Abstract
The influence of heat generation on the conventional process of LSPR based sensing has not been explored thus far. Therefore, a need exists to draw attention toward the heat generation issue during LSPR sensing as it may affect the refractive index of the analyte, leading to incorrect sensory conclusions. This manuscript addresses the connection between the photo-thermal effect and LSPR. We numerically analyzed the heat performance of a gold cladded nanotip. The numerical results predict a change in the micro-scale temperature in the microenvironment near the nanotip. These numerical results predict a temperature increase of more than 20 K near the apex of the nanotip, which depends on numerous factors including the input optical power and the diameter of the fiber. We analytically show that this change in the temperature influences a change in the refractive index of the microenvironment in the vicinity of the nanotip. In accordance with our numerical and analytical findings, we experimentally show an LSPR shift induced by a change in the input power of the source. We believe that our work will bring the importance of temperature dependence in nanotip based LSPR sensing to the fore.
Highlights
When light interacts with the conduction electrons of a metal at the metal–dielectric interface, it brings about coherent oscillations of these electrons
Modal analysis was done on the tip and it was observed that a number of modes of the visible regime could be accommodated in the apex
We looked at the presence of the photothermal effect at the apex of a plasmonic tip
Summary
When light interacts with the conduction electrons of a metal at the metal–dielectric interface, it brings about coherent oscillations of these electrons. The spectrum of LSPR at the metal–medium interface depends on various parameters such as the morphology of the metallic structure, irradiating electromagnetic field, and the refractive index of the environment [13]. This opens up the possibility of tuning the response of these structures or their use as sensors through their ability to discriminate between refractive indices. Given the inherent conflict among the results from these two different kinds of studies, it can be postulated that the use of LSPR as a sensing mechanism requires extreme care This is because it is prone to error due to the change of the refractive index of the analyte through heat generation from surface plasmons. We comment on the reliability of LSPR from a tapered nanotip as a sensing method under transmission spectroscopy
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