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Hybrid Co-based nanorods for biosensing and catalysis

Periodic Reporting for period 1 - HyCoRod (Hybrid Co-based nanorods for biosensing and catalysis)

Reporting period: 2016-09-01 to 2018-08-31

The H2020 EU Research and Innovation programme identifies energy efficiency, nanotechnologies and biotechnology as important areas of research. In the case of energy efficiency is of great importance to find new strategies to store the intermittence energy generated by the renewable energies. Concerning the area of biotechnology, cancer is one of the leading causes of death, having an incidence of 2.6 million people in Europe in 2012, and causing an estimated annual cost of €126 billion. Thus, detecting this illness at the very early stages would significantly reduce the mortality. Nanoscience and Nanotechnology is expected to have and important incidence in those mentioned research areas.

HyCoRod project aimed at tailoring the physical and chemical properties of metallic cobalt nanorods (NR) by combining them with two different metals for two important applications: (i) cobalt-gold for in vitro biodiagnostics and magneto-optical properties (MO) and (ii) cobalt-nickel for magnetically induced catalysis. The first main objective of HyCoRod was to improve the detection limit (up to subfemtomolar range) of analyte molecules, using a magneto-optical based detection method. The second objective was to study the MO properties of Co@Au NRs. The third objective was to evaluate the potential of Ni-containing Co NRs in magnetically induced catalytic reactions for fuel production by reusing the surplus of energy from renewable energies and the CO2 coming from contamination sources.

In conclusion, HyCoRod project has achieved to provide the society with a new nanostructured system with the composition of Co@SnNiAu that is envisaged to demonstrate its capability, in the following next experiments, as excellent biomarker sensor. Furthermore, a Co-Ni based nano-object has been already proved as a promising both catalyst and nanoheater for important energy-related catalytic reactions such as CO2 hydrogenation.
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).
HyCoRod project had not only fundamental but also applicative interest. Regarding Co@Au NRs it was expected that if a water-resistant and plasmon optically active Au-shell was achieved, the detection of analyte at subfemtomolar concentration would establish the PlasMag technology as a setup of choice for PoC in vitro biodiagnostics for a great number of biomarkers. Although the appropriate thickness of the Au shell in the Co@SnNiAu NRs has not been possible to achieve within the HyCoRod timeline, the new selected antibodies that were not anticipated at the HyCoRod project, against the protein HER2, are expected to provide detection limits down to picomolar range. The results related to these biosensing experiments are expected to be completed in the following months. Concerning the new concept of magnetically induced catalysis, the new Co-Ni NRs obtained during the HyCoRod project may be a more suitable model catalysts than Co-Fe since Ni is known to be an efficient catalyst in a broader range of catalytic reactions compared to Fe. We have successfully tested Co-Ni NRs in CO2 hydrogenation to produce fuel (CH4) and it is scheduled to use them in other catalytic reactions to demonstrate their versatility for magnetic induced catalysis applications.

Overall, both nanostructures systems (Co@SnNiAu and Co-Ni) obtained through HyCoRod project are expected to have in the near future both a socio-economic and societal impact as premature cancer detection or sustainable energy production directly affect the citizens’ wellbeing. Moreover, the economic burden in the Health and Care system would be reduced.
HyCoRod project: biosensing and catalytic applications for cancer detection and sustainable energy