Stable aqueous colloids of ZnS quantum dots prepared using double hydrophilic block copolymersElectronic supplementary information (ESI) available. See DOI: 10.1039/c2nj40738h

• Main Authors: Tarasov, Konstantin, Houssein, Dania, Destarac, Mathias, Marcotte, Nathalie, Gérardin, Corine, Tichit, Didier
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c2nj40738h

Stable aqueous colloids of ZnS nanoparticles have been synthesised using zinc acetate, sodium sulfide and asymmetric double hydrophilic block copolymers PAA- b -PAM (polyacrylic acid- block -polyacrylamide) with various block molecular weights: M PAA = 1000, 3000, 5000 g mol −1 and M PAM = 10 000, 15 000, 30 000 g mol −1 , respectively. The synthesis involves the formation of precursor hybrid polyion complex (HPIC) micelles, in which the micelle core is composed of Zn 2+ ions complexed by polyacrylate blocks, while the corona is constituted by the stabilising neutral PAM blocks. The addition of S 2− ions in the micelle solutions yields ZnS nanoparticles with a diameter of 3-4 nm. The ZnS nanoparticle size is weakly dependent on the copolymer block length, while the particle size distribution correlates with the copolymer asymmetry degree in such a way that a higher M PAM / M PAA ratio yields particles with a narrower size distribution. Characterisation by XRD and SEAD revealed that ZnS has a cubic sphalerite structure with the cell parameter a = 5.25 ± 0.05 Å that is smaller than that of the bulk material ( a = 5.406 ± 0.05 Å). The obtained colloids present photoluminescent properties with an emission band peaking at 410 nm and exhibit a blue-shift of the band-gap energy in the UV-visible absorption spectra due to the quantum-confinement effect. Stable colloids of hydrophilic polymer-protected ZnS nanoparticles are directly obtained from hybrid polyion complex micelles following a simple synthesis route in aqueous suspension.