Titanium nitride (TiN) nanofurnaces are fabricated in a method that involves anodization of a titanium (Ti) foil to form TiO2 nanocavities. After anodization, the TiO2 nanocavities are converted to TiN at 600° C. under ammonia flow. The resulting structure is an array of refractory (high-temperature stable) subwavelength TiN cylindrical cavities that operate as plasmonic nanofurnaces capable of reaching temperatures above 600° C. under moderate concentrated solar irradiation. The nanofurnaces show near-unity solar absorption in the visible and near infrared spectral ranges and a maximum thermoplasmonic solar-to-heat conversion efficiency of 68 percent.