12 research outputs found
Resonant optical trapping of Janus nanoparticles in plasmonic nanoaperture
Controlled trapping of light absorbing nanoparticles with low-power optical
tweezers is crucial for remote manipulation of small objects. This study takes
advantage of the synergetic effects of tightly confined local fields of
plasmonic nanoaperture, self-induced back-action of nanoparticles, and resonant
optical trapping method to demonstrate enhanced manipulation of Janus
nanoparticles in metallic nanohole aperture. We theoretically demonstrate that
displacement of Au-coated Janus nanoparticles toward plasmonic nanoaperture and
proper orientation of the metal coating give rise to enhanced near-field
intensity and pronounced optical force. We also explore the effect of resonant
optical trapping by employing dual laser system, where an on-resonant green
laser excites the metal-coated nanoparticle whereas an off-resonant
near-infrared laser plays trapping role. It is found that, at optimum
nanoparticle configuration, the resonant optical trapping technique can result
in three-fold enhancement of optical force, which is attributed to excitation
of surface plasmon resonance in Janus nanoparticles. The findings of this study
might pave the way for low power optical manipulation of light-absorbing
nanoparticles with possible applications in nanorobotics and drug delivery
Photoinduced Temperature Gradients in Sub-wavelength Plasmonic Structures: The Thermoplasmonics of Nanocones
Plasmonic structures are renowned for their capability to efficiently convert
light into heat at the nanoscale. However, despite the possibility to generate
deep sub-wavelength electromagnetic hot spots, the formation of extremely
localized thermal hot spots is an open challenge of research, simply because of
the diffusive spread of heat along the whole metallic nanostructure. Here we
tackle this challenge by exploiting single gold nanocones. We theoretically
show how these structures can indeed realize extremely high temperature
gradients within the metal, leading to deep sub-wavelength thermal hot spots,
owing to their capability of concentrating light at the apex under resonant
conditions even under continuous wave illumination. A three-dimensional Finite
Element Method model is employed to study the electromagnetic field in the
structure and subsequent thermoplasmonic behaviour, in terms of the
three-dimensional temperature distribution. We show how the latter is affected
by nanocone size, shape, and composition of the surrounding environment.
Finally, we anticipate the use of photoinduced temperature gradients in
nanocones for applications in optofluidics and thermoelectrics or for thermally
induced nanofabrication
Hybrid plasmonic modes for enhanced refractive index sensing
Compared to single nanoparticles, strongly coupled plasmonic nanoparticles
provide attractive advantages owing to their ability to exhibit multiple
resonances with unique spectral features and higher local field intensity.
These enhanced plasmonic properties of coupled metal nanoparticles have been
used for various applications including realization of strong light-matter
interaction, photocatalysis, and sensing applications. In this article, we
review the basic physics of hybrid plasmonic modes in coupled metallic
nanodimers and assess their potentials for refractive index sensing. In
particular, we overview various modes of hybrid plasmons including bonding and
antibonding modes in symmetric nanodimers, Fano resonances in asymmetric
nanodimers, charge transfer plasmons in linked nanoparticle dimers, hybrid
plasmon modes in nanoshells, and gap modes in particle-on-mirror
configurations. Beyond the dimeric nanosystems, we also showcase the potentials
of hybrid plasmonic modes in periodic nanoparticle arrays for sensing
applications. Finally, based on the critical assessment of the recent
researches on coupled plasmonic modes, the outlook on the future prospects of
hybrid plasmon based refractometric sensing are discussed We believe that,
given their tunable resonances and ultranarrow spectral signatures, coupled
metal nanoparticles are expected to play key roles in developing precise
plasmonic nanodevices with extreme sensitivity
Nanoporous Metals: From Plasmonic Properties to Applications in Enhanced Spectroscopy and Photocatalysis
The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used nanoporous gold to mixed metal compounds, and discuss each of these plasmonic materials' suitability for a range of structural design and applications. Finally, we discuss the potentials and limitations of the traditional and alternative plasmonic materials for applications in enhanced spectroscopy and photocatalysis
Plasmomechanical Systems: Principles and Applications
AbstractExtreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip‐scale fabrication, and efficient actuation of mechanical systems at the nanoscale. Conversely, coupling mechanical oscillators to plasmonic nanostructures introduces mechanical degrees of freedom to otherwise static plasmonic structures thus giving rise to the generation of extremely large resonance shifts even for minor position changes. This nanoscale marriage of plasmonics and mechanics has led to the emergence of a new field of study called plasmomechanics that explores the fundamental principles underneath the coupling between light and plasmomechanical nanoresonators. In this review, both the fundamental concepts and applications of plasmomechanics as an emerging field of study are discussed. After an overview of the basic principles of plasmomechanics, the active tuning mechanisms of plasmonic nano‐mechanical systems are extensively analyzed. Moreover, the recent developments on the practical implications of plasmomechanic systems for such applications as biosensing and infrared detection are highlighted. Finally, an outlook on the implications of the plasmomechanical nanosystems for development of point‐of‐care diagnostic devices that can help early and rapid detection of fatal diseases are forwarded
Advances in ultrafast plasmonics
In the past twenty years, we have reached a broad understanding of many
light-driven phenomena in nanoscale systems. The temporal dynamics of the
excited states are instead quite challenging to explore, and, at the same time,
crucial to study for understanding the origin of fundamental physical and
chemical processes. In this review we examine the current state and prospects
of ultrafast phenomena driven by plasmons both from a fundamental and applied
point of view. This research area is referred to as ultrafast plasmonics and
represents an outstanding playground to tailor and control fast optical and
electronic processes at the nanoscale, such as ultrafast optical switching,
single photon emission and strong coupling interactions to tailor photochemical
reactions. Here, we provide an overview of the field, and describe the
methodologies to monitor and control nanoscale phenomena with plasmons at
ultrafast timescales in terms of both modeling and experimental
characterization. Various directions are showcased, among others recent
advances in ultrafast plasmon-driven chemistry and multi-functional plasmonics,
in which charge, spin, and lattice degrees of freedom are exploited to provide
active control of the optical and electronic properties of nanoscale materials.
As the focus shifts to the development of practical devices, such as
all-optical transistors, we also emphasize new materials and applications in
ultrafast plasmonics and highlight recent development in the relativistic
realm. The latter is a promising research field with potential applications in
fusion research or particle and light sources providing properties such as
attosecond duration
Multifunctional charge transfer plasmon resonance sensors
Charge transfer plasmon (CTP) modes arise when metallic nanoparticle dimers are connected by a conductive junction. This offers a unique opportunity to explore electron transport at optical frequencies as well as to attain narrow plasmon resonances that can be broadly modulated from visible to IR regimes, implying their potentials for applications in single-molecule electronics and sensing. This article showcases recent developments in theory and applications of charge transfer plasmon resonances (CTPRs) in various configurations of conductively linked plasmonic nanodimers. In particular, we give a due attention to exploiting ultratunable spectral features of charge transfer plasmon resonances for developing multifunctional plasmonic sensors for bulk, surface, gas and molecular sensing applications. We also discuss the implications of the charge and energy transfer between two plasmonic nanoparticles linked by sub-nanometer thick self-assembled monolayers for single-molecule conductance sensing and molecular electronics. In addition to the well-established plasmonic sensing schemes based on propagating and localized surface plasmon resonances, charge transfer plasmon resonance sensors may open up a new route in efforts to develop multifunctional sensing technologies
Resonant optical trapping of Janus nanoparticles in plasmonic nanoaperture
Controlled trapping of light absorbing nanoparticles with low-power optical tweezers is crucial for remote manipulation of small objects. This study takes advantage of the synergetic effects of tightly confined local fields of plasmonic nanoaperture, self-induced back-action of nanoparticles, and resonant optical trapping scheme to demonstrate enhanced manipulation of Janus nanoparticles in metallic nanohole aperture. We theoretically demonstrate that displacement of Au-coated Janus nanoparticles toward plasmonic nanoaperture and proper orientation of the metal coating give rise to enhanced near-field intensity and pronounced optical force. We also explore the effect of resonant optical trapping by employing two-laser system, where an on-resonant green laser excites the metal-coated nanoparticle whereas an off-resonant near-infrared laser plays trapping role. It is found that, at optimum nanoparticle configuration, the resonant optical trapping method can result in three-fold enhancement of optical force, which is attributed to excitation of surface plasmon resonance in Janus nanoparticles. These findings might have implications for efficient manipulation of light-absorbing nanoparticles of various compositions with low-power
Recent advances on plasmonic nanocavities for single-molecule spectroscopy
Plasmonic nanocavities are able to engineer and confine electromagnetic fields into subwavelength volumes. In the past decade, they have enabled a large set of applications, in particular for sensing, optical trapping, as well as the investigation of physical and chemical phenomena at a few or single-molecule levels. This extreme sensitivity is possible thanks to the highly confined local field intensity enhancement, which depends on the geometry of the plasmonic nanocavities. Indeed, properly designed structures providing engineered local optical fields lead to enhanced optical sensing based on different phenomena like surface enhanced Raman scattering, fluorescence, and Förster Resonant Energy Transfer. In this mini-review, we illustrate the most recent results on plasmonic nanocavities, with specific emphasis on the detection of single molecules