Laser-MBE of nickel nanowires using AAO template: a new active substrate of surface enhanced Raman scattering

The highly ordered anodic aluminum oxide (AAO) template was fabricated using aluminum anodizing in electrolytes with two-step method, which apertures were about 50-80nm. The nickel nanowires with about 40-70nm in diameter was prepared on the AAO template by laser-MBE (molecular beam epitaxy). And high quality Raman spectra of SudanII were obtained on the glass covered with the nickel nanowires. On the nickel nanowires there are both surface enhanced Raman scattering (SERS) and tip enhanced Raman scattering (TERS). The new observations not only enlarge the range of SERS applications, but also imply a possible new enhancement mechanism. Otherwise the Raman and SERS frequencies of SudanII molecule were calculated using, respectively, DFT and B3PW91.     

Ag核Au壳双金属复合纳米线的制备及其表面增强拉曼光谱研究

采用氧化铝模板结合交流电沉积技术制备纯银纳米线, 然后通过化学还原方法, 并控制加入的金盐的量, 在已制备好的银线表面包裹不同厚度的金壳层, 得到具有核壳结构的Ag_核Au_壳复合纳米线. 采用电子显微镜(SEM, TEM)和表面增强拉曼光谱对该复合结构纳米线进行相关表征, 纳米线的表面形貌与加入的金盐的量有关. 以苯硫酚(TP)和对巯基苯胺(PATP)为探针分子, 研究了此类复合纳米线的表面增强拉曼散射效应. 并以PATP在金银纳米线表面吸附的表面增强拉曼光谱的差别为探针, 表征了复合纳米线表面金的包裹程度, 结果表明一定厚度的包裹程度可制备无针孔效应的核壳结构金银复合纳米线.     

三维树枝状银薄膜的可控生长及其在表面增强拉曼光谱中的应用

通过电流置换反应制备了树枝状银纳米薄膜。在反应过程中通过控制反应时间和硝酸银的浓度,得到了不同形貌、分布和密度的树枝状银薄膜,从而得到了具有不同SERS性能的树枝状银纳米薄膜。选取了具有最佳SERS性能的树枝状银纳米薄膜对罗丹明6G进行了微量检测、再现性检测和稳定性检测,其检测限可达到1×10~(-11) mol·L~(-1),具有优良的再现性和良好的稳定性。     

Synthesis and photoluminescence of the Y2O3:Eu3+ phosphor nanowires in AAO template

The monodisperse array and nanowires of Y₂O₃:Eu³⁺ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol–gel method. Scanning electron microscope (SEM) images indicated that Y₂O₃:Eu³⁺ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y₂O₃:Eu³⁺ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra of Y₂O₃:Eu³⁺/AAO composite films were measured. The characteristic red emission peak of Eu³⁺ ion attributed to ⁵D₀→⁷F₂ transition in Y₂O₃:Eu³⁺/AAO nanowires broadened its halfwidth.     

ZnO-聚苯胺同轴纳米线及其列阵的制备和表征

以阳极氧化铝膜 (AAO)作模板 ,制备聚苯胺 (PANI)纳米管和PANI纳米管列阵 ;同时利用溶胶_凝胶法制备ZnO_PANI同轴纳米线和同轴纳米线列阵 .PANI纳米管和ZnO_PANI同轴纳米线的形貌通过透射电子显微镜表征 .PANI纳米管的外径约 3 0nm ,内径约 1 0nm ;ZnO_PANI同轴纳米线直径约 60nm .实验发现 ,较之ZnO纳米线 ,同轴AAO模板中纳米线列阵的可见光发射谱带兰移 ,强度显著增强 ,这可能和PANI链上的NH基团与表面Zn2 +离子之间的相互作用有关 ,以及由于ZnO纳米微粒在PANI上富集、PANI的光生载流子部分转移给ZnO微粒所致 .实验还发现分散在NaOH溶液中的同轴纳米线 ,其可见光发射谱带比AAO模板中同轴纳米线的谱带兰移更甚     

Facile fabrication of silver nanoparticles on silicon for surface‐enhanced infrared and Raman analysis

A facile and economic method to fabricate and immobilize silver nanoparticles on a thin Si wafer (AgNP/Si) is reported for an analytical template in ambient environment by surface‐enhanced infrared/Raman spectroscopy. The protocol involves immersion of the Si wafer in a solution containing silver nitrate and hydrofluoric acid. To screen appropriate conditions for preparing AgNP/Si for SEIRAS application, different combinations of AgNO₃ and HF solutions were examined with paranitrobenzoic acid (PNBA) used as the probe molecule in transmission measurements. These SEIRA‐active substrates were also promising for SERS application, as demonstrated with high quality SERS spectra of iron (III) protoporphyrin adlayer on AgNP/Si with a red excitation line. The AgNP/Si substrates prepared under different conditions were examined by SEM for qualitative correlation of enhancements with morphologies. Copyright © 2008 John Wiley & Sons, Ltd.     

三维树枝状银薄膜的可控生长及其在表面增强拉曼光谱中的应用

通过电流置换反应制备了树枝状银纳米薄膜。在反应过程中通过控制反应时间和硝酸银的浓度,得到了不同形貌、分布和密度的树枝状银薄膜,从而得到了具有不同SERS性能的树枝状银纳米薄膜。选取了具有最佳SERS性能的树枝状银纳米薄膜对罗丹明6G进行了微量检测、再现性检测和稳定性检测,其检测限可达到1×10^-11 mol·L^-1,具有优良的再现性和良好的稳定性。     

Surface enhanced raman and resonance raman spectroscopy in a non-aqueous electrochemical environment: Tris(2,2′-bipyridine)ruthenium(II) adsorbed on silver from acetonitrile

This letter reports the first observation of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) from the transition metal complex tris(2,2′-bipyridine)ruthenium (II), Ru(bpy)₃²⁺, adsorbed on a silver electrode from acetonitrile (ACN). The assignment of these spectra as valid examples of SERS and SERRS in a non-aqueous environment is based on the following criteria: (1) in situ demonstration of monolayer surface coverage of Ru(bpy)₃²⁺ using double potential step chronocoulometry (DPSCC); (2) the Raman signals are most intense after surface roughening by anodization; (3) the Raman spectra are potential dependent in the non-faradaic potential region; (4) the measured enhancement factors are greater ilian 10⁶; (5) the surface spectra are frequency shifted relative to their bulk counterpart; and (6) several other molecules also exhibit non-aqueous SERS and SERRS behavior. These results are highly significant in that generality of surface enhanced Raman spectroscopy has been extended into the rich domain of nonaqueous electrochemistry.     

Enhanced raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas

We report a technique for preparing metal particles of prolate spheres for surface enhanced Raman scattering (SERS) measurements. The technique is a variation of one described by Liao in which prolate silver particles were formed on a regular array of SiO₂ posts made be reactive-ion etching a thermally grown SiO₂ layer on silicon. In the present study we have used transparent fused quartz as substrates to permit optical absorption measurements. Large patterned areas (6 cm²) with a high density of posts (60/μm²) have been obtained by using silver islands as etch masks. Good SERS spectra have been obtained for benzoic acid on gold and silver microstructures in the 100 nm range produced by this method with helium-neon laser excitation as low as 0.7 mW.     

MnS纳米线阵列上MnS花状球的水热合成

通过水热处理的方法,在氧化铝模板表面生成的MnS纳米线阵列上合成了六方相MnS花状球。利用场发射扫描电镜,透射电子显微镜,高分辨透射电子显微镜,选区电子衍射和X射线衍射对制备的样品进行了分析与表征。结果表明MnS花状球是在MnS纳米线阵列上生长的,纳米线的直径为70～80nm,与氧化铝模板的孔径一致且结晶性较好。随着阳极氧化氧化铝模板(AAO)的孔洞长度的减少,MnS花状球的数量快速增加。提出了MnS复合纳米结构可能的生长机制:氧化铝模板和反应中硫脲分解产生的H2S气体对产物的最终形貌有很重要的影响。室温光致发光光谱显示在420nm处存在一个很强的MnS带边发射峰。     

An investigation of the surface-enhanced Raman scattering effect from new substrates of several kinds of nanowire arrays

Silver, titanium, nickel, and aluminum nanowire arrays with diameters from 90 to 110 nm were prepared on AAO templates by laser molecular beam epitaxy. On the several kinds of nanowire arrays, high-quality surface-enhanced Raman scattering (SERS) spectra of probe molecules of the red dye Sudan II (C(18)H(16)N(2)O) were obtained. In particular, the SERS spectrum of Sudan II on an aluminum nanowire array is reported for the first time.     

Ag Nanoparticles Decorated CuO@RF Core-Shell Nanowires for High-Performance Surface-Enhanced Raman Spectroscopy Application

Vertical-aligned CuO nanowires have been directly fabricated on Cu foil through a facile thermal oxidation process by a hotplate at 550 °C for 6 h under ambient conditions. The intermediate layer of resorcinol–formaldehyde (RF) and silver (Ag) nanoparticles can be sequentially deposited on Cu nanowires to form CuO@RF@Ag core-shell nanowires by a two-step wet chemical approach. The appropriate resorcinol weight and silver nitrate concentration can be favorable to grow the CuO@RF@Ag nanowires with higher surface-enhanced Raman scattering (SERS) enhancement for detecting rhodamine 6G (R6G) molecules. Compared with CuO@Ag nanowires grown by ion sputtering, CuO@RF@Ag nanowires exhibited a higher SERS enhancement factor of 5.33 × 10⁸ and a lower detection limit (10⁻¹² M) for detecting R6G molecules. This result is ascribed to the CuO@RF@Ag nanowires with higher-density hot spots and surface-active sites for enhanced high SERS enhancement, good reproducibility, and uniformity. Furthermore, the CuO@RF@Ag nanowires can also reveal a high-sensitivity SERS-active substrate for detecting amoxicillin (10⁻¹⁰ M) and 5-fluorouracil (10⁻⁷ M). CuO@RF@Ag nanowires exhibit a simple fabrication process, high SERS sensitivity, high reproducibility, high uniformity, and low detection limit, which are helpful for the practical application of SERS in different fields.     

Template induced sol-gel synthesis of highly ordered LaNiO3 nanowires

The highly ordered LaNiO₃ nanowires of the rare-earth perovskite-type composite oxide were controlled synthesized within a porous anodic aluminum oxide (AAO) template by means of sol-gel method using nitrate as raw materials and citric acid as chelating agent. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the obtained LaNiO₃ nanowires had a uniform length and diameter, which were determined by the thickness and the pore diameter of the applied AAO template. The results of X-ray diffraction (XRD) and the selected-area electron diffraction (SAED) indicated that the LaNiO₃ nanowires were perovskite-type crystalline structures. Furthermore, X-ray photoelectron spectroscopy (XPS) and the energy dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric LaNiO₃ was formed.     

3D aluminum/silver hierarchical nanostructure with large areas of dense hot spots for surface‐enhanced raman scattering

Plasmonic nanomaterials possessing large‐volume, high‐density hot spots with high field enhancement are highly desirable for ultrasensitive surface‐enhanced Raman scattering (SERS) sensing. However, many as‐prepared plasmonic nanomaterials are limited in available dense hot spots and in sample size, which greatly hinder their wide applications in SERS devices. Here, we develop a two‐step physical deposition protocol and successfully fabricate 3D hierarchical nanostructures with highly dense hot spots across a large scale (6 × 6 cm²). The nanopatterned aluminum film was first prepared by thermal evaporation process, which can provide 3D quasi‐periodic cloud‐like nanostructure arrays suitable for noble metal deposition; then a large number of silver nanoparticles with controllable shape and size were decorated onto the alumina layer surfaces by laser molecular beam epitaxy, which can realize large‐area accessible dense hot spots. The optimized 3D‐structured SERS substrate exhibits high‐quality detection performance with excellent reproducibility (13.1 and 17.1%), whose LOD of rhodamine 6G molecules was 10^?9 M. Furthermore, the as‐prepared 3D aluminum/silver SERS substrate was applied in detection of melamine with the concentration down to 10^?7 M and direct detection of melamine in infant formula solution with the concentration as low 10 mg/L. Such method to realize large‐area hierarchical nanostructures can greatly simplify the fabrication procedure for 3D SERS platforms, and should be of technological significance in mass production of SERS‐based sensors.     

Ni-Pt multilayered nanowire arrays with enhanced coercivity and high remanence ratio

Highly ordered Ni-Pt multilayered nanowire arrays have been fabricated using a porous anodic aluminum oxide (AAO) template by pulse electrodeposition. The cylindrical Ni nanoparticles with different lengths and diameters in these arrays were characterized by transmission electron microscope (TEM) and alternating-gradient magnetometer (AGM) measurements. Magnetization measurements revealed that an array of such nanowires with 20-nm diameters has an enhanced coercivity (ca. 1169 Oe) and a high remanence ratio (ca. 0.96).     

利用模板法制备Ag纳米线

利用阳极氧化铝（AAO）作为模板,制备出高定向的Ag纳米线．Ag纳米线的形貌由环境扫描电镜证实,并通过X-射线能谱（EDX）、X-射线粉末衍射谱（XRD）测试手段进行了表征．     

Growth and characterization of ZnO nanowire arrays electrodeposited into anodic alumina templates in DMSO solution

ZnO nanowire arrays were grown by potentiostatic cathodic electrodeposition on aluminum anodic oxide template (AAO) from dimethyl sulfoxide (DMSO) solutions containing zinc chloride and molecular oxygen as precursors. The nanowires presented high aspect ratio and exhibited a very high crystallinity with a wurtzite crystal structure with preferential orientation along the (0001) crystallographic axis. Chronoamperometric experiments were performed on gold bulk electrodes in order to model this preferential mode growth of ZnO nanowires, which has not been previously reported for similar precursors in DMSO solution. The analysis of the corresponding chronoamperograms revealed that chloride ions influence the oxide nucleation and growth mechanism. It was found that in the absence of KCl as a supporting electrolyte, the data fitted an instantaneous three-dimensional diffusion-controlled (IN-3D)_diff nucleation and growth mechanism (NGM). The presence of KCl, instead favored a progressive three-dimensional (PN-3D)_diff NGM. With these results, a model for the more complex nanowire’s growth inside the pores of the AAO template is proposed.     

Glucose‐induced and fructose‐induced deboronation reaction of 4‐mercaptophenylboronic acid assembled on silver investigated by surface‐enhanced Raman scattering

We examined the deboronation reaction of 4‐mercaptophenylboronic acid (4MPBA) via fructose and glucose on silver surfaces by means of surface‐enhanced Raman scattering (SERS) at the excitation wavelengths of 488, 514, and 633 nm. The SERS spectra on silver nanoparticles clearly exhibited specific spectral signatures of thiophenol (TP) peaks, indicating a deboronation reaction of 4MPBA on the surfaces, whereas no strong TP peaks were observed on gold nanoparticles. The vibrational bands at 417, 999, 1021, and 1574 cm^?1 in the Ag SERS spectra could correspond to the in‐plane aromatic ring modes in TP. X‐ray photoelectron spectroscopy also supported the surface reaction on Ag by referring the B1s peaks at ~193 eV. The ratiometric Raman measurements of the band at 1574 cm^?1, with respect to that at 1587 cm^?1, revealed fructose and glucose quantification in the concentration range of 1–10 mm . We did not identify such changes for mannose, sucrose, and sialic acid. The SERS peaks of 4MPBA on roughened Ag plates also exhibited TP bands to show the time‐dependent spectral change. Our findings indicate that the deboronation of 4MPBA and conjugation with fructose and glucose may be facilitated efficiently on silver surfaces for their quantification. Copyright © 2016 John Wiley & Sons, Ltd.     

Ultrasensitive SERS Detection of TNT by Imprinting Molecular Recognition Using a New Type of Stable Substrate

We report herein a method for the ultra‐trace detection of TNT on p‐aminothiophenol‐functionalized silver nanoparticles coated on silver molybdate nanowires based on surface‐enhanced Raman scattering (SERS). The method relies on π‐donor–acceptor interactions between the π‐acceptor TNT and the π‐donor p,p′‐dimercaptoazobenzene (DMAB), with the latter serving to cross‐link the silver nanoparticles deposited on the silver molybdate nanowires. This system presents optimal imprint molecule contours, with the DMAB forming imprint molecule sites that constitute SERS “hot spots”. Anchoring of the TNT analyte at these sites leads to a pronounced intensification of its Raman emission. We demonstrate that TNT concentrations as low as 10^?12 M can be accurately detected using the described SERS assay. Most impressively, acting as a new type of SERS substrate, the silver/silver molybdate nanowires complex can yield new silver nanoparticles during the detection process, which makes the Raman signals very stable. A detailed mechanism for the observed SERS intensity change is discussed. Our experiments show that TNT can be detected quickly and accurately with ultra‐high sensitivity, selectivity, reusability, and stability. The results reported herein may not only lead to many applications in SERS techniques, but might also form the basis of a new concept for a molecular imprinting strategy.     

Surface enhanced Raman scattering of ammonia

A surface enhanced Raman scattering (SERS) spectrum of 0.5 M NH₃ in 4.0 M KCl has been observed on a silver electrode. An approximate enhancement factor of 3 × 10⁵ is calculated, and additional evidence for the enhanced nature of the spectrum is provided by the observation that totally symmetric vibrations are depolarized and by the strong potential dependence of the intensity of surface lines. Assignments have been given to the SERS lines with the low-frequency lines assigned to a AgCl and AgN stretch. The positive shift of the maximum of the intensity versus voltage curve with a lower laser excitation frequency is taken as evidence for the occurrence of a charge transfer process from ammonia to the silver electrode. The fact that the SERS spectrum of NH₃ on Ag can only be observed at large electrolyte concentrations is attributed to the breaking of hydrogen bonding at the electrode-solution interface.