Synthesis of W₁₈O₄₉ nanorod via ammonium tungsten oxide and its interesting optical properties

W₁₈O₄₉ nanorods were synthesized by pyrolyzing (NH₄)_xWO_3+x/2 nanorods precursors, which were prepared by a hydrothermal reaction using sulfate as a structure-directing agent, in a reductive atmosphere of H₂(5 vol %)/N₂ at 500 °C for 1 h. W₁₈O₄₉ nanorods showed high transmittance in the visible region as well as excellent shielding properties of NIR lights. A simulated experiment revealed that excellent heat insulating performance can be realized by applying a 70% visible light transparent W₁₈O ₄₉ coating on a quartz glass. Meanwhile, the W₁₈O ₄₉ nanorods also showed strong absorption of NIR light and instantaneous conversion of photoenergy to heat. In a word, W₁₈O ₄₉ nanorods hold interesting optical properties and are a promising material in a wide range of applications.