The Effect of Rare Earths on the Response of Photo UV-Activate ZnO Gas Sensors

Abstract

In this work, ZnO nanoparticle resistive sensors decorated with rare earths (REs; including Er, Tb, Eu and Dy) were used at room temperature to detect atmospheric pollutant gases (NO2, CO and CH4). Sensitive films were prepared by drop casting from aqueous solutions of ZnO nanoparticles (NPs) and trivalent RE ions. The sensors were continuously illuminated by ultraviolet light during the detection processes. The effect of photoactivation of the sensitive films was studied, as well as the influence of humidity on the response of the sensors to polluting gases. Comparative studies on the detection properties of the sensors showed how the presence of REs increased the response to the gases detected. Low concentrations of pollutant gases (50 ppb NO2, 1 ppm CO and 3 ppm CH4) were detected at room temperature. The detection mechanisms were then discussed in terms of the possible oxidation-reduction (redox) reaction in both dry and humid air atmospheres.

Gas-Sensing Properties and Mechanisms of 3D Networks Composed of ZnO Tetrapod Micro-Nano Structures at Room Temperature

“…In recent decades, with the advancement of nanoscience and nanotechnology, a diverse range of nano-ZnO gas sensors have been fabricated, including nanowires [ 22 ], nanorods [ 23 ], nanotubes [ 24 ], nanosheets [ 25 ], nanoflowers [ 26 ], and so on. Typically, these sensors function within the temperature range of 150–500 °C or can be operated at room temperature with auxiliary means such as UV light irradiation [ 27 , 28 , 29 ]. However, this approach may lead to increased complexity in fabrication and power consumption, and reduced sensor stability and lifespan, ultimately limiting their widespread applications.…”

Sol–Gel Synthesis of ZnO:Li Thin Films: Impact of Annealing on Structural and Optical Properties

“…The ZnO band gap can be tailored by doping with such materials as Mg [12]. Rare-earth metal doping of ZnO is reported to be an effective way for the adjustment and control of gas-sensing efficiency [13]. Generally, doping alters the ZnO-based materials in view of different applications by enhancing the desired properties through choosing the appropriate dopant.…”

Cobalt- and Copper-Based Chemiresistors for Low Concentration Methane Detection, a Comparison Study

“…In 1968, Taguchi released the first commercially available gas sensor for the detection of hydrocarbons [ 4 ]. Since then, gas sensors, having the advantage of being reduced in size [ 5 ] and also cheap devices that can be mass-produced, were used to monitor environmental pollution, obtain global contamination maps [ 6 ], monitordomestic safety, ensure public security, monitor automotive safety, monitor air quality and more recently, make medical diagnoses, such as exhaled breath analysis [ 7 ]. Gas detectors have been fabricated in many different ways (electrochemical and optical approaches), and solid-state gas sensors contain various gas sensing materials (e.g., metal oxides or MOX).…”

“…For MOX gas sensors, the most widely accepted sensing mechanism can be explained by the resistance change, which is caused by the surface reaction between the target gas and the sensitive material deposited on the surface of the sensor (in this particular case the sensors are named chemiresistors ), upon sensor exposure to different gaseous atmospheres [ 7 ]. Chemiresistors based on semiconductor metal oxides with low-costs, easy production, a compact size and simple electronics are the most widely used in gas detection applications, however, MOX-resistive sensors typically operate at high working temperatures, which limits their application as sensitive materials and leads to sensing material instability, increased power consumption and response drifts [ 6 ]. The key for obtaining an economically viable sensor is mainly the low-cost of the final product, which implies abundant raw materials for the sensor components and low-cost preparation techniques (sol–gel, hydrothermal, etc.)…”