The enhanced random lasing from dye-doped polymer films with different-sized silver nanoparticles

We reported on the enhanced random lasing from organic dyes doped with silver nanoparticles (Ag NPs), the sizes of Ag NPs ranged from 8 nm to 250 nm. The effects of different sizes of Ag NPs on the lasing properties were studied. We found a strong dependence of the random lasing properties on the size of the Ag NPs, and the lowest threshold was achieved by the introduction of Ag NPs with the diameter of 150 nm. By studying the enhanced localized electromagnetic (EM) field due to localized surface-plasmon resonance and the scattering effect of Ag NPs in experiment and Mie theory, we found that the enhanced localized EM field plays a major role on enhanced lasing of organic dyes for the small Ag NPs (diameter < 50 nm); and the scattering effect is the dominant underlying mechanism for random lasing for the large Ag NPs (diameter ≥ 100 nm), which also suggest that the lowest threshold and strongest lasing are dominated by the photon scattering.     

All thermal-evaporated surface plasmon enhanced organic solar cells by Au nanoparticles

Au nanoparticles (NPs) are fabricated on indium-tin-oxide substrates by a thermal evaporation method and incorporated to an efficient small molecule organic solar cell (OSC). This renders an all thermal evaporated surface plasmon enhanced OSC. The optimized device shows a power conversion efficiency of 3.40%, which is 14% higher than that of the reference device without Au NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au NPs and the increased conductivity of the device.     

纳米银颗粒表面增强荧光效应与其覆盖率的关联

实验上获得了纳米银颗粒对光敏剂二氢卟吩f-甲醚(CPD4)的荧光增强效应,基于纳米银颗粒覆盖率对表面增强荧光效应的影响,初步探讨了荧光增强的物理增强机制。不同覆盖率纳米银基底表面吸附的CPD4的增强荧光结果显示,在低颗粒覆盖率时(<30%),激发效率和激发态分子衰减速率不依赖于覆盖率变化;当颗粒覆盖率大于30%接近40%时,激发效率和激发态分子衰减速率都得到提高。实验和理论结果均表明,相比于单个银纳米颗粒,颗粒覆盖率增加提高了颗粒间电磁耦合效应,能够产生更强的表面增强荧光效应。     

High enhancement factor of Au nano triangular prism structure for surface enhanced coherent anti-Stokes Raman scattering

Coherent anti-Stokes Raman scattering spectroscopy(CARS) is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels, while the enhancement factor for surface plasmon resonances(SPR) are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 10¹⁶ over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering.     

Cooperative plasmon enhanced organic solar cells with thermal coevaporated Au and Ag nanoparticles

Cooperative plasmon enhanced small molecule organic solar cells are demonstrated based on thermal coevaporated Au and Ag nanoparticles (NPs). The optimized device with an appropriate molar ratio of Au:Ag NPs shows a power conversion efficiency of 3.32%, which is 22.5% higher than that of the reference device without any NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au:Ag NPs and the increased conductivity of the device. Besides, factors that determining the performance of the Au:Ag NPs cooperative plasmon enhance organic solar cells are investigated, and it finds that the thickness of MoO₃ buffer layer plays a crucial role. Owing to the different diameter of the thermal evaporated Au and Ag NPs, a suitable MoO₃ buffer layer is required to afford a large electromagnetic enhancement and to avoid significant exciton quenching by the NPs.     

等臂L形银纳米天线的表面等离子特性研究

利用FDTD方法分析了由银纳米线形成的等臂L形光学共振天线的共振模式。研究了其场增强特性及共振散射谱的变化。L形纳米天线的近场增强特性强烈依赖于入射偏振,入射光偏振方向沿垂直于镜面对称轴方向时有最大一阶共振近场增强;入射光偏振方向沿镜面对称轴方向时有最大的二阶共振近场增强。     

Enhanced power conversion efficiency of organic photovoltaic devices due to the surface plasmonic resonance effect generated utilizing Au-WO3 nanocomposites

Au-WO₃ nanocomposites (NCs) were used as a hole transport layer (HTL) to enhance the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells. The photon absorption of the active layer in the OPV cells was increased due to the plasmonic effect caused by the Au-WO₃ NCs, resulting in an enhanced short-circuit current density for the OPV cells with the Au-WO₃ NC HTL. The value of the root-mean-square roughness of the Au-WO₃ NC film was smaller than that of the WO₃ NP film, resulting in a more efficient transport of holes from the active layer. The PCE of the OPV cell with an Au-WO₃ NCs HTL with an Au NP concentration of 10 wt% was improved by 60.37% in comparison with that with WO₃ nanoparticles. The enhancement of the PCE was attributed to both an increase in the efficiency of the hole transport at an Au-WO₃ NCs HTL with an Au NP concentration of 10 wt%/active layer heterointerface and an enhanced photon absorption due to the localized surface plasmon resonance effect of the Au-WO₃ NCs.     

银纳米立方体对诺丹明分子的荧光增强或猝灭效应实验研究

用乙二醇还原硝酸银,成功制备了平均边长约97 nm的银纳米立方体以用于诺丹明(RhB)分子的荧光实验。实验中,将探针分子 RhB 粉末掺杂于PMMA苯甲醚溶液中,制得不同厚度参杂有RhB探针分子的PMMA薄膜,运用光谱技术和共焦显微技术研究了银纳米立方体与荧光分子的间隔、银纳米立方体不同浓度分布对RhB分子的荧光强度的影响。荧光光谱表明,荧光强度随PMMA厚度变薄而增强,当PMMA厚度为10nm时,荧光增强因子最大,获得了56倍的荧光增强效果,而继续减小PMMA厚度时,其荧光增强因子又变小,说明发生了荧光猝灭效应。共焦荧光像则更直观地表现了银纳米立方体的浓度分布对荧光分子辐射增强的影响。因而,可通过调控银纳米立方体与荧光分子的距离及银纳米立方体的分布优化荧光增强因子以用于基于荧光的单分子探测,这一实验结果在生物成像和生物传感领域有潜在应用价值。     

受纳米结构损伤限制的光纤拉曼探头SERS探测灵敏度

利用光线追迹法,研究了典型光纤拉曼探头在纳米结构损伤限制下收集到的SERS功率与样品位置之间关系,结果表明,对于不同焦距构成的同轴等光程光纤拉曼探头,在给定的纳米结构损伤阈值激发光功率密度下,样品偏离焦平面反而会使探头收集到的SERS功率增加,相比于样品远离探头方向偏离焦平面,靠近探头方向偏离焦平面时收集到的SERS功率更高。此外,收集光纤芯径越大,探头所收集的SERS功率越大。     

Hierarchically Ordered Arrays of Noncircular Silicon Nanowires Featured by Holographic Lithography Toward a High‐Fidelity Sensing Platform

A novel, highly uniform and tunable hybrid plasmonic array is created via ion‐milling, catalytic wet‐etching and electron‐beam evaporation, using a holographically featured structure as a milling mask. A simple and low‐cost prism holographic lithography (HL) technique is applied to create an unprecedentedly coordinated array of elliptic gold (Au) holes, which act as the silicon (Si) etching catalyst in the reaction solution used to fabricate an elliptic silicon nanowire (SiNW) array; here, the SiNWs are arrayed hierarchically in such a way that three SiNWs are triangularly coordinated, and the triangles are arranged hexagonally. After removing the polymeric mask and metal thin film, the highly anisotropic thick Au film is deposited on the SiNW arrays. This hybrid substrate shows tunable optical properties in the near‐infrared (NIR) region from 875 nm to 1030 nm and surface‐enhanced Raman scattering (SERS) activities; these characteristics depend on the catalytic wet etching time, which changes the size of the vertical gap between the Au thick films deposited separately on the SiNWs. In addition, lateral interparticle coupling induces highly intensified SERS signals with good homogeneity. Finally, the Au‐capped elliptical SiNW arrays can be hierarchically patterned by combining prism HL and conventional photolithography, and the highly enhanced fluorescence intensity associated with both the structural effects and the plasmon resonances is investigated.     

Ag纳米粒子点阵的表面等离激元共振特性调控

通过纳米粒子束流气相沉积方法在衬底表面沉积稠密银纳米粒子点阵。通过对纳米粒子覆盖率的精细控制与纳米粒子点阵消光谱的实时监测,实现了其表面等离激元共振峰频率的系统调控。随着Ag纳米粒子密度的增加,点阵的表面等离激元共振波长发生红移,可逐步由小于400nm增大到570nm以上。研究发现,表面等离激元共振波长的变化与随纳米粒子沉积量增加而增加的紧密相邻的纳米粒子对的百分数相关。     

纳米结构分子吸附引起的表面增强拉曼散射研究

利用模板印刷技术,制备了具有不同局域表面等离子体共振(LSPR)峰的Au纳米空心半球壳结构,并以4-巯基苯胺(4-ATP)为探针分子研究了纳米结构表面吸附分子对表面增强拉曼散射(SERS)强度的影响。结果表明,当纳米结构的LSPR峰位处于激发光波长的短波长或"马鞍型"位置时,SERS强度随吸附分子数的增加而增大;当处于长波长位置时,SERS强度呈现先增大后减小的趋势。利用分子吸附理论和纳米结构表面局域场强度变化,对此现象进行了解释。     

Realizing improved performance of down-conversion white organic light-emitting diodes by localized surface plasmon resonance effect of Ag nanoparticles

Down-conversion structure white organic light-emitting diodes (WOLEDs), in which white light is generated by a blue emission organic light-emitting diodes (OLEDs) in combination with a color conversion layer (CCL) outside the substrate, has attracted extensive interest due to its significant advantages in low cost and stabilized white-light emissions. However, low color-conversion efficiency of CCL is still a bottleneck for the performance improvement of down-conversion WOLEDs. Here, we demonstrate an approach to enhance the color-conversion efficiency of CCL-WOLEDs by localized surface plasmon resonance (LSPR) effect. In this approach, a blend of Ag nanoparticles and polyvinyl alcohol (PVA) is solution-deposited between the blue organic light emitting diodes and color-conversion layer. Based on the LSPR effect of this modified structure, the color conversion efficiency has improved 32%, from 45.4% to 60%, resulting a 14.4% enhancement of the current efficiency, from 9.73 cd/A to 11.14 cd/A. Our work provides a simple and low-cost way to enhance the performance of down-conversion WOLEDs, which highlights its potential in illumination applications.     

表面等离子共振Ag-SnO2复合膜光学传感器

为了研究CuO的不同掺杂浓度对表面等离子共振角的影响,提出一种新型的棱镜耦合法Ag-SnO2(掺杂CuO)复合膜表面等离子共振光学传感器结构.采用射频反应溅射法在清洗处理后的金红石棱镜上依次制备Ag膜(50nm),SnO2膜(50nm),CuO和SnO2膜(50nm)4层膜结构,CuO的厚度依其不同的掺杂体积分数的不同而不同,经过退火实现SnO2薄膜的掺杂得到复合膜.以He-Ne激光62.8nm为入射激励光源,通过采用表面等离子共振实验方法,CuO的掺杂体积分数分别为0,0.01和0.05时,得到共振角分别为59.61°,60.52°和61.3°的结果.结果表明,CuO掺杂的体积分数越大,表面等离子共振的共振角越大.     

平面波导激励的对称型表面等离子体共振结构的研究

研究了一种平面波导激励的对称型表面等离子体共振（SPR）结构,该结构以一定厚度的介质两侧覆盖金属层为核心。理论分析表明,该结构的TM0模式为表面波。研究了一定波长下不同介质时金属膜间介质厚度与等效折射率之间自勺．关系。采用离子交换技术制备了多模平面波导,对其等效折射率进行了测试,采用平面波导激励对称结构的等离子体表面波...     

金纳米颗粒增强富硅氮化硅发光特性的研究

采用时域有限差分(FDTD)方法,对Au纳米颗粒的尺寸和形貌对于其光学特性的影响进行了系统的理论研究。通过采用等离子体增强化学气相沉积(PECVD)、晶化处理、电子束蒸发和高温退火等工艺,制备基于局域表面等离子共振(LSPR)效应的富硅氮化硅发光芯片。利用拉曼光谱仪、扫描电子显微镜(SEM)、奥林巴斯显微镜等对不同结构Au纳米颗粒富硅氮化硅发光器件的特性进行了表征。研究表明,通过对Au纳米颗粒的大小、形状和分布合理优化,富硅氮化硅芯片的发光强度在570nm波长附近提升了7倍,增强峰的位置红移了10nm。     

脉冲激光改性金属纳米薄膜的等离子体特性

在室温环境下,实验采用Nd\:YAG光纤脉冲激光器辐照银(Ag)、铜(Cu)、铝(Al)三种光滑连续的金属薄膜,制备出了对应的三种金属纳米颗粒薄膜。通过调节激光扫描速率可以实现三种金属纳米颗粒薄膜的局域表面等离子体共振(LSPR)波长和强度的调谐。其中,Ag纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现出较宽的调谐范围,Cu纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现较小的调谐范围,Al纳米颗粒薄膜在紫外光波段的等离子体吸收峰窄而尖锐,且LSPR波长调谐范围也较小。与激光辐照前的三种金属薄膜相比,激光辐照后生成的三种金属纳米颗粒薄膜出现了更强的表面增强拉曼散射信号。有限差分时域仿真模拟出的样品的电场强度分布与实验得到的表面增强拉曼散射结果一致。     

表面等离子共振Ag／TiO2复合膜双光束光强归一化传感器

为了克服由于光源光强的波动而导致的表面等离子共振传感器的测量误差,提出一种双光束归一化光强的表面等离子共振检测方法,传感器的结构为金红石材料作成的棱镜作为耦合棱镜,在棱镜的底边采用射频溅射技术制作AS／TiO2复合膜,Ag膜和TiO2膜的厚度分别为50nm和100nm,在复合膜上设置待测气体的样品池。在He—Ne光入射激励下,复合膜的分界面发生表面等离子共振现象。实验结果表明：采用了双光束归一化光强检测方法,使系统的重复性、稳定性得到大大的提高,减少了测量误差。