Temperature measurements at the nanoscale are vital for
the application
of plasmonic structures in medical photothermal therapy and materials
science but very challenging to realize in practice. In this work,
we exploit a combination of surface-enhanced Raman spectroscopy together
with the characteristic temperature dependence of the Raman peak maxima
observed in β-phase copper phthalocyanine (β-CuPc) to
measure the surface temperature of plasmonic gold nanoparticles under
laser irradiation. We begin by measuring the temperature-dependent
Raman shifts of the three most prominent modes of β-CuPc films
coated on an array of Au nanodisks over a temperature range of 100–500
K. We then use these calibration curves to determine the temperature
of an array of Au nanodisks irradiated with varying laser powers.
The extracted temperatures agree quantitatively with the ones obtained
via numerical modeling of electromagnetic and thermodynamic properties
of the irradiated array. Thin films of β-CuPc display low extinction
coefficients in the blue-green region of the visible spectrum as well
as exceptional thermal stability, allowing a wide temperature range
of operation of our Raman thermometer, with minimal optical distortion
of the underlying structures. Thanks to the strong thermal response
of the Raman shifts in β-CuPc, our work opens the opportunity
to investigate photothermal effects at the nanoscale in real time.