title: Spectroscopic identification of tri-n-octylphosphine oxide (TOPO) impurities and elucidation of their roles in cadmium selenide quantum-wire growth.
abstract: Tri-n-octylphosphine oxide (TOPO) is the most commonly used solvent for the synthesis of colloidal nanocrystals. Here we show that the use of different batches of commercially obtained TOPO solvent introduces significant variability into the outcomes of CdSe quantum-wire syntheses. This irreproducibility is attributed to varying amounts of phosphorus-containing impurities in the different TOPO batches. We employ (31)P NMR to identify 10 of the common TOPO impurities. Their beneficial, harmful, or negligible effects on quantum-wire growth are determined. The impurity di-n-octylphosphinic acid (DOPA) is found to be the important beneficial TOPO impurity for the reproducible growth of high-quality CdSe quantum wires. DOPA is shown to beneficially modify precursor reactivity through ligand substitution. The other significant TOPO impurities are ranked according to their abilities to similarly influence precursor reactivity. The results are likely of general relevance to most nanocrystal syntheses conducted in TOPO.
authors.affiliation: Department of Chemistry and Center for Materials Innovation, Washington University, Saint Louis, Missouri 63130-4899, USA.
authors.forename: Fudong
authors.initials: F
authors.lastname: Wang
authors.forename: Rui
authors.initials: R
authors.lastname: Tang
authors.forename: Jeff L-F
authors.initials: JL
authors.lastname: Kao
authors.forename: Sean D
authors.initials: SD
authors.lastname: Dingman
authors.forename: William E
authors.initials: WE
authors.lastname: Buhro
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure; D009943:Organophosphorus Compounds / Q000032:analysis / Q000737:chemistry; D010721:Phosphinic Acids / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis; D018036:Selenium Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D008024:Ligands; D009943:Organophosphorus Compounds; D010721:Phosphinic Acids; D018036:Selenium Compounds; D010758:Phosphorus; C044965:trioctyl phosphine oxide; C058667:cadmium selenide