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

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.