Synthesis and luminescent properties of ultrasmall colloidal CdS nanoparticles stabilized by Cd(II) complexes with ammonia and mercaptoacetate

Abstract

The synthesis of stable water-soluble ultrasmall 1.8 nm CdS nanoparticles co-stabilized with Cd(II) complexes with NH 3 and mercaptoacetate ions is reported. The CdS nanoparticles emit broadband 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)-NH 3 complexes on the nanoparticle surface and the formation of Cd(II)-H 2 O 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 NH 3 and mercaptoacetate attractive for bio-imaging, bio-sensing, and other applications.

Temperature‐Dependent Photoluminescence of Silver‐Indium‐Sulfide Nanocrystals in Aqueous Colloidal Solutions

“…As discussed above, the temperature dependences of the intensity and spectral parameters of aqueous AIS (and AIS/ZnS) NCs stabilized by GSH complexes are very similar to those of aqueous CdS NCs stabilized both by Cd(II)‐PEI complexes and Cd(II)‐NH 3 ‐MA complexes . All three types of NCs indeed show linear Arrhenius‐like dependences of the PL intensity on temperature (SI, Figure S4) with apparent PL quenching activation energies of 2 nm CdS‐PEI and 2 nm CdS‐NH 3 ‐MA NCs estimated to be (310±10) meV and (250±10) meV, respectively (Figure d, blue bars).…”

“…Earlier we reported on the synthesis and PL properties of ultra‐small (the size d <2 nm) CdS NCs stabilized by Cd(II) complexes with PEI or by a combination of MA and ammonia . Both types of CdS NCs revealed very similar reversible variations of the PL intensity when heated up and cooled down in aqueous colloidal solutions (see examples in SI, Figure S3).…”

“…In particular, we reported recently on the aqueous syntheses of ternary AIS and core/shell AIS/ZnS NCs stabilized by NC surface complexes with polyethyleneimine (PEI), thioglycolic (mercaptoacetic) acid, and glutathione (GSH) . Our approaches to aqueous ternary NCs stemmed from our previous works on the syntheses of ultra‐small (the size d <2nm) CdS NCs capped with Cd(II) complexes with polyethyleneimine (PEI) or mixed complexes of Cd(II) with ammonia and mercaptoacetate (MA), as well as ultra‐small core/shell CdSe/CdS NCs . In these studies, we found that luminescent properties of aqueous ultra‐small CdX NCs and ternary AIS (CIS) NCs are very similar, both types of NCs emitting relatively intense visible PL characterized by large spectral widths and Stokes shifts .…”

Fluorescence modulation of cadmium sulfide quantum dots by azobenzene photochromic switches

“…The synthesis of surface-modified CdS QDs, CdS-(I) and CdS-(II) dyad assemblies is described as follows. In order to engineer photochrome-chromophore dyad, the CdS QDs were synthesized by performing slight modifications to the procedure given by Raevskaya et al [14]. For this purpose, ambient conditions were maintained, i.e.…”

Brightly luminescent colloidal Ag–In–S nanoparticles stabilized in aqueous solutions by branched polyethyleneimine

“…Taking into account the complexity of such synthesis alternative methods of formation of luminescent semiconductor metal-chalcogenide NPs directly in water were in the focus of interest for the last several years [5,12]. It was found that the water-soluble cadmium chalcogenide NPs featuring reasonably high PL QY (10-20%) can be produced directly in the presence of a number of polymer stabilizers [12] such as glycodendrimers, block-copolymers [5,12], polyethyleneimine [17] as well as combinations of molecular species, for example, ammonia and mercaptoacetate complexes with Cd(II) [18].…”