Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, K1A 0R6, Canada.
Small. 2011 Aug 8;7(15):2250-62. doi: 10.1002/smll.201100457. Epub 2011 Jul 7.
In-situ observation of the temporal evolution of the absorption of PbSe nanocrystals (NCs) via a low-temperature noninjection approach is presented. Based on a model reaction of lead oleate (Pb(OA)(2) ) and n-trioctylphosphine selenide (TOPSe) in 1-octadecene at 35-80 °C, the use of commercially available TOP (90 or 97%) in affecting the formation of the NCs is explored. TOPSe solutions made from TOP 90% exhibited higher reactivity than those made from TOP 97%. (31)P NMR spectroscopy detected no dioctylphosphine selenide (DOPSe) but some DOP in ≈1.0 M TOPSe/TOP solution (made from TOP 90%), as well as no diphenylphosphine selenide (DPPSe) when DPP was added to the ≈1.0 M solution. Hence, it is proposed that, for the formation of PbSe monomers, an indirect pathway dominates with the formation of a Pb-P complex/intermediate, which results from the activation of Pb(OA)(2) by a phosphine compound (such as DPP, DOP, or TOP) and in turn reacts with TOPSe. With the use of TOP 90% and the addition of secondary phosphine DPP, the formation of PbSe magic-sized nanoclusters (MSNCs) and regular NCs (RNCs) is investigated. With proper tuning of the synthesis conditions, the formation of various PbSe MSNCs versus RNCs is monitored in situ with versus without the addition of DPP, or at different reaction temperatures but otherwise identical synthetic formulation and reaction parameters. Accordingly, the degree of supersaturation (DS) of the PbSe monomer affecting the development of these PbSe MSNCs versus RNCs is proposed; the higher the DS, the more the MSNCs are favored. Also, surface-determined cluster-cluster aggregation is proposed to be the growth mechanism for both the RNCs and MSNCs. For the former, quantized growth is followed by continuous growth. For the latter, the sizes of the magic-sized families are calculated.
本文通过低温非注入法原位观察了 PbSe 纳米晶体（NCs）的吸收随时间的演变。基于油酸铅（Pb(OA)(2) ）和三辛基膦硒（TOPSe）在 1-十八烯中于 35-80°C 的模型反应，研究了商业可得的 TOP（90%或 97%）对 NCs 形成的影响。由 90%TOP 制成的 TOPSe 溶液显示出比由 97%TOP 制成的 TOPSe 溶液更高的反应性。（31）P NMR 光谱检测到没有二辛基膦硒（DOPSe），但在 ≈1.0 M TOPSe/TOP 溶液（由 90%TOP 制成）中检测到一些 DOP，并且当 DPP 添加到 ≈1.0 M 溶液中时，没有检测到二苯基膦硒（DPPSe）。因此，提出对于 PbSe 单体的形成，主导的是间接途径，其中形成 Pb-P 配合物/中间体，这是由磷化合物（如 DPP、DOP 或 TOP）对 Pb(OA)(2) 的活化而产生的，进而与 TOPSe 反应。使用 90%TOP 和添加第二膦 DPP，研究了 PbSe 魔数纳米团簇（MSNCs）和规则 NCs（RNCs）的形成。通过适当调整合成条件，在没有添加 DPP 的情况下，或在不同的反应温度下，但其他合成配方和反应参数相同的情况下，原位监测了各种 PbSe MSNCs 与 RNCs 的形成。因此，提出了影响这些 PbSe MSNCs 与 RNCs 形成的 PbSe 单体的过饱和度（DS）程度；DS 越高，MSNCs 越有利。此外，还提出表面决定的团簇-团簇聚集是 RNCs 和 MSNCs 生长的机制。对于前者，遵循量化生长，然后是连续生长。对于后者，计算了魔数族的尺寸。
