Investigation of the effect of surface modification with organosilane on the multi-redox electrochemical behavior of Co3[Co(CN)6]2 nanocubes

Abstract

The search for new functional nanomaterials rounds science for decades and supramolecular chemistry is an approach used to properly achieve this goal. The present work reports the successful synthesis of Co3[Co(CN)6]2@SiO2-NH2 nanomaterial, formed from the supramolecular association of cobalt Prussian blue analogue, Co3[Co(CN)6]2, and an external amorphous layer (@SiO2-NH2) originated from the addition of organosilanes as tetraethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APTMS). The amount of tetraethyl orthosilicate (TEOS) (0.22, 0.33, 0.44, 0.55, and 0.67 nmol) used to prepare SiO2 layer was varied to assess its impact on the properties of the new synthesized nanomaterial, which were named Co3[Co(CN)6]2@SiO2-NH2-01 to Co3[Co(CN)6]2@SiO2-NH2-05. XRD analyses were consistent with the pattern for Co3[Co(CN)6]2. FTIR measurements confirmed the modification of Co3[Co(CN)6]2 nanocubes surface by the formation of SiO2, and the attachment of NH2 groups after the APTMS addition was confirmed by the ninhydrin test, since the UV–Vis analysis showed a band around 576 nm, typical of a Ruherman’s purple. TEM images showed Co3[Co(CN)6]2 nanocubes with averaging size around 110 nm, and an amorphous SiO2 layer around 15 nm thick after modification by TEOS and APTMS. Cyclic voltammetry analyses of Co3[Co(CN)6]2@SiO2-NH2 nanomaterials showed the appearance of second redox process in lower scan rates (10–50 mV s−1), as the surface of Co3[Co(CN)6]2 is modified by TEOS and APTMS. Beyond that, electron transfer processes were evident even with the dielectric coating of SiO2 at high scan rates, which makes it suitable for application as an electrochemical biosensor as NH2-modified-SiO2 is capable of being functionalized with a wide range of molecules.

Keywords

• Cobalt
• Prussian blue analogue
• Silica
• Multi-redox
• Surface modification