A New Strategy for Detecting Plant Hormone Ethylene Using Oxide Semiconductor Chemiresistors: Exceptional Gas Selectivity and Response Tailored by Nanoscale Cr₂O₃ Catalytic Overlayer

Abstract

A highly selective and sensitive detection of the plant hormone ethylene, particularly at low concentrations, is essential for controlling the growth, development, and senescence of plants, as well as for ripening of fruits. However, this remains challenging because of the non‐polarity and low reactivity of ethylene. Herein, a strategy for detecting ethylene at a sub‐ppm‐level is proposed by using oxide semiconductor chemiresistors with a nanoscale oxide catalytic overlayer. The SnO2 sensor coated with the nanoscale catalytic Cr2O3 overlayer exhibits rapid sensing kinetics, good stability, and an unprecedentedly high ethylene selectivity with exceptional gas response (Ra/Rg − 1, where Ra represents the resistance in air and Rg represents the resistance in gas) of 16.8 at an ethylene concentration of 2.5 ppm at 350 °C. The sensing mechanism underlying the ultraselective and highly sensitive ethylene detection in the unique bilayer sensor is systematically investigated with regard to the location, configuration, and thickness of the catalytic Cr2O3 overlayer. The mechanism involves the effective catalytic oxidation of interfering gases into less‐ or non‐reactive species, without limiting the analyte gas transport. The sensor exhibits a promising potential for achieving a precise quantitative assessment of the ripening of five different fruits.

Exclusive and ultrasensitive detection of formaldehyde at room temperature using a flexible and monolithic chemiresistive sensor

“…Furthermore, it is challenging to find catalysts for the highly selective promotion of the formaldehyde sensing reaction or to design a catalytic filtering layer to oxidize only ethanol without oxidizing formaldehyde. Indeed, the catalytic filtering layer formed on the top of the sensing film decreased both responses to ethanol and formaldehyde 17 , 18 . This means that the exclusive detection of formaldehyde via catalyst loading or by using a catalytic filtering layer is highly challenging even in photo-assisted gas sensing at room temperature, which requires a new strategy such as molecular sieving.…”

“…The loading of various catalysts or the compositional control of sensing materials have been explored but have led to the enhancement of the responses toward ethanol and formaldehyde 13 – 16 . Furthermore because ethanol and formaldehyde exhibit similarly high reactivity, it is difficult to eliminate only ethanol through oxidative filtering using an catalytic overlayer 17 , 18 . In this perspective, the exclusive detection of trace formaldehyde using oxide chemiresistors has been a long-standing challenge.…”

Nanomaterials for IoT Sensing Platforms and Point-of-Care Applications in South Korea

“…In addition to their application of a wireless gas-sensing platform in POCT, such sensors are employed in IoT-based sensor systems for monitoring food quality in the agricultural industry [91][92][93]. For example, SnO 2 hollow spheres were synthesized with a nanoscale Cr 2 O 3 catalytic overlayer for improved selectivity toward ethylene, which is an important plant hormone used to determine the development and growth of climacteric fruits [92]. The overall fabrication process for the Cr 2 O 3 -SnO 2 sensor is illustrated in Figure 7i.…”

Electronic and Simple Oscillatory Conduction in Ferrite Gas Sensors: Gas-Sensing Mechanisms, Long-Term Gas Monitoring, Heat Transfer, and Other Anomalies

“…Chemiresistive gas sensors based on metal-oxide semiconductors are fast gaining traction in the food market. 1 Their colossal sensitivity comes with complicated processes that require clear explanation. Interestingly, sensors for liquefied petroleum gas (LPG) that rely on the rare-earth cobalt-and magnesium-based surfaces present very pronounced oscillatory-sensing behavior.…”

“…Many situations arise to detect and monitor hazardous gases or volatile organic compounds which require real-time measurements. Chemiresistive gas sensors based on metal-oxide semiconductors are fast gaining traction in the food market . Their colossal sensitivity comes with complicated processes that require clear explanation.…”