Novel photoswitchable dielectric properties on nanomaterials of electronic core–shell γ-FeO_x@Au@fullerosomes for GHz frequency applications

Abstract

We unexpectedly observed a large amplification of the dielectric properties associated with the photoswitching effect and the new unusual phenomenon of delayed photoinduced capacitor-like (i.e. electric polarization) behavior at the interface on samples of three-layered core-shell (γ-FeOx@AuNP)@[C60(>DPAF-C9)](n)2 nanoparticles (NPs) in frequencies of 0.5-4.0 GHz. The detected relative dielectric constant amplification was initiated upon switching off the light followed by relaxation to give an excellent recyclability. These NPs having e(-)-polarizable fullerosomic structures located at the outer layer were fabricated from highly magnetic core-shell γ-FeOx@AuNPs. Surface-stabilized 2 in a core-shell structure was found to be capable of photoinducing the surface plasmonic resonance (SPR) effect by white LED light. The accumulated SPR energy was subsequently transferred to the partially bilayered C60(>DPAF-C9) fullerosomic membrane layer in a near-field (∼1.5 nm) region without producing radiation heat. Since the monostatic SAR signal is dielectric property-dependent, we used these measurements to provide evidence of derived reflectivity changes on a surface coated with 2 at 0.5-4.0 GHz upon illumination of LED white light. We found that a high, >99%, efficiency of response amplification in image amplitude can be achieved.

3D-Conformer of Tris[60]fullerenylated cis-Tris(diphenylamino-fluorene) as Photoswitchable Charge-Polarizer on GHz-Responsive Trilayered Core-Shell Dielectric Nanoparticles

“…The self-assemble action was induced by strong hydrophobic-hydrophobic (C 60 >)-(C 60 >) interaction forces among fullerene cages. The resulting layered, polarized charges distribution affords a close resemblance to the characteristics of dielectrics, also as nano-capacitor-like assemblies, upon LED irradiation [ 14 , 15 , 16 ].…”

“…Synthetic procedures for the preparation of core-shell γ -FeO x @AuNP nanoparticles ( 4 -NPs) in an average particle diameter of ~20 nm were reported by us recently [ 14 , 15 ]. A slightly modified method was applied in this study to afford similar results based on the verification by transmission electron microscopy (TEM) micrographs and microanalyses of energy dispersive x-ray spectra (EDS).…”

“…Nanoparticles of γ -FeO x and the corresponding plasmonic metallic gold-coated γ -FeO x @AuNP nanoparticles ( 4 -NPs) were synthesized according to a slightly modified procedure reported previously [ 14 , 15 ]. A large scale preparation was carried out for the subsequent fabrication procedure using the same batch of materials to give consistency of γ -FeO x @AuNP characteristics in terms of the particle size and the Au-layer thickness.…”

“…These dielectric materials and polymers may exhibit potential in applications of capacitor-type charge and energy storage [ 10 , 11 , 12 ] and organic photovoltaics [ 13 ]. Recently, we found [ 14 , 15 , 16 ] that the dielectric constant of a medium can be amplified to more than 200–350% by a photoswitching technique using the construction of multi-layered core-shell nanoparticles. They consist of two main photoresponsive components, such as organic electron (e − )-polarizable nanostructure of C 60 (>DPAF-C 9 ) ( 1 -C 9 , Figure 1 ) and inorganic plasmonic gold nanocrystal hybrids in a form of core and shell layered nanomaterials.…”

“…The phenomena resulted in the formation of a positively charged (DPAF) + · -C 9 and a negatively charged (C 60 >) − · cage moieties, respectively. These two charge states form the foundation of our observed photoswitchable dielectric property enhancements [ 14 , 15 , 16 ]. Recently, we further extended the study to design and synthesize highly restricted 3D-stereoisomers based on inter-connected three DPAF-C 9 chromophore units giving a structure of tris(DPAF-C 9 ) or 2 -C 9 ( Figure 1 ).…”