substrate is revealed in Fig. S1a in the Supplementary Information and that for Au-functionalize WS2 is provided in Fig. S1b. The sensing layer has covered the substrate surface, creating the considerable contacts between the sensing layer and the electrodes. Au was functionalized on the surfaces of WS2 nanoflakes, and corresponding TEM micrographs are presented in Fig. 2a-h. With increasing the irradiation time during synthesis, Au
Conclusion
In a nutshell, Au-functionalized 2D WS2 nanoflakes were realized on flexible polyamide substrate. The gas sensing results of pristine WS2 nanoflakes in self-heating operation with an optimal applied voltage of 2 V showed the poor selectivity. On the other hand, optimized Au-functionalized 2D WS2 nanoflakes revealed improved sensitivity as well as selectivity to CO gas. In addition, the Au-functionalized gas sensor kept its properties even after many-times bending, demonstrating good flexibility
Declaration of Competing 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 paper.
CRediT authorship contribution statement
Jae-Hun Kim: Data curation, Investigation, Visualization, Data curation, Writing-original draft. Ali Mirzaei: Methodology, Visualization, Validation, Writing-original draft, Writing-review & editing. Hyoun Woo Kim: Supervision, Conceptualization, Project administration, Writing-review & editing. Sang Sub Kim: Supervision, Conceptualization, Funding acquisition, Resources, Writing-review & editing.
Acknowledgments
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A1A03013422). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2019R1A2C1006193).
Jae-Hun Kim received his B.S. degree from Gyeongsang National University, Republic of Korea in 2013. In February 2015, he received M.S. degree from Inha University, Republic of Korea. He is now working as a Ph.D. candidate at Inha University, Republic of Korea. He has been working on oxide nanowire gas sensors.
References (62)
- et al.
Effects of environment pollution on the ocular surface
Ocular Surf.
(2018) - et al.
Outdoor air pollution and cystic fibrosis
Paediatric Resp. Rev.
(2018) - et al.
Pollution and children’s health
Sci. Tot. Env.
(2019) - et al.
Flexible gas sensor array with an embedded heater based on metal decorated carbon nanofibres
Sens. Actuators B
(2013) Microheater-integrated single gas sensor array chip fabricated on flexible polyimide substrate
Sens. Actuators B
(2006)- et al.
A review on efficient self-heating in nanowire sensors: Prospects for very-low power devices
Sens. Actuators B
(2018) - et al.
Conductometric gas sensing behavior of WS2 aerogel
FlatChem.
(2017) - et al.
Layered transition-metal dichalcogenides (MoS2 and WS2) for sensing and biosensing
TrAC, Trends Anal. Chem.
(2014) - et al.
2D WS2 nanosheets with tio2 quantum dots decoration for high-performance ammonia gas sensing at room temperature
Sens. Actuators B
(2017) - et al.
Effect of layer number on recovery rate of WS2 nanosheets for ammonia detection at room temperature
Appl. Surf. Sci.
(2017)
Effects of ambient humidity and temperature on the NO2 sensing characteristics of WS2/graphene aerogel
Appl. Surf. Sci.
WS2 nanoflakes based selective ammonia sensors at room temperature
Sens. Actuators, B
MoS2 gas sensor functionalized by Pd for the detection of hydrogen
Sens. Actuators B
CO gas sensing properties of In4Sn3O12 and TeO2 composite nanoparticle sensors
J. Hazard. Mater.
Carbon monoxide poisoning deaths in the United States, 1999 to 2012
Am. J. Emer. Med
Extremely sensitive and selective sub-ppm co detection by the synergistic effect of au nanoparticles and core-shell nanowires
Sens. Actuators B
2D metal oxide nanoflakes for sensing applications: review and perspective
Sens. Actuators B
Morphology-controlled porous α-Fe2O3/SnO2 nanorods with uniform surface heterostructures and their enhanced acetone gas-sensing properties
Mater. Lett.
Light enhanced VOCs sensing of WS2 microflakes based chemiresistive sensors powered by triboelectronic nangenerators
Sens. Actuators B
2D WS2 nanosheets with TiO2 quantum dots decoration for high-performance ammonia gas sensing at room temperature
Sens. Actuators B
Localized surface plasmon resonance enhanced label-free photoelectrochemical immunoassay by Au-MoS2 nanohybrid
Electrochim. Acta
highly transparent and flexible NO2 gas sensor film based on MoS2/rGO composites using soft lithographic patterning
Appl. Surf. Sci.
The ultra-high NO2 response of ultra-thin WS2 nanosheets synthesized by hydrothermal and calcination processes
Sens. Actuators B
Highly reactive 0D ZnS nanospheres and nanoparticles for formaldehyde gas-sensing properties
Sens. Actuators B
Self-heating effects in large arrangements of randomly oriented carbon nanofibers: application to gas sensors
Sens. Actuators B
CO sensor based on Au-decorated SnO2 nanobelt
Mater. Chem. Phys.
Low power-consumption CO gas sensors based on Au-functionalized SnO2-ZnO core-shell nanowires
Sens. Actuators B
Physically Flexible, Rapid‐Response Gas Sensor Based on Colloidal Quantum Dot Solids
Adv. Mater.
A review on flexible gas sensors: From materials to devices
Sens. Actuators A
Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors
Nat. Mater.
Flexible graphene-based chemical sensors on paper substrates
Phys. Chem. Chem. Phys.
Cited by (90)
Effect of ZnO thickness on gas sensing behavior of WS<inf>2</inf>-ZnO p-n heterojunction nanosheets towards reducing gases
2024, Journal of Alloys and CompoundsMulti-strategy coordination enables WSe<inf>2</inf> to achieve high-performance real-world detection of NO<inf>2</inf>
2024, Sensors and Actuators B: ChemicalDecoration of Pt/Pd bimetallic nanoparticles on Ru-implanted WS<inf>2</inf> nanosheets for acetone sensing studies
2023, Applied Surface ScienceHighly sensitive CO gas sensor based on ternary metal sulfides PbSbS quantum dots: Experimental and DFT study
2023, Journal of Alloys and Compounds
Jae-Hun Kim received his B.S. degree from Gyeongsang National University, Republic of Korea in 2013. In February 2015, he received M.S. degree from Inha University, Republic of Korea. He is now working as a Ph.D. candidate at Inha University, Republic of Korea. He has been working on oxide nanowire gas sensors.
Ali Mirzaei received his Ph.D. degree in Materials Science and Engineering from Shiraz University in 2016. He was visiting student at Messina University, Italy in 2015. Since 2016 he is postdoctoral fellow at Hanyang University in Seoul. He is interested in the synthesis and characterization of nanocomposites for gas sensing applications.
Hyoun Woo Kim joined the Division of Materials Science and Engineering atHanyang University as a full professor in 2011. He received his B.S. and M. S. degreesfrom Seoul National University and his Ph.D. degree from Massachusetts Instituteof Technology (MIT) in electronic materials in 1986, 1988, and 1994, respectively.He was a senior researcher in the Samsung Electronics Co., Ltd. from 1994 to 2000.He has been a professor of materials science and engineering at Inha Universityfrom 2000 to 2010. He was a visiting professor at the Department of Chemistryof the Michigan State University, in 2009. His research interests include the one-dimensional nanostructures, nanosheets, and gas sensors.
Sang Sub Kim joined the Department of Materials Science and Engineering, Inha University, in 2007 as a full professor. He received his B.S. degree from Seoul National University and his M.S and Ph.D. degrees from Pohang University of Science and Technology (POSTECH) in Material Science and Engineering in 1987, 1990, and 1994, respectively. He was a visiting researcher at the National Research in Inorganic Materials (currently NIMS), Japan for 2 years each in 1995 and in 2000. In 2006, he was a visiting professor at Department of Chemistry, University of Alberta, Canada. In 2010, he also served as a cooperative professor at Nagaoka University of Technology, Japan. His research interests include the synthesis and applications of nanomaterials such as nanowires and nanofibers, functional thin films, and surface and interfacial characterizations.