Multilayer porous Pd-WO3 composite thin films prepared by sol-gel process for hydrogen sensing

2020

Nanomaterials

The influence of sensitive porous films obtained by pulsed laser deposition (PLD) on the response of surface acoustic wave (SAW) sensors on hydrogen at room temperature (RT) was studied. Monolayer films of TiO 2 and bilayer films of Pd/TiO 2 were deposited on the quartz substrates of SAW sensors. By varying the oxygen and argon pressure in the PLD deposition chamber, different morphologies of the sensitive films were obtained, which were analyzed based on scanning electron microscopy (SEM) images. SAW sensors were realized with different porosity degrees, and these were tested at different hydrogen concentrations. It has been confirmed that the high porosity of the film and the bilayer structure leads to a higher frequency shift and allow the possibility to make tests at lower concentrations. Thus, the best sensor, Pd-1500/TiO 2 -600, with the deposition pressure of 600 mTorr for TiO 2 and 1500 mTorr for Pd, had a frequency shift of 1.8 kHz at 2% hydrogen concentration, a sensitivity of 0.10 Hz/ppm and a limit of detection (LOD) of 1210 ppm. SAW sensors based on such porous films allow the detection of hydrogen but also of other gases at RT, and by PLD method such sensitive porous and nanostructured films can be easily developed.

Section: Introductionmentioning

confidence: 99%

Development of Pd/TiO2 Porous Layers by Pulsed Laser Deposition for Surface Acoustic Wave H2 Gas Sensor

2020

Nanomaterials

“…Han et al [ 14 ] developed Pd-WO 3 multilayer composite films by the sol-gel method. Using Pluronic F127 as template, the porosity of the films increased, offering a larger specific surface area, favorable for gas detection.…”

Section: Synthesis Methodsmentioning

confidence: 99%

“…Up to a concentration of 4%, hydrogen has no risk of flammability or explosion. Above this value, the risk of inflammation increases, and at even higher concentrations, it becomes explosive [ 9 , 13 , 14 , 15 ]. It must also be taken into account that hydrogen has a very small molecule with a high coefficient of diffusion in air (0.6 cm 2 /s at 0 °C), being thus capable of permeating many materials [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

Synthesis Methods of Obtaining Materials for Hydrogen Sensors

2021

Sensors

The development of hydrogen sensors has acquired a great interest from researchers for safety in fields such as chemical industry, metallurgy, pharmaceutics or power generation, as well as due to hydrogen’s introduction as fuel in vehicles. Several types of sensors have been developed for hydrogen detection, including resistive, surface acoustic wave, optical or conductometric sensors. The properties of the material of the sensitive area of the sensor are of great importance for establishing its performance. Besides the nature of the material, an important role for its final properties is played by the synthesis method used and the parameters used during the synthesis. The present paper highlights recent results in the field of hydrogen detection, obtained using four of the well-known synthesis and deposition methods: sol-gel, co-precipitation, spin-coating and pulsed laser deposition (PLD). Sensors with very good results have been achieved by these methods, which gives an encouraging perspective for their use in obtaining commercial hydrogen sensors and their application in common areas for society.

“…For all types of sensors, including SAW sensors, it is important to operate at RT, and at the same time, to ensure that a signal is obtained at the lowest analyte concentrations. The reference metal oxide semiconductors used in the domain of sensors include In 2 O 3 [ 34 , 107 , 108 , 109 , 110 ], ZnO [ 45 , 111 , 112 , 113 ], Co 3 O 4 [ 114 , 115 , 116 ], SnO 2 [ 99 , 117 ], CuO/Cu 2 O [ 100 , 118 ], TiO 2 [ 24 , 119 ], NiO [ 58 , 120 ], Fe 2 O 3 [ 121 , 122 ], and WO 3 [ 23 , 123 ]. They were most often used to detect volatile organic compounds, hydrogen, ammonia, etc.…”

Section: Sensitive Materials Used In Gas Detectionmentioning

confidence: 99%

“…A considerable advantage of this type of sensor is that it is versatile, which allows for adaptation to different applications [ 21 ]. SAW sensors are used for the detection of gases [ 22 , 23 , 24 ], as well as for the detection of liquids or other changes in the environment, such as pressure [ 25 ], humidity [ 26 ], the presence of UV radiation [ 27 ], and for chemical and biological applications [ 28 , 29 ]. In this work, we focused on the study of SAW sensors for gas detection.…”

Section: Introductionmentioning

confidence: 99%

ZnO Metal Oxide Semiconductor in Surface Acoustic Wave Sensors: A Review

2020

Sensors

Surface acoustic wave (SAW) gas sensors are of continuous development interest to researchers due to their sensitivity, short detection time, and reliability. Among the most used materials to achieve the sensitive film of SAW sensors are metal oxide semiconductors, which are highlighted by thermal and chemical stability, by the presence on their surface of free electrons and also by the possibility of being used in different morphologies. For different types of gases, certain metal oxide semiconductors are used, and ZnO is an important representative for this category of materials in the field of sensors. Having a great potential for the development of SAW sensors, the discussion related to the development of the sensitivity of metal oxide semiconductors, especially ZnO, by the synthesis method or by obtaining new materials, is suitable and necessary to have an overview of the latest results in this domain.