In this study, a magnetically separable threedimensional (3D) Co 3 [Co(CN) 6 ] 2 /Fe 3 O 4 nanocomposite comprising magnetic nanoparticles (NPs) adsorbed on the nanocubes of a cobalt Prussian blue analogue was prepared. The nanocomposite exhibited enhanced electrochemical performance in Co 2+ /Co 3+ conversion, while the superparamagnetic behavior of the magnetite NPs was preserved even after adsorption on the nanocubes. Increased Faradaic currents were observed in the cyclic voltammograms (CV) for Co 3 [Co(CN) 6 ] 2 /Fe 3 O 4 in comparison with the CV of isolated Co 3 [Co(CN) 6 ] 2 . This increase was attributed to supramolecular charge transfer between the cobalt Prussian blue analogue and the magnetic NPs and the larger amount of electroactive species on the electrode. Transmission electron microscopy images showed well-defined Co 3 [Co(CN) 6 ] 2 nanocubes that had edge lengths of 21−140 nm and were decorated with spherical magnetite NPs less than 10 nm in diameter. Interestingly, an intimate contact between the nanocubes and aggregate formation was avoided by Fe 3 O 4 NPs. The composition, morphology, and surface properties of the nanohybrid material were assessed by UV−vis absorption spectroscopy, FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, and Brunauer−Emmett−Teller surface area. The analytical results of nanocomposite showed main bands, crystalline phases, and structures associated with Fe 3 O 4 and Co 3 [Co(CN) 6 ] 2 . The bifunctional properties of Co 3 [Co(CN) 6 ] 2 /Fe 3 O 4 are potentially useful for building novel (bio)sensors and magnetic devices for clinical applications.

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Cobalt was electrodeposited onto chemical vapor deposition (CVD) graphene/Si/SiO 2 substrates, during different time intervals, using an electrolyte solution containing a low concentration of cobalt sulfate. The intention was to investigate the details of the deposition process (and the dissolution process) and the resulting magnetic properties of the Co deposits on graphene. During and after electrodeposition, in-situ magnetic measurements were performed using an (AGFM). These were followed by ex situ morphological analysis of the samples with ∆t DEP 30 and 100 s by atomic force microscopy in the non-contact mode on pristine CVD graphene/SiO 2 /Si. We demonstrate that it is possible to electrodeposit Co onto graphene, and that in-situ magnetic measurements can also help in understanding details of the deposition process itself. The results show that the Co deposits are ferromagnetic with decreasing coercivity (H C ) and demonstrate increasing magnetization on saturation (M SAT ) and electric signal proportional to remanence (M r ), as a function of the amount of the electrodeposited Co. It was also found that, after the end of the dissolution process, a certain amount of cobalt remains on the graphene in oxide form (this was confirmed by X-ray photoelectron spectroscopy), as suggested by the magnetic measurements. This oxide tends to exhibit a limited asymptotic amount when cycling through the deposition/dissolution process for increasing deposition times, possibly indicating that the oxidation process is similar to the graphene surface chemistry.

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