3D Visible‐Light‐Driven Plasmonic Oxide Frameworks Deviated from Liquid Metal Nanodroplets

Abstract

Eutectic gallium‐indium (EGaIn) liquid metal droplets have been considered as a suitable platform for producing customized 3D composites with functional nanomaterials owing to their soft and highly reductive surface. Herein, the synthesis of a 3D plasmonic oxide framework (POF) is reported by incorporating the ultra‐thin angstrom‐scale‐porous hexagonal molybdenum oxide (h‐MoO3) onto the spherical EGaIn nanodroplets through ultrasonication. Simultaneously, a large number of oxygen vacancies form in h‐MoO3, boosting its free charge carrier concentration and therefore generating a broad surface plasmon resonance across the whole visible light spectrum. The plasmonic chemical sensing properties of the POF is investigated by the surface‐enhanced Raman scattering detection of rhodamine 6G (R6G) at 532 nm, in which the minimum detectable concentration is 10−8 m and the enhancement factor reached up to 6.14 × 106. The extended optical absorption of the POF also allowed the efficient degradation of the R6G dye under the excitation of ultraviolet‐filtered simulated solar light. Furthermore, the POF exhibits remarkable photocurrent responses towards the entire visible light region with the maximum response of ≈1588 A W−1 at 455 nm. This work demonstrates the great potential of the liquid metal‐based POFs for high‐performance sensing, catalytic, and optoelectronic devices.

Insights into the Interfacial Contact and Charge Transport of Gas-Sensing Liquid Metal Marbles

“…Apart from this intrinsic absorbance, a long upward slope in the near-infrared (NIR) region was also observed for the WO 3 /EGaIn liquid metal marble samples, while such a feature was not seen in the WO 3 nanoparticle sample. This is ascribed to the LSPR of the substoichiometric WO 3– x embedded on the surface of EGaIn droplets, as the reducing EGaIn can convert WO 3 into a substoichiometric form . In addition, the ϕ = 30% WO 3 /EGaIn sample shows the strongest LSPR effect in both the visible and NIR regions due to its dense surface WO 3 coverage.…”

Recent advances in the fabrication of 2D metal oxides

“…Examples include the generation of enhanced surface plasmon resonance across the entire visible light and part of the near-infrared region in 2D MoO x enabled by ions and/or oxygen vacancies. Among them, the localized manipulation of d-electron states is the major factor for transition MOXs to achieve abundant high free electron concentration and mobility to generate plasmon resonances in the visible and near-infrared regions ( Alsaif et al., 2021 ). In addition, similar plasmonic properties have appeared in 2D amorphous MoO 3 quantum dots and are expected to be used for Raman spectroscopy detection ( Alsaif et al., 2016 ; Ge et al., 2021 ; Guo et al., 2019 ; Li et al., 2018 ; Liu and Xu, 2018 ; Ren et al., 2019 ; Yin et al., 2021 ; Shangguan et al., 2021 ).…”

Emerging Role of Liquid Metals in Sensing

“…(B) Schematic of POF particles showing (i) the oxygen vacancy formed in hexagonal MoO 3 coated on EGaIn nanodroplets and (ii) methodology utilized for SERS detection of R6G. Reproduced with permission from ref . Copyright 2021 John Wiley and Sons.…”

“…The particles were utilized for detection of malachite green, and a detection limit of 10 −10 was obtained. Alsaif et al 152 developed a 3D plasmonic oxide framework (POF), shown in Figure 8B, consisting of EGaIn droplets coated with ultrathin hexagonal molybdenum oxide. Interest-ingly, EGaIn reduced the MoO 3 flakes into substoichiometric ratios of Mo/O, forming oxygen vacancies in the hexagonal structure.…”