Violet phosphorus: Synthesis, fundamental properties, and emerging applications

Violet phosphorus (VP), a recently identified two-dimensional (2D) allotrope of phosphorus, exhibits a range of distinctive properties that position it as a promising material for diverse advanced applications. This review begins with a detailed examination of the synthesis strategies for VP, including bulk-phase growth, few-layer exfoliation, and the fabrication of VP quantum dots (QDs). Each method's advantages, limitations, and impact on the material's structural and electronic properties are discussed. VP's unique characteristics, such as its tunable direct bandgap, high charge carrier mobility, and anisotropic behavior, enable strong performance in optoelectronics. Applications in polarization-sensitive photodetectors, broadband photodetection, and neuromorphic vision systems are critically reviewed, emphasizing its potential for next-generation photonic devices. In the biomedical domain, VP's biodegradability, tunable optical properties, and promising electronic characteristics provide opportunities for biosensing, antibacterial treatments, and cancer therapy. Finally, VP's potential for energy storage and conversion is explored, with particular attention given to its role in photocatalytic hydrogen evolution and as an anode material in sodium-ion and lithium-ion batteries. The review provides a comprehensive analysis of VP's synthesis, properties, and multifaceted applications, while highlighting the ongoing challenges and future research directions required to fully exploit its potential.