2 research outputs found
Stark Effect Control of the Scattering Properties of Plasmonic Nanogaps Containing an Organic Semiconductor
The development of actively tunable plas-monic nanostructures enables real-time reconfigurable and on demand enhancement of optical signals. This is an essential requirement for a wide range of applications such as sensing and nanophotonic devices, for which electrically driven tunability is required. By modifying the transition energies of a material via the application of an electric field, the Stark effect offers a reliable and practical approach to achieve such tunability. In this work, we report on the use of the Stark effect to control the scattering response of a plasmonic nanogap formed between a silver nanoparticle and an extended silver film separated by a thin layer of the organic semiconductor PQT-12. The plasmonic response of such nano-scattering sources follows the quadratic stark shift. Additionally, our approach allows to experimentally determine the polarizability of the semiconductor material embedded in the nanogap region, offering a new approach to probe the excitonic properties of extremely thin semi-conducting materials such as 2D materials under applied external electric field with nanoscale resolution
Thermoplasmonic Effects in Gain-Assisted Nanoparticle Solutions
We
report a detailed characterization of the photoinduced heating
observed in gain-assisted solutions of gold nanoparticles (AuNPs).
AuNPs, with sizes ranging from 14 to 48 nm and concentration of 2.5
× 10<sup>–10</sup> M, are exposed to different intensity
values of a resonant continuous laser (532 nm), used to excite their
localized surface plasmon resonance (LSPR), responsible for the photogeneration
process. In this way the optimal conditions to achieve the maximum
temperature variation with the least laser dosage are obtained. By
addition of an organic dye to the solutions, whose emission band overlaps
to the LSPR, we found that the contribution to the photothermal efficiency
is enhanced if the solutions are excited at 405 nm. This happens in
the case of smaller NPs, due to a strong coupling effect between the
two subunits, which causes an increase of the extinction cross section
of the whole gain-assisted system. On the other hand, for the larger
AuNPs, an opposite behavior is found: a loss compensation mechanism,
based on a resonant energy transfer process from gain units to plasmonic
nanoparticles, limits the increase of the absorption cross section
with a consequent lowering of the photothermal efficiency. The presented
quantitative analysis of a dispersion of AuNPs results as fundamental
for biomedical applications as well as for integrated plasmonic devices
based on loss compensation effects, where the impact of undesirable
thermal effects cannot be ignored