Plexcitonic Nanohybrids Based on Gold Nanourchins: The Role of the Capping Layer

Abstract

Plexcitonic nanohybrids are plasmonic–excitonic novel materials whose peculiar properties are attracting considerable attention in photonics, solar cells, and sensing. These materials can be synthesized and characterized easily by assembling organic or inorganic dyes on plasmonic nanoparticles as support. However, the main factors controlling the assembly process and the occurrence of the plexcitonic coupling are still unclear. To fill this gap, in this work, we studied the plexciton coupling of 12 different dyes with a series of gold nanourchins with various coatings and sizes. Among 24 combinations tested, we observed the formation of plexcitonic hybrids only in five cases. Most of them had cyanine J-aggregates as excitonic counterparts. Stronger plexcitonic couplings were obtained when nanourchins were coated with an exchangeable citrate capping layer rather than a strong ionic thiols capping layer. We propose that the presence of a strongly bound capping layer, as in this latter case, reduces the effective volume available to the dyes.

Engineering the Aggregation of Dyes on Ligand-Shell Protected Gold Nanoparticles to Promote Plexcitons Formation

“…These features are promising for important applications in artificial light-harvesting, sensors, and photonics [ 25 , 26 , 28 , 36 , 38 ]. Plexciton materials, where the plasmonic component is a colloidal nanoparticle, are rising increasing interest because they are tunable, scalable, and easy to synthesize by cheap wet chemistry methodologies [ 39 , 40 ].…”

Ultrafast Dynamics of Multiple Plexcitons in Colloidal Nanomaterials: The Mediating Action of Plasmon Resonances and Dark States

“…Among polaritonic media, the class of colloidal plexcitonic materials is particularly appealing nowadays because these materials are cheap and easy to characterize, and their synthesis is easy to scale up. 8 , 21 , 22 …”

“…Plexcitons are a specific example of polaritonic states arising from the coupling of the plasmon resonance of a metal nanostructure such as a nanoparticle or a nanostructured metal surface and a molecular excitation. , Despite having higher dissipation rates than optical microcavities, metallic nanostructures allow tight confinement of the electromagnetic field of light in sub-wavelength regions, featuring extremely confined mode volumes and enabling the establishment of effective interactions with other photonic elements in close proximity. Among polaritonic media, the class of colloidal plexcitonic materials is particularly appealing nowadays because these materials are cheap and easy to characterize, and their synthesis is easy to scale up. ,, …”

“…Among polaritonic media, the class of colloidal plexcitonic materials is particularly appealing nowadays because these materials are cheap and easy to characterize, and their synthesis is easy to scale up. 8,21,22 In a previous publication, we characterized the photophysical properties of colloidal multiplexcitonic materials prepared by assembling gold spherical nanoparticles (NPs) and a tetra-sulfonate-phenyl-porphyrin (TPPS) in different aggregation states. 9 The peculiarity of these systems is that two different sets of resonances can be achieved either in the porphyrin's B-band region, exploiting the strong coupling of the NPs' plasmon with the B-band of J-aggregates, or in the Qband region, forming plasmonic nanogaps with the monomeric species in the intermediate coupling regime.…”

Subtle Structural Change in the Exciton-Forming Dye Drives Plasmon–Exciton Interaction Involving Gold Nanorods into the Strong Coupling Regime: Implications for Enhanced Optical Processes

“…As mentioned earlier, the difference between the two dyes used in this study is the presence of an extra ethyl substituent (Figure 1) on the polymethine chain of Cy78 dye. The presence of an extra substituent on the polymethine chain gives rise to equilibrium between cis-and trans-isomers 25 in Jaggregates of Cy78, while Cy75 J-aggregates remain in transform, as confirmed by fluorescence and AFM studies. The presence of cis J-aggregates in Cy78 gives a higher dipole moment for J-aggregates compared to the trans-form in Cy75.…”