Sm₂O₃ rice-like nanorods decorated on rGO flexible resistive sensor for room temperature LPG detection

Highlights

• Sm₂O₃ rice like nanorods was prepared by ESM-assisted hydrothermal method.

• Sensitivity, stability and selectivity parameters analyzed for Sm₂O₃/rGO sensor towards LPG at RT.

• The sensing mechanism explained based on Chemiresistive model.

Abstract

Flexible electrochemical sensors have gained huge attention over their significant properties and the probability of applying to any wearable electronic devices. LPG traces in definite concentrations leads to a fire accident, adverse health effects, and even causes death. The current study focuses on a flexible, room temperature LPG sensor based on Sm₂O₃/rGO hybrid nanocomposite with different loading factors (1, 3, and 5 wt%) coated on flexible polyethylene terephthalate (PET) substrate working electrodes. Eggshell membrane (ESM) template constituents are acts as a reducing agent during the hydrothermal synthesis of Sm₂O₃ nanorods. Flexible Sm₂O₃/rGO hybrid Chemiresistive gas sensor was tested for various gas sensing parameters. The decoration of Sm₂O₃ nanorods on 3 wt% rGO sheets exhibited good selectivity to liquefied petroleum gas (LPG) at room temperature gives a response of 116% at 700 ppm of LPG with a short response, recovery time and gained 99% response after bending with 94.5% stability of the sensor.

Introduction

The development of thriving day-to-day uses of flexible sensors depending on nanoparticles (NPs) ranging from 1 to 100 nm has gained much significance in various research fields and industrial applications [1]. Consequently, nanomaterials hold both high electron and hole mobility, diaphaneity, flexibility, and their ability to behave as semiconductors will be in immense demand [2]. Flexible sensors are projected to trigger the fabricating of advanced, intelligent system sensing applications in printed electronics [3], medical management [4], gas and chemical sensors [5], environmental and medical sensors [6], fitness monitoring, safety equipment, and sports [7]. Nanoparticle placed flexible sensors are greatly assuring a broad range of functions, still, the essential technology has to be promoted. To date, the utmost flexible sensors depended on solid metal nanoparticles, but an exploration of sensors is expanding in semiconducting hybrid nanocomposites [8], [9], [10]. Present work on fabricating high- performance, the low working temperature at small manufacturing cost gas sensors. The sensor working at low temperature is gaining high attention to provide less power feeding, no need for a heater, hence simplifies the manufacturing of sensors [11].

LPG (liquefied petroleum gas) an odorless, colorless liquid which readily evaporates into a gas and heavier than air also referred as a mixture of aliphatic hydrocarbons such as propane (C₃H₈) and butane (C₄H₁₀) as well as ethyl mercaptan (ethanethiol) in small amounts for odorization to detect leaks [12], which has most uses in cooking [13], vehicle fuel [14], refrigerants [15]. Flammability limit of 1.8–8.8% LPG makes it explosive and has been poisoned due to inhalation and subsequently developed convulsion and reduced level of consciousness [16] hence, room temperature detection is preferable and operationally safe.

Earlier, the sensing materials, such as ZnO, ZnO-ZnSnO₃, ZnFe₂O₄, CeO₂-rGO/CNT, and PVA/hBNNP were used to notice LPG gas at ambient temperature. Yet, most of these articles shown lower sensitivity. For example, Milad et al. stated that the sensitivity of polyaniline/titania for 04 vol% LPG is 43.2% [17]. The maximum sensor sensitivity of the CeO₂-rGO/CNT is 42% for 400-ppm LPG, which is 2.21 times than CeO₂ at room temperature working reported by MSB Reddy et al. [18]. The maximum sensitivity of the sensor on PVA/hBNNP to 1000 ppm in LPG gas reported by J. G. Thangamani et al. is about 25% [19]. For ZnO/PANI by D. Thomas et al. reported high response (~82 towards 400 ppm LPG), with the response time 10 s and recovery time 80 s [20]. Seeking for a significant LPG-sensing material that has higher sensitivity and shorter response-recovery time is desired.

The fabrication of different novel sensors through high response detection or a low limit of detection (LOD) for gas sensing applications, adopting graphene turn it into a popular research area owned to its exceptional electric conductivity [21], high S/V ratio, and high mobility, outstanding mechanical properties like flexibility and elasticity [22], [23] relate to other carbon nanoforms. Regardless the gas sensing response of reduced graphene oxide (graphene) is large and more rapid, though they get intensely distressed by relative humidity at room temperature, lower recovery, and poor selectivity, the limit of detection and repeatability that bounds their real-world application [24]. An interesting concept that has fascinated a pile of interest to this nanomaterial is the initiation of decorating rGO with different metal oxide NPs. By altering, the degree of loading the resulting hybrid nanomaterial properties can be fine-tuned, as well as the NPs decorated on the rGO sheets [25], [26], [27].

Rare earth oxides (REOs) or Lanthanide oxides, has recently been shown great consideration for their well-known applications like ion-glass manufacturing, gas and chemical sensors, microelectronics, and solid fuel cells [28]. The REO used in the present study, i.e. Samarium oxide/Samaria (Sm₂O₃) is a cubic structure below 1870 °C, is characterized as having large interstitial open spaces that have been proven to facilitate its catalytic activity [29]. The attention of the present study is to explain a facile, hydrothermal process for the synthesis of Sm₂O₃ nanorods using eggshell membranes (ESM) as templates and decorated on rGO for (Sm₂O₃/rGO) hybrid material over gentle sonication. ESMs are widely available bio-waste, low cost and eco-friendly materials have semipermeable structure with many functional groups such as amino, carboxyl, carbonyl and aldehydes, and performs as a reducing agent during NPs synthesis. Specified that the Sm₂O₃ nanorods falls in the nanometer scale and enhanced the surface area, to additional understand the effect of the material on the LPG gas sensing performance three separate compositions Sm₂O₃/rGO ratios (1, 3 and 5 wt%) were synthesized and examined.