Plasmonic Nanomaterials in Dark Field Sensing Systems

Plasma nanoparticles offer promise in data storage, biosensing, optical imaging, photoelectric integration, etc. This review highlights the local surface plasmon resonance (LSPR) excitation mechanism of plasmonic nanoprobes and its critical significance in the control of dark-field sensing, as well as three main sensing strategies based on plasmonic nanomaterial dielectric environment modification, electromagnetic coupling, and charge transfer. This review then describes the component materials of plasmonic nanoprobes based on gold, silver, and other noble metals, as well as their applications. According to this summary, researchers raised the LSPR performance of composite plasmonic nanomaterials by combining noble metals with other metals or oxides and using them in process analysis and quantitative detection.

Plasmonic Hot-Electron-Painted Au@Pt Nanoparticles as Efficient Electrocatalysts for Detection of H2O2

Plasmon-driven catalysis of metal nanostructures has garnered wide interest. Here, a photogenerated plasmonic hot-electron painting strategy was reported to form Au@Pt composite nanoparticles (Au@Pt NPs) with high catalytic reactivity without using reducing agents. Au nanoparticles, including Au nanospheres (Au NSs), Au nanorods (Au NRs), and Au nanobipyramids (Au NBPs), generated hot electrons under localized surface plasmon resonance (LSPR) excitation, which made the platinum precursor reduced as a consequence that Pt(0) atoms were painted on the surface of Au NPs to form an asymmetric Pt shell outside the plasmonic Au core. Compared with bare Au NPs, Au@Pt NPs exhibited significantly enhanced electrocatalytic activity toward reduction of H₂O₂ due to the bimetallic synergistic effect and great dispersion of Au@Pt NP-modified indium tin oxide (Au@Pt NPs/ITO). It exhibited a linear detection of H₂O₂ in a wide concentration range from 0.5 to 1000 μM with a low detection limit of 0.11 μM (S/N = 3). Therefore, the plasmonic hot-electron-painted Au@Pt NPs represent a novel and simple method for the design of advanced noble asymmetric metal nanomaterials.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

A novel deposition mechanism of Au on Ag nanostructures involving galvanic replacement and reduction reactions

Combining a galvanic replacement reaction with a reduction reaction can provide more possibility in the synthesis of Au-Ag hollow nanostructures. However, the detailed atomic deposition mechanism involving these two reactions is unclear. Herein, we proposed a novel deposition mechanism of the Au atoms on Ag nanostructures involving simultaneous galvanic replacement and reduction reactions. The Au atoms originating from galvanic replacement reaction will deposit at surface energy-related facets of the Ag nanostructures while the others originated from reduction reaction at high curvature sites, with the morphology of the final Ag@Au nanostructures determined by the ratio between the two reactions. This mechanism has been verified by experiments on Ag nanorods using varied volumes of Au precursor. Moreover, it can also be extended to Ag cuboctahedrons, suggesting the generality of this mechanism.

Catalytic Nanoframes and Beyond

The ever-increasing need for the production and expenditure of sustainable energy is a result of the astonishing rate of consumption of fossil fuels and the accompanying environmental problems. Emphasis is being directed to the generation of sustainable energy by the fuel cell and water splitting technologies. Accordingly, the development of highly efficient electrocatalysts has attracted significant interest, as the fuel cell and water splitting technologies are critically dependent on their performance. Among numerous catalyst designs under investigation, nanoframe catalysts have an intrinsically large surface area per volume and a tunable composition, which impacts the number of catalytically active sites and their intrinsic catalytic activity, respectively. Nevertheless, the structural integrity of the nanoframe during electrochemical operation is an ongoing concern. Some significant advances in the field of nanoframe catalysts have been recently accomplished, specifically geared to resolving the catalytic stability concerns and significantly boosting the intrinsic catalytic activity of the active sites. Herein, general synthetic concepts of nanoframe structures and their structure-dependent catalytic performance are summarized, along with recent notable advances in this field. A discussion on the remaining challenges and future directions, addressing the limitations of nanoframe catalysts, are also provided.

Manipulating Bimetallic Nanostructures With Tunable Localized Surface Plasmon Resonance and Their Applications for Sensing

Metal nanocrystals with well-controlled shape and unique localized surface plasmon resonance (LSPR) properties have attracted tremendous attention in both fundamental studies and applications. Compared with monometallic counterparts, bimetallic nanocrystals endow scientists with more opportunities to precisely tailor their LSPR and thus achieve excellent performances for various purposes. The aim of this mini review is to present the recent process in manipulating bimetallic nanostructures with tunable LSPR and their applications for sensing. We first highlight several significant strategies in controlling the elemental ratio and spatial arrangement of bimetallic nanocrystals, followed by discussing on the relationship between their composition/morphology and LSPR properties. We then focus on the plasmonic sensors based on the LSPR peak shift, which can be well-controlled by seed-mediated growth and selective etching. This review provides insights of understanding the “rules” involving in the formation of bimetallic nanocrystals with different structures and desired LSPR properties, and also forecasts the development directions of plasmonic sensors in the future.

Seeded growth of gold–silver ultrathin wire–dot hybrid nanostructures

Gold–silver hybrid nanostructures in the form of “ultrathin wire–dots” are prepared in high purity via seeded growth.