Cesium polytungstates with blue-tint-tunable near-infrared absorption

Abstract

Revisiting Wöhler's method (1824), Cs-doped tungsten bronzes were synthesized by reducing Cs-polytungstate at high temperature, and were pulverized into nanoparticles for determining their optical properties.

X-ray Photoelectron Spectroscopic Study of Reduced Alkali Tungsten Oxides with Localized and Delocalized Electrons

“…12 The corresponding NIR absorption of pulverized nanoparticles increased gradually with reduction. 12 The XPS profiles of W−4f for the CPT samples are reproduced in Figure 2a, with deconvoluted components of W 7/2 5+ , W 7/2 6+ , W 5/2 5+ , and W 5/2 6+ . In the present study, W 4+ was not observed, and neither was it reported in previous studies of HTBs.…”

“…Besides evaporating out most of the hydrogenic components, this hightemperature reduction gradually transformed Cs 4 W 11 O 35 to Cs 0.32 WO 3−y according to X-ray diffraction (XRD). 12 In this paper, we shall call the intermediate state of the two-phase mixture "Cs polytungstate" (CPT). In addition to reducing the Cs 4 W 11 O 35 crystal at high temperature (the "A" process), we obtained Cs-HTB via direct crystallization and reduction of the raw materials at intermediate temperatures (the "B" process).…”

“…30 Thus, an annihilation of those planar W defects, as well as a removal of octahedral oxygens, should proceed with high-temperature reduction, contributing to increasing NIR absorption with increasing numbers of free and localized electrons. 12 Octahedral V O s in Cs-HTB are calculated to be thermodynamically stable when aligned on the basal as well as the prismatic planes, 13 though this has not yet been proved experimentally. Here, with a series of samples with increasing V O s, the XPS W−4f could be examined in expectation of volumetric as well as distributional information about V O and W 5+ .…”

“…23 In the literature of studies containing XPS data for tungsten oxides, O−1s peaks have been variously deconvoluted, as illustrated by several examples 11,23−29 shown in Figure 1. 9 Recent studies 10,12 have indicated that the product HTB contains abundant V O s for Cs 0.32 WO 3−y (assayed 10 as Cs 0.32 WO 2.54 on full reduction). Both Cs 4 W 11 O 35 and Cs 0.32 WO 3−y can be considered on the orthorhombic basis, with the former having W-deficient planes regularly on (020) O ∥(011̅ 0) H (subscripts "O" and "H" stand for orthorhombic and hexagonal, respectively).…”

Dual-functional NIR/UV-shielding poly(lactic acid) nanocomposite films through CWO@PDA core–shell nanoparticles

“…The films based on CWO nanoparticles whose optical properties are absorptive can shield more than 80% of NIR light while maintaining high visible light transmittance. 34 The pure PDLA film exhibits high transmittance (Z75%) in the Vis-NIR region (400-2500 nm). Compared with PDLA, the prepared composite film has higher transmittance in visible light, but stronger shielding performance in NIR (800-2000 nm).…”