Synthesis of W18O49 Nanorod via Ammonium Tungsten Oxide and Its Interesting Optical Properties

W18O49 nanorods were synthesized by pyrolyzing (NH4)(x)WO3+x/2 nanorods precursors, which were prepared by a hydrothermal reaction using sulfate as a structure-directing agent, in a reductive atmosphere of H-2(5 vol %)/N-2 at 500 degrees 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 W18O49 coating on a quartz glass. Meanwhile, the W18O49 nanorods also showed strong absorption of NIR light and instantaneous conversion of photoenergy to heat. In a word, W18O49 nanorods hold interesting optical properties and are a promising material in a wide range of applications.