Hollow Au nanoparticles-decorated silica as near infrared-activated heat generating nano pigment

The photothermal effect resulting from the local surface plasmon phenomenon of metal nanoparticles is essentially a light–heat conversion mechanism, wherein the heat is generated around the nanoparticles owing to the absorption of light by the nanoparticles. A pigment exhibiting the photothermal effect can be used as a multifunctional nano-pigment providing high heat energy from a small amount of light energy as well as a bright color. In this study, a grayish blue nano-pigment (GBNP) was synthesized using silica nanoparticles and hollow Au nanoparticles that exhibited a relatively high photothermal effect in the near-infra red (NIR) region. By irradiating light in the NIR region, GBNP could selectively produce stable thermal energy with a photothermal efficiency of 39%. It was mixed with paint to confirm its applicability to pigments and heat-generation performance. The surface of paint containing 4 wt% GBNP was increased to 110 °C, exhibiting a stable heat-generation performance under both repeated and continuous NIR irradiation. Furthermore, the thermal energy generated due to the photothermal effect implied the high evaporation efficiency of water droplets on the surface. This pigment might be utilized in applications where a selectively high temperature needs to be maintained continuously for bacterial-growth prevention and moisture control.