金属纳米结构表面吸附的CO分子在外电场中的相互作用

建立金属纳米颗粒在外电场中的排列结构模型，用经典理论分析纳米结构金属表面上吸附的CO分子在外电场中的相互作用能，包括有效偶极子间的相互作用和与局域电场的相互作用，并讨论和计算了纳米颗粒表面附近的局域电场. 用Monte-Carlo方法进行数值计算和模拟，具体给出纳米颗粒表面CO分子的分布和相互作用能，表明金属表面纳米结构使CO产生凝聚，并使分子相互作用能增加，为解释异常红外吸收效应提供依据. 关键词： 纳米结构金属 吸附分子 相互作用 局域电场     

CoPt纳米棒异常红外光学性能研究

采用原位模板结合化学还原法制备了一维CoPt纳米棒,扫描电子显微镜(SEM)结果表明CoPt纳米棒平均直径为166.3 nm,长度在1.0~5.0μm之间。以CO为探针分子,在固/气界面研究了CoPt纳米棒的红外光学性质,并同本体Pt电极进行对比分析。原位固/气红外光谱结果表明,吸附态CO(COad)在本体Pt上为正常红外吸收,而CoPt纳米棒在GC基底上表现出异常红外效应(AIREs),当CoPt纳米棒负载到高反射率的金基底上可以得到相同的结论,说明CoPt纳米棒表现出异常红外效应是有材料本身的性质,与反射基底无关。论文从固/气界面进一步验证了一维纳米材料的异常红外效应,有助于加深对低维纳米材料异常红外光学性能的理解。     

金属纳米锥表面吸附分子分布的数值模拟

在均匀外电场中,将吸附在由过渡金属基底生长的纳米锥颗粒表面的CO分子等效为偶极子,在考虑偶极子与局域电场,偶极子之间色散力及偶极子与锥表面原子之间三种相互作用的情况下,给出各相互作用能的数学模型,并用Monte Carlo方法进行数值模拟,得到纳米锥颗粒表面吸附CO分子的空间分布构型.结果表明,在这些相互作用下,纳米锥表面吸附CO分子产生局部凝聚,且随着纳米锥角的变小,吸附在锥顶部的分子更加密集,导致吸附分子间相互作用更强,为解释纳米结构表面吸附体系的异常红外效应提供依据.     

分子激发中的表面等离激元增强效应

金属纳米粒子的表面等离激元增强效应是纳米科学领域的一个研究热点.针对染料分子与金属纳米粒子的耦合系统,应用偶极-偶极近似计算分子与金属纳米粒子的库仑相互作用,并应用密度矩阵理论描述在不同极化方向的电场作用下的电荷输运过程,分析了分子与金属纳米粒子在不同相对位置下分子激发态的动力学过程,发现表面等离激元的增强效应与分子和金属钠米粒子的相对位置以及等离激元的耗散系数有密切关系,详细讨论了分子与金属纳米粒子间的耦合强度、外场的极化方向、等离激元的寿命及共振激发条件对分子激发态及表面等离激元增强的影响,分析了分子-金属纳米粒子耦合系统中表面等离激元增强效应的物理本质.     

光激发作用下分子与多金属纳米粒子间的电荷转移研究

金属纳米粒子在光激发作用下的增强作用是纳米科学领域的一个研究热点. 针对分子和多个不同位形下的金属纳米粒子在光激发下的相互作用展开了理论研究. 应用密度矩阵理论描述分子和金属纳米粒子同时激发产生表面等离激元后的电荷输运过程. 研究发现, 表面等离激元增强效应与分子和各个金属纳米粒子的相对位置有密切关系. 详细分析了金属纳米粒子间的耦合强度、分子和金属纳米粒子间的耦合强度、表面等离激元能级杂化、分子激发能和外场频率对表面等离激元增强效应的影响.     

固/液界面原位红外显微镜和步进扫描时间分辨FTIR反射光谱及其在纳米材料科学中的应用

结合红外显微镜和步进扫描FTIR光谱仪 ,发展了固 /液界面电化学原位显微镜红外反射光谱和步进扫描快速时间分辨FTIR反射光谱 ,并应用于纳米材料特殊性能和电化学反应动力学的研究。研制纳米结构Pt微电极 ,获得CO吸附的红外特征随纳米结构和纳米尺度变化的原位显微镜红外谱图。利用纳米结构Pt微电极的异常红外效应 ,显著提高电化学原位红外反射光谱的灵敏度 ,获得分辨率达 5 0 μs的步进扫描时间分辨光谱。不仅发展了固 /液界面显微镜原位红外反射光谱新方法 ,并且拓展了电化学原位红外反射光谱在纳米材料科学研究中的应用。     

分子激发态光谱和动力学

分子激发态光谱和动力学对于了解分子的电子结构及电子运动、核振动和分子转动之间的相互作用有重要的意义.我们建立起了一套红外-红外双共振实验平台,开展了碱金属双原子分子微扰增强双共振研究,取得了一些重要结果.利用XUV激光结合高分辨光电子能谱的方法,我们研究了一些重要分子离子的光谱,如：CH3CN^＋/CD3CN^＋的电子运动与核振动之间的相互作用（Jahn-Teller效应）.     

Pt纳米微粒自组装体系的电化学和原位FTIR反射光谱研究

用化学还原法制备了铂金属纳米微粒 ,透射电子显微镜 (TEM)表征纳米Pt微粒的平均直径为 2 5nm。通过二硫醇将Pt纳米微粒组装到多晶金电极表面。以Fe(CN) 4- 3-6 的氧化还原作为探针反应的电化学研究表明 ,Au表面组装二硫醇后抑制了电极 /溶液界面的电子传递过程 ,而在二硫醇上再组装铂纳米微粒后 ,电子传递又可进行。运用电化学FTIR反射光谱研究了Pt纳米微粒组装电极在酸性介质中CO的吸附 ,检测到CO的线型、桥式吸附态 ,分别在 2 0 30和 184 5cm- 1 附近给出红外吸收谱峰 ,并且有增强红外效应。此外 ,还观察到Pt纳米微粒上的CO孪生吸附态。红外吸收峰位于 2 10 0cm- 1 附近。     

包埋Pt纳米粒子对金属-半导体-金属结构ZnO紫外光电探测器性能的影响

利用射频磁控溅射设备制备ZnO薄膜, 最终制备ZnO/Pt纳米粒子/ZnO 结构的金属-半导体-金属型紫外光电探测器. 研究了Pt纳米粒子处在ZnO薄膜层中的不同深度对金属-半导体-金属型紫外光电探测器响应性能的影响. 结果表明, 探测器的响应度随着Pt纳米粒子在ZnO薄膜层中所处深度的增大而升高. 在60 V偏压下, 包埋Pt最深的探测器在波长365 nm处取得响应度最大值1.4 A·W^-1, 包埋有Pt探测器的响应度最大值为无Pt 纳米粒子探测器响应度最大值的7倍. 结合对ZnO薄膜表面的表征及探测器各项性能的测试, 得出包埋Pt纳米粒子增强器件的响应性能可归因于表面等离子体增强散射.     

金属纳米椭球结构表面的局域电场和吸附分子分布

过渡金属纳米结构表面吸附CO分子时会出现异常红外效应,这一现象可以用纳米结构表面吸附分子在外电场作用下产生局部凝聚从而相互作用能增加来解释.在前期研究的基础上,给出金属基底表面生长出的纳米颗粒为椭球状颗粒的理论计算结果.基于均匀外电场中金属纳米椭球颗粒按一定对称性排列的表面结构模型,用经典电磁学理论计算了纳米椭球颗粒表面附近的局域电场.在此基础上,将吸附的CO分子等效为偶极子,在考虑了偶极子与局域电场、偶极子之间以及偶极子与金属基底三种相互作用的情况下,用Monte-Carlo方法进行数值模拟,最后给出纳 关键词： 金属纳米结构表面 纳米椭球 吸附分子 局域电场     

碱性溶液中纳米钯膜电极表面CO、CN-吸附的红外反射光谱研究

以原位ＦＴＩＲ反射光谱研究碱性介质中ＣＯ和ＣＮ＾－在纳米Ｐｄ膜电极上的吸附和共吸附,进一步揭示了纳米薄膜材料的异常红外效应和ＣＯ与ＣＮ＾－共吸附时的相互作用规律。     

Local electric field and configuration of CO molecules adsorbed on a nanostructured surface with nanocones

Based on the nanostructured surface model that the (platinum, Pt) nanocones grow out symmetrically from a plane substrate, the local electric field near the conical nanoparticle surface is computed and discussed. On the basis of these results, the adsorbed CO molecules are modelled as dipoles, and three kinds of interactions, i.e. interactions between dipoles and local electric field, between dipoles and dipoles, as well as between dipoles and nanostructured substrate, are taken into account. The spatial configuration of CO molecules adsorbed on the nanocone surface is then given by Monte-Carlo simulation. Our results show that the CO molecules adsorbed on the nanocone surface cause local agglomeration under the action of an external electric field, and this agglomeration becomes more compact with decreasing conical angle, which results in a stronger interaction among molecules. These results serve as a basis for explaining abnormal phenomena such as the abnormal infrared effect (AIRE), which was found when CO molecules were adsorbed on the nanostructured transition-metal surface.     

Monte Carlo simulations of FTIR studies during CO oxidation on a Pt/SiO2 catalyst

A Monte Carlo (MC) simulation of the reaction of CO with an oxygen covered Pt surface and oxygen with a CO covered Pt surface is presented in this paper. The effect of the adsorption, desorption, reaction, and surface migration rates on the formation of CO clusters is analyzed in terms of the CO frequency shift in the IR spectrum. The MC simulation calculates the CO frequency shifts according to a dipole-dipole interaction model. The IR frequency shifts predicted by the simulation depend on the value of the various kinetic processes considered. The simulation indicates that the CO migration on the surface is important at low pressure but is inhibited at high pressure. The IR frequency shifts predicted by the simulation agree qualitatively with experimental values obtained during CO oxidation on a Pt catalyst.     

Electric potential distribution near nanocone arrays on metal substrates

Based on the nanostructured surface model,where conical nanoparticle arrays grow out symmetrically from a plane metal substrate,a theoretical model of the local electric potential near nanocones is built when a uniform external electric field is applied.In terms of this model,the electric potential distribution near the nanocone arrays is obtained and given by a curved surface using a numerical computation method.The computational results show that the electric potential distribution near the nanocone arrays exhibit an obvious geometrical symmetry.These results could serve as a basis for explaining many abnormal phenomena,such as the abnormal infrared effects(AIREs) which are found on nanostructured metal surfaces,as well as a reference for investigating the applications of nanomaterials,such as nanoelectrodes and nanosensors.     

Surface interaction between H2 and CO2 over silicalite-supported platinum

Infrared spectroscopic evidence is presented for the formation of linearly bonded CO species, as a result of surface interaction between H₂ and CO₂ at room temperature over silicalite-supported Pt. Comparison with direct CO adsorption results suggests that the active sites for this CO₂ reaction are the corner or step sites on platinum particles. The CO formed on these active sites then migrates to other sites on the surface of Pt particles. Co-adsorbed hydrogen and water make the linearly bonded CO species more strongly adsorbed on Pt particles. However, exposure to oxygen or air at room temperature effectively removes these CO species.     

CO and O coadsorption on Pt3Sn studied by DFT: Changes in the adsorptive properties of the surface with alloying and coverage

Adsorption of CO and coadsorption of O and CO on Pt₃Sn(1 1 1) was studied using periodic DFT calculations. Calculations were performed on Pt(1 1 1) by using the same set of parameters and their results were used as reference basis. The calculations showed that the most stable configuration with the minimum energy for coadsorption of CO and O is CO adsorbed atop Pt and O adsorbed on fcc Pt2Sn hollow site and that the decrease in the adsorption strength of the system at a total surface coverage of 0.5 ML is by 0.063 eV as a result of coadsorption, with respect to the adsorption of one species individually. Results show that the interaction between the adsorbed CO and O is short range on PtSn alloy, contrary to that on pure Pt, and this is mainly related to stronger Sn–O bonds compared to Pt–O bonds which eventually reduce the surface strain at the coadsorption structure. There is a pronounced effect of total surface concentration on the adsorption energy of coadsorbed species; the adsorption strength is not directly proportional to the surface coverage but is also related to the distribution of the coadsorbed species on the surface.