The Surface Chemistry of Colloidal Nanocrystals Capped by Organic Ligands

Abstract

Nanocrystal surface chemistry is a pivotal element in the synthesis and application of nanocrystals. This perspective focuses on colloidal nanocrystals, capped with organic ligands. We start with insights into a workhorse characterization technique: solution nuclear magnetic resonance (NMR) spectroscopy. We then discuss the different models used to conceptualize nanocrystal surface chemistry and how the classification of binding motifs helps in the prediction of surface reactions. The thermodynamics and kinetics of these surface reactions are analyzed, and we arrive at the deciding factors for a high binding affinity: sterics, pK a/pK b, and solubility/solvent. Finally, we discuss recent ligand designs; most notably we introduce a new ligand class: monoalkyl phosphinic acids.

Insights into the Unanticipated Chemical Reactivity of Functionalized Nanosheets Derived from TiB2

“…De Roo suggests that this coordination can lead to changes in the peak width of NMR spectra, as seen in the case of CdSe nanocrystals capped with oleate ligand. 59 De Roo further explains that depending upon the size of the ligand and the nanomaterial, it might become hard to detect the attached ligand by NMR. 60,61 As the NS are large in lateral dimensions and also provide a large surface area, in our results we too observe something similar; the peak around 8 ppm for m-NS has almost become imperceptible, although the other peaks are relatively easy to observe; this suggests that this particular enediol group is closest to the NS surface and the chemical interaction happens through this group.…”

Phase transition behaviour and mechanism of 2D TiO2(B) nanosheets through water-mediated removal of surface ligands

“…S2†), which implies a surface-bound structure. 30 EG was introduced in the synthesis as a reagent, solvent and also protecting agent to stabilize the product. The EG ligands were chemically adsorbed, as they cannot be removed through repeated washing.…”

Effect of the bulkiness of alkyl ligands on the excited-state dynamics of ZnO nanocrystals

“…Recent detailed studies of organic ligands have revealed that a slight difference in the molecular structure of aliphatic ligands significantly affects the dispersibility of the NCs. 10–13 Moreover, it has also been reported that the dispersibility and emission properties of NCs are altered by changing the primary, secondary, and tertiary structures of the phosphonic acids and thiols. 14 However, there are few examples that reveal the effect of the molecular structure of alkyl ligands on the excited-state dynamics of NCs.…”