Aging populations and the increase in chronic diseases worldwide demand efficient healthcare tools for simple, rapid, and accurate diagnosis and monitoring the human health. In this context, gas sensors are used to analyze the type of gas in the breath to diagnose chronic diseases. Metal oxide and ceramic nanofibers (NFs) produced by the electrospinning (ES) method have been investigated for potential use as gas sensors in the engineering and medical sectors. The material and process parameters are the main influencing factors on the functional performance of electrospun metal oxide NFs. Zinc oxide (ZnO) based NFs are used in various gas sensors due to the wide band gap (3.37eV), large exciton binding energy, and high mobility of charge carriers of ZnO. In this research, we made an attempt to study the effect of poly(vinyl alcohol) (PVA) and zinc acetate dihydrate (ZnAc₂) concentrations and feed rate, voltage, spinneret tip-to-collector distance (TCD), and pyrolysis temperature on the physical properties of ZnO NFs. An average fiber diameter of 119 nm was obtained after pyrolysis at 600 °C of electrospun fiber produced from an aqueous PVA solution of concentration 15 w% with 7.5 w% ZnAc₂ based on the weight of PVA. The grain size, transmittance, structural defects, and band gap energy of NFs were found to increase as a function of the pyrolysis temperature, which could be beneficial for the functional applications of these NFs.

Fibre-reinforced polymer composites incorporating synthetic reinforcements such as glass and carbon fibres are widely used due to their superior mechanical performance. However, their energy-intensive production and end-of-life disposal contribute to an increased carbon footprint and significant environmental burden. Natural fibre-reinforced composites have emerged as promising low impact alternatives, but variability in their mechanical performance and the lack of controlled comparative studies limit their structural application. This study presents a controlled experimental comparison of alkaline-treated unidirectional flax/epoxy and hemp/epoxy composites fabricated using the vacuum-assisted resin infusion moulding (VARIM) process. Alkali treatment was employed to enhance the fibre–matrix interfacial bonding. Mechanical characterization was conducted through tensile, flexural, impact, interlaminar shear strength (ILSS), and Vickers microhardness testing in accordance with relevant ASTM and ISO standards. The flax/epoxy composites exhibited superior in-plane mechanical performance including, 9.1% higher tensile modulus, 13.8% higher flexural strength and 20.5% higher flexural modulus compared to hemp/epoxy composites. A significant improvement was observed in impact performance, with hemp composites showing 87.4% higher impact strength, indicating enhanced resistance to dynamic loading. Conversely, hemp/epoxy composites demonstrated a 10.6% higher ILSS, suggesting improved interfacial shear resistance and fibre interlocking. These findings confirm that the fibre type significantly influences composite performance, with flax fibres providing superior stiffness and strength, while hemp fibres offer better interlaminar shear behaviour and impact strength. Scanning Electron Microscopy (SEM) fractographic analysis was additionally conducted on fracture surfaces to characterize failure mechanisms and fibre–matrix interfacial morphology. The present study provides a reliable comparative framework for material selection and demonstrates the potential of flax- and hemp-based composites as sustainable alternatives for lightweight structural applications. This study supports the development of sustainable composite materials and contributes to the United Nations Sustainable Development Goals (SDGs), particularly SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 11 (Sustainable Cities and Communities).