Retardation of nanoparticles growth by doping
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NANO EXPRESS
Open Access
Retardation of nanoparticles growth by doping Valentyna Nosenko1*, Galyna Rudko1, Volodymyr Fediv2, Andrij Savchuk3, Evgenij Gule1 and Igor Vorona1
Abstract The process of doping of CdS nanoparticles with Mn during colloidal synthesis is analyzed by EPR and optical studies. Analysis of EPR results demonstrated that Mn2+ ions are successfully incorporated into the nanoparticles and occupy the crystal sites both in the bulk of a NP and near the surface of a NP. Optical absorption measurements revealed the retardation of absorption edge shift during the growth for Mn-doped CdS NPs as compared to the undoped CdS NPs. It was concluded that the presence of Mn in the solution leads to the inhibition of NPs growth. Keywords: Doping; Colloidal nanoparticles; CdS; CdS:Mn; Polyvinyl alcohol; Radius size
Background Over the past decades, much interest has been focused on the fabrication of semiconductor nanocrystals and various composites that contain nanoparticles (NPs). It was shown that II–VI semiconductor NPs are promising for applications in biological and medical fields as molecular probes or biomedical labels. On the other hand, their size-dependent optical, electronic, and magnetooptical properties stimulated potential applications in optoelectronic devices [1-3]. As a representative of II–VI NPs, nano-CdS is known for tunable light emission in the visible range that makes it attractive for fabrication of light emitting devices and luminescent markers [4]. Doping of CdS NPs draws considerable attention as one of the ways to achieve new possibilities of controlling optical, magnetic, electrical or other physical properties of these objects. Doping with Mn is of special interest, since, on the one hand, it can add magnetic properties, and, on the other hand, gives possibility to change light emission. Up to now the most well-defined method for growing both undoped and doped NPs is molecular beam epitaxy (MBE). Unfortunately, MBE growth methods are rather expensive, complex, time-consuming and do not produce NPs suitable for incorporation into polymers and biological tissues.
Colloidal route for the NPs synthesis is an attractive alternative to MBE growth due to its cheapness and simplicity. It does not demand building of any costly apparatus; procedure is simple and has been shown to yield high-quality NPs. The method implies the growth of NPs in the solutions containing capping molecules that restrict NPs growth. However, the doping of colloidally produced NPs is still an actual challenge. Moreover, despite of extensive studies the details of NPs formation during the colloidal synthesis are still obscure and need more detailed study [3,5]. In the present study we focused on the doping of CdS NPs with Mn2+ during the colloidal growth. The doping procedure proposed here did not essentially change the route of undoped NPs growth. Among vast variety of the capping agents the polyvinyl alcohol (PVA) has been chosen due to its attractive properties, such as cheapness, flexibility, transparency in
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