Sheng-Qing Zhu

Gold nanoparticle thin films fabricated by electrophoretic deposition method for highly sensitive SERS application

We report an electrophoretic deposition method for the fabrication of gold nanoparticle (GNP) thin films as sensitive surface-enhanced Raman scattering (SERS) substrates. In this method, GNP sol, synthesized by a seed-mediated growth approach, and indium tin oxide (ITO) glass substrates were utilized as an electrophoretic solution and electrodes, respectively. From the scanning electron microscopy analysis, we found that the density of GNPs deposited on ITO glass substrates increases with prolonged electrophoresis time. The films possess high mechanical adhesion strength and exhibit strong localized surface plasmon resonance (LSPR) effect by showing high SERS sensitivity to detect 1 × 10−7 M rhodamine 6 G in methanol solution. Finally, the relationship between Raman signal amplification capability and GNP deposition density has been further investigated. The results of our experiment indicate that the high-density GNP film shows relatively higher signal amplification capability due to the strong LSPR effect in narrow gap regions between the neighboring particles on the film.

Fabrication and spectroscopic investigation of branched silver nanowires and nanomeshworks

Wide wavelength ranges of light localization and scattering characteristics can be attributed to shape-dependent longitude surface plasmon resonance in complicated nanostructures. We have studied this phenomenon by spectroscopic measurement and a three-dimensional numerical simulation, for the first time, on the high-density branched silver nanowires and nanomeshworks at room temperature. These nanostructures were fabricated with simple light-induced colloidal method. In the range from the visible to the near-infrared wavelengths, light has been found effectively trapped in those trapping sites which were randomly distributed at the corners, the branches, and the junctions of the nanostructures in those nanostructures in three dimensions. The broadened bandwidth electromagnetic field enhancement property makes these branched nanostructures useful in optical processing and photovoltaic applications.

Optical properties of Ag nanoparticle-polymer composite film based on two-dimensional Au nanoparticle array film.

The nanocomposite polyvinyl pyrrolidone (PVP) films containing Ag nanoparticles and Rhodamine 6G are prepared on the two-dimensional distinctive continuous ultrathin gold nanofilms. We investigate the optical properties and the fluorescence properties of silver nanoparticles-PVP polymer composite films influenced by Ag nanoparticles and Au nanoparticles. Absorption spectral analysis suggests that the prominently light absorption in Ag nanowire/PVP and Ag nanowire/PVP/Au film arises from the localized surface plasmon resonance of Ag nanowire and Au nanofilm. The enhanced fluorescence is observed in the presence of Ag nanowire and Au nanofilm, which is attributed to the excitation of surface plasmon polariton resonance of Ag nanowire and Au nanofilm. The gold nanofilm is proven to be very effective fluorescence resonance energy transfer donors. The fabricated novel structure, gold ultrathin continuous nanofilm, possesses high surface plasmon resonance properties and prominent fluorescence enhancement effect. Therefore, the ultrathin continuous gold nanofilm is an active substrate on nanoparticle-enhanced fluorescence.

Two-dimensional ultrathin gold film composed of steadily linked dense nanoparticle with surface plasmon resonance

BackgroundNoble metallic nanoparticles have prominent optical local-field enhancement and light trapping properties in the visible light region resulting from surface plasmon resonances.ResultsWe investigate the optical spectral properties and the surface-enhanced Raman spectroscopy of two-dimensional distinctive continuous ultrathin gold nanofilms. Experimental results show that the one- or two-layer nanofilm obviously increases absorbance in PEDOT:PSS and P3HT:PCBM layers and the gold nanofilm acquires high Raman-enhancing capability.ConclusionsThe fabricated novel structure of the continuous ultrathin gold nanofilms possesses high surface plasmon resonance properties and boasts a high surface-enhanced Raman scattering (SERS) enhancement factor, which can be a robust and cost-efficient SERS substrate. Interestingly, owing to the distinctive morphology and high light transmittance, the peculiar nanofilm can be used in multilayer photovoltaic devices to trap light without affecting the physical thickness of solar photovoltaic absorber layers and yielding new options for solar cell design.

Light absorption enhancement in organic solar cell by embedding Ag nanoparticles and nanochains within the active layer

We numerically investigate the light absorption enhancement of organic photovoltaic cells by embedding Ag nanoparticles and nanochains within the active layer using a finite element method. We analyze the enhancement mechanism of light absorption and systematically study the influence of factors such as the size and the period of silver nanoparticles. The result shows the localized surface plasmon resonance of the particles has a significant influence on the light absorption. Under AM1.5 illumination condition, a relative enhancement with a factor of 107.1% is observed for nanoparticles with a diameter of 30 nm and a period of 200 nm. In addition, different types of nanochain structures have been studied, and we find that, comparing to monodisperse nanoparticles, nanochain structures can further enhance the light absorption because of the stronger light harvesting in the long wavelength range of 600–800 nm.

Study on the synthesis and optical properties of polyurethane-imide

In this paper, Polyurethane-imide (PUI) which has the advantages of polyurethane and polyimide is synthesized and introduced to apply in the slab optical waveguide devices. The PUI is characterized by infrared spectrum (FT-IR), differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). Slab optical waveguide is prepared via spin coating the cyclopentanone solution of PUI on top of K9 glass and cured at 140 °C for 20 minutes to complete removal of the solvent from the film. The film-formability of PUI is characterized by atomic force microscope (AFM). The results of DSC and TGA indicate that the PUI exhibits high thermal stability up to its glass-transition temperature (Tg) of 206 °C and 10% heat loss temperature of 310°C. Optical properties of absorption behavior and propagation loss are investigated in slab waveguides, and propagation loss of 1.782 dB/cm at 1310nm in TE (transverse electric field) mode has been achieved by using prism-coupler method. The results show that polyurethane-imide has distinct merits: good processability, high thermal stability and moderate glass-transition temperature, excellent film-formability, and low propagation loss. These advantages of polyurethane-imides make them suitable as electro-optic polymeric materials in integrated optics.