Hierarchical layered double hydroxides with Ag nanoparticle modification for ethanol sensing

Abstract

Layered double hydroxides (LDHs) have recently been revealed to be promising in gas sensor applications due to their compositional flexibility and unique 2D-interlayer channel for gas diffusion and adsorption. This work demonstrates highly porous hierarchical LDHs containing Mg and Al (MgAl-LDHs) for ethanol sensing at room temperature. These MgAl-LDHs, with unique flower-like hierarchical structure and mesoporous interlayer, were synthesized hydrothermally using sodium dodecyl sulfate as soft template as well as intercalating agent. Further modification by discrete Ag nanoparticles (NPs) was achieved via an environmentally friendly glucose-reduction method to improve the gas-sensing response of the LDH-based sensor. It is found that the hierarchical MgAl-LDHs show potential in sensing ethanol gas with rapid dynamic characteristics at room temperature; their response magnitude towards ethanol can be enhanced significantly by Ag NP modification. The gas-response value of the Ag-modified MgAl-LDH sensor is about twice that of pristine MgAl-LDH sensors, towards 5-200 ppm ethanol at room temperature. Meanwhile, rapid response-recovery characteristics are achieved, with response and recovery times shorter than 10 and 50 s, respectively. The satisfactory sensing performance and remarkable response enhancement by Ag NP modification are demonstrated in terms of the unique microstructure of the hierarchical MgAl-LDHs and a constructed conductive effect model of Ag functionalized LDHs.

Layered Double Hydroxide-Based Gas Sensors for VOC Detection at Room Temperature

“…This result can be correlated with the morphology of the material, since a larger M 3+ content leads to smaller nanosheet aggregates. 45,61 In general, the size is related to nucleation and growth rates, since as the former increases and the latter decreases the size of grains gets smaller and vice versa. A high Al content leads to an increase in the number of available nucleation sites, therefore implying a high nucleation rate and smaller grain sizes.…”

“…Among all of the contaminants in air, volatile organic compounds (VOCs) such as acetone, ethanol, and ammonia vapors are the most common and hazardous. Even at very low concentrations these molecules not only pollute the environment, but also directly affect human health and climate change. ,, Commercial gas sensors are based on different transduction mechanisms and materials, which include polymers, − metal oxides, − or nanocomposites. ,,− The most common are the ones based on metal oxide semiconductors, which require high working temperatures to obtain good sensitivities, fast response, and selectivity. ,, Morandi et al fabricated a CH 4 sensor using Pt/Zn/Al-LDH operating at 450 °C . This entails an increase in power consumption and device complexities, and it is unfavorable for device stability and flammable or explosive environments.…”

“…Within this context, to the best of our knowledge, LDHs have been successfully used as chemiresistive gas sensors especially for the detection of NO x , ,,− ,,− but most of them are insensitive to VOCs. ,,,,,,, Therefore, the possibility of employing miniaturized sensors based on LDHs for the detection of traces of VOCs represents a great advantage in many aspects, owing to their versatility in both chemical composition and structural morphology. In addition, the high porosity allows LDHs to show adjustable interlayer gallery pathways for atoms and molecules, enabling a fast diffusion and carrier transportation through the entire particle bulk and, at the same time, the short-range order allows a fast hole-trapping process where electrons can transfer within unit sheets freely and sufficiently until reaching the sheet edges, improving sensitivity, selectivity, stability, response, and recovery time …”

“…LDHs to show adjustable interlayer gallery pathways for atoms and molecules, enabling a fast diffusion and carrier transportation through the entire particle bulk 45 and, at the same time, the short-range order allows a fast hole-trapping process where electrons can transfer within unit sheets freely and sufficiently until reaching the sheet edges, improving sensitivity, selectivity, stability, response, and recovery time. 50 The present work aims to provide an accurate investigation of the gas-sensing behaviors of these materials.…”

S-Vacancies and Ag Nanoparticles in SnS2 Nanoflakes for Ethanol Sensing: A Combined Experimental and Theoretical Investigation

“…Ag/SnS 2 and Ag/Vs-SnS 2 were synthesized by a glucose-induced method . In a typical experiment, 0.5 g SnS 2 (or V s -SnS 2 ) was dispersed into 50 mL deionized water, stirred, and heated continuously.…”