Dual-layer Metallic grating(DMG)structures as surface-enhanced Raman scattering(SERS)substrates are studied using benzenethiol as the probe analyte.The DMG structure consists of a SiO2 grating and 100-nm-thick gold co...Dual-layer Metallic grating(DMG)structures as surface-enhanced Raman scattering(SERS)substrates are studied using benzenethiol as the probe analyte.The DMG structure consists of a SiO2 grating and 100-nm-thick gold coating layers.An enhancement factor of 105 is achieved by optimizing the SiO 2 grating height within the range from 165 to 550 nm.The enhancement factor dependence on the SiO2 grating height is due to the surface plasmon excitation,which is dependent on the polarization of the incident light,and confirmed by finite difference time domain simulations.This study demonstrates the advantages of high uniformity,reproducibility and sensitivity in the DMG structures for SERS applications.展开更多
We report a facile method of preparing novel branched silver nanowire structures such as Y-shaped, K-shaped and other multi-branched nanowires. These branched nanostructures are synthesized by reducing silver nitrate ...We report a facile method of preparing novel branched silver nanowire structures such as Y-shaped, K-shaped and other multi-branched nanowires. These branched nanostructures are synthesized by reducing silver nitrate （AgNO3） in polyethylene glycol （PEG） with polyvinglpyrrolidone （PVP） as capping agent. Statistical data indicate that for the ＂y＂ typed branched nanowire, the branches grow out from the side of the trunk nanowire in a preferential orientation with an angle of 55° between the branch and the trunk. Transmission electron microscopy （TEM） studies indicate that the defects on silver nanowires could support the growth of branched nanowires. Conditions such as the molar ratio of PVP/AgNO3, the reaction temperature, and the degree of polymerization of reducing agent and PVP play important roles in determining the yield of the silver branches. Due to the rough surface, these branched nanostructures can be used as efficient substrates for surface-enhanced Raman scattering applications.展开更多
Bending and first flexural mode vibration behavior of electrostatic actuated nanometer-sized interdigitated cantilever arrays are characterized under vacuum conditions. The pull-in＇＇ effect in dc driving and the har...Bending and first flexural mode vibration behavior of electrostatic actuated nanometer-sized interdigitated cantilever arrays are characterized under vacuum conditions. The pull-in＇＇ effect in dc driving and the hard spring effect＇＇ in ac driving are observed. A mass sensitivity of 20 fg is expected for our devices due to the ultra-small mass of the arm and relative high Q factor. The mass-spring lump model combined with Green＇s function method is used to fit the dc driving behaviors including the pull-in voltage. For the ac driving case, the polynomial expansion of the capacitive force is used in the model. The successfully fittings of the pull-in voltage and the hard spring effect prove that our simulation method could be used for guiding the geometrical design of cantilever-based sensors.展开更多
Realizing photon upconversion in nanostructures is important for many next- generation applications such as biological labelling, infrared detectors and solar cells. In particular nanowires are attractive for optoelec...Realizing photon upconversion in nanostructures is important for many next- generation applications such as biological labelling, infrared detectors and solar cells. In particular nanowires are attractive for optoelectronics because they can easily be electrically contacted. Here we demonstrate photon upconversion with a large energy shift in highly n-doped InP nanowires. Crucially, the mechanism responsible for the upconversion in our system does not rely on multi-photon absorption via intermediate states, thus eliminating the need for high photon fluxes to achieve upconversion. The demonstrated upconversion paves the way for utilizing nanowires--with their inherent flexibility such as electrical contactability and the ability to position individual nanowires--for photon upconversion devices also at low photon fluxes, possibly down to the single photon level in optimised structures.展开更多
基金supported by the International S&T Cooperation Program of China(2006DFB02020)the National Basic Research Program of China(2007CB936800 and 2009CB930704)the Hundred Talents Program of the Chinese Academy of Sciences.
文摘Dual-layer Metallic grating(DMG)structures as surface-enhanced Raman scattering(SERS)substrates are studied using benzenethiol as the probe analyte.The DMG structure consists of a SiO2 grating and 100-nm-thick gold coating layers.An enhancement factor of 105 is achieved by optimizing the SiO 2 grating height within the range from 165 to 550 nm.The enhancement factor dependence on the SiO2 grating height is due to the surface plasmon excitation,which is dependent on the polarization of the incident light,and confirmed by finite difference time domain simulations.This study demonstrates the advantages of high uniformity,reproducibility and sensitivity in the DMG structures for SERS applications.
文摘We report a facile method of preparing novel branched silver nanowire structures such as Y-shaped, K-shaped and other multi-branched nanowires. These branched nanostructures are synthesized by reducing silver nitrate （AgNO3） in polyethylene glycol （PEG） with polyvinglpyrrolidone （PVP） as capping agent. Statistical data indicate that for the ＂y＂ typed branched nanowire, the branches grow out from the side of the trunk nanowire in a preferential orientation with an angle of 55° between the branch and the trunk. Transmission electron microscopy （TEM） studies indicate that the defects on silver nanowires could support the growth of branched nanowires. Conditions such as the molar ratio of PVP/AgNO3, the reaction temperature, and the degree of polymerization of reducing agent and PVP play important roles in determining the yield of the silver branches. Due to the rough surface, these branched nanostructures can be used as efficient substrates for surface-enhanced Raman scattering applications.
文摘Bending and first flexural mode vibration behavior of electrostatic actuated nanometer-sized interdigitated cantilever arrays are characterized under vacuum conditions. The pull-in＇＇ effect in dc driving and the hard spring effect＇＇ in ac driving are observed. A mass sensitivity of 20 fg is expected for our devices due to the ultra-small mass of the arm and relative high Q factor. The mass-spring lump model combined with Green＇s function method is used to fit the dc driving behaviors including the pull-in voltage. For the ac driving case, the polynomial expansion of the capacitive force is used in the model. The successfully fittings of the pull-in voltage and the hard spring effect prove that our simulation method could be used for guiding the geometrical design of cantilever-based sensors.
文摘Realizing photon upconversion in nanostructures is important for many next- generation applications such as biological labelling, infrared detectors and solar cells. In particular nanowires are attractive for optoelectronics because they can easily be electrically contacted. Here we demonstrate photon upconversion with a large energy shift in highly n-doped InP nanowires. Crucially, the mechanism responsible for the upconversion in our system does not rely on multi-photon absorption via intermediate states, thus eliminating the need for high photon fluxes to achieve upconversion. The demonstrated upconversion paves the way for utilizing nanowires--with their inherent flexibility such as electrical contactability and the ability to position individual nanowires--for photon upconversion devices also at low photon fluxes, possibly down to the single photon level in optimised structures.
