对氨基苯甲酸分子在银表面多相吸附及氯离子影响的SERS研究

研究对氨基苯甲酸(PABA)在银表面上的吸附动力学过程以及氯离子对其的影响,发现PABA在银表面上呈多相吸附。与匀相吸附的情况相似,表面形态的差异较大地改变吸附速率常数,而对多相因子的影响不明显。氯离子的竞争吸附改变PABA吸附的多相性质,随着氯离子浓度的增加,PABA分子从多相吸附逐渐转变为匀相吸附。根据吸附等温线估算了PABA的吸附能,U≈-9.6kJ/mol。结果分析进一步证实:化学吸附时多相吸附意味着表面上存在非单一的吸附形式。 关键词：     

氯离子对银胶中表面增强喇曼散射效应的影响

讨论氯离子对银胶体系中对氨基苯甲酸(PABA)和吡啶(pyr)的表面增强喇曼散射(SERS)效应的影响。观察PABA在银胶中的SERS,氯离子的影响以及SERS强度-时间关系。发现氯离子的竞争吸附破坏PABA分子的类固相吸附并伴随着分子吸附状态的改变,从而导致SERS强度的减弱。研究PABA/银胶与pyr/银胶混合后添加氯离子的影响。同时观察氯离子对银胶中PABA和pyr光吸收的影响。发现氯离子对银胶中SERS的影响主要是化学增强。     

利用表面增强喇曼散射研究银表面上结晶紫分子的吸附

以表面增强曼散射为测量手段，详细讨论结晶紫分子在银镜表面上的吸附动力学。发现结晶紫的吸附是匀相的；表面形态的差异仅影响吸附速率常数，不改变多相因子（ｍ＝１）和脱附速率常数（ｋｄ＝０）。利用吸附等温线估算结晶紫分子在银镜上的吸附能，Ｕ≈５０ｋＪ／ｍｏｌ。不同银镜上ＣＶ分子的吸附能相同；但吸附位置密度有差异，银镜的增强效果与此有关。     

二苯基乙二胺在银胶表面吸附的表面增强拉曼光谱研究

以银纳米粒子作为SERS活性基底,研究了二苯基乙二胺(DPEDA)在银表面的吸附行为,并研究了溶液的pH值和DPEDA的浓度对吸附构型的影响。对比DPEDA的Raman和SERS谱图,可以认为DPEDA是通过氮原子的孤对电子吸附在银胶表面。在酸性介质中DPEDA的氨基被质子化生成胺正离子,导致DPEDA不容易吸附到银胶表面,所以DPEDA的SERS信号强度随着溶液酸性的增加而减弱。DPEDA的浓度变化对其吸附构型中芳香环的取向影响不大,但是其C-N键与表面的角度会有一定的变化。从SERS光谱得到的信息可以加深我们对DPEDA修饰的金属催化剂的多相不对称催化机理的认识。     

银胶和银岛膜上胸腺嘧啶的表面增强拉曼光谱对比研究

利用表面增强拉曼光谱对胸腺嘧啶在银胶和银岛膜上的吸附状态进行了对比研究.光谱分析表明,胸腺嘧啶吸附在银胶和银岛膜表面后其分子结构发生了互变异构,由原来的酮式结构变成了烯醇式结构.在银胶和银岛膜表面胸腺嘧啶主要以N(3)去质子化异构体的形式存在.胸腺嘧啶通过O(7)和N(3)倾斜地吸附在银胶颗粒表面,通过O(8)和N(3...     

表面增强的分子间能量转移效应的机理研究

对吸附于粗糙金属银表面的分子间能量转移效应的机理进行了研究.采用电磁理论,讨论了金属银表面对分子间能量转移速率的影响.结果表明,当能量供体(D)分子的辐射频率和能量受体(A)分子的吸收频率同时与银表面等离子体激发频率共振时,分子间非辐射的能量转移速率被增强10~3—10~4倍.采用表面增强喇曼散射(SERS)活性表面-银胶,测量了吸附的2,2菁染料单体分子和J聚集体分子的荧光光谱,观察到的J聚集体分子增强的592.4nm的荧光带是通过被加速的分子间能量转移过程而产生的,从而证实了表面增强的分子间能量转移效 关键词：     

结晶紫的表面增强共振拉曼光谱和银胶浓度的关系

常用的银胶一般浓度较低且不稳定,这就限制了它在表面增强共振拉曼谱(SERRS)中的应用,本文旨在探讨一种容易制备,浓度高而且特别稳定的银胶在增强结晶紫(CV)SERRS讯号方面的应用,对一定浓度的CV,我们发现只有配合适当浓度的银胶才能获得最强的SERRS的信号,这个现象是由于稳定剂(PVP)在银颗粒表面的作用造成的。     

不同的银表面上系列氨基苯甲酸的吸附行为的差别(英文)

分别以覆银的干燥滤纸和银胶溶液中的银纳米颗粒为基底,对苯甲酸的一系列氨基取代物[n -ABA(n =P ,M和O) ]进行了表面增强拉曼散射(SERS)的研究,发现PABA在两种基底上的SERS光谱差别较大,而MABA和OABA则不然,我们分析了可能的原因     

酸性金黄偶氮染料在银镜上的表面增强拉曼光谱研究

以银氨溶液和葡萄糖制备的银镜为吸附基底,获得了酸性金黄G偶氮染料在银镜上的表面增强拉曼光谱,并对其拉曼峰的归属及吸附机理进行了探讨。酸性金黄G靠静电引力和范德华力以带孤对电子的N原子垂直吸附在银镜表面,SERS强度随染料浓度的降低而降低,检出限为10-10mol/L。     

银胶中结晶紫分子吸附动力学过程及氯离子的影响

同在吸附银镜上相似，ＣＶ在银胶上均相吸附，表面形态对化学吸附的多相性无必然影响。氯离子的存在有助于银表面上产生ＳＥＲＳ活位，使ＣＶ的ＳＥＲＳ强度增强－１０＾２倍，活位上分子的喇曼散射截面较普通吸附位置上的分子增加了１０＾５倍，吸附动力学计算结果表明所有ＳＥＲＳ活位是等价的。     

STUDY OF HOMOGENEOUS ADSORPTION KINETICS OF CRYSTAL VIOLET

The adsorption kinetica of crystal violet (CV) on silver mirror and two different kinds of silver sols is studied. The adsorption of CV on silver is homogeneous. It is confirmed that the topography of the surface affects only adsorption rate constant, while it does not change heterogeneity parameter. The similar behavior of enhancement factor and adsorption rate constant of CV in the two silver sols is discussed. The adsorption energy of CV and the concentration of adsorbed sites on the surface are estimated by adsorption isotherm. It is found that the enhancement effect on the silver mirror is determined by the concentration of adsorbed sites on surface.     

氢在担载金属表面的吸附研究

应用格林函数方法在紧束缚近似下研究了氢在担载金属表面的吸附性质。采用自洽的Anderson-Newns吸附模型,对氢在Pt/ZnO,Cu/ZnO和Ni/ZnO三种担载式复合体系表面的吸附能△E、吸附态能级E_ad作了计算,并讨论了金属簿层在ZnO衬底上的沉积厚度及金属-衬底相互作用对氢在该类复合体系表面的吸附性质的影响。计算表明,金属-衬底相互作用越强,氢在Pt(Cu,Ni)/ZnO体系表面的吸附能及电荷转移量越小。金属-衬底相互作用抑制了氢在金属表面的吸附。衬底对金属表面吸附性质的影 关键词：     

Oxygen reduction reactions in the SOFC cathode of Ag/CeO2

The interactions between oxygen molecules and a silver surface or a CeO₂(111) supported atomic layer of silver are predicted using first-principles calculations based on spin polarized DFT with PAW method. The juncture between the CeO₂(111), the atomic layer of silver, and O₂ represents a triple-phase boundary (TPB) whereas the interface between silver surfaces and O₂ corresponds to a 2-phase boundary (2PB) in a solid oxide fuel cell (SOFC). Results suggest that the O₂ dissociation process on a monolayer of silver supported by CeO₂(111) surfaces (or TPB) with oxygen vacancies has lower reaction barrier than on silver surfaces (or 2PB), and the dissociated oxygen ions can quickly bond with subsurface Ce atom via a barrierless and highly exothermic reaction. The oxygen vacancies at TPB are found to be responsible for the lower energy barrier and high exothermicity because of the strong interaction between subsurface Ce and adspecies, implying that oxygen molecules prefer being reduced at TPB than on silver surfaces (2PB). The results suggest that, for a silver-based cathode in a SOFC, the adsorption and dissociation of oxygen occur rapidly and the most stable surface oxygen species would be the dissociated oxygen ion with − 0.78|e| Bader charges; the rate of oxygen reduction is most likely limited by subsequent processes such as diffusion or incorporation of the oxygen ions into the electrolyte.     

化学淀积银膜上卤素电解质对吡啶的表面增强喇曼散射(SERS)的影响

本文是载玻片上化学沉淀1000左右粗糙度的银膜,对其吡啶/KX/H_2O 体系(x=F~-,Cl~-,Br~-,I~-)的 SERS 光谱进行了实验研究。分析了不同的卤素电解质,其SERS 光谱峰值大小、位移及吸附态的变化。实验表明:适当的卤素电解质和吡啶的共吸附是产生 SERS 的必要条件。     

Study of chemisorption on silver surfaces using ultraviolet photoelectron spectroscopy (UPS)

Ultraviolet photoelectron spectroscopy (UPS) was used to study the chemisorption of halogens on stepped [3(111) × (100)] and low-index (111) silver surfaces. The initial rate of halogen adsorption using CHCl₃ exposure on the silver stepped surface is approximately twice that on the low-index surface. This indicates that steps play an important role in chemisorption even on metals with a low density of states at the Fermi level. The adsorbate-induced levels on silver were correlated with halogen p valence orbitals using model extended Hückel calculations. Changes in the silver d band are interpreted as due to p?d orbital interactions.     

Adsorption of carbon monoxide on silver/palladium alloys

The adsorption of carbon monoxide on epitaxial (100) and (111) planes of Ag/Pd alloys with definite surface compositions has been studied by means of LEED, Auger electron spectroscopy and work function measurements. The formation of ordered adsorbed structures is prevented by even small amounts of silver in the surfaces. The maximum variation of the work function with CO adsorption bears no simple relationship to the surface composition. From measured adsorption isotherms the isosteric heats of adsorption have been evaluated. For CO adsorption on pure Pd planes the adsorption energies E_ad are either constant or decrease slowly up to high coverages, whereas a continuous decrease was observed with the alloys indicating the energetical heterogeneity. The results are discussed on the basis of our knowledge about the nature of the CO chemisorption and about the electronic structure of Ag/Pd alloys.     

沉积在硅油表面上的Ag原子分形凝聚体

研究了沉积在硅油表面上的Ag原子团簇,经过随机扩散和转动,最终形成大尺度分形凝聚体的凝聚过程．研究结果表明：Ag原子团簇在这种液体基底上的转动为随机转动,转动角位移的方均值<(Δθ)²>和测量时间间隔Δt满足广义爱因斯坦关系<(Δθ)²>=4D_θΔt．随机转动系数D_θ与凝聚体面积S满足指数关系D_θ∝S^{－γ_θ,其中指数γ_θ＝2.4±0. 关键词：}     

Ab initio density functional study of O on the Ag(0 0 1) surface

The adsorption of oxygen on the Ag(1 0 0) is investigated by means of density functional techniques. Starting from a characterization of the clean silver surfaces oxygen adsorption in several modifications (molecularly, on-surface, sub-surface, Ag₂O) for varying coverage was studied. Besides structural parameters and adsorption energies also work-function changes, vibrational frequencies and core level energies were calculated for a better characterization of the adsorption structures and an easier comparison to the rich experimental data.