Abstract Herein, a highly facile, rapid and one-pot approach has been applied for the synthesis of water soluble starch capped CdSe quantum dots (QDs) by using UV irradiation in the aqueous solution containing cadmium sulphate, sodium selenosulfate, acetone and 2-propanol. No external reducing agents were added to the solution, as the radicals generated in situ upon photoirradiation i.e., 2-hydroxy-2-propyl radicals, (CH3)2C OH could reduce the precursor ions for the synthesis of these QDs. These QDs were characterised by various techniques such as UV–Vis absorption, XRD, Raman, FTIR, TEM and SEM measurements. The presence of strong quantum confinement effects could be realized from their very small size i.e., ∼3 nm as revealed by TEM studies. Besides, these QDs were found to exhibit photoluminescence (PL) in the longer wavelength region. The PL intensity as well as the charge carrier lifetime values could be conveniently tuned by simply varying the Cd to Se precursor ratio during the synthesis. Furthermore, a relatively novel approach has been adopted to extract these QDs from the colloidal solution by freezing it to 0 °C followed by de-freezing to room temperature. The extracted QDs were functionalized with thiourea in order to increase the PL quantum yield and the stability of the QDs. The effects of pH and temperature on the PL intensity of functionalized CdSe QDs were also investigated to explore their applicability in sensing of heavy metal ions. Interestingly, the QDs displayed highly selective PL quenching in the presence of Cu2+, Cr6+ and Hg2+ metal ions. The limits of detection for these metal ions have been determined and a probable PL quenching mechanism is postulated.

中文翻译：

---

淀粉封端的 CdSe 量子点的紫外诱导合成：硫脲功能化及其在检测水溶液中重金属离子中的应用

摘要 本文采用一种非常简便、快速和一锅法的方法，通过在含有硫酸镉、硒代硫酸钠、丙酮和 2-丙醇的水溶液中使用紫外线照射合成水溶性淀粉封端的 CdSe 量子点（QDs）。 . 没有将外部还原剂添加到溶液中，因为光照射时原位产生的自由基，即 2-羟基-2-丙基自由基，(CH3)2C OH 可以还原合成这些 QD 的前体离子。这些量子点通过各种技术进行表征，例如紫外-可见光吸收、XRD、拉曼、FTIR、TEM 和 SEM 测量。TEM 研究表明，它们非常小的尺寸，即~3 nm，可以实现强量子限制效应的存在。此外，发现这些量子点在较长波长区域表现出光致发光（PL）。通过在合成过程中简单地改变 Cd 与 Se 前驱体的比例，可以方便地调整 PL 强度以及电荷载流子寿命值。此外，还采用了一种相对新颖的方法从胶体溶液中提取这些量子点，方法是将其冷冻至 0 °C，然后解冻至室温。提取的量子点用硫脲功能化，以提高 PL 量子产率和量子点的稳定性。还研究了 pH 和温度对功能化 CdSe QD PL 强度的影响，以探索它们在感测重金属离子中的适用性。有趣的是，量子点在 Cu2+、Cr6+ 和 Hg2+ 金属离子存在下表现出高度选择性的 PL 猝灭。已经确定了这些金属离子的检测限，并假设了可能的 PL 猝灭机制。