Abstract l -cysteine capped ZnS:O quantum dots (QDs) were prepared by two steps. The effects of l -cysteine (L-cys) on the crystal structure, size, water-dispersibility, photoluminescence (PL) and cytotoxicity were studied. It was found that the surface modification of L-cys on ZnS:O QDs did not change the crystal structure, and their average crystallite size increased with the increase of L-cys content. Moreover, the water-dispersibility and photostability of ZnS:O QDs can be improved by L-cys modification. The results displayed that the PL intensity was remarkably enhanced with the increase of L-cys concentration. The most intense emission was obtained when the mass ratio of L-cys:ZnS:O = 1.2:1, and was about 5 times stronger than that of uncoated ZnS:O QDs. First-principles calculations were used to explain the origin of high PL intensity. Also, it showed that the L-cys capped ZnS:O QDs were nontoxic and maintained remarkable cell viability and morphology up to the concentration of QDs was 200 mg/mL for HeLa cells. This work suggested that L-cys capped ZnS:O QDs had favorable biocompatibility and may be used for in vitro cell imaging of HeLa cells.

中文翻译：

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L-半胱氨酸对ZnS:O量子点光致发光、电子和细胞毒性的影响

摘要 l-半胱氨酸封端的 ZnS:O 量子点 (QDs) 通过两个步骤制备。研究了 l-半胱氨酸 (L-cys) 对晶体结构、尺寸、水分散性、光致发光 (PL) 和细胞毒性的影响。发现L-cys在ZnS:O QDs上的表面改性没有改变晶体结构，它们的平均晶粒尺寸随着L-cys含量的增加而增加。此外，ZnS:O QDs 的水分散性和光稳定性可以通过 L-cys 改性得到改善。结果表明，随着L-cys浓度的增加，PL强度显着增强。当 L-cys:ZnS:O = 1.2:1 的质量比时获得最强烈的发射，并且比未涂覆的 ZnS:O QD 强约 5 倍。第一性原理计算用于解释高PL强度的起源。还，结果表明，L-cys 封端的 ZnS:O 量子点是无毒的，并且在 HeLa 细胞的量子点浓度为 200 mg/mL 时仍保持显着的细胞活力和形态。这项工作表明 L-cys 加帽的 ZnS:O QDs 具有良好的生物相容性，可用于 HeLa 细胞的体外细胞成像。