Trioctylphosphine:  A General Phosphorus Source for the Low-Temperature Conversion of Metals into Metal Phosphides

Metal phosphides can have important properties such as superconductivity, magnetoresistance, magnetocaloric behavior, catalytic activity, and lithium intercalation capacity, which make them useful for a variety of technological applications. Bulk metal phosphides usually require high temperatures and harsh reaction conditions to form, and metal phosphide nanocrystals can also be challenging to synthesize. Here we elaborate on a recently developed alternative approach for synthesizing metal phosphides, which involves the solution-mediated reaction of pre-formed metals with trioctylphosphine (TOP) at temperatures below 370 °C. This chemical conversion strategy is shown to be general and highly versatile, successfully forming a wide range of transition-metal and post-transition-metal phosphides using a range of both bulk and nanoscale metals as precursors. Metal nanocrystals, bulk powders, foils, wires, thin films, lithographically patterned substrates, and supported nanocrystals can all be converted to metal phosphides by reaction with TOP. Collectively, this represents a general, unified, and robust strategy for forming metal phosphides using readily available reagents and metal precursors.