Narrow Results

Periodic hexagonal gold crystal spherical nanoparticle arrays with controllable size and periodicity are fabricated by physical vapor deposition and further heat treatment based on monolayer colloidal crystal template. The size and center-to-center spacing of nanoparticles (NPs) were manipulated conveniently by tuning the deposition thickness of Au film and the size of colloidal spheres of the template, respectively. The thickness range of deposited Au film dependent on the size of colloidal spheres was investigated comprehensively. Dewetting model was established and employed to analyze the whole process of the evolution from gold film to spherical nanoparticle with uniform size. Additionally, localized surface plasmon resonance (LSPR) responses of these Au nanoparticle arrays were systematically measured. It is found that the extinction properties are significantly influenced by the particle size and periodicity of arrays. With the increase of particle size, the LSPR peak shows a red shift due to the quantum size effect of the nanoscaled Au particle. Meanwhile, the diffraction peaks also show small red shift due to a slight increase of average refractive index of arrays. This is highly helpful to improve its practical applications for detecting biochemical molecules based on LSPR and diffraction peak sensing.

In this paper, we studied the surface morphology of silver (Ag) thin films deposited on glass substrate by using the DC magnetron sputtering with various power conditions at room temperature. The surface morphology, the optical and electrical properties were measured by AFM (Atomic Force Microscopy), UV–Vis Spectrophotometer (Lambda 950), and the four-probe method (RTS-9, Four Probes Technology). The effect of the sputtering power on the root-mean-square (RMS) surface roughness of Ag thin films was analyzed. The experiment results showed that the RMS value was lowest in the range from 60W to 80W. At the same time, the effect of the thickness on optical transmittance and sheet resistance was also investigated. We found the rough surface was prejudiced to inducing sheet resistance and enhancing the optical transmittance when the thickness of Ag thin films was thin. In addition, the excitation of the localized surface plasmon resonance (LSPR) was due to Ag nanoparticles (NPs) based on the analysis of the FDTD (finite-difference time-domain) simulation.

In this paper, a systematic spectroscopic analysis on silver–polyvinyl alcohol (Ag/PVA) nanocomposite thin films is reported. Ag/PVA nanocomposite thin films fabricated by thermal annealing process are shown to exhibit a strong localized surface plasmon resonance (LSPR) at wavelength around 400 nm. The effects of different fabricating parameters on the absorbance and spectral position of LSPR are also investigated. The particle sizes calculated from Mie light scattering theory are found to agree with the values obtained from SEM characterization.

Metal nanostructures and noble metal-based nanostructures, in particular, exhibit plasmonic resonance in the visible region. The resonance absorption can be tuned by varying the size of nanoparticle and the external matrix in which the plasmonic materials are embedded. Mie’s theory has been used to demonstrate the shift in the plasmonic resonance in gold nanoparticles embedded in different dielectric media. Two model systems, viz. Au–ZnO and Au–Al₂O₃, prepared by sputtering on quartz substrates were used to study the optical absorption. The plasmonic peaks were observed to be red shifted in Au–Al₂O₃ and Au–ZnO, as is also supported by Mie formalism. The dielectric constant of the external matrix viz., Al₂O₃ and ZnO, estimated using the experimental and the Mie simulations are 3.05 and 1.83, respectively.

In this paper, localized surface plasmon resonance (LSPR) of periodic two-dimensional (2D) gold nanoparticles arrays is investigated using far field polarization spectroscopy. Square and rectangular arrays of 60 nm gold nanoparticles with different interparticle spacings are fabricated with electron beam lithography (EBL). The experimental extinction cross section spectra are revealed the existence of two plasmon modes depending to the polarization direction of the incident radiation on the sample. The extinction spectra are calculated using coupled dipole approximation (CDA). Good qualitative and quantitative agreement is obtained between calculations and experimental results. Moreover, it is found that the interparticle spacing on the array was the key parameter to study the plasmon interaction between the nanoparticles and to determine the amplitude, spectral position and width of LSPR band.

The localized surface plasmon resonance (LSPR) properties of Au/Ag/graphene nanoshells are studied by discrete dipole approximation (DDA). The coupled resonance wavelengths show a remarkable dependence on the graphene thickness as well as refractive index of the surrounding medium. The resonance wavelengths of Au/Ag/graphene nanoshells red-shift as the thickness of the graphene layer is increased, when the radii of the Au core and Ag interlayer are 40nm and 45nm, respectively. Specifically, the longer wavelength red-shifts from 540nm to 740nm when the refractive index varies from 1.25 to 2.05.

In this paper, we investigate the plasmonic coupling effects on the localized surface plasmon resonances (LSPRs) of palladium nanoparticle chains. We show the transmission electron microscopy (TEM) images and the extinction cross-section spectra of near-contact palladium nanoparticle chains from monomer to pentamer. The extinction spectra of chains nanoparticles were measured by far-field polarization spectroscopy over a large spectral range (ultraviolet, visible and near-infrared) and compared with numerical calculations based on finite element method (FEM). For single palladium nanoparticle, the LSPR phenomenon appears in ultraviolet region. By addition of palladium nanoparticles to the chain, we observe a tunable red-shifting on the spectral position due to plasmonic coupling between palladium nanoparticles and a systematic spectral amplitude enhancement with the appearance of new modes of resonance.

Divers spectroscopy techniques and advances imaging are elucidated when employing light in a controlled manner. One of the features of the light focusing fields is the localized surface plasmon resonance (LSPR). In this paper, we study the LSPRs for different arrangements of palladium (Pd) nanostructures with respect to light polarization in the visible and near-infrared regions. The extinction cross-section spectrum of asymmetric nanostructures is measured using far field spectroscopy technique and is calculated using Finite Element Method (FEM). The spectra of the nanostructures various arrangements recorded from the two methods are in very good agreement. Depending on the light polarization, the nanostructures produce strong plasmonic coupling. This is represented by the induction of dipole and quadrupole LSPR modes. A clear enhancement of the extinction spectrum has been evidenced by increasing the number of particles of nanostructures. The main advantage of the transition metallic nanostructures of different arrangements lies in the generation of a highly enhanced electromagnetic field accompanied by a redshift of LSPR spectrum that can be exploited in diverse applications.

We have prepared CoNPs@CN that cobalt nanoparticles(CoNPs) dispersed uniformly in the carbon matrix Composite (CN) via a facile and controllable method. Samples were characterized by X-ray diffraction (XRD), UV–V spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). CoNPs@CN exhibited favorable photocatalytic activity under visible light irradiation. The results of quenching and photoluminescence experiments reveal the generation of main active species (•OH and •O${}_2^{-}$ radicals). The producing mechanism of active species can be attributed to that CoNPs@CN absorb photons and generate photogenerated electrons through localized surface plasmon resonance (LSPR) effect, then H₂O and O₂ in the solution react with the photogenerated hole and electrons to produce •OH and •O${}_2^{-}$ radicals.

In this work, Ag nanoparticle/Ag-doped SiO₂ composite films were prepared with AgNO₃ and tetraethoxysilane precursors through a simple and environmentally friendly sol–gel method under high annealing temperatures. The effect of different annealing temperatures (400${}^{\circ }$C, 500${}^{\circ }$C, 600${}^{\circ }$C, and 700${}^{\circ }$C) on the structural and optical characters of the composite films was investigated. The localized surface plasmon resonance (LSPR) effect of the Ag nanoparticle/Ag-doped SiO₂ composite films enhanced the fluorescence intensity of CdSe quantum dots (QDs). Scanning electron microscopy (SEM), UV-vis spectrophotometer and photoluminescence (PL) spectroscopy were used to characterize the morphology and optical properties of the composite nanostructure.