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Highlights: Graphene oxide-based hybrid networks were fabricated via introducing multi-amino molecule with triple roles (i.e., cross-linker, fire retardant and reducing agent). The optimized hybrid network with mechanically robust, exceptional intumescent effect and ultra-sensitive fire alarm response (~ 0.6 s) can be used as desirable smart fire alarm sensor materials. Exceptional fire shielding performances, e.g., ~ 60% reduction in peak heat release rate and limiting oxygen index of ~ 36.5%, are achieved, when coated such hybrid network onto combustible polymer foam. Smart fire alarm sensor (FAS) materials with mechanically robust, excellent flame retardancy as well as ultra-sensitive temperature-responsive capability are highly attractive platforms for fire safety application. However, most reported FAS materials can hardly provide sensitive, continuous and reliable alarm signal output due to their undesirable temperature-responsive, flame-resistant and mechanical performances. To overcome these hurdles, herein, we utilize the multi-amino molecule, named HCPA, that can serve as triple-roles including cross-linker, fire retardant and reducing agent for decorating graphene oxide (GO) sheets and obtaining the GO/HCPA hybrid networks. Benefiting from the formation of multi-interactions in hybrid network, the optimized GO/HCPA network exhibits significant increment in mechanical strength, e.g., tensile strength and toughness increase of ~ 2.3 and ~ 5.7 times, respectively, compared to the control one. More importantly, based on P and N doping and promoting thermal reduction effect on GO network, the excellent flame retardancy (withstanding ~ 1200 °C flame attack), ultra-fast fire alarm response time (~ 0.6 s) and ultra-long alarming period (> 600 s) are obtained, representing the best comprehensive performance of GO-based FAS counterparts. Furthermore, based on GO/HCPA network, the fireproof coating is constructed and applied in polymer foam and exhibited exceptional fire shielding performance. This work provides a new idea for designing and fabricating desirable FAS materials and fireproof coatings. [ABSTRACT FROM AUTHOR]

Flame-retardant silane-grafted-graphene oxide (silane-GO) papers are fabricated via a green and versatile silane-assisted assembling strategy, and their use as early fire alarm sensors are investigated. Different silane molecules with alkoxy groups can react with GO in aqueous solution via hydrolysis and condensation reactions and thus assemble into the aligned silane-GO papers. The silane-GO papers exhibit good mechanical flexibility, strong acidic/alkaline tolerance, excellent flame resistance and improved thermal stability at low silane content in comparison with pure GO paper. Structure observation and analysis disclose that a compact nano-silica protective layer transformed from the grafted silane molecules during combustion is formed to inhibit the thermal degradation of GO sheet effectively. Furthermore, the insulating silane-GO paper can be thermally reduced into the conductive reduced GO network after encountering high-temperature or flame situation, thus providing ideal early fire alarm response, i.e. rapid flame detecting response time of ∼1.6 s and fire early warning response of ∼5 s when attach on the heat resistor. These results suggest that the silane-GO papers are promising for development of advanced materials as smart sensors in early fire alarm applications. A facile and green silane-assisted assembling technique was developed to fabricate flame-retardant graphene oxide papers, showing fast flame detection and ideal early warning response. Image 1 • A facile silane-assisted assembling strategy was developed to fabricate flame-retardant graphene oxide (silane-GO) papers. • Different silane molecules with alkoxy groups were assembled well onto the aligned silane-GO papers. • The silane-GO papers exhibited good mechanical flexibility, strong acidic/alkaline tolerance, and excellent thermal stability and flame resistance. • The related flame-retardant mechanisms were analyzed and discussed. • The silane-GO papers showed fast fire alarm response due to temperature-triggered sensitive resistance transition, showing promising for fire safety and prevention. [ABSTRACT FROM AUTHOR]

Fire safety and prevention of combustible materials are of paramount importance in modern society but have been a global challenge. Frequent fire disasters cause massive casualties and irreparable property losses and negatively impact the global environment. A recent increasing concern is to develop smart fire warning materials and sensors that combine traditional passive flame retardant strategies and active fire alarm response. However, there still lacks an incisive and comparative overview of such fire warning systems. This review comprehensively discusses passive flame retardant materials, traditional active fire warning sensors, and next-generation smart fire warning materials and sensors, in addition to the flammability of combustible materials. The conceptual design, synthesis, characterizations, and fabrication strategies of smart warning materials are systematically reviewed. Subsequently, the performance and applications of different fire warning sensor systems, including resistance-type, phase/shape change, thermoelectric responsive and colour-change observation, were reviewed and compared to understand their features and working mechanisms better. Finally, some key challenges associated with fire warning materials/sensors are highlighted, following which future perspectives and opportunities are proposed. [Display omitted] [ABSTRACT FROM AUTHOR]

Two natural biomass derivatives i.e., tannic acid (TA) and phosphorylated-cellulose nanofibrils (P-CNFs) were employed to decorate graphene oxide network and the as-prepared flame-retardant GTP paper with ultrasensitive fire alarm response can be applied as desirable smart fire alarm sensor material. [Display omitted] • Biomass-derivatives decorated graphene oxide networks were fabricated via a facile strategy. • The synergistic reinforcing effect was formed in the hybrid networks based on bionic design. • The bio-based hybrid networks showed excellent flame resistance and structural stability. • Ultrasensitive fire alarm time of < 1 s and desirable fire early warning responses were achieved. • Such hybrid networks can be used as sustainable fireproof and fire alarm sensor materials. Effective utilization of natural biomass-derivatives for developing sustainable, mechanically robust, and fireproof materials remains a huge challenge in fire safety and prevention field. Herein, based on bionic design, the hybrid interconnected networks composed of two-dimensional (2D) graphene oxide (GO) nanosheets, renewable one-dimensional (1D) phosphorylated-cellulose nanofibrils (P-CNFs) and tannic acid molecules (TA) were prepared via a green and facile evaporation-induced self-assembly strategy. Through construction of the multiple synergistic interactions among the TA, P-CNFs and GO, the optimized 1D/2D interconnected networks with hierarchical nacre-like structure were achieved and exhibited improved mechanical properties (tensile strength and Young's modulus up to ∼ 132 MPa and ∼ 7 GPa, i.e. ∼ 3.6 and ∼ 14 times higher than that of the pure GO paper), good structural stability in various environments (aqueous solutions with different pH values), excellent flame retardancy (keeping structural integrity after flame attack), and ultrasensitive fire alarm functions (e.g., ultrafast flame alarm time of < 1 s and sensitive fire warning responses). Further, such 1D/2D interconnected networks can act as effective flame-retardant nanocoatings to significantly improve the flame retardancy of combustible PU foam materials (e.g., ∼48% decrease in peak heat release rate at only 10 wt% content). Based on the structure observation and analysis, the related synergistic reinforcing and flame-retardant mechanisms were proposed and clarified. Clearly, this work provides a new route for design and development of environmentally friendly fireproof and fire alarm materials based on utilization of natural biomass-derivatives. [ABSTRACT FROM AUTHOR]

Historically, fire disasters have killed numerous human lives, and caused tremendous property loss. Fire warning systems play a vital role in predicting fire risks, and are strongly desired to effectively prevent the disaster occurrence and significantly reduce the loss. Among the developed fire warning systems, thermoelectrics (TEs) and thermocells (TECs)-based fire warning materials are extremely important and indispensable in future research, owing to their unique capability of direct conversion between heat and electricity. Here, we present this review of the recent progress of TEs and TECs in fire warning field. Firstly, a brief introduction of existing fire warning systems is provided, including the mechanisms and features of various types. Then, the mechanisms of electronic TE (eTE), ionic TE (iTE) and TEC are elucidated. Next, the basic principles for the material preparation and device fabrication are discussed in their dimension sequence. Subsequently, some important advances or examples of TE fire warnings are highlighted in details. Finally, the challenges and prospects are outlooked. [ABSTRACT FROM AUTHOR]

[Display omitted] An abundance of early warning graphene-based nano-materials and sensors have been developed to avoid and prevent the critical fire risk of combustible materials. However, there are still some limitations that should be addressed, such as the black color, high-cost and single fire warning response of graphene-based fire warning materials. Herein, we report an unexpected montmorillonite (MMT)-based intelligent fire warning materials that have excellent fire cyclic warning performance and reliable flame retardancy. Combining phenyltriethoxysilane (PTES) molecules, poly(p-phenylene benzobisoxazole) nanofiber (PBONF), and layers of MMT to form a silane crosslinked 3D nanonetwork system, the homologous PTES decorated MMT-PBONF nanocomposites are designed and fabricated via a sol–gel process and low temperature self-assembly method. The optimized nanocomposite paper shows good mechanical flexibility (good recovery after kneading or bending process), high tensile strength of ∼81 MPa and good water resistance. Furthermore, the nanocomposite paper exhibits high-temperature flame resistance (almost unchanged structure and size after 120 s combustion), sensitive flame alarm response (∼0.3 s response once exposure onto a flame), cyclic fire warning performance (>40 cycles), and adaptability to complex fire situations (several fire attack and evacuation scenarios), showing promising applications for monitoring the critical fire risk of combustible materials. Therefore, this work paves a rational way for design and fabrication of MMT-based smart fire warning materials that combine excellent flame shielding and sensitive fire alarm functions. [ABSTRACT FROM AUTHOR]

Fire safety and protection are very important but still show a critical global challenge. Developing smart fire warning materials with combined passive flame retardancy and active fire alarm response is promising for reducing or avoiding serious fire disasters. Various nano-fillers (e.g., graphene oxide and MXene) based composite coatings have proven to be effective for monitoring critical fire risk of various combustible materials; however, they still show some shortages, for example, high cost, black color, poor weather resistance and complicated fabricating process. Here, we report a green, cost-effective and large-scale strategy for fabricating water-based 3D-titania/2D-montmorillonite/1D-celluose nanofiber (TiO 2 /MMT/CNF) hierarchical nanocomposite coatings with adjustable color, mechanical robustness, good flame retardancy, long-term weather resistance and sensitive fire cyclic alarming response. The formation of strong chemical bonding and hydrogen bonding interactions among polyethylene glycol molecules and multi-scale nano-fillers together with silane surface modification can produce good mechanical flexibility (folded crane), surface hydrophobicity (water contact angle of 152°) and exceptional flame resistance (good structure integrity after 120 s flame exposure). Notably, the optimized nanocomposite coatings exhibit ultrafast fire alarm response (<3.5 s) and stable fire cyclic alarming capability via the possible band transition of the TiO 2 network under flame. Further, such color-adjustable nanocomposite coatings can be easily fabricated for large-scale production, and they show excellent stable flame retardancy and stable fire cyclic warning response even after more than one-year outdoor exposure. This work provides a promising and green fire-warning nanocomposite coatings with combined passive-active functionalities for fire warning and protection. • Water-based nanocomposite coatings are fabricated by a facile and green approach. • Hierarchical TiO 2 /MMT/CNF interconnected networks are constructed and optimized. • The hybrid coatings exhibit good flame resistance and sensitive fire cyclic warning. • Color adjustable, weather resistant and stable outdoor fire warning are demonstrated. [ABSTRACT FROM AUTHOR]

• Silane and LAA co-crosslinked GO network was prepared via a facile strategy. • The hybrid GO network shows good structure stability and improved flame retardancy. • LAA promotes thermal reduction of GO, thus providing efficient fire alarm response. • Flame-retardant mechanisms and fire alarm behaviors were discussed and clarified. Frequent fire disasters have not only caused massive casualties, irreparable property and priceless artefacts loss, but also create severe environmental damage. Therefore, it is imperative, but also challenging, to obtain excellent fire resistance and efficient early-warning alarm response in precombustion of combustible materials. In this work, a green flame-retardant graphene oxide (GO) based paper/coating is designed and constructed via using a facile 3-methacryloxypropyltrimethoxysilane and L-ascorbic acid (LAA) co-functionalization strategy. The optimized co-modified GO network shows good structure stability and improves the flame retardancy of combustible materials. Further, such GO network can provide an ultrafast flame detection signal of only ~1 s and ideal fire early warning responses (e.g. a low responsive temperature of ~120 °C and an extremely rapid responsive time of ~7 s at 300 °C) in precombustion which are among the best performances of the state-of-the-art fire alarm sensors. Moreover, the transformation of silane molecules into a compact protective layer on sheets and the resistance transition of insulating GO network into conductive reduced GO path promoted by LAA molecules are clarified. This work provides a novel strategy and paradigm to achieving excellent flame resistance and ideal fire early warning response of GO network for fire safety and prevention applications. [ABSTRACT FROM AUTHOR]