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1.
Nanoscale ; 2020 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-32510097

RESUMO

Anisotropy in a crystal structure can lead to large orientation-dependent variations of mechanical, optical, and electronic properties. Material orientation control can thus provide a handle to manipulate properties. Here, a novel sputtering approach for 2D materials enables growth of ultrathin (2.5-10 nm) tellurium films with rational control of the crystalline orientation templated by the substrate. The anisotropic Te 0001 helical chains align in the plane of the substrate on highly oriented pyrolytic graphite (HOPG) and orthogonally to MgO(100) substrates, as shown by polarized Raman spectroscopy and high-resolution electron microscopy. Furthermore, the films are shown to grow in a textured fashion on HOPG, in contrast with previous reports. These ultrathin Te films cover exceptionally large areas (>1 cm2) and are grown at low temperature (25 °C) affording the ability to accommodate a variety of substrates including flexible electronics. They are robust toward oxidation over a period of days and exhibit the non-centrosymmetric P3121 Te structure. Raman signals are acutely dependent on film thickness, suggesting that optical anisotropy persists and is even enhanced at the ultrathin limit. Hall effect measurements indicate orientation-dependent carrier mobility up to 19 cm2 V-1 s-1. These large-area, ultrathin Te films grown by a truly scalable, physical vapor deposition technique with rational control of orientation/thickness open avenues for controlled orientation-dependent properties in semiconducting thin films for applications in electronic and optoelectronic devices.

2.
ACS Nano ; 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32286792

RESUMO

Nanostructures of some metals can sustain light-driven electron oscillations called localized surface plasmon resonances, or LSPRs, that give rise to absorption, scattering, and local electric field enhancement. Their resonant frequency is dictated by the nanoparticle (NP) shape and size, fueling much research geared toward discovery and control of new structures. LSPR properties also depend on composition; traditional, rare, and expensive noble metals (Ag, Au) are increasingly eclipsed by earth-abundant alternatives, with Mg being an exciting candidate capable of sustaining resonances across the ultraviolet, visible, and near-infrared spectral ranges. Here, we report numerical predictions and experimental verifications of a set of shapes based on Mg NPs displaying various twinning patterns including (101̅1), (101̅2), (101̅3), and (112̅1), that create tent-, chair-, taco-, and kite-shaped NPs, respectively. These are strikingly different from what is obtained for typical plasmonic metals because Mg crystallizes in a hexagonal close packed structure, as opposed to the cubic Al, Cu, Ag, and Au. A numerical survey of the optical response of the various structures, as well as the effect of size and aspect ratio, reveals their rich array of resonances, which are supported by single-particle optical scattering experiments. Further, corresponding numerical and experimental studies of the near-field plasmon distribution via scanning transmission electron microscopy electron-energy loss spectroscopy unravels a mode nature and distribution that are unlike those of either hexagonal plates or cylindrical rods. These NPs, made from earth-abundant Mg, provide interesting ways to control light at the nanoscale across the ultraviolet, visible, and near-infrared spectral ranges.

3.
Adv Mater ; 32(7): e1904302, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31667920

RESUMO

As elemental main group materials (i.e., silicon and germanium) have dominated the field of modern electronics, their monolayer 2D analogues have shown great promise for next-generation electronic materials as well as potential game-changing properties for optoelectronics, energy, and beyond. These atomically thin materials composed of single atomic variants of group III through group VI elements on the periodic table have already demonstrated exciting properties such as near-room-temperature topological insulation in bismuthene, extremely high electron mobilities in phosphorene and silicone, and substantial Li-ion storage capability in borophene. Isolation of these materials within the postgraphene era began with silicene in 2010 and quickly progressed to the experimental identification or theoretical prediction of 15 of the 18 main group elements existing as solids at standard pressure and temperatures. This review first focuses on the significance of defects/functionalization, discussion of different allotropes, and overarching structure-property relationships of 2D main group elemental materials. Then, a complete review of emerging applications in electronics, sensing, spintronics, plasmonics, photodetectors, ultrafast lasers, batteries, supercapacitors, and thermoelectrics is presented by application type, including detailed descriptions of how the material properties may be tailored toward each specific application.

4.
J Phys Chem C Nanomater Interfaces ; 123(41): 25501-25508, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31681455

RESUMO

The growing interest in plasmonic nanoparticles and their increasingly diverse applications is fuelled by the ability to tune properties via shape control, promoting intense experimental and theoretical research. Such shapes are dominated by geometries that can be described by the kinetic Wulff construction such as octahedra, thin triangular platelets, bipyramids, and decahedra, to name a few. Shape is critical in dictating the optical properties of these nanoparticles, in particular their localized surface plasmon resonance behavior, which can be modeled numerically. One challenge of the various available computational techniques is the representation of the nanoparticle shape. Specifically, in the discrete dipole approximation, a particle is represented by discretizing space via an array of uniformly distributed points-dipoles; this can be difficult to construct for complex shapes including those with multiple crystallographic facets, twins, and core-shell particles. Here, we describe a standalone user-friendly graphical user interface (GUI) that uses both kinetic and thermodynamic Wulff constructions to generate a dipole array for complex shapes, as well as the necessary input files for DDSCAT-based numerical approaches. Examples of the use of this GUI are described through three case studies spanning different shapes, compositions, and shell thicknesses. Key advances offered by this approach, in addition to simplicity, are the ability to create crystallographically correct structures and the addition of a conformal shell on complex shapes.

5.
ACS Appl Mater Interfaces ; 11(36): 33442-33451, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31411450

RESUMO

Supported lipid bilayers are essential model systems for studying biological membranes and for membrane-based sensor development. Surface-enhanced Raman spectroscopy (SERS) stands to add considerably to our understanding of the dynamics and interactions of these systems through direct chemical information. Despite this potential, SERS of lipid bilayers is not routinely achieved. Here, we carried out the first measurements of a solid-supported lipid bilayer on a SERS-active substrate and characterized the bilayer using SERS, atomic force microscopy, surface plasmon resonance spectroscopy, ellipsometry, and fluorescence recovery after photobleaching (FRAP). The creation of a fluid, SERS-active supported lipid bilayer was accomplished through use of a novel silica-coated silver film-over-nanosphere substrate. These substrates offer a powerful new platform to couple common surface techniques that are challenging on the nanoscale, for example, ellipsometry and FRAP, with SERS for studying biological membranes and their dynamics.

6.
ACS Appl Mater Interfaces ; 11(13): 12777-12785, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30854848

RESUMO

Metal-semiconductor contact has been a critical topic in the semiconductor industry because it influences device performance remarkably. Conventional metals have served as the major contact material in electronic and optoelectronic devices, but such a selection becomes increasingly inadequate for emerging novel materials such as two-dimensional (2D) materials. Deposited metals on semiconducting 2D channels usually form large resistance contacts due to the high Schottky barrier. A few approaches have been reported to reduce the contact resistance but they are not suitable for large-scale application or they cannot create a clean and sharp interface. In this study, a chemical vapor deposition (CVD) technique is introduced to produce large-area semiconducting 2D material (2H MoTe2) planarly contacted by its metallic phase (1T' MoTe2). We demonstrate the phase-controllable synthesis and systematic characterization of large-area MoTe2 films, including pure 2H phase or 1T' phase, and 2H/1T' in-plane heterostructure. Theoretical simulation shows a lower Schottky barrier in 2H/1T' junction than in Ti/2H contact, which is confirmed by electrical measurement. This one-step CVD method to synthesize large-area, seamless-bonding 2D lateral metal-semiconductor junction can improve the performance of 2D electronic and optoelectronic devices, paving the way for large-scale 2D integrated circuits.

7.
J Chem Phys ; 151(24): 244708, 2019 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-31893891

RESUMO

Plasmonic structures have attracted much interest in science and engineering disciplines, exploring a myriad of potential applications owing to their strong light-matter interactions. Recently, the plasmonic concentration of energy in subwavelength volumes has been used to initiate chemical reactions, for instance by combining plasmonic materials with catalytic metals. In this work, we demonstrate that plasmonic nanoparticles of earth-abundant Mg can undergo galvanic replacement in a nonaqueous solvent to produce decorated structures. This method yields bimetallic architectures where partially oxidized 200-300 nm Mg nanoplates and nanorods support many smaller Au, Ag, Pd, or Fe nanoparticles, with potential for a stepwise process introducing multiple decoration compositions on a single Mg particle. We investigated this mechanism by electron-beam imaging and local composition mapping with energy-dispersive X-ray spectroscopy as well as, at the ensemble level, by inductively coupled plasma mass spectrometry. High-resolution scanning transmission electron microscopy further supported the bimetallic nature of the particles and provided details of the interface geometry, which includes a Mg oxide separation layer between Mg and the other metal. Depending on the composition of the metallic decorations, strong plasmonic optical signals characteristic of plasmon resonances were observed in the bulk with ultraviolet-visible spectrometry and at the single particle level with darkfield scattering. These novel bimetallic and multimetallic designs open up an exciting array of applications where one or multiple plasmonic structures could interact in the near-field of earth-abundant Mg and couple with catalytic nanoparticles for applications in sensing and plasmon-assisted catalysis.

8.
ACS Appl Mater Interfaces ; 10(47): 40773-40780, 2018 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-30387342

RESUMO

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are a unique class of 2D materials possessing unique optoelectronic properties when exfoliated into mono- and few-layer sheets. Recently, electroablation (EA) has become of interest as a promising synthesis method for single-layer sheets of TMDs. Here, we introduce spectroelectrochemical micro-extinction spectroscopy (SE-MExS) as a high-throughput technique to study electrochemical thinning of TMDs as it occurs. This approach enables the parallel use of spectroscopy and imaging to nondestructively characterize 2D materials in situ. We unravel optoelectronics of the TMDs by observing changes in optical properties during EA. We find that the EA process for MoS2, WS2, MoSe2, and WSe2 occurs edge first, generating high density of edge sites. Our results show that stable monolayers of MoS2, WS2, and MoSe2 can be synthesized from bulk precursors by the EA process, while conversely, no WSe2 remains postablation.

9.
Nano Lett ; 18(6): 3752-3758, 2018 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-29771126

RESUMO

Nanoparticles of some metals (Cu/Ag/Au) sustain oscillations of their electron cloud called localized surface plasmon resonances (LSPRs). These resonances can occur at optical frequencies and be driven by light, generating enhanced electric fields and spectacular photon scattering. However, current plasmonic metals are rare, expensive, and have a limited resonant frequency range. Recently, much attention has been focused on earth-abundant Al, but Al nanoparticles cannot resonate in the IR. The earth-abundant Mg nanoparticles reported here surmount this limitation. A colloidal synthesis forms hexagonal nanoplates, reflecting Mg's simple hexagonal lattice. The NPs form a thin self-limiting oxide layer that renders them stable suspended in 2-propanol solution for months and dry in air for at least two week. They sustain LSPRs observable in the far-field by optical scattering spectroscopy. Electron energy loss spectroscopy experiments and simulations reveal multiple size-dependent resonances with energies across the UV, visible, and IR. The symmetry of the modes and their interaction with the underlying substrate are studied using numerical methods. Colloidally synthesized Mg thus offers a route to inexpensive, stable nanoparticles with novel shapes and resonances spanning the entire UV-vis-NIR spectrum, making them a flexible addition to the nanoplasmonics toolbox.

10.
Nanoscale ; 10(9): 4267-4275, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29436546

RESUMO

Depending on the experimental conditions and plasmonic systems, the correlations between near-field surface enhanced Raman scattering (SERS) behaviors and far-field localized surface plasmon resonance (LSPR) responses have sometimes been accepted directly or argued or explored. In this work, we focus on the attractive subwavelength closely spaced metallic nanorod arrays and investigate in detail the complex relationship between their SERS behaviors and plasmon resonances. This is achieved utilizing a combination of array fabrication, conventional LSPR spectra, SERS measurements, electron microscopy and numerical modeling. Three key factors that may impact the correlations have been comprehensively analyzed: the intrinsic near-field to far-field red-shift is found to be rather small in the lattice; the surface roughness has actually little impact on the spectral alignment of the near- and far-field responses; the continuous dependence of individual SERS peak heights on the Stokes Raman shift has been visualized and further clarified. By 3D finite element method (FEM) plasmon mapping, the physical origin of the collective resonances in the lattice is verified directly to be the Fabry-Perot-like cavity mode. The strong near-field enhancement results from the coupling of surface plasmon polaritons (SPPs) propagating at the two sidewalls of neighbouring nanorods forming the resonant cavity. The physical principles demonstrated here benefit significantly the optimization of nano-optic devices based on closely spaced metallic nanorod arrays, as well as the fundamental understanding of the near- and far-field relationship.

11.
ACS Appl Mater Interfaces ; 9(43): 37597-37605, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28990755

RESUMO

Controlling the size, number, and shape of nanogaps in plasmonic nanostructures is of significant importance for the development of novel quantum plasmonic devices and quantitative sensing techniques such as surface-enhanced Raman scattering (SERS). Here, we introduce a new synthetic method based on coordination interactions and galvanic replacement to prepare core-shell plasmonic nanorods with tunable enclosed nanogaps. Decorating Au nanorods with Raman reporters that strongly coordinate Ag+ ions (e.g., 4-mercaptopyridine) afforded uniform nucleation sites to form a sacrificial Ag shell. Galvanic replacement of the Ag shell by HAuCl4 resulted in Au-AgAu core-shell structure with a uniform intra-nanoparticle gap. The size (length and width) and morphology of the core-shell plasmonic nanorods as well as the nanogap size depend on the concentration of the coordination complexes formed between Ag+ ions and 4-mercaptopyridine. Moreover, encapsulating Raman reporters within the nanogaps afforded an internal standard for sensitive and quantitative SERS analysis. To test the applicability, core-shell plasmonic nanorods were functionalized with aptamers specific to circulating tumor cells such as MCF-7 (Michigan Cancer Foundation-7, breast cancer cell line). This system could selectively detect as low as 20 MCF-7 cells in a blood mimicking fluid employing SERS. The linking DNA duplex on core-shell plasmonic nanorods can also intercalate hydrophobic drug molecules such as Doxorubicin, thereby increasing the versatility of this sensing platform to include drug delivery. Our synthetic method offers the possibility of developing multifunctional SERS-active materials with a wide range of applications including biosensing, imaging, and therapy.


Assuntos
Células Neoplásicas Circulantes , Ouro , Humanos , Nanopartículas Metálicas , Nanoestruturas , Nanotubos , Prata
12.
ACS Nano ; 11(10): 10281-10288, 2017 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-28945360

RESUMO

Recently, aluminum has been established as an earth-abundant alternative to gold and silver for plasmonic applications. Particularly, aluminum nanocrystals have shown to be promising plasmonic photocatalysts, especially when coupled with catalytic metals or oxides into "antenna-reactor" heterostructures. Here, a simple polyol synthesis is presented as a flexible route to produce aluminum nanocrystals decorated with eight varieties of size-tunable transition-metal nanoparticle islands, many of which have precedence as heterogeneous catalysts. High-resolution and three-dimensional structural analysis using scanning transmission electron microscopy and electron tomography shows that abundant nanoparticle island decoration in the catalytically relevant few-nanometer size range can be achieved, with many islands spaced closely to their neighbors. When coupled with the Al nanocrystal plasmonic antenna, these small decorating islands will experience increased light absorption and strong hot-spot generation. This combination makes transition-metal decorated aluminum nanocrystals a promising material platform to develop plasmonic photocatalysis, surface-enhanced spectroscopies, and quantum plasmonics.

13.
ACS Nano ; 11(7): 6930-6941, 2017 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-28656759

RESUMO

The cathodic oxygen reduction reaction (ORR) is essential in the electrochemical energy conversion of fuel cells. Here, through the NH3 atmosphere annealing of a graphene oxide (GO) precursor containing trace amounts of Ru, we have synthesized atomically dispersed Ru on nitrogen-doped graphene that performs as an electrocatalyst for the ORR in acidic medium. The Ru/nitrogen-doped GO catalyst exhibits excellent four-electron ORR activity, offering onset and half-wave potentials of 0.89 and 0.75 V, respectively, vs a reversible hydrogen electrode (RHE) in 0.1 M HClO4, together with better durability and tolerance toward methanol and carbon monoxide poisoning than seen in commercial Pt/C catalysts. X-ray adsorption fine structure analysis and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy are performed and indicate that the chemical structure of Ru is predominantly composed of isolated Ru atoms coordinated with nitrogen atoms on the graphene substrate. Furthermore, a density function theory study of the ORR mechanism suggests that a Ru-oxo-N4 structure appears to be responsible for the ORR catalytic activity in the acidic medium. These findings provide a route for the design of efficient ORR single-atom catalysts.

14.
Nano Lett ; 17(4): 2611-2620, 2017 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-28337921

RESUMO

Doped metal oxides are plasmonic materials that boast both synthetic and postsynthetic spectral tunability. They have already enabled promising smart window and optoelectronic technologies and have been proposed for use in surface enhanced infrared absorption spectroscopy (SEIRA) and sensing applications. Herein, we report the first step toward realization of the former utilizing cubic F and Sn codoped In2O3 nanocrystals (NCs) to couple to the C-H vibration of surface-bound oleate ligands. Electron energy loss spectroscopy is used to map the strong near-field enhancement around these NCs that enables localized surface plasmon resonance (LSPR) coupling between adjacent nanocrystals and LSPR-molecular vibration coupling. Fourier transform infrared spectroscopy measurements and finite element simulations are applied to observe and explain the nature of the coupling phenomena, specifically addressing coupling in mesoscale assembled films. The Fano line shape signatures of LSPR-coupled molecular vibrations are rationalized with two-port temporal coupled mode theory. With this combined theoretical and experimental approach, we describe the influence of coupling strength and relative detuning between the molecular vibration and LSPR on the enhancement factor and further explain the basis of the observed Fano line shape by deconvoluting the combined response of the LSPR and molecular vibration in transmission, absorption and reflection. This study therefore illustrates various factors involved in determining the LSPR-LSPR and LSPR-molecular vibration coupling for metal oxide materials and provides a fundamental basis for the design of sensing or SEIRA substrates.

15.
J Phys Chem Lett ; 8(1): 299-306, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-27982600

RESUMO

Interactions between fluorophores and plasmonic nanoparticles modify the fluorescence intensity, shape, and position of the observed emission pattern, thus inhibiting efforts to optically super-resolve plasmonic nanoparticles. Herein, we investigate the accuracy of localizing dye fluorescence as a function of the spectral and spatial separations between fluorophores (Alexa 647) and gold nanorods (NRs). The distance at which Alexa 647 interacts with NRs is varied by layer-by-layer polyelectrolyte deposition while the spectral separation is tuned by using NRs with varying localized surface plasmon resonance (LSPR) maxima. For resonantly coupled Alexa 647 and NRs, emission to the far field through the NR plasmon is highly prominent, resulting in underestimation of NR sizes. However, we demonstrate that it is possible to improve the accuracy of the emission localization when both the spectral and spatial separations between Alexa 647 and the LSPR are optimized.

16.
J Phys Chem C Nanomater Interfaces ; 120(37): 20843-20851, 2016 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-27688821

RESUMO

Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3-6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of the Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way toward comprehensive nanoengineering of multifunctional bimetallic nanostructures, with potential applications in plasmon-enhanced catalysis and in situ monitoring of chemical processes via surface-enhanced spectroscopy.

17.
Nano Lett ; 16(11): 6939-6945, 2016 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-27704845

RESUMO

The internal structure of hollow AgAu nanorods created by partial galvanic replacement was manipulated reversibly, and its effect on optical properties was mapped with nanometer resolution. Using the electron beam in a scanning transmission electron microscope to create solvated electrons and reactive radicals in an encapsulated solution-filled cavity in the nanorods, Ag ions were reduced nearby the electron beam, reshaping the core of the nanoparticles without affecting the external shape. The changes in plasmon-induced near-field properties were then mapped with electron energy-loss spectroscopy without disturbing the internal structure, and the results are supported by finite-difference time-domain calculations. This reversible shape and near-field control in a hollow nanoparticle actuated by an external stimulus introduces possibilities for applications in reprogrammable sensors, responsive materials, and optical memory units. Moreover, the liquid-filled nanorod cavity offers new opportunities for in situ microscopy of chemical reactions.

18.
Anal Chem ; 88(16): 7968-74, 2016 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-27436204

RESUMO

Lipid membranes and membrane proteins are important biosensing targets, motivating the development of label-free methods with improved sensitivity. Silica-coated metal nanoparticles allow these systems to be combined with supported lipid bilayers for sensing membrane proteins through localized surface plasmon resonance (LSPR). However, the small sensing volume of LSPR makes the thickness of the silica layer critical for performance. Here, we develop a simple, inexpensive, and rapid sol-gel method for preparing thin conformal, continuous silica films and demonstrate its applicability using gold nanodisk arrays with LSPRs in the near-infrared range. Silica layers as thin as ∼5 nm are observed using cross-sectional scanning transmission electron microscopy. The loss in sensitivity due to the thin silica coating was found to be only 16%, and the biosensing capabilities of the substrates were assessed through the binding of cholera toxin B to GM1 lipids. This sensor platform should prove useful in the rapid, multiplexed detection and screening of membrane-associated biological targets.


Assuntos
Técnicas Biossensoriais , Toxina da Cólera/análise , Gangliosídeo G(M1)/química , Bicamadas Lipídicas/química , Ressonância de Plasmônio de Superfície , Membrana Celular/química , Ouro/química , Nanopartículas Metálicas/química , Microscopia Eletrônica de Transmissão , Dióxido de Silício/química
19.
Proc Natl Acad Sci U S A ; 113(32): 8916-20, 2016 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-27444015

RESUMO

Metallic nanoparticles with strong optically resonant properties behave as nanoscale optical antennas, and have recently shown extraordinary promise as light-driven catalysts. Traditionally, however, heterogeneous catalysis has relied upon weakly light-absorbing metals such as Pd, Pt, Ru, or Rh to lower the activation energy for chemical reactions. Here we show that coupling a plasmonic nanoantenna directly to catalytic nanoparticles enables the light-induced generation of hot carriers within the catalyst nanoparticles, transforming the entire complex into an efficient light-controlled reactive catalyst. In Pd-decorated Al nanocrystals, photocatalytic hydrogen desorption closely follows the antenna-induced local absorption cross-section of the Pd islands, and a supralinear power dependence strongly suggests that hot-carrier-induced desorption occurs at the Pd island surface. When acetylene is present along with hydrogen, the selectivity for photocatalytic ethylene production relative to ethane is strongly enhanced, approaching 40:1. These observations indicate that antenna-reactor complexes may greatly expand possibilities for developing designer photocatalytic substrates.

20.
Sci Rep ; 6: 23159, 2016 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-26983501

RESUMO

Considering the nanogap and lattice effects, there is an attractive structure in plasmonics: closely spaced metallic nanoarrays. In this work, we demonstrate experimentally and theoretically the lattice coupling of multipole plasmon modes for closely spaced gold nanorod arrays, offering a new insight into the higher order cavity modes coupled with each other in the lattice. The resonances can be greatly tuned by changes in inter-rod gaps and nanorod heights while the influence of the nanorod diameter is relatively insignificant. Experimentally, pronounced suppressions of the reflectance are observed. Meanwhile, the near-field enhancement can be further enhanced, as demonstrated through surface enhanced Raman scattering (SERS). We then confirm the correlation between the near-field and far-field plasmonic responses, which is significantly important for maximizing the near-field enhancement at a specific excitation wavelength. This lattice coupling of multipole plasmon modes is of broad interest not only for SERS but also for other plasmonic applications, such as subwavelength imaging or metamaterials.

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