Understanding the "tailoring synthesis" of CdS nanorods by O2.
Understanding the "tailoring synthesis" of CdS nanorods by O2.
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DOI：
10.1021/ic201119c
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发表时间：
2012-01
影响因子：
4.6
通讯作者：
Guoxin Zhang;Peilei He;Xiuju Ma;Y. Kuang;Junfeng Liu;Xiaoming Sun
中科院分区：
文献类型：
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作者：
Guoxin Zhang;Peilei He;Xiuju Ma;Y. Kuang;Junfeng Liu;Xiaoming Sun
众所周知，在溶剂热合成CdS半导体纳米棒（NRs）的过程中，溶液浓度和环境气氛组成等参数对相和形貌控制很重要，但对所涉及的潜在机制缺乏清晰的认识。在这项工作中，通过一系列实验证明了影响CdS NRs相和形貌的关键因素是密封容器中反应溶液上方空间中O(2)的量相对于溶液中前驱体的量：O(2)贫条件下，立方相CdS和厚多晶NRs较多，其宽高比通常小于3，带边发射蓝移较小，表面陷阱发射较小；而O(2)富条件下，六边形相CdS和薄单晶NRs较多，带边发射蓝移明显，表面陷阱发射较强。因此，增加容器中的溶液量，将环境气氛从空气改为N(2)，以及增加试剂浓度都降低了O(2)与试剂的摩尔比，从而导致更多的立方相和更厚的nr。结果表明，反应容器“空”部分的组成与液体组成在决定相和形态方面起着同样重要的作用，这在早期的工作中被忽视了。在此基础上提出了氧对晶核和生长阶段影响的机理，并通过振荡实验和ZnS - NR合成操作得到了进一步的支持。不同条件下合成的CdS NRs在光催化活性上表现出明显的差异，表明控制合成工艺可以得到具有定制光催化活性的材料。
Parameters such as solution concentrations and composition of the ambient atmosphere are known to be important in phase and morphology control in the solvothermal synthesis of CdS semiconductor nanorods (NRs), but a clear understanding of the underlying mechanisms involved is lacking. In this work, a series of experiments were performed to demonstrate that the key factor affecting the phase and morphology of CdS NRs is the amount of O(2) in the space above the reaction solution in the sealed vessel relative to the amount of precursors in solution: O(2)-depleted conditions resulted in more cubic phase CdS and thick polycrystalline NRs with an aspect ratio usually less than 3, which have small blue shifts in band-edge emission and little surface trap emission, while O(2)-rich conditions resulted in more hexagonal-phase CdS and slim single-crystal NRs, which have significantly blue shifted band-edge emission and relatively strong surface trap emission. Thus, increasing the amount of solution in the vessel, changing the ambient atmosphere from air to N(2), and increasing the reagent concentration all lower the molar ratio of O(2) to reagents and lead to more cubic phase and thicker NRs. The results indicate that the composition of the "empty" section of the reaction vessel plays as important a role as the composition of the liquid in determining the phase and morphology, something that has been overlooked in earlier work. A mechanism to explain the effect of oxygen on the nucleation and growth stages has been proposed on the basis of those results and further supported by shaking experiments and ZnS NR synthesis manipulation. The CdS NRs synthesized under different conditions showed obvious differences in photocatalytic activity, which indicated that controlling the synthetic process can lead to materials with tailored photocatalytic activity.