High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Trioctylphosphine oxide, frequently referred to simply as TOPO, is a chemical compound. TOPO, a tertiary alkylphosphine, can be used as an extraction or stabilizing agent. It is a stable white solid at room temperature. It can be synthesized from phosphorus trichloride, or from a phosphine. It is now frequently used as a capping ligand for quantum dots (e.g. CdSe quantum dots). In these cases, it stabilizes the nanoparticles in organic solvents. TOPO-coated quantum dots are typically soluble in chloroform, toluene, and (to a lesser extent) hexane.