Cystine-capped CdSe@ZnS nanocomposites: mechanochemical synthesis, properties, and the role of capping agent
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Cystine-capped CdSe@ZnS nanocomposites: mechanochemical synthesis, properties, and the role of capping agent Matej Bala´zˇ • Peter Bala´zˇ • Georgi Tjuliev Anton Zubrı´k • Marı´a Jesu´s Sayague´s • Anna Zorkovska´ • Nina Kostova
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Received: 23 August 2012 / Accepted: 12 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media New York 2012
Abstract Cystine-capped CdSe@ZnS nanocomposites were synthesized mechanochemically with the aim to prepare a material which could be used in medicine for biosensing applications. Although synthesized CdSe@ZnS nanocomposites were capped with L-cysteine, cystine was formed from L-cysteine during the milling process. It was proven that water plays the key role in this oxidative transformation. The novel material was characterized by the complex of physico-chemical methods (FTIR, XPS, SEM, EDX, surface area measurements) and CHNS analysis. The leakage of Cd2? and Zn2? ions into physiological solution was also studied. List of FTIR XPS SEM EDX
abbreviations Fourier-transform infrared spectroscopy X-ray photoelectron microscopy Scanning electron microscopy Energy-dispersive photoelectron spectroscopy
M. Bala´zˇ (&) P. Bala´zˇ A. Zubrı´k A. Zorkovska´ Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, Kosˇice, Slovakia e-mail: [email protected] G. Tjuliev N. Kostova Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 11, Sofia, Bulgaria M. J. Sayague´s Institute of Materials Science of Seville, Consejo Superior de Investigaciones Cientı´ficas, C/Americo Vespucio 49, 41092 Sevilla, Spain
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Introduction Cadmium selenide is perfectly suitable for application in biological imaging, because of its fluorescent properties and quantum confinement. CdSe nanoparticles of appropriate size can have an absorption edge and emission peak anywhere in the visible spectrum. Therefore, they can be used as multicolor fluorescent markers in biological systems [1]. However, CdSe particles contain cadmium, which is toxic and its direct contact with biological systems can be harmful [2]. A protective shell around the CdSe nanoparticles is one of the ways of preventing the toxic effect. ZnS is pretty suitable for playing the role of a shell for CdSe nanoparticles, because of several properties including a wider bandgap than CdSe [3]. The addition of ZnS surface coating results in the increase of the stability of nanocrystals, the decrease of the surface oxidation [4], lower cytotoxicity and the improvement of optical properties of the system [5]. In addition, these CdSe/ZnS nanoparticles can be capped with various organic species [6–8]. The amino acid L-cysteine was also used as a capping agent in the synthesis of pretty similar system [9]. It is possible to use mechanochemical approach to synthesize nanoparticles [10–12]. However, in this case, during milling, the oxidation process takes place and cystine is formed from L-cysteine. L-cystine is a dimer of L-cysteine, precursor of protein and an optically active quadridenta
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