Inorganic–Organic Interfacial Electronic Effects in Ligand-Passivated WO_3–x Nanoplatelets Induce Tunable Plasmonic Properties for Smart Windows

Abstract

Transition-metal oxide (TMO) nanocrystals (NCs), displaying localized surface plasmon resonance (LSPR) properties, are an emerging class of nanomaterials due to their high stability, high earth abundance, and wide range of spectral responses covering the near-to-far infrared region of the solar spectrum. Although surface passivating ligands are ubiquitous to colloidal NC-based research, the role of ligands, specifically the impact of their chemical structure on the dielectric and LSPR properties of TMO NC films, has not been investigated in detail. Here, we report for the first time the chemical effects at the metal–ligand (inorganic–organic) interfaces influencing the optical constants and LSPR properties of thin films comprising highly oxygen-deficient, sub-stoichiometric, LSPR-active tungsten oxide (WO3–x ) nanoplatelets (NPLs). We studied ligands with two different types of binding head groups, aromatic conjugation, and short and long hydrocarbon chains. Using density functional theory calculations, we determine that the changes in the interfacial dipole moments and polarizability control the permittivity at the interface, resulting in the alteration of dielectric and LSPR properties of ligand-passivated NPL in thin nanocrystalline films. The photochromic properties of WO3–x NPL passivated with different ligands in thin films have also been investigated to highlight the impact of interfacial permittivity caused by the chemical structures of passivating ligands. Taken together, this study provides a fundamental understanding of emerging properties at the metal–ligand interface that could be further optimized for energy efficiency in smart windows.

Kinetic Studies of WO3-Based Photochromism in Polyvinyl Alcohol Film

“…The blue coloration occurred due to electrochemical reduction or by band-gap excitation under UV irradiation is referred to as electrochromism or photochromism, respectively. Especially, the electrochromism of WO 3 has been widely studied for smart windows to modulate the near infrared (NIR) solar radiation, which is considered as a promising technology to save energy in buildings. − Transparent indium tin oxide electrodes coated with amorphous WO 3 or hexagonal sodium tungsten bronze nanorods turned blue when cathodic potentials were applied. Transmittance of those electrodes was high at 400–520 nm, and their absorption was extended to the NIR range. , On the other hand, photochromic behaviors of WO 3 have been extensively studied for applications as information storage media, color sensor, nanoinks, and UV monitors. ,− Various forms of WO 3 such as colloidal nanoparticles, powders, small disks prepared by pressing powders, thin films on glasses or fibers and nanosheets have been investigated for various applications.…”

Mechanistic Insights into Anion-Induced Electrochromism of Ru(II)-Based Metallo-Supramolecular Polymer

“…Electrochromic (EC) materials have received significant attention for their various applications in smart windows [ 7 , 8 ], antiglare rear-view mirrors [ 9 ], information displays [ 10 ], etc. Diverse EC materials have been exploited so far, including transition metal oxides [ 11 , 12 , 13 ], transition metal complexes [ 14 , 15 , 16 ], organic small molecules [ 17 , 18 ], organic conducting polymers [ 19 , 20 ] and metallo-supramolecular polymers [ 21 , 22 , 23 ]. In particular, metallo-supramolecular polymers (MSPs) are recently developed electrochromic materials with superior electrochromic performance and stable redox properties [ 5 , 21 ].…”

Near-Infrared Dual-Band LSPR Coupling in Oriented Assembly of Doped Metal Oxide Nanocrystal Platelets

“…Meanwhile, degenerately doped semiconductor nanocrystals have recently emerged as a new material class that hosts LSPR in the infrared range of light. , With the rapidly growing technological demands for infrared optics, − numerous strategies have been proposed for generating and tuning infrared LSPR in semiconductor nanocrystals . Unlike metals, semiconductors offer new degrees of freedom in terms of charge density and dielectric function of the medium, which are the primary parameters determining the LSPR frequency.…”