Mechanistic study of precursor evolution in colloidal group II-VI semiconductor nanocrystal synthesis
Mechanistic study of precursor evolution in colloidal group II-VI semiconductor nanocrystal synthesis
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DOI：
10.1021/ja0656696
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发表时间：
2007-01-17
影响因子：
15
通讯作者：
Alivisatos, A. Paul
中科院分区：
文献类型：
--
作者：
Liu, Haitao;Owen, Jonathan S.;Alivisatos, A. Paul
采用H-1、C-13和P-31核磁共振谱和质谱研究了胶体II-VI族半导体纳米晶体合成中前驱体演变的分子机制。三丁基膦硫属元素化物（TBPE; E = S、Se、Te）与镉或锌的油酸配合物（M-OA; M = Zn、Cd）在非配位溶剂（十八碳烯（ODE）、正壬烷-d（20）或正癸烷-d（22））中反应，得到ME纳米晶体、三丁基氧化膦（TBPO）和油酸酐（（OA）（2）O）。类似地，三烷基硒化膦与正十八烷基膦酸镉络合物（Cd-ODPA）在三正辛基氧化膦（TOPO）中的反应产生CdSe纳米晶体、三烷基氧化膦和正十八烷基膦酸的酸酐。在Cd-OA和Cd-ODPA存在下，三正辛基硒化膦的消失可以拟合为单指数衰减（k（obs）=（1.30 +/- 0.08）x 10（-3）s（-1），Cd-ODPA，260 ℃，和k（obs）=（1.51 +/- 0.04）x 10（-3）s（-1），Cd-OA，117 ℃）。反应在无水条件下以70-80%的TOPSe转化率和在添加的水存在下以100%的转化率接近完成。在358-400 K范围内，由TBPSe衰减的温度依赖性确定了TBPSe与Cd-OA在正壬烷-d（20）中反应的活化参数（Δ H = 62.0 +/-2.8 kJ中心点mol（-1），Δ S = -145 +/-8 J中心点mol（-1）中心点K-1）。提出了三烷基膦硫族化合物与油酸或膦酸表面活性剂脱附生成三烷基氧化膦和油酸或膦酸酸酐产物的反应机理。动力学实验结果表明，磷硫族化合物双键（TOPE）的裂解是通过膦酸酯或油酸酯对（TOPE）M络合物的亲核攻击进行的，产生初始的M-E键。
The molecular mechanism of precursor evolution in the synthesis of colloidal group II-VI semiconductor nanocrystals was studied using H-1, C-13, and P-31 NMR spectroscopy and mass spectrometry. Tri-n-butylphosphine chalcogenides (TBPE; E = S, Se, Te) react with an oleic acid complex of cadmium or zinc (M-OA; M = Zn, Cd) in a noncoordinating solvent (octadecene (ODE), n-nonane-d(20), or n-decane-d(22)), affording ME nanocrystals, tri-n-butylphosphine oxide (TBPO), and oleic acid anhydride ((OA)(2)O). Likewise, the reaction between trialkylphosphine selenide and cadmium n-octadecylphosphonic acid complex (Cd-ODPA) in tri-n-octylphosphine oxide (TOPO) produces CdSe nanocrystals, trialkylphosphine oxide, and anhydrides of n-octadecylphosphonic acid. The disappearance of tri-n-octylphosphine selenide in the presence of Cd-OA and Cd-ODPA can be fit to a single-exponential decay (k(obs) = (1.30 +/- 0.08) x 10(-3) s(-1), Cd-ODPA, 260 degrees C, and k(obs) = (1.51 +/- 0.04) x 10(-3) s(-1), Cd-OA, 117 degrees C). The reaction approaches completion at 70-80% conversion of TOPSe under anhydrous conditions and 100% conversion in the presence of added water. Activation parameters for the reaction between TBPSe and Cd-OA in n-nonane-d(20) were determined from the temperature dependence of the TBPSe decay over the range of 358-400 K (Delta H = 62.0 +/- 2.8 kJ center dot mol(-1), Delta S = -145 +/- 8 J center dot mol(-1)center dot K-1). A reaction mechanism is proposed where trialkylphsophine chalcogenides deoxygenate the oleic acid or phosphonic acid surfactant to generate trialkylphosphine oxide and oleic or phosphonic acid anhydride products. Results from kinetics experiments suggest that cleavage of the phosphorus chalcogenide double bond (TOPE) proceeds by the nucleophilic attack of phosphonate or oleate on a (TOPE)M complex, generating the initial M-E bond.