Surface chemistry of as-synthesized and air-oxidized PbS quantum dots
Surface chemistry of as-synthesized and air-oxidized PbS quantum dots
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DOI：
10.1016/j.apsusc.2018.06.152
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发表时间：
2018-11-01
影响因子：
6.7
通讯作者：
van Veggel, Frank C. J. M.
中科院分区：
文献类型：
--
作者：
Beygi, Hossein;Sajjadi, Seyed Abdolkarim;van Veggel, Frank C. J. M.
本文报道了理论和实验研究，解释了尺寸依赖的形状和元素组成的PbS量子点（QD）的影响量子点表面吸附配体的排列和密度，以及它们的相关敏感性氧化。通过考虑颗粒的Pb：S比的差异，我们预测了与我们的测量结果一致的尺寸相关的Pb：S比，以及文献中报道的Pb：S比。我们进一步连接的形状和小面Pb：S组合物的表面配体密度，并与此相关的颗粒大小的氧化时，暴露在空气中的依赖性。虽然较小颗粒（d <2.7nm）的表面完全被Pb终止的（111）面覆盖，但较大QD（2.7 < d <7.5nm）在其（100）面处被截断以形成立方八面体形状的颗粒。代表较小和较大颗粒表面的最大部分的（111）小面可以被阴离子油酸盐/氢氧化物配体很好地钝化。通过FT-IR、NMR、XPS和燃烧元素分析以及空间稳定性考虑对PbS QD的表面化学的研究表明，PbS QD的（111）面中的氢氧化物与油酸盐的原子比为约1：5。在另一侧，（1 0 0）表面刻面具有铅和硫原子的棋盘式排列，并由油酸配体配位。这种配体的低密度和弱结合能使得（100）面在空气气氛中容易氧化。XPS研究表明，氧化物包括PbS量子点表面上的PbSO 3和PbSO 4组分。
This paper reports theoretical and experimental studies that explain how the size-dependent shape and elemental composition of PbS quantum dots (QDs) affect the arrangement and density of adsorbed ligands by QDs surfaces, and their related susceptibility to oxidation. By considering the differences of Pb:S ratios of the particles, we predict a size-dependent Pb:S ratio that is consistent with our measurements, and those reported in the literature. We further connect the shape and facet Pb:S composition to surface ligand densities, and relate this to the particle-size dependence of oxidation when exposed to air. While the surfaces of smaller particles (d < 2.7 nm) are entirely covered by Pb terminated (1 1 1) facets, bigger QDs (2.7 < d < 7.5 nm) are truncated at their (1 00) facets to form cuboctahedron-shape particles. The (1 1 1) facets representing the largest portion of both smaller and bigger particle's surfaces can be well-passivated by anionic oleate/hydroxide ligands. Investigation on the surface chemistry of PbS QDs by the means of FT-IR, NMR, XPS and combustion elemental analyses, as well as steric stability considerations suggested that hydroxide to oleate atomic ratio in (1 1 1) facet of PbS QDs is about 1:5. On the other side, (1 0 0) surface facets have a checkerboard arrangement of lead and sulfur atoms and are coordinated by oleic acid ligands. Low density and weak binding energy of such ligands make the (1 0 0) facets vulnerable to oxidation in an air atmosphere. XPS investigations indicate that the oxide includes both PbSO3 and PbSO4 components on the surface of PbS QDs.