Tailoring bifunctional hybrid organic-inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions.

Veronika V Tomina,Vadim G Kessler,Aivaras Kareiva,Inna V Melnyk,Gulaim A Seisenbaeva,Yuriy L Zub,Miroslava Vaclavikova

doi:10.3762/bjnano.8.36

Abstract

Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stöber method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature.

Highlights

Materials with bi- or multifunctional surface layers have been of considerable interest in the recent years [1,2,3,4,5,6,7,8,9,10,11]
The samples, bearing only the aminopropyl groups were denoted as N, those bearing both aminopropyl and methyl groups as NM and those, bearing the fluorinated along with aminopropyl groups as NF
Silica particles with bifunctional surface layers and high content of available aminopropyl groups were successfully produced by a modified one-step Stöber approach

Summary

Introduction

Materials with bi- or multifunctional surface layers have been of considerable interest in the recent years [1,2,3,4,5,6,7,8,9,10,11]. The most suitable objects for such application are apparently hybrid organic–inorganic materials bearing surface-anchored functional groups. The methodology for their synthesis has reached a high-level, opening for broad practical application [14]. The suggested technique was based on the Stöber method [29] These silica spheres, because of their excellent properties, such as adjustable size and surface layer composition, along with their chemical stability and biocompatibility, are promising materials for the application in a wide range of areas (chromatography, controlled drug delivery, bioseparation, chemo- and biosensors, biocatalysis). There arose a question about the possibility of synthesis for such particles with bi- and multi-functional surface layers

Results

Discussion

Conclusion