GOLD NANOPARTICLES AND SENSOR TECHNOLOGY FOR SENSITIVE ETHYLENE DETECTION

Abstract

A new electrocatalytic sensor for measurement of gaseous ethylene (C2H4) concentration in air is presented. The measuring principle is based on ethylene oxidation on a gold-Nafion anode with weak sulphuric acid used as the electrolyte. The small ethylene molecules are trapped in the pores of the nanoporous gold matrix and partly consumed to produce the signal proportional to their concentration in air. The high surface area of the nanoporous gold catalyst renders high sensitivity and fast response in detection of ethylene in air making it particularly suitable for postharvest or plant physiology applications. In the current study, the accuracy was 96-98% with a SD of 0.05-0.15 ppm C2H4 and a variation coefficient of 0.5-2%, when the calibration gas of 8 ppm C2H4 was measured after calibration. The measuring range of the device is 0 -50 ppm C2H4 with an accuracy of ±5% of reading and displayed resolution of 1 ppb. For a 30 sec measurement, the instrument draws a ca. 150 ml gas sample and appears suitable for measurement of individual fruit in an open or closed gas system, for continuous sampling or single gas samples. Temperature, humidity, CO2 (option) and another gas or ethylene analogue like MCP (option) are displayed concomitantly. The reproducibility of the values was 93% with 3 subsequent measurements of a variety of fruits. The unit can be operated on mains or built-in battery providing up to 8 hours operation and weighs 4.5 kg. This makes it portable for in-situ ethylene measurement after calibration with an external gas supply and is elegant alternative to ethylene determination in a 10 ml sample from head space of jar after hours of accumulation by gas chromatography.