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

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.

Protection of Thiol Groups on the Surface of Magnetic Adsorbents and Their Application for Wastewater Treatment

“…Moreover, it is known that thiol groups are easily oxidized to form disulfide bonds 25 , 26 that are no longer capable of ion-exchange interactions, which decrease their sorption capacity towards many metal ions 27 . Recently it has been demonstrated that introduction of an additional alkyl function into the ligand layer is capable to limit the unwanted interactions and stabilize single functional groups 28 . Therefore it appeared plausible that expanding the range of application for such particles could be achieved by creating mono- as well as bifunctional layers, containing thiol, methyl and/or propyl groups on their surface.…”

Diverse Pathway to Obtain Antibacterial and Antifungal Agents Based on Silica Particles Functionalized by Amino and Phenyl Groups with Cu(II) Ion Complexes

“…The divergence in elemental analysis and titration of NH 2 –/SiO 2 may result from the inaccessibility of the groups or their washing off in the acidic medium. As previously reported, , the presence of additional trifunctional silane with an organic group during the sol–gel transformations of TEOS and APTES affects the speed of co-condensation. There are simultaneous reactions of hydrolysis, condensation, and dissolution proceeding in the alkaline medium created by amino groups .…”

“…The one-pot approaches described in ref , were used to synthesize two types of samples: amino–/silica (NH 2 –/SiO 2 ) and amino–/phenyl–/silica (NH 2 –/C 6 H 5 –/SiO 2 ). Briefly, TEOS (0.018 mol) and APTES (0.006 mol) [or APTES (0.003 mol) with PhTES (0.003 mol)] were mixed with ethanol (100 mL).…”

Synthesis of Cyclen‐Functionalized Ethenylene‐Based Periodic Mesoporous Organosilica Nanoparticles and Metal‐Ion Adsorption Studies

“…It seems that chelation within a Cyclen ring is also contributing to the mechanism of uptake. This indicates a considerable difference for the uptake in mesoporous nanoparticles compared to that of dense nanoparticles, where coordination of metal cations most often can be related to complexation in the monolayer on the surface [14] . The mapping of Ni(II) on E‐P1’ 75/25 PMO NPs and its quantification (Table S5 and Table S7) was performed with EDS (Figures S17–S18) after adsorption of an aqueous solution of Ni(II) at 0.5 and 10 mM initial metal concentration, respectively.…”

“…This indicates a considerable difference for the uptake in mesoporous nanoparticles compared to that of dense nanoparticles, where coordination of metal cations most often can be related to complexation in the monolayer on the surface. [14] The mapping of Ni(II) on E-P1' 75/25 PMO NPs and its quantification (Table S5 and Table S7) was performed with EDS (Figures S17-S18) after adsorption of an aqueous solution of Ni(II) at 0.5 and 10 mM initial metal concentration, respectively. We observed a homogeneous distribution of Ni(II) in the nanorods with an adsorption of 0.46 mmol • g À 1 and 0.94 mmol • g À 1 of Ni(II), respectively.…”