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The purpose of this paper was to develop a chemo-resistive sensor based on TiO₂–WO₃ composite material to detect and estimate ethylene released from the fruit ripening process to ensure food safety.

The ethylene sensor has been fabricated using TiO₂–WO₃ composite material through the sol-gel method.

The sensitivity of the sensor obtained using the pre-calibrated ethylene is found to be 46.2 per cent at 200 ppm ethylene concentration, and the proposed sensor could measure 8 ppm as the lowest concentration.

The sensor was tested for continuous ethylene detection during natural ripening of fruits and hence is useful for ensuring food safety through discrimination of the type of fruit ripening. A TiO₂–WO₃ composite ethylene sensor is developed for the first time.

The production of long-lasting fragrant semi-worsted fabrics using dendritic compounds as one of the nano size materials is concerned. Also quantitative assessments of the odour intensity of the fragrant fabrics using an electronic-nose (E-nose) are made. The paper aims to discuss these issues.

The semi-worsted fabrics were perfumed using the second generation of polypropylene-imine (PPI) dendrimer as a host molecules. The ginseng and rosewater fragrances as guest molecules were applied into the PPI dendrimer to produce long-lasting fragrant fabrics. The odour intensity as well as long-lasting properties of the fragrant fabrics perfumed recently and the other sample perfumed one year ago were evaluated via E-nose fabricated in our laboratory. Physical properties of the fragrant fabrics were compared to the non-fragrant ones.

The interaction between ginseng and rosewater fragrances with the second generation of PPI dendrimer into the semi-worsted fabrics made a long-lasting fragrant fabrics without considerable impacts on bending length, air permeability and wrinkle recovery angles based on statistical analysis. However, the effects of making fragrant fabrics on the increasing weight are significant. In addition, the E-nose was successfully used to monitor the release of ginseng and rosewater fragrance from the fabrics by the response patterns of a temperature-modulated chemo-resistive gas sensor. E-nose analysis showed that the aroma intensity released from the old fragrant semi-worsted fabrics has no obvious diversity from that of new fragrant fabrics.

The findings suggest that the semi-worsted fabrics perfumed with dendritic materials revealed excellent sustained release property.

Artificial fruit ripening is hazardous to mankind. In the recent past, artificial fruit ripening is increasing gradually due to its commercial benefits. To discriminate the type of fruit ripening involved at the vendors’ side, there is a great demand for on-sight ethylene detection in a nondestructive manner. Therefore, this study aims to deal with a comparison of various laboratory and portable methods developed so far with high-performance metrics to identify the ethylene detection at fruit ripening site.

This paper focuses on various types of technologies proposed up to date in ethylene detection, fabrication methods and signal conditioning circuits for ethylene detection in parts per million and parts per billion levels. The authors have already developed an infrared (IR) sensor to detect ethylene and also developed a lab-based setup belonging to the electrochemical sensing methods to detect ethylene for the fruit ripening application.

The authors have developed an electrochemical sensor based on multi-walled carbon nanotubes whose performance is relatively higher than the sensors that were previously reported in terms of material, sensitivity and selectivity. For identifying the best sensing technology for optimization of ethylene detection for fruit ripening discrimination process, authors have developed an IR-based ethylene sensor and also semiconducting metal-oxide ethylene sensor which are all compared with literature-based comparable parameters. This review paper mainly focuses on the potential possibilities for developing portable ethylene sensing devices for investigation applications.

The authors have elaborately discussed the new chemical and physical methods of ethylene detection and quantification from their own developed methods and also the key findings of the methods proposed by fellow researchers working on this field. The authors would like to declare that the extensive analysis carried out in this technical survey could be used for developing a cost-effective and high-performance portable ethylene sensing device for fruit ripening and discrimination applications.

Carbon dioxide (CO₂) has attracted special scientific interest over the last years mainly because of its relation to climate change and indoor air quality. Except for this, CO₂ can be used as an indicator of food freshness, patients’ clinical state and fire detection. Therefore, the accurate monitoring and controlling of CO₂ levels are imperative. The development of highly sensitive, selective and reliable sensors that can efficiently distinguish CO₂ in various conditions of temperature, humidity and other gases’ interference is the subject of intensive research with chemi-resistive zinc oxide (ZnO)-based sensors holding a privileged position. Several ZnO nanostructures have been used in sensing applications because of their versatile features. However, the deficient selectivity and long-term stability remain major concerns, especially when operating at room temperature. This study aims to encompass an extensive study of CO₂ chemi-resistive sensors based on ZnO, introducing the most significant advances of recent years and the best strategies for enhancing ZnO sensing properties.

An overview of the different ZnO nanostructures used for CO₂ sensing and their synthesis methods is presented, focusing on the parameters that highly affect the sensing mechanism and, thus, the performance of CO₂ sensors.

The selectivity and sensitivity of ZnO sensors can be enhanced by adjusting various parameters during their synthesis and by doping or treating ZnO with suitable materials.

This paper summarises the advances in the rapidly evolving field of CO₂ sensing by ZnO sensors and provides research directions for optimised sensors in the future.