Abstract:
A photoexcited plasmonic nanoparticle (NP) can decay both radiatively and nonradiatively. The hot charge carriers and heat (thermoplasmonic heat) generated, via
the non-radiative decay pathway, have been used for various chemical and physical
transformations. However, the contribution of these two non-radiative decay process
in bringing out a particular task is often debated. The main reason for this limitation is
the lack of practical techniques available to quantify the thermoplasmonic heat under
the conditions of photocatalysis (basically in solution state). In this thesis, we have
tried to explore the possibility of using a thermally driven organic transformation as a
tool to study the thermoplasmonic heat generated. Here the source of heat was the
thermoplasmonic heat generated by photoexcited plasmonic gold NPs (AuNPs). The
reaction yield was used the proxy to quantify the thermoplasmonic heat generated:
more the yield, more is the thermoplasmonic heat. For this, we have selected the
thermal transformation of 3-hydroxy-2-methyl-4-pyrone with methylamine to form the
product 3-hydroxy-1,2-dimethyl-pyridin-4-one. We successfully demonstrated that the
thermoplasmonic heat from photoexcited AuNPs can drive the organic conversion.
This method is more effective to quantify the thermoplasmonic heat as it gives a
combined estimate of both localised heating and bulk heating in the system. Using
reaction yield as a parameter, we investigated the effect of size of AuNPs on the
generation of thermoplasmonic heat. Accordingly, ~10 nm sized AuNP was found to
be generating the maximum thermoplasmonic heat under our experimental conditions,
which was further independently verified using solar-vapor generation experiments as
well.
