Abstract
A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness.
Highlights
Estimation of the degree of maturity of fruit at harvest is of great importance because physiologically immature fruits have not completed their growth, while fruit harvested at a far more advanced stage toward or after maturity are more susceptible to disease and deteriorate rapidly [1].Assessment and monitoring of food quality, during both production and storage is of prime importance to enhance its quality at the point of sale
[815 nm (HCl), 810 nm (TSA), 787 nm (CSA), 770 nm (MSA)], indicating that the samples are in the conducting state [23]
All the sensors tested were observed to have excellent reversibility. These results indicate that thin film PANI-emeraldine salt (ES) prepared by in-situ polymerization is a promising material for technological applications such as the development of gas sensors
Summary
Estimation of the degree of maturity of fruit at harvest is of great importance because physiologically immature fruits have not completed their growth, while fruit harvested at a far more advanced stage toward or after maturity are more susceptible to disease and deteriorate rapidly [1]. With the aim of minimizing production losses and preserving the unique features of each fruit, a strategy involving electronic artificial nose systems that use sensors to monitor volatile organic compounds (VOCs) emitted during fruit ripening has been reported [2]. These sensors are non-specific, since their response is an overall profile of the response to the various chemical species present in the VOCs, including ethylene. The degree of doping in the PANI films was investigated by UV-Vis spectroscopy and sensor performance was studied by measuring their electrical properties
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