Silver Nanoparticle Arrays Research Articles

Preparation of ordered silver angular nanoparticles array in block copolymer film for surface-enhanced Raman spectroscopy

We report a single-step method of preparation of ordered silver nanoparticles array through template-assisted nanoparticles synthesis in the semidried block copolymer film. Ordered nanoparticles were prepared on different substrates by the proper choice of solvents combination and preparation procedure. In particular, block copolymer and silver nitrate were dissolved in the mix of tetrahydrofuran, toluene, and n-methylpyrolidone. During short spin-coating procedure ordering of block copolymer, evaporation of toluene and preferential silver redistribution into poly(4-vinylpyridine) block occurred. Rapid heating of semidry film initiated silver reduction, removing of residual solvent and creation of ordered silver array. After polymer removing silver nanoparticles array was tested as a suitable candidate for subdiffraction plasmonic application–surface-enhanced Raman scattering. Enhancement factor was calculated and compared with the literature data.

Laser deposition of bimetallic island films

In this work the results of a bimetallic Au-Ag structure deposition from the colloidal system by nanosecond laser radiation are presented. The formation of the extended arrays of gold and silver nanoparticles with controlled morphology is examined. We report the results of formation bimetallic islands films with various electrical and optical properties. The changes in the optical properties of the obtained thin films are found to depend on their morphology.

Plasmon-Enhanced Performance of an Array of Core-Shell Silver Nanoparticles Photodeposited onto a Titanium Dioxide Layer

A plasmonic photocatalytic reactor which composed of a periodic array of core-shell silver nanoparticles (CSSNPs) photodeposited onto a Titanium Dioxide (TiO2) thin film in a multilayer rotating-disk system was numerically investigated by using three-dimensional finite element method. Results show that the proposed structure can exhibit much higher photocalytic activity in a broad range of incident angle of light that are not observed for the same counterpart without the CSSNPs on the SiO2 surface. The enhanced electric field distribution and intensity could be expanded as the inner diameter of CSSNPs and incident angle of light increased.

Oil-in-water emulsion as fabrication platform for uniform plasmon-controlled two-dimensional metallic nanoparticle array

Gold/silver nanoparticles were trapped at the oil/water interface of oil droplets dispersed in water. The metallic nanoparticles were self-assembled into a uniform two-dimensional large array structure through the aggregation and coalescence of the nanoparticle-covered oil droplets. The plasmon resonance of the array structure was tunable and a surface-enhanced Raman scattering measurement was performed with the silver nanoparticle array. The enhancement factor was ∼105 and enhanced Raman signals were observed over the whole array () with high reproducibility, which is an advantage of a self-assembly method using a liquid/liquid interface.

Reliable and well-controlled synthesis of noble metal nanoparticles by continuous wave laser ablation in different liquids for deposition of thin films with variable optical properties

We report the results of continuous wave laser interactions with both gold and silver targets in the presence of different liquids (deionized water, ethanol, and glycerol). Upon moderate laser irradiation at wavelength of 1.06 nm during 30 min, nanoparticle colloids are shown to be formed with surprisingly narrow size distributions and average dispersion as small as 15–20 nm. The average particle sizes range between 8 and 52 nm for gold and between 20 and 107 nm for silver. This parameter is shown to be stable and well-controlled by such laser parameters as intensity and effective irradiation time, as well as by the choice of the liquid phase. The possibilities of an efficient control over the proposed synthesis techniques are discussed, and the results of a bimetallic Au–Ag structure deposition from the obtained colloids are presented. The formation of the extended arrays of gold and silver nanoparticles with controlled morphology is examined. The changes in the optical properties of the obtained thin films are found to depend on their morphology, in particular, on the particle size, and distance between them.

Laser Power Threshold of Chemical Transformation on Highly Uniform Plasmonic and Catalytic Nanosurface

Noble metallic nanosurface exhibits both plasmonic and catalytic functions. Surface-enhanced Raman scattering of para-aminothiophenol (p-ATP) was measured on a highly uniform two-dimensional silver nanoparticle array at different intensities of an excitation laser (532 nm) ranging from 4 to 4000 W/mm2. It was observed that p-ATP was chemically transformed to 4,4′-dimercaptoazobenzene (DMAB) with the laser intensities of ≥40 W/mm2 during the Raman measurement. At 4 W/mm2, the Raman peaks of DMAB disappeared, which indicates that the laser intensity was insufficient for the chemical transformation although it was sufficient for the Raman measurement. The highly uniform silver nanoparticle array allowed quantitative analysis on the Raman peak intensity. The threshold of the chemical transformation from p-ATP to DMAB was estimated to be ∼18.8 W/mm2 on the silver nanoparticle array whose enhancement factor is ∼104.

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties.

Silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal–organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryotic cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.

Silver Nanoparticle Arrays Prepared by In Situ Automatic Reduction of Silver Ions in Mussel‐Inspired Block Copolymer Films

Block copolymer phase separation has been employed to form templates for the fabrication of nanoscale patterns of metals due to their characteristic size scales that range from several nanometers to tens of nanometers. In the present work, poly(vinyl catechol‐block‐styrene) PVCa‐b‐PSt synthesized with various compositions forms unique microphase‐separated structures. Silver nanoparticles are spontaneously formed inside of the PVCa phases due to the reductive properties of the catechol moieties. The alignment and formation of silver nanoparticle arrays is successfully achieved without the need for high‐temperature thermal treatment or chemical reduction processes. The present system can be applied to the formation of nanoparticle arrays with a wide variety of metals by control of their arrangement. image

Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.

Optical Properties of One-, Two-, and Three-Dimensional Arrays of Plasmonic Nanostructures

This Feature Article describes research on the optical properties of arrays of silver and gold nanoparticles, particles that exhibit localized surface plasmon resonances in the visible and near-infrared. These resonances lead to strong absorption and scattering of light that is strongly dependent on nanoparticle size and shape. When arranged into multidimensional arrays, the nanoparticles strongly interact such that the collective properties can be rationally designed by changing the dimensions of the array (one-, two-, or three-dimensional), interparticle spacing, and array shape or morphology. Emerging from this work is a large body of literature focusing on one-, two-, and three-dimensional arrays, which provide unique opportunities for realizing materials with interesting and unusual photonic and metamaterial properties. Electrodynamics theory provides an accurate description of the optical properties, often based on simple models such as coupled dipoles, effective medium theory, and anomalous diffrac...

A Surface Design for Enhancement of Light Trapping Efficiencies in Thin Film Silicon Solar Cells

We report on a surface design of thin film silicon solar cells based on silver nanoparticle arrays and blazed grating arrays. The light transmittance is increased at the front surface of the cells, utilizing the surface plasmon resonance effect induced by silver nanoparticle arrays. As a reflection layer structure, blazed gratings are placed at the rear surface to increase the light reflectance at bottom of the thin film cells. With the combination of the silver nanoparticle arrays and the blazed gratings, the light trapping efficiency of the thin film solar cell is characterized by its light absorptance, which is determined from the transmittance at front surface and the reflectance at bottom, via the finite-difference time-domain (FDTD) numerical simulation method. The results reveal that the light trapping efficiency is enhanced as the structural parameters are optimized. This work also shows that the surface plasmon resonance effect induced by the silver nanoparticles and the grating characteristics of the blazed gratings play crucial roles in the design of the thin film silicon solar cells.

Wide-range modulation and micro-identification of the plasmonic behaviour in gas phase-deposited silver nanoparticle arrays

The surface plasmon resonance properties of silver cluster-deposited multi-structured nanoparticle arrays are investigated for various substrate surfaces. A remarkable redshift from 396 to 572 nm is observed on Formvar film-decorated substrate with controlled particle coverage under in situ surface plasmon resonance wavelength monitoring. The redshift induced by the electromagnetic near-field couplings between the silver nanoparticles and the tuning of the local surface plasmon resonance wavelength in the nanoparticle arrays is found to be correlated to the fraction of closely spaced particle-pairs. Plasmonic ruler behaviour of the closely spaced particle-pair fraction is established and used as an indicator on a gradient silver nanoparticle micro-assembly for identifying the local surface plasmon resonance property in nanostructures. With a 473 nm laser probe, the featured surface plasmon resonance of the optimal nanoparticle assembly for surface-enhanced Raman scattering is found to be around 515 nm.

Controlling quantum dot emission by plasmonic nanoarrays.

Metallic nanoparticle arrays support localized surface plasmon resonances (LSPRs) and propagating surface lattice resonances (SLRs). We study the control of quantum dot (QD) emission coupled to the optical modes of silver nanoparticle arrays, both experimentally and numerically. With a hybrid lithography-functionalization method, the QDs are deposited in the vicinity of the nanoparticles. Directionality and enhancement of the emission are observed in photoluminescence spectra and fluorescence lifetime measurements, respectively. Similar features are also demonstrated in the numerical simulations. The tunable emission of this type of hybrid structures could lead to potential applications in light sources.

Polarized interference imaging of dense disordered plasmonic nanoparticle arrays for biosensor applications

We report on light scattering by dense short-range ordered gold and silver nanoparticle arrays with 25 nm diameter and 50 nm center separation produced by masked deposition through anodized aluminum oxide membranes. Local resonant regions are formed, which scatter light with polarization components perpendicular to the incident wave due to electromagnetic coupling between particles at random angles. The observed cross-polarized far-field images have a granular structure that morphs in response to environmental variations in the article near field. We quantify the changes in the recorded images by 2D correlation matrix calculation and demonstrate the application of this approach to biomolecular sensing by using various concentrations of cysteine solution as a model system. The presented method may potentially compete with colorimetric sensor techniques since the detection setup does not require any spectroscopic instruments.

Tuning the Plasmonic Extinction Resonances of Hexagonal Arrays of Ag Nanoparticles

Plasmonically enhanced effects on a self-assembled, hexagonal array layer of ~4-nm silver nanoparticles are analyzed using three-dimensional finite-difference time-domain (3D FDTD) simulations and compared against experimentally measured extinction spectra. The effect of particle size, lattice spacing, and lack of monodispersity of the hexagonal array of silver nanoparticles on the extinction resonance was investigated to help determine optimal design specifications for efficient organic solar power harvesting.

Efficient Light Trapping Structures of Thin Film Silicon Solar Cells Based on Silver Nanoparticle Arrays

We report on an investigation into the light trapping efficiency for structures of thin film silicon solar cells, with silver nanoparticle arrays at both front and rear surfaces of the cells. The light trapping efficiencies of the structures are quantified by the weighted mean values of the photons absorbed by the silicon layer, over a wavelength range of 400 to 1100 nm. The weighted mean values are calculated under various combinations of the structural parameters for the silver nanoparticle arrays. The results show that efficient light trapping structures of the solar cells can be achieved by carefully choosing the structural parameters of the metal arrays. This great light absorption by the cell is attributed to the effects induced by the surface plasmon excitation of the metal particles. Based on the analyses, we also suggest that the method employed in this work may be a useful tool to probe other similar structures of the solar cells with metal nanoparticle arrays.

Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition

Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were prepared by the pulsed laser deposition from the back flux of erosion torch particles in argon atmosphere on the substrate placed at the target plane. Preparation conditions of the films were set by argon pressure, energy density of laser pulses, their amount and substrate position relatively to the torch axis. The films were prepared with gradient thickness, variable Ag NP sizes and distance between them along the length of substrate as well as corresponding maxima in the spectra of local surface plasmon absorption. Plasmon effects of the Raman scattering enhance in the matter of the Ag NP shell gave the opportunity to register the spectral bands caused by an extremely small quantity of silver compounds with oxygen and carbon. The possible nature of individual bands in the Raman spectrum was analyzed. The obtained results are important for interpretation of the Raman spectra of analytes based on the prepared SERS substrates.

Design of Novel Metal Nanostructures for Broadband Solar Energy Conversion

Solar power holds great potential as an alternative energy source, but current photovoltaic cells have much room for improvement in cost and efficiency. Our objective was to develop metal nanostructures whose surface plasmon resonance (SPR) spectra closely match the solar spectrum to enhance light absorption and scattering. We employed the finite-difference time-domain simulation method to evaluate the effect of varying key parameters. A novel nanostructure with SPR absorption matching a region of the solar spectrum (300 to 1500 nm) that contains 90% of solar energy was successfully designed. This structure consists of a large gold-silica core-shell structure with smaller gold nanoparticles and nanorods on its surface. Such complex nanostructures are promising for broad and tunable absorption spectra. In addition, we investigated the SPR of silver nanoparticle arrays, which can achieve scattering close to the solar spectrum. We demonstrated an improvement in efficiency of over 30% with optimal nanoparticle radius and periods of 75 nm and 325 nm, respectively. In combination, our studies enable high-efficiency, tunable, and cost-effective enhancement of both light absorption and scattering, which has potential applications in solar energy conversion as well as biomedical imaging.

Plasmonic Filters Based on Lithographically Patterned and Hexagonally Arranged Triangular Silver Nanoparticles Array

A plasmonic filter applied in visible regime is proposed on the basis of hexagonally arranged triangular silver nanoparticle arrays. A method using discrete dipole approximation (DDA) to aid design parameters of the silver nanoparticle arrays is adopted for the filter design and optimization on the basis of computational numerical calculation. The influence of the particle’s thickness and period on the extinction spectrum is studied using the DDA-based computational analysis. Considering the nanofabrication condition, arrays with 40 nm thickness and 230 nm period are selected and fabricated by using nanosphere lithography (NSL) technique. The experimental spectrum is basically in agreement with the theoretical spectrum derived by the DDA calculation.

Facile and rapid fabrication of large-scale silver nanoparticles arrays with high SERS performance

A facile and rapid self-assembly method for fabricating a high performance SERS substrate was reported here by using ascorbic acid as an active reagent.