SnO2Nanoparticle-Based Passive Capacitive Sensor for Ethylene Detection

Mangilal Agarwal,Mercyma D Balachandran,Sudhir Shrestha,Kody Varahramyan

doi:10.1155/2012/145406

Abstract

A passive capacitor-based ethylene sensor using SnO2nanoparticles is presented for the detection of ethylene gas. The nanoscale particle size (10 nm to 15 nm) and film thickness (1300 nm) of the sensing dielectric layer in the capacitor model aid in sensing ethylene at room temperature and eliminate the need for microhotplates used in existing bulk SnO2-resistive sensors. The SnO2-sensing layer is deposited using room temperature dip coating process on flexible polyimide substrates with copper as the top and bottom plates of the capacitor. The capacitive sensor fabricated with SnO2nanoparticles as the dielectric showed a total decrease in capacitance of 5 pF when ethylene gas concentration was increased from 0 to 100 ppm. A 7 pF decrease in capacitance was achieved by introducing a 10 nm layer of platinum (Pt) and palladium (Pd) alloy deposited on the SnO2layer. This also improved the response time by 40%, recovery time by 28%, and selectivity of the sensor to ethylene mixed in a CO2gas environment by 66%.

Highlights

In the United States, almost 23 percent wastage of fruit occurs every year in the postharvest handling [1]
Ε0 εr A1 d where, ε0 is the permittivity of free space, εr is the dielectric constant of SnO2 nanoparticles, A1 is the area of the dielectric, that is, sum of the total depletion region of the nanoparticles and the dielectric regions between nanoparticles before exposure to ethylene gas, and d is the thickness of the dielectric region
The ethylene gas concentration from 0 ppm to 100 ppm was used for testing purpose

Summary

Introduction

In the United States, almost 23 percent wastage of fruit occurs every year in the postharvest handling [1]. Ethylene gas is the key factor for initiating the ripening process in climacteric fruits and for accelerating the aging process, thereby reducing the quality and shelf life of production during postharvest transits. Climacteric fruits, such as, apples, peaches tend to emit different concentrations of ethylene at various stages of ripening [2, 3]. The active sensing layer is tin dioxide used as the dielectric material, fabricated at room temperature using low-cost dip coating technique or layer-by-layer (LbL) self-assembly technique [19]. The passive nature of the SnO2 capacitive ethylene sensor aids in the integrated with a triangular microstrip patch antenna which represents a one of a kind passive wireless sensor tag used for detecting freshness of climacteric fruit [23]

Theory

Fabrication

Results and Discussions

Conclusion