Wurtzite CdSe quantum belts having Z-type ligation, such as {CdSe[Cd(oleate)2]0.19} QBs, undergo facile ligation exchange with AX salts (A = R4N, Na; X = OH, Cl, Br, NO3, OBz, OAc) to afford quantum belts having bound-ion-pair X-type ligation and empirical formulas CdSe[X]x[A]x. Exchange to AX ligation is accompanied by shifts of the quantum-belt absorption spectra by as large as 340 meV (for X = OH) relative to the spectrum of L-type {CdSe[n-octylamine]0.53} QBs. The AX ligation appears to consist of two populations, one for which the AX ligands are persistently bound, and another for which the AX ligands are readily removed by washing. These generate two ligation stoichiometries referred to as depleted and saturated ligation, respectively. The empirical formulas for depleted ligation are in the approximate range of CdSe[X]0.1-0.3[A]0.1-0.3, whereas those for saturated ligation are in the approximate range of CdSe[X]0.4-0.8[A]0.4-0.8. These ranges are consistent with approximately one and two X- ligands per three-coordinate surface Cd atom, respectively. AX ligation is readily exchanged to either L-type primary amine or Z-type Cd(oleate)2 ligation. However, AX salts do not displace L-type primary amine ligation under the conditions studied. All ligation exchanges are rapid and complete at room temperature, and with the exception of L-type to bound-ion-pair X-type ligation, fully reversible.

Interchange of L-, Z-, and bound-ion-pair X-type ligation on cadmium selenide quantum belts

2019 Spring National Meeting

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