Raman spectroscopy of gold nanoparticles in polycrystalline LiF film

Results of the Raman spectroscopy analysis of a new composite material based on a thin polycrystalline LiF film containing gold nanoparticles are presented. The formation of spherical gold nanoparticles in the film has been confirmed by the X-ray structural analysis and observation of the optical plasmon resonance absorption spectrum with a maximum at 534 nm. The obtained composite layers have been subjected to annealing by ruby laser (λ = 694 nm) in the spectral region on a descending long-wavelength wing of the plasmon absorption band of gold nanoparticles. Raman spectroscopy has been applied for the first time to the investigation of the modification of the shape of gold nanoparticles in LiF during laser annealing. The experimental Raman spectra are compared with calculated modes of in-phase bending vibrations generated in gold nanoparticles.     

Sensitive surface-enhanced Raman scattering substrates based on anti-pyramidal gold architectures decorated with silver nanoparticles

Abstract

A micro-structured gold surface, consisting of a periodic square–based anti–pyramidal array (Klarite) with a smooth boundary surface on which silver nanoparticles (diameter: 60?nm) were deposited, produced an active surface enhanced Raman scattering substrate. With p-aminothiophenol as a probe molecule, the Raman activity of the micro–structured surface was compared before and after deposition of the silver nanoparticles. Experimental results show that the Raman spectra on the silver/p-aminothiophenol/Klarite structure is stronger than that on the silver/p-aminothiophenol/gold film and the Raman spectra on the silver/p-aminothiophenol/gold film is stronger than that on silver/p-aminothiophenol, p-aminothiophenol/Klarite structure, p-aminothiophenol/gold film, which is confirmed by numerical simulations. A similar result is obtained with crystal violet as test molecule.     

Inkjet printed Cu(In,Ga)S<Subscript>2</Subscript> nanoparticles for low-cost solar cells

Cu(In,Ga)Se₂ (CIGSe) thin film solar cells were fabricated by direct inkjet printing of Cu(In,Ga)S₂ (CIGS) nanoparticles followed by rapid thermal annealing under selenium vapor. Inkjet printing is a low-cost, low-waste, and flexible patterning method which can be used for deposition of solution-based or nanoparticle-based CIGS films with high throughput. XRD and Raman spectra indicate that no secondary phase is formed in the as-deposited CIGS film since quaternary chalcopyrite nanoparticles are used as the base solution for printing. Besides, CIGSe films with various Cu/(In + Ga) ratios could be obtained by finely tuning the composition of CIGS nanoparticles contained in the ink, which was found to strongly influence the devices performance and film morphology. To date, this is the first successful fabrication of a solar device by inkjet printing of CIGS nanoparticles.     

Plasmon resonance modulated photoluminescence and Raman spectroscopy of diindenoperylene organic semiconductor thin film

In a comparison between a bare diindenoperylene (DIP) film and a DIP film spin-coated with a layer of gold nanoparticles, we have investigated the influence of plasmon resonances in the gold particles on spectroscopic properties of the molecular film. Under off-resonant excitation with a laser at 633 nm, the bare DIP film showed only weak photoluminescence (PL) and Raman signals, but after spin-coating gold nanoparticles on such a DIP film, we found an enhancement of both the PL and Raman signals by a factor of about 3, whereas no enhancement could be observed when the same sample was excited with laser light of 488 nm. This difference reveals that at 633 nm, plasmon resonances in the gold nanoparticles are excited, leading in turn to an enhancement of PL and Raman signals of the weakly absorbing DIP film via coupling between plasmons in the gold particles and exciton-polaritons in the molecular film. For the laser at 488 nm, due to a much larger absorption coefficient of DIP, excitons in the molecular film are directly excited, out-weighing the influence of an off-resonant coupling to the plasmon resonances in the gold particles occurring at much lower energy.     

Controlling SERS intensity by tuning the size and height of a silver nanoparticle array

It is demonstrated that the surface-enhanced Raman scattering (SERS) intensity of R6G molecules adsorbed on a Ag nanoparticle array can be controlled by tuning the size and height of the nanoparticles. A firm Ag nanoparticle array was fabricated on glass substrate by using nanosphere lithography (NSL) combined with reactive ion etching (RIE). Different sizes of Ag nanoparticles were fabricated with seed polystyrene nanospheres ranging from 430 nm to 820 nm in diameter. By depositing different thicknesses of Ag film and lifting off nanospheres from the surface of the substrate, the height of the Ag nanoparticles can be tuned. It is observed that the SERS enhancement factor will increase when the size of the Ag nanoparticles decreases and the deposition thickness of the Ag film increases. An enhancement factor as high as 2×10⁶ can be achieved when the size of the polystyrene nanospheres is 430 nm in diameter and the height of the Ag nanoparticles is 96 nm. By using a confocal Raman mapping technique, we also demonstrate that the intensity of Raman scattering is enhanced due to the local surface plasmon resonance (LSPR) occurring in the Ag nanoparticle array.     

电化学方法制备ZnO纳米颗粒掺杂类金刚石薄膜及其场发射性能研究

采用液相电化学沉积技术制备了ZnO纳米颗粒掺杂的类金刚石(DLC)薄膜, 研究了ZnO纳米颗粒掺杂对DLC薄膜场发射性能的影响. 利用X射线光电子能谱、透射电子显微镜、Raman光谱以及原子力显微镜分别对薄膜的化学组成、 微观结构和表面形貌进行了表征. 结果表明: 薄膜中的ZnO纳米颗粒具有纤锌矿结构, 其含量随着电解液中Zn源的增加而增加. ZnO纳米颗粒掺杂增强了DLC薄膜的石墨化和表面粗糙度. 场发射测试表明, ZnO纳米颗粒掺杂能提高DLC薄膜的场发射性能, 其中Zn与Zn+C的原子比为10.3%的样品在外加电场强度为20.7 V/μm时电流密度达到了1 mA/cm². 薄膜场发射性能的提高归因于ZnO掺杂引起的表面粗糙度和DLC薄膜石墨化程度的增加.     

Synthesis of graphene oxide sheets decorated by silver nanoparticles in organic phase and their catalytic activity

The graphene oxide(GO) sheets decorated by Ag nanoparticles were prepared using a liquid–liquid two-phase method at the room temperature. The synthesized samples existed in the organic phase and were characterized by X-ray diffraction, transmission electron microscopy, UV–vis spectroscopy and Raman spectra. The results demonstrate that these silver-nanoparticles with diameter of about 10 nm assembled on graphene oxide sheets are flexible and can form stable suspensions in organic phase. Raman signals of graphene oxide sheets are increased by the attached silver nanoparticles, displaying higher surface-enhanced Raman scattering activity. Furthermore, Ag/GO are found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH₄.     

银纳米粒子/碳纳米管阵列SERS基底增强因子分析和实验

为了直观、准确地定量分析表面拉曼增强散射基底结构的拉曼增强,利用磁控溅射和高温退火的方法制备了银纳米粒子修饰垂直排列的碳纳米管阵列三维复合结构样品;实验采用罗丹明6G(R6G)溶剂作为探针分子,结合共聚焦显微拉曼系统,开展了表面增强拉曼增强因子(EF)分析计算的相关实验。SEM结果表明：在有序碳纳米管阵列的表面和外壁均匀地负载了大量银纳米粒子。对退火温度为450 ℃,退火时间为30 min的样品进行了EF计算,得到其增强因子约为2.2×103,并分析了EF值低的原因主要是：在碳纳米管上溅射的银膜膜厚不均匀,导致退火后银颗粒分布不均,使得样品粗糙度值偏大,EF值较低;实验中所用的激励光源并非银纳米颗粒的优化光源。     

银纳米粒子修饰三维碳纳米管阵列SERS实验

为了使表面增强拉曼散射(SERS)基底的三维聚焦体积内包含更多的“热点”,能吸附更多探针分子和金属纳米颗粒,以便获得更强的拉曼光谱信号,提出了银纳米粒子修饰垂直排列的碳纳米管阵列三维复合结构作为SERS基底,并对其进行了实验研究。利用化学气相沉积(CVD)方法制备了垂直排列的碳纳米管阵列;采用磁控溅射镀膜方法先在碳纳米管阵列上形成一层银膜,再通过设置不同的高温退火温度,使不同粒径的银纳米粒子沉积在垂直有序排列碳纳米管阵列的表面和外壁。SEM结果表明：在有序碳纳米管阵列的表面和外壁都均匀地负载了大量银纳米粒子,并且银纳米颗粒的粒径、形貌及颗粒间的间距随退火温度的不同而不同。采用罗丹明6G(R6G)分子作为探针分子,拉曼实验结果表明：R6G浓度越高,拉曼强度越强,但是R6G浓度的增加与拉曼强度增强并不呈线性变化;退火温度为450 ℃,银纳米颗粒平均粒径在100～120 nm左右,退火温度为400 ℃,银纳米颗粒平均粒径在70 nm左右,退火温度为450 ℃的拉曼信号强度优于退火温度400和350 ℃。     

Polycarbonate nanoparticles spray coated on silicon substrate using micro-electromechanical-systems-based high-frequency ultrasonic nozzle

Mono-disperse polycarbonate (PC) nanoparticles 20 nm in diameter was spray coated on silicon substrate using a novel high-frequency ultrasonic nozzle. Specifically, Bisphenol-A polycarbonate with a molecular weight (M_w) of approximately 6.4 × 10⁴ g/mol was first dissolved in pyridine. The resulting solution was sprayed into surfactant-containing de-ionized (DI) water using a 300 kHz silicon-based multiple-Fourier horn nozzle (MFHN). As pyridine was extracted into the water, PC nanoparticles formed but remained dispersed. This suspension of PC nanoparticles was then sprayed onto a silicon substrate using a 500 kHz 3-Fourier horn nozzle. Scanning electron microscopy (SEM) of the dried substrate revealed that PC nanoparticles were spread uniformly with no aggregation.     

Self-cleaning performance of polycarbonate surfaces coated with titania nanoparticles

The effect of NaOH-etching and UVC-irradiation on the mechanical stability of TiO₂ nanoparticles on polycarbonate (PC) slides was investigated. TiO₂ nanoparticles were found to adhere more strongly on UVC-treated PC than NaOH-etched PC, caused by the increase in the hydroxyl and carboxyl groups on the UVC-treated PC. Although a mechanically strong TiO₂ film was developed on UVC-treated PC, the sheet-like wetting effect and antifogging behaviour were only observed with the film coated on NaOH-etched PC. It was also detected that the film coated onto NaOH-etched PC exhibited a more superior performance in degrading methylene blue than that in the UVC-treated PC system. Evidences from the FTIR and AFM analyses indicated that the performance of TiO₂ films was strongly depended on the leaching rate of PEG.     

Ag纳米粒子修饰聚合物纳米尖锥阵列的SERS衬底制备

表面增强拉曼散射(SERS)以其无损、超灵敏、快速检测分析等优点而备受关注,在化学和生物传感等应用领域有着极大的潜力。研制灵敏度高、重复性强、稳定性好的SERS基底,对于实现其在痕量分析、生物诊断中的实际应用具有重要意义。具有微/纳米结构的聚合物具有优异的机械性能、光学性能、耐化学性等优点。通过模板压印法,利用多孔阳极氧化铝(AAO)在聚合物聚碳酸酯(PC)表面制备一种高度有序的纳米PC尖锥阵列结构,然后通过蒸发镀膜在PC尖锥阵列上沉积一层银膜,制备了大面积Ag纳米颗粒修饰的高度有序聚合物纳米尖锥阵列。高曲率纳米针状结构顶端的银颗粒及颗粒之间狭小的纳米间隙能产生大量的SERS"热点"。这种方法得到了均匀,可重复,大面积高增强的SERS活性基底,并进一步研究了不同沉积厚度银膜的SERS特性。用扫描电子显微镜(SEM)对其进行了表征,以结晶紫作为探针分子对这种结构进行研究。结果表明:拉曼信号强度随银厚度的增加显示为先增强后减弱的趋势。基底对结晶紫的拉曼增强因子达到5.4×10~6,基底主要拉曼峰强度的RSD为10%,说明该基底具有很好的检测灵敏性和重复性。此外,基底在存放40 d后,在相同条件下仍然保持着高SERS性能,表现出很好的稳定性。整个制备过程简单易行,重复性好,制作成本非常低廉,而且能够规模化制备,可方便地作为活性基底应用于SERS研究,必将具有广阔的研究和应用前景。     

基于激光诱导水拉曼抑制法的油膜厚度测量方法研究

为了实现水体表面油膜厚度的快速测量分析,以266 nm的激光作为探测系统的激发光源,基于激光诱导水拉曼散射光谱检测技术,通过获取不同种类不同厚度油膜存在下水拉曼光谱信息,建立油膜厚度反演模型。采用高斯函数拟合法校正了荧光光谱对拉曼光谱的干扰。然后根据水拉曼抑制法结合非线性最小二乘优化算法,建立油膜厚度反演模型。结果表明：对92#汽油、0#柴油、美孚机油20w-40、壳牌润滑油10w-40、采埃孚变速箱油AG6和原油油膜能探测到的油膜厚度范围为0.19~379.22 μm。采用水拉曼光谱-油膜厚度反演模型预测油膜厚度的平均相对误差在8.14%~15.81%之间。该方法能实现实验室条件下对微米级油膜的测量。     

Photopolymerization in water of diacetylenes chemisorbed onto noble metal nanoparticles: a spectroscopic study

Gold and silver nanoparticles of different size, decorated by a diacetylenic monomer having a COOH anchor group, were prepared in aqueous dispersions. Topochemical polymerization of the colloidal suspensions was obtained by UV irradiation and studied by means of spectroscopic techniques (UV–visible absorption, IR and Raman spectroscopies). A variety of polymer phases were found in the case of silver nanohybrids. The main contribution for this investigation was supplied by the Raman spectra, which provide detailed information on the polymer forms and on the preferred conformation of the alkylic side chains. Copyright © 2009 John Wiley & Sons, Ltd.     

半胱氨酸作为耦联剂制备的纳米银膜上的SERS研究

在直流10V电压下电解聚乙烯醇和硝酸银的混合液3h制备纳米银胶,将经过半胱氨酸修饰后的载玻片浸入银胶24h制得纳米银膜。用紫外可见分光光度计对银胶进行了观测,由于其吸收峰半高宽较窄可知银胶中纳米银颗粒粒径分布较为均匀。同时,使用扫描电镜对银膜进行了表征。通过对半胱氨酸分子SERS信号的分析得出了纳米银粒子在玻璃表面上可能的组装方式。以结晶紫(Crystal Violet)和孔雀石绿(Malachite Green)作为探测分子,采用便携式拉曼光谱仪测得两种分子不同浓度下的SERS谱。发现该方法所制得的纳米银膜有很好的表面增强效果。最后分析了半胱氨酸分子SERS信号对探针分子光谱的影响。     

Chemistry and morphology of dried‐up pollen suspension residues

Pollen grains are covered with lots of different biochemical compounds, like proteins, saccharides and lipids, which are only loosely attached to the pollen. Therefore, they can be separated from the pollen by suspending them in water. Since these compounds play a key role in many atmospheric processes (e.g. cloud condensation nucleation, ice nucleation, aerial allergen exposure), their separation and analyzing are of interest. The chemical composition of whole pollen grains is compared by both Raman and infrared spectroscopy with material that could be extracted from pollen with water. The dominant signals in the pollen grain Raman spectra are those from sporopollenin and carotenoids. These bands decrease in the washing water spectra, since sporopollenin is high molecular and thus is not extractable. The released material shows in turn a chemical composition that differs significantly between species, what is quite expected, since they differ even in the optical properties of their aqueous suspensions. The FTIR spectra show some additional bands to appear in comparison to the Raman spectra. Furthermore, we investigated the pollen rupturing and material release in the aqueous suspensions by drying them up and picturing the residues with a scanning electron microscope. We saw that corn pollen ejected loads of micrometer‐sized organelles, which are most likely starch granules. The more the pollen disrupted, the more the measured samples were covered with an amorphous film, which consists of the extracted pollen material, like lipids, sugars, and proteins – the same substances we detected by spectroscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

具有窄光致发光谱的纳米Si晶薄膜的激光烧蚀制备

采用XeCl脉冲准分子激光器，在10Pa的Ar气环境下，烧蚀高阻单晶Si靶，分别在距靶3cm的玻璃和单晶Si衬底上制备了纳米Si薄膜. 相应的Raman谱和x射线衍射谱均证实了薄膜中纳米Si晶粒的形成. 扫描电子显微镜图像显示，所形成的薄膜呈均匀的纳米Si晶粒镶嵌结构. 相应的光致发光峰位出现在599nm，峰值半高宽为56nm，与相同参数下以He气为缓冲气体的结果相比，具有较窄的光致发光谱，并显示出谱峰蓝移现象. 关键词： 纳米Si晶粒 脉冲激光烧蚀 薄膜形貌 光致发光     

Influence of surface plasmon resonance wavelength on SERS activity of naturally grown silver nanoparticle ensemble

We present experimental results to quantify and optimize the surface‐enhanced Raman scattering (SERS) activity of naturally grown silver nanoparticles. Ag nanoparticle ensembles with mean equivalent radii ranging from 10.6 to 20.3 nm were prepared under ultrahigh vacuum conditions by Volmer–Weber growth on quartz plates. A tuning of the localized surface plasmon polariton resonance wavelength from 453 to 548 nm was performed by varying the morphology of the silver nanoparticles. The dependence of the SERS activity on the plasmon resonance wavelength was investigated with a Raman set‐up containing a microsystem light source with an emission line at 488 nm. Shifted excitation Raman difference spectroscopy was applied to remove the fluorescence‐based background from the SERS spectra of pyrene in water using two slightly different emission wavelengths (487.61 and 487.91 nm) of the microsystem light source. We demonstrate that the Raman activities for all SERS substrates are available in the nanomolar range in a water sample. However, the Raman activity crucially depends on the plasmon resonance wavelength of the nanoparticle ensembles. Although for an on‐resonance ensemble the limit of detection for pyrene in water is very low and was estimated to be 2 nmol/L, it increases rapidly to several tens of nanomol for slightly off‐resonance ensembles. Hence, the highest SERS activity was obtained with a nanoparticle ensemble exhibiting a plasmon resonance wavelength at 491 nm, which almost coincides with the excitation wavelengths. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of SnO<Subscript>2</Subscript> tubular nanostructures on top of a silicon nitride surface using polymeric templates and their characterization as gas sensor

Uniform polycrystalline SnO₂ microtubes formed by sintered nanoparticles (fixed to a surface or in free standing form) were obtained with the infiltration technique using SnCl₄ as precursor and a porous polycarbonate (PC) film as template. The advantage of this synthesis method was based on its simplicity, reproducibility, low cost, and the possible applicability to other complex oxides. The morphology and crystal structure of SnO₂ tubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The crystalline sizes of the nanoparticles assembled in the tube walls obtained at 600 °C were in the range of 5–7 nm, calculated from both the XRD and the TEM data. The length of the microtubes fixed to a silicon nitride surface ranged between 2 and 7 μm. Sensors fabricated with this material showed unusual sensitivity to ethanol at room temperature and fast reversible response, as compared to those obtained by the deposition of metallic tin film and further oxidation (Rheotaxial Growth and Thermal Oxidation method).     

巯基苯甲酸在电化学沉积的金/银薄膜表面的吸附行为

通过表面增强拉曼散射(SERS)技术和密度泛函理论(DFT)研究对巯基苯甲酸自组装在电化学沉积的金和银薄膜表面的吸附行为.结果表明电化学沉积的金和银薄膜是良好的SERS活性基底. 通过对巯基苯甲酸的SERS光谱分析和DFT理论计算,以及表面选择定则,得到了对巯基苯甲酸主要通过羧基自组装在电化学沉积银膜表面,并且苯环表面可能和银表面有一倾角,对巯基苯甲酸主要通过硫原子和金表面相互作用,并且苯环平面可能和金膜表面有一个倾角