密排银颗粒薄膜的制备及其SERS应用

银纳米颗粒通过自组装形成二维结构薄膜具有独特的光学性质,其提供的大量“热点”使其成为优越的表面增强拉曼散射(Surface enhanced Raman Scattering,SERS)基底.本文采用水/正己烷界面上自组装的方法得到了由密排的银纳米颗粒构成的薄膜,并以Rhodamine 6G为探针分子,比较了不同尺寸银...     

银纳米阵列直径对SERS增强效果的影响

采用电化学沉积法分别在不同孔径的阳极氧化铝(AAO)模板上沉积一系列直径不同,排列规则的银纳米阵列。以对氨基苯甲酸(PABA)和三聚氰胺两种分子分别作为探针分子, 研究了银纳米阵列的直径大小对其表面增强拉曼散射(SERS)效果的影响。结果表明, 在波长为514.5 nm的激光激发下, 探针分子的SERS信号强度随银纳米阵列直径的改变而明显变化, 并在银纳米阵列直径约为53 nm时, SERS强度达到最大。利用电磁增强机制对此实验结果进行了分析和解释。     

金光栅/金纳米颗粒SERS基底的设计、制备及其性能

表面等离子激元（SPP）和局域表面等离子共振（LSPR）耦合产生的电场增强显著高于单纯LSPR引起的电场增强。因此一种新型高效的表面增强拉曼散射（SERS）基底是寄希望于在一种复合基底中实现SPP-LSPR耦合获得的。基于SPP-LSPR耦合机理,提出一种针对633 nm激光使用的金光栅/金纳米颗粒SERS基底的设计思路以及光栅和纳米颗粒的具体结构参数。为了验证设计方法的正确性,利用电子束光刻法和化学合成法分别制备了具有相应几何尺寸特征的金光栅和金纳米颗粒,并将它们复合在一起得到了光栅/纳米颗粒SPP-LSPR耦合型复合SERS基底,这个基底相比仅有金纳米颗粒制备的LSPR型SERS基底,在检测R6G溶液时浓度可以降低2个数量级,增强因子是后者的72倍,实验结果和时域有限差分（FDTD）法理论拟合的结果基本一致。     

修饰银电极上单壁碳纳米管的表面增强拉曼散射

本文采用修饰了银纳米颗粒的银电极作为基底,获得了高质量的单壁碳纳米管(SWCNTs)的表面增强拉曼散射(SERS)光谱。在1100~1500 cm-1范围内观测到了一组表征SWCNTs结构的新峰。修饰在银电极上的银纳米颗粒不仅可以保证SWCNTs在这一体系中吸附的紧密性,而且通过变面等离子体共振起到了电磁放大的作用。通过对银纳米颗粒修饰银电极表面SWCNTs的SERS光谱及其随电位变化的SERS光谱的研究,我们可以研究这一过程中的SERS机制。理论和实验结果表明,银纳米颗粒修饰银电极上单壁碳纳米管的SERS很有潜力成为一种检测单壁碳纳米管合成质量的新方法。     

内吞金纳米粒子的鼻咽癌细胞SERS光谱

采用内吞方法将金纳米粒子引入细胞内,测试分析单个活性CNE-1鼻咽癌细胞的常规拉曼光谱和SERS光谱,并对其进行初步谱峰归属。CNE-1细胞的常规拉曼光谱有6个主要的拉曼峰:718,1001,1123,1336,1446和1660cm-1;沉积于细胞内的金纳米粒子强烈地增强了细胞内生化物质拉曼信号,在内吞金纳米粒子的CNE-1细胞的拉曼光谱中出现了20多个SERS拉曼信号,主要拉曼峰的强度明显高于常规拉曼信号。DNA骨架振动(1026,1097,1336和1585cm-1)证明金纳米粒子通过内吞作用而进入细胞核内。结果表明,基于胶体金SERS技术可能为活性鼻咽癌细胞内生化物质的探测提供一种高灵敏的方法。     

退火法制备石墨烯-银纳米粒子及其增强拉曼实验

针对目前SERS基底上金属颗粒制备过程中存在的分布不均匀、易氧化和稳定性差等缺点,通过热蒸镀和高温退火获得分布均匀的SERS基底;同时结合石墨烯优良的光学性能、化学惰性、荧光猝灭以及本身的SERS增强等优点,制备了稳定的石墨烯-银纳米颗粒（GE/AgNPs）复合结构SERS基底。通过GE/AgNPs复合结构的拉曼光谱稳定性试验证明了石墨烯在GE/AgNPs结构中起到隔绝银纳米颗粒与空气直接接触及催化氧化银脱氧的作用,有利于SERS基底的时间稳定性。(1) 石墨烯、Ag纳米颗粒及其复合结构的制备。首先采用热蒸镀和高温退火的方法使Ag纳米颗粒均匀地沉积在SiO₂/Si基底上,再采用化学气相沉积法在Cu箔上制备少层石墨烯,并用湿法转移法将石墨烯转移到目标基底上,并实验研究了以不同的退火顺序对GE/AgNPs基底造成的影响。(2) 石墨烯、Ag纳米颗粒及其复合基底的表征。分别采用光学显微镜、扫描电子显微镜和拉曼光谱进行表征,得到转移后的纯石墨烯较完整地覆盖在SiO₂/Si基底上面,表面比较平整,但在少数地方仍然存在褶皱和杂质;SEM表征结果表明对于不同制备流程的GE/AgNPs复合结构上的Ag纳米颗粒基本呈球形。基本符合Ostwald熟化理论,通过对退火温度和时间的控制能获得平均粒径在40~60 nm的银颗粒,且分布较均匀。此外,在不同退火顺序中,石墨烯的加入对银纳米颗粒的扩散形成扩散势垒,从而出现较大的不规则的颗粒。(3) 基底稳定性试验和仿真分析。通过基底本身的Raman mapping测试,分析了石墨烯拉曼特征峰峰值和半高宽的变化,得知基底对石墨烯本身的拉曼增强效果主要来源于银纳米颗粒间的电磁场增强。同时采用浓度为10-6 mol·L-1的罗丹明6G (R6G)水溶液作为探针分子,对转移了石墨烯的GE/AgNPs复合基底和未转移石墨烯的Ag纳米颗粒基底进行了SERS稳定性实验。结果表明GE/AgNPs复合基底在1~33 d内衰减较缓慢,30 d后仍能探测到拉曼信号约为原来信号的35.1%~40.6%;而纯Ag基底上随着Ag纳米颗粒在空气中迅速氧化,基底的SERS性能显著下降,在30 d后只有原来信号的5.9%~11.3%。此外,通过实验得到覆盖了石墨烯之后的增强因子约为6.05×105。最后采用时域有限差分算法（FDTD）计算了复合结构的电磁场分布和理论增强因子,其理论增强因子可以达到5.7×105。实验和仿真结果的差异,主要是源于石墨烯的化学增强作用。     

覆银银电极上哌啶分子的表面增强拉曼散射研究

通过改进电极修饰方法,在粗糙银电极上沉积银纳米颗粒,得到了哌啶分子吸附在覆银银电极上的高质量SERS谱,并研究了电位对哌啶分子在这种覆银银电极上SERS光谱的影响。实验表明,沉积有银纳米颗粒的粗糙银电极是一种新的高效SERS活性基底,分析并解释了覆银银电极能产生极强的增强效应的可能原因。     

金纳米颗粒阵列基底的化学置换制备及其表面增强拉曼散射特性研究

表面增强拉曼(SERS)作为一种分析手段,具有高灵敏度、高选择性、高重复性、非破坏性等优点,在过去的几十年中,被广泛应用在成分检测、环境科学、生物医药及传感器等领域。其中以金、银等贵金属纳米颗粒薄膜在表面增强拉曼(SERS)活性基底方面得到了更为广泛的应用。SERS技术一个关键的因素是如何制设计并备具有大面积、高增强能力及高重复性、可循环使用的SERS基底。通常,贵金属纳米颗粒规则阵列结构的单元颗粒电磁增强特性及其颗粒间的电磁耦合增强特性的综合作用可大力提升SERS基底的探测性能。然而,利用传统微纳米加工方法如光刻、电子束光刻等方法制备得到的贵金属纳米阵列结构的表面粗糙度不够理想。结合光刻与化学置换方法制备金纳米颗粒四方点阵列孔洞结构,并研究其作为SERS基底的电磁增强特性。具体研究利用光刻法在硅衬底上制备了规则排列的四方点阵列孔洞结构,用磁控溅射在其表面镀上金属铁膜;接着在衬底上旋涂浓度为1.893 8 mol·L-1的氯金酸液膜,在孔洞内铁和氯金酸发生置换反应,进而孔洞生成金纳米颗粒,最终得到金纳米颗粒四方点阵SERS活性基底。采用罗丹明6G(R6G)分子作为探测分子测试不同金纳米颗粒阵列结构基底的SERS谱。实验结果表明,随着化学置换反应时间的延长,金纳米颗粒排列更加紧凑有序,SERS谱增强性能更好。     

片状三角形银纳米颗粒的自组织行为与光学特性

用化学方法制备了一种规则的片状三角形银纳米颗粒，边长为100±10nm，厚度约为30nm.紫外可见光谱分析表明了三角形银纳米颗粒形貌的完整性.颗粒表面修饰的有机分子，使三角形银纳米颗粒在碳膜上自组织形成二维单层膜，在硅片上形成高取向银膜，该银膜对吡啶分子具有很强的表面增强拉曼散射效应，增强因子可达108.     

片状三角形银纳米颗粒的自组织行为与光学特行

用化学方法制备了一种规则的片状三角形银纳米颗粒,边长为100±10nm,厚度约为30nm.紫外-可见光谱分析表明了三角形银纳米颗粒形貌的完整性.颗粒表面修饰的有机分子,使三角形银纳米颗粒在碳膜上自组织形成二维单层膜,在硅片上形成高取向银膜,该银膜对吡啶分子具有很强的表面增强拉曼散射效应,增强因子可达108.     

基于粒子群算法的Pt-Pd合金纳米粒子的稳定结构研究

Pt-Pd合金纳米粒子相对于Pt及Pd单晶纳米粒子均具有更好的催化活性和选择性, 研究它的稳定结构对进一步了解催化性能具有重要意义. 本文采用粒子群算法和量子修正Sutton-Chen多体势对不同尺寸、 不同组成比例的二十四面体Pt-Pd合金纳米粒子的结构稳定性进行研究. 结果表明: Pt-Pd合金纳米粒子中Pt原子趋向于分布在纳米粒子内层, 而Pd原子趋向于分布在纳米粒子外层, 且Pt, Pd原子的分布越对称有序, 其能量越低, 结构越稳定; 随着Pt原子比例的增加, 三种不同尺寸的合金纳米粒子的Warren-Cowley化学短程有序值都逐渐升高, 即纳米粒子更趋向于偏聚分布状态; 在相同比例下, 小尺寸纳米粒子的偏聚程度比大尺 寸纳米粒子的大. 关键词： 合金纳米粒子 粒子群算法 稳态结构     

高指数晶面Au-Pd纳米合金粒子的稳定结构研究

基于蒙特卡罗方法, 本文采用了紧束缚势和量子修正Sutton-Chen型多体势两种势能函数对具有不同比例、不同尺寸二十四面体Au-Pd合金纳米粒子的稳定结构、表面原子分布、核壳分布和化学短程序值进行了研究分析. 结果表明: 两种势函数得到的表面原子分布趋势一致, 即Au-Pd合金纳米粒子中的Au原子趋向于分布在纳米粒子的外层, 而Pd原子趋向于分布在纳米粒子的内层, 这有利于降低纳米粒子的总能; 在Au原子比例较小时, 两种势函数下得到的稳定结构均呈现出核壳分离的结构, 随着Au比例的增大, 紧束缚势函数下得到的纳米粒子稳定结构将趋向于洋葱状的多壳层的结构; 相比于紧束缚势, 量子修正Sutton-Chen型多体势作用下得到的Au-Pd纳米粒子的稳定结构偏聚程度更高.     

Preparation of stable suspensions of gold nanoparticles in water by sonoelectrochemistry

Stable suspensions of gold nanoparticles in water were prepared with high yield by a novel one-step ultrasound assisted electrochemical process. Various strategies based on the addition of either tailor-made polymers or mixtures of commercially available polymers, in the electrochemical bath have been found successful to avoid nanoparticles aggregation commonly observed by sonoelectrochemistry. alpha-Methoxy-omega-mercapto-poly(ethylene oxide) or poly(vinyl pyrrolidone)/polyethylene oxide mixtures were able to build up a coalescence barrier around the gold nanoparticles. The results showed that the size of the gold nanoparticles could be easily tuned between 5 nm and 35 nm by simple control of the electrochemical parameters, i.e. the deposition time (T(ON)) from 10 ms to 20 ms. The properties of as-prepared gold nanoparticles were compared to the ones of gold colloids prepared by the more conventional wet nanoprecipitation method using chemical reductive agents.     

Preparation of CoFe alloy nanoparticles with tunable electromagnetic wave absorption performance

CoFe alloy nanoparticles with different particle sizes were successfully prepared by hydrogen-thermal reduction of CoFe₂O₄ microspheres at different temperatures. It was found that the real part of the permeability of the CoFe alloy nanoparticles increased with the decrease of the particle size, and accordingly the reflection loss (RL) peak moved towards the low-frequency region. The maximum RL of the coating based on CoFe alloy nanoparticles exceeded −23 dB, and a wide effective absorption band width (RL≤−10 dB) of about 6 GHz was simultaneously achieved. The EMA performance was confirmed to be tunable by the control of the absorber's particle size, and thus a new clue for the design of the EMA applications was supplied.     

Preparation and application of polymer-grafted magnetic nanoparticles for lipase immobilization

Functionalized superparamagnetic particles were prepared by graft polymerization of glycidyl methacrylate and methacryloxyethyl trimethyl ammonium chloride onto the surface of modified-Fe₃O₄ nanoparticles. The resultant particles were characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The results indicate that the polymer chains had been effectively grafted onto the surface of Fe₃O₄ nanoparticles. The functionalized particles remained dispersive and superparamagnetic. Lipase was immobilized on the magnetic particles under mild conditions by electrostatic adsorption and covalent binding with the activity recovery up to 70.4%. The immobilized lipase had better thermal stability compared to free lipase.     

Synthesis and application of iron-filled carbon nanotubes coated with FeCo alloy nanoparticles

FeCo alloy nanoparticles were coated onto the iron-filled carbon nanotubes by an electroless plating method. As-prepared samples were then annealed at different temperatures. The morphologies and structures of the samples were characterized, and the relationship between the soft magnetic properties and the Fe/Co ratios of the samples was established. The microwave absorbing characteristics of the samples were also evaluated. The results show that the soft magnetic characteristics of iron-filled carbon nanotubes can be improved after being coated with FeCo alloy nanoparticles and then heat treated, which results in more effective microwave absorption.     

Electron microscopy and EXAFS studies on oxide-supported gold-silver nanoparticles prepared by flame spray pyrolysis

Gold and gold-silver nanoparticles prepared by flame spray pyrolysis (FSP) were characterized by electron microscopy, in situ X-ray absorption spectroscopy (XANES and EXAFS), X-ray diffraction (XRD) and their catalytic activity in CO oxidation. Within this one-step flame-synthesis procedure, precursor solutions of dimethyl gold(III) acetylacetonate and silver(I) benzoate together with the corresponding precursor of the silica, iron oxide or titania support, were sprayed and combusted. In order to prepare small metal particles, a low noble metal loading was required. A loading of 0.1-1 wt.% of Au and Ag resulted in 1-6 nm particles. The size of the noble metal particles increased with higher loadings of gold and particularly silver. Both scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDXS) and X-ray absorption spectroscopy (XAS) studies proved the formation of mixed Au-Ag particles. In case of 1% Au-1% Ag/SiO₂, TEM combined with electron spectroscopic imaging (ESI) using an imaging filter could be used in addition to prove the presence of silver and gold in the same noble metal particle. CO oxidation in the presence of hydrogen was chosen as a test reaction sensitive to small gold particles. Both the influence of the particle size and the alloying of gold and silver were reflected in the CO oxidation activity.     

Preparation, characterization and MRI application of carboxymethyl dextran coated magnetic nanoparticles

Superparamagnetic nanoparticles functionalized with carboxymethyl dextran (CM-dextran) were synthesized by a two-step method. First, the magnetic nanoparticles (MNPs) coated with dextran (M_w ≈ 20000) were prepared by co-precipitation of Fe²⁺ and Fe³⁺ ions. Then, dextran on the surface of MNPs reacted with monochloroacetic acid (MCA) in alkaline condition. The influences of temperature and reactant concentration on the amount of -COOH on the surface of nanoparticles were systematically studied. The obtained MNPs coated with CM-dextran were stable over the entire range of pH and NaCl concentration. The MRI experiment indicated that the CM-dextran MNPs could potentially be used as MRI contrast agents for magnetic resonance molecular imaging.     

Preparation and characterization of smart polymer brush-modified magnetic nanoparticles for biomedicine application

This paper investigates synthesis and characterization of smart polymer brush-modified magnetic nanoparticles (SPB-MNPs). Magnetic nanoparticles (MNPs) modified with poly(poly(ethylene glycol) monomethacrylate (poly(PEGMA)) brush were first functioned with activated pyridyldithio. Then, MNPs functioned with pyridyldithio (MNPs-PEG-PDT) were conjugated with 4-diamino-6-mercaptopyrimidine (DMP) to form SPB-MNPs via stimuli-responsive disulfide linkage. Fourier transform infrared spectra (FTIR) was used to monitor the preparation process of MNPs-PEG-PDT. MNPs-PEG-PDT is very highly reactive toward DMP. The disulfide linkage of SPB-MNPs can be cleaved by reduced glutathione (GHS). The concentration of GHS plays an important role in controlling the cleaved efficiency. The optimum concentration of GHS to release DMP is in the millimolar range.     

磁性核壳纳米粒子的制备及其在分离和光谱检测中的应用

磁性及其核壳复合纳米粒子由于在不同领域中具有广泛应用而受到研究者的极大关注,总结了磁性及磁性核壳纳米粒子常见的制备方法及各自的特点,并重点讨论了其在磁分离及光谱检测方面的应用,也介绍了本课题组在纳米粒子合成及应用方面所做的一部分工作。最后对磁性纳米粒子中存在的问题进行了探讨,并对其应用前景进行了展望。