InP/ZnS Nanocrystals: Coupling NMR and XPS for Fine Surface and Interface Description

Abstract

Advanced (1)H, (13)C, and (31)P solution- and solid-state NMR studies combined with XPS were used to probe, at the molecular scale, the composition (of the core, the shell, and the interface) and the surface chemistry of InP/ZnS core/shell quantum dots prepared via a non-coordinating solvent strategy. The interface between the mismatched InP and ZnS phases is composed of an amorphous mixed oxide phase incorporating InPO(x) (with x = 3 and predominantly 4), In(2)O(3), and InO(y)(OH)(3-2y) (y = 0, 1). Thanks to the analysis of the underlying reaction mechanisms, we demonstrate that the oxidation of the upper part of the InP core is the consequence of oxidative conditions brought by decarboxylative coupling reactions (ketonization). These reactions occur during both the core preparation and the coating process, but according to different mechanisms.

A compact dispersive refocusing Rowland circle X-ray emission spectrometer for laboratory, synchrotron, and XFEL applications

“…Previous literature has also reported oxidized P levels of InP cores close to 10% by XPS and NMR but has shown an increase to approximately 35% after shelling with ZnS. 64 In Fig. 10 (bottom), InP magic-sized clusters were prepared with a phosphonate ligand shell, showing the mixed environment of P 3 from the inorganic core and P 5+ from the organic ligands.…”

Identifying short surface ligands on metal phosphide quantum dots

“…For instance, we have previously shown for InP QDs that PO x (with x = 3 and predominantly 4), In 2 O 3 , and InO y (OH) 3–2 y ( y = 0, 1) species exist at the surface. 8 The formation of these species is the direct consequence of the high oxophilicity of these QDs which react with water existing as a residual impurity in reactants or solvents or coming from side-reactions of ligands at high temperature. Given the extraordinary complexity of these phosphide QDs surface, the full characterization of the surface ligand is not an easy task.…”

“…It has been shown, 8,15 that the analysis of surface QDs using the basic cross-polarization (CP) sequence MAS NMR is of high interest because it brings complementary information to those given by solution NMR: the low motion of the surface ligand can be advantageously used through the CP experiment to enhance the signals which are typically too broad and too weak to be not observable in solution. The CP experiment where magnetization is transferred from a proton nucleus to a spin nucleus of lower sensitivity ( e.g.…”

“…These QDs can be synthesized at RT and thus, side-reactions which are known to occur at high (300 °C) or moderately high (150 °C) temperature are avoided. 8,20 In addition, the surface chemistry of these QDs is versatile and can be modified in order to introduce various ligands and to test the limits of this method.…”

Doping Group IIB Metal Ions into Quantum Dot Shells via the One‐Pot Decomposition of Metal‐Dithiocarbamates

“…Hg containing samples used the Hg4d area between 350 and 385 eV rather than the more conventional Hg4f or Hg5d due to masking elements, particularly Si2p masking of Hg4f, as all QD samples for analysis were mounted on glass prior to analysis (figure 3). [39][40][41][42] [ Figure 3]…”