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51.
本文对羟乙芦丁在玻碳电极上的阳极微分脉冲安行为进行了研究,发现在Na2HPO4溶液中(pH=8.95)于+0.64V(vs.Ag/AgCl)左右产生一个良好的阳极氧化伏安峰,浓度在5~60mg/L之间与峰电流呈线性关系,不需分离直接测定了片剂中的羟乙芦丁含量。电极反应为扩散速率控制的不可逆可程。 相似文献
52.
J. Mayer T. Szreder M. Szadkowska-Nicze A. Faucitano 《Journal of polymer science. Part A, Polymer chemistry》1998,36(8):1217-1226
A pulse radiolysis study of isotactic polypropylene (PP) film has been carried out with the main aims of investigating charge trapping in an undoped system and solute radical ion generation in an pyrene (Py) doped matrix. In PP, pulse radiolysis gives electron–positive hole pairs. The electron can be stabilized in the undoped system as a trapped electron, e. The transient absorption spectrum of e in the near-IR (up to 1800 nm) was observed in the temperature range 30–100 K. This IR absorption was not detected in the case of oxidized PP. In such a matrix electrons can be scavenged by oxidation products generating respective radical-anions (absorption in the UV RANGE, λ < 350 nm). In a doped matrix transient absorption bands centered at 450 and 500 nm were observed which can be assigned to the Py radical cation and anion, respectively. The recombination of these ionic species leads to monomer excited-state formation observed during and after the 17 ns pulse. Contrary to the Py-doped polyethylene no excimer emission was detected at room temperature even if Py content in PP was close to 0.02 mol dm−3. The rate of Py radical-ion decay was found to be temperature dependent. Two linear parts of the Arrhenius plot were observed which intersected at ca. 240 K, the glass transition temperature, Tg, for PP. The activation energies calculated for two parts of Arrhenius plot were equal to 111 and ca. 0.78 kJ mol−1 for T > Tg and T < Tg, respectively. Some preliminary results concerning the ionic processes in PP containing two solutes (Py, 3,3′-dimethyldiphenyl) were presented. The mechanism of ionic recombination in PP will be proposed and discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1217–1226, 1998 相似文献
53.
BasedonthefirstideaspresentedbyBeck',anewmethodcalledalternatingpulsecurrent-chronopotentiometricstrippinganalysis(APC-CPSA)hasbeendeveloped.Inthistechnique,duringthestrippingstepthecurrentimposedontheelectrol,ysi$cellcomprisesofanalternatingpulsecurrent(APC)andtheinherentdirectcurrentofCPSA.TheAPCisoperatedwithahighfrequencyinasquarewavemode.isandiRisdefinedastheanodicandcathodicpulsecurrent,respectively,isandtRisthetimeforwhichthesecurrentsflow.So,whenisandiRalternates,partsofthestri… 相似文献
54.
Brian N. DiMarco Dmitry E. Polyansky David C. Grills Ping Wang Yutaka Kuwahara Xuan Zhao Etsuko Fujita 《Chemphyschem》2021,22(14):1478-1487
In this work, the differences in catalytic performance for a series of Co hydrogen evolution catalysts with different pentadentate polypyridyl ligands (L), have been rationalized by examining elementary steps of the catalytic cycle using a combination of electrochemical and transient pulse radiolysis (PR) studies in aqueous solution. Solvolysis of the [CoII−Cl]+ species results in the formation of [CoII(κ4-L)(OH2)]2+. Further reduction produces [CoI(κ4-L)(OH2)]+, which undergoes a rate-limiting structural rearrangement to [CoI(κ5-L)]+ before being protonated to form [CoIII−H]2+. The rate of [CoIII−H]2+ formation is similar for all complexes in the series. Using E1/2 values of various Co species and pKa values of [CoIII−H]2+ estimated from PR experiments, we found that while the protonation of [CoIII−H]2+ is unfavorable, [CoII−H]+ reacts with protons to produce H2. The catalytic activity for H2 evolution tracks the hydricity of the [CoII−H]+ intermediate. 相似文献
55.
石墨烯修饰玻碳电极测定邻苯二酚 总被引:2,自引:0,他引:2
制备了用于测定邻苯二酚(CAT)的石墨烯修饰电极,并应用循环伏安法研究了CAT在该修饰电极上的电化学行为;用差分脉冲伏安法研究了测试底液的pH值对该修饰电极性能的影响,结果表明,此修饰电极在含不同浓度CAT的PBS溶液(pH=7.0)中测定,响应电流与CAT浓度在5.0×10-8~5.6×10-4mol/L范围内有良好的线性关系,相关系数r=0.9919,检出限为6.68×10-9mol/L(S/N=3)。与其它几种修饰电极相比,石墨烯修饰电极制备简单、响应时间快、操作简便,稳定性和重现性良好,有应用价值。 相似文献
56.
《Analytical letters》2012,45(11):851-861
Abstract A system is described for the non-flame atomisation of mercury, using sample heating pulses of a few microseconds duration. The rapid sample atomisation thus obtained leads to good analytical sensitivity; it also provides a technique for distinguishing between, and separately measuring, inorganic and organically-bound mercury. 相似文献
57.
采用脉冲充电方法替代传统充电方法,研究了在有机电解液 0.5 mol·L-1 LiBr/PC (碳酸丙烯酯)中,在铜电极上沉积锂的表面变化. 扫描电镜观测结果显示,在传统直流充电时电极表面明显地出现了枝晶,而使用脉冲充电时能够抑制枝晶的生长. 交流阻抗测试结果显示,在占空比为 0.5 时,沉积锂表面固体电解质界面(solid electrolyte interphase,SEI)膜电阻最大,沉积锂表面枝晶较少;单次脉冲电沉积时间过长,会使沉积锂表面 SEI 膜电阻减小,沉积锂表面枝晶增加;电流密度大于等于 2 mA·cm-2时,脉冲电沉积可有效抑制枝晶生长. 相似文献
58.
Cheng Wang Yuxin Leng Chuang Li Baozhen Zhao Zhizhan Xu 《Optics & Laser Technology》2010,42(4):657-661
A decentered grating stretcher for chirped pulse amplification systems is analyzed with oblique meridional ray tracing. Several formulae and conclusions are developed to design and optimize the stretcher. On basis of an analytical phase expression with an explicit significance, the expressions of the second-, third- and approximate fourth-order phases at the central wavelength are presented with only independent variables. These simplify the parameter design for this kind of stretcher and the phase compensation design of the whole amplifier system, which has been demonstrated with a practical example. 相似文献
59.
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