How to build gold nano-antenna

The evolution and advancement of nanotechnology have created opportunities for the development of advanced materials and devices for applications in the molecular and nanoelectronics. In particular, the chiral single-walled gold nanotubes with helical geometry have demonstrated outstanding potential for creating the strong magnetic and electromagnetic fields which are necessary, in particular, for wireless signal transmission between different elements of nanodevices. Figure shows that such nanotubes geometrically resemble the coils used as macroscopic electromagnets in conventional electrical engineering. The gold nanotubes have the metal-type electron structure and remarkable ballistic conductivity. Consequently, the direct and alternating currents have exhibited formation of the constant magnetic field and generation of the electromagnetic radiation, respectively, the fields’ strengths being dependent on arrangement of atoms in a tubule, its length, and diameter.

To date, the macroscopic alternating-current carrying solenoids have been extensively researched and used for various applications. However, the properties and possible applications of emitting nano-antennas remain underexplored. Recently, Professor Pavel D’yachkov from Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences investigated quantitively the applicability of chiral gold nanotubes with screw axes in developing nano-electromagnets and high-performance radiating nano-solenoid antennas. In particular, the author estimated the electromagnetic fields of solenoid nano-antennas depending on the applied alternating voltage, current, and the atomic structure of tubules. The research work is currently published in the research journal, Chemical Physics Letters.

In this approach, the geometries of the nanotubes were obtained by rolling up gold monoatomic sheets tiled with hexagons centered by the gold atoms. The helical currents flowing around the nanotube’s solenoid were estimated with account of materials band structure. Next by considering the gold nanotubes geometry, their band structure, and ballistic perfect electron transport model, the Maxwell’s equations were used to calculate the longitudinal and azimuthal electric and magnetic fields generated under the alternating voltage and current.

The author reported the realization of record high fields in the nano-volumes using gold nanotubes nano-antennas. The radial dependencies of both the magnetic and electric field components were compared for variety of the gold tubules. The longitudinal magnetic fields were greater than the azimuthal fields, while the reverse was true for the case of electric fields. Consequently, the eigenfrequencies of the field components were observed to lie in the x-ray range. Generally, the magnetic or electromagnetic properties of the system were reported to depend strongly on the geometry of the gold nanotubes and applied electrical constant or alternating voltage.

Furthermore, it was noted that for multi-walled gold nanotubes taken as perfect conductors, the realization of the current and fields was independent of the outer cylindrical gold layers. Similarly, the field internal to the innermost solenoid wall, for a sequence of concentric solenoids, was determined by the boundary condition of the solenoid wall’s inner surface.

In summary, the study reported that chiral gold nanotubes are nano-solenoids with high helicoidal electric currents. Results showed that the electromagnetic fields generated under the alternating voltage and current could be realized in the nano-volumes using gold nanotube nano-antennas. In a statement to Advances in Engineering, Professor D’yachkov said his findings will expand the future research on the potential applications of nano-antennas.