Silver Nanoparticle Arrays Research Articles

SERS based detection of glucose with lower concentration than blood glucose level using plasmonic nanoparticle arrays

Surface Enhanced Raman Scattering (SERS) based detection of glucose, without using binder molecule, is difficult due to very small Raman scattering cross section of glucose and its very low affinity/binding with metal nanoparticles. This was overcome by using coupled plasmonic arrays of metal nanoparticles, which produced large field enhancement responsible for higher SERS intensity. It has been observed that the Raman intensity of glucose deposited on patterned Si with silver nanoparticle arrays is higher compared to that on plane Si and plane Si with randomly ordered nanoparticles. The nanoparticle arrays on patterned Si can detect glucose concentration as low as 5 × 10−5 g/ml, which is much lower than blood glucose level. The method can be used for the development of low concentration detection technologies for glucose.

Enhancing solar cell efficiency with plasmonic behavior of double metal nanoparticle system

The use of special arrangement of silver nanoparticle (Ag Np) arrays is presented in order to enhance light trapping capability of the thin film solar cells due to their ability to couple incident sunlight into localized modes. The spatial distribution of the nanoparticles in the matrix and their relative position are the important factors governing the performance of the device. Double nanoparticle system (DNS) over the silicon substrate, which is not a commonly studied system, is explored and the performance (absorption enhancement) was compared with periodically arranged single Ag Nps system. Finite difference time domain (FDTD) simulation has been performed to investigate the effect of silver nanoparticle array patterning on the absorption of solar radiation. The presence of DNS was found responsible for increased coupling of photons into plasmonic modes, and consequently increased absorption of photons into the substrate over a broad range of the solar spectrum.

Synthesis of the 3D AgNF/AgNP arrays for the paper-based surface enhancement Raman scattering application

Paper-based SERS sensor has attracted considerable attention recently, resulting from the separation, aggregation and high sensitive detection of biomolecules. However, optical losses, caused by the holes or “vase”-like defects, affect the overall intensity of the electromagnetic (EM) coupling and then the Raman signal. Silver nanoflowers (AgNFs) connected with silver nanoparticles (AgNPs) arrays are proposed and firstly obtained onto such “vase” surface to enhance the EM coupling. AgNFs are easily self-assembled on the defects, and the closed packed AgNPs can be formed on the other area. Multiple cascaded amplification mechanisms (localized surface plasmon mode and optical standing waves or refraction) are used to promote the EM magnification. Such paper card is also exploited successfully as an integrated platform, allowing for ultra-sensitivity (1 × 10−19M) CV and (1 × 10−20M) R6G detection.

Surface-enhanced Raman scattering effect of silver nanoparticles array

The Raman signal of adsorbed Raman probe molecule can be significantly enhanced by using metallic nanostructures with high-density hot spots as surface enhanced Raman scattering (SERS) substrates. A great effort has been devoted to the improving of the SERS detection sensitivity and reproducibility by preparing ordered metal nanostructure arrays with controlled particle size, shape and hot spot position, which are used as SERS substrates. In this paper, we prepare high-density Ag nanoparticle arrays by electrochemical deposition in anodic aluminum oxide (AAO) templates. The particle size and the nanogap between the adjacent particles can be adjusted by changing the deposition time. The structures and surface plasmons of Ag nanoparticle arrays are characterized by scanning electron microscopy and reflectance spectra. The size of the gap between the particles significantly affects the plasmon resonance and the plasmon coupling between the particles. The SERS properties of Ag nanoparticle arrays are investigated by using 1, 4-benzenedithiol (1, 4-BDT) as Raman probe molecule. The Ag nanoparticle arrays with high SERS detection sensitivity and high reproducibility (uniformity) are prepared by optimizing the deposition time (the nanogap between the adjacent particles), and the detection limit of the 1, 4-BDT can reach 10-13 mol/L. The relative standard deviation of the SERS signal intensity randomly measured from 20 spots on the Ag nanoparticle array substrate is 5.35%. The finite-difference time domain simulations confirm that the plasmon coupling between nanoparticles is strong, and that the coupling between the nanoparticles will increase as the nanogap decreases. Additionally, the local field is enhanced at the bottom of the nanoparticle and the gap between the Ag nanoparticle and the AAO template is larger. These results show that Ag nanoparticle array can be used as a high-efficiency SERS substrate.

Core-shell cylinder (CSC) nanotemplates comprising mussel-inspired catechol-containing triblock copolymers for silver nanoparticle arrays and ion conductive channels.

Catechol moieties, which are found in mussel-adhesive proteins, allow the interaction of various kinds of materials that results in substantial adhesion to a wide variety of materials and in the reduction of metal ions to solid metals. Various types of catechol-containing polymers mimicking adhesion and reduction properties have been reported, however, due to its reactivity to a wide variety of functional groups, only a few reports about the formation of block and sequence controlled copolymers containing catechol groups. This is the first report about the synthesis of triblock copolymers containing catechol groups by reversible-addition fragmentation transfer (RAFT) polymerization. The synthesized triblock copolymer forms a core–shell cylinder (CSC) phase-separated structure, in which PVCa domains located the surface of cylinders, and it works as a template for silver nanoparticle arrays and a proton conductive channel. Since triblock copolymer has broader latitude to form phase-separated structures, the triblock copolymer containing catechol groups can be suitable for templates of inorganic nanoparticle arrays.

Simulated near-field mapping of ripple pattern supported metal nanoparticles arrays for SERS optimization

An analytical model has been developed using a modified Yamaguchi model along with the wavelength dependent plasmon line-width correction. The model has been used to calculate the near-field response of random nanoparticles on the plane surface, elongated and spherical silver nanoparticle arrays supported on ion beam produced ripple patterned templates. The calculated near-field mapping for elongated nanoparticles arrays on the ripple patterned surface shows maximum number of hot-spots with a higher near-field enhancement (NFE) as compared to the spherical nanoparticle arrays and randomly distributed nanoparticles on the plane surface. The results from the simulations show a similar trend for the NFE when compared to the far field reflection spectra. The nature of the wavelength dependent NFE is also found to be in agreement with the observed experimental results from surface enhanced Raman spectroscopy (SERS). The calculated and the measured optical response unambiguously reveal the importance of interparticle gap and ordering, where a high intensity Raman signal is obtained for ordered elongated nanoparticles arrays case as against non-ordered and the aligned configuration of spherical nanoparticles on the rippled surface.

P.1.h.017 - Reinforcing properties of the glutamate receptors antagonists and karyotypic stability in rats

The use of special arrangement of silver nanoparticle (Ag Np) arrays is presented in order to enhance light trapping capability of the thin film solar cells due to their ability to couple incident sunlight into localized modes. The spatial distribution of the nanoparticles in the matrix and their relative position are the important factors governing the performance of the device. Double nanoparticle system (DNS) over the silicon substrate, which is not a commonly studied system, is explored and the performance (absorption enhancement) was compared with periodically arranged single Ag Nps system. Finite difference time domain (FDTD) simulation has been performed to investigate the effect of silver nanoparticle array patterning on the absorption of solar radiation. The presence of DNS was found responsible for increased coupling of photons into plasmonic modes, and consequently increased absorption of photons into the substrate over a broad range of the solar spectrum.

An atomistic-electrodynamics theory for the optical response of periodic lattices of metallic nanoparticles in the quantum size regime

We present a new theoretical method for calculating the optical properties of periodic arrays of metallic nanoparticles whose dimensions are in the quantum-size limit and cannot, therefore, be described by macroscopic electrodynamic theory based on Maxwell’s equations. In the first stage, the method calculates the scattering matrix for a single metal nanoparticle described as a polyhedral cluster of atoms, via a discrete-dipole approximation/point-matching technique. The resulting scattering matrix is incorporated into a layer-multiple-scattering technique which allows the modeling of two- and three-dimensional nanostructures containing very small metal nanoparticles. The method is demonstrated for square arrays of silver nanoparticles with radii below 2 nm and the corresponding results are compared against classical local and nonlocal electrodynamic approaches.

Preparation, morphology and sonication time dependence of silver nanoparticles in amphiphilic block copolymers of PEO with polystyrene or PMMA

Composite materials comprising arrays of silver nanoparticles in amphiphilic copolymers have been prepared by sonochemically enhanced borohydride reduction of precursor silver nitrate (AgNO3). The precursor was incorporated into the cores of polymeric micelles formed from block copolymers of polystyrene (PS) or poly(methyl methacrylate) (PMMA) with poly(ethylene oxide) (PEO). The copolymers were synthesised with varying hydrophobic block lengths from a PEO macroinitiator by atom transfer radical polymerization (ATRP). UV/visible spectroscopy was used to confirm the formation of elemental silver and the effect of sonication time on the appearance of the silver nanoparticles was determined. The growth was faster than when gold nanoparticles are formed in comparable block copolymers. Nanoparticles formed in copolymers with PMMA blocks were more stable to agglomeration than when polystyrene was used. Electron microscopy revealed the morphology of the nanocomposites which confirmed that both block copolymers are vehicles for the formation of well-defined films containing nanoparticulate silver. However, AgNP formation shows some significant differences from previous reports of gold NP containing materials formed under similar conditions.

Plasmonic coupling induced by growing processes of metal nanoparticles in wrinkled structures and driven by mechanical strain applied to a polidimethisiloxisilane template

Plasmonic coupling induced by growing processes of metal nanoparticles in wrinkled structures and driven by mechanical strain applied to a polidimethisiloxisilane template

Plasmonic lattice resonance-enhanced light emission from plastic scintillators by periodical Ag nanoparticle arrays

We have demonstrated that periodical arrays of silver nanoparticles can enhance the light emission from a plastic scintillator layer on the surface of a silicon substrate. The enhancement is attributed to surface lattice resonances with a photonic-plasmonic nature. Although the enhancement exhibits directional characteristics for individual wavelengths, the wavelength-integrated enhancement shows a monotonous increase with increasing emission angle. As a result, an overall 1.81-fold wavelength- and angle-integrated enhancement has been obtained. This observation is promising for fundamental and applied research into enhanced luminescent material layers on opaque substrates.

Enhanced photoresponsivity in organic field effect transistors by silver nanoparticles

Organic semiconductors (OSC) such as thiophene-based oligomers exhibit useful electronic and optical properties making them applicable in photo-sensing devices. Generally, thiophene-based photodetectors exhibit a decent responsivity with a spectral sensitivity determined by the OSC's absorption properties. We present a simple, yet efficient method to enhance and spectrally tune the photoresponsivity of organic phototransistors (OPTs) utilizing the plasmonic properties of embedded metallic nanoparticles. The ability to fabricate and characterize nanostructures with high accuracy allows for tailoring of the optical properties of metal nanoparticles (NPs) and thereby tuning of the spectral range of enhanced photoresponsivity. In this work we have investigated OPTs based on the molecule 5,5″-bis(naphth-2-yl)-2,2':5′,2″-terthiophene (NaT3). We have fabricated OPTs with electron beam lithography-defined arrays of silver NPs under the organic thin-film. The photoconductivity of OPTs with and without NPs was characterized under spectrally resolved illumination. The OPTs exhibit significant responsivity at wavelengths below 500nm essentially coinciding with the absorption spectrum of NaT3. Finite element simulations of the optical properties of the NPs reveal large electric field enhancement at the plasmon resonances. At these wavelengths (350→500nm) the experimentally measured photoresponsivity of OPTs with NPs is significantly increased compared to the responsivity for OPTs without NPs. Due to a variation in particle size and shape of the fabricated silver NPs, a spectrally broad enhancement is predicted, which is in agreement with the experimental results. The results show that the photoresponsivity is dominantly enhanced in a spectral region of low OSC absorption coinciding with the localized surface plasmon resonances of the NPs. This work demonstrates that it is possible to improve and tailor the responsivity spectrum of photoactive organic devices by integration of metal nanoparticles.

Fabrication and laser-assisted modification of the Ag particles ensembles supporting quadrupole plasmon oscillations

A combination of physical vapour deposition, thermal annealing and laser irradiation was used to tailoring of the silver nanoparticles array on a quartz substrate. This method for control of optical properties is exploit 355-nm pulsed laser irradiation. Experimental separation of three main overlapped plasmonic modes, dipoles that correspond to parallel and perpendicular oscillations and quadrupole with maximum wavelength at 355 nm, in extinction spectrum of Ag nanoparticles ensembles was demonstrated. It was shown that the laser post-processing of the nanoparticles array in spectral vicinity of the quadrupole band leads to selective ablation of nanometer particles. This process resulted to close-packing of the nanoparticles ensemble on top of the substrate causing, in turn, formation of ‘hot-spots’ and absorptive bands in the near IR range. Using the laser post-processing as persistent spectral hole burning technique, a dephasing time of quadrupole plasmon resonances was experimentally defined for the first time.

Broadband Absorption Enhancement in μc-Si:H Thin-Film Solar Cells Based on Silver Nanoparticle Arrays

The thin-film solar cell structure with a broadband absorption enhancement is reported. We designed spherical silver (Ag) nanoparticle arrays on or embedded partially into indium tin oxide (ITO) layer of the hydrogenated microcrystalline silicon ([Formula: see text]c-Si:H) thin-film solar cells. The geometrical parameters, such as nanoparticle radius ([Formula: see text], array period ([Formula: see text] and ITO layer thickness ([Formula: see text] are optimized by using the finite element method (FEM). The numerical results show that the key parameter that influences the integrated absorption is period/radius ratio ([Formula: see text]/[Formula: see text] for Ag nanoparticle arrays. Embedding nanoparticle arrays partially into ITO layer with the appropriate thickness can improve broadband light-trapping. The optimized structure shows 50.1% enhancement in the integrated absorption compared to the reference cell when [Formula: see text][Formula: see text]nm, [Formula: see text][Formula: see text]nm and [Formula: see text][Formula: see text]nm. Furthermore, physical mechanisms of absorption enhancement in different wavelength range are discussed according to the electrical field amplitude distributions in the solar cells.

Morphology Optimization of Silver Nanoparticles Used to Improve the Light Absorption in Thin-Film Silicon Solar Cells

Silver nanoparticle (NP) arrays are used as antireflection coating to enhance light trapping capability of thin-film silicon solar cells. In this paper, we theoretically investigate the differences of light absorption distribution between the silver NP (spherical and hemispherical) array layer and the crystalline silicon (CS) substrate. Compared to the naked silicon of the same thickness, the results show that only the flattened hemispherical silver NPs can really improve the light trapping ability and make the light absorption of CS body increase by 26%; the optimum ratio of lateral (NP diameter divided by the array periodicity) and longitudinal (NP height divided by diameter) are 0.86 and 0.22, respectively.

Direct growth of plasmonic nanorod forests on paper substrates for low-cost flexible 3D SERS platforms

Paper substrates, coated with ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs), allowed the production of inexpensive, highly-performing and extremely reproducible three-dimensional (3D) SERS platforms. The ZnO NRs were synthesized by a simple, fast and low-temperature hydrothermal method assisted by microwave radiation and made SERS-active by decorating them with a dense array of silver nanoparticles deposited via a single-step thermal evaporation technique. Using Rhodamine 6G (R6G) as a probe molecule, with an amount down to 10−9 M, the SERS substrates allowed a Raman signal enhancement of 107. The contribution of the inter-Ag-NPs gaps for 3D geometry, ZnO NRs orientation and the large sensing area allowed by the NR scaffolds, were determinant factors for the significant Raman enhancement observed. The results demonstrate that plasmonic nanorod forests, covered with Ag NPs, are efficient SERS substrates with the advantages of being recyclable, flexible, lightweight, portable, biocompatible and extremely low-cost.

Lasing in dark and bright modes of a finite-sized plasmonic lattice

Lasing at the nanometre scale promises strong light-matter interactions and ultrafast operation. Plasmonic resonances supported by metallic nanoparticles have extremely small mode volumes and high field enhancements, making them an ideal platform for studying nanoscale lasing. At visible frequencies, however, the applicability of plasmon resonances is limited due to strong ohmic and radiative losses. Intriguingly, plasmonic nanoparticle arrays support non-radiative dark modes that offer longer life-times but are inaccessible to far-field radiation. Here, we show lasing both in dark and bright modes of an array of silver nanoparticles combined with optically pumped dye molecules. Linewidths of 0.2 nm at visible wavelengths and room temperature are observed. Access to the dark modes is provided by a coherent out-coupling mechanism based on the finite size of the array. The results open a route to utilize all modes of plasmonic lattices, also the high-Q ones, for studies of strong light-matter interactions, condensation and photon fluids.

Enhancing light reflective properties on ITO glass by plasmonic effect of silver nanoparticles

The preparation of well-defined silver (Ag) nanoparticle arrays is reported in this paper. Ag nanoparticles are electrodeposited on Indium tin oxide (ITO) coated glass substrates at 30°C. The size, shape and periodicity of the Ag nanoparticle arrays are well-controlled. We study the effect of particle size and interparticle distance on reflection enhancement. The sample at the deposition potential of −0.2V for an electrodeposition time of 3600s exhibits an enhancement of 28% in weighted reflection in contrast with bare ITO glass. This study reports the high reflection of Ag nanoparticle arrays by electrodeposition method might be application to large-scale photovoltaic devices.

Localized surface plasmon resonance tuning via nanostructured gradient Ag surfaces

Gradient surfaces, i.e. surfaces whose properties change gradually along the sample length, receive increasing attention as they facilitate optimization of surface properties for particular applications. In this study we present vacuum-based strategy for fabrication of irregular silver nanoparticle arrays with gradient optical properties. This approach is based on the magnetron sputtering of Ag performed at low pressure in argon atmosphere. The gradient character of deposited arrays is achieved by use of a movable mask that is introduced in the vicinity of the substrate. It is shown that this technique enables to tailor the course of the gradient of localized surface plasmon resonance (LPSR) either by the speed of the mask or by additional deposition of silver on the top of surface pre-seeded by the gradient nanoparticle arrays.

Characterization of anisotropically shaped silver nanoparticle arrays via spectroscopic ellipsometry supported by numerical optical modeling

The present investigation aims to study the optical response of anisotropic Ag nanoparticle arrays deposited on rippled silicon substrates by performing a qualitative comparison between experimental and theoretical results. Spectroscopic ellipsometry was used along with numerical calculations using finite-difference time-domain (FDTD) method and rigorous coupled wave analysis (RCWA) to reveal trends in the optical and geometrical properties of the nanoparticle array. Ellipsometric data show two resonances, in the orthogonal x and y directions, that originate from localized plasmon resonances as demonstrated by the calculated near-fields from FDTD calculations. The far-field calculations by RCWA point to decoupled resonances in x direction and possible coupling effects in y direction, corresponding to the short and long axis of the anisotropic nanoparticles, respectively.