Ultrasensitive yttrium modified tin oxide thin film based sub-ppb level NO2 detector
Introduction
Amid the COVID-19 (coronavirus disease of 2019) crisis, the deleterious effects of rising air pollution have been observed in every corner of the world. The satellite images have revealed that with just few months of lockdown, the nitrogen dioxide (NO2) levels were slashed by as much as 40 % over Asia and Europe in comparison to that in 2019 for a brief period. Nevertheless, even with the implementation of strict regulations and stringent measurements, a current report indicates that nearly 98 % of cities in low-income countries fail to meet World Health Organization (WHO) air quality standards, and approximately 3 million people lost their lives each year from pollution-related ailments [1]. Thus, the development of low-cost, easy-to-use and effective gas monitors is critical for averting these life-threatening diseases as well as environmental monitoring.
Until very recently, the prevailing air quality monitoring devices were expensive, bulky, have high working temperatures and low-resolution. Nonetheless, current research trends show that this paradigm is changing at a fast pace with the development of portable, room temperature, low power gas sensors which can detect trace concentration (∼ sub-ppb) of gaseous vapours [[2], [3], [4]]. Towards this end, numerous investigations have been made to find a suitable material possessing these qualities for gas sensing applications. Apparently, tin oxide (SnO2) is a promising material which has attracted wide attention owing to its unique properties such as low toxicity, small size, high charge carrier mobility, wide bandgap, high chemical and thermal stability [5,6]. As it can detect a variety of gases with high sensitivity in a short time, it has been widely explored as a versatile gas sensor. However, traditional SnO2 based sensors have a higher detection limit (DL) normally in the ppm range, higher operating temperatures (150–300 °C) and cross-sensitivity issues, which limits their extensive use.
In view of this, various strategies like doping, nano-structuring, hetero-structuring, self-doping, etc. have been adopted to achieve low working temperatures and enhanced selectivity along with low DL [2,3,7,8]. Among these, the introduction of different valence atoms such as Zn, Pt, Pd, etc. into the SnO2 matrix has been identified as an effective and simple approach to enhance the sensing properties [[9], [10], [11], [12]]. As an example, Pengjian Wang et al. was successful in reducing the DL down to 100 ppb towards H2S with extraordinary stability and low response/recovery time by loading W into ultrafine SnO2 nanoparticles [4]. The observed results have been owed to the reduction in particle size and tuning of the electronic bandgap of SnO2. Lately, rare earth elements (Gd, Er, Y, Ce, etc.) have been used to alter the optical and electrical properties of SnO2 [[13], [14], [15], [16], [17]]. These elements promote gas adsorption by increasing the catalytic activity and creating structural defects like oxygen vacancies (OVs) and tin interstitials (Sni) in host lattice, which in turn modifies the adsorption/desorption properties of the surface. For instance, the loading of Dy in SnO2 nanoparticles reduced the operating temperature by 50 °C and also enhanced the sensing response towards ethanol [18]. A similar result has been obtained with Gd-doped SnO2 thick films where the improved sensing characteristics towards ethanol have been attributed to high surface basicity, small crystallite size and abundant OVs [15]. Reduction in DL to as low as 1 ppm towards formaldehyde has been achieved with Y modified SnO2 flower-like nanostructures; however, the device still performs best at 180 °C [17]. A brief literature review of rare earth doped SnO2 gas sensors has been given in Table 1. Thus, despite these findings, the potential of rare earths in developing low-power SnO2 sensors having low DL has not been fully exploited.
This work is targeted to fabricate 3 wt% Y incorporated SnO2 thin film room temperature (RT) sensor with a sub-ppb experimental detection limit. The sensor showed excellent sensing properties with high selectivity towards NO2 in comparison to undoped SnO2 sensor. The high quality undoped and doped SnO2 thin films (50–150 nm) have been prepared using the electron-beam deposition technique and later characterized by various structural and spectroscopic techniques.
Section snippets
Materials and method
All the precursors including tin chloride pentahydrate (SnCl4·5H2O), yttrium nitrate pentahydrate (Y(NO3)3·5H2O) and ammonium hydroxide (NH4OH) were obtained from Sigma-Aldrich Chem. Co. Ltd. The chemicals and reagents were subsequently used without any further purification throughout the experiment.
Synthesis of pure and Y-doped SnO2 nanoparticles
The facile and low-cost co-precipitation method was used to synthesize pure, 1, 3 and 5 wt% Y-doped SnO2 nanoparticles. In a typical experiment, optimum amount of SnCl4·5H2O was dissolved in 100 mL
Morphological and structural studies
Fig. 1 shows the FESEM micrographs of SnO2 thin films with different doping concentrations. The 1PS thin film is smooth and crystalline with interjoined grains, however with 1% Y addition, distinctive grains start to appear implying the successful incorporation of Y. For 3% Y-doped thin film sample, in addition to the clearly separated grains, reduction in their size was also observed. With excessive doping in 5YS sample, the quality and granular structure of the film was destroyed, and instead
Conclusions
In summary, highly sensitive, selective and reliable Y-doped SnO2 thin film-based RT sensors have been successfully fabricated using physical vapour deposition technique. It has been found that the Y incorporation significantly enhances the sensing performance of the SnO2 sensor towards NO2. The 3 wt% Y-doping improved the sensing response from 19 % to 1445 %, reduced the τres and τrec to few minutes. Notably, the 3YS sensor exhibited outstanding sensitivity towards 0.6 ppb NO2 with 26 %
CRediT authorship contribution statement
Manreet Kaur Sohal: Data curation, Formal analysis, Investigation, Methodology, Writing - original draft. Aman Mahajan: Conceptualization, Methodology, Project administration, Supervision, Visualization, Writing - review & editing. Sahil Gasso: Data curation, Writing - review & editing. R.K. Bedi: Conceptualization. Ravi Chand Singh: Project administration, Supervision. A.K. Debnath: Investigation. D.K. Aswal: Investigation.
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.
Acknowledgements
The authors are thankful to DST, New Delhi, for providing financial support through Project No. INT/UKP/P-21/2018 in support of the present research work.
Manreet Kaur Sohal received her Bachelor’s and Master’s degree in Physics from Guru Nanak Dev University, Amritsar, India. She is presently working as a research associate in the Department of Physics from the same university. Her research interests lie in the fabrication and characterization of chemiresistive metal oxide thin films based gas sensors.
References (47)
- et al.
p-N heterostructural sensor with SnO-SnO2 for fast NO2 sensing response properties at room temperature
Sens. Actuators B Chem.
(2018) - et al.
Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature
Sens. Actuators B Chem.
(2019) - et al.
Enhanced methane sensing property of flower-like SnO2 doped by Pt nanoparticles: a combined experimental and first-principle study
Sens. Actuators B Chem.
(2019) - et al.
Highly sensitive and selective electronic sensor based on Co catalyzed SnO2 nanospheres for acetone detection
Sens. Actuators B Chem.
(2020) - et al.
Gold nanoparticles incorporated SnO2 thin film: highly responsive and selective detection of NO2 at room temperature
Mater. Lett.
(2018) - et al.
Highly sensitive formaldehyde resistive sensor based on a single Er-doped SnO2 nanobelt
Physica B Condens. Matter
(2016) - et al.
Synthesis of Ce-doped SnO2 nanoparticles and their acetone gas sensing properties
Appl. Surf. Sci.
(2017) - et al.
Synthesis and characterization of Gd-doped SnO2 nanostructures and their enhanced gas sensing properties
Ceram. Int.
(2017) - et al.
Highly sensitive formaldehyde gas sensors based on Y-doped SnO2 hierarchical flower-shaped nanostructures
J. Alloys Compd.
(2019) - et al.
Fabrication of Pr-doped SnO2 spherical core-shell nanostructure with wrinkly shell and the gas sensing properties
Mater. Lett.
(2017)
Effect of crystallite size, Raman surface modes and surface basicity on the gas sensing behavior of terbium-doped SnO2 nanoparticles
Ceram. Int.
Preparation of Yb-doped SnO2 hollow nanofibers with an enhanced ethanol–gas sensing performance by electrospinning
Sens. Actuators B Chem.
Surface defect and gas-sensing performance of the well-aligned Sm-doped SnO2 nanoarrays
Mater. Lett.
A comparative study between different alternatives to prepare gaseous standards for calibrating UV-Ion Mobility Spectrometers
Talanta
Enhanced UV emission of Y-doped ZnO nanoparticles
Appl. Surf. Sci.
High-performance acetone gas sensor based on Ru-doped SnO2 nanofibers
Sens. Actuators B Chem.
Structural and photoluminescence characterization of SnO2: F thin films deposited by advanced spray pyrolysis technique at low substrate temperature
J. Lumin.
Enhancing NO2 gas sensing performances at room temperature based on reduced graphene oxide-ZnO nanoparticles hybrids
Sens. Actuators B Chem.
Enhanced room temperature sensing of Co3O4-intercalated reduced graphene oxide based gas sensors
Sens. Actuators B Chem.
Synthesis of WO3 nanorods by thermal oxidation technique for NO2 gas sensing application
Mater. Sci. Semicond. Process.
Low-temperature wet chemical synthesis strategy of In2O3 for selective detection of NO2 down to ppb levels
J. Alloys Compd.
Highly sensitive NO2 sensors based on organic field effect transistors with Al2O3/PMMA bilayer dielectrics by sol-spin coating
Org. Electron.
Simple self-assembly of 3D laminated CuO/SnO2 hybrid for the detection of triethylamine
Chinese Chem. Lett.
Cited by (0)
Manreet Kaur Sohal received her Bachelor’s and Master’s degree in Physics from Guru Nanak Dev University, Amritsar, India. She is presently working as a research associate in the Department of Physics from the same university. Her research interests lie in the fabrication and characterization of chemiresistive metal oxide thin films based gas sensors.
Dr. Aman Mahajan received his M.Sc. degree (1997) and Ph.D. (2003) in Physics from Guru Nanak Dev University, Amritsar, India. He is presently working as an assistant professor in the same university. His main interests are preparation and characterization of organic and metal oxide thin films for OLEDs, sensors and photovoltaic applications.
Sahil Gasso received his Bachelor in Non-medical degree from Punjabi University, Patiala, India, in the year 2015 and Master’s degree in Physics from School of Physics and Material Sciences, Thapar University, Patiala, India. Presently, he is working towards his Ph.D. degree in the Department of Physics, Guru Nanak Dev University, Amritsar, India. His research interests are preparation and characterization of metal oxide thin films based gas sensors.
Dr. R. K. Bedi is a Ph.D. and retired professor from the Department of Physics, Guru Nanak Dev University Amritsar, India. He has held academic positions such as Head of Department, Dean, Science faculty and other administrative positions in the university. His research interests are material Science, thin films, photovoltaics and sensors. He is a fellow of The Institution of Electronics and Telecommunication Engineers (IETE). Presently, he is Director, SIET, Amritsar, India.
Dr. Ravi Chand Singh received his Ph.D. in Physics from Guru Nanak Dev University, Amritsar, India, in 1989. Since then, he has had an appointment at the same institute for one year and moved to a post-doctoral position at Simon Fraser University, Canada in 1990. He joined Guru Nanak Dev University Amritsar in 1993. He is presently working as a Professor of Physics. His research interests are material research for gas sensing and the development of new experiments for physics education.
Dr. A. K. Debnath is presently working as Scientific Officer (G) at Technical Physics Division of BARC. He has extensively worked on oxide materials based gas sensor, particularly for H2S detection. His current research interest is to understand the charge transport and gas sensing properties of ultra-thin films of organic semiconductor grown using MBE.
Dr. D. K. Aswal joined BARC in 1986 and served as Head, Thin Films Devices Section. At, present he is Director, CSIR- National Physical Laboratory, New Delhi, India. His current area of research interests includes physics of organic films and their applications for solar cells, conducting polymer films for flexible electronics, thermoelectric power generators and gas sensors and electronic nose. He is a recipient of several international fellowships including, JSPS fellowship, Japan (1997–1999), IFCPAR fellowship, France (2004–2005), BMBF fellowship, Germany (2006) and CEA fellowship, France (2008). He is recipient of several awards, including “MRSI Medal 2010”, “Homi Bhabha Science and Technology Award-2007”, “DAE-SRC Outstanding Research Investigator Award-2008”, and “Paraj: Excellence in Science Award, 2000”.