Effect of linker on the photosensitization of ZnO layers with CdSe quantum dots
Effect of linker on the photosensitization of ZnO layers with CdSe quantum dots
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连接剂对 CdSe 量子点 ZnO 层光敏化的影响
DOI：
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发表时间：
2011
影响因子：
2.4
通讯作者：
Ashutosh Kumar Singh
中科院分区：
文献类型：
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作者：
Aneeta Kharkwal;S. Sharma;S. Chand;Ashutosh Kumar Singh
在这项工作中，氧化锌 (ZnO) 纳米颗粒（尺寸 <10 nm）是通过乙醇溶液中的沉淀形成的。将乙酸锌和氢氧化锂的乙醇溶液在 273 K 温度下剧烈搅拌混合。为了研究量子点 (QD) 覆盖的影响，我们通过化学途径制备了封端 CdSe QD（尺寸约 5 nm）的胶体悬浮液，并通过直接吸附或通过连接剂将它们锚定到纳米多孔 ZnO 层上。在此，双功能分子（巯基丙酸，MPA 和巯基乙酸，TGA）预先吸附在 ZnO 表面上，充当分子电缆。从 TEM/SEM 研究中发现，CdSe QD 直接吸附到 ZnO 表面上效率不高。然而，双功能连接分子，特别是 MPA，有利于 CdSe QD 与 ZnO 的结合；因此，粒子间的电子转移变得容易。 MPA 连接体尽管具有长碳链，但其使用也有助于以更系统的方式猝灭添加 ZnO 时的 CdSe 光致发光，表明分别与没有连接体和有连接体 TGA 的情况相比，从 CdSe 到 ZnO 的有效电荷转移。由于更高的 PL 猝灭和寿命值的降低，与 TGA 连接体和无连接体情况相比，具有 MPA 的 CdSe-ZnO 复合材料分别获得了更高的 Stern-Volmer 猝灭常数值。对于没有连接体情况的样品观察到的非线性 Stern-Volmer 图表明由于 CdSe QD 和 ZnO 之间的结合不足而导致异质猝灭。通过光谱（PL、UV-VIS、FTIR）和显微（TEM、SEM）技术，我们证明了带有 CdSe 量子点的 ZnO 层的依赖于连接体的光敏化机制。因此，我们的数据表明，QD-连接体-ZnO 组装体中的界面电子转移动力学几乎与含烷基分子连接体的长度无关。
In this work, zinc oxide (ZnO) nanoparticles (size <10 nm) were formed via precipitation in ethanolic solution. The zinc acetate and lithium hydroxide solutions in ethanol were mixed at 273 K temperatures under vigorous stirring. To study the effect of quantum dot (QD) coverage, we have prepared a colloidal suspension of capped CdSe QDs (size ~5 nm) by chemical route and anchored them to a nanoporous ZnO layer either by direct adsorption or through linker. Here a bifunctional molecule (mercaptopropionic acid, MPA, and thioglycolic acid, TGA) was previously adsorbed on the ZnO surface, which acted as a molecular cable. From TEM/SEM studies, it was observed that direct adsorption of CdSe QDs onto ZnO surface was not efficient. However, the bifunctional linker molecules particularly MPA facilitates binding of CdSe QDs to ZnO; and consequently, interparticle electron transfer is thus facilitated. The use of MPA linker despite of its long carbon chain also aids in the quenching of photoluminescence of CdSe on addition of ZnO in a more systematic manner indicating efficient charge transfer from CdSe into ZnO as compared with the without linker and with linker TGA case, respectively. Due to higher PL quenching and reduction in lifetime values, higher values of Stern–Volmer quenching constants were thus obtained for CdSe–ZnO composites with MPA as compared with TGA linker and without linker case, respectively. Nonlinear Stern–Volmer plots as observed for samples without linker case indicated heterogeneous quenching due to insufficient binding between CdSe QDs and ZnO. By means of spectroscopic (PL, UV–VIS, FTIR) and microscopic (TEM, SEM) techniques, we have demonstrated linker-dependent photosensitization mechanism of ZnO layers with CdSe QDs. Our data thus illustrate that interfacial-electron transfer kinetics in QD–linker–ZnO assemblies are almost independent of the length of alkyl-containing molecular linkers.