Aggregation-Induced Emission Properties of Glutathione and L-Cysteine Capped CdS Quantum Dots and their Application as Z
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ORIGINAL ARTICLE
Aggregation-Induced Emission Properties of Glutathione and L-Cysteine Capped CdS Quantum Dots and their Application as Zn(II) Probe Caixia Yao 1 & Tianyang Lin 1 & Zongjuan Lian 1 & Shenghua Liao 1 & Zhengyu Yan 1 & Shengmei Wu 1 Received: 7 May 2020 / Accepted: 28 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Targeting to obtain better water solubility and stability and less aggregation-caused quenching effects of quantum dots, two kinds of thiol molecules, glutathione and L-cysteine, were firstly united to offer stabilizing ligands for aqueous synthesized CdS quantum dots, which exhibited sensitive aggregation-induced emission properties. Fluorescent intensity of the CdS quantum dots was enhanced about 5 folds by simple solvent exchange from water to 90 vol% PEG200. Restriction of intramolecular motions in an aggregate state was probably the main cause of the phenomenon. At the same time, fluorescent intensity of CdS quantum dots in the presence of zinc ions was able to be enhanced about 2.2 folds. Based on the researches, a handy metal enhanced fluorescent probe for detecting zinc ions was established. And the detection limit was 0.58 μmol/L. Zinc ions as a bridge among CdS quantum dots to form aggregates limited motions of CdS quantum dots to a certain extent and simultaneously enhanced their fluorescence emission intensities. Meanwhile, activation of surface states of CdS quantum dots also led to emission enhancement. Both of the two factors together contributed to the fluorescence enhancement and ultimately to the sensitivity to zinc ion sample detection. Keywords CdS quantum dots . Aqueous synthesis . Aggregation-induced emission properties . Metal enhanced fluorescent probe
Introduction Aggregation-induced emission (AIE) is a photophysical phenomenon that molecules are not or weakly luminescent when dissolved in a compatible solvent but emit intensely when they were aggregated in a poor solvent or precipitated into a solid state [1]. Although aggregation of luminophores tends to lead to aggregation-caused quenching (ACQ) [2], there are still a number of luminogenic molecules with propeller-shaped structures showing pronounced AIE effects [3, 4]. The luminogens with AIE activities have been referred to as AIEgens, such as hexaphenylsilole (HPS), tetraphenylethene (TPE), 10,10′,11,11′-tetrahydro- 5,5′-bidibenzo[a,d][7]annulenylidene (THBA) and so on. However, these AIEgens suffer from the * Zhengyu Yan [email protected] * Shengmei Wu [email protected] 1
Department of Analytical Chemistry, China Pharmaceutical University, 24 Tongjia Lane, Gulou District, Nanjing 210009, China
disadvantages of complex organic synthetic methods, high cost, environment unfriendly, etc., which have greatly limited their practical applications [5]. Therefore, a number of inorganic AIE effect quantum dots (QDs) which owe advantages such as easy aqueous synthetic technology, high luminescence efficiency and excellent biocompatibility have recently been used in
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