The Experts below are selected from a list of 2208 Experts worldwide ranked by ideXlab platform
Richard P Van Duyne - One of the best experts on this subject based on the ideXlab platform.
-
plasmonic properties of film over nanowell surfaces fabricated by Nanosphere Lithography
Journal of Physical Chemistry B, 2005Co-Authors: Erin M Hicks, Kenneth G Spears, George C Schatz, Xiaoyu Zhang, Olga Lyandres, Richard P Van DuyneAbstract:In this work, a detailed and systematic study of the plasmonic properties of a novel film over nanowell surface is investigated. These nanostructures are fabricated using Nanosphere Lithography and reactive ion etching and structurally characterized by AFM and SEM. The resulting structures show remarkably narrow plasmon bands in reflectance spectra (as little as 0.10 eV) and greater sensitivity to external dielectric environment than has been seen in other nanoparticle systems, resulting in an improvement in the figure of merit (FOM = refractive index sensitivity (eV·RIU-1)/full width at half-maximum (eV)) for refractive index sensing. Theoretical modeling for the plasmon spectra of these nanostructures is done using discrete dipole approximation code under periodic boundary conditions. The modeling results match the measurements accurately in aspects of the variation of the plasmon line shape with altering internanowell distance and dielectric environment.
-
electrochemical tuning of silver nanoparticles fabricated by Nanosphere Lithography
Nano Letters, 2005Co-Authors: Xiaoyu Zhang, Erin M Hicks, George C Schatz, J Zhao, Richard P Van DuyneAbstract:An electrochemical method is developed to quantitatively modify and spectroscopically monitor the size and shape of Ag nanotriangles fabricated by Nanosphere Lithography (NSL) on an indium tin oxide (ITO) electrode surface. AFM and SEM results demonstrate that the preferential order of electrochemical oxidation for a nanotriangle is, surprisingly, bottom edges first, then triangular tips, then out-of-plane height.
-
sub 100 nm triangular nanopores fabricated with the reactive ion etching variant of Nanosphere Lithography and angle resolved Nanosphere Lithography
Nano Letters, 2004Co-Authors: Alyson V Whitney, Benjamin D Myers, Richard P Van DuyneAbstract:Nanosphere Lithography (NSL) is combined with reactive ion etching (RIE) to fabricate ordered arrays of in-plane, triangular cross-section nanopores. Nanopores with in-plane widths ranging from 44 to 404 nm and depths ranging from 25 to 250 nm are demonstrated. The combination of angle-resolved Nanosphere Lithography (AR NSL) and RIE yields an additional three-fold reduction in nanopore size.
-
a highly sensitive and selective surface enhanced nanobiosensor
MRS Proceedings, 2002Co-Authors: Amanda J Haes, Richard P Van DuyneAbstract:Nanosphere Lithography (NSL) derived triangular Ag nanoparticles were used to create an extremely sensitive and specific optical biological and chemical nanosensor. Using simple UV-vis spectroscopy, biotinylated surface-confined Ag nanoparticles were used to detect streptavidin down to one picomolar concentrations. The system was tested for nonspecific binding interactions with bovine serum albumin and was found to display virtually no adverse results. The extremely sensitive and selective response of the Ag nanoparticle sensor indicates an exciting use for biological and chemical sensing.
-
angle resolved Nanosphere Lithography manipulation of nanoparticle size shape and interparticle spacing
Journal of Physical Chemistry B, 2002Co-Authors: Christy L Haynes, John C Hulteen, Matthew T Smith, Adam D Mcfarland, Richard P Van DuyneAbstract:This work presents a novel approach to fine-tuning the size, shape, and interparticle spacing of nanoparticles fabricated by Nanosphere Lithography (NSL). This approach, termed angle-resolved Nanosphere Lithography (AR NSL), is a variant of NSL that yields vastly different, and increasingly flexible, nanostructures. This is accomplished by controlling the angle, θ, between the surface normal of the sample assembly and the propagation vector of the material deposition beam. Comparison of experimental results to simulated nanoparticle array geometries generated using an analytical model show excellent qualitative agreement. Using AR NSL, we have demonstrated that it is possible to reduce in-plane nanoparticle dimensions by a factor of 4. This important result shows that it will be possible to achieve fabrication of nanoparticles with precision control of their dimensions in a size regime comparable with the industry standard electron beam Lithography. AR NSL provides a massively parallel, rather than serial...
Richard P Van Duyne - One of the best experts on this subject based on the ideXlab platform.
-
second harmonic excitation spectroscopy of silver nanoparticle arrays
Journal of Physical Chemistry B, 2005Co-Authors: Andrew M Moran, Jiha Sung, Erin M Hicks, Richard P Van Duyne, Kenneth G SpearsAbstract:Frequency-scanned excitation profiles of coherent second harmonic generation (SHG) were measured for silver nanoparticle arrays prepared by Nanosphere Lithography. The frequency of the fundamental beam did not coincide with the localized surface plasmon resonance (LSPR) of the nanoparticles and was tuned so that the coherent second harmonic (SH) emission was in the region of the LSPR at 720−750 nm. The SH emission from the arrays was compared with a smooth silver film to identify an enhancement of SH emission efficiency that peaks near ∼650 nm for nanoparticles 50 nm in height. The polarization and orientation dependence of this enhancement suggests that it is related to a dipolar LSPR mode polarized normal to the plane of the substrate. Linear extinction spectra are dominated by in-plane dipoles and do not show this weak out-of-plane LSPR mode. The nanoparticle arrays are truncated tetrahedrons symmetrically oriented by Nanosphere Lithography to cancel SH from in-plane dipoles which allows observation of...
-
Nanosphere Lithography tunable localized surface plasmon resonance spectra of silver nanoparticles
Journal of Physical Chemistry B, 2000Co-Authors: Traci R Jensen, Christy L Haynes, Michelle Duval Malinsky, Richard P Van DuyneAbstract:The wavelength corresponding to the extinction maximum, λmax, of the localized surface plasmon resonance (LSPR) of silver nanoparticle arrays fabricated by Nanosphere Lithography (NSL) can be systematically tuned from ∼400 nm to 6000 nm. Such spectral manipulation was achieved by using (1) precise lithographic control of nanoparticle size, height, and shape, and (2) dielectric encapsulation of the nanoparticles in SiOx. These results demonstrate an unprecedented level of wavelength agility in nanoparticle optical response throughout the visible, near-infrared, and mid-infrared regions of the electromagnetic spectrum. It will also be shown that this level of wavelength tunability is accompanied with the preservation of narrow LSPR bandwidths (fwhm), Γ. Additionally, two other surprising LSPR optical properties were discovered: (1) the extinction maximum shifts by 2−6 nm per 1 nm variation in nanoparticle width or height, and (2) the LSPR oscillator strength is equivalent to that of atomic silver in gas or...
-
Nanosphere Lithography effect of the external dielectric medium on the surface plasmon resonance spectrum of a periodic array of silver nanoparticles
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, Michelle L Duval, Lance K Kelly, Anne A Lazarides, George C Schatz, Richard P Van DuyneAbstract:In this paper we examine the effect of solvent on the optical extinction spectrum of periodic arrays of surface-confined silver nanoparticles fabricated by Nanosphere Lithography (NSL). By use of NSL, it is possible to systematically vary the out-of-plane height of the nanoparticles, and by thermal annealing, we can control the nanoparticle shape. We have studied four separate samples of nanoparticle arrays; three samples have nanoparticles that are truncated tetrahedral in shape but that differ in out-of-plane height and one sample has nanoparticles that are oblate ellipsoidal in shape. By performing UV−vis extinction spectroscopy measurements at 12 μm spatial resolution, we show that the defect sites that occur as a byproduct of the NSL fabrication process play a negligible role in the macroscale extinction spectrum. We find that the extinction spectrum of the nanoparticles that are oblate ellipsoidal in shape is least sensitive to the surrounding dielectric medium, and the extinction spectrum of the na...
-
Nanosphere Lithography surface plasmon resonance spectrum of a periodic array of silver nanoparticles by ultraviolet visible extinction spectroscopy and electrodynamic modeling
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, George C Schatz, Richard P Van DuyneAbstract:In this paper we measure the optical extinction spectrum of a periodic array of silver nanoparticles fabricated by Nanosphere Lithography (NSL) and present detailed comparisons of the results with predictions of electrodynamic theory. The silver nanoparticles are small (∼100 nm) compared to the wavelength of light but too large to have their optical properties described adequately with a simple electrostatic model. We make use of the discrete dipole approximation (DDA), which is a coupled finite element method. With the DDA one can calculate the extinction of light as a function of wavelength for particles of arbitrary size and shape. We show that NSL-fabricated Ag nanoparticles can be modeled without adjustable parameters as truncated tetrahedrons, taking their size and shape parameters directly from atomic force microscopy (AFM) measurements and using literature values of the bulk dielectric constants of silver. These AFM measurements are presented as part of this paper, and the resulting theoretical li...
A Cusano - One of the best experts on this subject based on the ideXlab platform.
-
Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes
MDPI AG, 2018Co-Authors: Giuseppe Quero, Marco Pisco, Francesco Galeotti, Gianluigi Zito, Stefano Managò, Anna Chiara De Luca, A CusanoAbstract:In this paper we report on the engineering of repeatable surface enhanced Raman scattering (SERS) optical fiber sensor devices (optrodes), as realized through Nanosphere Lithography. The Lab-on-Fiber SERS optrode consists of polystyrene Nanospheres in a close-packed arrays configuration covered by a thin film of gold on the optical fiber tip. The SERS surfaces were fabricated by using a Nanosphere Lithography approach that is already demonstrated as able to produce highly repeatable patterns on the fiber tip. In order to engineer and optimize the SERS probes, we first evaluated and compared the SERS performances in terms of Enhancement Factor (EF) pertaining to different patterns with different Nanosphere diameters and gold thicknesses. To this aim, the EF of SERS surfaces with a pitch of 500, 750 and 1000 nm, and gold films of 20, 30 and 40 nm have been retrieved, adopting the SERS signal of a monolayer of biphenyl-4-thiol (BPT) as a reliable benchmark. The analysis allowed us to identify of the most promising SERS platform: for the samples with Nanospheres diameter of 500 nm and gold thickness of 30 nm, we measured values of EF of 4 × 105, which is comparable with state-of-the-art SERS EF achievable with highly performing colloidal gold nanoparticles. The reproducibility of the SERS enhancement was thoroughly evaluated. In particular, the SERS intensity revealed intra-sample (i.e., between different spatial regions of a selected substrate) and inter-sample (i.e., between regions of different substrates) repeatability, with a relative standard deviation lower than 9 and 15%, respectively. Finally, in order to determine the most suitable optical fiber probe, in terms of excitation/collection efficiency and Raman background, we selected several commercially available optical fibers and tested them with a BPT solution used as benchmark. A fiber probe with a pure silica core of 200 µm diameter and high numerical aperture (i.e., 0.5) was found to be the most promising fiber platform, providing the best trade-off between high excitation/collection efficiency and low background. This work, thus, poses the basis for realizing reproducible and engineered Lab-on-Fiber SERS optrodes for in-situ trace detection directed toward highly advanced in vivo sensing
-
Nanosphere Lithography for optical fiber tip nanoprobes
Light-Science & Applications, 2017Co-Authors: Marco Pisco, Francesco Galeotti, G Quero, Giorgio Grisci, Alberto Micco, L V Mercaldo, Paola Delli Veneri, A Cutolo, A CusanoAbstract:A simple way is used to make nanopatterned tips for optical fibres by combining self-assembly of Nanospheres with nanofabrication processes. Nanostructures fabricated on optical fibre tips can be used to realize exceptional light trapping and manipulation on the nanoscale, which can be harnessed for sensing applications. The ability of Nanospheres to self-assemble into hexagonal arrays is promising for achieving such nanostructures. Marco Pisco at the University of Sannio in Italy and co-workers have demonstrated a new approach for realizing nanoprobes. They created a self-assembled hexagonal array of polystyrene Nanospheres on a water surface and then transferred it to an optical fibre tip. The team then modified the periodic structure by employing processes based on thermal evaporation, plasma etching and sonication. They demonstrated this method by using it to produce probes for surface-enhanced Raman spectroscopy.
-
Nanosphere Lithography for optical fiber tip nanoprobes
Light-Science & Applications, 2017Co-Authors: Marco Pisco, Francesco Galeotti, G Quero, Giorgio Grisci, Alberto Micco, L V Mercaldo, Paola Delli Veneri, A Cutolo, A CusanoAbstract:This paper reports a simple and economical method for the fabrication of nanopatterned optical fiber nanotips. The proposed patterning approach relies on the use of the Nanosphere Lithography of the optical fiber end facet. Polystyrene (PS) Nanospheres are initially self-assembled in a hexagonal array on the surface of water. The created pattern is then transferred onto an optical fiber tip (OFT). The PS monolayer colloidal crystal on the OFT is the basic building block that is used to obtain different periodic structures by applying further treatment to the fiber, such as metal coating, Nanosphere size reduction and sphere removal. Ordered dielectric and metallo-dielectric sphere arrays, metallic nanoisland arrays and hole-patterned metallic films with feature sizes down to the submicron scale are achievable using this approach. Furthermore, the sizes and shapes of these periodic structures can be tailored by altering the fabrication conditions. The results indicate that the proposed self-assembly approach is a valuable route for the development of highly repeatable metallo-dielectric periodic patterns on OFTs with a high degree of order and low fabrication cost. The method can be easily extended to simultaneously produce multiple fibers, opening a new route to the development of fiber-optic nanoprobes. Finally, we demonstrate the effective application of the patterned OFTs as surface-enhanced Raman spectroscopy nanoprobes.
George C Schatz - One of the best experts on this subject based on the ideXlab platform.
-
plasmonic properties of film over nanowell surfaces fabricated by Nanosphere Lithography
Journal of Physical Chemistry B, 2005Co-Authors: Erin M Hicks, Kenneth G Spears, George C Schatz, Xiaoyu Zhang, Olga Lyandres, Richard P Van DuyneAbstract:In this work, a detailed and systematic study of the plasmonic properties of a novel film over nanowell surface is investigated. These nanostructures are fabricated using Nanosphere Lithography and reactive ion etching and structurally characterized by AFM and SEM. The resulting structures show remarkably narrow plasmon bands in reflectance spectra (as little as 0.10 eV) and greater sensitivity to external dielectric environment than has been seen in other nanoparticle systems, resulting in an improvement in the figure of merit (FOM = refractive index sensitivity (eV·RIU-1)/full width at half-maximum (eV)) for refractive index sensing. Theoretical modeling for the plasmon spectra of these nanostructures is done using discrete dipole approximation code under periodic boundary conditions. The modeling results match the measurements accurately in aspects of the variation of the plasmon line shape with altering internanowell distance and dielectric environment.
-
electrochemical tuning of silver nanoparticles fabricated by Nanosphere Lithography
Nano Letters, 2005Co-Authors: Xiaoyu Zhang, Erin M Hicks, George C Schatz, J Zhao, Richard P Van DuyneAbstract:An electrochemical method is developed to quantitatively modify and spectroscopically monitor the size and shape of Ag nanotriangles fabricated by Nanosphere Lithography (NSL) on an indium tin oxide (ITO) electrode surface. AFM and SEM results demonstrate that the preferential order of electrochemical oxidation for a nanotriangle is, surprisingly, bottom edges first, then triangular tips, then out-of-plane height.
-
Nanosphere Lithography effect of substrate on the localized surface plasmon resonance spectrum of silver nanoparticles
Journal of Physical Chemistry B, 2001Co-Authors: Michelle Duval Malinsky, Lance K Kelly, George C Schatz, Richard P Van DuyneAbstract:In this paper, we explore the optical contributions of the substrate to the localized surface plasmon resonance (LSPR) spectrum of surface confined Ag nanoparticles produced by Nanosphere Lithography (NSL). We present optical extinction spectra of Ag nanoparticles fabricated on the following substrates: fused silica, borosilicate optical glass, mica, and SF-10a high refractive index specialty glass. For all the experiments discussed here, the Ag nanoparticles were approximately 100 nm in in-plane width and 25 nm in out-of-plane height. In a controlled N2 environment, the wavelength corresponding to the extinction maximum, λmax, shifts to the red with increasing refractive index of the substrate, nsubstrate. The sensitivity factor, Δλmax/Δnsubstrate, was measured to be 87 nm per refractive index unit (RIU). Experimental extinction spectra were modeled using the discrete dipole approximation (DDA). The DDA theory qualitatively predicts the experimentally observed trend that λmax is linearly dependent on ns...
-
Nanosphere Lithography effect of the external dielectric medium on the surface plasmon resonance spectrum of a periodic array of silver nanoparticles
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, Michelle L Duval, Lance K Kelly, Anne A Lazarides, George C Schatz, Richard P Van DuyneAbstract:In this paper we examine the effect of solvent on the optical extinction spectrum of periodic arrays of surface-confined silver nanoparticles fabricated by Nanosphere Lithography (NSL). By use of NSL, it is possible to systematically vary the out-of-plane height of the nanoparticles, and by thermal annealing, we can control the nanoparticle shape. We have studied four separate samples of nanoparticle arrays; three samples have nanoparticles that are truncated tetrahedral in shape but that differ in out-of-plane height and one sample has nanoparticles that are oblate ellipsoidal in shape. By performing UV−vis extinction spectroscopy measurements at 12 μm spatial resolution, we show that the defect sites that occur as a byproduct of the NSL fabrication process play a negligible role in the macroscale extinction spectrum. We find that the extinction spectrum of the nanoparticles that are oblate ellipsoidal in shape is least sensitive to the surrounding dielectric medium, and the extinction spectrum of the na...
-
Nanosphere Lithography surface plasmon resonance spectrum of a periodic array of silver nanoparticles by ultraviolet visible extinction spectroscopy and electrodynamic modeling
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, George C Schatz, Richard P Van DuyneAbstract:In this paper we measure the optical extinction spectrum of a periodic array of silver nanoparticles fabricated by Nanosphere Lithography (NSL) and present detailed comparisons of the results with predictions of electrodynamic theory. The silver nanoparticles are small (∼100 nm) compared to the wavelength of light but too large to have their optical properties described adequately with a simple electrostatic model. We make use of the discrete dipole approximation (DDA), which is a coupled finite element method. With the DDA one can calculate the extinction of light as a function of wavelength for particles of arbitrary size and shape. We show that NSL-fabricated Ag nanoparticles can be modeled without adjustable parameters as truncated tetrahedrons, taking their size and shape parameters directly from atomic force microscopy (AFM) measurements and using literature values of the bulk dielectric constants of silver. These AFM measurements are presented as part of this paper, and the resulting theoretical li...
Traci R Jensen - One of the best experts on this subject based on the ideXlab platform.
-
Nanosphere Lithography tunable localized surface plasmon resonance spectra of silver nanoparticles
Journal of Physical Chemistry B, 2000Co-Authors: Traci R Jensen, Christy L Haynes, Michelle Duval Malinsky, Richard P Van DuyneAbstract:The wavelength corresponding to the extinction maximum, λmax, of the localized surface plasmon resonance (LSPR) of silver nanoparticle arrays fabricated by Nanosphere Lithography (NSL) can be systematically tuned from ∼400 nm to 6000 nm. Such spectral manipulation was achieved by using (1) precise lithographic control of nanoparticle size, height, and shape, and (2) dielectric encapsulation of the nanoparticles in SiOx. These results demonstrate an unprecedented level of wavelength agility in nanoparticle optical response throughout the visible, near-infrared, and mid-infrared regions of the electromagnetic spectrum. It will also be shown that this level of wavelength tunability is accompanied with the preservation of narrow LSPR bandwidths (fwhm), Γ. Additionally, two other surprising LSPR optical properties were discovered: (1) the extinction maximum shifts by 2−6 nm per 1 nm variation in nanoparticle width or height, and (2) the LSPR oscillator strength is equivalent to that of atomic silver in gas or...
-
Nanosphere Lithography effect of the external dielectric medium on the surface plasmon resonance spectrum of a periodic array of silver nanoparticles
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, Michelle L Duval, Lance K Kelly, Anne A Lazarides, George C Schatz, Richard P Van DuyneAbstract:In this paper we examine the effect of solvent on the optical extinction spectrum of periodic arrays of surface-confined silver nanoparticles fabricated by Nanosphere Lithography (NSL). By use of NSL, it is possible to systematically vary the out-of-plane height of the nanoparticles, and by thermal annealing, we can control the nanoparticle shape. We have studied four separate samples of nanoparticle arrays; three samples have nanoparticles that are truncated tetrahedral in shape but that differ in out-of-plane height and one sample has nanoparticles that are oblate ellipsoidal in shape. By performing UV−vis extinction spectroscopy measurements at 12 μm spatial resolution, we show that the defect sites that occur as a byproduct of the NSL fabrication process play a negligible role in the macroscale extinction spectrum. We find that the extinction spectrum of the nanoparticles that are oblate ellipsoidal in shape is least sensitive to the surrounding dielectric medium, and the extinction spectrum of the na...
-
Nanosphere Lithography surface plasmon resonance spectrum of a periodic array of silver nanoparticles by ultraviolet visible extinction spectroscopy and electrodynamic modeling
Journal of Physical Chemistry B, 1999Co-Authors: Traci R Jensen, George C Schatz, Richard P Van DuyneAbstract:In this paper we measure the optical extinction spectrum of a periodic array of silver nanoparticles fabricated by Nanosphere Lithography (NSL) and present detailed comparisons of the results with predictions of electrodynamic theory. The silver nanoparticles are small (∼100 nm) compared to the wavelength of light but too large to have their optical properties described adequately with a simple electrostatic model. We make use of the discrete dipole approximation (DDA), which is a coupled finite element method. With the DDA one can calculate the extinction of light as a function of wavelength for particles of arbitrary size and shape. We show that NSL-fabricated Ag nanoparticles can be modeled without adjustable parameters as truncated tetrahedrons, taking their size and shape parameters directly from atomic force microscopy (AFM) measurements and using literature values of the bulk dielectric constants of silver. These AFM measurements are presented as part of this paper, and the resulting theoretical li...
