女大学生创业行为特征及成因初探

以某综合性研究型大学的在校生及毕业五年内创业学生为调查对象,采用问卷调查及数据分析的方法。调查显示：男女大学生在校期接受创业实践教育机会均等,男女参与创业实践项目比例持平,但女大学生实施创业比例小于男生,持续创业比例远低于男生,女大学生在校创业与毕业后创业比例出现断崖式跌幅;男女大学生创业行业分布差异明显,女生主要集中于传统服务业、文化创意类、互联网类、公益创意类、教育培训类等,但相对其他研究行业分布相对全面、均衡

The Charge Transfer Effect of SERS Induced by the Electrochemical Hydrogen Evolution Reaction

应用高灵敏度的共焦显微拉曼技术 ,分别研究了水体系和不同pH值的硫脲体系中电化学反应与表面增强拉曼散射 (SERS)效应之间的关系 .研究结果表明 ,在电化学析氢反应电位区 ,电荷转移增强机制起主要作用 ,使表面物种的拉曼强度显著地增强 .As one of the important mechanisms of SERS, the charge transfer (CT) enhancement requires the strong interaction of the adsorbed species with the substrate in order to permit the transition of charge between the metal Fermi level (energy state) and the molecular orbital [1] . The high enhancement needs the match of the energy gap between the Fermi level (or surface state) and the orbital energy level of the adsorbed molecules with the energy of the incident light. The electrode Fermi level is usually adjusted by the applied potential to satisfy the CT resonance. For the electrochemical reaction process, the frontier orbital energy level of the reacting surface species should be greatly different from that of the adsorbed molecules. Thus, it is interesting to test the additional SERS enhancement induced by the electrochemical reaction. In the present study, the influence of the electrochemical reaction on SERS intensity of thiourea (TU) and water adsorbed on silver electrode surfaces were investigated, respectively. The Raman experiments were performed on a confocal microprobe Raman system (LabRam I). The details of the Raman system and pretreatment of the Ag electrode can be found elsewhere [2] . The SERS spectra of TU in pH 1 and 7 are showed in the Fig. 1 (a) and (b), respectively. The major bands of TU locate at～710 cm -1 and～1 091 cm -1 . The strong 933 cm -1 band is assigned to the symmetric stretching vibration of ClO 4 - as electrolyte anion, which coadsorbed on the surface. The electrochemical measurements indicate that TU can adsorb strongly at Ag electrode in a wide potential region from -0.2 V to -1.5 V (vs SCE). It is of interest that the SERS intensity reaches the maximum at different potential in acidic and neutral solutions. In the low pH solution, one can find that when the electrode potential shifted to -0.8 V, all the band intensities increase remarkably. In the high pH solution (Fig. 1 (b)), at potentials positive of -1.0 V only solution signal can be discerned. The intensity of the surface signals underwent a sharp increase at -1.2 V. Interestingly, we found the maximum intensities in the two pH solutions have a certain relation with the occurrence of the electrochemical hydrogen evolution reaction (HER). A systematic SERS experiments were performed in solutions with pH of 2.0, 2.5, 3..0, 3.5, 4.0 and 7.0 respectively. The profiles of the integrated band intensities (～710 cm -1 ) and the potentials are shown in Fig. 2. It can be found that the maxima of the intensities are located at -0.8 V, -1.1 V for pH 1.0 and 2.0 respectively and -1..2 V for pH 2.5 ～7.0. Correspondingly, the current densities for each potential in different pH solution were presented in Fig. 3. From the two figures, it can be found that the potentials of the maximum intensity of SERS are right at the initial potentials of HER. It implies that there must have some relation between the HER and the additional enhancement of the SERS. A study on the SERS of water will be helpful for further understanding of this relation.作者联系地址：厦门大学固体表面物理化学国家重点实验室!化学系厦门361005,厦门大学固体表面物理化学国家重点实验室!化学系厦门361005,厦门大学固体表面物理化学国家重点实验室!化学系厦门361005,江西师范大学化学系!南昌,330027,厦门大学固体表面物理化学国家重点实验室!化学系厦门361005,Author's Address: 1 State Key Lab. for Phys. Chem. of Sol. Surf., Inst. of Phys. Chem. and Dept. of Chem., Xiamen Univ., Xiamen 361005, China; 2 Dept. of Chem.,

Electrocatalytic Oxidation of Formic Acid on Pt-Se Hollow Nanosphere Modified Glassy Carbon Electrodes

Corresponding authors. Email: [email protected],[email protected]; Tel:+86-13879159319.[中文文摘]以无定形硒溶胶为模板制备了不同硒覆盖度(θSe)(θSe=0.49,0.39,0.06,0)的Pt-Se和Pt纳米空球(分别记为(Pt-Se)HN和PtHN),发展了利用亚硫酸盐彻底除去核壳纳米粒子上Se的方法.对获得的纳米空球进行了形貌和结构的表征,结果表明所制备的(Pt-Se)HN粒径均匀,分散性好,球壳呈多孔结构.以其作为电催化剂制备了(Pt-Se)HN修饰的玻碳(GC)电极((Pt-Se)HN/GC),利用常规电化学方法比较该电极与PtHN/GC和商用碳载铂(Pt/C)修饰GC(Pt/C/GC)电极对甲酸的催化氧化作用,发现对甲酸氧化的活性顺序为(Pt-Se)HN/GC>PtHN/GC>Pt/C/GC.三种电极催化甲酸氧化的机理有所不同:前者更倾向于通过弱吸附中间体直接氧化成CO2的单途径机理进行,后两者则通过强吸附和弱吸附中间体的双途径机理进行.在一定Se覆盖度条件下,(Pt-Se)HN/GC对甲酸的氧化有助催化作用.[英文文摘]Platinum-selenium and platinum hollow nanospheres(denoted as(Pt-Se)HN and PtHN,respectively) with different coverages of Se(θSe)(θSe=0.49,0.39,0.06,0) were prepared using amorphous Se colloids as a sacrificial template.Sulfite was used to completely remove Se from the core-shell nanoparticles.The morphology and structure of the nanoparticles were characterized using various methods,which revealed a hollow structure with a very uniform size distribution and a porous structure on the shell.Assembly of Pt-Se hollow nanospheres ((Pt-Se)HN) on a glassy carbon (GC) electrode produced a (Pt-Se)HN/GC electrode. The electrocatalytic activity of the electrode for the oxidation of formic acid was compared with the PtHN/GC and commercial Pt/C/GC electrodes by cyclic voltammetry and chronoamperometry. The activity followed the order:(Pt-Se)HN/GC > PtHN/GC >Pt/C/GC. The electrooxidation of formic acid on (Pt-Se)HN/C, PtHN/C, and Pt/C catalysts follows different mechanisms: the former tends to directly oxidize formic acid to CO2 via weakly adsorbed intermediates, and the latter two via both weakly and strongly adsorbed intermediates.(Pt-Se)HN with a suitable selenium content showed optimal electrocatalytic activity for the oxidation of formic acid.国家自然科学基金(20663002); 厦门大学固体表面物理化学国家重点实验室基金(200511)资助项

电化学析氢反应诱导的电荷传递SERS效应(英文)

应用高灵敏度的共焦显微拉曼技术 ,分别研究了水体系和不同pH值的硫脲体系中电化学反应与表面增强拉曼散射 (SERS)效应之间的关系 .研究结果表明 ,在电化学析氢反应电位区 ,电荷转移增强机制起主要作用 ,使表面物种的拉曼强度显著地增强

Influence of annealing ambience on the formation of cobalt silicides

By using two sets of Raman systems with excitation lines of 514.5 and 632.8 nm, the influence of annealing ambience was investigated on the formation of cobalt silicides. The results show that a more uniform, compact and thermal stable cobalt silicide film can be formed in the hydrogen annealing ambience than that in the Ar annealing ambience. Two characteristic bands located at 305 and 325 cm(-1), which may be assigned to the CoSi. and COSi2, respectively, were found during the phase transition processes. The strong band which appeared at 325 cm(-1) that can only be detected with the excitation line of 632.8 nm was found to be due to the resonant Raman effect. (C) 2003 Elsevier Science B.V. All rights reserved

Au_(core)@Pt_(shell)/GC电极上甲醇解离中间体CO氧化的SERS研究

本文采用共焦显微拉曼系统对不同介质中甲醇解离中间体CO在Aucore@Ptshell/GC电极上的氧化行为进行了研究。结果显示,不论在酸性、中性还是碱性介质中,甲醇均能在Aucore@Ptshell/GC电极上自发氧化解离出强吸附中间体CO;较低电位下,CO在酸性和中性介质中以线性吸附为主,碱性介质中则以桥式吸附为主。此研究表明,电极在中性及碱性介质中对甲醇解离中间体CO的电氧化比在酸性介质中有更好的催化活性,原位表面增强拉曼光谱技术有望拓展成为研究电催化反应的有效工具

金纳米空球的合成及其SERS效应

本文利用非晶硒溶胶作模板合成了金纳米空球,采用扫描电子显微镜(SEM)、X射线衍射(XRD)及拉曼光谱对其进行了表征,结果显示,所得到的金纳米空球呈多晶结构,粒径约为150 nm,壳层厚度约为25 nm,表面为颗粒状金原子团簇;将金纳米空心球组装到玻碳电极表面,以SCN-作为探针分子,初步探讨了金纳米空球的SERS效应,表明其具有较强的SERS活性

Optimizing detection sensitivity on surface-enhanced Raman scattering of transition-metal electrodes with confocal Raman microscopy

Some points on how to improve the detection sensitivity of confocal Raman microscopy for the study of surface-enhanced Raman scattering (SERS) of transition-metal electrodes are discussed, including the careful design of the spectroelectrochemical cell, proper selection of the thickness of the solution layer, the binning of charge-coupled device (CCD) pixels, and appropriate setting of the notch filter. Various roughening methods for the Pt, Rh, Fe, Co, and Ni electrode surfaces have been introduced in order to obtain SERS-active surfaces. It has been shown that the appropriate roughening procedure and the optimizing performance of the confocal Raman microscope are the two most important factors to directly generate and observe SERS on net transition-metal electrodes

Density functional study and normal-mode analysis of the bindings and vibrational frequency shifts of the pyridine-M (M = Cu, Ag, Au, Cu+, Ag+, Au+, and Pt) complexes

Raman and infrared (IR) spectroscopies have been used extensively to study the adsorption of pyridine on various surfaces for more than 40 years. However, no satisfactory assignment on all the vibrational modes has been achieved. In the present study, density functional theory at the level of B3LYP/6-311+G** (for C, N, H)/LANL2DZ (for metals) has been used for the normal coordinate calculations of the neutral and cationic species of the pyridine-metal atom (ion) complexes. Based on the present calculations, new assignments of the fundamental frequencies for the bands attributed to nu(17a), nu(3), nu(5), and nu(18b) modes of the free pyridine in the reported IR and Raman spectra have been suggested. The calculated frequency shifts indicate that the coupling among nu(1), nu(12), and nu(18a) modes and the coupling between these mode,, and the N-metal (Cu, Ag, Au, or Pt) bond depend on the strength of the N-metal bond and its bonding properties. The fundamental frequency of the nu6(a) mode has a nearly linear relationship with the change of the force constant of the N-M bond, Therefore, its frequency shift can be used to directly correlate to the strength of the interaction of pyridine with the metal atom (surface)

铂纳米空球的制备及其对甲醇氧化的电催化性能

以粒径为100nm的硒球作模板,在室温下批量合成了粒径约110nm、壳厚约5 nm的铂空球.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HR-TEM)、选区电子衍射(SAED)、X射线衍射(XRD)、能量色散X射线谱(EDX)等检测技术表征了其形貌与结构;以甲醇为探针分子研究了铂纳米空球修饰玻碳电极对甲醇电氧化的催化性能.结果表明,由铂原子簇团构筑的多孔铂空球粒径均匀、分散性好、结构稳定、比表面积大、传质性能好,是甲醇氧化的理想催化材料.循环伏安(CV)结果表明:当甲醇氧化的电流密度0.10 mA·cm~(-2),正扫时,铂纳米空球的氧化电位与实心铂纳米粒子及铂黑相比,分别负移了约110和64mV;负扫时,前者比后两者分别负移了约51与13 mV.经800圈循环伏安扫描后,正扫时,甲醇在铂纳米空球上氧化峰的电流密度为实心铂纳米粒子及铂黑上的13和15倍;负扫时,前者为后两者的19和38倍.表明铂纳米空球对甲醇氧化具有较好的催化活性和稳定性