Mechanically flexible graphene oxide network for highly-sensitive and ultra-long fire warning

Graphene oxide (GO)-based intelligent fire alarm sensor (FAS) has recently been a sought-after research topic in fire prevention fields. However, it remains a challenge to facilely construct GO-based composite that simultaneously possess mechanical flexibility, excellent flame resistance, highly-sensitive temperature-responsive behavior, rapid fire response and ultra-long fire alarming durability. Here, a nacre-like ternary hybrid paper is conveniently obtained by integrating GO with hexachlorophosphazene-based multi‑hydroxyl molecule (HHACP) and tannic acid (TA) via a facile and eco-friendly water evaporation-induced self-assembly method. The resultant composite paper (TA-GO/HHACP) exhibits mechanically flexible property with tensile strength of 103.7 MPa and toughness of 1.51 MJ/m3, comparable to 2.52 and 5.39 times higher than those of pure GO paper. Further, the TA-GO/HHACP paper displays excellent nonflammability and high-temperature resistance that can withstand continuous butane flame attack (∼ 1200 °C), resulting in ultra-long sustained alarming period of > 1600 s under an open fire. More importantly, benefiting from its rapid electrical resistance reduction capability, such TA-GO/HHACP paper demonstrates ultra-fast fire-triggered response time of ∼ 0.6 s, and ultra-sensitive early fire alarm responses to abnormal high temperatures during pre-combustion process, e.g., ∼ 1 s at 250 °C and ∼ 19 s at 200 °C, respectively, outperforming the best reported GO‑based FAS counterparts. This work provides an inventive paradigm to develop high-performance GO-based intelligent materials with reliable and sensitive early fire-warning function.