Interaction Of Metal Nanoparticles Research Articles

Plasmonic-based instrument response function for time-resolved fluorescence: toward proper lifetime analysis

In this report, we investigated the so-called plasmonic platforms prepared to target ultra-short fluorescence and accurate instrumental response function in a time-domain spectroscopy and microscopy. The interaction of metallic nanoparticles with nearby fluorophores results in the increase of the dye fluorescence quantum yield, photostability and decrease of the lifetime parameter. The mentioned properties of platforms were applied to achieve a picosecond fluorescence lifetime (21 ps) of erythrosin B, used later as a better choice for deconvolution of fluorescence decays measured with “color” sensitive photo-detectors. The ultra-short fluorescence standard based on combination of thin layers of silver film, silver colloidal nanoparticles (about 60 nm in diameter), and top layer of erythrosin B embedded in 0.2 % poly(vinyl) alcohol. The response functions were monitored on two photo-detectors; microchannel plate photomultiplier and single photon avalanche photodiode as a Rayleigh scattering and ultra-short fluorescence. We demonstrated that use of the plasmonic base fluorescence standard as an instrumental response function results in the absence of systematic error in lifetime measurements and analysis.

Giant optical activity from the radiative electromagnetic interactions in plasmonic nanoantennas

We fabricate the linear chains of twisted gold nanorods by a facile chiral molecular templating method. In such a chiral plasmonic system, particle-particle separation distances are in the order of the light wavelength and are much larger than the sizes of individual particles. As a result, the inter-particle interactions in this chiral system are mediated mainly by a relatively weak far-field plasmonic coupling, rather than a strong near-field coupling. However, such a chiral system of twisted gold nanorods show a huge surface plasmon based circular dichroism response, with the highest anisotropy factor around 0.027. This is in contrast to the previous studies in which near-field plasmonic coupling is an indispensable prerequisite to obtain strong optical activity from a chiral plasmonic nanostructure. Our study demonstrates here an alternative strategy for achieving huge chiroptical response of a chiral plasmonic nanostructure based on far-field, radiative electromagnetic interactions of metallic nanoparticles. Theoretical simulations show a satisfactory agreement with the experimental results. This study may provide more flexible ways to design chiral plasmon nanostructures with strong CD responses for various applications.

Optical Property Characterization of Novel Graphene‐X (X=Ag, Au and Cu) Nanoparticle Hybrids

The present investigation reports new results on optical properties of graphene‐metal nanocomposites. These composites were prepared by a solution‐based chemical approach. Graphene has been prepared by thermal reduction of graphene oxide (GO) at 90°C by hydrazine hydrate in an ammoniacal medium. This ammoniacal solution acts as a solvent as well as a basic medium where agglomeration of graphene can be prevented. This graphene solution has further been used for functionalization with Ag, Au, and Cu nanoparticles (NPs). The samples were characterized by X‐ray diffraction (XRD), Raman spectroscopy, UV‐Vis spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to reveal the nature and type of interaction of metal nanoparticles with graphene. The results indicate distinct shift of graphene bands both in Raman and UV‐Vis spectroscopies due to the presence of the metal nanoparticles. Raman spectroscopic analysis indicates blue shift of D and G bands in Raman spectra of graphene due to the presence of metal nanoparticles except for the G band of Cu‐G, which undergoes red shift, reflecting the charge transfer interaction between graphene sheets and metal nanoparticles. UV‐Vis spectroscopic analysis also indicates blue shift of graphene absorption peak in the hybrids. The plasmon peak position undergoes blue shift in Ag‐G, whereas red shift is observed in Au‐G and Cu‐G.

Interaction of metallic nanoparticles with dielectric substrates: effect of optical constants

In this paper, we study the local-field enhancement in a system of a metallic nanoparticle placed very near to a dielectric substrate. In such systems, intense electric fields are localized in the gap between the particle and the substrate, creating a ‘hot-spot’ under appropriate excitation conditions. We use finite-element numerical simulations in order to study the field enhancement in this dielectric–metal system. More specifically, we show how the optical properties of the dielectric substrate (n and k) affect the plasmonic field enhancement in the nano-gap. We also analyze the degree of field confinement in the gap and discuss it in the context of utilization for surface-enhanced Raman scattering. We finally show the fields generated by real substrates and compare them to metallic ones.

Chiral Nanoparticles: Chirality of Metal Nanoparticles in Chiral Mesoporous Silica (Adv. Funct. Mater. 18/2012)

The chiroptical properties of pure inorganic material are reported by Shunai Che and co-workers on page 3784. The properties are investigated by dispersing achiral metal nanoparticles into chiral mesoporous silica, due to collectively asymmetric plasmon interactions of metal nanoparticles arranged along a helical pore orientation. Such chiral materials will have novel applications for biosensing, chiral recognition, and detection, based on the importance of surface plasmon resonance (SPR) in biological structures.

A discrete interaction model/quantum mechanical method to describe the interaction of metal nanoparticles and molecular absorption

A frequency-dependent quantum mechanics/molecular mechanics method for the calculation of response properties of molecules adsorbed on metal nanoparticles is presented. This discrete interaction model/quantum mechanics (DIM/QM) method represents the nanoparticle atomistically, thus accounting for the local environment of the nanoparticle surface on the optical properties of the adsorbed molecule. Using the DIM/QM method, we investigate the coupling between the absorption of a silver nanoparticle and of a substituted naphthoquinone. This system is chosen since it shows strong coupling due to a molecular absorption peak that overlaps with the plasmon excitation in the metal nanoparticle. We show that there is a strong dependence not only on the distance of the molecule from the metal nanoparticle but also on its orientation relative to the nanoparticle. We find that when the transition dipole moment of an excitation is oriented towards the nanoparticle there is a significant increase in the molecular absorption as a result of coupling to the metal nanoparticle. In contrast, we find that the molecular absorption is decreased when the transition dipole moment is oriented parallel to the metal nanoparticle. The coupling between the molecule and the metal nanoparticle is found to be surprisingly long range and important on a length scale comparable to the size of the metal nanoparticle. A simple analytical model that describes the molecule and the metal nanoparticle as two interacting point objects is found to be in excellent agreement with the full DIM/QM calculations over the entire range studied. The results presented here are important for understanding plasmon-exciton hybridization, plasmon enhanced photochemistry, and single-molecule surface-enhanced Raman scattering.

Density matrix based microscopic theory of molecule metal–nanoparticle interactions: Linear absorbance and plasmon enhancement of intermolecular excitation energy transfer

A microscopic theory of interacting molecule metal-nanoparticle (MNP) systems is presented and used to compute absorption spectra and the plasmon enhancement of intermolecular excitation energy transfer (EET). The approach is based on a nonperturbative consideration of the Coulomb coupling matrix elements responsible for EET between the molecules and the MNP. In this way, the need to determine the local fields induced by surface plasmon excitations of the MNP is removed, but the whole description is restricted to distances among the interacting species less than the wavelength of absorbed photons. Based on a density matrix theory, the approach accounts for the vibrational level structure of the molecules, intramolecular vibrational energy redistribution (IVR), and plasmon damping. Numerical results for linear absorbance spectra and EET dynamics are offered. In this respect the importance of energy dissipation in the MNP due to rapid surface plasmon decay is emphasized.

Optical properties of metallic nanoparticles: manipulating light, heat and forces at the nanoscale

We present to a general readership an overview of the rich variety of phenomena and applications that arise from the interaction of metallic nanoparticles with light. First, we present the fundamental physics of localized surface plasmon resonances, the most relevant theories and numerical methods, as well as optical detection schemes. Finally, we explain how the localized surface plasmon resonances are currently exploited for the nanoscale manipulation of light, heat and forces in various applications and experimental investigations.

Plasmon enhanced direct and inverse Faraday effects in non-magnetic nanocomposites

While applications of plasmonics are rapidly growing, magneto-optical effects in nanocomposites are poorly understood. We therefore devote this paper to the theoretical analysis of magneto-optical effects in nanocomposites. Based on the Drude model, we derived the constitutive equation where the dielectric and coupling functions describe the interactions of metal nanoparticles with magnetic field. In the limitation of low volume fraction of metal nanoparticles (i.e., when the material is still transparent), these functions were calculated within the Maxwell–Rayleigh theory of dilute suspensions. We showed that in the absence of external magnetic fields, a non-magnetic nanoparticle can be magnetized in the circularly polarized light beam, and the magnetization depends on the direction of rotation of the light wave. The external magnetic field alters the particle magnetization, and when the fields are weak, this change in magnetization linearly depends on the particular field. The proposed theory was applied to an analysis of the Faraday effect in nanocomposites. We predicted a resonance behavior of the Verdet function in nanocomposites and its dependence on concentration, sample thickness, and external magnetic field.

Probing the acoustic vibrations of single metal nanoparticles by ultrashort laser pulses

AbstractThe strong interaction of metal nanoparticles with light makes it possible to detect individual particles by far‐field optical methods. In this article, the interaction of a metal nanoparticle with a short laser pulse is discussed, with the emphasis on the coherent excitation of mechanical (acoustic) modes and the optical detection of these vibrations. The literature on acoustic vibrations of single metal nanoparticles of different shapes (spheres, dumbbells, rods, cubes, wires, prisms) is reviewed, and the modes that have been excited and detected in these particles are discussed. Finally, the insights and potential applications enabled by these studies are summarized.

Advanced microwave-assisted production of hybrid electrodes for energy applications

Carbon nanotubes are one of the most prominent materials in research for creating electrodes for portable electronics. When coupled with metallic nanoparticles the performance of carbon nanotube electrodes can be dramatically improved. Microwave reduction is an extremely rapid method for producing carbon nanotube-metallic nanoparticle composites, however, this technique has so far been limited to carbon nanotube soot. An understanding of the microwave process and the interactions of metallic nanoparticles with carbon nanotubes have allowed us to extend this promising functionalisation route to pre-formed CNT electrode architectures. Nanoparticle reduction onto pre-formed architectures reduces metallic nanoparticle waste as particles are not formed where there is insufficient porosity for electrochemical processes. A two-fold increase in capacitive response, stable over 500 cycles, was observed for these composites, with a maximum capacitance of 300 F g−1 observed for a carbon Nanoweb electrode.

Effect of metal nanoparticles on the optical properties of the solutions of porphyrinates and MEH-PPV polymer

The interactions of metal nanoparticles, which were synthesized in inverse micelles, with a number of porphyrinate molecules and a poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) polymer in solutions were examined by spectrophotometry in order to study the effects of various additives on the efficiency of sun energy absorption and conversion by photosensitive polymer layers. The optical absorption and luminescence spectra of the solutions of Ag, Pd, and Pt nanoparticles and the solutions of Pd(II) and Pt(II) meso-tetra(benzo-15-crown-5)porphyrinates and the MEH-PPV polymer were measured previously.

Regulation of Interparticle Interaction of Metallic Nanoparticles and Formation of Particle Super Lattice(<Special Issue>Crystallization and Structure Formation of Nano-Submicron Particles)

Regulation of Interparticle Interaction of Metallic Nanoparticles and Formation of Particle Super Lattice(<Special Issue>Crystallization and Structure Formation of Nano-Submicron Particles)

Interaction of Metallic Nanoparticles with a Biologically Active Molecule, Dopamine

We present the results of first-principles molecular orbital calculations describing the interaction of metallic nanoparticles, represented by Mn(13), Ag(13), and Al(13) atomic clusters, with a biologically active molecule, dopamine. The interaction strength, determined in terms of the nanoparticle-molecule complex binding energy, is found to be higher for Mn than either Ag or Al and can be explained in terms of the degree of the hybridization of the (metal) atomic orbitals with the molecular orbitals in the complex. Furthermore, smaller interaction strength of these metallic nanoparticles with water compared to that with dopamine predicts the preference of forming a complex of dopamine with the metallic nanoparticles in the aqueous solution. The calculated results may therefore suggest that the presence of these metallic nanoparticles could induce different levels of dopamine depletion in solution.

Study on the Doping and Interactions of Metal Nanoparticles in the Lyotropic Liquid Crystals

Abstract The hydrophilic silver and hydrophobic gold nanoparticles are doped simultaneously or separately into different regions of a lyotropic liquid crystal (LLC) with long-range structural order built with the AOT/isooctane/ water ternary system. A stable lamellar hybrid is produced under suitable conditions. Polarized optical microscopy (POM) and small angle X-ray scattering (SAXS) are used to compare the phase changes upon various doping manners. The interactions between doped particles and surfactant bilayers are analyzed and compared in detail. Factors affecting the stability of inorganic/organic hybrids are also discussed. The doped hydrophobic particles affect the equilibrium of van der Waals and Helfrich interactions between them and the membranes. When hydrophilic particles are incorporated into LLC aqueous region, electrostatic force will be dominant. The results suggest that it is the balance of electrostatic, van der Waals, and Helfrich forces in the lyotropic liquid crystal that determines the hybrid structure.

Interaction of silver nanoparticles with HIV-1

The interaction of nanoparticles with biomolecules and microorganisms is an expanding field of research. Within this field, an area that has been largely unexplored is the interaction of metal nanoparticles with viruses. In this work, we demonstrate that silver nanoparticles undergo a size-dependent interaction with HIV-1, with nanoparticles exclusively in the range of 1–10 nm attached to the virus. The regular spatial arrangement of the attached nanoparticles, the center-to-center distance between nanoparticles, and the fact that the exposed sulfur-bearing residues of the glycoprotein knobs would be attractive sites for nanoparticle interaction suggest that silver nanoparticles interact with the HIV-1 virus via preferential binding to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the virus from binding to host cells, as demonstrated in vitro.

Casimir Forces Between Nanoparticles and Substrates

ABSTRACTWe study the Casimir force between a nanoparticle and a substrate using a spectral representation formalism. We consider the interaction of metal nanoparticles with different substrates within the dipolar approximation. The force is calculated as a function of the distance between the particles and the substrate. The particles are made of gold or potassium spheres, and the substrate is titanium dioxide, sapphire or a perfect conductor.

Interaction of metal nanoparticles with a semiconductor in surface-doped gas sensors

A capacitance response of semiconductor sensors fabricated on the basis of thin NiO and SnO2 films with noble-metal nanoparticles deposited on their surface was analyzed. This response was shown to appear due to the solid-phase metal-semiconductor reaction accompanied by the formation of a boundary layer with a fairly high density of surface electron states in its band gap. The chemisorption field effect (the change in work function of the metal after inlet of gases) observed in the capacitance gas sensors not only forms the basis for the sensitive and prompt method of analysis but also represents the basic functional phenomenon responsible for their capacitance response.