An understanding of the nanocrystal-ligand interface is paramount for any optoelectronic devices or biological labels based on these materials. Here, we quantitatively study the initial binding events on 5.0 nm oleic-acid capped CdS nanocrystals (NC). This is done by correlating the change in CdS Photoluminescence (PL), which is due to flourescence resonance energy transfer (FRET) from the CdS donor to an acceptor, a specially designed dye functionalized with a carboxylic group. This work first reveals the initial binding events between cadmium chalcogenide NCs and carboxylic acid groups. Until now, quantitative study at such low concentrations has been hindered by the high concentration required by NMR, and the spectroscopically silent nature of the carboxylic acid group in photoluminescence-based studies. A good fit was obtained from our model for both the experimental steady-state and time-resolved photoluminescence data by assuming a Poissonian binding distribution. A modified Langmuir isotherm involving a ligand with one binding group to identical, multiple binding sites on the surface of CdS NC can describe the binding behavior well. Specifically, there are an average of 3 new carboxylic acid ligands on the CdS surface with a binding constant, Ka, of 4.7�105 M-1

Quantifying the initial carboxylic acid ligand exchange events on CdS nanocrystals

248th National Meeting (2014)

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