Metal chalcogenide quantum dots (MCQDs) have received tremendous attention in biomedical field for their fascinating optical properties and the admirable biomolecular modifiability. However, challenged by low stability and notorious biocompatibility, MCQDs make them limited for direct biomedical use. Herein, a novel designed and synthesized poly(allylamine) and cysteine co-capped silver indium sulfide quantum dots (PAA-Cys-AIS QDs) with excellent photostability is reported for the specific rapid detection of Cd2+ and Zn2+ ions. The obtained water-soluble PAA-Cys-AIS QDs emitted a stable orange fluorescence at 625 nm with an average size of 3.639 ± 1.006 nm. The unusual anti-photobleaching property of PAA-Cys-AIS QDs is demonstrated to be owing to the introducing of poly(allylamine) and cysteine, which uniquely increased the crystallinity and hydrodynamic size of the structure system. Unexpectedly, unlike most reported approaches for Cd2+ and Zn2+ detection based on the quenching fluorescence mechanism, the PAA-Cys-AIS QDs showed remarkable and rapid fluorescence enhancement after being exposed to Cd2+ and Zn2+ ions aqueous solutions. Notably, the detection limits of the new probe for Cd2+ and Zn2+ are 175 and 50 nM respectively. Complexation and metal ions doping mechanisms are proposed to be responsible for the enhancement of photoluminescence intensity based on the metal ions capture capacity coming from PAA-Cys-AIS QDs’ intrinsic defects and abundant surface amino functional groups. Moreover, the intracellular photostability and biocompatibility of PAA-Cys-AIS QDs are strong enough to prompt us to investigate the metal ions imaging applications in SH-SY5Y cells to further demonstrate the potential for real-live biomedical applications.

中文翻译：

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聚（烯丙胺）和半胱氨酸共封端的硫化银铟量子点，具有优异的光稳定性，适用于基于荧光增强的特异性 Cd2+ 和 Zn2+ 检测


金属硫属化物量子点 （MCQD） 因其迷人的光学特性和令人钦佩的生物分子可修饰性而在生物医学领域受到极大关注。然而，由于稳定性低和臭名昭著的生物相容性，MCQD 使其仅限于直接生物医学使用。在此，报道了一种新颖设计合成的聚（烯丙胺）和半胱氨酸共封端硫化银硫化银量子点 （PAA-Cys-AIS QDs），具有优异的光稳定性，用于特异性快速检测 Cd2+ 和 Zn2+ 离子。获得的水溶性 PAA-Cys-AIS QDs 在 625 nm 处发出稳定的橙色荧光，平均尺寸为 3.639 ± 1.006 nm。PAA-Cys-AIS QD 不寻常的抗光漂白性能被证明是由于聚（烯丙胺）和半胱氨酸的引入，这独特地增加了结构系统的结晶度和流体动力学尺寸。出乎意料的是，与大多数已报道的基于猝灭荧光机制的 Cd2+ 和 Zn2+ 检测方法不同，PAA-Cys-AIS QDs 在暴露于 Cd2+ 和 Zn2+ 离子水溶液后表现出显着和快速的荧光增强。值得注意的是，新探针对 Cd2 + 和 Zn 2 + 的检测限分别为 175 和 50 nM。基于 PAA-Cys-AIS QD 的内禀缺陷和丰富的表面氨基官能团的金属离子捕获能力，提出了络合和金属离子掺杂机制来提高光致发光强度。此外，PAA-Cys-AIS QD 的细胞内光稳定性和生物相容性足够强，足以促使我们研究 SH-SY5Y 细胞中的金属离子成像应用，以进一步证明真实生物医学应用的潜力。