TY - JOUR
T1 - Interchange of L-, Z-, and Bound-Ion-Pair X-Type Ligation on Cadmium Selenide Quantum Belts
AU - Yao, Yuewei
AU - Dekoster, Gregory T.
AU - Buhro, William E.
N1 - Funding Information:
We sincerely thank Prof. Dan Oron (Weizmann Institute of Science) for suggesting chiral ligation and CD spectroscopy to establish the direct surface bonding of anionic X-type ligands. We also thank Prof. Emily A. Weiss (Northwestern University) and Prof. Tianquan Lian (Emory University) for helpful discussions. This work was supported by the National Science Foundation (CHE-1607862). We also acknowledge financial support from Washington University and the Institute of Materials Science and Engineering for the use of instruments and staff assistance.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/6/11
Y1 - 2019/6/11
N2 - Wurtzite CdSe quantum belts (QBs) having Z-type ligation, such as {CdSe[Cd(oleate)2]0.19} QBs, undergo a facile ligation exchange with AX salts (A = R4N, Na; X = OH, Cl, Br, NO3, OBz, OAc) to afford QBs having bound-ion-pair X-type ligation and empirical formulas CdSe[X]x[A]x. The 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. AX ligation is also investigated using the Na+ salts of d- and l-phenylalanine. These chiral X ligands induce inverse chiroptical effects in the circular dichroism spectra corresponding to the electronic transitions of the CdSe QBs, providing a strong evidence of the direct ligation of the X groups on the QB surfaces. AX ligation appears to consist of two populations on the QBs, 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. The empirical formulas for the 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. 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.
AB - Wurtzite CdSe quantum belts (QBs) having Z-type ligation, such as {CdSe[Cd(oleate)2]0.19} QBs, undergo a facile ligation exchange with AX salts (A = R4N, Na; X = OH, Cl, Br, NO3, OBz, OAc) to afford QBs having bound-ion-pair X-type ligation and empirical formulas CdSe[X]x[A]x. The 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. AX ligation is also investigated using the Na+ salts of d- and l-phenylalanine. These chiral X ligands induce inverse chiroptical effects in the circular dichroism spectra corresponding to the electronic transitions of the CdSe QBs, providing a strong evidence of the direct ligation of the X groups on the QB surfaces. AX ligation appears to consist of two populations on the QBs, 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. The empirical formulas for the 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. 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.
UR - http://www.scopus.com/inward/record.url?scp=85067126071&partnerID=8YFLogxK
U2 - 10.1021/acs.chemmater.9b01659
DO - 10.1021/acs.chemmater.9b01659
M3 - Article
AN - SCOPUS:85067126071
VL - 31
SP - 4299
EP - 4312
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 11
ER -