Abstract Cobalt-doped zinc selenide/zinc sulfide quantum dots have been successfully synthesized directly in aqueous solution by using L-cysteine as the modifier. The optical properties and structures of the as-prepared quantum dots have been characterized through transmission electron microscopy, X-ray powder diffraction, infrared spectrum, energy dispersive X-ray spectrum, ultraviolet-visible spectrum, and fluorescence spectrum. The results show that cobalt-doped zinc selenide/zinc sulfide quantum dots are spherical particles with a diameter around 2.8 nm, have good dispersity and have a cubic zinc blende structure. The effects of several synthesis conditions on the fluorescence properties of the as-prepared quantum dots are surveyed and the optimum synthesis conditions are found to be as follows: reaction solution pH of 10.0; molar ratio of L-cysteine to hydrogen selenide ions to zinc ions of 1.6:0.15:1; doping content of cobalt ions of 2%; molar ratio of shell (zinc sulfide) to core (cobalt-doped zinc selenide) of 1.5:1. The fluorescence quantum yield of the as-prepared quantum dots increases from 6.4% to 19% via doping with cobalt ions and the epitaxial growth of zinc sulfide shell. The L-cysteine modified on the surface of cobalt-doped zinc selenide/zinc sulfide quantum dots renders the quantum dots water-soluble and bioconjugation capable. The L-cysteine-modified cobalt-doped zinc selenide/zinc sulfide quantum dots will have potential applications in biological fluorescence analysis.

中文翻译：

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L-半胱氨酸修饰的钴掺杂硒化锌/硫化锌量子点的水合成增强荧光

摘要 以L-半胱氨酸为改性剂，在水溶液中直接合成了钴掺杂硒化锌/硫化锌量子点。通过透射电子显微镜、X 射线粉末衍射、红外光谱、能量色散 X 射线光谱、紫外-可见光谱和荧光光谱对所制备的量子点的光学性质和结构进行了表征。结果表明，钴掺杂硒化锌/硫化锌量子点为球形颗粒，直径约2.8 nm，分散性好，呈立方闪锌矿结构。考察了几种合成条件对制备的量子点荧光性质的影响，发现最佳合成条件为：反应溶液pH 10.0；L-半胱氨酸与硒化氢离子与锌离子的摩尔比为1.6:0.15:1；钴离子掺杂量2%；壳（硫化锌）与核（钴掺杂硒化锌）的摩尔比为 1.5:1。通过掺杂钴离子和硫化锌壳的外延生长，所制备的量子点的荧光量子产率从 6.4% 增加到 19%。在钴掺杂硒化锌/硫化锌量子点表面修饰的 L-半胱氨酸使量子点具有水溶性和生物共轭能力。L-半胱氨酸修饰的钴掺杂硒化锌/硫化锌量子点将在生物荧光分析中具有潜在的应用价值。通过掺杂钴离子和硫化锌壳的外延生长，所制备的量子点的荧光量子产率从 6.4% 增加到 19%。在钴掺杂硒化锌/硫化锌量子点表面修饰的 L-半胱氨酸使量子点具有水溶性和生物共轭能力。L-半胱氨酸修饰的钴掺杂硒化锌/硫化锌量子点将在生物荧光分析中具有潜在的应用价值。通过掺杂钴离子和硫化锌壳的外延生长，所制备的量子点的荧光量子产率从 6.4% 增加到 19%。在钴掺杂硒化锌/硫化锌量子点表面修饰的 L-半胱氨酸使量子点具有水溶性和生物共轭能力。L-半胱氨酸修饰的钴掺杂硒化锌/硫化锌量子点将在生物荧光分析中具有潜在的应用价值。