Before starting the HyCoRod project, the LPCNO laboratory had already accomplished the growth of a thin Au shell through coating of bare Co NRs with a multi-metallic Sn/Pt/Au shell layer system. Co@SnPtAu nanorods were successfully implemented in the detection of sHER2 at concentrations of 440 pM. However, it was necessary to improve the optical signal intensity in order to increase the sensitivity of the method.
During HyCoRod project we have developed a strategy in order to improve the homogeneity of the Au shell over the whole nanorod. We have replaced Pt by nickel (Ni), which also reduces the interfacial energy between Au and Co and possess a good miscibility with both materials. Although a homogenous Au shell has been successfully grown over the whole surface of Co@SnNi NR, its thickness (< 0.5 nm) is not sufficient to exhibit LSPR modes. Consequently, up to now, it has not been possible to assess the magneto-plasmonic properties of Co@SnNiAu NRs. Nevertheless, these are promising results as starting point for next projects in order to end up with a thicker Au shell as Au is now distributed along all NR surface, thus presumably acting as nucleating sites.
Co@SnNiAu NRs were then used to biofunctionalize them under a secondment at W. J. Parak’s group at CICbiomaGUNE (Spain). Co@SnNiAu NRs were biofunctionalized with carefully selected antibodies in order to decrease the detection limit when using these NRs as biosensors and improve the sensing results performed so far on the previous Co@SnPtAu NRs analogues. Namely, the current antibodies used are more selective to the protein sHER2 (associated to cancer breast) in the presence of other proteins present within the cell media.
The biofunctionalized Co@SnNiAu NRs were tested as possible future biosensors under a magneto-optical experimental set-up during a secondmend at AIT (Austria). Although the preliminary results are quite optimistic, further experiments are still being performed by the AIT collaborators to complete the study.
The LPCNO group has demonstrated that the controlled transformation of Fe NPs to FexCy or Fe@FexCy NPs leads to an increase in their heating power in an alternating magnetic field. Furthermore, it was possible to use Fe based NPs (Fe@FeCo and Fe@Ru) to catalyse the FTS by application of an alternating magnetic field. The initial idea proposed within HyCoRod project was to develop hybrid Co@Fe-based NRs. However, during the course of the project Ni metal was found to be even a better candidate than Fe as Ni is also a soft magnetic material (thus having also the possibility to improve SAR properties) and, besides, it exhibits excellent catalytic properties in CO2 hydrogenation.
Co@Ni NRs have been tested both as catalysts and heating agents in the catalytic reaction of CO2 hydrogenation to produce CH4. Importantly, these NRs exhibit similar activity and selectivity performance as their Fe@FexCy and Fe@Ru analogues, but interestingly, in the present case, for Co-Ni NRs the amplitude of the magnetic field necessary to activate catalytic reaction is much lower. Hence, this system is energetically more efficient.
Last but not least, it is worth mentioning that HyCoRod project has contributed to develop parallel projects building up valuable collaborations. Co NRs directly grown onto a porous substrate have been found to be excellent catalysts for FTS in fixed-bed reactor giving rise to significantly activity and selectivity towards C5+ (Angew. Chem. Int. Ed., 57, 10579-10583 (2018)). Moreover, Co-Ni NRs have been used as prototypes to test a home-made set up device to assess SAR properties using high field frequencies.
Finally, all these results derived from HyCoRod project have been disseminated, so far, in three international conferences, of which two oral presentations and one invited talk: MRS-Fall 2017 (Boston), E-MRS 2018 (Strasbourg) and EMN 2018 (Milan).
