Surface Plasmons Of Silver Nanoparticles Research Articles

Spintronic hydrogen evolution induced by surface plasmon of silver nanoparticles loaded on Fe- and Co-doped ZnO nanorods

The spin–plasmon-assisted quantum entanglement modulator enables solar-to-hydrogen water splitting cells prepared by silver NPs coated on TM:ZnO (TM: Fe, Co) NRs with circularly polarized light of coherent ħ/−ħ light radiation.

Spectral and Temperature Dynamics of the Processes inside Aqueous Droplets Containing Eosine Molecules and Silver Nanoparticles upon Laser Excitation in the IR and Visible Ranges

Photophysical and thermal processes in a droplet of an aqueous solution of eosine with silver nanoparticles (NPs) produced by laser ablation are studied upon double laser excitation, stationary (λ = 532 nm) and IR pulsed (λ = 10.6 μm). It is established that after IR exposure, long-lived luminescence is generated due to intercombination transitions inside molecules, the intensity of which depends on the concentration of eosine and NPs, and the coordinates of the region of luminescence glow in a microvolume of the droplet. The processes of thermal diffusivity and thermal conductivity after exposing a drop of the solution to IR radiation are modeled. The effect the surface plasmons of silver NPs have on the efficiency of quenching the thermally activated luminescence (TL) of a droplet is determined, the rate constant of which is equal to the constant of diffusion.

Excited-State Dynamics of Quinine Sulfate and Its Di-Cation Doped in Polyvinyl Alcohol Thin Films Near Silver Nanostructure Islands.

The present study demonstrates the near-field effect of silver nanostructure island films (SNIFs) on the photophysics and exited-state dynamics of quinine sulphate (QS) and its di-cation (QSD), doped in polyvinyl alcohol (PVA) films. The results indicate a nearly 3.8-fold enhancement in absorption and 4000-fold enhancement in fluorescence in SNIF-coated QS-doped PVA films, whereas only twofold enhancement in absorption and sevenfold enhancement in fluorescence intensity are found in SNIF-coated QSD-doped PVA films. However, an increase in photostability and a decrease in decay time have been observed in both the SNIF-coated films as compared to their uncoated forms. Further, a decrease in the magnitude of the edge excitation red shift in emission spectra along with a red shift in the La band and a rise in the intensity of the Lb band of excitation is observed in SNIF-coated QSD films because of strong coupling of the Lb band with the surface plasmons of silver nanoparticles. Moreover, X-ray photoelectron spectroscopic measurement of silver nanoparticle-coated QS–PVA films shows no change in 3d3/2 and 3d5/2 transitions of silver, whereas the decrease in energy in these silver transitions in the QSD–PVA system is observed as compared to silver nanoparticle-coated PVA films. These results indicate the formation of a field-governed radiating plasmon and plasmon-coupled unified fluorophore system, respectively. This affects the photophysics of both of the molecules by plasmonic coupling of the Frank–Condon state, solvent relaxation state, and charge-transfer state by different orders of magnitude.

Silver Nanoparticle-Based Arrays into Mesoporous Thin Films Structures for Photoelectronic Circuits

Background: Silver nanosystems have attracted considerable attention for numerous applications in optoelectronics. The localized surface plasmon of silver nanoparticles embedded into mesoporous titania gives rise to an enhancement of local optical field in the vicinity of Ag nanoparticles which act as efficient light-trapping components, resulting in a visible wavelength-dependent photocurrent. Objective: In this paper, we synthetized patterned nanocomposites formed by titania mesoporous thin films loaded with alkanethiol functionalized Ag nanoparticles and we demonstrated that these stable and accessible nanostructures possess a photocurrent response. Method: Mesoporous thin films are created by combining sol-gel synthesis and template selfassembly. Based on a photolithography technique, silver nanoparticles were selectively photodeposited and then stabilized with octanethiols. Current vs. voltage curves with and without light were compared, where selective light wavelength measurements were achieved by using visible bandpass filters. The optofluidic behavior was evaluated by placing a drop of solutions on the mesoporous film. Results: We demonstrate photocurrent in these mesoporous thin film structures decorated with chemistabilized Ag nanoparticle-based conductive arrays, with significantly enhanced photocurrent peak at the plasmon resonant wavelength around 540 nm. Our findings offer a possibility to perform improved fluid detection with silver-mesoporous titania electronic devices. Conclusion: We showed that an optofluidic sensitive nanocomposite circuit consisting of alkanethiol- functionalized metal nanoparticles embedded in a mesoporous oxide thin film matrix can be produced.

Microstructure and ellipsometric modelling of the optical properties of very thin silver films for application in plasmonics

Excitation of surface plasmons in silver nanoparticles is a promising method for enhancing light trapping. The present paper reports results for the optical properties of the nanocrystalline silver thin films in attempt to understand the effects of the particle size. The microstructure of the films was probed by scanning electron-microscopy, Atomic Force microscopy (AFM) and X-ray diffraction (XRD). The size of the crystallites/grains calculated from the XRD measurements by the Debye-Scherrer formula is in a good agreement with the AFM results. The optical properties were determined from spectral ellipsometric measurements. It was shown that the Drude-Lorentz model is suitable for characterization of porous films, while an island structure required the extended Drude model with frequency dependent damping parameter, Γ. It was demonstrated that the maximum of the imaginary part of the complex permittivity,ε^ω=ε′ω+iε′′ω, that is due to the transverse oscillations of the polarization of the silver grains, can be positioned in the energy range of 1.5–2.8eV in dependence of the deposition rate; it's been shifted to higher energies when reducing the grains size. Contemporary, the resulting changes in the surface/volume ratio lead to shifts the maximum in the loss function Im−1ε^ω from 3.8 to 3.5eV.

Metal-Enhanced Fluorescence: Ultrafast Energy Transfer from Dyes in a Polymer Film to Metal Nanoparticles.

Fluorescence from dye molecules dispersed in thin polymer layers increases by 20-25 times when a silver island film exists beneath the layer. Polymer layers of <100 nm thick cover the silver island film to minimize emission quenching from direct contact and also keep the dye molecules in close proximity to the metal nanosurface for possible fluorescence enhancements by silver island film. We report an ultrafast radiation process of ~400 ps lifetime from the surface plasmons of silver nanoparticles observed in time-resolved fluorescence of rhodamine 6G and DCM in thin polymer films coated on silver island surface. The ultrafast energy transfer and fluorescence from metal nanoparticles might be strongly related to the efficiency of metal-enhanced fluorescence.

Strong Coupling between ZnO Excitons and Localized Surface Plasmons of Silver Nanoparticles Studied by STEM-EELS.

We investigated the strong coupling between the excitons of ZnO nanowires (NWs) and the localized surface plasmons (LSPs) of individual Ag nanoparticles (NPs) by monochromated electron energy loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscopy (STEM) instrument. The EELS results confirmed that the hybridization of the ZnO exciton with the LSPs of the Ag NP created two plexcitons: the lower branch plexcitons (LPs) with a symmetrical dipole distribution and the upper branch plexcitons (UPs) with an antisymmetrical dipole distribution. The spatial maps of the LP and UP excitations reveal the nature of the LSP-exciton interactions. With decreasing size of the Ag NP the peak energies of the LPs and UPs showed a blue-shift and an anticrossing behavior at the ZnO exciton energy was observed. The coupled oscillator model explains the dispersion curve of the plexcitons and a Rabi splitting energy of ∼170 meV was deduced. The high spatial and energy resolution STEM-EELS approach demonstrated in this work is general and can be extended to study the various coupling interactions of a plethora of metal-semiconductor nanocomposite systems.

An approach to achieve significantly faster luminescence decay of thin-film scintillator by surface plasmons

A fast component of 2.2 ns from the LSO thin-film scintillator was achieved through coupling of scintillator with surface plasmons of silver nanoparticles. From the emission spectra, the observed fast component is from the transition of 5d to 4f level of Ce3+ in LSO. The fast component is attributed to the enhanced spontaneous recombination rate due to the surface plasmons. The present demonstration provides an interesting approach to improve the timing resolution of scintillator, which is distinguished from these conventional methods.

Optimum surface condition for plasmonic Ag nanoparticles in polycrystalline silicon thin film solar cells

Excitation of surface plasmons in silver nanoparticles is a promising method for increasing the light absorption in solar cells and hence, the cell photocurrent. The optical environment is an important key factor to consider when designing plasmonic solar cells because it affects the surface plasmon characteristics. In this paper, we applied the silver nanoparticles on the rear side of polycrystalline silicon thin film solar cells and systematically investigated the optimum surface condition for maximising plasmonic enhanced light absorption in the cells. Three different environments, thermal silicon dioxide (SiO2), native SiO2, and oxide-free silicon surface were investigated. We found that the existence of the SiO2 layer between Si and nanoparticles has a major effect on Qscat and therefore, the absorption in the cells. We also found that nanoparticles on the thermal SiO2 layer showed that the peak of Qscat is located at the visible light wavelengths &amp;lt;700 nm, nanoparticles on the native SiO2 layer and directly on Si sample showed that their peaks of Qscat are positioned at the longer wavelengths &amp;gt;700 nm. The sample with nanoparticles on the native SiO2 layer showed the highest potential short circuit current density (Jsc) enhancement, 62.5%, and absolute Jsc enhancement, 32.3%. On the other hand, the sample with nanoparticles on the thermal SiO2 layer indicated 19.6% enhancement of Jsc.

Immobilization of Silver Nanoparticles by Peptide Nucleic Acids in Surface Plasmon Enhanced Dye-Sensitized Solar Cells

Light absorption of dye molecules can be increased by the localized surface plasmons of silver nanoparticles (AgNPs), which can be used to enhance the photocurrent generation of dye-sensitized solar cells (DSSCs). Simultaneously, however, reverse electron transfer from the TiO2 working electrode to the I3−/I− electrolyte is also increased. In this work, peptide nucleic acid (PNA) was successfully used to immobilize AgNPs at different distances from the TiO2 layer and dye molecules. Together with results from previous studies, results here reveal that the optimal distance is between the lengths of possibly bent 2-nm alkane-thiols and 3.2- to 4.2-nm PNA. AgNPs immobilized by hybridization of PNA of this length lead to an increase in energy conversion efficiency from 3.1% to 4.0%. Furthermore, PNA forms π-electron stacks upon hybridization, which can reduce reverse electron transfer. With double-stranded PNA, the internal quantum efficiency of DSSCs could be increased more than 10%, from 73% to 88%, with 5.8- to 6.8-nm long double-stranded PNA.

Nonlinear phenomenon of surface enhanced Raman scattering caused by surface plasmon

Silver nanoparticles are synthesized through thermal evaporation for molecular detection using surface enhanced Raman scattering microscopy. The optical properties of silver nanoparticles are obtained by ultraviolet-visible spectrometry, which show the resonance wavelength near the detecting wavelength of Raman scattering (488 nm). Using rhodamine 6G as a test molecule, the results in this paper show that the detected Raman peak intensity has a nonlinear relationship with the incident power density when surface plasmon of silver nanoparticles was excitated by incident photon. This nonlinear phenomenon of surface enhanced Raman scattering caused by "hot spot" with high electromagnetic field strength provides an effective way to obtain high scattering intensity without high incident power density, which may expand the scope of Raman scattering application.

Improved Charge Separation Properties of Organic Hetero-Junction Solar Cells by Self-Assembled Monolayers Anchored Ag Nanoparticles

We investigate the effect of self-assembled monolayers and localized surface plasmons of silver nano-particles on an organic solar cell consisting of zinc phthalocyanine as an active layer. The device was fabricated by covalent attachment of silver nanoparticles on n-type silicon substrates using self-assembled monolayer of 4-mercaptophenol. Power conversion efficiency is increased up to 8 times as compared to a reference device with merely 0.13% photo-conversion efficiency containing no self-assembled monolayers and silver nano-particles. We believe that improved conductivity at the interface due to the aromatic self-assembled monolayer and the increased local electric field experienced by the active layer in presence of silver nano-particles act in synergy towards the higher population of excitons and dissipation of charge.

Photoabsorption-enhanced dye-sensitized solar cell by using localized surface plasmon of silver nanoparticles modified with polymer

Photoelectric conversion efficiency ( E ff) of a dye-sensitized solar cell (DSSC) was improved by localized surface plasmon on silver (Ag) nanoparticles modified with polyacrylate-based comb-shaped block copolymer. The polymer-modified Ag nanoparticles were inserted into pores of a TiO 2 film in a DSSC. Then, the characteristics of this photoabsorption enhanced DSSC (PE-DSSC) with the Ag nanoparticles were evaluated. To clarify the effect of Ag nanoparticles on the characteristics, the thickness of the TiO 2 film in the DSSC was 2 μm, thinner than that for a typical DSSC (10 μm). A PE-DSSC showed an improved E ff of 2.5%, compared with about 1.5% for a DSSC with no Ag nanoparticles.

Size-dependent surface-plasmon-enhanced photoluminescence from silver nanoparticles embedded in silica

The size dependence of the photoluminescence spectra from silver nanoparticles embedded in a silica host medium was observed. The quantum yield of the photoluminescence increased when the size of the nanoparticles was decreased. The quantum yield for 8 nm silver nanoparticle was estimated to be on the order of ${10}^{\ensuremath{-}2}$ which is ${10}^{8}$ times higher than the one observed for bulk silver. The two photoluminescence bands observed from silver nanoparticles were rationalized as the radiative electron interband transitions and radiative decay of the surface plasmons in silver nanoparticles. The strong local electric field induced by the surface-plasmon resonance in silver nanoparticles enhances the exciting and emitted photons and increases the quantum yield of the photoluminescence.

Photoluminescence from Silver Nanoparticles Enhanced by Surface Plasmon Resonance

AbstractThe size dependence of the photoluminescence spectra from silver nanoparticles embedded in a silica host medium was observed. The quantum yield of the photoluminescence increased when the size of the nanoparticles was decreased. The quantum yield for 8 nm silver nanoparticle was estimated to be on the order of 10-2 which is 108 times higher than the one observed for bulk silver. The two photoluminescence bands observed from silver nanoparticles were rationalized as the radiative electron interband transitions and radiative decay of the surface plasmons in silver nanoparticles. The strong local electric field induced by the surface plasmon resonance in silver nanoparticles enhances the exciting and emitted photons and increases the quantum yield of the photoluminescence.

Raman scattering of L‐tryptophan enhanced by surface plasmon of silver nanoparticles: vibrational assignment and structural determination

AbstractVibrational bands of L‐tryptophan which was adsorbed on Ag nanoparticles (∼10 nm in diameter) have been investigated in the spectral range of 200–1700 cm−1 using surface‐enhanced Raman scattering (SERS) spectroscopy. Compared with the normal Raman scattering (NRS) of L‐tryptophan in either 0.5 M aqueous solution (NRS‐AS) or solid powder (NRS‐SP), the intensified signals by SERS have made the SERS investigation at a lower molecular concentration (5 × 10−4 M) possible. Ab initio calculations at the B3LYP/6‐311G level have been carried out to predict the optimal structure and vibrational wavenumbers for the zwitterionic form of L‐tryptophan. Facilitated with the theoretical prediction, the observed vibrational modes of L‐tryptophan in the NRS‐AS, NRS‐SP, and SERS spectra have been analyzed. In the spectroscopic observations, there are no significant changes for the vibrational bands of the indole ring in either NRS‐AS, NRS‐SP, or SERS. In contrast, spectral intensities involving the vibrations of carboxylate and amino groups are weak in NRS‐AS and NRS‐SP, but strong in SERS. The intensity enhancement in the SERS spectrum can reach 103–104‐fold magnification. On the basis of spectroscopic analysis, the carboxylate and amino groups of L‐tryptophan are determined to be the preferential terminal groups to attach onto the surfaces of Ag nanoparticles in the SERS measurement. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles inmetal–dielectric nanocomposites

We report the preparation of a new type of nanocomposite containing cobalt and silvernanoparticles organized in parallel layers with a well controlled separation. Thisarrangement allows the observation of an enhanced low-frequency Raman signal at thevibration frequency of cobalt nanoparticles excited through the surface plasmons of silvernanoparticles. Numerical simulations of the electric field confirm the emergence of hot spotswhen the separation between silver and cobalt nanoparticles is small enough.

Self-assembly of λ-DNA networks/Ag nanoparticles: Hybrid architecture and active-SERS substrate

In this article, highly rough and stable surface enhanced Raman scattering (SERS)-active substrates had been fabricated by a facile layer-by-layer technique. Unique λ-DNA networks and CTAB capped silver nanoparticles (AgNP) were alternatively self-assembled on the charged mica surface until a desirable number of bilayers were reached. The as-prepared hybrid architectures were characterized by UV–vis spectroscopy, tapping mode atomic force microscopy (AFM) and confocal Raman microscopy, respectively. Linear increases of the maximum absorbance of DNA band with the number of bilayers present a common LBL assembly feature. The red-shift of surface plasmon of silver nanoparticles within the hybrid films was mainly due to the aggregation effect. With the increase of number of bilayers, the surface coverage of nanoparticles on the substrate became larger, as well as the rising of total amount of nanoparticles and the surface roughness of hybrid films. These rough metallic hybrid architectures could be utilized as SERS-active substrates. A significant enhanced Raman scattering effect of the adsorbed analytes, e.g., methylene blue (MB), on these hybrid films was easily exploited by the confocal Raman microscopy. The enhancement factor depended on the surface coverage of nanoparticles and number of bilayers of λ-DNA/AgNP.

Enhanced Scattering of Random-Distribution Nanoparticles and Evanescent Field in Super-Resolution Near-Field Structure

This study focuses on evanescent fields induced by silver nanoparticles in the mask layer and in the interfaces in an AgOx-type super-resolution near-field structure (super-RENS). The finite-difference time-domain (FDTD) method is used to analyze the scattering fields from the localized surface plasmons of silver nanoparticles. It has been found that the spatial extension of the evanescent field is very short along the thickness direction of the layers, and the 3-dimensional coupling patterns of the evanescent fields from the individual particles are irregular. The study also found that the intensity of the evanescent fields is dependent on the silver concentration.

Photoelectron emission caused by surface plasmons in silver nanoparticles

A new intense band of photoelectron emission peaked at a wavelength of 490 nm has been observed in granular silver films with a nanoparticle size of 10–50 nm. Coinciding with an optical reflection band, the new photoelectron emission peak is related to the excitation of surface plasmons in silver nanoparticles. The quantum yield of photoemission (0.25%) for the new band is approximately equal to that for a longwave band of the classical silver-oxygen-cesium photocathode. It is demonstrated that the photoelectron emission from both photoemitters has a common nature and a time constant on the order of several femtoseconds can be obtained.