Sub-stoichiometric tungsten oxide WO3-x is a promising candidate for improving the spectral selectivity of electrochromic (EC) smart windows in terms of optical contrast in the near-infrared (NIR) (responsible for heat fluxes modulation), and that independently from the visible (VIS) (responsible for light modulation). This innovative behaviour relates to intrinsic plasmonic properties of localized surface plasmon resonance (LSPR), conferring two additional configurations of optical filtration, with up to 4 accessible states (clear, cool, warm, dark) instead of the 2 conventional ones (clear, dark). Such plasmonic materials material ultimately lead to universal glazing devices adaptable to all sorts of climates and seasons and increase overall energy efficiency of such windows. This presentation addresses innovative approaches of wet chemical synthesis and surface modification of WO3-x nanostructures as benchmark dual-band VIS-NIR electrochromic compound. Monoclinic WO3-x (m-WO3-x) nanorods are purposely targeted, notably avoiding clusters of impurities made up of hexagonal-WO3 (h-WO3) flakes. The characteristic differences of these two different species obtained as colloidal suspensions are investigated in terms of composition, structure, shape and optical and electronic behaviour. Additionally, we establish the EC performance of functional layers consecutively processed through spin and spray coating3 and containing only m-WO3-x or both h-WO3 and m-WO3-x nanostructures, notably in terms of optical contrast, switching times, cycling stability and coloration efficiency in both VIS an NIR ranges. To this end, the specific tuning of the obtained WO3-x nanostructures using oleic acid and/or phosphonic acid based ligands either in-situ or post-synthesis, is investigated at both levels of colloidal inks and wet-coated films, and evaluated in terms of chemical stability and consecutive EC efficiency.