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With a rising interest in smart windows and optical displays, the utilization of metal oxides (MOs) has garnered significant attention owing to their high active sites, flexibility, and tunable electronic and optical properties. Despite these advantages, achieving precise tuning of optical properties in MOs-based quantum dots and their mass production remains a challenge. In this study, we present an easily scalable approach to generate WO3 quantum dots with diverse sizes through sequential insertion/exfoliation processes in solvents with suitable surface tension. Additionally, we utilized the prepared WO3 quantum dots in the fabrication of luminescent transparent wood via an impregnation process. These quantum dots manifested three distinct emitting colors: red, green, and blue. Through characterizations of the structural and optical properties of the WO3 quantum dots, we verified that quantum dots with sizes around 30 nm, 50 nm, and 70 nm showcase a monoclinic crystal structure with oxygen-related defect sites. Notably, as the size of the WO3 quantum dots decreased, the maximum emitting peak underwent a blue shift, with peaks observed at 407 nm (blue), 493 nm (green), and 676 nm (red) under excitation by a He-Cd laser (310 nm), respectively. Transparent woods infused with various WO3 quantum dots exhibited luminescence in blue/white emitting colors. These results suggest substantial potential in diverse applications, such as building materials and optoelectronics. [ABSTRACT FROM AUTHOR]

It is difficult to obtain ultrathin two-dimensional (2D) tungsten trioxide (WO3) nanosheets through direct exfoliation from bulk WO3 in solution due to the strong bonding between interlayers. Herein, WO3 nanosheets with controllable sizes were synthesized via K+ intercalation and the exfoliation of WO3 powder using sonication and temperature. Because of the intercalation and expansion in the interlayer distance, the intercalated WO3 could be successfully exfoliated to produce a large quantity of individual 2D WO3 nanosheets in N-methyl-2-pyrrolidone under sonication. The exfoliated ultrathin WO3 nanosheets exhibited better electrochromic performance in an electrochromic device than WO3 powder and exfoliated WO3 without intercalation. In particular, the prepared small WO3 nanosheets exhibited excellent electrochromic properties with a large optical modulation of 41.78% at 700 nm and fast switching behavior times of 9.2 s for bleaching and 10.5 s for coloring. Furthermore, after 1000 cycles, the small WO3 nanosheets still maintained 86% of their initial performance. [ABSTRACT FROM AUTHOR]

For practical implementation of water splitting, development of efficient bifunctional catalytic electrodes by replacing precious metal-based electrocatalysts with transition metal-based electrocatalysts with high efficiencies and stabilities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desirable. Accordingly, herein, flower-like Ni/α-Ni(OH)2 particles and nanosheet-shaped Ni/α&β-Ni(OH)2 arrays with adjustable shapes are first fabricated on a carbonized wood (CW) electrode without binders and additives via a simple electrodeposition approach. The hierarchically porous CW electrode with high active surface area provides effective triple pathways for the transport of electrons and ions and release of gas bubbles. Thus, the as-prepared Ni/Ni(OH)2/CW electrodes demonstrate low overpotentials of HER (62 mV; Ni/α&β-Ni(OH)2/CW), which is comparable to that of Pt/C catalyst, and OER (367 mV; Ni/α-Ni(OH)2/CW) in alkaline electrolytes, and the bifunctional electrocatalyst exhibits efficient performance with a cell voltage of 1.74 V at 10 mA cm−2. Furthermore, the cost-effective, eco-friendly, and easily manufactured Ni/Ni(OH)2/CW electrodes can be successfully applied to commercial batteries and solar panels, revealing the feasibilities and practicalities of bifunctional Ni/Ni(OH)2/CW electrodes as active and scalable electrodes for green energy systems of water splitting. [ABSTRACT FROM AUTHOR]