Sustainable biomass-based composite biofilm: Sodium alginate, TEMPO-oxidized chitin nanocrystals, and MXene nanosheets for fire-resistant materials and next-generation sensors

Efficient utilization of natural biomass for the development of fireproof materials and next-generation sensors faces various challenges in the field of fire safety and prevention. In this study, renewable sodium alginate (SA), TEMPO-oxidized chitin nanocrystals (TOChNs), and MXene nanosheets were employed to fabricate a sustainable, flexible, and flame-retardant composite biofilm, donated as STM, utilizing a simple and environmentally friendly evaporation-induced self-assembly technique. The incorporation of SA, TOChNs, and MXene in a weight ratio of 50/10/40 led to improved mechanical properties of the resulting STM-40 films, as evidenced by increased tensile strength and Young's modulus values of approximately 36 MPa and 4 GPa, respectively. Notably, these values were approximately 3 and 11 times higher than those observed for the pure SA film. Moreover, the STM-40 films demonstrated highly sensitive fire alarm capabilities, exhibiting a superior flame alarm response time of 0.6 s and a continuous alarm time of approximately 492 s when exposed to flames. The STM exhibited exceptional flame retardancy due to the synergistic carbonization between MXene and SA/TOChNs, resulting in a limiting oxygen index of 45.0 %. Furthermore, its maximum heat release rate decreased by over 90.1 % during the test. This study presents a novel approach for designing and developing fire-retardant fire alarm sensors by utilizing natural biomass.