An antisymmetric plasmon resonance in coupled gold nanoparticles as a sensitive tool for detection of local index of refraction
TL;DR: In this paper, a nanofabricated regular array of coupled gold nano-pillars is employed to detect local indices of refraction of different liquids using a shift of an antisymmetric plasmon resonance peak observed in the reflection spectra.
Abstract: A nanofabricated regular array of coupled gold nano-pillars is employed to detect local indices of refraction of different liquids using a shift of an antisymmetric plasmon resonance peak observed in the reflection spectra. The peak spectral position is found to be a unique function of the local refractive index for a wide range of indices. We discuss possible applications of the fabricated nanostructured arrays in bio and chemical sensors.
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TL;DR: In this article, the first experimental realization of three-dimensional nanometric optical tweezers that are based on nanostructured substrates was reported, which achieved nanoscale control of entities at significantly smaller laser powers and open new avenues for nanomanipulation of fragile biological objects.
Abstract: The ability to control the position of a mesoscopic object with nanometric precision is important for the rapid progress of nanoscience. One of the most promising tools to achieve such control is optical tweezers, which trap objects near the focus of a laser beam. However, the drawbacks of conventional tweezers include a trapping volume that is diffraction-limited and significant brownian motion of trapped nanoobjects. Here, we report the first experimental realization of three-dimensional nanometric optical tweezers that are based on nanostructured substrates. Using electromagnetically coupled pairs of gold nanodots in a standard optical tweezers set-up, we create an array of subwavelength plasmonic optical traps that offer a significant increase in trapping efficiency. The nanodot optical near-fields reduce the trapping volume beyond the diffraction limit and quench brownian motion of the trapped nanoparticles by almost an order of magnitude as compared to conventional tweezers operating under the same trapping conditions. Our tweezers achieve nanoscale control of entities at significantly smaller laser powers and open new avenues for nanomanipulation of fragile biological objects.
634 citations
TL;DR: This study has engineered optical nanosensors by the combined approach of negative resist, electron beam lithography, and reactive ion etching to form highly reproducible arrays of gold dimers in which the near-field coupling in their subwavelength gap enables for scaling the sensing volume down to the single-protein scale.
Abstract: In this study, we report on ultrasensitive protein detection with lithographically prepared plasmonic nanostructures. We have engineered optical nanosensors by the combined approach of negative resist, electron beam lithography, and reactive ion etching to form highly reproducible arrays of gold dimers in which the near-field coupling in their subwavelength gap enables for scaling the sensing volume down to the single-protein scale. In good agreement with recent theoretical predictions, the dimer geometry offers enhanced sensitivity compared to isolated particles for the detection of both small organic molecules and proteins. Beyond, by exploiting size exclusion, we are capable of monitoring the number of proteins able to bind across the gap region through the precise engineering of the structures coupled to the selective binding of a surface-assembled monolayer and covalent attachment of the protein.
351 citations
TL;DR: The development of a nanoparticle-enhanced biosensor by integrating both the nanoparticles and immunoassay sensing technologies into a phase interrogation surface plasmon resonance (SPR) system for detecting antigen at a concentration as low as the femtomolar range is reported.
Abstract: In this study, we report the development of a nanoparticle-enhanced biosensor by integrating both the nanoparticles and immunoassay sensing technologies into a phase interrogation surface plasmon resonance (SPR) system for detecting antigen at a concentration as low as the femtomolar range. Our work has demonstrated that the plasmonic field extension generated from the gold film to gold nanorod (GNR) has led to a drastic sensitivity enhancement. Antibody-functionalized sensing film, together with antibody-conjugated GNRs, was readily served as a plasmonic coupling partner that can be used as a powerful ultrasensitive sandwich immunoassay for cancer-related disease detection. Experimentally, it was found that the bioconjugated GNR labels enhance the tumor necrosis factor alpha (TNF-α) antigen signal with more than 40-fold increase compared to the traditional SPR biosensing technique. The underlying principle was analyzed by simulating the near-field coupling between the sensing film and the GNR. The results have shown that GNRs were readily served as promising amplification labels in SPR sensing technology.
239 citations
TL;DR: This work presents what it believes to be the first experimental study of the optical response of collective plasmon resonances in regular arrays of nanoresonators to local environment and shows that the phase sensitivity of the collective resonances can be more than 2 orders of magnitude better than the best amplitude sensitivity ofthe same nanodot array.
Abstract: We present what we believe to be the first experimental study of the optical response of collective plasmon resonances in regular arrays of nanoresonators to local environment. Recently observed collective plasmon modes arise due to diffractive coupling of localized plasmons and yield almost 1 order of magnitude improvement in resonance quality. We measure the response of these modes to tiny variations of the refractive index of both gaseous and liquid media. We show that the phase sensitivity of the collective resonances can be more than 2 orders of magnitude better than the best amplitude sensitivity of the same nanodot array as well as 1 order of magnitude better than the phase sensitivity in surface plasmon resonance sensors.
156 citations
TL;DR: It is shown that aligned gold nanotube arrays capable of supporting plasmonic resonances can be used as high performance refractive index sensors in biomolecular binding reactions and have a signal-to-noise ratio better than 1000 upon protein binding.
Abstract: We show that aligned gold nanotube arrays capable of supporting plasmonic resonances can be used as high performance refractive index sensors in biomolecular binding reactions. A methodology to examine the sensing ability of the inside and outside walls of the nanotube structures is presented. The sensitivity of the plasmonic nanotubes is found to increase as the nanotube walls are exposed, and the sensing characteristic of the inside and outside walls is shown to be different. Finite element simulations showed good qualitative agreement with the observed behavior. Free standing gold nanotubes displayed bulk sensitivities in the region of 250 nm per refractive index unit and a signal-to-noise ratio better than 1000 upon protein binding which is highly competitive with state-of-the-art label-free sensors.
152 citations
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Book•
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01 Jan 1959
TL;DR: In this paper, the authors discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals, including interference, interferometers, and diffraction.
Abstract: The book is comprised of 15 chapters that discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals. The text covers the elements of the theories of interference, interferometers, and diffraction. The book tackles several behaviors of light, including its diffraction when exposed to ultrasonic waves.
19,815 citations