自组装法制备团簇Ag纳米结构衬底及其SERS

采用自组装方法,在3-Aminopropyltrimethoxysilane(APS)分子修饰后的玻璃衬底表面,获得了二维Ag纳米结构衬底。在波长为532nm激光激发下,研究了沉积在衬底表面的Rhodamine 6G(Rh6G)分子的拉曼光谱特性。结果表明,制备的二维Ag纳米结构衬底具有强的拉曼增强特性,增强因子可以达到107倍。这说明,在外光场作用下,制备的Ag纳米结构衬底表面能够形成的强局部电磁场分布,可以有效提升探针分子的光谱辐射效率,从而获得高增强拉曼散射。     

表面增强喇曼光谱的Au@SiO2核壳纳米粒子制备北大核心

研究了核壳纳米颗粒的表面增强喇曼光谱（SERS）,并制备了不同SiO2厚度的Au@SiO2核壳纳米粒子进行喇曼光谱分析测试。首先,采用化学还原法制备出酒红色的金溶胶溶液。接着,添加不同量的正硅酸四乙酯（TEOS）制备了以Au为核、不同厚度SiO2为壳包裹的Au@SiO2核壳纳米粒子。然后,采用紫外-可见光（UV-Vis）和扫描电子显微镜（SEM）对Au@SiO2核壳纳米粒子的结构进行表征。最后,不同SiO2厚度的Au@SiO2核壳纳米粒子和未进行表面修饰的金溶胶溶液中滴入等量质量浓度为0.1 mg/L的罗丹明B,离心干燥后用喇曼光谱仪测试表面增强喇曼光谱效应。结果表明：罗丹明B的检出限可达到2.1×10^-7 mol/L,在扫描范围为300-1 800 cm^-1,激发波长为532 nm的条件下,SERS活性随TEOS用量的增加先增大后减小。TEOS的用量为120μL时,罗丹明B的表面喇曼增强效应最佳。     

自组装法制备团簇Ag纳米结构衬底及其SERS

采用自组装方法,在3-Aminopropyltrimethoxy silane(APS)分子修饰后的玻璃衬底表面,获得了二维Ag纳 米结构衬底。在波长为532nm激光激发下,研究了沉积在衬底表面的 Rhodamine 6G(Rh6G)分子的拉曼光谱特性。结 果表明,制备的二维Ag纳米结构衬底具有强的拉曼增强特性,增强因子可以达到 10⁷ 倍。这说明,在外光场作用下,制备的Ag纳米结构衬底表面能够形成的强局部电磁场分布, 可以有效提升探针分子的光谱辐射效率,从而获得高增强拉曼散射。     

C层包覆Ag纳米颗粒基底的表面增强拉曼散射研究

Ag纳米结构是最常用的表面增强拉曼散射(SERS) 活性基底,缺点是Ag的化学稳定性和 生物相容性比较差。为此,利用化学方法合成了一种新型的SERS活性基底—纳米碳层包覆的 Ag(Ag@C)纳米颗粒。利用透射电子显微镜(TEM)和紫外- 可见吸收光谱对制备的核壳结构纳米颗粒进行了表征,并研究了颗粒的SERS活性。结果表明 ,罗丹明6G(R6G)、结晶紫(CV)和孔雀石绿(MG)分子在Ag@C悬浮液中的SERS光谱强度 与在Ag胶中的SERS光谱强度相比显著增强。根据光谱 的变化规律推断,额外的增强来自于化学增强。由于C层的存在,相比于Ag纳米颗粒, Ag@C颗粒的化学稳定性和生物相容性都有所改进。     

Au纳米颗粒的形状和尺寸对表面等离子体的影响

通过调控Au纳米颗粒的形状和尺寸,研究了Au纳米颗粒的形状和尺寸与表面等离子体之间的关系。通过直流磁控溅射的方法在外延片上溅射Au薄膜,并采用快速热退火和常规热退火两种方式对其进行热退火,制备出Au纳米颗粒。使用不同热退火方式、不同热退火温度及不同Au薄膜厚度来改变Au纳米颗粒的形状和尺寸,并对Au纳米颗粒的表面形貌及它的消光谱进行了分析,对比了不同形貌的Au纳米颗粒对表面等离子体共振特性的影响。实验结果表明,使用普通热退火制备的Au纳米颗粒形状接近球体,而使用快速热退火得到的Au纳米颗粒的形状更接近棒体;随着热退火温度的升高,表面等离子体的共振波长发生红移;随着Au薄膜厚度的增加,表面等离子体的共振波长也发生红移。     

激光烧蚀Ag表面的结构表征及纳米产物的光谱应用

用Nd：YAG激光器对Ag片在二次去离子水中进行烧蚀,用原子力显微镜(AFM)和扫描电子显微镜(SEM)对Ag表面形态进行测量,发现其表面呈现具有nm量级的粗糙度。同时,在Ag片所处的液体中制备出了具有nm尺度“化学纯净”的Ag胶体系。此体系中,Ag纳米颗粒尺度分布均匀,并且具有很好的稳定性。通过用对羟基苯甲酸(PHBA)作为探针分子,对这种纯净Ag胶体系中的表面增强拉曼散射(SERS)进行研究测试发现,这种Ag胶体系是一种非常高效的SERS活性增强基底,对其原因进行了分析。     

Ag纳米颗粒有机薄膜受激辐射增强研究

为进一步降低有机半导体材料的激射阈值,文章研究利用银纳米颗粒的表面等离子体共振效应来实现对有机半导体薄膜受激辐射的增强.将制备好的Ag纳米溶液旋涂于玻璃基底上,然后在其上再旋涂PS:Alq3:DCJTB有机薄膜发光层,构成平面波导结构.用355nm波长的YAG激光泵浦样品.实验发现:相比于无Ag纳米颗粒情况,有Ag纳米...     

金属表面等离激元增强聚合物太阳电池

研究了Au纳米颗粒表面等离激元增强聚噻吩(P3HT)与富勒烯衍生物(PCBM)共混体系聚合物太阳电池的光电转换效率。Au纳米颗粒表面由双十烷基二甲基溴化铵(DDAB)修饰,能够均匀分散在活性层中。研究了Au纳米颗粒的质量分数对电池性能的影响,发现质量分数为1.2%时,电池性能最佳,转换效率高达3.76%,较未掺杂的参比电池相对提高约20%。掺入Au纳米颗粒后P3HT和PCBM共混膜光吸收显著增强,从而使电池外量子效率大大增加。电池效率的提升主要归结于Au纳米颗粒表面等离激元激发所引起的近场增强。     

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。     

贵金属纳米颗粒/石墨烯复合基底SERS研究进展

由于贵金属纳米颗粒/石墨烯复合基底可为喇曼光谱分析技术提供灵敏度高、稳定性好、生物相容性好的基底而备受关注。首先从电磁原理和化学原理两个角度出发,系统地探讨了贵金属纳米颗粒/石墨烯复合基底表面增强喇曼散射(SERS)的机理,进而概述了石墨烯及贵金属纳米颗粒的制备方法及其性能特征,并详细介绍了化学气相沉积法制备石墨烯和物理法制备贵金属纳米颗粒的过程。在此基础上,对不同贵金属纳米颗粒/石墨烯复合基底SERS的国内外研究进展进行了综合的阐述和分析,主要介绍了贵金属Ag,Au和Pt的纳米颗粒复合体系,最后对贵金属纳米颗粒/石墨烯复合基底SERS技术在各个领域的应用及其发展前景进行了展望。     

一种实现微型频率选择表面通带开关的方法

微型频率选择表面（MEFSS）基于感性表面（金属栅格）与容性表面（间隔的金属环形贴片）之间的耦合机制实现带通滤波功能。采用全波分析矢量模匹配法精确计算了耦合介质的相对介电常数εr、厚度d对MEFSS传输特性的影响：εr由3.5变为2时中心频点高漂2.8GHz,d增加0.4mm时中心频点往低频漂移1.4GHz且透过率降低2.6dB。由此可见,通过控制耦合介质厚度能够实现MEFSS通带开关的功能：当耦合介质厚度增加1mm时通带中心频点透过率降低8.173dB。在覆铜的聚酰亚胺膜上复制光刻制备感性表面、容性表面并分别置于0.2mm、1.2mm厚泡沫板两侧采用自由空间法测试了其传输特性。计算与实验结果均表明：通过控制耦合介质厚度变化能够实现MEFSS通带开关的功能,为实现有源FSS提供一种新的方向。     

First-principles of wurtzite ZnO (0001) and (0001) surface structures

The surface structures ofwurtzite ZnO(0001) and(0001) surfaces are investigated by using a first-principles calculation of plane wave ultra-soft pseudo-potential technology based on density functional theory(DFT).The calculated results reveal that the surface energy of ZnO-Zn is bigger than that of ZnO-O,and the ZnO-Zn surface is more unstable and active.These two surfaces are apt to relax inward,but the contractions of the ZnO-Zn surface are smaller than the ZnO-O surface.Due to the dispersed Zn4s state...     

Supported Faceted Gold Nanoparticles with Tunable Surface Plasmon Resonance for NIR‐SERS

A novel dry plasma methodology for fabricating directly stabilized substrate‐supported gold nanoparticle (NP) ensembles for near infrared surface enhanced Raman scattering (NIR SERS) is presented. This maskless stepwise growth exploits Au‐sulfide seeds by plasma sulfidization of gold nuclei to produce highly faceted Au NPs with a multiple plasmon resonance that can be tuned from the visible to the near infrared, down to 1400 nm. The role of Au sulfidization in modifying the dynamics of Au NPs and of the corresponding plasmon resonance is discussed. The tunability of the plasmon resonance in a broad range is shown and the effectiveness as substrates for NIR SERS is demonstrated. The SERS response is investigated by using different laser sources operating both in the visible and in the NIR. SERS mapping of the SERS enhancement factor is carried out in order to evaluate their effectiveness, stability, and reproducibility as NIR SERS substrates, also in comparison with gold NPs fabricated by conventional sputtering and with the state‐of‐the‐art in the current literature.     

单点金刚石车削技术的研究

介绍了单点金刚石车削原理,分析了单点金刚石车削技术中影响光学零件面形精度和粗糙度的重要技术因素,同时提出了相应的解决方案,并展望了单点金刚石车削技术在光学制造领域的应用前景.     

频选膜拼接工艺误差对复材天线罩电性能的影响

加载频率选择表面(FSS)薄膜的复合材料天线罩在实际制作过程中,需将若干FSS薄膜结构进行拼接以构成一个整体,FSS膜的拼接工艺误差则对天线罩的电性能产生实质性的影响。文中设计了一款X波段的A夹层平板复合材料天线罩,并建立了由拼接工艺误差带来的FSS膜搭接和FSS膜缝隙的电磁仿真模型,研究了不同拼接工艺对复合材料天线罩的透波率、电磁波传输特性的影响以及对天线辐射特性的影响。研究结果表明：天线罩中的FSS薄膜结构的拼接错位对电磁波传输影响明显,会明显降低天线主瓣增益和天线罩透波率;当入射电磁波的极化方向与FSS薄膜结构的搭接缝方向相同时,FSS膜结构对天线罩透波率影响较大,当极化方向与FSS薄膜结构的搭接缝方向垂直时,则其对天线罩透波率影响较小;两块FSS膜结构边缘搭接的相对位置和搭接距离对天线方向图有明显影响;两块FSS薄膜结构边缘无搭接且存在缝隙则对天线罩透波率影响较小。该研究对复合材料天线罩的制造工艺具有工程指导意义。     

Preparation of atomically flat surfaces on silicon carbide using hydrogen etching

Hydrogen etching of 6H- and 4H-SiC(0001) surfaces is studied. The as-polished substrates contain a large number of scratches arising from the polishing process which are eliminated by hydrogen etching. Etching is carried out in a flow of hydrogen gas at atmospheric pressure and temperatures around 1600–1700°C attained on a tantalum strip heater. Post-etching atomic force microscopy images show periodic arrays of atomically flat terraces that are a few thousand angstroms wide. These terraces are separated by steps 15 Å high in the 〈1 $ < 1\bar 100 > $ 00〉 directions. Often, the surface is seen to be faceted with steps on neighboring facets forming 60° angles and offset in the c-direction by half a unit cell. Images of incompletely etched surfaces show early stages of etching where one can see remnants of surface damage in the form of arrays of hexagonal pits. On the larger scale, the surface has a hill-and-valley type morphology. The observed features are interpreted in a model based on the symmetry of the SiC unit cell and crystal miscut.     

FDTDSIBC混合方法计算近地导线表面电流

通过在FDTD方法中引进时域表面阻抗界条件来研究瞬态电磁脉冲对有耗地面附近电缆线耦合问题。由频域表面阻抗出发通过拉氏变换得到时域表面阻抗边界条件（SIBC）,并将这种边界条件应用于FDTD方法中来模拟有耗地面的反射。计算结果表明了些方法的有效性。     

Investigation of the Surface Removal Process of Silicon Carbide in Elastic Emission Machining

Elastic emission machining (EEM) is a precise surface preparation technique, which uses chemical reactions between the surfaces of the workpiece and fine powder particles. The purpose of this study is to clarify the surface removal process of silicon carbide (SiC) in EEM. A SiC sample with a periodic step-bunched structure was prepared as the initial surface and was flattened by EEM. Optical interferometer and atomic force microscopy (AFM) observations show that the topmost areas on the periodic step-bunched structure in contact with the powder particles are preferentially removed and surface protrusion is gradually reduced as removal depth increases. Moreover, power spectral density analyses reveal that the surface is smoothed in the spatial wavelength range from 0.07 μm to 10 μm.     

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。     

Enhanced electron injection/transportation by surface states increment in mesoporous TiO2 dye-sensitized solar cells

A strategy of surface modification to the mesoporous TiO2 photoanode with hydrochloric acid treatment was used in this study, and it was found that short circuit current and photovoltaic efficiency of dyesensitized solar cells (DSSCs) were increased by 5.5% and 8.9% respectively. The improvement was attributed to the reduced impedances in the TiO2 film and at the TiO2/dye/electrolyte interface. It was showed that the increased surface electronic states could remarkably prolong electron lifetime, which was responsible for the reduction of impedances. Under these quasi-continuous states in mesoporous structure, the electron injection/transportation can be notably facilitated, which will be beneficial for the DSSC performance.