环形石墨烯纳米结构的等离激元激发

基于含时密度泛函理论,研究了环形石墨烯纳米结构的等离激元激发.在低能共振区,和同尺度大小的石墨烯纳米结构相比,环形石墨烯纳米结构光谱的主要吸收峰发生了红移;体系中有两种主要的等离激元共振模式:低能成键模式和高能反键模式.此外,环形石墨烯纳米结构的等离激元激发对体系尺度的大小也有一定的依赖性.     

碳原子链连接的石墨烯量子点的等离激元激发

基于含时密度泛函理论,研究碳原子链连接的石墨烯纳米结构的等离激元激发和等离激元激发诱导的电子输运。结果表明:随着链的增加,在低能共振区,体系的吸收光谱逐渐红移;当碳原子链较长时,体系在近红外、中红外光谱区都有较强的吸收。在红外光谱区,碳原子链连接的石墨烯纳米结构的等离激元共振模式还取决于碳原子链中原子数的奇偶性;在低能光谱区,强度较大的等离激元共振模式诱导的的电流强度也较大。     

基于纳米颗粒阵列与法布里-珀罗干涉结构的超灵敏传感器设计

当前的等离激元传感主要基于表面等离极化激元和局域表面等离激元共振两种模式.然而基于表面等离极化激元的传感需要精确的入射角度及多种光学元器件的配合方能使用;而基于局域表面等离激元共振的传感由于共振线宽较宽导致其灵敏度和品质因数(figure of merit,FOM)不够高.设计了一种基于纳米颗粒/间隔层/反射层结构的具有超高灵敏度和FOM的折射率传感器.由于表面等离激元晶格模式与局域表面等离激元共振以及法布里-珀罗干涉的相互作用,器件的反射光谱具有一个超窄反射峰.利用这个反射峰实现传感,其灵敏度达到500 nm/RIU,FOM达到625.进一步分析表明,此传感器在不同结构与激发参数下都具有很好的传感灵敏度.该研究结果对高灵敏等离激元传感器设计具有重要参考意义.     

石墨烯量子点的等离激元激发

基于含时密度泛函理论,研究石墨烯量子点的等离激元激发。和宏观大小的石墨烯相比,由于量子点的尺寸和量子受限效应,石墨烯量子点的等离激元具有一些不同的特征。在低能共振区,光谱线发生展宽和劈裂。石墨烯量子点的等离激元激发依赖于边界的构型。此外,对称性对于石墨烯量子点的等离激元激发也起着重要的作用。     

不对称纳米环/椭球二聚体的高阶表面等离激元共振特性

基于三维有限元法,研究了不对称纳米环/椭球二聚体的表面等离激元共振和局域场增强光学特性。结果可得可调的高阶表面等离激元共振,这样的高阶共振源于纳米环和纳米椭球之间的等离激元耦合。同时,在两个纳米结构耦合下,在纳米椭球上可以观察到环形电流,其产生了增强的局域电磁场。数值模拟结果表明,纳米环/椭球二聚体的偏心方向和偏心率对表面等离激元共振有着重要的影响。此结果在表面增强光谱学和生物传感方面都有着潜在的应用。     

Ag@Au双金属纳米颗粒的制备和表征

采用种子生长法制备了银纳米颗粒,通过电置换反应将单金属银颗粒转变为中空金银双金属纳米颗粒.电镜表征及吸收光谱的结果表明,通过控制种子溶液的加入量、超声时间和离心次数等条件,能够有效调控金属纳米颗粒的尺寸以及局域表面等离激元的共振峰位与目标分子匹配;进而可以利用配体交换反应在金属纳米颗粒表面包裹TDBC分子薄膜,实现表面等离激元-分子激子的强耦合.     

金属纳米颗粒增强太阳能电池光吸收效应研究

采用Mie理论,对球形纳米金属颗粒进行数值计算,研究了金属纳米颗粒在发生表面等离激元共振时表现出的散射效应.改变金属材料类型或者颗粒尺寸大小,金属纳米球的散射效率均发生不同程度的变化.这一现象表明:金属纳米颗粒的散射效应受材料类型和尺寸大小的影响显著.计算结果表明,半径为100nm的Ag纳米颗粒在发生表面等离激元共振时,散射效率最高,吸收效应最弱.     

石墨烯量子点二聚物的等离激元激发

基于含时密度泛函理论,研究了石墨烯量子点二聚物的等离激元激发.当2个石墨烯量子点靠近,若量子点间的间隙较大,通过电容性相互作用时,石墨烯量子点二聚物的低能等离激元共振模式随着间隙的减小发生红移.进一步减小间隙时,由于电子的隧穿,二聚物的等离激元共振模式发生了改变,杂化等离激元共振模式形成.杂化等离激元共振模式随着间隙的减小继续红移.石墨烯量子点二聚物等离激元共振模式的演化规律不依赖于石墨烯量子点的形状.     

基于表面等离激元的量子相干效应的理论研究

起源于金属中自由电子集体振荡的表面等离激元,具有超小的光学模式体积和亚波长局域的近场增益,为纳米尺度上研究光和物质相互作用带来新的机遇．共振的纳米金属结构的近场区域,具有各向异性的珀塞尔系数,并且可以为量子体系提供近场激发．我们理论上演示了基于表面等离激元结构的单分子共振荧光、原子布居数的本征量子拍频及其在表面等离激元结构中的纳米尺度上的实现、表面等离激元诱导的各向异性珀塞尔系数导致的亚波长尺度自发辐射谱线的变化．这些结果在超紧凑的有源量子器件中有潜在应用．     

石墨烯微米带THz SPPs的激发及场分布特性研究

表面等离激元可以突破衍射极限,具有强局域性,在传感、起偏、吸收、分束等方面具有广泛的应用前景.目前,太赫兹波段的表面等离激元器件研究大多是在远场光谱方面,其近场特性的研究有待更进一步深入.本文基于石墨烯微米带结构,研究了太赫兹表面等离激元的激发及场分布特性.本文设计了能够通过太赫兹波激发表面等离激元的石墨烯微米带结构,数值计算了其表面等离激元的场分布,并制备了石墨烯微米带器件,利用透射式太赫兹近场显微镜激发并测量了石墨烯微米带的表面等离激元,对共振失谐对等离激元场分布的影响进行了探究.研究结果为石墨烯表面等离激元器件在太赫兹生物传感、安全检测、高数据率通信等方面的应用提供了相关指导.     

Synthesis and Largely Enhanced Nonlinear Refraction of Au@Cu_2O Core-Shell Nanorods

Au@Cu_2O core-shell nanorods with tunable thickness of Cu_2O shell were synthesized and their linear and nonlinear optical responses were investigated. Two transverse plasmon resonance peaks were observed when the Au nanorods were coated with Cu_2O shells, which were adjusted by the Cu_2O shell thickness. The nonlinear absorption of the Au@Cu_2O nanorods is enhanced by 5 times at the longitudinal plasmon resonance wavelength compared with that of bare Au nanorods. More intriguingly, largely enhanced nonlinear refraction and suppressed nonlinear absorption at the transverse plasmon resonance wavelength were observed in the Au@Cu_2O nanorods. Our findings indicate the existence of strong local field enhancement at the interface between the Au core and the Cu_2O shell, which would provide a promising strategy in designing plasmonic nonlinear nanodevices with good nonlinear figures of merit.     

Synthesis and Largely Enhanced Nonlinear Refraction of Au@Cu<Subscript>2</Subscript>O Core-Shell Nanorods

Au@Cu₂O core-shell nanorods with tunable thickness of Cu₂O shell were synthesized and their linear and nonlinear optical responses were investigated. Two transverse plasmon resonance peaks were observed when the Au nanorods were coated with Cu₂O shells, which were adjusted by the Cu₂O shell thickness. The nonlinear absorption of the Au@Cu₂O nanorods is enhanced by 5 times at the longitudinal plasmon resonance wavelength compared with that of bare Au nanorods. More intriguingly, largely enhanced nonlinear refraction and suppressed nonlinear absorption at the transverse plasmon resonance wavelength were observed in the Au@Cu₂O nanorods. Our findings indicate the existence of strong local field enhancement at the interface between the Au core and the Cu₂O shell, which would provide a promising strategy in designing plasmonic nonlinear nanodevices with good nonlinear figures of merit.     

Near-infrared absorption imaging and processing technologies based on gold nanorods

Noble metal nanoparticles with localized surface plasmon resonance (LSPR) properties are widely used as optical sensors in biochemical detection and medical diagnosis. In this paper, we propose an effective determination method to measure the LSPR absorption intensity of gold nanorods (GNRs). A near-infrared (NIR) imaging system is established, and an NIR absorption image of the multiple samples of the colloidal GNRs is captured. Then, the LSPR absorption intensities of these samples are obtained by calculating the average grayscale of the target areas based on the NIR image processing technology. By using this method, the LSPR absorption intensities of the multiple samples are determined all at once, and their accuracy is as high as that obtained by using spectrophotometry. These results suggest that this method is an efficient multi-channel determination technique with high-throughput sensing applications.     

Au/Si基底上电沉积Pt纳米层的衰减全反射表面增强红外吸收光谱

以一氧化碳为探针分子,研究了在金/硅基底上合理电沉积形成的铂纳米薄层的衰减全反射表面增强红外吸收效应．与外反射红外吸收光谱测得的本体铂电极表面上一氧化碳最大吸收峰强相比,铂纳米薄层的红外吸收增强了约10倍;与文献上的有关薄膜的反常红外效应相比,其峰的强度相当,但方向上却无倒转或出现双极．可应用于诸如甲醇电催化氧化的吸附中间体的灵敏检测．铂纳米膜的红外吸收增强,可能与其本身表面等离子振荡的激发有关．     

基于SPR的液体折射率检测研究

精确的折射率测量可以深入的了解介质微小的物理或者化学变化。提出一种基于Kretschmann棱镜结构的SPR折射率检测方法。首先利用Mathematica软件重点分析Kretschmann模型结构下待测样品折射率变化对表面等离子体共振吸收峰的影响,得到吸收峰随样品折射率的变化关系。在此基础上,构建Kretschmann模型并进行了酒精与水混合溶液的折射率测量。最后得出该方法能够有效检测到样品反射谱曲线,且与理论曲线趋势基本一致,在1.33~1.36折射率范围内检测的灵敏度可达86.88 deg/RIU。本研究方案对研制表面等离子体共振折射率传感器具有良好的价值。     

银纳米粒子的消光光谱与粒子形状的关系

先利用离散偶极子近似(Discrete Dipole Approximation,DDA)的方法,分别计算置于空气中的球形、不同长径比的椭球形和棒形银纳米粒子的消光光谱.计算结果表明:球形纳米粒子仅存在单个等离子体共振尖峰;而椭球状和棒状粒子则存在横向和纵向两个等离子体共振峰;并且横向峰的变化不甚明显,而纵向峰会随粒子长径比的增大而线性地红移.再结合Gans的解析理论,分析等离子体共振的机理,并研究纵向等离子体共振峰随着粒子长径比的增大而红移的现象.     

Optical properties of silver nanoplates synthesized by photoinduced method

Silver nanoplates were synthesized in aqueous solution by photoinduced chemical reduction method with tungsten lamp as light source. The growth process was analyzed and characterized. The linear absorption spectra showed that, along with the growth process, the surface plasmon resonance of silver seed nanoparticles at 395 nm decreased gradually, while a new plasmon band at 740 nm corresponding to silver nanoplates appeared and increased gradually. Z-scan technique was used to explore the nonlinear optical properties of silver nanoplates. The results displayed that with the reaction time increases from 0 h to 24 h, the value of nonlinear absorption (NLA) coefficient and the value of nonlinear refraction (NLR) index of the products increased from 0 to 3.167 cm/GW and from 0.64×10^?4 to 6.83×10^?4 cm²/GW, respectively.     

纳米半球壳结构光学调谐特性分析

利用离散偶极近似法,理论研究了颗粒几何结构参数和物理特性对金纳米半球壳颗粒消光特性的影响.结果表明,随着壳层厚度的增大,消光共振波长先发生蓝移而后再红移,共振波长转向时对应的壳层厚度随内核材料及外界环境介电常数和颗粒间距的增大而增大.利用等离激元杂化理论和相位延迟效应对该现象进行了解释.     

用有效介质理论模拟Ag/AAO纳米有序阵列复合结构光学常数

运用Maxwell—Garnett有效介质理论，计算了Ag／阳极氧化铝（AAO）纳米有序阵列复合结构的光学常数（250～2000nm波段），探讨了Ag组分的体积分数对Ag／AAO光学常数的调制作用和Ag纳米粒子的长径比对其表面等离子共振吸收的影响．模拟结果表明，随着Ag组分体积分数的增加，在小于450nm波段，Ag／AAO复合结构的介电函数实部和折射率均逐渐减小，而介电函数虚部和消光系数逐渐增大；在大于450nm波段，Ag／AAO复合结构的介电函数实部、介电函数虚部及折射率均逐渐增大，消光系数则变化较小．模拟结果显示出Ag纳米粒子的长径比与复合结构表面等离子共振吸收峰位有较强的相关性．另外，理论模拟预期透射谱也与实验透射谱变化趋势一致．