Localized surface plasmon resonance H2 detection by MoO3 colloidal nanoparticles fabricated by the flame synthesis method

Optical properties of VO2 spherical nanoparticles

The LSPR regulation of TiO2: W nanocrystals and its application in enhanced upconversion luminescence

Development of chemically synthesized spherical plasmonic LaB6 nanoparticles for biomedical applications

Plasmonic doped semiconductor nanocrystals: Properties, fabrication, applications and perspectives

Plasmonic metal oxides are promising photocatalysts for the artificial photosynthesis of green ammonia due to localized surface plasmon resonance (LSPR) enhanced photoconversion and rich surface oxygen vacancies improved chemisorption and activation of dinitrogen molecules. However, these oxygen vacancies are unstable during the photocatalytic process and could be oxidized by photogenerated holes, leading to the vanishing of the LSPR. Here, we fabricated antimony-doped molybdenum trioxide nanosheets with stable plasmonic absorption extending into the near-infrared (NIR) range, even after harsh treatment in oxidative atmospheric conditions at high temperatures. For undoped plasmonic MoO3-x nanosheets, the LSPR originates from the abundant oxygen vacancies that vanish after heat treatment at high temperatures in air, leading to the disappearance of the LSPR absorption. Sb doping does not significantly increase the concentration of oxygen vacancies while donating more free electrons because Sb can keep a lower oxidation state. Heat treatment diminished the oxygen vacancies while not affecting the low oxidation state of Sb. As a result, heat-treated Sb-doped MoO3-x nanosheets still show strong LSPR absorption in the NIR range. Both experimental results and theoretical calculations demonstrated that add-on states close to the Fermi level are formed due to the Sb doping and high concentration of oxygen vacancies. The prepared samples were used for photocatalytic nitrogen reduction and showed an LSPR-dependent photocatalytic performance. The present work has provided an effective strategy to stabilize the LSPR of plasmonic semiconductor photocatalysts.

Localized surface plasmon resonance (LSPR) excitation on single silver nanoring with nanoscale surface roughness

Noble metallic nanoparticles (NPs) can exhibit valuable properties such as localized surface plasmon resonance (LSPR) and large surface to volume ratio, which can find various optoelectronic and catalytic applications. In this work, the improved configuration and uniformity of platinum (Pt) NPs are demonstrated by using a sacrificial indium (In) layer via the enhanced solid state dewetting of In-Pt bilayers on sapphire (0001). In a sharp contrast to the conventional dewetting of intrinsic Pt film, the introduction of In component can significantly enhance the global dewetting process and thus can result in the fabrication of well-defined Pt NPs with the improved uniformity. This can be due to the fact that In possess high diffusivity, low surface energy and low sublimation temperature. Upon annealing, the intermixing of In and Pt atoms can occur at the interface due to the inter-diffusion, which forms In-Pt alloy system. As a result, the overall diffusivity and dewetting degree of system can be significantly improved and this can produce more isolated, uniform and semispherical Pt NPs at much lower temperatures as compared to the pure Pt film dewetting. Conveniently, the In atoms preferentially can be removed from the NP matrix by the sublimation even at relatively low temperatures. These Pt NPs exhibit dynamic LSPR band in the UV-visible wavelength based on the excitation of dipolar, quadrupolar and higher order resonance modes. Specifically, the LSPR wavelength can be tuned between ~480 and 580 nm by the fabrication of small to large size Pt NPs with the distinct configuration and interparticle spacing. Furthermore, at a constant Pt thickness, the size, spacing and density of Pt NPs can be readily tuned by the control of In layer thickness. The introduction of sacrificial In component can enable an additional flexibility for the control of surface morphologies of metallic NPs with the low diffusivity materials.

Noble metal nanoparticles, particularly gold and silver nanoparticles, have garnered significant attention due to their ability to manipulate light at the nanoscale through their localized surface plasmon resonance (LSPR). While their LSPRs below 1100 nm were extensively exploited in a wide range of applications, their potential in the near-infrared (NIR) region, crucial for optical communication and sensing, remains relatively underexplored. One primary reason is likely the limited strategies available to obtain highly stable plasmonic nanoparticles with tailored optical properties in the NIR region. Herein, we synthesized AuAg nanorattles (NRTs) with tailored and narrow plasmonic responses ranging from 1000 to 3000 nm. Additionally, we performed comprehensive characterization, employing advanced electron microscopy and various spectroscopic techniques, coupled with finite difference time domain (FDTD) simulations, to elucidate their optical properties. Notably, we unveiled the main external and internal LSPR modes by combining electron energy-loss spectroscopy (EELS) with surface-enhanced Raman scattering (SERS). Furthermore, we demonstrated through surface-enhanced infrared absorption spectroscopy (SEIRA) that the NRTs can significantly enhance the infrared signals of a model molecule. This study not only reports the synthesis of plasmonic NRTs with tunable LSPRs over the entire NIR range but also demonstrates their potential for NIR sensing and optical communication.

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO3 solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

The extinction maximum of the localized surface plasmon resonance (LSPR) of noble metal nanoparticles is highly dependent upon the refractive index of the nanoparticles' surrounding environment. In this study, the effect that molecular resonances have on the intensity, LSPR peak width, and LSPR shift of the LSPR of Ag nanoparticles is monitored. By systematically tuning the LSPR extinction maxima of Ag nanoparticles versus molecular resonances, new phenomena are revealed. First, the LSPR peak shift induced by a resonant molecule varies with wavelength. In most instances, the trends in this data qualitatively track with the Kramer's-Kronig transformation of the molecular resonance spectrum; however, the magnitude of the response is severely underestimated. This was verified from both experimental data and theoretical calculations. Because this phenomenon is revealed to be electronic transition dependent, it is hypothesized that the coupling between the molecular and plasmon resonances is responsible for this wavelength dependent observation. These results will have implications in molecular enhanced LSPR sensing and in the understanding of surface-enhanced spectroscopy.

Localized surface plasmon resonance (LSPR) of noble metal nanoparticles can focus surrounding light onto the particle surface to boost photochemical reactions and solar energy utilization. However, the rarity and high cost of noble metals limit their applications in plasmonic photocatalysis, forcing researchers to seek low-cost alternatives. Recently, some heavily doped semiconductors with high free carrier density have garnered attention due to their metal-like LSPR properties. However, plasmonic semiconductors have complex surface structures characterized by the presence of a depletion layer, which poses challenges for active site exposure and hot carrier transfer, resulting in low photocatalytic activity. In this review, we introduce the essential characteristics and types, synthesis methods, and characterization techniques of full-spectrum plasmonic semiconductors, elucidate the mechanism of full-spectrum nonmetallic plasmonic photocatalysis, including the local electromagnetic field, hot carrier generation and transfer, the photothermal effect, and the solutions for the surface depletion layer, and summarize the applications of plasmonic semiconductors in photocatalytic environmental remediation, CO2 reduction, H2 generation, and organic transformations. Finally, we provide a perspective on full-spectrum plasmonic photocatalysis, aiming to guide the design and development of plasmonic photocatalysts.

It is an efficient mode to optimize photocatalytic performance of semiconductors by the localized surface plasmon resonance (LSPR) effect through constructing composites with noble metal nanoparticles, nevertheless, the understanding for the essential mechanism, especially the LSPR effect on band gap engineering or free radicals, is not clear. Herein, Ag nanoparticles (Ag NPs) were decorated on popular used semiconductors, graphitic carbon nitride (g-C₃N₄), through a microemulsion route. As expected, Ag/g-C₃N₄ hybrid materials demonstrated outstanding photocatalytic decomposition of organic dyes, including methyl orange, phenol and rhodamine B, in which the photocatalytic efficiency of the composite with the optimal ratio of Ag content was 3.37 times higher than that of pristine sample. The mechanism for the better photocatalytic action was attributed to the localized surface plasmon resonance (LSPR) effect, narrow band gap and low valance band position originated from Ag NPs, which resulted in superior visible-light adsorption and the formation of _OH with strong oxidation. As well, because of the synergy between Ag NPs and g-C₃N₄, faster separation of the photogenerated charges and efficiently utilization of the ·OH and ·O-₂ generated from hole and electron are realized simultaneously. Ultimately, our results offer a extremely understanding of superior photocatalytic property caused by the LSPR effect.

Ammonium dinitramide (ADN) is an environmentally friendly solid rocket propellant. In this work, a spectroscopic sensor based on gold nanoparticles (AuNPs) was developed to directly determine ADN at sub-picomolar level, involving the aggregation of melamine (MEL)-functionalized AuNPs (MEL-AuNPs) with dinitramide anion. As a result of supramolecular salt formation between MEL and dinitramide (i.e. melaminium dinitramide) giving rise to MEL-AuNPs aggregation involving hydrogen-bonded bridges among nanoparticles, the peak pertaining to AuNPs' localized surface plasmon resonance (LSPR) absorption is red-shifted to enable ADN determination. Thus, aggregation of MEL-AuNPs in the presence of ADN causes a color change from red to blue, making ADN detection possible even with the naked eye below picomolar levels. The limit of detection (LOD) and limit of quantification (LOQ) of the developed sensor for ADN were 0.013 ng L−1 (1.04 × 10−13 M) and 0.043 ng L−1, respectively. This is the lowest LOD for an ADN determination sensor ever reported. Nitramine, nitroaromatic, and nitrate ester type explosives, and even the dinitramide-containing guanylurea dinitramide (FOX-12) explosive, did not affect the proposed sensor.

Gold nanoparticles (AuNPs) exhibit size-dependent optical properties governed by localized surface plasmon resonance (LSPR) and strong X-ray absorption, making them attractive for biomedical imaging and radiosensitization. Understanding their response to ionizing radiation is therefore essential. Here, citrate-stabilized AuNPs synthesized by the Turkevich method were exposed to LINAC photon irradiation at doses from 0.1 to 100 Gy and characterized by UV– Vis spectroscopy, AFM, and TEM. UV–Vis measurements showed a non-monotonic dose dependence of LSPR intensity with a maximum at 1 Gy, while no significant peak position shift was observed. AFM and TEM analyses revealed dose- dependent changes in nanoparticle size distribution and morphology. Quantitative statistical evaluation indicated particle growth at intermediate doses followed by redistribution toward smaller characteristic sizes at higher doses. These findings demonstrate that clinically relevant irradiation induces measurable but moderate modifications in AuNP optical and structural properties without pronounced aggregation, contributing to the understanding of radiation– nanoparticle interactions.

We report here a gasoline sensor utilizing localized surface plasmon resonance (LSPR) phenomenon of metal nanoparticles (NPs) with a U-bent optical fiber. The optical response of the noble metal NPs upon interaction with gasoline has been simulated and experimentally demonstrated. The increase in gasoline vapor over a period of time induces a change in the refractive index of the adjacent medium of nanoparticle colloids, adhering to the probe, and thus the variation has been observed accordingly. This change in the refractive index in the close proximity to noble metals NPs produces a measurable variation in the output signal that has been correlated with the increase in the concentration of gasoline. The sensor provides better sensitivity corresponding to AgNPs when compared to AuNPs. However, in terms of stability, AuNPs-based LSPR performs better than the AgNPs-based plasmonic response. The present sensing set-up offers a light weight, robust and easy to implement platform that has potent application in detecting volatile liquids very effectively.