Plasmonic Mechanism Research Articles

Plasmon enhanced oxygen evolution reaction on Au decorated Ni(OH)2 nanostructures: The role of alkaline cations solvation

Water electrolysis is widely acknowledged to be kinetically hindered by the oxygen evolution reaction (OER), which involves multiple electron transfer steps. A critical yet often overlooked factor ruling the OER rate is the intricate interplay between alkaline cations of electrolyte, reaction intermediates, and the electrocatalyst surface. This study investigates the impact of plasmonic excitation on the OER using hexagonal hybrid Ni(OH)2-Au nanoplates in different alkaline electrolytes. While CsOH electrolyte exhibited the highest overall OER electroactivity, LiOH presented a remarkable enhancement under plasmonic excitation. Furthermore, FTIR-RAS and calculations analysis revealed that plasmonic relaxation mechanisms accelerate the Li+ environment modification process, mimicking the electrostatic configuration of Cs+, which facilitates a stabilized interaction between the active site (Ni3+) and OER intermediates, promoting rapid O−O bond formation. Our findings suggest that manipulating the cation’s vicinity through plasmonic heating is a promising strategy for enhancing OER efficiency.

A novel non-catalytic plasmonic immunoabsorbant assay amplification mechanism

The amplification of signals is dependent upon enzyme/ catalyst. Enzyme activity, specificity, pH condition, enzyme linkers, stability, storage and efficiency are some very important factors that can eventually affect the detection results. We aimed to amplify signals without the assistance of enzyme/ catalyst so that the strategy can be used in the wide range of signal detection including immune-assay. Silver nanocrystals (Ag NCs) grown from self-nucleation are used as chromogens due to their strong plasmon band at ∼ 400 nm. During 140 s of reaction time in presence of 6.10 mM CTAB and 0.61 mM of AgNO3, the 0.57 mM of Ascorbic acid allows Ag over growth on antibody-tagged gold nanospheres (10±0.5 nm) that competes silver atoms from the self-nucleation growth and thus affects the growth kinetics of the latter. By utilizing the opened kinetic window, sensitive detection has been achieved from 6.67 × 10–14 M (1 pg) to 3.33 × 10–9 M (50 ng) using human IgG as a model protein. The non-catalytic plasmonic immunoabsorbant assay we developed herein adds a new possibility of plasmonic NPs for sensitive detection. The detection slope and resolution is higher and better than those via signal amplification through the assistance of enzymes/ catalysts. This work supports the concept that nanoparticles mediated reactions are sensitive enough that they have the potential to go independently without enzymes/ catalyst assistance.

Plasmonic Photovoltaic Effect of an Original 2D Electron Gas System and Application in Mid‐Infrared Imaging

AbstractOwing to their consistently emerging applications in modern photonics, highly sensitive and rapid mid‐infrared (MIR) photodetectors, operating at high temperatures, are of great significance. Herein, a novel PbTe/Ge heterostructure is introduced. Notably, the discovery of a 2D electron gas (2DEG) system on the surface of the PbTe layer is experimentally identified for the first time. A high‐performance PbTe/Ge heterostructure MIR photodetector utilizing a plasmonic photovoltaic effect is developed by employing asymmetric electrodes. The photodetecting device demonstrates an exceptionally high detectivity of 1.1 × 1011 Jones along with a short response time of 15 ns at room temperature. Additionally, the proposed plasmonic photovoltaic mechanism of the device is investigated and mainly ascribed to the propagating plasmons, generated by the coupling of the 2DEG with incident MIR photons. Moreover, a linear detector array (LDA) of PbTe/Ge is demonstrated for a thermal imaging application, which exhibits promising high‐quality real‐time imaging via the 2D photodetector arrays on Ge‐based integrated circuits. This work opens up a new way for the development of next‐generation, advanced MIR photonic devices and integrated photonic systems.

Improvement of directivity in plasmonic nanoantennas based on structured cubic gold nanoparticles

An array of metallic nanoparticles can diffract or concentrate the incident electromagnetic wave and behave as an antenna. In this paper, the effects of the inner sub-wavelength structure of nanoparticles are studied on the directivity of the plasmonic nanoantenna, which is coated on the output of a waveguide. Three 5*5 element configurations are analyzed: nanocubes, nanoshells, and nanoframes array. Numerical results are obtained using the 3D FDTD technique. The results show that structured nanoantennas can improve the antenna's directivity due to the plasmonic properties and hybridization mechanism. Between the three configurations investigated in the 250–800 nm wavelength range, the nanoshell array exhibits maximum and minimum amounts of its directivity at 321.5 nm and 591 nm, respectively. At 558 nm, nanoframes and nanoshells' arrays show the same amount of directivity, and from the wavelength greater than 558 nm, the nanoframe array has the best performance. The results may help design and fabricate directive optical fiber endcaps.

Stearic acid-coated plasmonic Ag nanoparticles as a dual catalyst for enhanced NiO chemo and photo catalysis

The phenomenon of Localized Surface Plasmon Resonance (LSPR) in plasmonic metal nanoparticles causes a strong absorption of visible light and leads to the generation of hot electrons on the surface and the creation of localized electromagnetic fields near the surface. This characteristic enhances the catalytic performance of a plasmonic metal Ag–NiO nanocomposite (NiO-SNP) when exposed to low-flux visible light irradiation. The NiO-SNP was synthesized using a simple and cost-effective ultrasonication method. Its structural, morphological, and optical properties were analyzed, confirming the formation of nanocomposites. The proximity of stearic acid-coated Ag nanoparticles (SNP) acts as visible light-harvesting antennas, promoting NiO's activity for effectively reducing paracetamol (PM) drugs. The improved catalytic property is attributed to an electron relay effect, while the strong electromagnetic fields generated by irradiated Ag nanoparticles facilitate the concentration of PM molecules at active sites, leading to accelerated reaction rates. NiO-SNP2 demonstrates remarkable PM degradation: 97 % in tap water and 82.6 % in deionized water within 10 min, demonstrating its catalytic effectiveness. The plasmonic SNP mechanism in NiO-SNP1 nanocomposites enhances photocatalytic efficiency by up to 90 %, owing to efficient charge separation and transfer, resulting in a notable 1.5-fold increase in PM degradation. The degradation kinetics follow a pseudo-first-order model, with rate constants (k) ranging from approximately 0.059 to 0.6104 min⁻1, underscoring the crucial role of Ag nanoparticles in enhancing photocatalytic activity and degradation efficiency. Catalysis and visible light photocatalysis are significantly improved with increasing concentrations of NiO and SNP, respectively. This research could inspire a new approach to transforming traditional metal catalysis into plasmonic-metal catalysis.

Circular terahertz ratchets in a two-dimensionally modulated Dirac system

We report on the observation of the circular ratchet effect excited by terahertz laser radiation in a specially designed two-dimensional metamaterial consisting of a graphene monolayer deposited on a few-layer graphene gate patterned with an array of triangular antidots. We show that a periodically driven Dirac fermion system with spatial asymmetry converts the a.c. power into a d.c. current, whose direction reverses when the radiation helicity is switched. The circular ratchet effect is demonstrated for room temperature and a radiation frequency of 2.54 THz. It is shown that the ratchet current magnitude can be controllably tuned by the patterned and uniform back gate voltages. The results are analyzed in the light of the developed microscopic theory considering electronic and plasmonic mechanisms of the ratchet current formation. Published by the American Physical Society 2024

Linear Vibronic Coupling Approach for Surface-Enhanced Raman Scattering: Quantifying the Charge-Transfer Enhancement Mechanism.

The outstanding amplification observed in surface-enhanced Raman scattering (SERS) is due to several enhancement mechanisms, and standing out among them are the plasmonic (PL) and charge-transfer (CT) mechanisms. The theoretical estimation of the enhancement factors of the CT mechanism is challenging because the excited-state coupling between bright plasmons and dark CT states must be properly introduced into the model to obtain reliable intensities. In this work, we aim at simulating electrochemical SERS spectra, considering models of pyridine on silver clusters subjected to an external electric field E⃗ that represents the effect of an electrode potential Vel. The method adopts quantum dynamical propagations of nuclear wavepackets on the coupled PL and CT states described with linear vibronic coupling models parametrized for each E⃗ through a fragment-based maximum-overlap diabatization. By presenting results at different values of E⃗, we show that indeed there is a relation between the population transferred to the CT states and the total scattered intensity. The tuning and detuning processes of the CT states with the bright PLs as a function of the electric field are in good agreement with those observed in experiments. Finally, our estimations for the CT enhancement factors predict values in the order of 105 to 106, meaning that when the CT and PL states are both in resonance with the excitation wavelength, the CT and PL enhancements are comparable, and vibrational bands whose intensity is amplified by different mechanisms can be observed together, in agreement with what was measured by typical experiments on silver electrodes.

Colorimetric Pressure Sensing by Plasmonic Decoupling of Silver Nanoparticles Confined within Polymeric Nanoshells.

Employing a plasmonic decoupling mechanism, we report the design of a colorimetric pressure sensor that can respond to applied pressure with instant color changes. The sensor consists of a thin film of stacked uniform resorcinol-formaldehyde nanoshells with their inner surfaces functionalized with silver nanoparticles. Upon compression, the flexible polymer nanoshells expand laterally, inducing plasmonic decoupling between neighboring silver nanoparticles and a subsequent blue-shift. The initial color of the sensor is determined by the extent of plasmonic coupling, which can be controlled by tuning the interparticle distance through a seeded growth process. The sensing range can be conveniently customized by controlling the polymer shell thickness or incorporating hybrid nanoshells into various polymer matrices. The new colorimetric pressure sensors are easy to fabricate and highly versatile, allow for convenient tuning of the sensing range, and feature significant color shifts, holding great promise for a wide range of practical applications.

UV-light-responsive Ag/TiO2/PVA nanocomposite for photocatalytic degradation of Cr, Ni, Zn, and Cu heavy metal ions

The rapid growth of industrialization has led to the uncontrolled pollution of the environment, and rapid action is needed. This study synthesized Ag/TiO2/polyvinyl alcohol (PVA) nano photocatalyst for promising light-derived photocatalytic removal of heavy metal ions. The design of experiment (DOE) was used to study the effect of important factors (pH, reaction time, and photocatalyst dosage) to maximize the final performance of the photocatalyst. In the optimized condition, the Ag/TiO2/PVA nano-photocatalyst removed more than 94% of Cr6+ in 180 min, and the efficiency was more than 70% for Cu2+, Zn2+, and Ni2+ metal ions. The adsorption of the heavy metal ions on the photocatalyst was described well with the Langmuir isotherm, while the pseudo-second-order linear kinetic model fitted with the experimental data. The nano-photocatalyst's stability was confirmed after maintaining its performance for five successive runs. The enhanced photocatalytic activity for the heavy metal ions removal can be attributed to the presence of metallic silver nanoparticles (electron transfer and plasmonic fields mechanisms) and PVA, which delayed the recombination of electron–hole. The synthesized ternary Ag/TiO2/PVA nano-photocatalyst showed promising performance for the elimination of heavy metal ions and can be used for environmental remediation purposes.

Bound states in the continuum and plasmonics in perovskite nanostructures for emission, detection, and sensing

We present photonic and plasmonic configurations on surfaces of perovskite materials which facilitate robust temporal confinement of light by means of photonic bound states in the continuum (BIC) and/or surface plasmonic resonance. Our three-dimensional finite-difference time domain simulation captures the intricate properties of BIC of photonic lattices and plasmonic cavities. We show that single crystal of MAPbBr3 can be utilized in developing new generation of nanostructured surface emitters, where with sufficient modulation depth high quality factors can be achieved with photonic BIC. We also show how gold thin film enhances the emission of FAPbBr3 NCs by plasmonic mechanisms

Advances in fundamentals and application of plasmon-assisted CO2 photoreduction.

Artificial photosynthesis of hydrocarbons from carbon dioxide (CO2) has the potential to provide renewable fuels at the scale needed to meet global decarbonization targets. However, CO2 is a notoriously inert molecule and converting it to energy dense hydrocarbons is a complex, multistep process, which can proceed through several intermediates. Recently, the ability of plasmonic nanoparticles to steer the reaction down specific pathways and enhance both reaction rate and selectivity has garnered significant attention due to its potential for sustainable energy production and environmental mitigation. The plasmonic excitation of strong and confined optical near-fields, energetic hot carriers and localized heating can be harnessed to control or enhance chemical reaction pathways. However, despite many seminal contributions, the anticipated transformative impact of plasmonics in selective CO2 photocatalysis has yet to materialize in practical applications. This is due to the lack of a complete theoretical framework on the plasmonic action mechanisms, as well as the challenge of finding efficient materials with high scalability potential. In this review, we aim to provide a comprehensive and critical discussion on recent advancements in plasmon-enhanced CO2 photoreduction, highlighting emerging trends and challenges in this field. We delve into the fundamental principles of plasmonics, discussing the seminal works that led to ongoing debates on the reaction mechanism, and we introduce the most recent abinitio advances, which could help disentangle these effects. We then synthesize experimental advances and in situ measurements on plasmon CO2 photoreduction before concluding with our perspective and outlook on the field of plasmon-enhanced photocatalysis.

Plasmonic‐assisted Electrocatalysis for CO2 Reduction Reaction

AbstractIntegrating plasmonic features as an emerging strategy for enhancing electrocatalysis for the carbon dioxide reduction reaction (CO2RR). The key parameters responsible for the enhanced electrocatalysis performance are the local heating, the hot carriers, and near‐field enhancement induced by localized surface plasmon resonance (LSPR, that is, plasmonic) excitation. This review provides a concise overview of the fundamental mechanism of CO2RR, detailing the generation and decay of plasmonic and the energy transfer dynamics between plasmonic nanostructures and adsorbates. It further involves recent progress in plasmonic‐assisted electrocatalysis for CO2RR, including experimental and theoretical research to decipher plasmonic mechanisms. Finally, it ends with an insightful discussion of the existing challenges and potential future directions in this field.

Synthesis of visible-light-driven ZIF-67/Ag-AgVO3 heterostructures with enhanced synergistic photocatalytic degradation mechanism

The utilization of solar energy through semiconductor-based photocatalysis has gained significant attention. This approach enables the breakdown of different pollutants efficiently. Nonetheless, the effectiveness of photocatalytic reactions is limited by the rapid recombination of electron-hole pairs and the inefficient utilization of light. Consequently, extensive endeavors have been dedicated to resolving these issues by developing well-engineered photocatalytic heterojunctions to enhance photocatalytic activity by separating the photogenerated charge carriers. Herein, heterojunction composites of Co-zeolitic imidazolate framework (ZIF-67) grafted onto Ag-AgVO3 nanoribbons (ZIF-67/Ag-AgVO3) have been constructed using hydrothermal/solvothermal routes. The phase purity, morphological, and optical characteristics of the ZIF-67/Ag-AgVO3 photocatalysts were described by XRD, XPS, FESEM, EDS, TEM, DRS PL and BET surface area procedures. The ZIF-67/Ag-AgVO3 photocatalysts exhibited enhanced photocatalytic degradation performance for Congo red dye (CR). During the visible-light photocatalysis, the degradation rate of CR can achieve 94.4 % in 120 min, outperforming that of ZIF-67, AgVO3, Ag-AgVO3, and ZIF-67/AgVO3 samples. Also, the excellent photostability of the ZIF-67/Ag-AgVO3 has been achieved, which is verified by recycling experiments. A plasmonic Z-type mechanism was considered to be behind the boosted photodegradation behavior of the synthesized ZIF-67/Ag-AgVO3 photocatalyst.

Plasmon-Molecule Interactions in Single-Molecule Junctions.

Single-molecule optoelectronics offers opportunities for advancing integrated photonics and electronics, which also serves as a tool to elucidate the underlying mechanism of light-matter interaction. Plasmonics, which plays pivotal role in the interaction of photons and matter, have became an emerging area. A comprehensive understanding of the plasmonic excitation and modulation mechanisms within single-molecule junctions (SMJs) lays the foundation for optoelectronic devices. Consequently, this review primarily concentrates on illuminating the fundamental principles of plasmonics within SMJs, delving into their research methods and modulation factors of plasmon-exciton. Moreover, we underscore the interaction phenomena within SMJs, including the enhancement of molecular fluorescence by plasmonics, Fano resonance and Rabi splitting caused by the interaction of plasmon-exciton. Finally, by emphasizing the potential applications of plasmonics within SMJs, such as their roles in optical tweezers, single-photon sources, super-resolution imaging, and chemical reactions, we elucidate the future prospects and current challenges in this domain.

Nanoscale and ultrafast in situ techniques to probe plasmon photocatalysis

Plasmonic photocatalysis uses the light-induced resonant oscillation of free electrons in a metal nanoparticle to concentrate optical energy for driving chemical reactions. By altering the joint electronic structure of the catalyst and reactants, plasmonic catalysis enables reaction pathways with improved selectivity, activity, and catalyst stability. However, designing an optimal catalyst still requires a fundamental understanding of the underlying plasmonic mechanisms at the spatial scales of single particles, at the temporal scales of electron transfer, and in conditions analogous to those under which real reactions will operate. Thus, in this review, we provide an overview of several of the available and developing nanoscale and ultrafast experimental approaches, emphasizing those that can be performed in situ. Specifically, we discuss high spatial resolution optical, tip-based, and electron microscopy techniques; high temporal resolution optical and x-ray techniques; and emerging ultrafast optical, x-ray, tip-based, and electron microscopy techniques that simultaneously achieve high spatial and temporal resolution. Ab initio and classical continuum theoretical models play an essential role in guiding and interpreting experimental exploration, and thus, these are also reviewed and several notable theoretical insights are discussed.

Ultrasmall and tunable TeraHertz surface plasmon cavities at the ultimate plasmonic limit

The ability to confine THz photons inside deep-subwavelength cavities promises a transformative impact for THz light engineering with metamaterials and for realizing ultrastrong light-matter coupling at the single emitter level. To that end, the most successful approach taken so far has relied on cavity architectures based on metals, for their ability to constrain the spread of electromagnetic fields and tailor geometrically their resonant behavior. Here, we experimentally demonstrate a comparatively high level of confinement by exploiting a plasmonic mechanism based on localized THz surface plasmon modes in bulk semiconductors. We achieve plasmonic confinement at around 1 THz into record breaking small footprint THz cavities exhibiting mode volumes as low as {V}_{cav}/{lambda }_{0}^{3} sim 1{0}^{-7}-1{0}^{-8}, excellent coupling efficiencies and a large frequency tunability with temperature. Notably, we find that plasmonic-based THz cavities can operate until the emergence of electromagnetic nonlocality and Landau damping, which together constitute a fundamental limit to plasmonic confinement. This work discloses nonlocal plasmonic phenomena at unprecedentedly low frequencies and large spatial scales and opens the door to novel types of ultrastrong light-matter interaction experiments thanks to the plasmonic tunability.

Models of light absorption enhancement in perovskite solar cells by plasmonic nanoparticles

AbstractNumerous experiments have demonstrated improvements on the efficiency of perovskite solar cells by introducing plasmonic nanoparticles, however, the underlying mechanisms are still not clear: the particles may enhance light absorption and scattering, as well as charge separation and transfer, or the perovskite's crystalline quality. Eventually, it can still be debated whether unambiguous plasmonic increase of light absorption has indeed been achieved. Here, various optical models are employed to provide a physical understanding of the relevant parameters in plasmonic perovskite cells and the conditions under which light absorption may be enhanced by plasmonic mechanisms. By applying the recent generalized Mie theory to gold nanospheres in perovskite, it is shown that their plasmon resonance is conveniently located in the 650–800 nm wavelength range, where absorption enhancement is most needed. It is evaluated for which active layer thickness and nanoparticle concentration a significant enhancement can be expected. Finally, the experimental literature on plasmonic perovskite solar cells is analyzed in light of this theoretical description. It is estimated that only a tiny portion of these reports can be associated with light absorption and point out the importance of reporting the perovskite thickness and nanoparticle concentration in order to assess the presence of plasmonic effects.

Enhancing the absorption figure of merit on solution-based CuO thin films by Ni doping

We evaluated an absorbance effectiveness on the solar spectrum using an absorption figure of merit (a-FOM) for the conducting thin films. In particular, Ni-doped and un-doped CuO thin films were deposited by a facile and sustainable solution-processed synthesis, whose Ni doping concentration was varied to be 0.2, 0.6, 1, 2, 3, 4 wt%. We observed a change of smooth surface to an appearance of nanoparticles by Ni doping, which supported to form of a plasmonic mechanism for improving the light capture and retention. The absorption of long wavelengths was improved and extended to the near-infrared range. That is, the bandgap energy decreased from 2.10 to 1.88 eV with Ni doping. Also, we found that the absorption length decreased from 99.93 nm to 63.80 nm as the Ni doping increased. In addition, the CuO-based film with 4 wt% Ni doping showed a maximal value of a-FOM as high as 30.88 Ω−1cm−1, corresponding to a resistance of 2.07 MΩ/sq and an absorption length of 63.80 nm. Our finding suggested that Ni-doped CuO thin films can be considered as an excellent selection of absorbent conductive oxide layers for application in optoelectronic devices and solar cell systems.

Encoding Mie, plasmonic, and diffractive structural colors in the same pixel.

We present a 1D reflective multi-level structural color design that incorporates Mie, plasmonic, and diffractive mechanisms in the same pixel. Comprised of a metallodielectric grating made of TiOx nanowires sandwiched between Ag thin film and Ag substrate, the design can exhibit either a Mie resonance or a localized plasmonic resonance depending on the polarization of incident light, resulting in dramatically different color states. Due to the periodicity, the grating also diffracts light, providing an additional color state. Since diffraction can be turned on or off by the degree of coherence of the incoming light, both Mie and plasmonic colors can be modulated using objective lenses with different numerical apertures. Exploiting the different color generating modes, we encode four layers of information in a pixel array, where each layer is unveiled using a different combination of excitation and imaging settings. These results introduce new possibilities for data encryption, anticounterfeiting, and data storage.

High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors.

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO2 shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO2 coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.