Broad Surface Plasmon Resonance Absorption Research Articles

Colloid-Interface-Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities.

High-efficient charge and energy transfer between nanocrystals (NCs) in a bottom-up assembly are hard to achieve, resulting in an obstacle in application. Instead of the ligands exchange strategies, the advantage of a continuous laser is taken with optimal wavelength and power to irradiate the film-scale NCs superlattices at solid-liquid interfaces. Owing to the Au-based NCs' surface plasmon resonance (SPR) effect, the gentle laser irradiation leads the Au NCs or Au@CdS core/shell NCs to attach each other with controlled pattern at the interfaces between solid NCs phase and liquid ethanol/ethylene glycol. A continuous wave 532 nm laser (6.68-13.37 W cm-2 ), to control Au-based superlattices, is used to form the monolayer with uniformly reduced interparticle distance followed by welded superstructures. Considering the size effect to Au NCs' melting, when decreasing the Au NCs size to ≈5 nm, stronger welding nanostructures are obtained with diverse unprecedented shapes which cannot be achieved by normal colloidal synthesis. With the help of facile scale-up and formation at solid-liquid interfaces, and a good connection of crystalline between NCs, the obtained plasmonic superstructured films that could be facilely transferred onto different substrates exhibit broad SPR absorption in the visible and near-infrared regime, enhanced electric conductivities, and wide applications as surface enhanced Raman scattering (SERS)-active substrates.

Implantation-synthesized Cu/Cu–Zn core/shell nanoparticles in SiO_2 and their optical properties

Silica glasses were pre-implanted with 60 keV Zn ions at different fluences of 1 × 1016 and 1 × 1017 cm−2, respectively, and were then subjected to implantation of 45 keV Cu ions at a fluence of 5 × 1016 cm−2. The formation of metallic nanoparticles (NPs) as well as their optical properties has been studied in details. Our results clearly show that Zn ion preimplantation at a low fluence of 1.0 × 1016 cm–2 can give rise to the formation of large Cu NPs with a double-layer arrangement, which contribute a greatly enhanced surface plasmon resonance (SPR) absorption at about 572 nm. As the Zn ion fluence increases to 1.0 × 1017 cm–2, Cu/Cu–Zn core/shell NPs with a high particle density and a narrow size distribution can be obtained, resulting in a strong and broad SPR absorption band around 528 nm. Besides, the dually implanted samples also exhibit excellent third-order nonlinear optical properties comparing with the Cu solely implanted sample. The possible mechanisms for the nucleation and growth of NPs as well as for the enhancements of linear and nonlinear optical properties have been discussed.

One-step synthesis of Ag–Fe3O4 nanocomposites and their SERS properties

Noble metal and ferromagnetic oxides nanocomposites have attracted great interest because of their optical and magnetic properties. In this paper, we prepared Ag–Fe3O4 nanocomposites by a facile, one-step, and repeatable solvothermal method. The diameter of the as-synthesized nanocomposites was about 250 nm, and the composition of the products was tuned by varying the molar ratio of Ag/Fe. The saturated magnetization of the Ag–Fe3O4 nanocomposites at room temperature gradually decreased with increasing of Ag/Fe molar ratios. The saturated magnetization of the products was 30.6 emu g−1 with the molar ratio of 1:1, which enables them to be easily concentrated from the solution by simply applying a small magnet. These nanocomposites have broad surface plasmon resonance absorption bands from 400 to 600 nm, which are overlapping with the excitation laser of 532 nm. The surface-enhanced Raman spectroscopy (SERS) properties of the nanocomposites were studied using Rhodamine 6G and crystal violet as the target molecules. The correlation of the product composition on SERS was then demonstrated by gradually increasing Ag/Fe molar ratios. So these efficiently and conveniently concentrated products have a great potential in the fields of the biomedical sensitive detection and assay.

Ag-Nanoparticle-Decorated SiO2 Nanospheres Exhibiting Remarkable Plasmon-Mediated Photocatalytic Properties

We demonstrated for the first time that Ag-nanoparticle-decorated SiO2 nanospheres (NSs) may display noticeable photocatalytic activities upon surface plasmon resonance (SPR) excitation. The samples were prepared by reacting SiO2 NSs with AgNO3 in the seed-mediated growth process, from which the Ag particle size and decoration density can be readily controlled. The dependence of the SPR-mediated photocatalytic performance of Ag-decorated SiO2 NSs on the Ag morphology was investigated and presented. The as-prepared Ag-decorated SiO2 NSs showed a significantly red shifted and relatively broad SPR absorption when compared with the individually dispersed Ag nanoparticles. Owing to the considerably broad SPR absorption that spanned from the visible to the near-infrared region, Ag-decorated SiO2 NSs surpassed N-doped P-25 TiO2 powder and individually dispersed Ag nanoparticles in photocatalytic activity, demonstrating their potential as an active photocatalyst in nearly all the current photocatalysis applicatio...

Effects of post-thermal annealing temperature on the optical and structural properties of gold particles on silicon suboxide films

In this work, silicon suboxide (SiO x ) thin films were deposited using a RF magnetron sputtering system. A thin layer of gold (Au) with a thickness of about 10 nm was sputtered onto the surface of the deposited SiO x films prior to the thermal annealing process at 400 °C, 600 °C, 800 °C and 1000 °C. The optical and structural properties of the samples were studied using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and optical transmission and reflection spectroscopy. SEM analyses demonstrated that the samples annealed at different temperatures produced different Au particle sizes and shapes. SiO x nanowires were found in the sample annealed at 1000 °C. Au particles induce the crystallinity of SiO x thin films in the post-thermal annealing process at different temperatures. These annealed samples produced silicon nanocrystallites with sizes of less than 4 nm, and the Au nanocrystallite sizes were in the range of 7–23 nm. With increased annealing temperature, the bond angle of the Si–O bond increased and the optical energy gap of the thin films decreased. The appearance of broad surface plasmon resonance absorption peaks in the region of 590–740 nm was observed due to the inclusion of Au particles in the samples. The results show that the position and intensity of the surface plasmon resonance peaks can be greatly influenced by the size, shape and distribution of Au particles.

Synthesis and Characterization of Ag-Polymer Nanocomposites

We report the synthesis of Ag nanoparticles in polyethylene terephthalate (PET) matrix using atom beam co-sputtering. Metal filling factor was evaluated by Rutherford backscattering spectrometry. Microstructural evolutions of the nanocomposites films were investigated by transmission electron microscopy, which confirmed the formation of irregular shaped Ag nanoparticles. The X-ray photoelectron spectroscopy measurements of the sputter deposited PET film and co-sputtered deposited Ag-PET as well as PET bulk foil (from Goodfellows) were performed to study chemical composition of the nanocomposite films. The optical properties of these nanocomposites were studied by light absorption/transmission, which revealed a narrow transmission of UV light approximately 320 nm and a broad surface plasmon resonance absorption extending up to infrared region (approximately 2400 nm). Swift heavy ion irradiation of Ag-PET nanocomposite resulted in narrowing the full width at half maximum of transmission band.

Synthesis of Plasmonic Nanocomposites for Diverse Applications

We report the synthesis of gold and silver nanostructures embedded in different dielectric matrices by atom beam co-sputtering, a novel technique. We have synthesized gold-silicon core shell nanostructures and Au-ZnO nanocomposite with tunable surface plasmon resonance (SPR) by atom beam co-sputtering and subsequent annealing. The Au-ZnO nanocomposite shows significant enhancement in intensity of Raman modes of fullerene molecules and therefore can help in surface enhanced Raman spectroscopy investigation of organic molecules. The synthesized Ag-polymer nanocomposite thin films show excellent features of broad SPR absorption extending upto IR region and a narrow transmission of light in UV region approximately 320 nm which could be of technological interest in solar absorbers and UV light filters respectively. The Ag-silica nanocomposite thin films show their utility in glucose sensing. The gold-silica nanocomposite thin films exhibit their possible use in detection of human ovarian cancer cells in a preliminary study. The shift in SPR peak of Au nanoparticles (NPs) present at the surface of silica synthesized by thermal evaporation and annealing, after attachment of biological molecules like proteins has been studied.

Effect of annealing on the optical absorption of Ni nanoparticles in MgO single crystals

Ni+ ion implantation with an energy of 64keV in MgO single crystals was conducted at room temperature up to a fluence of 1×1017ion/cm2. The as-implanted crystals were annealed isochronally at temperatures up to 900°C. Optical absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) have been utilized to characterize the changes of optical properties and the microstructure of the annealed samples. XPS results showed that the charge state of implanted Ni was still mainly in metallic Ni0 after annealing at 900°C. TEM analysis revealed metallic Ni nanoparticles with depth-dependant dimensions of ∼1–10nm in the annealed sample. Optical absorption spectroscopy indicated that the Ni nanoparticles exhibited a broad surface plasmon resonance absorption band in annealed samples and the band shifted to a longer wavelength with the increasing annealing temperature.