Silicon eccentric shell nanoparticles fabricated by template-assisted deposition for Mie magnetic resonances enhanced light confinement.

We report a structure of silicon eccentric shell particles array, fabricated by the SiO2particles monolayer array assisted deposition of amorphous Si, for high-efficiency light confinement. The SiO2particles monolayer array is tailored to regulate its interparticle distance, followed by silicon film deposition to obtain silicon eccentric shell arrays with positive and negative off-center distancee. We studied the Mie resonances of silicon solid sphere, concentric shell, eccentric shell and observed that the eccentric shell with positive off-centeresupports superior light confinement because of the enhanced Mie magnetic resonances. Spectroscopic measurements and finite difference time domain simulations were conducted to examine the optical performance of the eccentric shell particles array. Results show that the Mie magnetic resonance wavelength can be easily regulated by the size of the inner void of the silicon shell to realize tunable enhanced light confinement. It was found silicon shell withD= 460/520 nm offered high enhanced light absorption efficiency at wavelength ofλ= 830 nm, almost beyond the bandgap of the amorphous silicon.

Hybrid nanostructure of SiO2@Si with Au-nanoparticles for surface enhanced Raman spectroscopy.

In this study, a structure of large-area orderly-arranged SiO2@Si core-shell nanoparticles decorated with Au nanoparticles was fabricated for surface-enhanced Raman spectroscopy (SERS). This hybrid structure features light confinement in the Si shells and a uniform distribution of localized electric hot spots. FDTD simulations were carried out to examine the near-field enhancement response of this structure. Results indicate that the strongly enhanced local electric field is attributed to the WGM-LSPR coupling, that is, the coupling of the whispering gallery mode (WGM) of Si nanoshells with the localized surface plasmon resonance (LSPR) of Au nanoparticles. The excitation of WGM comes primarily from the magnetic response of the Si shell with a minor modification by its electric response. The WGM-LSPR coupling of the structure is tunable through the change of geometric parameters of SiO2@Si particles. Raman scattering measurements were conducted on the samples fabricated, which agree well with the simulated results. The measured data gave a SERS G factor of ∼2 × 108 and showed highly sensitive and reproducible SERS signals of R6G with a high spatial uniformity on a 2 × 2 cm2 substrate consisting of an array of SiO2@Si (D = ∼220 nm/290 nm) particles whose outer surfaces were scattered with d = ∼20 nm Au particles.

Multilayered Dual Functional SiO2@Au@SiO2@QD Nanoparticles for Simultaneous Intracellular Heating and Temperature Measurement.

This paper discusses synthesis and application of dual functional SiO2@Au@SiO2@QD composite nanoparticles for integrated intracellular heating with temperature motoring. The particles are of multilayered concentric structure, consisting of Au nanoshells covered with quantum dots, with the former for infrared heating through localized surface plasma resonance while the later for temperature monitoring. The key to integrate plasmonic-heating/thermal-monitoring on a single composite nanoparticle is to ensure that the quantum dots be separated at a certain distance away from the Au shell surface in order to ensure a detectable quantum yield. Direct attachment of the quantum dots onto the Au shell would render the quantum dots practically functionless for temperature monitoring. To integrate quantum dots into Au nanoshells, a quantum quenching barrier of SiO2 was created by modifying a Stöber-like process. Materials, optical and thermal characterization was made of these composite nanoparticles. Cellular uptake of the nanoparticles was discussed. Experiments were performed on simultaneous in vitro heating and temperature monitoring in a cell internalized with the dual-functional SiO2@Au@SiO2@QD composite nanoparticles.

Nano-fabrication of depth-varying amorphous silicon crescent shell array for light trapping.

We report a new structure of depth controllable amorphous silicon (a-Si) crescent shells array, fabricated by the SiO2 monolayer array assisted deposition of a-Si by plasma enhanced chemical vapor deposition and nanosphere lithography, for high-efficiency light trapping applications. The depth of the crescent shell cavity was tailored by selective etching of a-Si layer of the SiO2/a-Si core/shell nanoparticle array with a varied etching time. The morphological changes of the crescent shells were examined by scanning electron microscopy and atomic force microscopy. A simple model is developed to describe the geometrical evolution of the a-Si crescent shells. Spectroscopic measurements and finite difference time domain simulations were conducted to examine the optical performance of the crescent shells. Results show that these nanostructures all have a broadband high efficiency absorption and that the light trapping capability of these crescent shell structures depends on the excitation of depths-regulated optical resonance modes. With an appropriate selection of process parameters, the structure of crescent a-Si shells may be fine-tuned to achieve an optimal light trapping capacity.

Thermal sensing with CdTe/CdS/ZnS quantum dots in human umbilical vein endothelial cells.

An experimental methodology is presented to measure the temperature variation in cells with the usage of CdTe/CdS/ZnS core/shell/shell quantum dots as nanothermometers. The photoluminescence spectral shifts from the endocytosed quantum dots were measured and analyzed to show heat generation in the human umbilical vein endothelial cell following Ca2+ stress. Cytotoxicity evaluation has demonstrated the CdTe/CdS/ZnS QDs are biocompatible to cells. The measured data show that the thermal sensibility of the core/shell/shell nanocrystals has been calibrated and has a linear correlation of 0.16 nm °C-1 along with temperature variation. The photoluminescence spectral shift of QD uptake in the cell indicates a thermogenesis of 3.125 °C.