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1.
通过电化学扫描法在玻碳电极和导电玻璃基底上组装制备过渡金属铜取代多金属氧酸盐[PCu(H2O)Mo11O39]5-和4代聚酰胺-胺(G4-PAMAM)交替沉积的复合膜.X射线光电子能谱(XPS),原子力显微镜(AFM),循环伏安法(CV)结果表明复合膜成功制备且有好的均匀性.多层膜中的[PCu(H2O)Mo11O39]5-与其在溶液中的氧化还原行为相比,电子转移控制速率不同,该多层膜修饰电极稳定性好,对NO-2的还原及抗坏血酸的氧化具有较好的电催化性能.  相似文献   

2.
通过静电层层自组装方法在预修饰聚二烯丙基二甲基氯化铵的电极基片上制备了Dawson型磷钼钒杂多酸/聚酰胺-胺多层复合膜.用X射线光电子能谱、紫外-可见光谱、循环伏安法和原子力显微镜分析表征了多层复合膜的形成过程;用循环伏安法表征了该复合膜修饰电极的电化学性能,研究结果表明,该复合膜修饰的电极稳定性好,对亚硝酸盐、溴酸盐的还原以及抗坏血酸的氧化具有良好的催化活性.  相似文献   

3.
在4-氨基苯甲酸修饰的玻碳电极上制备了过渡金属取代杂多酸[ZnW11O39Mn(H2O)]^8-(ZnW11Mn)多层膜,各层的循环伏安行为证明膜的增长均匀,峰电流随层数的增加而增加,与其在溶液中的氧化还原行为相比,多层膜中ZnW11Mn显示出一些特殊的性质,还讨论了pH对其氧化还原行为的影响,该多层膜驿BrO3^-和H2O2的还原及抗坏血酸的氧化具有较好的电催化性能。  相似文献   

4.
用电化学扫描法制备了{[PMo12O40]3--Pt/PAMAM}n多层复合膜,通过X射线光电子能谱(XPS)、循环伏安测定(CV)和原子力显微镜(AFM)对样品的化学组成和膜的均匀性进行了表征。测试和分析结果表明[PMo12O40]3--Pt和PAMAM通过静电相互作用形成了交替多层复合膜,且膜的增长均匀,[PMo12O40]3-和Pt粒子均匀分布在间隔剂PAMAM上。采用三电极体系的循环伏安电化学分析方法研究了样品在酸性溶液中对甲醇的电催化氧化活性,结果表明,与Pt/GCE催化剂相比,{[PMo12O40]3--Pt/PAMAM}n/GCE呈现出较高的电催化氧化活性和好的稳定性。  相似文献   

5.
氨基酸多金属氧酸盐纳米粒子复合膜的制备及抗菌活性   总被引:6,自引:1,他引:5  
用水热微乳法制备了Keggin结构(CTA)0.2(HGly)2.8[PMo12O40]·nH2O(1) 纳米粒子(nano-1), 并通过元素分析, XPS, IR, XRD, TEM和CV进行表征. 利用层接层自组装技术, 将已制备的纳米粒子装配成纳米复合膜, 用紫外-可见光谱监测膜的生长, 用电化学方法分析膜的成分. 测定了纳米粒子对致病Escherichia coli(E. coli)的拮抗性, 结果显示, 纳米粒子及其复合膜具有显著的抗菌活性.  相似文献   

6.
合成了2种不同的钒取代Keggin型多金属氧酸盐(Na4PMo11VO40和(HGly)4PMo11VO40,以下分别简写为PMo11V和Gly-PMo11V),并用紫外光谱和红外光谱对其进行结构表征.以这2种化合物为效应物,采用酶动力学方法研究其对酪氨酸酶二酚酶的抑制效果、抑制机理和抑制类型.结果表明:PMo11V和Gly-PMo11V对酪氨酸酶均有明显的抑制效果,其IC50分别为0.522和0.447mmol/L.其中,PMo11V对酪氨酸酶的抑制过程属可逆的竞争型抑制,抑制常数KI为2.629mmol/L,而Gly-PMo11V对酪氨酸酶的抑制属不可逆的抑制.综合比较,Gly-PMo11V对蘑菇酪氨酸酶的抑制效果优于PMo11V.  相似文献   

7.
采用循环伏安法和碳糊电极,考察了用共缩合法和二次嫁接法合成的多金属氧酸盐(POM)/SBA-15介孔杂化材料的电化学性质以及氧化还原性能.在乙腈介质和所检测的电势范围内,溶液中游离的PW11Si23-物种和浸渍负载于介孔氧化硅上的同样POM物种显示两对WVI单电子氧化还原峰;共价键联于介孔氧化硅上的PW11Si23-物...  相似文献   

8.
无机-有机杂多盐[Bmim]5PMo10V2O40的制备及电催化性能   总被引:1,自引:1,他引:0  
合成了Keggin型磷钼钒1-丁基-3-甲基咪唑无机-有机杂化多金属氧酸盐([Bmim]5PMo10V2O40),并用元素分析、等离子体原子发射光谱、红外光谱、热重和差热分析等手段对其进行了表征. 在0.5 mol/L H2SO4溶液中,考察了邻苯二酚和H2O2在[Bmim]5PMo10V2O40修饰的碳糊电极(B-PMo10V2O40-CPE)上的电化学行为. 与空白碳糊电极对比发现,在B-PMo10V2O40-CPE上,邻苯二酚的氧化和还原峰的峰电位差减小了108 mV,氧化还原峰的峰电流明显增大;在-65和-200 mV出现了H2O2的不可逆还原峰,且还原峰的峰电流也明显增大. 结果表明,[Bmim]5PMo10V2O40对邻苯二酚具有良好的电催化氧化还原作用,对H2O2具有良好的电催化还原作用. 同时该修饰电极表现出良好的稳定性、重现性和易表面更新性.  相似文献   

9.
采用循环伏安法,研究双-Keggin型含铕硅钼钨多金属氧酸盐(Eu(SiMo4W7)213-)水溶液的电化学性质,结果表明,在0.7~-0.45V的电位区间内,Eu(SiMo4W7)213-呈现了两对准可逆的单电子氧化还原峰,峰电位随着溶液pH值的升高而线性负移,催化活性实验显示,在酸性溶液中该化合物对NaNO2和H2O2的还原反应具有良好的催化作用.  相似文献   

10.
聚苯胺负载H4PMo11VO40催化剂的结构和催化性能   总被引:2,自引:0,他引:2  
 合成了聚苯胺负载的H4PMo11VO40催化剂,利用IR, XRD,ICP,SEM和NH3-TPD等技术对催化剂进行了表征,证实H4PMo11VO40能够负载于聚苯胺载体上,并有效地改善了H4PMo11VO40的酸碱-氧化还原催化性能. 考察了催化剂催化正己醇转化的性能,正己醇氧化生成正己醛和脱水生成正己烯两种产物. 与未负载的H4PMo11VO40相比,聚苯胺负载的4PMo11-VO40催化剂的氧化还原催化性能有所提高,而酸碱催化性能有所降低,并且催化性能随着H4PMo11VO40负载量的增加而提高. 但负载量过高时,正己醛收率反而降低. 其中以C6H4.5NH4PMo11VO40)0.0319催化剂最佳,140 ℃时达到最大正己醇转化率87.6%,正己醛的收率为48.8%,选择性为55.7%.  相似文献   

11.
The {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films are prepared by LBL electrostatic assembly technique, and their uniform and homogeneous traits have been verified by cyclic voltammetry. The {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films with PAMAM as the outmost layer, having an open structure and exhibiting good penetrability for the solvent molecules at low pH, are used as matrices for electro-deposition of Pt micro-nano clusters in situ. X-ray photoelectron spectroscopy (XPS) analysis and field emission scanning electron microscope (FE-SEM) characterization show that the unique Pt micro-nano clusters with flower-like structure have been immobilized on the surface of {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films. The morphologies of Pt micro-nano clusters are influenced by electro-deposition conditions such as deposition potential, deposition time, and the number of layers of {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films. Pt(-clusters)-{PMo(12)/PAMAM}(3) composite films demonstrate good electrocatalytic activities regarding methanol oxidation and improved tolerance of CO.  相似文献   

12.
Hybrid self-assembled multilayer films were prepared by alternate adsorption of 1,10-diaminodecane(1,10-DAD)and Keggin polyoxometalates of Siw12O40^4,SiW11VO40^-5,and PMo12O40^3-,respectively.The films were reproducibly grown at each adsorption cycle as monitored by UV spectroscopy.  相似文献   

13.
黄正国  程龙 《分析化学》2000,28(11):1331-1335
通过电化学生长法在4-氨基硫酚自组装膜修饰金电极上制备了包含杂多酸(SiMo11VO^5-40和聚合物阳极离子PDDA的多层膜修饰电极。用循环伏安法研究了该多层膜的电化学行为,结果表明,Mo的第3个还原峰随多层膜层数的增加显著增长,而另两个还原峰增长缓慢。该修饰电极的峰电位随PH的增加而线性负移,表明有氢离子参与杂多酸的氧化还原反应。该修饰电极对BrO^-3和NHO2的还原反应有良好的催化作用,催化电流随着层数的增加而增长,并且Mo的第三个还原峰电流与CRrO^-3有良好的线性关系。  相似文献   

14.
The nitration of alkanes by using nitric acid as a nitrating agent in acetic acid was efficiently promoted by vanadium-substituted Keggin-type phosphomolybdates such as [H4PVMo11O40], [H5PV2Mo10O40], and [H6PV3Mo9O40] as catalyst precursors. A variety of alkanes including alkylbenzenes were nitrated to the corresponding nitroalkanes as major products in moderate yields with formation of oxygenated products under mild reaction conditions. The carbon--carbon bond cleavage reactions hardly proceeded. ESR, NMR, and IR spectroscopic data show that the vanadium-substituted polyoxometalate, for example, [H4PVMo11O40], decomposes to form free vanadium species and [PMo12O40](3-) Keggin anion. The reaction mechanism involving a radical-chain path is proposed. The polyoxometalates initially abstract the hydrogen of the alkane to form the alkyl radical and the reduced polyoxometalates. The reduced polyoxometalates subsequently react with nitric acid to produce the oxidized form and nitrogen dioxide. This step would be promoted mainly by the phosphomolybdates, [PMo12O40](n-), and the vanadium cations efficiently enhance the activity. The nitrogen dioxide promotes the further formation of nitrogen dioxide and an alkyl radical. The alkyl radical is trapped by nitrogen dioxide to form the corresponding nitroalkane.  相似文献   

15.
Two Vanadium‐substituted Keggin‐type polyoxometalates, K3H2[α‐SiVW11O40]?6H2O (SiVW11) and K4H2[γ(1, 2)‐SiV2W10O40]?4H2O (SiV2W10) were first successfully immobilized on 4‐aminobenzoic acid modified glass carbon electrodes respectively by layer‐by‐layer assembly with poly (ethylenimine) (PEI) as counterions. The regular growth processes were monitored by cyclic voltammetry (CV), and it was proved that the multilayer films were uniform and stable. The cyclic voltammetry results indicated that the electrochemical behavior of two multilayer films was similar, and their redox couples are pH‐ and scan rate‐dependent. The multilayer films show favorable electrocatalytic active toward the reduction of NO2?, IO3? and H2O2.  相似文献   

16.
We carried out in operando Mo K-edge X-ray absorption fine structure measurements on the rechargeable molecular cluster batteries (MCBs) of polyoxometalates (POMs), in which a Keggin-type POM, [PMo(12)O(40)](3-), is utilized as a cathode active material with a lithium metal anode. The POM-MCBs exhibit a large capacity of ca. 270 (A h)/kg in a voltage range between V = 4.0 V and V = 1.5 V. X-ray absorption near-edge structure analyses demonstrate that all 12 Mo(6+) ions in [PMo(12)O(40)](3-) are reduced to Mo(4+) in the discharging process. This means the formation of a super-reduced state of the POM, namely, [PMo(12)O(40)](27-), which stores 24 electrons, and this electron number can explain the large capacity of the POM-MCBs. Furthermore, extended X-ray absorption fine structure analyses reveal the molecular structure of [PMo(12)O(40)](27-), which is slightly reduced in size compared to the original [PMo(12)O(40)](3-) and involves Mo(4+) metal-metal-bonded triangles. Density functional theory calculations suggest that these triangles are formed because of the large number of additional electrons in the super-reduced state.  相似文献   

17.
Electron transfer from the electron donor of p-phenylenediamine (PPD) to the electron acceptor of (H+)3[PMo12O40]3- forms a one-electron-reduced Keggin cluster of [PMo12O40]4-, bearing a S = 1/2 spin, while proton transfer from the proton donor of (H+)3[PMo12O40]3- to the proton acceptor of PPD yielded mono- and diprotonated cations of 4-aminoanilinium (HPPD+) and p-phenylenediammonium (H2PPD2+). By introduction of crown ether receptors during the crystallization process, supramolecular cations of (HPPD+)(crown ethers) and/or (H2PPD2+)(crown ethers) were successfully introduced into three new alpha-[PMo12O40]4- salts of (H2PPD2+)2([12]crown-4)4[PMo12O40]4- (1), (HPPD+)4([15]crown-5)4[PMo12O40]4- (2), and (HPPD+)2(H2PPD2+)([18]crown-6)4[PMo12O40]4- (3) as the countercation. The protonated states of PPD and molecular-assembly structures of the supramolecular cations depended on the size of the crown ethers. In salt 3, a novel mixed-protonated state of HPPD+ and H2PPD2+ was confirmed to be complexed in the cation structure. According to the changes in the cation structures, the anion arrangements were modulated from those of the two-dimensional layer for salt 1 to the isolated cluster for salts 2 and 3. The temperature-dependent magnetic susceptibilities of salts 1-3 were consistent with the isolated spin arrangements of [PMo12O40]4-. The electronic spectra of salts 1-3 indicated the intervalence optical transition from pentavalent Mo(V) to hexavalent Mo(VI) ions within the [PMo12O40]4- cluster. Temperature-dependent electron spin resonance spectra of salt 2 revealed the delocalization-localization transition of the S = 1/2 spin at 60 K. The spin on the [PMo12O40]4- cluster was localized on a specific Mo(V) site below 60 K, which was thermally activated with an activation energy of 0.015 eV.  相似文献   

18.
骨架金属原子对Keggin阴离子电子结构和物化性质的研究   总被引:4,自引:1,他引:3  
使用第一原理密度泛函理论中的离散变分方法(DFT-DVM)对(PM~1~2O~4~0)^n^-(M=Mo,W,V),(PMo~9W~3O~4~0)^3^-,(PMo~9V~3O~4~0)^6^-五种Keggin结构杂多阴离子进行了电子结构计算,讨论了骨架金属原子对Keggin结构杂多阴离子的电荷分布、成键作用、热稳定性、氧化还原性等的影响。结果表明,骨架金属原子对Keggin阴离子的电荷分布和成键作用均有一定的影响,以Mo,W,V作骨架金属原子的Keggin阴离子(PM~1~2O~4~0)^n^-的热稳定性顺序为:(PW~1~2O~4~0)~3^->(PMo~1~2O~4~0)^3^->(PV~1~2O~4~0)^1^5^-。提出了判断杂多阴离子氧化性强弱的两因素法---脱出晶格氧的难易程度和LUMO轨道电负性,并根据两因素法得到氧化性强弱顺序为:(PV~1~2O~4~0)^1^5^->(PMo~1~2O~4~0)^3^->(PW~1~2O~4~0)~3^-。同时,讨论了当(PMo~1~2O~4~0)~3^-中的Mo部分被W和V取代后,即(PMo~9W~3O~4~0)^3^-,(PMo~9V~3O~4~0)^6^-,其中取代原子对电子结构的影响,结果表明,W取代使整个阴离子的稳定性增强,但氧化性减弱,V取代,使稳定性减弱,但氧化性增强。  相似文献   

19.
The redox properties of four series of more than one handred acids and salts of rare earth heteropoly compounds, such as LnHSiMoi2O40, In (PMo11 O39)211-, Ln (PW11 O39)211-, Ln (AsW11 O39)211-, Ln(GeW11O39)213-, Ln(BW11O39)215-, Ln(GaW11O39)216-, Ln(P2Mo17O61)217-, Ln (As2W17O61)217-, Ln2P2Mo18O62and Ln2HP2Mo17VO62(Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, etc. ) which have Keggin, Daw-son and their derivative structures, were studied by means of potentiometric titration, polarography and cy-clovoltammetry. The mechanisms of the redox reactions were supposed-and the orders of redox ability of the heteropoly compounds were concluded. The periodic changes in reduction potentials of Ln(PMo11O39)211-and Ln(P2Mo17O61)2217- with Ln atomic numbers, and the correlation between E1/2 of Ln(XMo11O39)2(?)-(X =P, Ge, Si) and nq2(n is the main quantum number of the central atoms and q is their charges) were found.  相似文献   

20.
Protonated phosphovanadomolybdates of the Keggin structure, H(3+x)PV(x)Mo(12-x)O(40) where x = 0, 1, 2, and derivatives with surface defects formed by loss of constitutional water were studied using high-level DFT calculations toward determination of the most stable species and possible active forms in oxidation catalysis in both the gas phase and in polar solutions. The calculations demonstrate that protonation at bridging positions is energetically much more favorable than protonation of terminal oxygen atoms. The preferential protonation site is determined by the stability of the metal-oxygen bond rather than the negative charge on the oxygen atom. In H(3)PMo(12)O(40), maximum distances between protons at bridging oxygen atoms are energetically favored. In contrast, for H(4)PVMo(11)O(40) and H(5)PV(2)Mo(10)O(40) protons prefer nucleophilic sites adjacent to vanadium atoms. Up to three protons are bound to the nucleophilic sites around the same vanadium atom in the stable isomeric forms of H(5)PV(2)Mo(10)O(40) that result in strong destabilization of oxo-vanadium(V) bonding to the Keggin unit. Such behavior arises from the different nature of the Mo-O and V-O bonds that can be traced to the different sizes of the valence d orbitals of the metals. Coordination of two protons at the same site yields water and an oxygen defect as a result of its dissociation. The energetic cost for the formation of surface defects decreases in the order: O(t) ? O(c) ? O(e) and is lower for the sites adjacent to vanadium atoms. Vanadium atoms near defects also have a significant contribution to the LUMO. Thus, vanadium-substituted polyoxometalates with defects near and, especially, between vanadium atoms present a plausible active form of polyoxometalates in oxidation reactions.  相似文献   

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