Effect of Al Doping on Sn02 N anoparticles for CO Sensing

Due to the increase in environmental pollution, the monitoring of greenhouse gases became a topic of interest for the damage they cause to the ecosystems and human health. One such harmful gas is carbon monoxide which is highly toxic. In this present work, the sensing of to is done by using thin films of Sn02 and Sn02iAI doped nanoparticles synthetized by sol-gel method, to observe changes in response. The optical characterization was done using DLS and FTIR spectroscopy. For morphological characterization was done using SEM. The crystal structure characterization was done using DRX.

1. Introduction

Nowadays, environmental pollution has become a worldwide problem due to greenhouse gas emissions from the use of vehicles, industries and domestic emissions. Many greenhouse gases are toxic for humans; however, carbon monoxide (CO) has been identified as one of the most dangerous [1]. Ranges from 0 to 500 ppm are used because it is of high interest for human health, as high concentrations are lethal to human health. As the gas concentration increases, the electrical conductivity of Sn02 increases, allowing for gas measurement [2]. Therefore, CO detection is a relevant point of interest to keep the environment and humans' health safe. Considerable research showed that metal-oxide semiconductors (MOS) are reliable and sensitive for gas sensing, for instance, ZnO [3], Pt-doped-ZnO-based [4], CuO [5] and In-doped Sn02 [6]. Tin oxide has become well-studied since it is an n-type and has a band gap of 3.6 e V at 300 K [7]. In addition, Sn02 can achieve an adjustable energy band gap through the doping process. The incorporation of aluminum into the Sn02 crystal structure alters its electrical properties from n-type to p-type [7]. The Al doping makes changes in grain size and substitution of Sn⁴+ ion by Al3+ion in the Sn02 lattice, generating an increase of oxygen vacancy and improving the gas sensing [8]. The sol-gel method offers several notable advantages, including precise compositional control, low-temperature processing, and the capacity to produce materials with tailored surface properties, leading to metal oxides with an increased surface area [9]. The drop casting method is an easy, efficient and fast method driven by the surface tension differential between the solution and substrate [10]. In 2015, Wang et al. reported the synthesis of Sn02 NPs using the co-precipitation method and created thick films for C02 sensing. This study showed that Sn02 NPs are efficient for detecting C02 under specific conditions. However, in dry air environments, the response to this gas was observed to diminish. [11]. Similarly, nanosheets of Sn02 NPs with Pd-Ag decoration have been reported, showing a high sensitivity and selectivity to hydrogen gas [12]. Furthermore, sensors fabricated from thin films of Al-doped Sn02 decorated with Pd NPs demonstrated remarkable selectivity and sensitivity toward the detection of hydrogen gas [8]. While extensive research has been conducted on the interaction of tin oxide nanoparticles with various gases, the literature pertaining to their interaction with carbon monoxide remains relatively limited.