Synthesis and luminescent properties of ultrasmall colloidal CdS nanoparticles stabilized by Cd(II) complexes with ammonia and mercaptoacetate
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The synthesis of stable water-soluble ultrasmall 1.8 nm CdS nanoparticles co-stabilized with Cd(II) complexes with NH3 and mercaptoacetate ions is reported. The CdS nanoparticles emit broad-band photoluminescence with a peak at 2.3 eV and a quantum yield of up to 15 %. The photoluminescence decay is strongly non-exponential and characterized by an average radiative life-time increasing from 46 to 105 ns as the emission quantum energy decreases from 2.9 to 1.8 eV. The photoluminescence intensity and life-time decrease to about 50 % as the colloid temperature is elevated from 22 to 50 °C. This behavior is completely reversible and assumed to originate from the thermally activated dissociation of Cd(II)–NH3 complexes on the nanoparticle surface and the formation of Cd(II)–H2O complexes acting as the radiationless recombination sites. The strong temperature dependence of the luminescent properties coupled with the small size and reasonably high quantum yields of emission makes CdS nanoparticles co-stabilized with NH3 and mercaptoacetate attractive for bio-imaging, bio-sensing, and other applications.
KeywordsCadmium sulfide Radiative life-time Temperature dependence Thioglycolate Luminescence quenching Water-based colloids Bioimaging
Authors thank Diana Voigt and Prof. Robert Magerle for their kind help in obtaining AFM images, and Dr. Steffen Schulze for performing HRTEM measurements. Authors acknowledge financial support of International Research Training Group “Materials and Concepts for Advanced Interconnects”, Cluster of Excellence “MERGE” (EXC 1075), Alexander von Humboldt Foundation, State Fund for Fundamental Research of Ukraine (Project # F53.3/019), and National Academy of Sciences of Ukraine (Joint Projects of NASU and Siberian Branch of RAS #07-03-12 Ukr and #49-02-14(U)).
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