Formation and stability of manganese-doped ZnS quantum dot monolayers determined by QCM-D and streaming potential measurements

Magdalena Oćwieja; Katarzyna Matras-Postołek; Julia Maciejewska-Prończuk; Maria Morga; Zbigniew Adamczyk; Svitlana Sovinska; Adam Żaba; Marta Gajewska; Tomasz Król; Klaudia Cupiał; Michael Bredol

doi:10.1016/j.jcis.2017.04.059

Formation and stability of manganese-doped ZnS quantum dot monolayers determined by QCM-D and streaming potential measurements

J Colloid Interface Sci. 2017 Oct 1:503:186-197. doi: 10.1016/j.jcis.2017.04.059. Epub 2017 May 10.

Affiliations

¹ Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow, Poland.
² Cracow University of Technology, Faculty of Chemical Engineering and Technology, Warszawska 24, 31-155 Krakow, Poland. Electronic address: matras@chemia.pk.edu.pl.
³ Cracow University of Technology, Faculty of Chemical Engineering and Technology, Warszawska 24, 31-155 Krakow, Poland.
⁴ AGH University of Science and Technology, Academic Centre for Materials and Nanotechnology, Mickiewicza 30, 30-059 Krakow, Poland.
⁵ Muenster University of Applied Sciences, Department of Chemical Engineering, Stegerwaldstr. 39, 48-565 Steinfurt, Germany.

PMID: 28525826
DOI: 10.1016/j.jcis.2017.04.059

Abstract

Manganese-doped ZnS quantum dots (QDs) stabilized by cysteamine hydrochloride were successfully synthesized. Their thorough physicochemical characteristics were acquired using UV-Vis absorption and photoluminescence spectroscopy, X-ray diffraction, dynamic light scattering (DLS), transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy. The average particle size, derived from HR-TEM, was 3.1nm, which agrees with the hydrodynamic diameter acquired by DLS, that was equal to 3-4nm, depending on ionic strength. The quantum dots also exhibited a large positive zeta potential varying between 75 and 36mV for ionic strength of 10^-4 and 10^-2M, respectively (at pH 6.2) and an intense luminescent emission at 590nm. The quantum yield was equal to 31% and the optical band gap energy was equal to 4.26eV. The kinetics of QD monolayer formation on silica substrates (silica sensors and oxidized silicon wafers) under convection-controlled transport was quantitatively evaluated by the quartz crystal microbalance (QCM) and the streaming potential measurements. A high stability of the monolayer for ionic strength 10^-4 and 10^-2M was confirmed in these measurements. The experimental data were adequately reflected by the extended random sequential adsorption model (eRSA). Additionally, thorough electrokinetic characteristics of the QD monolayers and their stability for various ionic strengths and pH were acquired by streaming potential measurements carried out under in situ conditions. These results were quantitatively interpreted in terms of the three-dimensional (3D) electrokinetic model that furnished bulk zeta potential of particles for high ionic strengths that is impractical by other experimental techniques. It is concluded that these results can be used for designing of biosensors of controlled monolayer structure capable to bind various ligands via covalent as well as electrostatic interactions.

Keywords: Monolayers of quantum dots; Quantum dots; Quartz crystal microbalance; Streaming potential measurements.