Localized Surface Plasmon Resonance Behavior Research Articles

Polarization Anisotropy of Multiple Localized Plasmon Resonance Modes in Noble Metal Nanocrescents

Multiple localized surface plasmon resonance (LSPR) modes induced in gold and silver nanocrescents exhibit anisotropic behavior with respect to polarization of incident light. Extinction spectroscopy with polarization control was used to characterize the optical properties of asymmetric nanocrescents with diameters ranging from 100 to 500 nm. The analysis shows that selective induction of distinct dipole and quadrupole LSPR modes can be accomplished through polarization of incident light. Finite-difference time-domain calculations of the LSPR responses of the nanocrescent corroborate the polarization-dependent optical behavior. Simulations reveal optical near field enhancements with unique spatial patterns associated with the individual resonance modes depending on the polarization and wavelength of incident light. Quantitative analysis of the anisotropic LSPR behavior supports the potential for controlling the near field through selective induction of specific resonance modes with particular near field d...

Slab Thickness Dependence of Localized Surface Plasmon Resonance Behavior in Gold Nanorings

We present detailed experimental and numerical studies of plasmonic properties of gold nanoring (NR) arrays with different slab thicknesses from 15 to 125 nm. The hybrid plasmon resonances for the bonding and antibonding modes in gold NRs exhibit a high slab thickness dependence behavior in optical properties. For the thinner slab thickness below 50 nm, both hybrid modes show large spectral tunabilities by varying the slab thickness. Furthermore, for such hollow NR structure, the enhancements of electric field intensities at the inner and outer ring surfaces when reducing the slab thickness are investigated. We observe a significant transition of field distributions for the antibonding mode. All these features can be understood by surface charge distributions from our simulations. The results of this study offer a potential strategy to design a composite plasmonic nanostructure with large field enhancement for numerous applications.

Sandwich-like Cu1.94S–ZnS–Cu1.94S nanoheterostructure: structure, formation mechanism and localized surface plasmon resonance behavior

In this communication, a thermolysis route is developed to synthesize novel Cu1.94S–ZnS–Cu1.94S nanoheterostructures with interesting sandwich-like architectures, taking Cu1.94S nanoplates as precursors. Evidently, the trimeric nanostructure is formed by a three-stage process, which includes the Zn-oleate induced assembling of Cu1.94S nanoplate couples, the heteronucleation and growth of a ZnS layer between two Cu1.94S plates dominated by interfacial diffusion, and the catalyst assisted axial growth of ZnS nanorod following the solution–liquid–solid mechanism. With epitaxial growth of ZnS nanocrystal between two Cu1.94S nanoplates, the localized surface plasmon resonance frequency of Cu1.94S shifts from 1875 to 1323 nm, indicating that this new material is potentially applicable as a light absorbing agent in laser photothermal therapy. The reported growth mechanism may provide new strategies for designing and fabricating various technologically important polymeric nanoheterostructures.

Correlating SAXS analysis with LSPR behavior: poly(vinyl alcohol)-stabilized Ag nanoparticles

We explore the localized surface plasmon resonance (LSPR) behavior of aqueous sols of PVA-stabilized AgNPs synthesized in presence of glucose as a reducing agent. The in situ synthesis parameters are tuned by adding increasing amounts of NaOH, which causes interesting variations in pH, LSPR curve broadening, and the evolution of AgNPs embedded PVA cross-linked nanostructures. Small angle X-ray scattering (SAXS) analysis is used to investigate sol aggregate characteristics. In all samples, mass fractal aggregates of two radius of gyration are formed. Assuming spherical form, the SAXS nanoparticle size distribution predicts a range from 6 to 60 nm. However, only the fractal aggregate features closely correspond to the observed LSPR characteristics.

银包覆PMMA纳米核壳颗粒的局域表面等离激元共振行为的模拟计算

Localized surface plasmon resonance (LSPR) spectrum behaviors of PMMA/Ag core-shell nanoparticles are extensively and systematically simulated by a calculation method based on Mie theory. Through the simulation calculation, the dependence of the LSPR behaviors of the core-shell nanoparticle on nanoparticle size, ratio of the radius of PMMA core to the thickness of Ag shell, and some other factors is studied. Furthermore, LSPR behaviors of Ag nanoparticles are simulated as well for comparison. The simulation results show that the nanosized PMMA dielectric core can weaken the retardation effects in the process of free electron resonance in the Ag nanoshell. Thus, compared with the LSPR of Ag nanoparticles, the position of the LSPR peak of the PMMA/Ag core-shell nanoparticles has an even more obvious red shift and the width of the LSPR becomes even narrower. Such simulation results indicate that the core-shell nanoparticles would have more advantages over Ag nanoparticles for potential applications of future chemical and biological nanosensors.

Characterizing the localized surface plasmon resonance behaviors of Au nanorings and tracking their diffusion in bio-tissue with optical coherence tomography

The characterization results of the localized surface plasmon resonance (LSPR) of Au nanorings (NRs) with optical coherence tomography (OCT) are first demonstrated. Then, the diffusion behaviors of Au NRs in mouse liver samples tracked with OCT are shown. For such research, aqueous solutions of Au NRs with two different localized surface plasmon resonance (LSPR) wavelengths are prepared and characterized. Their LSPR-induced extinction cross sections at 1310 nm are estimated with OCT scanning of solution droplets on coverslip to show reasonably consistent results with the data at individual LSPR wavelengths and at 1310 nm obtained from transmission measurements of Au NR solutions and numerical simulations. The resonant and non-resonant Au NRs are delivered into mouse liver samples for tracking Au NR diffusion in the samples through continuous OCT scanning for one hour. With resonant Au NRs, the average A-mode scan profiles of OCT scanning at different delay times clearly demonstrate the extension of strong backscattering depth with time. The calculation of speckle variance among successive OCT scanning images, which is related to the local transport speed of Au NRs, leads to the illustrations of downward propagation and spreading of major Au NR motion spot with time.

Synthesis of gelatin-capped gold nanoparticles with variable gelatin concentration

Gelatin-stabilized gold nanoparticles (AuNPs-gelatin) with controlled particle size were synthesized with simple variation of concentration of gelatin by reducing in situ tetrachloroauric acid with sodium citrate. The nanoparticles showed excellent colloidal stability. Transmission electron microscopy (TEM) revealed the formation of well-dispersed gold nanoparticles (AuNPs) with different sizes. The methodology produces particles 10–15 nm in size depending on the concentration of gelatin used. The measured AuNPs are 10, 11, 12, 13, 14, and 15 nm for AuNPs-gelatin 1, 0.5, 0.25, 0.1 and 0.05%, and pure AuNPs, respectively. The AuNPs-gelatin exhibit size-dependent localized surface plasmon resonance behavior as measured by UV–visible spectroscopy. UV–vis spectroscopy and TEM results suggest that higher concentration of gelatin favor smaller particle size and vice versa. FTIR spectroscopy analysis of AuNPs-gelatin revealed the amino bands and carboxyl peak of gelatin. The crystalline nature of AuNPs was investigated by X-ray diffraction.