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In Situ 1 H NMR Study on the Trioctylphosphine Oxide Capping of Colloidal InP Nanocrystals
Author(s) -
Hens Zeger,
Moreels Iwan,
Martins Jose C.
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500182
Subject(s) - trioctylphosphine oxide , nanocrystal , chemistry , steric effects , spectroscopy , colloid , adsorption , nuclear magnetic resonance spectroscopy , analytical chemistry (journal) , resonance (particle physics) , two dimensional nuclear magnetic resonance spectroscopy , crystallography , materials science , stereochemistry , nanotechnology , organic chemistry , atomic physics , physics , quantum mechanics , extraction (chemistry)
We used trioctylphosphine oxide (TOPO) capped colloidal InP nanocrystals (Q‐InP|TOPO) to explore the potential of solution 1 H NMR spectroscopy in studying in situ the capping and capping exchange of sterically stabilized colloidal nanocrystals. The spectrum of Q‐InP|TOPO shows resonances of free TOPO, superimposed on broadened spectral features. The latter were assigned to TOPO adsorbed at Q‐InP by means of pulsed field gradient diffusion NMR and 1 H‐ 13 C HSQC spectroscopy. The diffusion coefficient of Q‐InP|TOPO nanocrystals was inferred from the decay of the adsorbed TOPO NMR signal. The corresponding hydrodynamic diameter correlates well with the diameter of Q‐InP. By using the resolved methyl resonance of adsorbed TOPO, the packing density of TOPO at the InP surface can be estimated. Spectral hole burning was used to demonstrate explicitly that the adsorbed TOPO resonances are heterogeneously broadened. Exchange of the TOPO capping by pyridine was demonstrated by the disappearance of the resonances for adsorbed TOPO and the appearance of pyridine resonances in the 1 H NMR spectrum. These results show that solution NMR spectroscopy should be considered a powerful technique for the in situ study of the capping of sterically stabilized colloidal nanocrystals.