Influence of excitation light wavelength and irradiation time on photothermal properties of photochemically synthesized colloidal gold

The photochemical route is a simple method for producing plasmonic nanoparticles with precise control over size and shape. Some parameters that control the synthesis outcome are the excitation wavelength and irradiation time. By employing the spatial self-phase modulation technique to measure the nonlinear refractive index of thermal origin \(n_{2\text {th}}\) $n_{2\text{th}}$ , we show that the longer the wavelength of the excitation and the irradiation time, the lower the value of \(n_{2\text {th}}\) $n_{2\text{th}}$ .