Efficient Method for the Concentration Determination of Fmoc Groups Incorporated in the Core-Shell Materials by Fmoc-Glycine.

Elżbieta Szczepańska,Amanda Kulpa,Tadeusz Ossowski,Beata Grobelna,Jacek Ryl,Paweł Niedziałkowski

doi:10.3390/molecules25173983

Elżbieta Szczepańska, Amanda Kulpa + Show 4 more

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https://doi.org/10.3390/molecules25173983

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Abstract

In this paper, we described the synthesis procedure of TiO2@SiO2 core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc–glycine (Fmoc–Gly–OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO2@SiO2 core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc–Gly–OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene–piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm3 × mol−1 × cm−1 for λ = 289 nm and both 7800 and 8021 dm3 × mol−1 × cm−1 for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO2@SiO2–(CH2)3–NH2 was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc–Gly–OH used as the model sample.

Highlights

Titanium dioxide (TiO2 ) possesses many advantages, is nontoxic, highly efficient, photocatalytically stable and cost-effective [1,2]
All measurements were compared with the solution of Fmoc–Gly–OH used as the model sample
The obtained product was separated by centrifugation, washed with distilled water until complete removal of Sodium dodecyl sulfate (SDS) and the dried on air

Summary

Introduction

Titanium dioxide (TiO2 ) possesses many advantages, is nontoxic, highly efficient, photocatalytically stable and cost-effective [1,2]. This compound has been extensively used in many fields. Molecules 2020, 25, 3983 dioxide nanoparticles (TiO2 NPs) are utilized in many fields of industry [9]. One of the biggest drawbacks of TiO2 NPs is the tendency to agglomerate. This limitation has been solved by the deposition of TiO2 NPs on surfaces of other materials such as silica (SiO2 ) resulting in the formation of TiO2 @SiO2 core-shell particles. The SiO2 coating of NPs provides the colloidal stability, but the presence of silanol groups on the NPs surface contribute to the possible additional modification by various functional groups such as: alkyl [10], hydroxyl [11], thiol (-SH) [12,13], carboxyl (-COOH) [14], amine (-NH2 ) [15], EDTA derivatives [16] or other nanoparticles and ions [17,18]

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