Size Control of Cadmium Sulfide Nanoparticles in Polyvinyl Alcohol and Gelatin by Polyethyleneimine Addition
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Size Control of Cadmium Sulfide Nanoparticles in Polyvinyl Alcohol and Gelatin by Polyethyleneimine Addition Oleksandra E. Rayevska1, Galyna Ya. Grodzyuk1, Oleksandr L. Stroyuk1, Stepan Ya. Kuchmiy1, Victor F. Plyusnin2 1 L. V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 prosp. Nauky, 03028, Kyiv, Ukraine, [email protected] 2 Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, 3 Institutskaya str., 630090, Novosibirsk, Russian Federation,
ABSTRACT A simple method of controlling the size and photoluminescence of CdS nanoparticles stabilized by gelatin and polyvinyl alcohol in water by introducing small amounts of polyethyleneimine at the moment of nanoparticle formation is reported. It was found that by adding 0.01–0.10 w.% polyethyleneimine the size of CdS nanoparticles can be changed in the range of 3.8–6.6 nm. The luminescence efficiency and radiative life time of polyvinyl alcoholstabilized CdS nanoparticles were found to increase four-, fivefold with increasing the polyethyleneimine content at the moment of CdS nanoparticles synthesis. A more complex behavior was observed for gelatin-based media, where the interaction between the polyethyleneimine and gelatin can have a detrimental effect of on the size distribution and luminescence properties of CdS nanoparticles. INTRODUCTION Cadmium chalcogenide nanoparticles (NPs) stabilized in aqueous solutions by watersoluble polymers, for example, gelatin and polyvinyl alcohol (PVA) attract considerable attention as promising materials for the luminescent biodiagnostics, photocatalysis, non-linear optics, light-emitting devices, etc. [1-5]. The main challenges at the synthesis of aqueous CdS colloids are low photoluminescence (PL) efficiency, and the limited means of exerting control over the size and the size distribution of CdS NPs [1-3]. Recently we have reported on the synthesis of ultra-small, ~2 nm (with ~10% size dispersion), colloidal CdS nanoparticles (NPs) stabilized by polyethyleneimine (PEI) in water and ethanol [6]. The CdS-PEI NPs exhibit excellent chemical and photo-chemical stability and PL emitted in a broad band at λ = 400-700 nm with the quantum yields up to 20-30% and a life-time of 60-70 ns [6]. However, though producing CdS NPs with superior PL efficiency and size distribution to those stabilized by gelatin or PVA, this approach does not allow varying the NP size without concomitant deterioration of PL properties [6]. Here we report on a simple method of controlling the average size and PL properties of CdS NPs stabilized by gelatin and PVA in water by introducing small amounts of PEI at the moment of NP formation.
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EXPERIMENTAL DETAILS Polyethyleneimine (50 wt% aqueous solution, molecular weight 50.000 g/mole), CdSO4, Na2S, gelatin, polyvinyl alcohol of reagent grade quality were supplied by Sigma-Aldrich. Aqueous colloidal CdS solutions were prepared by interaction between CdSO4 and Na2S in the presence of gelatin [7, 8], PVA [7, 9] and
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