Optical excitation of noble metal nanoparticles (e.g., Ag, Au) results in a coherent collective oscillation of the conduction-band electrons known as the localized surface plasmon (LSP). After light excitation, the decay of the excited LSP eventually results in a hot electron distribution within tens of femtoseconds. The hot electrons are often utilized in the context of the catalysis, as they can scatter to occupy the empty orbitals of the adsorbed molecules (i.e., reactants). Next, the hot electrons are scattered by the phonons and their energy is transferred to the metal lattice, which increases the particle temperature (i.e., thermoplasmonic effect). The photothermal effect is finally observed as the thermal energy dissipation to the surrounding medium (i.e., ligand or solution). The thermoplasmonic effect of the black gold in absence of any electron acceptors is here used as an indication for the strong harvesting of light and generation of hot electrons. Herein, the photothermal conversion effect of the black gold solution was examined while the particles were irradiated with NIR lasers (808 and 976 nm). Figure shows the setup adopted to measure the photoheating effect. Briefly, the nanoparticles dispersion is placed in a quartz cuvette and directly irradiated with different lasers. Meanwhile, the temperature of the solutions is simultaneously recorded every 20 seconds by a digital thermometer. Figure shows the stepwise temperature increments of the particle suspensions under continuous light irradiation (808 nm). As shown, the temperature of the gold solution rises quickly with increasing the light exposure time and reaches the steady state after 10 minutes.