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Respiratory illness demands pragmatic clinical monitoring and diagnosis to curb numerous fatal diseases in all aged groups. Due to the complicated instrumentation, long amplification periods, and restricted number of simultaneous detections, present clinically available multiplex diagnostic technologies are difficult to deploy the onsite diagnostic platforms. The futuristic assessment of medical diagnosis eases the respiratory monitoring using exhaled breath, due to the simple and comfort non-invasive detecting techniques. Carbon dioxide (CO2) stands as a promising biomarker and has been identified in exhaled breath samples that distinguish different respiratory issues. State-of-the-art CO2 gas sensing strategies are recognized with the growth of modern telecommunication technologies for real-time respiratory illness monitoring and diagnosis using exhaled breath. The presented article reviews the existing CO2 gas sensors and their developments towards medical applications. With that, the advancement of infrared (IR) CO2 gas sensors with distinguished light and sensing properties in detecting respiratory disorders are overviewed. The development of optimal CO2 gas sensing strategy incorporated with Internet of Things (IoT) technology is over-reviewed. The hurdles encountered in the existing research and future preference with real-time CO2 monitoring and diagnosing respiratory disorders with the advancement attained in IR sensing technology and IoT networking are highlighted.

Compatibility of natural fiber with hydrophobic matrix is a herculean task in literature works. Surface treatment is a well-known approach for increasing the strength of interfacial adhesion between fibres and polymer matrices. Therefore, this study aims to examine the impact of surface treatment with zinc oxide nanoparticles (ZnONPs) in improving hydrophobicity of kenaf fiber (KF) to enhance the compatibility between KF and polymer matrix. In this study, KF reinforced unsaturated polyester composites (KF/UPE) were fabricated by the hand lay-up method with varying fiber loadings (wt %) of 10 20, 30, and 40. KF were treated with five different contents of ZnONPs (1% to 5 wt%) to make UPE/KF-ZnONPs composites. The composites were studied in terms of wetting response (contact angle measure and water absorption), mechanical properties, chemical structure (FTIR), crystalline structure (XRD), and surface morphology (SEM, AFM). The investigational findings indicate that the composite samples incorporating ZnONPs exhibit optimum hydrophobicity and mechanical properties, as they possessed a higher contact angle than the untreated KF composite. The optimum content of ZnONPs was found to be 2 wt%. Regarding water absorption, the untreated UPE/KF composites absorbed more water than the treated UPE/KF-ZnONPs composites. SEM images showed changes in the morphology of the KF, while FTIR analysis proved the presence of ZnONPs functional groups in the UPE/KF composites. AFM images revealed that the ZnONPs could actively produce nanolevel roughness, advantageous to the hydrophobic characteristics.