Liquid phase exfoliation of few-layer phosphorene (FL-P) is extensively explored in recent years. Nevertheless, their deficiencies such as ultralong sonication time, limited flake size distribution, and uncontrollable thicknesses are major hurdles for the development of phosphorene-based materials. Herein, electrochemical cationic intercalation has been introduced to prepare phosphorene, through which large-area FL-P without surface functional groups can be efficiently attained (less than 1 h). More importantly, its layer number (from 2 to 11 layers) can be manipulated by changing the applied potential. The as-obtained phosphorene delivers superior sodium-storage performances when directly utilized as an anode material in sodium-ion batteries. This electrochemical cation insertion method to prepare phosphorene should greatly facilitate the development of phosphorene-based technologies. Moreover, this work provides the possibility for the scalable preparation of monolayer 2D materials by exploring intercalation ions. Additionally, the successful electrochemical exfoliation of phosphorene can promote the application of electrochemical exfoliation in other 2D materials.

The design of flame-retardant biocomposites based on biobased flame retardants (FRs) represents a promising direction for creating a sustainable world. To date, it remains a major challenge to explore a green and scalable strategy for the design of highly effective, biobased FRs for bioplastics, such as polylactic acid (PLA). Herein, we have demonstrated a green, facile fabrication approach for a core–shell-structured biobased flame retardant (APP@CS@PA-Na) via layer-by-layer assembly using water as the assembly media. With electrostatic interactions, APP@CS@PA-Na was prepared by sequential assembly of ammonium polyphosphate (APP) with positively charged chitosan (CS) and then negatively charged phytic acid salt (PA-Na). The addition of APP@CS@PA-Na can enhance both the flame retardancy and the toughness of PLA. With the addition of 10 wt % APP@CS@PA-Na, the resultant PLA composite can pass an UL-94 V-0 rating and meanwhile shows an increased elongation at break by 28.4%, compared with that of neat PLA (8.1%). Through the analysis of the volatile gases and the residues, the flame retardant mechanism of APP@CS@PA-Na in PLA plays the key role in the condensed-phase. This work will broaden the practical application field of PLA, such as in electric and electronic and fibers fields.

Covalently functionalized carbon nanotubes (CNTs) wrapped in intumescent flame retardant were successfully fabricated and characterized. By adjusting the ratio of CNTs and flame retardant, the diameter of the functionalized CNTs was effectively controlled to 20-90 nm. Compared with pristine CNTs, the functionalized CNTs are better dispersed in polypropylene (PP) due to the in situ compatibilization reaction between the active groups of the intumescent flame retardant on the CNT surface and the maleic anhydride groups in the compatibilizer, maleic anhydride-grafted polypropylene (PPMA). Incorporating the functionalized CNTs could confer outstanding flame retardancy on PP/ PPMA, and considerably enhance the mechanical properties of the polymeric materials due to the improved interfacial adhesion and stress transfer. Therefore, use of intumescent flame-retardantwrapped carbon nanotubes and in situ compatibilization are promising strategies for simultaneously improving the flame retardancy and mechanical properties of polymeric materials.

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