Rapid synthesis of broadband Ag@TiO2 core-shell nanoparticles for solar energy conversion

Plasmonics are applied to concentrate light at the nanoscale and are integrated into photothermal technologies to improve solar energy absorption. Here, we report a one-step synthetic route of super broadband Ag@TiO2 core-shell nanoparticles under well-defined conditions using silver nitrate (AgNO3) and titanium butoxide (TBT) in N,N-dimethylformamide as raw materials and hexadecyl trimethyl ammonium chloride (CTAC) as both an inducer and a protective agent. Transmission electron microscopy revealed that the prepared nanoparticles have well-defined core-shell structures. The intermediates and final product were further characterized by UV-vis absorption, which showed that the synthesized Ag@TiO2 core-shell nanoparticles exhibit super broadband absorbance in the visible light range, and the surface plasmon resonance (SPR) peak can be systematically tuned between 414 and 499 nm. In addition, X-ray diffraction and energy-dispersive spectroscopy confirmed the compositions of the nanoparticles. The nanoparticles prepared under well-defined conditions, i.e., a TBT:AgNO3 molar ratio of 3:1, CTAC concentration of 0.6 mM, temperature of 80 °C, and reaction time of 70 min, show an SPR peak at 474 nm, which is close to the maximum solar irradiation intensity and has great potential for promoting solar energy conversion.