Kinetic Study of Photoelectrochemical Oxidation of Lignin Model Compounds on TiO2 Nanotubes

本文用电化学方法制备了二氧化钛纳米管，并用扫描电子显微镜和X 衍射对其形貌及组成进行了表征. 进一步研究了木质素的两个模型化合物, 1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy) -1,3-propanediol (DMP) and 3-hydroxy-1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanone (HDM),在二氧化钛纳米管上的光电氧化. 在DMP的光电氧化过程中, 一个新的紫外吸收峰出现在波长304 nm处. 虽然中间体的形成速率随着浓度的增加而增加, 却随着温度的增加而减少. 尽管HDM 和DMP在结构上有很小的差别, 在氧化过程中DMP却呈现出很小的吸光度变化, 表明HDM 不易被光电氧化. 量子化学计算结果也表明，DMP更容易被氧化, 这个结果与光电氧化的结果相吻合.In this study, TiO2 nanotubes were prepared via the electrochemical oxidation of titanium substrates in a non-aqueous electrolyte and their morphology and microstructures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoelectrochemical oxidation of two lignin model compounds, 1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanediol (DMP) and 3-hydroxy-1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanone (HDM), was investigated. A new band appeared at ~304 nm during the photoelectrochemical oxidation of DMP. The rate of DMP intermediate formation was amplified with the increase of initial concentrations, while it was diminished with increased temperature. Despite the similarity in structure between HDM and DMP, there are only small increases in absorbance during the oxidation of HDM, suggesting that HDM is less reactive. Quantum chemical calculations based on the density functional theory (DFT) were performed in order to link photoelectrochemical reactivity with specific molecular properties. Relatively higher ELUMO-EHOMO of HDM makes it more stable and thus more refractory to oxidation, which is consistent with our photoelectrochemical results.This work was supported by a Strategic Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). A. Chen acknowledges NSERC and the Canada Foundation of Innovation (CFI) for the Canada Research Chair Award in Materials and Environmental ChemistryThis work was supported by a Strategic Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). A. Chen acknowledges NSERC and the Canada Foundation of Innovation (CFI) for the Canada Research Chair Award in Materials and Environmental Chemistry作者联系地址：湖首大学化学系, 加拿大, 安大略 P7B 5E1Author's Address: Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada通讯作者E-mail：[email protected]

Electrochemical and spectroelectrochemical probing of the ionic channel in Nafion films using the redox of perfluoroalkyl viologen

We explored the electrochemistry of a perfluoroalkyl viologen, N,N′-di-(1H,1H,2H,2H-perfluorobutyl)-4,4′-bipyridinium dichloride (FC4VFC4) in a Nafion film on an Au electrode. The capability of FC4VFC4 as a redox-active probe for micro-environments of the ionic channels in the Nafion film was highlighted by clarifying the difference of its electrochemical behavior from that of its alkyl analog, dibutyl viologen (C4VC4). The time course of cyclic voltammograms (CVs) was tracked after immersion of a Nafion film-coated Au electrode in viologen solutions of various concentrations, Cs. The strongly Cs-dependent time change revealed the formation of an aggregate of FC4VFC4 in the ionic channels in the Nafion film. The aggregate blocks its own redox reaction at Cs ≥ 10 μM. At Cs = 5 μM, FC4VFC4 exhibited a quasi-reversible response. In contrast, C4VC4 showed a quasi-reversible response in the Cs range from 5 μM to 500 μM. We also used the time dependent change of electroreflectance (ER) spectra to track the state of viologens in the close proximity of the electrode|Nafion interface. After the immersion in 50 μM FC4VFC4 solution, the ER signals of the redox of FC4VFC4 molecules, being not in direct contact with the Au surface, rapidly increased in line with the change of CVs. What followed was a steep decrease of ER signal while the CV redox current was still increasing. It was also found that the FC4VFC4 aggregates in the Nafion film block the electrode reactions of [Ru(NH3)6]2+/3+, methylviologen, and C4VC4, which otherwise show reversible or quasi-reversible responses in the absence of FC4VFC4. All the results, especially the sharp contrast of the behavior of FC4VFC4 to that of C4VC4, revealed that either or both intermolecular perfluoro chain-chain interaction and perfuorinated FC4VFC4 side chain-Nafion perfluoroether side chain interaction are the key to determine the chemical micro-environment in the ionic channels

Nano-cement composite with graphene oxide produced from epigenetic graphite deposit

This study presents the development of a nano-cement composite with graphene oxide (GO) carbon-based nanomaterials synthesized from a high-purity epigenetic graphite deposit. Diamond drill sampled graphite mineralization was upgraded through beneficiation and purification to recover a high-purity graphite product (99.9% graphitic carbon “Cg”). An alternate and improved chemical oxidation process based on the Modified Hummers method was adopted for the synthesis of GO from high-purity graphite. Microstructural analysis were performed to characterise GO. The GO consists of single bondOH, single bondC=O, single bondCOOH, and C-O-C functional groups with a layer thickness of 1.2 nm, 2 to 3 layers of graphene, an interlayer distance of 0.90 nm and a Raman (ID/IG) ratio of 0.79. The effect of 0.02, 0.04, and 0.06 wt% GO of cement on the composite workability, hydration, microstructure, mechanical and transport properties was determined. Increasing the concentration of GO in the composite decreased the workability due to the hydrophilic nature of the 2D planar surface. The rate of hydration accelerated and the cumulative hydration heat increased with the increasing proportions of GO in the composite. GO dosages about 0.02 and 0.04 wt% of cement in the composites resulted the maximum enhancement of compressive and flexural strength by 83 and 26%, respectively, compared to the control mix (0 wt% GO). The microstructural investigation shows that GO enhanced the hydration of calcium hydroxide (CH) and calcium silicate hydrate (C-S-H) during the nucleation and growth stages, filled pores, bridged micro-cracks and created interlocking between the cement hydration products. Collectively, these effects ultimately improved the mechanical properties of the composites. Also, in this process, the 0.02 and 0.04 wt% GO cement composite increased the electrical resistivity by 11.5%, and decreased the sorptivity by 29%, respectively, both of which improved the overall performance of the composite

Determination of Drugs in Clinical Trials: Current Status and Outlook

All pharmaceutical drugs, vaccines, cosmetic products, and many medical breakthroughs must first be approved through clinical research and trials before advancing to standard practice or entering the marketplace. Clinical trials are sets of tests that are required to determine the safety and efficacy of pharmaceutical compounds, drugs, and treatments. There is one pre-phase and four main clinical phase requirements that every drug must pass to obtain final approval. Analytical techniques play a unique role in clinical trials for measuring the concentrations of pharmaceutical compounds in biological matrices and monitoring the conditions of patients (or volunteers) during various clinical phases. This review focuses on recent analytical methods that are employed to determine the concentrations of drugs and medications in biological matrices, including whole blood, plasma, urine, and breast milk. Four primary analytical techniques (extraction, spectroscopy, chromatography, and electrochemical) are discussed, and their advantages and limitations are assessed. Subsequent to a survey of evidence and results, it is clear that microelectromechanical system (MEMS) based electrochemical sensor and biosensor technologies exhibit several notable advantages over other analytical methods, and their future prospects are discussed