Plasmonic Effect Research Articles

Chiral and Quantum Plasmonic Sensors: New Frontiers in Selective and Ultra-Sensitive Sensing.

Surface Plasmon Polaritons (SPPs) and Localized Surface Plasmon Resonances (LSPRs) are fundamental phenomena in plasmonics that enable the confinement of electromagnetic waves beyond the diffraction limit. This confinement results in a significant enhancement of the electric field, making this phenomenon particularly beneficial for sensitive detection applications. However, conventional plasmonic sensors face several challenges, notably their difficulty in distinguishing chiral molecules, which are vital in drug development. Furthermore, these sensors exhibit sensitivity issues and energy losses, leading to broader resonance peaks and diminished signal-to-noise ratios. Recent research has concentrated on integrating chirality and quantum effects in plasmonics to overcome these limitations. Particularly, the development of plasmonic sensors with exceptional sensitivity and precision at scales smaller than the diffraction limit. This review assesses the latest advancements in chiral and quantum plasmonic sensing technologies. The first section details the theory and operational principles of conventional sensors based on SPPs and LSPRs. The second section discusses recent developments in chiral plasmonic sensors, while the third section focuses on plasmonic quantum sensing, highlighting contemporary findings. Specifically, this section emphasizes quantum-enhanced sensing techniques that mitigate shot noise, a significant barrier to single-molecule detection. The concluding section summarizes the review and identifies potential future research directions.

Plasmonic Cu-supported amorphous RuP for efficient photothermal CO2 hydrogenation to CO.

The hydrogenation of carbon dioxide into profitable chemicals is a viable path toward achieving the objective of carbon neutrality. However, the typical approach for hydrogenation of CO2 heavily relies on thermally driven catalysis at high temperatures, which is not aligned with the goals of carbon neutrality. Thus, there is a critical need to explore new catalytic methods for the high-efficiency conversion of CO2. Herein, we present a new class of catalysts, featuring phosphorus-doped amorphous ruthenium nanoparticles supported on copper nanoparticles, which capitalizes on the plasmonic effects of copper to achieve the photothermal transformation of CO2 to CO within a gas-solid flow system. Our findings indicated that the reaction efficiency in the presence of photothermal energy was over eight times greater than that with thermal energy alone. The catalyst system exhibited nearly 100% selectivity towards CO under mild conditions, with an impressive CO yield of 123.16 mmol g-1 h-1. This study highlights the significant potential of amorphous metal phosphides in photocatalytic CO2 hydrogenation under mild conditions and offers a fresh avenue for the robust catalysis of amorphous materials.

Near-field-driven thermal phonon lasing.

The extreme electromagnetic near-field environment of nanoplasmonic resonators and metamaterials can give rise to unprecedented electromagnetic heating effects, enabling large and manipulable temperature gradients on the order of 101-102 K/nm. In this Letter, by interfacing traditional semiconductor quantum dots with industry-grade plasmonic transducer technology, we demonstrate that the near-field-induced thermal gradient can facilitate the requisite population inversion for coherent phonon amplification and lasing at the nanoscale. Our detailed analysis uncovers both the characteristics and parameter sensitivity of inversion and relaxation oscillations in the system, thereby unveiling hitherto unexplored opportunities for leveraging plasmonic near-field effects in the context of quantum thermodynamics and phononics.

High-performance large-area terahertz detector based on the WTe2 film of Weyl semimetal with a subwavelength zigzag line array

A large-area terahertz detector based on a subwavelength zigzag line array on the Weyl semimetal film of WTe2 was designed and prepared. A high-performance device, on account of the combination of the absorption characteristic of Weyl semimetals for long-wave photons with low energy and the enhancement effect of the localized surface plasmon by virtue of a subwavelength zigzag line array structure, has been demonstrated by a numerical simulation and experimental verification. A high-performance detection ability of a large 3.8 mm square area for a 0.1 THz wave at room temperature was verified. The characteristic parameters of the detection ability for the device with a 70 µm line width of WTe2 under the bias voltage of 20 V were obtained with a photocurrent responsivity (R i ) of 9.51mAW−1, a noise equivalent power (NEP) of 89.3pWHz−1/2, and a detectivity (D∗) of 4.25×109cmHz1/2W−1.

Polarization-Dependent Plasmon-Induced Doping and Strain Effects in MoS2 Monolayers on Gold Nanostructures.

Monolayers of transition-metal dichalcogenides, such as MoS2, have attracted significant attention for their exceptional electronic and optical properties, positioning them as ideal candidates for advanced optoelectronic applications. Despite their strong excitonic effects, the atomic-scale thickness of these materials limits their light absorption efficiency, necessitating innovative strategies to enhance light-matter interactions. Plasmonic nanostructures offer a promising solution to overcome those challenges by amplifying the electromagnetic field and also introducing other mechanisms, such as hot electron injection. In this study, we investigate the vibrational and optical properties of MoS2 monolayer deposited on gold substrates and gratings, emphasizing the role of strain and plasmonic effects using conventional spectroscopic techniques. Our results reveal significant biaxial strain in the supported regions and a uniaxial strain gradient in the suspended ones, showing a strain-induced exciton and carrier funneling effect toward the center of the nanogaps. Moreover, we observed an additional polarization-dependent doping mechanism in the suspended regions. This effect was attributed to localized surface plasmons generated within the slits, as confirmed by numerical simulations, which may decay nonradiatively into hot electrons and be injected into the monolayer. Photoluminescence measurements further demonstrated a polarization-dependent trion-to-A exciton intensity ratio, supporting the hypothesis of additional plasmon-induced doping. These findings provide a comprehensive understanding of the strain-mediated funneling effects and plasmonic interactions in hybrid MoS2/Au nanostructures, offering valuable insights for developing high-efficiency photonic devices and quantum technologies, including polarization-sensitive detectors and excitonic circuits.

Coupling mechanisms of plasmon resonance and Bi3+ emission in YAG: Bi, Ce, Yb epitaxial films at low temperatures

This paper is devoted to the investigation of the plasmonic effect of metal nanoparticles (NPs) formed on the surface of the YAG: Bi, Ce, Yb phosphors in a temperature range between 4 and 300 K. Combination of a thin conversion layer with silver plasmonic nanostructures leads to increase of sensitizer absorption and emission efficiency. Enhancement of Bi3+ luminescence in YAG epitaxial films with Ag NPs was observed upon cooling the samples below 200 K. High enhancement factors were associated with closely matching the maximum of plasmon extinction and Bi3+ emission bands. The maximum value of enhancement factor near 170% at 4 K was obtained. It is shown that temperature decrease causes an increase in the EM field intensity around the NPs, the probability of spontaneous recombination, the penetration depth of the localized surface plasmon resonances (LSPR) into the substrate, and the adjustment of the position of the LSPR. Simultaneous action of all these factors leads to Bi3+ emission intensity enhancement. Comparative analysis of the Finite-Difference Time-Domain (FDTD) simulation data vs. experimental results of the temperature behavior of plasmon absorption spectra, luminescence spectra of Bi3+ ions, and their decay kinetics confirms the correctness of the proposed mechanisms.

Scalable Fabrication of Light-Responsive Superhydrophobic Composite Phase Change Materials via Bionic-Engineered Wood for Solar–Thermal Energy Management

The growing demand for sustainable energy storage solutions has underscored the importance of phase change materials (PCMs) for thermal energy management. However, traditional PCMs are always inherently constrained by issues such as leakage, poor thermal conductivity, and lack of solar energy conversion capacity. Herein, a multifunctional composite phase change material (CPCM) is developed using a balsa-derived morphology genetic scaffold, engineered via bionic catechol surface chemistry. The scaffold undergoes selective delignification, followed by a simple, room-temperature polydopamine (PDA) modification to deposit Ag nanoparticles (Ag NPs) and graft octadecyl chains, resulting in a superhydrophobic hierarchical structure. This superhydrophobicity plays a critical role in preventing PCM leakage and enhancing environmental adaptability, ensuring long-term stability under diverse conditions. Encapsulating stearic acid (SA) as the PCM, the CPCM exhibits exceptional stability, achieving a high latent heat of 175.5 J g−1 and an energy storage efficiency of 87.7%. In addition, the thermal conductivity of the CPCM is significantly enhanced along the longitudinal direction, a 2.1-fold increase compared to pure SA, due to the integration of Ag NPs and the unidirectional wood architecture. This synergy also drives efficient photothermal conversion via π-π stacking interactions of PDA and the surface plasmon effects of Ag NPs, enabling rapid solar-to-thermal energy conversion. Moreover, the CPCM demonstrates remarkable water resistance, self-cleaning ability, and long-term thermal reliability, retaining its functionality through 100 heating–cooling cycles. This multifunctional balsa-based CPCM represents a breakthrough in integrating phase-change behavior with advanced environmental adaptability, offering promising applications in solar–thermal energy systems.

Interplay of plasmonic and charge transfer effects for ultrasensitive Ag–WO3/TiO2 photonic crystal SERS sensors

Cooperative plasmonic, photonic and charge transfer amplification effects in hybrid metal/semiconductor Ag–WO3/TiO2 inverse opal substrates lead to ultrasensitive SERS detection of 4-mercaptobenzoic acid.

Ti3C2T x MXene Thin Films and Intercalated Species Characterized by IR-to-UV Broadband Ellipsometry.

MXenes are two-dimensional (2D) materials with versatile applications in optoelectronics, batteries, and catalysis. To unlock their full potential, it is crucial to characterize MXene interfaces and intercalated species in more detail than is currently possible with conventional optical spectroscopies. Here, we combine ultra-broadband ellipsometry and transmission spectroscopy from the mid-infrared (IR) to the deep-ultraviolet (UV) to probe quantitatively the composition, structure, transport, and optical properties of spray-coated Ti3C2T x MXene thin films with varying material properties. We find film thickness heterogeneity and surface roughness in the low-nanometer range as well as depth-dependent conductivity properties, which we quantify with a graded Drude model. The optically determined sheet resistance is confirmed by four-point probe measurements. Furthermore, we employ density-functional-theory calculations to assign the observed absorption bands in the MXene dielectric function to various interband transitions from mixed MXene surface terminations. The prominent 1.48 eV (833 nm) spectral feature is found to be related to oxygen termination. Additional plasmonic effects are also suggested. Finally, we leverage the chemical sensitivity of state-of-the-art IR ellipsometry to separate the fingerprints of intercalated species within the MXene from the dominant Drude contributions, presenting for the first time a set of infrared optical constants of intercalated water. This work lays the foundation for optical metrology for interface engineering of MXene and other 2D materials.

Enhanced Visible Light Controlled Glucose Photo-Reforming Using a Composite WO3/Ag/TiO2 Photoanode: Effect of Incorporated Plasmonic Ag Nanoparticles.

WO3/Ag/TiO2 composite photoelectrodes were formed via the high-temperature calcination of a WO3 film, followed by the sputtering of a very thin silver film and deposition of an overlayer of commercial TiO2 nanoparticles. These synthetic photoanodes were characterized in view of the oxidation of a model organic compound glucose combined with the generation of hydrogen at a platinum cathode. During prolonged photoelectrolysis under simulated solar light, these photoanodes demonstrated high and stable photocurrents of ca. 4 mA cm-2 due, on one hand, to the occurrence of the so-called photocurrent doubling and, on the other hand, to the plasmonic effect of Ag nanoparticles. The post-photoelectrolysis analyses of the electrolyte demonstrated the formation of high-value final glucose photo-reforming products, principally gluconic acid, erythrose and formic acid.

Regulating Charge Separation Via Periodic Array Nanostructures for Plasmon-Enhanced Water Oxidation.

Plasmonic resonance intensity in metallic nanostructures plays a crucial role in charge generation and separation, directly affecting plasmon-induced photocatalytic activity. Engineering strategies to enhance plasmonic effects involve designing specific nanostructures, such as triangular nanoplates with sharp corners or dimer nanostructures with hot spots. However, these approaches often lead to a trade-off between enhanced plasmonic intensity and resonance energy, which ultimately determines local charge density and photocatalytic performance. Here, inspired by theoretical predications, it is shown that a flexibly controlled plasmonic photocatalyst, consisting of an ordered array of Au nanoparticles on a SrTiO3 surface, exhibits an enhanced surface plasmon resonance (SPR) intensity while maintaining a constant SPR resonant energy, due to the presence of surface lattice resonance. This trade-off results in improved charge separation efficiency and an increase in local charge density at catalytically active sites, as verified by theoretical simulations, surface photovoltage microscopy, and ultrafast transient absorption spectroscopy. Moreover, the optimized periodic photocatalyst shows a 7-fold increase in water oxidation activity over disordered nanostructures. This work provides a novel approach for balancing the intensity and energy of SPR, which will contribute to optimizing photocatalytic activity on plasmonic platforms.

Tunable Infrared Emissivity Using Laser‐Sintered Liquid Metal Nanoparticle Films

AbstractThis paper describes laser exposure to tune the infrared (IR) emissivity of a film of eutectic gallium indium (EGaIn) particles. EGaIn – a liquid metal at room temperature – forms a native oxide that keeps particles of the metal from spontaneously percolating. Photothermal energy from a CO2 laser percolates the particles into a conductive network. Here, it also causes a decrease in the IR emissivity of the film of particles from 0.4 to 0.24 over the range of 7.5–13 µm wavelength (measured by an IR camera) with the increase of laser fluence from 1.4 to 1.9 J cm−2. The particles percolate most prominently at the bottom of the film, and thus, the apparent surface roughness does not change with laser exposure. This finding suggests the decrease in emissivity is not due to changes in the film's topography. Instead, the change in IR emissivity is attributed to a loss of the surface plasmonic resonance effect of EGaIn particles in the IR range after the sintering, which is confirmed by optical simulations. As a demonstration, it is shown that the ability to change the emissivity makes it possible to encrypt messages and camouflage laser‐processed patterns.

Time-dependent quantum/continuum modeling of plasmon-enhanced electronic circular dichroism.

In this work, we present a multiscale real-time approach to study the plasmonic effects of a metal nanoparticle (NP) on the electronic circular-dichroism (ECD) spectrum of a chiral molecule interacting with it. The method is based on the time-evolution of the molecule's time-dependent wavefunction, expanded in the eigenstates of a perturbed Hamiltonian. A quantum description of the molecular system is coupled to a classical representation of the NP via a continuum model. The method is applied to methyloxirane and peridinin at various distances (1, 3, and 5nm) with respect to a gold NP surface. While no remarkable effect is observed for methyloxirane at any studied distance, an enhancement appears when the peridinin lies at 1nm and the pulse is linearly polarized perpendicularly to the molecular axis, with the ECD signal centered at 4.1eV increased by a factor of around 20. These results are rationalized looking at the gap between the plasmonic peak of the NP at around 2.5eV and the molecular excitations: the smaller the gap between molecular and plasmonic excitations, the larger the plasmonic enhancement of the ECD signal. Moreover, ECD peaks are selectively enhanced due to the favorable coupling between the pulse polarization and the combined effect of electric and magnetic dipole moments. This approach allows one to go through the electronic structure and dynamics of chiral molecules for obtaining a realistic description of plasmon-mediated ECD spectra, e.g., paving the way to applications to molecules of biological relevance interacting with nanostructures of experimental interest.

Origin of electromagnetic wave amplification in 20-μm-diameter plasmonic whispering gallery mode resonators: the effects of long-range surface plasmons and low effective refractive indices

Origin of electromagnetic wave amplification in 20-μm-diameter plasmonic whispering gallery mode resonators: the effects of long-range surface plasmons and low effective refractive indices

Suppression of the plasmonic heating effect in SERS measurement by coating graphene on the Ag@AAO substrate surface

The plasmonic heating effect on the substrate surface prompted by laser radiation used in surface-enhanced Raman spectroscopy (SERS) measurement can inhibit the practical application of the SERS technique. Graphene, due to its high photothermal conversion and thermal conductivity, could provide a rapid path for dissipating the heat generated from hot electrons. In this work, the diluted graphene was spin-coated onto the anodized aluminum oxide (AAO) template modified with Ag films (G@Ag@AAO) to suppress the plasmonic heating effect. Theoretical simulations demonstrated that the ultrathin graphene coating can promote the plasmonic coupling between adjacent Ag nanoislands. The in-situ SERS monitoring revealed that the G@Ag@AAO substrate exhibits better signal stability than the pristine Ag@AAO substrate. Besides, ultraviolet (UV) radiation caused cross-linking of PVA (polyvinyl alcohol)/G (graphene) nanocomposites on the Ag@AAO substrate surface, which made the PVA/G@Ag@AAO substrate exhibit more excellent long-term detection stability in solution due to the increases of PVA/G interfacial adhesion toughness. In addition, the excellent λ-DNA (dsDNA) identification ability of PVA/G@Ag@AAO substrate suggests its broad prospect in biomolecular sensing and genetic engineering applications.

Machine-Learning Mental-Fatigue-Measuring μm-Thick Elastic Epidermal Electronics (MMMEEE).

Electrophysiological (EP) signals are key biomarkers for monitoring mental fatigue (MF) and general health, but state-of-the-art wearable EP-based MF monitoring systems are bulky and require user-specific, labeled data. Ultrathin epidermal electrodes with high performance are ideal for constructing imperceptive EP sensing systems; however, the lack of a simple and scalable fabrication delays their application in MF recognition. Here, we report a facile, scalable printing-welding-transferring strategy (PWT) for printing μm-thickness micropatterned silver nanowires (AgNWs)/sticky polydimethylsiloxane, welding the AgNWs via plasmonic effect, and transferring the electrode to skin as tattoos. The PWT provides electrodes with conformability, comfort, and stability for EP sensing. Leveraging the facile and scalable PWT, we develop plug-and-play wireless multimodal epidermal electronics integrated with an unsupervised transfer learning (UTL) scheme for MF recognition across various users. The UTL adaptively minimizes the intersubject difference and achieves high accuracy, without demand of expensive computation and labels from target users.

Polydopamine Inspired Silver Nanoflower SERS Substrate for Highly Sensitive Detection of Nivalenol in Food Samples: Unveiling Biocompatibility in Mammalian Cells

Surface-enhanced Raman spectroscopy (SERS) is a reliable analytical technique for mycotoxins' swift and precise determination. However, thus far, there has been no exploration of SERS for the quantitative detection of nivalenol (NIV). In this study, we engineered polydopamine-coated silver nanoflower (PDA-AgNFs) SERS substrates with potent "hot spots" to enhance Raman signals of NIV. These substrates exhibited exceptional SERS enhancement capabilities in detecting and quantifying the target analyte, demonstrating uniformity (with a relative standard deviation of SERS signals, RSD = 4.1% for substrate-to-substrate test and 3.24% for spot-to-spot test), an enhancement factor of 2.87 × 10^6 for rhodamine 6B (R6G), and detection sensitivity as low as 1 femtomolar (10^-15 M) for R6G probe molecule. Furthermore, we successfully employed the PDA-AgNFs SERS substrates for the first time to detect NIV in corn, horse beans, and mushroom samples. The calibration curve exhibited a satisfactory linear fit based on SERS intensities at different NIV concentrations, with a detection limit (LOD) of 0.22 nM (S/N = 3) for the proposed approach. Intriguingly, the MTT assay experiment demonstrated the biocompatibility of PDA-AgNFs, showing no toxicity against mammalian NIH-3T3 cells. These biocompatible substrates, endowed with intense plasmonic effects and binding sites, showcased remarkable Raman enhancement, offering an efficient, label-free, and rapid SERS-based analysis of NIV in real samples. Keywords: Polydopamine-inspired, silver nanoflowers, mycotoxins, nivalenol, biocompatibility. Figure 1

Preparation and characterization of temperature-induced ultrasensitive SERS large-scale vertical Au nanosphere dimers

Plasmonic dimers have a very wide range of applications as a unique platform for studying the fundamental effects of plasmonics. Most dimer structures are prepared by chemical methods and direct-writing methods, such as coupling agents and lithography. These methods are often complex and expensive. Here, we prepared Au nanospheres (AuNSs) by layer-by-layer (LBL) deposition, used polymethyl methacrylate (PMMA) as a spacer layer, and then annealed the deposited AuNSs to orient the assembly and integrate them together. In this paper, suitable PMMA spin coating conditions and optimal annealing temperatures were explored, and large-scale AuNSs-PMMA-AuNSs(NSs-P-NSs) composed of vertical Au nanosphere dimers were prepared successfully. The detection limits of this substrate can reach 4 × 10−12 M/L and 4 × 10−10 M/L for Rhodamine 6 G (R6G) and Crystal Violet (CV), respectively, demonstrating excellent Raman activity. In addition, the sensitivity of detecting aspartame (APM) is 0.015625 g/L. This method is not only simple to operate but also allows the preparation of a large-scale uniform substrate with excellent detection capabilities.

Photocatalytic Seawater Splitting by Earth-Abundant Catalysts: Metal-Semiconductor Metamaterials Made of Plasmonic Magnesium Diboride and Transitional Metal Dichalcogenides.

Metal-semiconductor metamaterials hold great promise for photocatalytic water splitting due to their excellent light harvesting in a broad spectral range as well as efficient charge carrier generation and transfer. In the majority of such metamaterials, semiconductors are used to initiate the water splitting reaction, while their metal counterparts are employed to improve light harvesting through plasmonic effects. Here, we describe for the first time an exceptional reversed case of metal-semiconductor photocatalysts in which metals are used to initiate the water splitting reaction and semiconductors are employed to improve light harvesting through the blackbody effect and serve as co-catalysts. The studied photoanodes are made of non-noble plasmonic MgB2 combined with transition metal dichalcogenides (TMDCs). The plasmonic resonances of the MgB2 component contribute to field confinement, plasmon-exciton coupling, and hot-electron transfer providing an enhancement of photoactivity in the entire solar spectrum capable of water splitting. The TMDC component provides impedance matching and enhances light absorption by the metal catalyst. We demonstrate seawater splitting with MgB2-TMDCs photoanodes attaining current densities of ~3 mA cm-2 at solar radiation. The overall efficiency of hydrogen production in seawater splitting by sunlight with the help of the studied photoanodes is 3 % at a bias voltage of Vbias=0.3 V.

Unraveling the Plasmonic Effect of Au in Promoting Photocatalytic H2 Generation and Organic Synthesis

Unraveling the Plasmonic Effect of Au in Promoting Photocatalytic H₂ Generation and Organic Synthesis