Cu,Zn-SOD在银电极上的原位表面增强Raman光谱

本文应用原位共焦拉曼光谱技术观察了Cu ,Zn -SOD分子在经表面增强处理后的银电极上 ,吸附状态随电位跃迁变化的过程。结果表明在 -0 2V～ 0 1V的电位区间内 ,Cu,Zn -SOD分子经由羧酸根离子吸附于银电极表面 ,而在 0 2～ 0 4V电位区间内发生脱附 ,表面吸附的物种改变为缓冲溶液中的磷酸根离子。上述结果为SOD分子在固体电极表面电子传递机制的探索提供了依据。     

现场拉曼光谱研究乙腈在金电极上的解离吸附行为

利用共焦显微拉曼系统、结合合适的电极表面粗糙方法研究了非水体系 0 1mol/LLiClO4 /CH3CN溶液中 ,乙腈分子在金表面的吸附和解离行为。结果表明非水体系中乙腈可在金表面发生还原反应 ,产物CN- 离子与电极表面作用形成的表面配合物可在较宽的电位区间吸附于电极表面。溶液中的微量水、激光照射以及电极电位均对该反应有较大的影响。通过拉曼谱图的比较得出乙腈分子解离出的CN- 在金电极表面比在银电极表面有更强的吸附作用。     

金电极上Cu,Zn-SOD的表面增强拉曼光谱

应用原位共焦拉曼光谱技术在经表面增强处理后的金电极上,观察Cu,Zn-SOD分子的吸附方式及其随电位变化的过程。实验结果表明,在400mV-700mV的电位区间内,Cu,Zn-SOD分子始终以氨基酸残基上COO-和NH2在电极表面吸附,使活性中心所处的平面远离电极表面,且随电位负移发生脱附。上述结果为解释SOD分子在金电极表面无法实现快速电子传递提供了直接依据。     

非水体系中甲酸在铂电极上催化氧化的表面增强拉曼光谱研究

采用共焦显微拉曼系统研究了甲酸在非水体系中的纯多晶铂电极上的表面增强拉曼光谱,实验发现电位较低时甲酸首先在粗糙铂电极表面生成CO中间体,当电位逐渐变正并高于0.1 V时CO开始氧化,但是此时新生成的CO足以弥补其氧化的消耗,表现在Raman强度和一定覆盖度下的耦合作用并没有减少。当电位达到约0.6 V时CO的氧化速度进一步加剧并完全氧化为最终产物CO₂。     

胞嘧啶吸附在粗糙银和金电极上的表面增强拉曼光谱

利用电化学伏安方法和表面增强拉曼光谱(SERS)技术研究了在-1.0V~0V的电位区间内胞嘧啶在粗糙银电极和金电极表面上的吸附行为。结果表明,在所研究的电位区间,胞嘧啶通过N3位垂直吸附在粗糙银和金电极表面,且当电位负移时吸附作用减弱。     

DL-2-氨基4-磺酸基-丁酸与金属离子相互作用的研究

运用傅里叶变换红外光谱技术,对DL-2-氨基-4-磺酸基丁酸(DLH)与Na+,Cu2+,Zn2+和Ni2+ 形成的配合物进行了研究,并用元素分析的方法确定配合物的组成。红外光谱显示DLH分子中的—COOH,—NH+₃和—SO-₃ 基团均可与金属离子发生直接或间接的相互作用。不同过渡金属离子与氨基、羧基相互作用的强度顺序均为： Cu2+＞Zn2+＞Ni2+,其中羧基与不同离子可能采取了不同的配位方式。     

拉曼光谱法研究纳米结构多孔ZnO微球的合成机理

利用拉曼光谱方法,对柠檬酸钠辅助水热合成纳米结构多孔ZnO微球的机理进行了研究。样品的拉曼光谱特征显示,多孔ZnO微球中存在Zn-柠檬酸配合物;分析表明反应溶液中柠檬酸钠水解产生的柠檬酸根与Zn2+结合形成Zn-柠檬酸配合物,该配合物化学吸附在Zn(OH)₂晶核的(204)和(503)晶面,使Zn(OH)₂晶核择优生长形成纳米薄片状结构;水热过程中Zn(OH)₂微晶团聚形成纳米片状结构多孔Zn(OH)₂微球并以沉淀析出。研究发现吸附在薄片表面的Zn-柠檬酸配合物提高了Zn(OH)₂微晶的热稳定性,使得Zn(OH)₂的分解温度高于200 ℃,加热到300 ℃后Zn(OH)₂完全分解获得纳米结构多孔ZnO微球。     

2-噻吩甲酸在Fe3O4@Ag基底上的吸附及表面增强拉曼光谱

采用共沉淀法合成Fe₃O₄纳米颗粒,再以柠檬酸三钠还原AgNO₃获得了具有SERS活性的Fe₃O₄@Ag磁性纳米复合材料。基于密度泛函理论(DFT)的量子化学计算方法和表面增强拉曼光谱(SERS)技术,从理论计算和实验测定表征探讨了2-噻吩甲酸(2-TCA)在Fe₃O₄@Ag表面的吸附行为和增强效应。结果表明:理论计算得到的拉曼光谱与实际测得的常规拉曼光谱基本一致,而在DFT理论计算中所键连的Ag原子数越多,与实测值就越接近。溶液的浓度和pH对拉曼增强效果有很大的影响,当溶液的pH=3且浓度为1×10^-4 mol·L^-1时有最大拉曼增强效应。峰强随2-TCA浓度的增加呈现先增大后减小的趋势,浓度过大会导致大量2-TCA分子吸附聚集在Ag表面形成局部"拥堵",阻碍了激发光尤其是光谱信号的散射通过,从而减弱了拉曼增强效应。pH的变化使溶液中2-TCA分子形态发生改变,结构形态不同,其在Ag表面的吸附方式也不同。中性C₄H₃SCOOH分子以环上S:形式垂直吸附键合在Ag表面,形成S—Ag配位键而产生SERS光谱。-1价C₄H₃SCOO^-离子以S—Ag配位和O—Ag共价"双键合"侧卧方式共同吸附在Ag表面而产生SERS光谱。在Ag表面,以单独S—Ag配位键吸附或键合的能力比S—Ag配位和O—Ag共价共同吸附方式要弱,但其产生的SERS信号更强,故2-TCA中性分子比2-TCA^-离子更有利于SERS的产生。随着pH值的增加,溶液中的2-TCA由中性分子逐渐转化为-1价的C₄H₃SCOO^-离子,因而在pH>3以后,拉曼增强效应逐步减弱。     

硫代水杨酸在银表面的化学吸附及其表面增强拉曼光谱研究

采用电化学法对Ag电极粗糙活化,进而对含巯基基团的硫代水杨酸(TSA)进行表面增强拉曼光谱(SERS)研究。研究表明,溶液浓度与pH对增强效应影响显著,1×10-3 mol·L-1与pH 4分别为增强效应的最佳浓度与酸度。浓度增大由于空间位阻等因素影响而增强效应急速下降。由TSA化学吸附所产生的S—Ag峰位基本不随pH改变;但pH对峰强度有显著影响。经对TSA在不同pH下的分布和机理研究表明,TSA是通过中性C₆H₄(COOH)SH分子中的硫醇端基脱H后与活化的Ag表面进行吸附,形成S—Ag化学键而产生SERS光谱。在较强碱性条件下负一价的C₆H₄(COO-)SH 可能与OH- 形成竞争吸附而不易产生SERS;同时吸附基团巯基对羧基振动谱峰的变化以及对苯环共轭体系中的电子云分布有很大影响。     

表面增强拉曼光谱和电化学方法研究中性条件下咪唑对镍电极的缓蚀作用

利用表面增强拉曼光谱技术(SERS)研究了咪唑在镍电极表面的吸附机理和吸附方式,并分别比较了镍电极在加入咪唑前后溶液中的循环伏安曲线和极化曲线,计算了其缓蚀效率。结果表明,在镍电极表面,咪唑起到了较好的缓蚀效果;在研究电位区间内所得的SERS谱图中,面内振动峰占据了主导地位,咪唑是以垂直略带倾斜的方式吸附在镍电极表面的;而N—H面内弯曲振动峰(1 173 cm-1)的出现和pH值接近中性的研究体系证明了咪唑是以中性咪唑分子的形式存在;低波数区N—Ni伸缩振动峰(214 cm-1)的出现进一步验证了咪唑通过N原子与镍电极表面略带倾斜的吸附方式。     

In situ nucleation and growth of silver nanoparticles in membrane materials: a controllable roughened SERS substrate with high reproducibility

A controllable roughened silver surface with high surface‐enhanced Raman scattering (SERS) activity and high reproducibility has been developed in this study. This silver surface was prepared by silver nucleation in polyelectrolyte multilayers (PEMs) and silver‐enlarged growth. First, the small Ag nuclei were synthesized by NaBH₄ in situ reduction of Ag ions on a surface of PEMs. Then the small Ag nuclei formed were effectively enlarged by using a mixture of commercially available reagents named Li Silver . The optical properties and morphologies of the silver substrates have been investigated by ultraviolet–visible (UV–vis) spectroscopy and atomic force microscopy (AFM). The UV–vis and AFM results revealed that the small Ag nuclei separately appeared on the PEMs after NaBH₄ in situ reduction. The size of the enlarged Ag nanoparticles can be easily controlled with the immersing cycle in Li Silver. 4‐Mercaptopyridine (4‐MPY) and Rhodamine 6G (R6G) have been used as Raman probes to evaluate the properties of the new SERS substrates. It has been found that the enhancement factor of R6G reached ∼10⁹ after treatment in Li Silver. Reproducibility has been investigated using the SERS signal intensity at 1094 cm⁻¹ of 4‐MPY. Signals collected over multiple spots within the same substrate resulted in a relative standard deviation (RSD) of 6.38%, while an RSD of 10.33% was measured in signals collected from different substrates. Copyright © 2008 John Wiley & Sons, Ltd.     

N-甲基咪唑与2,2''-联吡啶在铜表面共吸附的SERS研究

采用电化学现场表面增强拉曼光谱(SERS)分别研究了非水体系中N-甲基咪唑(NMIM),2,2’-联吡啶(2,2-’bipy)在铜电极表面的吸附行为以及两者的共吸附行为。结果表明在非水体系中,NMIM可在很宽的电位区间内稳定地吸附在金属表面,而2,2-’bipy在一个相对较窄的电位区间内能稳定地吸附在金属表面。当两者共存时存在竞争吸附和共吸附行为,较负的电位下主要以NMIM吸附为主,在略偏负的电位区间内以2,2-’bipy吸附为主,而正电位区间两者在金属表面共吸附,NMIM倾斜吸附在金属表面,而2,2’-bipy以顺式结构垂直吸附在金属表面。     

杀线威在Fe_3O_4/Ag纳米磁粒上的吸附及表面增强拉曼光谱研究

采用共沉淀法合成了Fe_3O_4磁性纳米颗粒,进一步以柠檬酸三钠还原法制备出了具有SERS活性的Fe_3O_4/Ag磁性包覆修饰材料,用紫外可见吸收光谱、能谱及透射电镜对结构与形貌进行表征,发现所制备的Fe_3O_4/Ag纳米材料粒径约为30~60nm,形貌规整接近球形,经测试Fe_3O_4/Ag材料很容易被磁铁收集,能够满足分散萃取再收集的需要。根据密度泛函理论(DFT)对杀线威(Oxamyl)、Oxamyl-Ag和OxamylAg4进行了理论结构优化计算,得到了杀线威的理论拉曼光谱和与Ag表面增强拉曼光谱及其谱峰的归属,结合表面增强拉曼光谱(SERS)测定,研究了杀线威在Fe_3O_4/Ag表面的吸附行为和增强效应,测算得到杀线威在Fe_3O_4/Ag表面上的增强因子为2.08×105。研究表明:理论计算的杀线威拉曼光谱与测定的拉曼光谱具有较好的一致性,DFT理论计算中发现研究分子与活性Ag原子作用越多,与实测值常规拉曼NRS越接近;杀线威以双键侧N原子和S原子与Fe_3O_4/Ag表面吸附作用为主;双键侧N优先与Ag吸附成键后,整个分子靠近Ag表面,最终使得双键侧N原子与S原子共同吸附在Ag表面;Fe_3O_4/Ag磁性纳米复合材料具有显著的富集吸附和拉曼增强作用;可利用其作为拉曼基底,以实现SERS光谱法对杀线威农残的快速分析检测。     

Surface-enhanced Raman scattering study of silver deposition on thin Alq3 layers

Surface-enhanced Raman scattering (SERS) spectroscopy is applied to study in situ the interface formation of silver on thin Alq₃ films. The changes in the frequencies of Alq₃ vibrational modes are moderate and their line-shape is preserved upon Ag deposition. Moreover, a good correspondence appears between the SERS and powder spectra and frequencies predicted by density functional calculations for the meridianal isomer. The behaviour of Raman spectra indicates that no chemical interaction occurs between the Ag atoms and Alq₃ molecules.     

Identification of species formed after pyridine adsorption on iron,cobalt, nickel and silver electrodes by SERS and theoretical calculations

The adsorption of pyridine (py) on Fe, Co, Ni and Ag electrodes was studied using surface‐enhanced Raman scattering (SERS) to gain insight into the nature of the adsorbed species. The wavenumber values and relative intensities of the SERS bands were compared to the normal Raman spectrum of the chemically prepared transition metal complexes. Raman spectra of model clusters M₄(py) (four metal atoms bonded to one py moiety) and M₄(α‐pyridil) where M = Ag, Fe, Co or Ni were calculated by density functional theory (DFT) and used to interpret the experimental SERS results. The similarity of the calculated M₄(py) spectra with the experimental SERS spectra confirm the molecular adsorption of py on the surface of the metallic electrodes. All these results exclude the formation of adsorbed α‐pyridil species, as suggested previously. Copyright © 2009 John Wiley & Sons, Ltd.     

苯并三氮唑对铜和铁缓蚀作用的拉曼光谱研究

本文利用现场拉曼光谱研究了中性含氯离子溶液中苯并三氮唑在铜和铁电极表面的吸附以及成膜行为,结果表明苯并三氮唑能强烈地化学吸附于铜电极和铁电极表面,形成类似［Ｍｎ（ＢＴＡ）ｐ］的配合物膜,一定程度上阻止了膜内外物质的交换,对金属起缓蚀作用。另一方面两种金属表面配合物膜均具有电位依赖性：在铜电极表面,当外加电位由－０．５Ｖ负移至－０．９Ｖ时,发生了由［Ｃｕ（Ⅰ）（ＢＴＡ）］ｎ向［Ｃｕ（Ⅰ）Ｃｌ（ＢＴＡＨ）］４的转变;而在铁电极表面当外加电位由－０．６Ｖ负移至－１．２Ｖ时,最初形成的表面配合物［Ｆｅｎ（ＢＴＡ）ｐ］则很可能转变成类似于［Ｆｅｎ（Ｃｌ）ｐ（ＢＴＡＨ）ｍ］的配合物,从而使得ＢＴＡＨ对铜、铁的缓蚀能力均有所下降。     

Visible laser–induced photoreduction of silver 4‐nitrobenzenethiolate revealed by Raman scattering spectroscopy

We have investigated the photochemical characteristics of silver 4‐nitrobenzenethiolate (Ag‐4NBT) by means of Raman spectroscopy. When Ag‐4NBT is irradiated with an argon ion laser at 514.5 nm, its Raman spectrum changes over time, resulting in the production of 4NBT‐capped silver nanoparticles. The surface‐enhanced Raman scattering (SERS) spectrum of 4NBT adsorbed on those Ag nanoparticles is subsequently converted to that of 4‐aminobenzenethiol (4ABT). These surface‐induced photoreduction characteristics were investigated by monitoring the growth of Raman peaks of 4ABT as a function of the laser exposure time. Water vapor or ambient conditions were more effective than vacuum conditions for the photoreduction of 4NBT to 4ABT. Nonetheless, the occurrence of photolysis even under vacuum conditions suggests that the benzene ring hydrogen atoms might be the H‐atom source of the nitro‐to‐amine group conversion although in ambient conditions water or solvent molecules trapped inside the Ag‐4NBT should be the primary H‐atom source and facilitate the transfer of electrons, as well as the diffusion of Ag atoms to form highly SERS‐active nanoaggregates. Copyright © 2009 John Wiley & Sons, Ltd.     

Improved performance of surface‐enhanced Raman scattering on silver substrates prepared in nitric acid solutions

In this work, we propose a new electrochemical method to prepare surface‐enhanced Raman scattering (SERS)‐active silver substrates in nitric acid solutions. Experimental results indicate that the SERS intensity of adsorbed Rhodamine 6G (R6G) can be significantly increased, as compared with that of R6G adsorbed on a SERS‐active Ag substrate prepared by an electrochemical method in a chloride‐containing solution, which was generally employed in the literature. Moreover, the SERS of R6G on the newly developed substrate (prepared in a nitric acid solution) still performs well at a high temperature of 250 °C. However, the enhancement capability of the SERS‐active substrate prepared in a chloride‐containing solution is seriously destroyed at temperatures higher than 150 °C. Further investigations indicate that the oxidation states of roughened Ag substrates prepared in nitric acid solutions under different experiment conditions have less influence on the corresponding SERS performances. Instead, different surface morphologies of roughened Ag substrates and different contents of nitrogen‐containing dopping ions on the roughened Ag substrates demonstrate significant effects on the corresponding SERS performances. Copyright © 2011 John Wiley & Sons, Ltd.     

Use of atomic layer deposition to improve the stability of silver substrates for in situ,high‐temperature SERS measurements

A method to stabilize silver surface‐enhanced Raman spectroscopy (SERS) substrates for in situ, high‐temperature applications is demonstrated. Silver island films grown by thermal evaporation were coated with a thin layer (from 2.5 to 5 nm) of alumina by atomic layer deposition (ALD), which protects and stabilizes the SERS‐active substrate without eliminating the Raman enhancement. The temporal stability of the alumina‐coated silver island films was examined by measurement of the Raman intensity of rhodamine 6G molecules deposited onto bare and alumina‐coated silver substrates over the course of 34 days. The coated substrates showed almost no change in SERS enhancement, while the uncoated substrates exhibited a significant decrease in Raman intensity. To demonstrate the feasibility of the alumina‐coated silver substrate as a probe of adsorbates and reactions at elevated temperatures, an in situ SERS measurement of calcium nitrate tetrahydrate on bare and alumina‐coated silver was performed at temperatures ranging from 25 to 400 °C. ALD deposition of an ultrathin alumina layer significantly improved the thermal stability of the SERS substrate, thus enabling in situ detection of the dehydration of the calcium nitrate tetrahydrate at an elevated temperature. Despite some loss of Raman signal, the coated substrate exhibited greater thermal stability compared to the uncoated substrate. These experiments show that ALD can be used to synthesize stable SERS substrates capable of measuring adsorbates and processes at high temperature. Copyright © 2009 John Wiley & Sons, Ltd.     

基于单个花状银纳米颗粒的表面增强拉曼散射效应研究

在室温下,以硝酸银为银源,抗坏血酸为还原剂,通过调节表面活性剂聚乙烯吡络烷酮的浓度,实现对花状银纳米颗粒的可控制备。利用扫描电子显微镜、原子力显微镜、X射线衍射和X射线能谱等手段检测并分析了材料的形貌结构和成分组成。实验结果表明,当聚乙烯吡络烷酮的浓度为0.1 mol/L时,所制备花状银纳米颗粒的表面结构达到最精细的状态且颗粒的尺寸达到微米量级,适合对单颗粒进行定位与光学性质研究。以结构最优化的花状银纳米颗粒为表面增强拉曼散射基底材料,以羟基苯甲酸为探针,对单个和少数颗粒的表面增强拉曼散射效应进行了研究,并借助暗场散射光谱分析了基底的表面增强拉曼散射机理。结果显示,该花状银纳米颗粒因其独特的表面结构为拉曼信号增强提供了大量“热点”。良好的拉曼性能以及较低的制备成本表明,该新型表面增强拉曼散射基底具有很大的应用前景。