Liquid phase deposition of hemoglobin/SDS/TiO2 hybrid film preserving photoelectrochemical activity

This work demonstrates that liquid phase deposition (LPD) technique provides a novel approach to the immobilization of hemoglobin (Hb) in TiO(2) film for studying the direct electron transfer of Hb. Using the LPD process, a hybrid film composed of Hb, TiO(2) and sodium dodecylsulfonate (SDS) is successfully prepared on the electrode surface. The surface morphology of as-deposited Hb/SDS/TiO(2) film shows a flower-like structure. The cyclic voltammetric measurement indicates that the LPD hybrid film facilitates the electron transfer of Hb, which yields a pair of redox peaks prior to the characteristic voltammetric peaks of TiO(2). Due to the electrocatalytic activity of Hb towards H(2)O(2), the Hb/SDS/TiO(2) hybrid LPD film can be utilized as an H(2)O(2) sensor, showing a sensitive response linearly proportional to the concentration of H(2)O(2) in the range of 5.0×10(-7)-4.0×10(-5) mol/L. At the same time, the Hb/SDS/TiO(2) hybrid film preserves the photoelectrochemical activity of TiO(2). The photovoltaic effect on the electrochemical behavior of Hb/SDS/TiO(2) film is observed after long-time UV irradiation on the film, which could improve the calibration sensitivity for H(2)O(2).     

Preparation of a nanoporous CaCO3-coated TiO2 electrode and its application to a dye-sensitized solar cell

A nanoporous CaCO3 overlayer-coated TiO2 thick film was prepared by the topotactic thermal decomposition of Ca(OH)2, and its performance as an electrode of a dye-sensitized solar cell was investigated. As compared to bare TiO2, nanoporous CaCO3-coated TiO2 provided higher specific surface area and, subsequently, a larger amount of dye adsorption; this in turn increased short-circuit current (Jsc). Furthermore, the CaCO3 coating demonstrated increased impedance at the TiO2/dye/electrolyte interface and increased the lifetime of the photoelectrons, indicating the improved retardation of the back electron transfer, which increases Jsc, open-circuit voltage (Voc), and fill factor (ff). Thereby, the energy conversion efficiency (eta) of the solar cell improved from 7.8 to 9.7% (an improvement of 24.4%) as the nanoporous CaCO3 layer was coated onto TiO2 thick films.     

Electron transport in silver-semiconductor nanocomposite films exhibiting multicolor photochromism

In the multicolor photochromism of TiO2 nanoporous films loaded with photocatalytically deposited Ag nanoparticles, visible light-induced electron transfer from Ag to oxygen molecules plays an essential role. Here we examined the effect of TiO2 on the electron transfer. We found that not only photocatalytically deposited Ag, but also electrodeposited Ag and commercially available Ag nanoparticles in a nanoporous TiO2 film exhibit the multicolor photochromism. The electrodeposited Ag exhibits the multicolor photochromism also in a nanoporous ZnO film, but not in nanoporous indium-tin oxide (ITO) and SiO2 matrices. Photoelectrochemical measurements for the Ag-TiO2 nanocomposite elucidated that some of the photo-excited electrons on Ag are transferred to oxygen molecules via TiO2 and non-excited Ag. Thus, an n-type semiconductor plays an important role in the charge separation between the excited electrons and Ag+. Non-excited Ag on TiO2 also plays an important role in the charge separation and/or catalysis of oxygen reduction. Replacement of the non-excited Ag with Pt accelerated the electron transport from the photo-excited Ag to oxygen molecules and the photochromic behavior.     

Immobilisation of lactate dehydrogenase on poly(aniline)-poly(acrylate) and poly(aniline)-poly(vinyl sulphonate) films for use in a lactate biosensor

The immobilisation of enzymes on an electrode surface, in such a manner that they retain both substrate specificity and high levels of catalytic activity, is of great importance in bioelectrochemistry. This includes areas such as the development of enzyme-catalysed fuel cell electrodes, biosensors and other biotechnological applications. We have investigated the catalytic activity of hexahistidine tagged variants of lactate dehydrogenase (EC 1.1.1.27) from the thermophile Bacillus stearothermophilus both in solution and when immobilised on poly(aniline)-poly(acrylate) (PANi-PAA) or poly(aniline)-poly(vinyl sulphonate) (PANi-PVS) composite films. Both the C- and N-terminally tagged enzymes are readily immobilised on the modified electrode and catalyse the conversion of lactate and NAD⁺ to pyruvate and NADH. The NADH that is generated can be readily oxidised at the PANi-modified electrode surface.In solution, the activity of the C-tagged enzyme (LDH-CHis) was some 30% less that of the wild-type under comparable conditions, whereas the N-tagged enzyme was found to possess essentially the same activity as the wild-type. However, when the enzymes were immobilised on PANi-PAA and PANi-PVS the C-tagged enzyme films showed a higher NADH-dependent current than the wild-type LDH whilst the N-tagged enzyme had the highest of the three. In addition, the C-tagged enzyme film appeared more stable than the wild-type LDH-PANi film. A novel immobilisation chemistry of the enzyme is proposed to account for these observations.     

紫外光下纳米TiO2 薄膜亲水性机理的电化学研究

The nanometer films of TiO2 were prepared by sol-gel method on ITO（Indium-tin oxide,SnO2:In） substrate. The TiO2 film was the anatase phase with a particle size of 100 nm from the measurements of X-ray diffraction and AFM（Atomic-Force-Microscope）. Electrochemical characteristics of ITO/ TiO2 electrode under UV（ultraviolet）irradiation were investigated using the method of cyclic voltammetry. A new oxidative peak was observed at 0.035 V when the TiO2 electrode was irradiated by 253.7 nm UV light for a certain time. The peak current increased with the irradiation time. It was assumed that the new oxidative peak resulted from Ti3+,which was formed during the UV illumination. The changes of hydrophilicity of the TiO2 thin film on ITO under UV light were also observed. It was assumed that the changes of hydrophilicity of the films may be related with the formation of Ti3+ on the surface when the film was irradiated by UV light.     

Third generation biosensor based on myoglobin-TiO2/MWCNTs modified glassy carbon electrode

TiO2 nanoparticles were homogeneously coated on multi-walled carbon nanotubes by hydrothermal deposition, this nanocomposite may be a promising material for myoglobin immobilization in view of its high biocompatibility and large surface. The glassy carbon electrode modified with Mb-TiO2/MWCNTs films exhibited a pair of weU defined, stable and nearly reversible cycle voltammetric peaks. The electron transfer between Mb and electrode surface, Ks of 3.08 s^-1, was greatly facilitated in the TiO2/ MWCNTs film. The electrocatalytic reductions of hydrogen peroxide were studied, the apparent Michaelis-Menten constant is calculated to be 83.10 μmol/L, which shows a large catalytic activity of Mb in the TiO2/MWCNTs film to H2O2.     

Electrochemical study of photovoltaic effect of nano titanium dioxide on hemoglobin

Nano titanium dioxide (TiO2) and hemoglobin (Hb) were co-modified on pyrolytic graphite (PG) electrode to study the photovoltaic effect of TiO2 nanoparticles (NPs) on the electron transfer reactivity and catalytic activity of the protein. By means of cyclic voltammetry (CV) and FTIR measurements, the study was characterized in both aerobic and anaerobic environments. Experimental results revealed that the factors which mainly interacted with Hb were electron/hole pairs and reactive oxygen species (ROS) generated by the photovoltaic effect when TiO2 NPs were irradiated under ultraviolet (UV) light. The electron/hole pairs generated on the surface of TiO2 would influence the structure of Hb gently, so the electron transfer reactivity and catalytic ability of the protein slightly changed. In contrast, ROS interacted with Hb intensively, which brought in much conformational change to Hb and its active centers, and even cause some damage. Consequently, the electron transfer reactivity and catalytic activity of Hb changed with a process of increasing initially and decreasing afterwards.     

不同波长紫外光照下纳米TiO2薄膜的光致亲水性与循环伏安行为

通过溶胶-凝胶方法分别在ITO和玻璃表面制备了纳米TiO_2薄膜，研究了纳米 TiO_2薄膜在254及365nm的紫外光照射下的循环伏安行为和光致超亲水性。在紫外 光的照射下，TiO_2薄膜电极可表现出两个光电化学过程，纳米TiO_2薄膜的光致超 亲水性转变及两个光电化学过程的速率均取决于紫外光的波长，原因在于纳米 TiO_2薄膜对两种波长的光的吸收率和光子的能量不同。提出了光电化学过程的机 理，认为紫外光照射下纳米TiO_2薄膜的超亲水性变化与产生Ti~(3+)的过程引起的 表面微观结构变化存在的一定的内在联系。     

聚3-甲基噻吩修饰量子点硫化铅连接TiO2纳米结构膜的光电化学研究

采用原位化学法在纳米结构TiO2电极上制备了量子点PbS(Q-PbS), 并用电化学方法在TiO2/Q-PbS表面聚合3-甲基噻吩[poly(3-Methylthiophene), PMeT]. 研究结果表明, PMeT和Q-PbS单独修饰纳米结构TiO2电极和PMeT修饰Q-PbS连接纳米结构TiO2电极的光电流产生的起始波长都向长波方向移动; 在可见光区光电转换效率均比纳米结构TiO2的光电转换效率提高显著; PMeT与Q-PbS修饰的纳米结构TiO2之间存在p-n异质结. 在一定条件下p-n异质结的存在有利于光生电子/空穴的分离, 提高了光电转换效率.     

Redox-linked protein dynamics of cytochrome c probed by time-resolved surface enhanced infrared absorption spectroscopy

Time-resolved surface enhanced infrared absorption (SEIRA) spectroscopy is employed to analyse the dynamics of the protein structural changes coupled to the electron transfer process of immobilised cytochrome c (Cyt-c). Upon electrostatic binding of Cyt-c to Au electrodes coated with self-assembled monolayers (SAMs) of carboxyl-terminated thiols, cyclic voltammetric measurements demonstrate a reversible redox process with a redox potential that is similar to that of Cyt-c in solution, and a non-exponential distance-dependence of the electron transfer rate as observed previously (D. H. Murgida and P. Hildebrandt, Chem. Soc. Rev. 2008, 37, 937). On the basis of characteristic redox-state-sensitive amide I bands, the protein structural changes triggered by the electron transfer are monitored by rapid scan and step scan SEIRA spectroscopy in combination with the potential jump technique. Whereas the temporal evolution of the conjugate bands at 1693 and 1673 cm(-1) displays the same rate constants as electron transfer, the time-dependent changes of the 1660-cm(-1) band are slower by about a factor of 2. The study demonstrates that time-resolved SEIRA spectroscopy provides further information about the dynamics and mechanism of interfacial processes of redox proteins, thereby complementing the results obtained from other surface-sensitive techniques. In comparison with previous surface enhanced resonance Raman spectroscopic findings, the present results are discussed in terms of the local electric field strengths at the Au/SAM/Cyt-c interface.     

聚3-甲基噻吩修饰硫化物量子点连接纳米结构TiO2膜的光电化学研究

采用原位化学法在纳米结构TiO₂膜上制备了量子点CdS, PbS (Q-CdS, Q-PbS), 并用电化学方法在TiO₂/Q-CdS, TiO₂/Q-PbS表面聚合3-甲基噻吩[poly(3-Methylthiophene, PMeT)]. 用光电化学方法研究了PMeT修饰Q-CdS, Q-PbS连接TiO₂纳米结构膜, 实验结果表明, PMeT和Q-CdS, Q-PbS单独修饰纳米结构TiO₂电极和PMeT修饰Q-CdS, Q-PbS连接纳米结构TiO₂电极的光电流产生的起始波长都向长波方向移动; 一定条件下在可见光区光电转换效率均较纳米结构TiO₂的光电转换效率有明显的提高; 聚3-甲基噻吩(PMeT)与Q-CdS, Q-PbS连接的纳米结构TiO₂之间存在p-n异质结. 在一定条件下p-n异质结的存在有利于光生电子/空穴的分离, 在本文实验条件下PMeT修饰Q-CdS, Q-PbS连接纳米结构TiO₂电极最高的单色光的光电转换效率分别为11%和7%.     

血红蛋白与NO分子间相互作用的电化学表征

近年来 ,蛋白质的电化学研究引起了人们广泛兴趣[1～ 5] .利用自组装技术[4 ] 或将蛋白质分子固定于双层磷脂膜、水凝胶、表面活性剂膜及 Al2 O3膜上[6～ 9] 等可成为制备蛋白质膜的有效手段 .血红蛋白(Mr=6 50 0 0 )是生物体内一类重要的蛋白 ,由于对其结构已有较清楚的认识 [10 ] ,因而常被选作探讨生物大分子的电化学行为的模型分子 . NO是一种内皮细胞松弛因子、神经递质和免疫系统的媒介体 ,与生物体内的许多生理过程、疾病的产生与治疗有密切关系 [11～ 13] .因此研究蛋白与 NO之间的相互作用并寻求监测 NO的各种途径具有重要意义…     

Direct electrochemistry and electrochemical catalysis of myoglobin-TiO2 coated multiwalled carbon nanotubes modified electrode

TiO(2) nanoparticles were homogeneously coated on multiwalled carbon nanotubes (MWCNTs) by hydrothermal deposition, and this nanocomposite might be a promising material for myoglobin (Mb) immobilization in view of its high biocompatibility and large surface. The glassy carbon (GC) electrode modified with Mb-TiO(2)/MWCNTs films exhibited a pair of well-defined, stable and nearly reversible cycle voltammetric peaks. The formal potential of Mb in TiO(2)/MWCNTs film was linearly varied in the range of pH 3-10 with a slope of 48.65 mV/pH, indicating that the electron transfer was accompanied by single proton transportation. The electron transfer between Mb and electrode surface, k(s) of 3.08 s(-1), was greatly facilitated in the TiO(2)/MWCNTs film. The electrocatalytic reductions of hydrogen peroxide were also studied, and the apparent Michaelis-Menten constant is calculated to be 83.10 microM, which shows a large catalytic activity of Mb in the TiO(2)/MWCNTs film to H(2)O(2). The modified GC electrode shows good analytical performance for amperometric determination of hydrogen peroxide. The resultant Mb-TiO(2)/MWCNTs modified glassy carbon electrode exhibited fast amperometric response to hydrogen peroxide reduction, long term life and excellent stability. Finally the activity of the sensor for nitric oxide reduction was also investigated.     

后处理对TiO_2纳米晶膜电极光电性能的改善(英文)

利用TiCl4 水溶液处理TiO2 纳米晶膜电极 ,可以提高光电流 ,改善电极的光电转换性能 .对未经处理和处理后电极的比表面、孔分布 ,以及瞬态光电流分析表明 ,后处理改善了电荷在电极中的传输 ,从而提高了光电流     

Cytochrome c biosensor for determination of trace levels of cyanide and arsenic compounds

An electrochemical method based on a cytochrome c biosensor was developed, for the detection of selected arsenic and cyanide compounds. Boron doped diamond (BDD) electrode was used as a transducer, onto which cytochrome c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH = 7) was found to be in the range of (1.1–4.5) × 10⁻⁸ A μM⁻¹ and the detection limits ranged from 4.3 to 9.1 μM. The biosensor is therefore able to measure significantly lower than current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines, for these types of analytes. The protein binding was monitored as a decrease in biosensor peak currents by SWV and as an increase in biosensor charge transfer resistance by electrochemical impedance spectroscopy (EIS). EIS provided evidence that the electrocatalytic advantage of BDD electrode was not lost upon immobilisation of cytochrome c. The interfacial kinetics of the biosensor was modelled as equivalent electrical circuit based on electrochemical impedance spectroscopy data. UV–vis spectroscopy was used to confirm the binding of the protein in solution by monitoring the intensity of the soret bands and the Q bands. FTIR was used to characterise the protein in the immobilised state and to confirm that the protein was not denatured upon binding to the pre-treated bare BDD electrode. SNFTIR of cyt c immobilised at platinum electrode, was used to study the effect of oxidation state on the surface bond vibrations. The spherical morphology of the immobilised protein, which is typical of native cytochrome c, was observed using scanning electron microscopy (SEM) and confirmed the immobilisation of the cytochrome c without denaturisation.     

Direct Electron Transfer of Hemoglobin on a Carbon Ionic Liquid Electrode with TiO2 Nanopatricle as Enhancer

Room temperature ionic liquids (RTILs) N‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) was fabricated and applied to adsorb the hemoglobin (Hb) and TiO₂ nanoparticles on the electrode surface step by step to form a Hb modified electrode noted as TiO₂/Hb/CILE. UV‐Vis and FT‐IR spectra showed that Hb in the film retained its native conformations. Cyclic voltammetric experiments indicated that a pair of well‐defined quasi‐reversible redox peaks appeared with the formal potential (E^0′) located at ?0.251 V (vs. SCE) at pH 7.0 phosphate buffer solution (PBS), which was the characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters of the Hb in the film such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant (k_s) were estimated as 0.469, 0.87 and 0.635 s^?1, respectively.     

TiO2 surface modification and characterization with nanosized PbS in dye-sensitized solar cells

The nanoporous TiO2 films utilized in dye-sensitized solar cells (DSSCs) possess a large surface-to-volume ratio, which facilitates the adsorption of sensitizing dye and the recombination due to the high density of surface traps. In this paper, nanosized PbS was fabricated on the TiO2 films. The components of the modified TiO2 film were studied by X-ray diffraction (XRD) and electron probe microanalysis (EPMA), while the structure of the film was characterized with BET physisorption and high-resolution scanning electron microscopy (HRSEM). The results showed that the PbS particles were 2-3 nm and discrete on the surface of TiO2. Diffusion photovoltage (PV) spectroscopy was employed to study the charge separation and diffusion processes inside modified and unmodified TiO2 films. The diffusion PV signals revealed that the traps on the surface of TiO2 were extremely reduced due to the presence of PbS. The results of transient photovoltage and back I-V characteristics showed that the back reaction, that is, the recombination due to the reaction between an electron on TiO2 and the hole-transporting media, was retarded significantly.     

L-胱氨酸在Pb/nanoTiO_2膜电极上的电催化还原

采用阳极氧化和恒电位沉积法制备Pb纳米粒子修饰的多孔Ti基TiO2(Pb/nanoTiO2)膜电极.通过对不同的电沉积电位和时间对比,找出了最佳电沉积条件.SEM分析显示该膜为均匀多孔结构,Pb纳米粒子均匀地分散在TiO2膜的表面.循环伏安和计时电流法研究了L-胱氨酸在Pb/nanoTiO2膜电极上的电催化还原活性,结果表明该电极对L-胱氨酸的还原具有高催化活性和稳定性.     

射频磁控溅射制备纳米TiO2薄膜的光电化学行为

在室温下采用射频磁控溅射法制备了纳米晶粒的TiO2薄膜,用循环伏安法研究了ITO/TiO2薄膜电极的光电化学行为,并测量了相应TiO2薄膜的亲水性与光催化能力.结果表明,在室温下制备的TiO2薄膜为无定形结构,当退火温度超过400 ℃时转化为锐钛矿结构.在400 ℃下退火的TiO2薄膜具有良好的亲水性和光催化能力. TiO2薄膜电极用254 nm的紫外光照射一定时间后会产生新的氧化峰,且随着光照时间的增加,峰电流也增加.初步认为用紫外光照射一定时间后, TiO2薄膜的循环伏安图的氧化峰属于光生的Ti3＋,而光致亲水性可能与Ti3＋的生成有关.     

Direct electrochemistry and electrocatalysis of hemoglobin on undoped nanocrystalline diamond modified glassy carbon electrode

Direct electrochemistry of hemoglobin (Hb) was observed at glassy carbon electrode (GCE) modified with undoped nanocrystalline diamond (UND) and Hb multilayer films via layer-by-layer assembly. UV-VIS absorbance spectroscopy, electrochemical impedance spectroscopy and cyclic voltammograms were employed to characterize the film. The results showed that the UND had the effect of enhancing the electron transfer between Hb and the electrode surface. Hb in the multilayer films maintained its bioactivity and structure. It also exhibited a good catalytic activity towards the reduction of H(2)O(2). The reciprocal of catalytic current showed a linear dependence on the reciprocal of H(2)O(2) concentration ranging from 0.5 microM to 0.25 mM with a detection limit of 0.4 microM. The apparent Michaelis-Menten constant was estimated to be 0.019 mM.