Showing papers on "Surface plasmon resonance published in 2019"

Multicomponent Plasmonic Nanoparticles: From Heterostructured Nanoparticles to Colloidal Composite Nanostructures.

Abstract: Plasmonic nanostructures possessing unique and versatile optoelectronic properties have been vastly investigated over the past decade. However, the full potential of plasmonic nanostructure has not yet been fully exploited, particularly with single-component homogeneous structures with monotonic properties, and the addition of new components for making multicomponent nanoparticles may lead to new-yet-unexpected or improved properties. Here we define the term "multi-component nanoparticles" as hybrid structures composed of two or more condensed nanoscale domains with distinctive material compositions, shapes, or sizes. We reviewed and discussed the designing principles and synthetic strategies to efficiently combine multiple components to form hybrid nanoparticles with a new or improved plasmonic functionality. In particular, it has been quite challenging to precisely synthesize widely diverse multicomponent plasmonic structures, limiting realization of the full potential of plasmonic heterostructures. To address this challenge, several synthetic approaches have been reported to form a variety of different multicomponent plasmonic nanoparticles, mainly based on heterogeneous nucleation, atomic replacements, adsorption on supports, and biomolecule-mediated assemblies. In addition, the unique and synergistic features of multicomponent plasmonic nanoparticles, such as combination of pristine material properties, finely tuned plasmon resonance and coupling, enhanced light-matter interactions, geometry-induced polarization, and plasmon-induced energy and charge transfer across the heterointerface, were reported. In this review, we comprehensively summarize the latest advances on state-of-art synthetic strategies, unique properties, and promising applications of multicomponent plasmonic nanoparticles. These plasmonic nanoparticles including heterostructured nanoparticles and composite nanostructures are prepared by direct synthesis and physical force- or biomolecule-mediated assembly, which hold tremendous potential for plasmon-mediated energy transfer, magnetic plasmonics, metamolecules, and nanobiotechnology.

Nanoplasmonic Sensor Detects Preferential Binding of IRSp53 to Negative Membrane Curvature.

Abstract: Biosensors based on plasmonic nanostructures are widely used in various applications and benefit from numerous operational advantages. One type of application where nanostructured sensors provide unique value in comparison with, for instance, conventional surface plasmon resonance, is investigations of the influence of nanoscale geometry on biomolecular binding events. In this study, we show that plasmonic "nanowells" conformally coated with a continuous lipid bilayer can be used to detect the preferential binding of the insulin receptor tyrosine kinase substrate protein (IRSp53) I-BAR domain to regions of negative surface curvature, i.e., the interior of the nanowells. Two different sensor architectures with and without an additional niobium oxide layer are compared for this purpose. In both cases, curvature preferential binding of IRSp53 (at around 0.025 nm-1 and higher) can be detected qualitatively. The high refractive index niobium oxide influences the near field distribution and makes the signature for bilayer formation less clear, but the contrast for accumulation at regions of negative curvature is slightly higher. This work shows the first example of analyzing preferential binding of an average-sized and biologically important protein to negative membrane curvature in a label-free manner and in real-time, illustrating a unique application for nanoplasmonic sensors.

Plasmon-Driven Catalysis on Molecules and Nanomaterials.

Abstract: As a new class of photocatalysts, plasmonic noble metal nanoparticles with the unique ability to harvest solar energy across the entire visible spectrum and produce effective energy conversion have been explored as a promising pathway for the energy crisis. The resonant excitation of surface plasmon resonance allows the nanoparticles to collect the energy of photons to form a highly enhanced electromagnetic field, and the energy stored in the plasmonic field can induce hot carriers in the metal. The hot electron-hole pairs ultimately dissipate by coupling to phonon modes of the metal nanoparticles, resulting in a higher lattice temperature. The plasmonic electromagnetic field, hot electrons, and heat can catalyze chemical reactions of reactants near the surface of the plasmonic metal nanoparticles. This Account summarizes recent theoretical and experimental advances on the excitation mechanisms and energy transfer pathways in the plasmonic catalysis on molecules. Especially, current advances on plasmon-driven crystal growth and transformation of nanomaterials are introduced. The efficiency of the chemical reaction can be dramatically increased by the plasmonic electromagnetic field because of its higher density of photons. Similar to traditional photocatalysis, energy overlap between the plasmonic field and the HOMO-LUMO gap of the reactant is needed to realize resonant energy transfer. For hot-carrier-driven catalysis, hot electrons generated by plasmon decay can be transferred to the reactant through the indirect electron transfer or direct electron excitation process. For this mechanism, the energy of hot electrons needs to overlap with the unoccupied orbitals of the reactant, and the particular chemical channel can be selectively enhanced by controlling the energy distribution of hot electrons. In addition, the local thermal effect following plasmon decay offers an opportunity to facilitate chemical reactions at room temperature. Importantly, surface plasmons can not only catalyze chemical reactions of molecules but also induce crystal growth and transformation of nanomaterials. As a new development in plasmonic catalysis, plasmon-driven crystal transformation reveals a more powerful aspect of the catalysis effect, which opens the new field of plasmonic catalysis. We believe that this Account will promote clear understanding of plasmonic catalysis on both molecules and materials and contribute to the design of highly tunable catalytic systems to realize crystal transformations that are essential to achieve efficient solar-to-chemical energy conversion.

Sunlight induced photo-thermal synergistic catalytic CO2 conversion via localized surface plasmon resonance of MoO3−x

Abstract: Photocatalytic conversion of CO2 to solar fuels is considered an alternative approach for simultaneously mitigating the greenhouse effect and solving energy shortage. The efficient light harvesting and the thermochemical conversion have been demanding quests in photocatalysis due to the relatively low solar energy utilization efficiency. In this work, oxygen vacancies are induced in MoO3 for improving photo-thermal CO2 reduction efficiency by capturing near-infrared (NIR) photons. The localized surface plasmon resonance (LSPR) of MoO3−x triggered by oxygen vacancies enables the efficient capture of NIR photons. Additionally, oxygen vacancies can promote the carrier separation, improve CO2 adsorption on the defective surface and lower the barrier of CO2 hydrogenation during the conversion process. As a result, MoO3−x displayed dramatically enhanced photo-thermal synergistic CO2 reduction under simulated sunlight (UV-Vis-IR) irradiation than MoO3. The amount of CO produced by MoO3−x can reach 10.3 μmol g−1 h−1, which is 20 times higher than that of MoO3 (0.52 μmol g−1 h−1). And the CH4 production of MoO3−x can reach 2.08 μmol g−1 h−1, which is 52 times higher than that of MoO3 (0.04 μmol g−1 h−1). In situ FT-IR and theoretical calculations also proved the enhanced activity of MoO3−x. This work highlights the significance of defect engineering for improving the photo-thermal catalytic conversion of CO2.

Surface Plasmon Resonance Based Titanium Coated Biosensor for Cancer Cell Detection

Abstract: A new optimized bowl-shaped mono-core surface plasmon resonance based cancer sensor is proposed for the rapid detection of different types of cancer affected cell. By considering the refractive index of each individual cancer contaminated cell with respect to their normal cell, some major optical parameters variation are observed. Moreover, the cancerous cell concentration is considered at 80% in liquid form and the detection method is finite element method with 2 100 390 mesh elements. The variation of spectrum shift is obtained by plasmonic band gap between the silica and cancer cell part which is separated by a thin (35 nm) titanium film coating. The proposed sensor depicts a high birefringence of 0.04 with a maximum coupling length of 66 $\mu$ m. However, the proposed structure provides an optimum wavelength sensitivity level between about 10 000 nm/RIU and 17 500 with a resolution of the sensor between 1.5 × 10−2 and 9.33 × 10−3 RIU. Also, the transmittance variance of the cancerous cell ranges from almost 3300 to 6100 dB/RIU and the amplitude sensitivity ranges nearly between −340 and −420 RIU $^{-1}$ for different cancer cells in major polarization mode with the maximum detection limit of 0.025. Besides, the overall sensitivity performance is measured with respect to their normal cells which can be better than any other prior structures that have already proposed.

Collective excitation of plasmon-coupled Au-nanochain boosts photocatalytic hydrogen evolution of semiconductor.

Abstract: Localized surface plasmon resonance (LSPR) offers a valuable opportunity to improve the efficiency of photocatalysts. However, plasmonic enhancement of photoconversion is still limited, as most of metal-semiconductor building blocks depend on LSPR contribution of isolated metal nanoparticles. In this contribution, the concept of collective excitation of embedded metal nanoparticles is demonstrated as an effective strategy to enhance the utilization of plasmonic energy. The contribution of Au-nanochain to the enhancement of photoconversion is 3.5 times increase in comparison with that of conventional isolated Au nanoparticles. Experimental characterization and theoretical simulation show that strongly coupled plasmonic nanostructure of Au-nanochain give rise to highly intensive electromagnetic field. The enhanced strength of electromagnetic field essentially boosts the formation rate of electron-hole pair in semiconductor, and ultimately improves photocatalytic hydrogen evolution activity of semiconductor photocatalysts. The concept of embedded coupled-metal nanostructure represents a promising strategy for the rational design of high-performance photocatalysts.

Highly Sensitive SPR Biosensor Based on Graphene Oxide and Staphylococcal Protein A Co-Modified TFBG for Human IgG Detection

Abstract: A highly sensitive optical fiber surface plasmon resonance (SPR) biosensor based on graphene oxide (GO) and staphylococcal protein A (SPA) co-modified tilted fiber Bragg grating (TFBG) is proposed and demonstrated for the detection of human immunoglobulin G (IgG) for the first time. The gold film on the surface of the sensor was first fixed with GO and then modified with an SPA to improve the sensitivity of the sensor. Large specific surface area and abundant functional groups of GO can adsorb more antibodies. The combination of SPA and the antibody molecule Fc region makes the Fab area with antigen-binding sites extend outward, resulting in highly oriented antibody immobilization on the sensor surface and high antigen–antibody binding efficiency. The experimental results show that the sensitivity as well as the limit of detection of GO-SPA-modified TFBG-SPR biosensor is around 0.096 dB/( $\mu \text{g}$ /mL) and $0.5~\mu \text{g}$ /mL, showing better responses to human IgG solutions with a concentration range of 30– $100~\mu \text{g}$ /mL compared with the TFBG-SPR biosensors modified singly with GO or SPA. The biosensor exhibits the advantages of small size, ease of fabrication, high sensitivity, label-free, and rapid response, and provides a new solution for detecting low concentration of biological solution, presenting great application potential in the biochemistry field.

Boosting Electrocatalytic Hydrogen Evolution over Metal–Organic Frameworks by Plasmon‐Induced Hot‐Electron Injection

Abstract: Efficient hydrogen evolution via electrocatalytic water splitting holds great promise in modern energy devices. Herein, we demonstrate that the localized surface plasmon resonance (LSPR) excitation of Au nanorods (NRs) dramatically improves the electrocatalytic hydrogen evolution activity of CoFe-metal-organic framework nanosheets (CoFe-MOFNs), leading to a more than 4-fold increase of current density at -0.236 V (vs. RHE) for Au/CoFe-MOFNs composite under light irradiation versus in dark. Mechanistic investigations reveal that the hydrogen evolution enhancement can be largely attributed to the injection of hot electrons from AuNRs to CoFe-MOFNs, raising the Fermi level of CoFe-MOFNs, facilitating the reduction of H2 O and affording decreased activation energy for HER. This study highlights the superiority of plasmonic excitation on improving electrocatalytic efficiency of MOFs and provides a novel avenue towards the design of highly efficient water-splitting systems under light irradiation.

Binding to Nanopatterned Antigens is Dominated by the Spatial Tolerance of Antibodies

Abstract: Although repetitive patterns of antigens are crucial for certain immune responses, an understanding of how antibodies bind and dynamically interact with various spatial arrangements of molecules is lacking. Hence, we introduced a new method in which molecularly precise nanoscale patterns of antigens are displayed using DNA origami and immobilized in a surface plasmon resonance set-up. Using antibodies with identical antigen-binding domains, we found that all the subclasses and isotypes studied bind bivalently to two antigens separated at distances that range from 3 to 17 nm. The binding affinities of these antibodies change with the antigen distances, with a distinct preference for antigens separated by approximately 16 nm, and considerable differences in spatial tolerance exist between IgM and IgG and between low- and high-affinity antibodies. The ordered display of antigen patterns on DNA origami platforms combined with surface plasmon resonance chips allows the investigation of the affinity and kinetics of the antigen–antibody bivalent binding in relation to the antigen distance and antibody flexibility.

Plasmon damping depends on the chemical nature of the nanoparticle interface

Abstract: The chemical nature of surface adsorbates affects the localized surface plasmon resonance of metal nanoparticles. However, classical electromagnetic simulations are blind to this effect, whereas experiments are typically plagued by ensemble averaging that also includes size and shape variations. In this work, we are able to isolate the contribution of surface adsorbates to the plasmon resonance by carefully selecting adsorbate isomers, using single-particle spectroscopy to obtain homogeneous linewidths, and comparing experimental results to high-level quantum mechanical calculations based on embedded correlated wavefunction theory. Our approach allows us to indisputably show that nanoparticle plasmons are influenced by the chemical nature of the adsorbates 1,7-dicarbadodecaborane(12)-1-thiol (M1) and 1,7-dicarbadodecaborane(12)-9-thiol (M9). These surface adsorbates induce inside the metal electric dipoles that act as additional scattering centers for plasmon dephasing. In contrast, charge transfer from the plasmon to adsorbates—the most widely suggested mechanism to date—does not play a role here.

Taking the Heat Off of Plasmonic Chemistry

Abstract: Several chemical reactions catalyzed by plasmonic nanoparticles show enhanced rates under visible-light-excitation of the localized surface plasmon resonance of the nanoparticles. But it has been argued that there is an associated photothermal effect that can complicate the analysis and/or interpretation of the nature of the role played by plasmon excitation. This Viewpoint discusses this dilemma and provides some best practices for accounting for photothermal contributions in plasmon-excitation-driven chemistry. A classification of plasmonic chemistry into plasmonic photocatalysis and plasmonic photosynthesis is also proposed. It is argued that photosynthetic reactions, which require a Gibb's free energy input, constitute an ultimate test of the non-thermal, photochemical action of plasmon excitation.

EM-Wave Biosensors: A Review of RF, Microwave, mm-Wave and Optical Sensing.

Abstract: This article presents a broad review on optical, radio-frequency (RF), microwave (MW), millimeter wave (mmW) and terahertz (THz) biosensors. Biomatter-wave interaction modalities are considered over a wide range of frequencies and applications such as detection of cancer biomarkers, biotin, neurotransmitters and heart rate are presented in detail. By treating biological tissue as a dielectric substance, having a unique dielectric signature, it can be characterized by frequency dependent parameters such as permittivity and conductivity. By observing the unique permittivity spectrum, cancerous cells can be distinguished from healthy ones or by measuring the changes in permittivity, concentration of medically relevant biomolecules such as glucose, neurotransmitters, vitamins and proteins, ailments and abnormalities can be detected. In case of optical biosensors, any change in permittivity is transduced to a change in optical properties such as photoluminescence, interference pattern, reflection intensity and reflection angle through techniques like quantum dots, interferometry, surface enhanced raman scattering or surface plasmon resonance. Conversely, in case of RF, MW, mmW and THz biosensors, capacitive sensing is most commonly employed where changes in permittivity are reflected as changes in capacitance, through components like interdigitated electrodes, resonators and microstrip structures. In this paper, interactions of EM waves with biomatter are considered, with an emphasis on a clear demarcation of various modalities, their underlying principles and applications.

High Sensitivity Surface Plasmon Resonance Sensor Based on Two-Dimensional MXene and Transition Metal Dichalcogenide: A Theoretical Study

Abstract: MXene, a new class of two-dimensional nanomaterials, have drawn increasing attention as emerging materials for sensing applications. However, MXene-based surface plasmon resonance sensors remain largely unexplored. In this work, we theoretically show that the sensitivity of the surface plasmon resonance sensor can be significantly enhanced by combining two-dimensional Ti 3 C 2 T x MXene and transition metal dichalcogenides. A high sensitivity of 198 ∘ /RIU (refractive index unit) with a sensitivity enhancement of 41.43% was achieved in aqueous solutions (refractive index ∼1.33) with the employment of monolayer Ti 3 C 2 T x MXene and five layers of WS 2 at a 633 nm excitation wavelength. The integration of Ti 3 C 2 T x MXene with a conventional surface plasmon resonance sensor provides a promising approach for bio- and chemical sensing, thus opening up new opportunities for highly sensitive surface plasmon resonance sensors using two-dimensional nanomaterials.

Colloidal Self-Assembly Concepts for Plasmonic Metasurfaces

Abstract: In metallic thin films, light can drive coherent oscillations of the free electrons at the metal–dielectric interface. This oscillation, known as a surface plasmon resonance, depends on specific wavelength, polarization, and angle of incidence of the light as well as the thickness of the metallic thin film.[1] Less precision is needed to reach the resonance conditions for spherical metallic nanoparticles, for which the excitation Metallic nanostructures exhibit strong interactions with electromagnetic radiation, known as the localized surface plasmon resonance. In recent years, there is significant interest and growth in the area of coupled metallic nanostructures. In such assemblies, shortand long-range coupling effects can be tailored and emergent properties, e.g., metamaterial effects, can be realized. The term “plasmonic metasurfaces” is used for this novel class of assemblies deposited on planar surfaces. Herein, the focus is on plasmonic metasurfaces formed from colloidal particles. These are formed by selfassembly and can meet the demands of low-cost manufacturing of large-area, flexible, and ultrathin devices. The advances in high optical quality of the colloidal building blocks and methods for controlling their self-assembly on surfaces will lead to novel functional devices for dynamic light modulators, pulse sharpening, subwavelength imaging, sensing, and quantum devices. This progress report focuses on predicting optical properties of single colloidal building blocks and their assemblies, wet-chemical synthesis, and directed self-assembly of colloidal particles. The report concludes with a discussion of the perspectives toward expanding the colloidal plasmonic metasurfaces concept by integrating them with quantum emitters (gain materials) or mechanically responsive structures.

Spectral Screening of the Energy of Hot Holes over a Particle Plasmon Resonance

Abstract: Plasmonic hot carriers have been recently identified as key elements for photocatalysis at visible wavelengths. The possibility to transfer energy between metal plasmonic nanoparticles and nearby molecules depends not only on carrier generation and collection efficiencies but also on their energy at the metal–molecule interface. Here an energy screening study was performed by monitoring the aniline electro-polymerization reaction via an illuminated 80 nm gold nanoparticle. Our results show that plasmon excitation reduces the energy required to start the polymerization reaction as much as 0.24 eV. Three possible photocatalytic mechanisms were explored: the enhanced near field of the illuminated particle, the temperature increase at the metal–liquid interface, and the excited electron–hole pairs. This last phenomenon is found to be the one contributing most prominently to the observed energy reduction.

Plasmonic control of solar-driven CO2 conversion at the metal/ZnO interfaces

Abstract: Molecular-level understanding of the solar-driven CO2 conversion is of importance to design high-efficiency artificial photosynthetic systems for rebalancing the global carbon cycle. Herein, some physical insights into the surface plasmon resonance (SPR) mediated CO2 photoreduction were demonstrated with metal (Au, Ag, and Pd)/3D porous ZnO nanosheets (NSs). Such plasmonic photocatalysts were designed elaborately to expose the polar {001} facet, based on the physical prototype of field-field coupling, in order to benefit chemical polarization and activation of the inert molecule. Among these plasmonic metals, gold was found to be not only more effective for promoting the solar-driven CO2 conversion, but unique for producing the higher hydrocarbon, C2H6. A 10-fold enhanced conversion efficiency and a quantum efficiency of 1.03% were achieved on Au/ZnO NSs at ca. 80% selectivity to hydrocarbons under solar light irradiation. The characterization results indicated that the metal-semiconductor interaction enables the electron-phonon decoupling to generate more amounts of energetic electrons in the excited ZnO NSs by a proposed pathway, called the SPR energy transfer induced interband transition that promotes the semiconductor photoexcitation, kinetically accelerating the conversion. Density functional theory calculations revealed that the field-field coupling greatly intensifies the surface polarization for adsorbates, charging negatively the C atom of CO2 and making O C O bond bent, along with the electrophilic attack by two competitive paths, leading to the concomitance of CO and CH4. The loading of plasmonic metal nanoparticles alters the molecular paths of CO2 conversion by tuning thermodynamically the first dehydroxylation step, consequently the product selectivity. Especially Au plasmon, it enables the CO hydrogenation path, making CH4 faster.