A Review on Advanced Sensing Materials for Agricultural Gas Sensors

Abstract

This work is a comprehensive review of sensing materials, which interact with several target gases pertinent to agricultural monitoring applications. Sensing materials which interact with carbon dioxide, water vapor (relative humidity), hydrogen sulfide, ethylene and ethanol are the focus of this work. Performance characteristics such as dynamic range, recovery time, operating temperature, long-term stability and method of deposition are discussed to determine the commercial viability of the sensing materials considered in this work. In addition to the sensing materials, deposition methods are considered to obtain the desired sensing material thickness based on the sensor’s mechanism of operation. Various material classes including metal oxides, conductive polymers and carbon allotropes are included in this review. By implementing multiple sensing materials to detect a single target analyte, the issue of selectivity due to cross sensitivity can be mitigated. For this reason, where possible, it is desirable to utilize more than one sensing material to monitor a single target gas. Among those considered in this work, it is observed that PEDOT PSS/graphene and TiO2-coated g-C3N4 NS are best suited for CO2 detection, given their wide dynamic range and modest operating temperature. To monitor the presence of ethylene, BMIM-NTf2, SWCNTs and PtTiO2 offer a dynamic range most suitable for the application and require no active heating. Due to the wide dynamic range offered by SiO2/Si nanowires, this material is best suited for the detection of ethanol; a gas artificially introduced to prolong the shelf life of the harvested crop. Finally, among all other sensing materials investigated, it observed that both SWCNTs and CNTs/SnO2/CuO are most suitable for H2S detection in the given application.

Self-Assembled Corn-Husk-Shaped Fullerene Crystals as Excellent Acid Vapor Sensors

“…Quartz crystal microbalance (QCM) sensing results show the excellent sensing performance of the CHFCs modified QCM electrode sensitive to acetic acid vapors due to the enhanced diffusion via mesoporous architecture and hollow structure of the CHFCs. Thus, these results demonstrate that in addition to the conventional nanomaterials and molecular nanocarbon such as graphene and carbon nanotubes [50][51][52], the corn-husk-shaped fullerene C 60 crystals have the considerable possibility of developing new functional sensor systems for VOC sensing selective to the aliphatic acid vapors.…”

A Review: Application and Implementation of Optic Fibre Sensors for Gas Detection

“…These issues have led researchers to devote their efforts to exploiting materials that react with water vapour. The authors of this review decided not to include coverage of this area, as there are excellent reviews and publications already available [144][145][146] but will briefly mention current research in this area. The focus has been on materials that react to the presence of water vapour.…”

“…Therefore, for standalone and remote environmental monitoring, LOD and resolution needs to be on the order ~0.01% or better. MOS sensors do react with water vapour, but suffer cross-sensitivity with other compounds [145]. Inspecting Table 4, there are potential candidates for atmospheric detection of vapour applications [152,[191][192][193] with approximately the correct LOD and concentration ranges, with the additional advantage of low cross-sensitivity with other substances.…”

“…These devices have produced good results, reasonable resolutions and LOD [196,197] and work at ambient temperature. Chemiresistive sensors have a major drawback which is the LOD, which is not sufficient for the low percentage range of concentrations in the atmosphere and neither is the resolution [145,196,197].…”

Metal-Organic-Frameworks: Low Temperature Gas Sensing and Air Quality Monitoring

“…Sensing materials for gas detection can be classified into metal oxides [16,36,37], conductive and non-conductive polymers [38][39][40][41], carbon-based materials (e.g., graphene, carbon nanotubes, etc.) [42][43][44][45][46], noble metal-based structures [47][48][49][50], ionic liquids [51][52][53], metal-organic frameworks [8,[54][55][56], and their composites [57][58][59]. Among these material groups, metal oxide-based sensors have been investigated extensively due to their strong and rapid response, low limit of detection (LOD), high reproducibility, simple and portable design, and low fabrication cost [60][61][62].…”