一种新型的通用的SERS基底-核壳结构纳米子

为了进一步来提高SERS基底和分子的普适性,本文采取了一种"借力"的方法,设计合成了金核过渡金属薄壳(Au@Pd,Au@Pt,Au@Ni,Au@Co)的核壳结构纳米粒子,借用底层高SERS活性的金核强的电磁场来增强过渡金属表面吸附分子的SERS信号,使得过渡金属表面的增强因子可达104-105。系统地开展了不同壳层厚度及相同壳层厚度下金核大小对SERS活性影响的研究,发现随着壳层厚的增加SERS活性迅速衰减,而且当金核为120-140 nm时可以得到最强的增强。     

水雾包裹沙尘颗粒核壳结构的散射特性研究

基于离散偶极子近似法(DDA),对水雾包裹沙尘颗粒的核壳结构光学特性进行研究,计算了长短轴比例为2∶1的椭球形粒子的核壳结构内、外层厚度及散射角度变化对光散射特性的影响。结果表明,内核大小不变,外层厚度由1.2 μm增大到4.8 μm,核壳双层颗粒散射系数和消光系数由3.4和3.43降低到2.543和2.545,且散射相对强度也明显增大。外层厚度不变,内核厚度由0.6 μm增加到2.4 μm,散射系数和消光系数由3.105和3.111变化为2.76和2.9;可见外层厚度对核壳双层颗粒散射特性的影响更大,这是由于散射光主要与外层物质相互作用引起的。散射相对强度随波长的增加而降低,随核壳结构尺度的增加呈现递增的规律。该结果对大气中气溶胶和水雾共同作用时的散射特性,激光在其中的传输特性等研究有参考价值。     

核/壳结构ZnS : Mn/CdS纳米粒子的制备及发光

利用溶剂热法制备了Mn离子掺杂的ZnS纳米粒子(ZnS : Mn),利用沉淀法对ZnS ∶ Mn纳米粒子进行了不同厚度的CdS无机壳层包覆。采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)及光致发光(PL)光谱等手段对样品进行了表征。TEM显示粒子为球形,直径大约在14~18 nm之间。由XRD结果可以看出CdS壳层的形成过程受到了ZnS ∶ Mn核的影响,导致其结晶较差。XRD和XPS测量证明了ZnS : Mn/CdS的核壳结构。随着CdS壳层的增厚,样品的发光强度呈现一直减弱的现象。     

CdSe/ZnSe核-壳结构纳米粒子合成新方法

报道用“一步”合成新方法制备了CdSe/ZnSe核-壳结构的发光纳米粒子.该方法是将锌的前驱体注入表面Se富集的CdSe发光纳米粒子溶液中,通过Zn²⁺与Se共价键结合,从而在CdSe发光纳米粒子的表面形成ZnSe壳.分别通过X射线粉末衍射、光电子能谱、透射电镜、紫外-可见吸收光谱和光致发光光谱,对核-壳结构的发光纳米粒子的结构及光学性质进行了表征.结果表明,以较宽带隙的ZnSe在较窄带隙的CdSe纳米粒子表面形成的壳层有效地钝化了CdSe纳米粒子的表面缺陷,明显地提高了室温下CdSe纳米粒子的光致发光效率.X射线粉末衍射表明随着Zn²⁺的不断注入,CdSe/ZnSe的衍射峰逐渐移向ZnSe衍射峰.光电子能谱数据显示,Zn2p的双峰分别位于1020,1040eV附近,通过与体材料ZnO相比,确定为Zn²⁺的光电子发射,说明Zn是以共价键形式存在于CdSe纳米粒子的表面.透射电镜照片显示纳米粒子具有良好的单分散性,核-壳结构的发光纳米粒子直径较CdSe核的直径明显增加.     

银/二氧化钛核壳纳米颗粒对碲化镉纳米晶的荧光增强研究

利用新合成的复合纳米结构银/二氧化钛核壳纳米颗粒,研究了金属银纳米颗粒对碲化镉纳米晶层荧光的增强情况.结果表明,这种新型复合金属纳米结构能极大地增强发光纳米晶层的荧光强度.银/二氧化钛核壳纳米颗粒是以水合肼、硝酸银和四异丙氧基钛为原材料,利用胶体化学法在水溶液中合成.透射电子显微镜图片表明这种新合成的银/二氧化钛纳米材料基本上呈球形,有较为明显的核壳结构,中间黑色的核是银纳米颗粒,外层颜色较浅部分是二氧化钛壳层.另外,包裹二氧化钛壳层后,银纳米颗粒的表面等离子吸收带从409 nm红移至430 nm,也证实了这种新型核壳纳米材料的形成.将此合成方法得到的银/二氧化钛纳米颗粒和碲化镉纳米晶用旋转涂覆方法进行直接组合后,得到了银纳米颗粒对碲化镉纳米晶荧光的明显增强,并对其增强的物理过程进行了讨论.这种能够增强荧光团发光的新型复合银纳米结构将在发光器件、荧光成像、生物探测等方面具有一定的应用价值.     

核壳结构CdS/ZnS纳米微粒的制备与光学特性

用微乳液法制备CdS纳米微粒 ,以ZnS对其进行表面修饰 ,得到具有核壳结构的CdS/ZnS纳米微粒 .采用X射线衍射 (XRD)、透射电镜 (TEM )表征其结构、粒度和形貌 ,紫外 可见吸收光谱 (UV)、光致发光光谱(PL)表征其光学特性 .制得的CdS近似呈球形 ,直径为 3.3nm ;以XRD和UV证实了CdS/ZnS核壳结构的实现 .研究了不同ZnS壳层厚度对CdS纳米微粒光学性能的影响 ,UV谱表明随着壳层厚度的增加纳米微粒的吸收带边有轻微的红移 ,同时短波吸收增强 ;PL谱表明壳层ZnS的包覆可减少CdS纳米微粒的表面缺陷 ,带边直接复合发光的几率增大 ,具有合适的壳层厚度时发光效率大大提高 .     

金银核壳结构复合纳米颗粒的消光特性研究

利用离散偶极近似(Discrete Dipole Approximation-DDA)算法,从理论上模拟分析了金银核壳结构复合纳米颗粒的消光光谱以及不同核壳厚度、不同介质折射率情况下峰位的变化情况。研究结果表明,随着壳层厚度的增加,复合纳米颗粒的消光谱线先逐渐形成两个与单质金属纳米颗粒相似的消光峰,后又逐渐合为一个半峰宽度较宽的消光峰;在不同介质环境中复合纳米颗粒的消光峰都随着介电常数的增大出现红移;无论是作为核层还是壳层,银对总体消光谱线的作用都要比金强。     

SiO_2/Ag核壳结构纳米粒子的制备及其表面荧光增强

以罗丹明B掺杂的SiO2球为核,通过化学还原的方法制备了二氧化硅/银核壳结构复合纳米粒子。采用透射电镜(TEM)、紫外-可见-近红外(UV-Vis-NIR)分光光度计和荧光分光光度计对二氧化硅/银核壳结构纳米粒子的表面形貌、表面等离子共振和表面荧光增强特性进行了研究和表征。结果表明,二氧化硅/银核壳结构纳米粒子的表面等离子共振峰具有明显的可调谐性,且其表面荧光增强强烈依赖于银壳层的表面等离子共振,随银壳层厚度的增大而增强。     

核-壳结构的ZnS∶Cu/ZnS纳米粒子的制备及发光性质研究

制备了核-壳结构的ZnS∶Cu/ZnS纳米粒子以及普通的没有壳的Cu2 掺杂的ZnS纳米粒子,研究了ZnS无机壳层对ZnS∶Cu纳米粒子发光性质的影响。透射电子显微镜、激发光谱和发射光谱的研究表明,后加入的Zn2 离子在已经形成的ZnS核表面生长,形成ZnS壳层;而适当厚度的ZnS壳层可以钝化粒子表面,减少无辐射复合中心的数目,抑制表面态对发光的不利影响,提高ZnS∶Cu纳米粒子中Cu2 离子在450 nm左右的发光强度。     

利用核壳结构实现纳米颗粒的多色上转换发光

将多色荧光标记技术应用于生物信息检测可实现快速、实时、同步大规模检测目标生物分子的目的,利用上转换纳米粒子作为多色荧光探针可有效地避免生物组织自荧光对检测信号的影响。本文制备了具有核-壳结构的稀土氟化物纳米粒子,并通过在核与壳不同位置共掺杂不同浓度的敏化离子和发光离子来改变发光离子各发射峰之间的相对强度。利用不同颜色和强度的发射光谱实现了纳米粒子的多色上转换发光。利用透射电子显微镜成像、X射线衍射分析、发光光谱等测量手段对多色上转换发光纳米粒子进行了形貌、结构和上转换发光性质的表征。实验结果表明,具有核-壳结构的纳米粒子尺寸小于30 nm,呈球形。在980 nm红外光激发下,纳米粒子呈现从红色到蓝紫色的颜色可变的上转换发光。     

High-order plasmon resonances in an Ag/Al2O3 core/shell nanorice

Using numerical simulation, we investigate the high-order plasmon resonances in individual nanostructures of an Ag nanorice core surrounded by an Al2O3 shell. The peak positions of localized surface plasmon resonances （LSPRs） are red-shifted exponentially with the increase of the dielectric shell thickness. This is due to the exponential decay of electromagnetic field intensity in the direction perpendicular to the interface. This exponential red-shift depends on the wavelength of the resonance peak instead of the resonance order. In addition, we find that the LSPRs in an Ag nanorice of 60-nm width can be perfectly described by a single linear function. These features make nanorice an ideal platform for sensing applications.     

极化子效应对ZnS/CdSe核壳量子点光吸收系数的影响

在有效质量近似下,利用量子力学密度矩阵理论,从理论上研究了考虑极化子效应后核壳量子点中线性、三阶非线性以及总的光吸收系数在不同条件下随入射光能量变化的关系。通过数值计算,分析了电子-LO声子和电子-IO声子相互作用对ZnS/CdSe柱型核壳结构量子点光吸收系数的影响。结果表明,极化子效应对光吸收系数有很大影响,不同声子模式对光吸收系数影响大小不同。考虑电子-LO声子后,光吸收系数被大大提高。另外,入射光强和弛豫时间对系统的吸收系数也有很大影响。     

银/硒化锌核壳结构微球对硝酸钠红外光谱特性的影响研究

利用硒化锌微球表面的银镜反应制备了银/硒化锌(Ag/ZnSe)核壳结构微球,并利用扫描电镜(SEM)、X射线衍射(XRD)以及傅里叶变换红外光谱仪对其进行了表征,研究了Ag/ZnSe核壳结构对硝酸钠水溶液红外吸收光谱特性的影响。结果表明,Ag/ZnSe核壳结构微球使得硝酸钠反对称伸缩振动模式频率发生了明显的蓝移,振动强度有了较大程度的提高。     

Nanostructured Au/Si substrate for organic molecule SERS detection

Nanoparticles of noble metals, such as gold and silver, exhibit unique and tunable optical properties on account of their surface plasmon resonance. In particular, gold nanoparticles on silicon substrates are attractive for future nanoscale sensors and optical devices due to their resistance to oxidation and due to their electrical and optical properties. In this study, we developed a nanostructured gold/macroporous silicon (Au/PS) substrate capped with 11-mercaptoundecanoic acid (11-MUA) with ultra-sensitive detection properties achieved in characterization, an approach based on surface-enhanced Raman scattering (SERS). Surface-enhanced Raman scattering allows us to detect substances at a low concentration level and to observe structural details of a thiol molecule bonded to small film thicknesses. Raman measurements were carried out at 514 nm and 785 nm. In order to emphasize the effect of the Si microstructuration on the efficiency of this new substrate (Au/PS) proposed for SERS experiments, the same molecule (11-MUA) was adsorbed on it as well as on gold/atomically flat silicon (Au/Si) and on commercial Klarite (Mesophotonics) substrates. Systematic studies realized by Raman spectroscopy, electron microscopy, and X-ray spectroscopy show the influence of silicon substrate texturing and metallic deposition conditions, including time and temperature on the optical phenomena.     

金微/纳颗粒阵列的SERS效应研究

表面增强拉曼散射(surface-enhanced Raman scattering,简称为SERS)能够提供有机分子的指纹特征信息,且具有灵敏度高和响应时间快等优点,是一项具有发展前景的分析技术。纳米结构SERS基底是获得SERS信号的关键。本文利用简便的电沉积方法在硅片上制备大面积的金微/纳颗粒阵列。金纳米颗粒之间存在大量狭小的纳米间隙,在光激发下产生大量的SERS热点,从而具有很高的SERS灵敏度。而且,这种金微/纳结构具有高结构稳定性和化学稳定性。该结构对浓度低至10-12 M的罗丹明6G(R6G)具有很高的SERS灵敏性,且具有很好的SERS信号均匀性。利用这种微/纳结构阵列SERS基底,实现对水中低浓度农药甲基对硫磷的成功检测。这表明我们制备的金微/纳颗粒阵列在检测环境中的毒性有机物污染物方面具有潜在的应用前景。     

Graphenic Aerogels Decorated with Ag Nanoparticles as 3D SERS Substrates for Biosensing

A versatile and efficient surface-enhanced Raman scattering (SERS) substrate based on a hybrid aerogel composed of reduced graphene oxide (rGO) decorated with silver nanoparticles (AgNPs), suitable for highly sensitive label-free detection of chemical and biological species, is presented. The simple and low-cost one-pot hydrothermal synthesis allows obtaining of a 3D nanostructured spongy-like matrix that shows good spatial distribution of Ag nanoparticles in intimate contact with rGO flakes, characterized by means of several morphological, structural, and compositional techniques. The nanostructured material, tested by SERS analysis with both rhodamine 6G (R6G) and 4-mercaptobenzoic acid (MBA), shows a satisfying SERS efficiency, quantified in terms of minimum detectable concentration of 10⁻¹⁰ and 10⁻⁷ m , corresponding to on- and off-resonant excitation, respectively. The versatility of chemical/biochemical functionalization is successfully demonstrated by exploiting different routes, by immobilizing both protoporphyrin IX (PRPIX) and hemin (H) that take advantage of π−π non-covalent bonding with the graphene layers, as well as thiol-ended oligonucleotides (DNA probes/aptamers) directly grafted on the AgNPs. Finally, after the successful integration of the hybrid aerogel into a microfluidic chip, the biorecognition of miR222 is obtained demonstrating the reliability of the aerogel substrate as SERS platform for biosensing.     

Fabrication and surface-enhanced Raman scattering (SERS) of Ag/Au bimetallic films on Si substrates

Ag films on Si substrates were fabricated by immersion plating and served as sacrificial materials for preparation of Ag/Au bimetallic films by galvanic replacement reaction. The formation procedure of films on the surface of Si was studied by scanning electron microscopy (SEM), which revealed Ag films with island and dendritic morphologies experienced novel structural evolution process during galvanic replacement reaction, and nanostructures with holes were produced within the resultant Ag/Au bimetallic films. SERS activity both of sacrificial Ag films and resultant Ag/Au bimetallic films was investigated by using crystal violet as an analyte. It has been shown that SERS signals increased with the process of galvanic substitution and reached intensity significantly stronger than that obtained from pure Ag films.     

Raman of indigo on a silver surface. Raman and theoretical characterization of indigo deposited on silicon dioxide-coated and uncoated silver nanoparticles

Raman, surface-enhanced Raman scattering, and shell isolated nanoparticles-enhanced Raman scattering techniques were used to study the indigo–nanoparticle interaction nature. Silver nanoparticles were employed with and without a silicon dioxide spacer inert layer. The SERS spectral profile, obtained using silver nanoparticles, is different from the Raman one, which led to the proposition that the indigo–silver interaction is in the range of intermolecular interactions. SERS spectral reproducibility suggests identical organization and orientation of the analyte on the metal surface. The shell isolated nanoparticles enhanced Raman scattering spectrum of indigo, obtained by using silicon dioxide coated silver nanoparticles resulted similar to its Raman spectrum. This result indicates that the indigo structure is chemically unmodified by the silicon dioxide-coated silver surface. From the shell-isolated nanoparticles-enhanced Raman scattering experiments, the electromagnetic mechanism is proposed as the reason for the spectral enhancement. Theoretical calculations allow one to infer both the indigo–silver surface interaction nature and the orientation of indigo on the surface.     

水溶液银纳米晶聚集对表面增强拉曼散射的影响

由于贵金属纳米粒子独特的光学性质,基于衬底的贵金属纳米粒子薄膜表面增强拉曼散射技术在分子生物学和医学免疫分析等研究领域中显现出非常好的应用优势和潜力。本项研究工作应用柠檬酸纳作聚集剂诱导水溶液中对巯基苯甲酸修饰的Ag纳米粒子聚集,并应用以此形成的"热点"增强SERS光谱,获得了对巯基苯甲酸修饰的Ag纳米粒子聚集非常有效的4-MBA分子的SERS信号,为未来建立生物待测物的分析检测奠定前期基础。结果证明,水溶液中的Ag纳米粒子的聚集形成的"热点"具有非常好的SERS光谱增强效应。