Plasmon Resonance of Finite One-Dimensional Au Nanoparticle Chains (original) (raw)
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Linear optical properties of a linear chain of interacting gold nanoparticles
Canadian Journal of Physics
In a Drude-like model for the conduction electrons of metal nanoparticles (MNPs) in a periodic linear chain, considering dipole-dipole interactions of adjacent particles, an analytical expression is derived for each particle permittivity for two different polarizations of incident light: parallel with and perpendicular to the chain line. A numerical analysis is carried out for a chain including 10 identical gold nanoparticles (NPs) for two different sizes of NPs and two different host media: air and glass. It is shown that in the parallel case of polarization, interaction of NPs leads to a substantial increase in the extinction cross section and the redshift of the surface plasmon resonance (SPR) wavelength. In comparison with the linear properties of a single NP, the second and penultimate particles have the most increase in the extinction cross section and SPR wavelength displacement while the first and last particles experience the least variations due to the mutual interactions....
Plasmonic Resonances of Closely Coupled Gold Nanosphere Chains
The Journal of Physical Chemistry C, 2009
The optical properties of an ordered array of gold nanospheres have been calculated using the T-matrix method in the regime where the near-fields of the particles are strongly coupled. The array consists of a one-dimensional chain of spheres of 15 nm diameter where the number of spheres in the chain and interparticle spacing is varied. Calculations have been performed with chains up to 150 particles in length and with an interparticle spacing between 0.5 and 30 nm. Incident light polarized along the axis of the chain (longitudinal) and perpendicular (transverse) to it are considered, and in the latter case for wavevectors along and perpendicular to the chain axis. For fixed chain length the longitudinal plasmon resonance red shifts, relative to the resonance of an isolated sphere, as the interparticle spacing is reduced. The shift in the plasmon resonance does not appear to follow an exponential dependence upon gap size for these extended arrays of particles. The peak shift is inversely proportional to the distance, a result that is consistent with the van der Waals attraction between two spheres at short range, which also varies as 1/d. The transverse plasmon resonance shifts in the opposite direction as the interparticle gap is reduced; this shift is considerably smaller and approaches 500 nm as the gap tends to zero. Increasing the number of particles in the chain for a fixed gap has a similar effect on the longitudinal and transverse plasmon. In this case, however, the longitudinal plasmon tends toward an asymptotic value with increasing chain length, with the asymptotic value determined by the interparticle spacing. Here, the approach to the asymptote is exponential with a characteristic length of approximately two particles, at small interparticle spacings. This approach to an asymptote as the chain length becomes infinite has been verified in a finite element calculation with periodic boundary conditions.
Nonradiative limitations to plasmon propagation in chains of metallic nanoparticles
Physical Review B
We investigate the collective plasmonic modes in a chain of metallic nanoparticles that are coupled by nearfield interactions. The size-and momentum-dependent nonradiative Landau damping and radiative decay rates are calculated analytically within an open quantum system approach. These decay rates determine the excitation propagation along the chain. In particular, the behavior of the radiative decay rate as a function of the plasmon wavelength leads to a transition from an exponential decay of the collective excitation for short distances to an algebraic decay for large distances. Importantly, we show that the exponential decay is of a purely nonradiative origin. Our transparent model enables us to provide analytical expressions for the polarization-dependent plasmon excitation profile along the chain and for the associated propagation length. Our theoretical analysis constitutes an important step in the quest for the optimal conditions for plasmonic propagation in nanoparticle chains.
The Journal of Physical Chemistry Letters, 2013
We investigated the near-and far-field response of 1D chains of Au nanoparticles (NPs) fabricated with high structural control through template guided self-assembly. We demonstrate that the density of poly(ethylene glycol) ligands grafted onto the NP surface, in combination with the buffer conditions, facilitate a systematic variation of the average gap width (g) at short separations of g < 1.1 nm. The overall size (n) of the individual clusters was controlled through the template. The ability to independently vary n and g allowed for a rational tuning of the spectral response in individual NP clusters over a broad spectral range. We used this structural control for a systematic investigation of the electromagnetic coupling underlying the superradiant cluster mode. Independent of the chain length, plasmon coupling is dominated by direct neighbor interactions. A decrease in coupling strength at separations ≲0.5 nm indicates the presence of nonlocal or quantum-mechanical coupling mechanisms. Figure 4. (a) HRTEM pictures of 1D clusters formed from NP NC in T40 buffer; scale bar represents 50 nm. (b) Cumulative probability plots for the interparticle gap distributions obtained under three different experimental conditions as defined in the legend.
The Journal of Physical Chemistry C, 2012
The plasmonic properties of single Au triangular nanoprisms are investigated using photoemission electron microscopy with particular emphasis on polarization dependence. Two localized surface plasmon resonances (LSPRs) are studied, namely, the in-plane dipolar and quadrupolar plasmon excitations. Experimental maps of the near-field spatial distribution upon polarization and wavelength of the exciting field are interpreted in the framework of a group theory description and finite difference time domain simulations. This work demonstrates the selective excitations, by lifting of degeneracy, of the different LSPR eigenmodes at the single object level and opens ways for the active control of the angular radiation patterns of optical nanoantennas. This approach is general and applies to any nano-object, whatever its initial shape symmetry.
Optical response of metal nanoparticle chains
Optics Communications, 2006
We study the optical responses of metal nanoparticle chains. Multiple scattering calculations are used to study the extinction cross sections of silver nanosphere chains of finite length embedded in a glass matrix. The transmission and reflection coefficients of periodic 2D arrays of silver nanospheres are also calculated to understand the interaction between nanoparticle chains. The results are in agreement with recent experiments. The splitting of plasmon-resonance modes for different polarizations of the incident light are explored. Results on the effect of disorder are also presented.
Synthesis and Formation of One-Dimensional Au Nanoparticle Chains
e-Journal of Surface Science and Nanotechnology, 2009
Structures on the nanoscale have become increasingly prevalent in optoelectronics research in recent years. In particular low dimensional metallic structures have generated interest due to their unique plasmonic properties. We report the synthesis of gold nanoparticles in aqueous solution and the subsequent arrangement of these particles into nanowires-type structures using the dipole-dipole attractive properties of the particles. These nanowire-type structures have differing surface plasmonic properties in comparison to the 0-dimensional nanoparticles due to the 1-dimensional propagation of the plasmon signals. A number of methods were examined for the dipole-dipole interactions to be initiated. Under low pH conditions (~pH 3) the stabilisers become detached causing a reversible aggregation of the nanoparticles. Through careful tuning of the solution pH it was examined as to whether only partial removal of the stabilisers was possible with a view to inducing linear aggregation. A second method examined was the removal of the nanoparticles from the aqueous solution and their subsequent dispersal in ethanol. The polar nature of water is seen to interfere with the dipole-dipole interaction once the stabilizers have been removed. Using a less polar solvent was examined, again with regards to initiating nanowire growth.
Parallel Collective Resonances in Arrays of Gold Nanorods
Nano Letters, 2014
In this work we discuss the excitation of parallel collective resonances in arrays of gold nanoparticles. Parallel collective resonances result from the coupling of the nanoparticles localized surface plasmons with diffraction orders travelling in the direction parallel to the polarization vector. While they provide field enhancement and delocalization as the standard collective resonances, our results suggest that parallel resonances could exhibit greater tolerance to index asymmetry in the environment surrounding the arrays. The near-and far-field properties of these resonances are analyzed, both experimental and numerically. KEYWORDS. Surface plasmons, nanoparticles, collective resonances, near-field optical microscopy (SNOM), near-field patterns, Rayleigh anomalies. Metallic nanoparticles exhibit remarkable optical properties associated with the excitation of localized surface plasmon resonances (LSPRs), which enable an ever increasing number of applications related to enhanced and more confined light-matter interaction, control of emission and sensing. 1 Furthermore, these properties can be modified and promoted by adjusting the interaction between nanoparticles. So, near-field interactions between very close nanoparticles shift the resonance position anisotropically, 2 induce an even stronger field enhancement between the nanoparticles, 3 and improve sensing capabilities. 4 Complex nanoclusters can generate collective modes of different nature, which provide a further control of the spectral response through Fano resonances. 5,6 In recent years, interactions between nanostructures in arrays mediated by diffraction orders have also received an increasing amount of attention. 7-20 At wavelengths close to a Rayleigh anomaly (RA), which corresponds to the transition from an evanescent to a propagative diffraction order in an array, the nanoparticles LSPRs can couple with these diffracted waves and give rise to the so called collective, lattice or geometric resonances. 14,15 Collective resonances induce several differences between the extinction spectrum of an array and that of an isolated nanostructure, such as a shift of the main extinction peak, the presence of a dip, and, more interestingly, the appearance of a supplementary extinction peak with an asymmetric shape and a potential high quality factor. 9,12,15 Moreover, the collective resonance is concomitant with an increase of the plasmonic enhancement of the near-field, as well as its delocalization. 18,21-23 These far-and near-field properties make geometric resonances of great interest for several applications such as sensing, 24-27 enhanced surface Raman scattering (SERS), 28 or enhancement and control of spontaneous 29-34 and stimulated 35 emission.