Arrays Of Noble Metal Nanoparticles Research Articles

Bionic 3D periodic nanostructures by Ag nano-islands deposited on cicada wings for rapid SERS detection

Recently, flexible and wearable sensors are extensively developed in advanced coating materials, especially in label-free and culture-free rapid detection. Surface-enhanced Raman scattering (SERS) detection is the one of the “fingerprinting” and rapid sensing technology, which combined with noble metal nanoparticle arrays and Raman spectroscopy. The bionic 3D regular structures can induce the multiple reflection of the laser in 3D structures to increase SERS intensity. In this study, we used the natural organism wings (cicada wings, CW) as the substrate. Homogenous nano-columnar structures with the size of 69–72 nm were observed on the CW by scanning electron microscope. Ag nano-island arrays were further deposited on the CW by thermal evaporation. The interparticle spacing of the Ag nano-columnar would decrease with increasing the deposited thickness, which could produce a very strong 3D hot-spots effect for enhancing Raman signals. The results show that the optimal SERS signals were found at 100 nm deposited thickness of Ag nano-islands on the CW nanostructure. The limit of detection (LOD) is lower than 10−9 M and the related standard deviation (RSD%) is about 13.7%, showing the high sensitivity and reproducibility of SERS signal for small molecules detection. Particularly, SERS intensity of CW-Ag-100 nm would increase ~1.7 times while bending inner angle achieves 15o, displaying its flexible characterization.

Anomalous Absorption in Arrays of Metallic Nanoparticles: A Powerful Tool for Quantum Dot Optoelectronics.

Periodic arrays of noble metal nanoparticles are emblematic nanostructures in photonics. Their ability to sustain localized surface plasmon resonances has been used throughout the years to demonstrate a variety of passive and active functionalities such as enhanced luminescence in dipolar media and LEDs as well as higher responsivities in photoconductive detectors. Here, we show that additional magnetic resonances, associated with inductive current loops between the nanoparticles and accessible with transverse electric waves, emerge in the limit of dense arrays with subwavelength periods. Moreover, their interplay with the plasmons of the system results in spectrally sharp analogues of electromagnetically induced absorption (EIA). We use these metasurfaces to induce changes and enhancements in the emission, absorption, photoconduction, and polarization properties of active layers of PbS nanocrystals, illustrating the potential of EIA beyond the passive functionalities demonstrated so far in literature.

Resonant Optical Phenomena in Heterogeneous Plasmon Nanostructures of Noble Metals: A Review

The interaction of electromagnetic radiation with ordered and disordered arrays of noble metal nanoparticles, leading to the excitation of various modes of surface plasmon states in them, is analyzed. The dipole localized surface plasmon resonance in isolated nanoparticles and the influence of various size effects on its optical response are considered. The effect of dipole-dipole interaction between gold and silver nanoparticles on the optical properties of various nanosized and nanostructured objects is discussed. It is shown that both localized and delocalized (propagated) surface plasmon modes can be excited in composite gold and silver nanosystems, in particular, in porous films. The prospects for the practical application of nanostructures with arrays of gold and silver nanoparticles in sensor technology, surface-enhanced Raman spectroscopy, and modern optoelectronics are examined.

Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting.

We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol–gel (IGSG) resist on glass using a two-layer polydimethylsiloxane (PDMS) stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures. The microstructural and mechanical characteristics that developed during the processes were discussed. The results are promising for low-cost mass fabrication of devices for several photonic applications.

Engineering of parallel plasmonic-photonic interactions for on-chip refractive index sensors.

Ultra-narrow linewidth in the extinction spectrum of noble metal nanoparticle arrays induced by the lattice plasmon resonances (LPRs) is of great significance for applications in plasmonic lasers and plasmonic sensors. However, the challenge of sustaining LPRs in an asymmetric environment greatly restricts their practical applications, especially for high-performance on-chip plasmonic sensors. Herein, we fully study the parallel plasmonic-photonic interactions in both the Au nanodisk arrays (NDAs) and the core/shell SiO2/Au nanocylinder arrays (NCAs). Different from the dipolar interactions in the conventionally studied orthogonal coupling, the horizontal propagating electric field introduces the out-of-plane "hot spots" and results in electric field delocalization. Through controlling the aspect ratio to manipulate the "hot spot" distributions of the localized surface plasmon resonances (LSPRs) in the NCAs, we demonstrate a high-performance refractive index sensor with a wide dynamic range of refractive indexes ranging from 1.0 to 1.5. Both high figure of merit (FOM) and high signal-to-noise ratio (SNR) can be maintained under these detectable refractive indices. Furthermore, the electromagnetic field distributions confirm that the high FOM in the wide dynamic range is attributed to the parallel coupling between the superstrate diffraction orders and the height-induced LSPR modes. Our study on the near-field "hot-spot" engineering and far-field parallel coupling paves the way towards improved understanding of the parallel LPRs and the design of high-performance on-chip refractive index sensors.

Two-Dimensional Arrays of Gold Nanoparticles for Plasmonic Nanosensor

Two dimensional (2D) arrays of noble metal nanoparticles are widely used in the sensing of nanoscale biological and chemical events. Research in this area has sparked considerable interest in many fields owing to the novel optical properties, e.g., the localized surface plasmon resonance, of these metallic nanoarrays. In this paper, we report successes in fabricating 2D arrays of gold nano-islands using nanosphere lithography. The reproducibility and the effectiveness of the nano-patterning method are tested by means of spin coating and capillary force deposition. We found that the capillary force deposition method was more effective for nanospheres with diameters greater than 600 nm, whereas the spin coating method works better for nanospheres with diameters less than 600 nm. The optimal deposition parameters for both methods were reported, showing about 80% reproducibility. In addition, we characterize gold nano-island arrays both geometrically with AFM as well as optically with UV-VIS spectrometry. The AFM images revealed that the obtained nano-arrays formed a hexagonal pattern of truncated tetrahedron nano-islands. The experimental and theoretical values of the geometric parameters were compared. The 2D gold nano-arrays showed strong LSPR in the absorption spectra. As the nano-islands increased in size, the LSPR absorption bands became red-shifted. Linear dependence of the plasmon absorption maximum on the size of the gold nano-islands was identified through the increment in the plasmon absorption maximum rate for a one nanometer increase in the characteristic length of the nano-islands. We found that the 2D gold nano-arrays showed nearly seven-fold higher sensitivity of the absorption spectrum to the size of the nano-islands as compared to colloidal gold nano-particles.

Synthesis and photocatalytic properties of hierarchical metal nanoparticles/ZnO thin films hetero nanostructures assisted by diblock copolymer inverse micellar nanotemplates

Metal dot-on-ZnO type hierarchical nanostructures composed of ordered arrays of noble metal nanoparticles with controlled areal density, prepared from poly(styrene- block-vinyl pyridine) diblock copolymer inverse micelles loaded with metal precursors, on sol–gel process based ∼48 nm thick ZnO thin films exhibit enhanced photocatalytic activities compared with pure ZnO thin films in terms of photodegradation of methylene blue.

A plasmonic biosensor array by block copolymer lithography

Highly uniform and dense, hexagonal noble metal nanoparticle arrays were achieved on large-area transparent glass substrates via scalable, parallel processing of block copolymer lithography. Exploring their localized surface plasmon resonance (LSPR) characteristics revealed that the Ag nanoparticle array displayed a UV-vis absorbance spectrum sufficiently narrow and intense for biosensing application. A highly-sensitive, label-free detection of prostate cancer specific antibody (anti-PSA) with sub-ng ml−1 level detection limit (0.1∼1 ng ml−1) has been accomplished with the plasmonic nanostructure. Our approach offers a valuable route to a low-cost, manufacture-scale production of plasmonic nanostructures, potentially useful for various photonic and optoelectronic devices.

Detection of biomolecules using optoelectronic biosensor based on localized surface plasmon resonance. Nanoimprint lithography approach

In this work, we use a nanoimprint lithography fabrication technology to create uniformly-oriented and homogenous noble metal nanoparticle arrays with well- controlled size, shape and spacing, which can be the basis platform for the development of Localized Surface Plasmon Resonance (LSPR) sensors for biomolecular detection. Using this approach, we demonstrate proof-of-principle of an optical biosensor to quantify biomolecular interactions in a real-time mode using a UV-visible spectrophotometer. The sensor shows concentration-dependent kinetics of surface adsorption or binding of biomolecules and a capability to monitor antigen-antibody specific reactions, which is demonstrated by the reaction between bovine serum albumin (BSA) and anti-BSA immunoglobulin.

Tunable, directional and wavelength selective plasmonic nanoantenna arrays

Linear arrays of noble metal nanoparticles, supporting Bragg plasmonic resonances, areproposed as optical nanoantennae. Electrodynamic calculations show that tunable,directional and wavelength selective emission enhancement is obtained throughout thevisible and near-infrared spectrum by varying the dielectric environment and thearray geometrical parameters, and thus tuning the Bragg modes. Large quantumefficiency enhancements are possible even in the case of poor emitters (1% intrinsicefficiency), spanning wavelengths that are relevant in lighting ( nm) and telecommunication () applications. Nanoantenna array angular emission is highly directional and extremelysensitive to the array geometrical parameters and the dielectric environment.

A Simple and Rapid Method of Making 2D and 3D Arrays of Gold Nanoparticles

Monodispersive gold nanoparticles can be synthesized by a dropwise addition of a reducing agent microemulsion to a gold ion microemulsion followed by immediate stabilization with 1-decanethiol. No size-selective precipitations or digestive ripening procedures are necessary. There is no need for metal functionalization of the surfactant AOT. Gold nanoparticles with an average size of 3.8 nm and a relative size dispersion of 5.4% were observed using n-heptane as a solvent. It seems possible to adjust the nanoparticle size by small changes in the carbon chain length of the solvent. Self-assembled 2D and 3D arrays of gold nanoparticles with adjustable sizes have been obtained on carbon-coated copper grids and on a silicon wafer. The arrays have good crystallinity as evidenced by the external morphology and transmission electron diffraction results. The size of the gold nanoparticle 3D arrays depends on the immersion time and can be greater than 15 microm. This approach could be used to synthesize other noble metal nanoparticle arrays that may lead to new materials for electronic and photonic applications.