Solution phase synthesis of the less-known Form II crystalline red phosphorus

The emerging application of crystalline red phosphorus (RP) in optoelectronics such as photocatalysis is bogged down by its limited synthesis routes. Scalable and controllable solution phase methods usually lead to the formation of amorphous RP products. Herein, we developed a facile and mild solvothermal strategy to synthesize highly crystalline RP by selecting 1,2-diaminopropane as an appropriate nucleophilic agent. The diamine-induced "dissolution-crystallization" mechanism was proposed to explain the phosphorus phase transition in solution from amorphous RP, via polyphosphide anions, to crystalline RP. The structure of this crystalline RP was assigned to Form II RP by X-ray diffraction pattern matching and other morphological characterization methods. This novel method to prepare Form II RP may offer a chance for its potential photocatalytic water splitting and the solution phase fabrication of other elemental phosphorus allotropes. Form II crystalline red phosphorus was grown by solvothermal reactions. XRD patterns match well with Roth's results in 1947. Polyphosphide anions captured during phosphorus phase transformation support the "dissolution-crystallization" mechanism.