Peculiarities of atomic hydrogen interactions with detonation nanodiamonds

Hydrogen treatment is a popular way of surface modification of nanodiamonds. Here, we used atomic hydrogen treatment of the functionalized surface to increase its hydrophobicity gently and maintain its overall composition. Corresponding mechanism was revealed via combination of theoretical and experimental methods.     

Click chemistry electrode modification using 4-ethynylbenzyl substituted cobalt phthalocyanine for applications in electrocatalysis

In this work, we report on the synthesis and applications of a new cobalt tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyanine (3) for the detection of hydrazine. The glassy carbon electrode (GCE) was first grafted through diazotization, providing the GCE surface layer with azide groups. Thereafter, the 1,3-dipolar cycloaddition reaction, catalyzed by a copper(I) catalyst was used to “click” complex 3 to the grafted surface of GCE. The new platform was then characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). This work shows that 3 is an effective sensor with sensitivity of 91.5 μA mM^?1 and limit of detection of 3.28 μM which is a great improvement compared to other reported sensors for this analyte.     

A cobalt(II) phthalocyanine with indole substituents: formation,characterization and electrocatalytic studies

Herein, we report the formation of a new cobalt(II) phthalocyanine (CoPc) containing peripheral tetra-substituted indole (CoPc-ind, 2) moieties. The derivatized phthalonitrile, 4-(indole-4-oxy)phthalonitrile (1) as well its corresponding metal complex was characterized by NMR (for 1), IR– and UV–Vis spectroscopy as well as TOF mass spectrometry and elemental analysis (for 2). The electrochemical properties of the N₄-macrocyclic metal complex were investigated using cyclic- and square-wave voltammetry as well as corroborated by UV–Vis spectroelectrochemistry. The CoPc was electrodeposited onto the surface of a Pt working electrode followed by the immobilization of multiwalled carbon nanotubes (MWCNTs) onto the modified working electrode surface. The electrocatalytic activity of the resultant modified electrode toward dopamine revealed a lower ΔE value of 80?mV versus Ag|AgCl for the modified (2-MWCNTs) Pt electrode compared to the bare Pt electrode (ΔE?=?280?mV vs. Ag|AgCl). The diffusion- and convection-controlled electron-transfer kinetics of the chemically modified electrode were evaluated by chronoamperometry and rotating disk electrode techniques. Electrochemical impedance spectroscopic studies revealed that the 2-MWCNTs Pt electrode had a lower charge-transfer resistance and a higher apparent electron-transfer rate constant.     

Theoretical study of the electron transfer reaction of hydrazine with cobalt(II) phthalocyanine and substituted cobalt(II) phthalocyanines

A theoretical model is proposed to explain the trend in reactivity of cobalt(II) phthalocyanine (CoPc) and substituted cobalt(II) phthalocyanines for the oxidation of hydrazine. Our study suggests that the reaction occurs via a through bond charge transfer pathway and not via a through space charge transfer pathway as was shown in previous work for the oxidation of 2-mercaptoethanol by CoPc (G.I. Cárdenas-Jirón and D.A. Venegas-Yazigi, J. Phys. Chem. A. 106, 11398 (2002)). We propose a mechanism for the oxidation of hydrazine based on a four-step energy profile which agrees with a mechanism proposed for the electro-oxidation of hydrazine mediated by cobalt phthalocyanines confined on a graphite electrode. We show that the step in the energy profile that involves formation of a radical of hydrazine seems to be a good starting point for the study of the transfer of the first electron in the oxidation of hydrazine mediated by different substituted cobalt(II) phthalocyanines.     

Effects of covalent versus non-covalent interactions on the electrocatalytic behavior of tetracarboxyphenoxyphthalocyanine in the presence of multi-walled carbon nanotubes

Tetracarboxyphenoxy phthalocyanine was covalently linked to multi-walled carbon nanotubes and the conjugate was used for modification of glassy carbon electrodes for the detection of hydrogen peroxide. The electrocatalytic behavior was examined by cyclic voltammetry, square wave voltammetry, and rotating disk electrode. The results show that covalent linking is attractive in terms of high detecting currents, low overpotential, and high catalytic rate constants. Very low detection limits were observed with CoTCPhPc-DAMN-MWCNT(linked)-GCE at 0.33 nM. The resulting catalytic rate constant was 1.1 × 10³ M^?1s^?1.     

Interaction of nitric oxide with cobalt(II) phthalocyanine: kinetics, equilibria and electrocatalytic studies

The coordination of nitric oxide (NO) to cobalt(II) phthalocyanine (CoPc) in dimethyl sulphoxide (DMSO) has been studied. CoPc coordinates with NO in a 1:1 ratio, forming a CoPc(NO) species. The IR band observed at 1680 cm⁻¹ is assigned to the coordinated NO. In the presence of excess NO, pseudo first order kinetics were followed. The observed rate constant, k_f, was determined to be 15.0±0.3 dm⁻³ mol⁻¹ s⁻¹ and the equilibrium constant was K=5.4±0.4×10⁴dm³ mol⁻¹. Solution or adsorbed CoPc catalyses the reduction of NO. The products of reduction include NH₃ and NH₂OH.     

酞菁钴修饰碳糊电极对微量苯酚的测定

研究了苯酚在酞菁钴修饰碳糊电极上的电化学行为,提出了催化反应的机理,并以此为依据,用伏安法以酞菁钴修饰碳糊电极为工作电极测定了微量苯酚.在pH 8.7的磷酸盐缓冲溶液(PBS)中,苯酚在0.61 V(对SCE)出现一氧化峰,该峰电流与苯酚的浓度在5.0×10-7～1.0×10-4 mol/L之间呈线性关系,检出限为1.0×10-7 mol/L.此法可用于工业废水中苯酚的测定.     

碳纳米纤维增强钴酞菁催化氧化染料的性能研究

将氨基钴酞菁（CoTAPc）以共价键的形式负载到碳纳米纤维（CNF）上制备碳纳米纤维负载钴酞菁催化剂（CoTAPc-CNF）,利用原子吸收光谱、紫外-可见光吸收光谱、衰减全反射-红外光谱等方法对CoTAPc-CNF进行表征.选用具有氧杂蒽结构的罗丹明6G（Rh6G）为主要研究对象,研究CoTAPc-CNF对Rh6G的催化氧化性能,考察了温度、pH、NaCl、异丙醇等对CoTAPc-CNF催化性能的影响.结果表明,CoTAPc-CNF在常温中性条件下能有效催化氧化Rh6G;随着温度和pH的增加,CoTAPc-CNF催化氧化Rh6G速率逐渐提高;NaCl和异丙醇的加入,没有抑制催化氧化反应的进行,相反大大提高了Rh6G的降解速率,这与一般羟基自由基占主导的高级氧化体系完全不同;进一步采用电子顺磁共振波谱法证实CoTAPc-CNF/H2O2体系确实为非羟基自由基催化机理.另外,研究发现CoTAPc-CNF还能有效催化氧化其他共轭结构的染料,如偶氮染料酸性橙7（AO7）、三芳甲烷染料碱性绿1（BG1）.因此,本文探索的CoTAPc-CNF/H2O2非羟基自由基催化反应体系在处理成分复杂的实际印染废水中具有较好的应用前景.     

Synthesis of cobalt A2B triaryl corroles bearing methoxy or hydroxyl groups and their activity in electrocatalytic hydrogen evolution

Four A₂B cobalt corrole complexes 1 – 4 appending two methoxy or hydroxyl groups on the 10-meso phenyl group had been synthesized. Four cobalt corroles showed high electrocatalytic activity for hydrogen evolution reaction (HER) in the organic phase and in the aqueous phase. The hydrogen evolution pathway was EECEC when using acetic acid as proton source. When trifluoroacetic acid was used as proton source, the hydrogen evolution route via EECEC or EECC depending on the concentration of trifluoroacetic acid. Cobalt corrole 4 showed the best HER performance with the k_obs of 122.68 s⁻¹ in organic phase and the TOF of 832.2 h⁻¹ in aqueous phase respectively. The results suggested the phenyl hydroxyl group at the cobalt corrole peripheral may act as the proton relay group in HER and the o-hydroxyl of phenyl was better than m- hydroxyl for proton relay.     

Syntheses and investigation of the effects of position and nature of substituent on the spectral,electrochemical and spectroelectrochemical properties of new cobalt phthalocyanine complexes

The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to Co^IIIPc⁻²/Co^IIPc⁻² (E_½ = +0.64 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.24 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to Co^IIIPc⁻¹/Co^IIIPc⁻² species (E_p = +0.86 V versus Ag|AgCl), and ring-based reduction associated with Co^IPc⁻²/Co^IPc⁻³ species (E_½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.41 V versus Ag|AgCl) and Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.59 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.26 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.     

2,9,16,23-四-(2,6-二甲基苯氧基)酞菁钴(Ⅱ)的合成、表征及性质

用4-(2,6-二甲基苯氧基)邻苯二腈和金属盐在熔融状态下合成了2,9,16,23-四-(2,6-二甲基苯氧基)酞菁钴配合物,对产物进行了IR、UV-vis光谱、元素分析、热重分析等测定和表征.     

Flow injection analysis of zinc pyrithione in hair care products on a cobalt phthalocyanine modified screen-printed carbon electrode

Zinc pyrithione (ZPT) is an antibacterial and antifungal reagent that is often utilized for the antidandruff activity in hair-care shampoos with a composition level up to 1% in the formulation. It has some adverse effects to human and animal if consumed orally. A disposable type of cobalt phthalocyanide modified screen-printed carbon electrode (CoPc/SPE) in couple with flow injection analysis (FIA) was developed for easy and selective analysis of ZPT in commercial hair-care products. Under the optimized FIA conditions, the CoPc/SPE yielded a linear calibration plot in the window of 6–576 μM with sensitivity and detection limit of 1.65 nA μM⁻¹ and 0.9 μM (i.e. 1.42 pg in 5 μl sample loop), respectively, in 0.1 M KOH solution at an applied potential of 0.3 V versus Ag/AgCl. Since the approach is simple, easy, selective, and inexpensive, it offers a potential application of daily ZPT analysis in hair-care products.     

L-酪氨酸为指示剂四羧基钴酞菁催化瑞利散射法测定青蒿素

常温常压下,在pH 10.0的Britton-Robinson缓冲溶液中,以及8.0×10-7 mol/L四羧基钴酞菁催化作用下,L-酪氨酸与青蒿素反应,瑞利散射光谱发生变化.其288 nm处瑞利散射光降低,降低值△I(I0-I)与青蒿素浓度在0～4.6×10-5 mol/L范围内呈线性关系,相关系数r为0.9985;检出限为4.89×10-7 mol/L.方法已用于中药青蒿草中青蒿素的检测.     

贮氢合金表面分析和金属氢化物电极电催化活性

贮氢合金表面状态和组成是影响金属氢化物(MH)电极电催化活性的重要因素, MH电极的表面改性处理是改善电极性能的有效方法。用XPS, ICP, BET方法分析了处理后贮氢合金表面组成和状态的变化。讨论了化学还原处理对MH电极电催化活性的影响, 结果表明: 化学还原处理大大提高了MH电极反应的交换电流密度和减低了电极反应活化能。     

PdCu alloy nanoclusters: generation and activity tuning for electrocatalytic oxidation of nitrite

The process control of electrodeposition of nanoparticles by cyclic voltammetry (CV) is important with respect to the preparation of highly active catalysts. We have simultaneously deposited novel nanoclusters of PdCu alloys on the surface of glassy carbon electrodes (GCEs) from a solution. SEM, XPS, XRD and electrochemical techniques were used for characterizing the nanocomposite and the modified electrode (PdCu/GCE). We found that the PdCu alloys form liana-like fractal 2D-nanoclusters on the base and spherical 3D-nanoclusters on the top, and these clusters consisted of 9.9 nm average sized nanoparticles. The 2D-clusters have strong ability to reduce the overpotentials of nitrite oxidation but have small influence on the current response. Inversely, the 3D-clusters have weak ability to influence the overpotentials but strong ability to influence the current response. It is found that the cycle number is important to the catalytic activity of the generated nanoclusters and 25 cycle number was the optimal for obtaining most negative peak potential (0.77 V vs. SCE) with highest CV peak current (0.53 A/M · cm²) and DPV peak current for nitrite oxidation. This PdCu/GCE can be used as a sensitive and stable nitrite sensor with wide linear range. Mechanisms of the deposition and catalytic activity of the nanoclusters are discussed.     

Quantum chemical studies on the structure and detonation properties of the fused polynitrodiazoles: New high energy density molecules

In this study, we explore the possibility that fused polynitrodiazoles act as high energy density materials. Density functional theory calculations at the B3LYP/aug‐cc‐pVDZ level were performed to predict the structure, energy of explosion (≈1.68 kcal g^?1), density (≈1.98 g cm^?3), detonation velocity (≈9.50 km s^?1), and detonation pressure (≈41.50 GPa) of model molecules. The predicted properties have been found to be promising compared with 3,4,5‐trinitro‐1H‐pyrazole, 1,3,5‐trinitro‐1,3,5‐triazinane, and octahydro‐1,3,5,7‐tetranitro‐l,3,5,7‐tetraazocane. The nature of azoles of the molecule presumably determines the geometry, stability, sensitivity, density, and detonation performance. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Kinetic Study of the Electro-Catalytic Oxidation of Hydrazine on Cobalt Hydroxide Modified Glassy Carbon Electrode

Electrocatalytic oxidation of hydrazine was investigated on a cobalt hydroxide modified glassy carbon (CHM-GC) electrode in alkaline solution. The process of oxidation involved and its kinetics were established by using cyclic voltammetry, chronoamperometry techniques as well as steady state polarization measurements. In cyclic voltammetry (CV) studies, in the presence of hydrazine the peak current increase of the oxidation of cobalt hydroxide is followed by a decrease in the corresponding cathodic current. This indicates that hydrazine is oxidized on the redox mediator that is immobilized on the electrode surface via an electrocatalytic mechanism. A mechanism based on the electrochemical generation of Co(IV) active sites and their subsequent consumption by the hydrazine in question was also investigated.     

Effect of trimethylsilyl substitution on the structure and properties of phthalocyanine: A density functional theory study

The geometries of four isomers of the trimethylsilyl substituted phthalocyanine (Pc)— I , II , III , and IV —have been optimized at the B3LYP/3‐21G level of density functional theory. Normal‐mode vibrational analyses have been performed and their standard thermodynamic functions, molar fractions, and electronic absorption spectra calculated. Single‐point energies have been calculated at the B3LYP/6‐311G* level for all isomers to evaluate the heats of formation from an isodesmic reaction. It is found that substitution has little influence on the geometry and electronic structures of the Pc framework. The corresponding geometric parameters in various isomers are close. According to the B3LYP/6‐311G*//B3LYP/3‐21G results, substitution at the peripheral position of the isoindole with an inner hydrogen is most favorable. The energies increase in the order of IV < II < III < I , and the energy difference between IV and I is 5.75 kJ/mol. The molar fractions of IV , II , III , and I are 0.80, 0.17, 0.02, and 0.02 and the heats of formation are 2009.96, 2010.10, 2015.85, and 2016.52 kJ/mol, respectively. This indicates that nonperipheral substituted Pcs have higher energy and little production because they are not stable under the considered conditions. The electronic spectra of the substituted Pcs calculated using the ZINDO method have two strong Q absorption bands around 700 nm and one B band around 300 nm that are slightly shifted compared with those in Pc. The ratios of the oscillator strength of the B band to the Q bands are much lowered by trimethylsilyl substitution. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002