Electrochemical protein chip with arrayed immunosensors with antibodies immobilized in a plasma-polymerized film

An electrochemical protein chip was microfabricated. A thin-film three-electrode system, including an array of 36 platinum working electrodes, a set of thin-film Ag/AgCl electrodes, and platinum auxiliary electrodes, was integrated on a glass substrate. Capture antibodies were immobilized in a 4.5-nm-thick double layer of a hexamethyldisiloxane plasma-polymerized film. Because of their highly cross-linked network structure, the capture antibodies could be firmly immobilized. No nonspecific adsorption was observed during a series of procedures to detect target proteins, and electrochemical cross talk between neighboring sites was negligible. The sandwich immunoassay was conducted on a single chip using model proteins, alpha-1-fetoprotein and beta2-microglobulin. A distinct current increase following the oxidation of hydrogen peroxide produced by the enzymatic reaction of glucose oxidase was observed, which indicates that the capture proteins could actually bind the target proteins. Two kinds of protein were detected independently on multiple sites with respective capture antibodies.     

Influence of raw carbon nanotubes diameter for the optimization of the load composition ratio in epoxy amperometric composite sensors

In this work, it is reported the necessity to characterize the raw carbon materials before their application in composite electrodes based on multiwall carbon nanotubes (MWCNTs) dispersed in epoxy resin for the development of improved amperometric sensors. These sensors must contain an optimum MWCNT/epoxy ratio for their best electroanalytical response. The main drawback in MWCNTs composite materials resides in the lack of homogeneity of the different commercial nanotubes largely due to different impurities content, as well as dispersion in their diameter/length ratio and state of aggregation. The optimal composite electrode composition takes into account the high electrode sensitivity, low limit of detection, fast response, and electroanalytical reproducibility. These features depend on carbon nanotube physical properties as the diameter. Three different commercial carbon nanotubes with different diameters were characterized by transmission electron microscopy and the results were significantly different from the ones provided by the manufacturers. Then, the three MWCNTs were used for the MWCNT/epoxy sensors construction. After an accurate electrochemical characterization by cyclic voltammetry and electrochemical impedance spectroscopy, they were employed as working electrodes using ascorbic acid as a reference analyte. Percolation theory was applied in order to verify the electrochemical results. It is demonstrated that the optimum interval load of raw carbon material in the optimized-composite electrodes closely depends on the MWCNTs diameter, needing 5 % in carbon content for the narrowest MWCNTs containing composite electrodes versus 12 % for the widest MWCNTs.     

A morphological investigation of electrodes for solid electrolytes

Using the techniques of image analysis, profilometry, gas permeability, mercury porosimetry, and gas adsorption, the morphological properties of porous electrode film (1 to 300 μm) materials are discussed. The materials include platinum paste which is utilized as electrodes for high-temperature oxygen-ion-conducting ZrO₂ electrolytes and for low-temperature solid-state protonic electrolytes. Also considered are plasma-sprayed nickel layers and silver membranes. It is shown that each of the five methods can be used to make quantitative evaluations of film electrodes. The electrode morphological parameters measured include particle dimeter, pore diameter, porosity, three-phase line, thickness, surface texture, gas-flow/pressure, pore area, and surface area. A discussion of these properties as they relate to activation and concentration polarization of electrochemical cells is also presented.     

Facile fabrication of activated carbonized horseweed-based biomaterials and their application in supercapacitors

Carbonized horseweed was prepared for the first time using KOH as activating agent and employed as an electrode material. Varying the KOH/C weight ratio had a dramatic effect on the electrochemical capacitance of this electrode material. The obtained results showed that the sample prepared using a KOH/C weight ratio of 5/1 exhibited the highest specific surface area of 1469 m² g^?1, with average pore diameter of 3.18 nm. Further, this sample also exhibited the highest specific capacitance (184.2 F g^?1) at a current density of 0.4 A g^?1 in 6 M KOH electrolyte. In addition, the sample retained 97.6 % of its initial specific capacitance even after 1000 cycles, owing to the formation of a microporous/mesoporous structure by the activation process, the structure which provided suitable sites for charge transport and electrolyte diffusion. Thus, activated microporous carbon materials derived from horseweed could be effective as electrode materials in supercapacitors.     

Preparation and electrochemical properties of coke powder activated carbon based electrode materials

Coke powder activated carbons (CPACs) were prepared using coke powder as raw materials. The as-prepared CPACs were characterized by energy dispersive spectrometer, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The BET surface area and porous properties of CPACs were evaluated by nitrogen adsorption at 77 K. The optimal preparation conditions for CPACs were optimized according to the results of a series of electrochemical performance measurements by using the as-prepared CPACs as electrode in 2 mol L^?1 electrolyte solution of KOH. The CPACs, which were prepared under optimal conditions, exhibit a BET surface area of 285.6 m² g^?1, a pore volume of 0.112 m³ g^?1, a statistical average pore diameter of 10 nm, and ratios of the sum of micro and meso pore volume to the total pore volume of about 80.4 %, respectively. The electrochemical measurement results show that the electrode prepared by CPACs under optimal preparation conditions exhibits a specific capacitance of 211 F g^?1. Moreover, it also exhibits a good electrochemical stability with a specific capacitance reaches up to 156 F g^?1 over consecutive 1,000 cycle numbers.     

Application of different types of carbon nanotubes as PIGE surface modifier in Pd(II) electrochemical determination

Nowadays, carbon nanotubes with differences in specific surface area, dopants, or functional groups are used in a number of applications, electrolysis not excluding. Various types of carbon nanotubes could improve bare graphite electrode properties by different way and so result in obtaining the different records for the same analyte. The automobile catalysts represent mobile sources of palladium. Levels of palladium in environment are continuously increasing and they need to be monitored. Electrochemistry is a useful and inexpensive component of the field of environment monitoring. For Pd(II) electrochemical determination, six types of carbon nanotubes were used as paraffin impregnated graphite electrode (PIGE) surface modifiers. Voltammetric determination brought interesting results of LOD, LOQ, standard and relative precisions of the method. These parameters as well as prediction intervals were calculated according to the technical procedure DIN 32 645 for the six electrodes and three pH values. Modification of PIGE with nitrogen doped carbon nanotubes (LOD = 1.91 × 10^?5 mol L^?1 or 3.14 × 10^?5 mol L^?1 for pH 3 and pH 4.5, respectively) seems very promising. In laboratory, functionalized carbon nanotubes, with specific surface area 200 m² g^?1, provided LOD = 1.49 × 10^?5 mol L^?1 (pH = 3) and 1.42 × 10^?5 mol L^?1 (pH = 4.5)     

Fluorescence imaging of the heterogeneous reduction of oxygen

The reduction of oxygen at a variety of solid electrodes was spatially imaged using fluorescence microscopy. Hydroxide produced during electrolysis of oxygen converted the acid-base indicator, fluorescein, into its fluorescent form. Fluorescence intensity was collected as a function of potential at platinum, silver, and glassy carbon disk electrodes and tracked the faradaic current due to oxygen reduction at platinum electrodes. The ability to observe spatial variations in electron-transfer kinetics was demonstrated at a bimetallic electrode prepared from silver and platinum. Fluorescence imaging of oxygen reduction on silver electrodeposited on glassy carbon revealed the location and size of the silver deposits. Imaging of oxygen reduction at a ruthenium-graphite composite electrode demonstrated the ability to identify electrochemically active sites on a spatially complex surface.     

透明硫化钴对电极在染料敏化太阳能电池中的应用

硫化钴纳米材料是一种重点研究的染料敏化太阳能电池对电极材料。本工作以氟掺杂二氧化锡导电玻璃为基片, 采用反向恒压电沉积法制备透明硫化钴薄膜。实验结果表明: 电镀溶液的pH是硫化钴薄膜表面形貌形成的关键性因素, 而电沉积圈数可以有效控制硫化钴薄膜的厚度。电化学测试结果表明: 硫化钴薄膜对电极展现出了良好的电催化活性, 尤其是在电镀溶液pH为7.2、电沉积圈数为12圈的最佳条件下制备的硫化钴对电极具有大量的纳米薄片状结构, 有利于增加电催化活性位点, 使得其展现出了比铂电极更加优异的电催化性能。由此电极组装的染料敏化太阳能电池的能量转换效率达到7.26%, 10个电池器件的平均效率为7.18%, 高于相应铂电极器件的电池效率(6.94%)。     

Supported and unsupported platinum catalysts prepared by a one-step dry deposition method and their oxygen reduction reactivity in acidic media

The present study examines the physical and electrochemical properties of platinum particles generated by a combustion method for use in oxygen reduction on the cathode side of a proton exchange fuel cell (PEMFC). This method employs a one-step, open-atmosphere, and dry deposition technique called reactive spray deposition technology (RSDT). The objective of this study is to characterize the intrinsic activity of the platinum produced for incorporation into low-loading cathode electrodes in high performing membrane electrode assemblies (MEA). The process allows for independent real-time control of the carbon, platinum, and ionomer ratios in the final electrode. In this research work we examine the oxygen reduction reaction via a rotating disk three electrode set-up to understand the intrinsic activity of the as-sprayed platinum as well as platinum condensed onto a carbon support. The mass and specific activities were measured in a 0.1 M perchloric acid electrolyte under different deposition conditions and loading was verified by atomic emission spectroscopy inductively coupled plasma (AES-ICP). Microscopy results indicate that the platinum particle sizes are 5 nm (σ = 2.8 nm) in diameter while TEM and XRD show that the platinum generated by the process is pure and crystalline without bulk oxides or precursor material present. The initial rotating disk electrode result shows that the RSDT technique is capable of producing catalysts with an oxygen reduction mass activity at 0.9 V of 200 mA/mg_Pt rotating at 1600 rpm and 30 °C. The electrochemically active surface area approaches 120 m²/g for the platinum, carbon, and ionomer samples and the unsupported sample with only platinum has an active area of 92 m²/g. The rather larger surface area of the unsupported sample exists when the platinum is deposited as a highly porous nanostructured layer that allows for high penetration of reactant.     

The performance of sintered TiO2-x electrodes and the electrochemical polymerization of O-phenylene diamine at surface imperfections

TiO_2-x electrodes were fabricated under atmospheric conditions using the ceramic method at 1400°C. Photoelectrochemical and capacitance measurements permitted verification of the relation of the performance of such electrodes to the presence of surface imperfections. The electropolymerization of o-phenylene diamine ( OPD ) on TiO_2-x ceramic electrodes in the dark was investigated and compared with the electropolymerization of OPD on smooth platinum electrodes. The results indicate that polymerization occurs only on the surface imperfections of the TiO_2-x semiconductor and effectively blocks the electrode surface and prevents electron exchange with the solution. The photoelectrical response of electrodes subjected to this treatment shows the decrease of the dark current intensity in the potential region of oxygen adsorption in comparison with untreated electrodes. The flat band potential determined from Mott-Schottky plots did not correlate well with the potential for the onset of anodic photocurrent and photopotential. Evidence for the electrochemical incorporation of hydrogen in the oxide and oxide surface reduction are discussed.     

Templated synthesis, characterization, and sensing application of macroscopic platinum nanowire network electrodes

Novel platinum nanowire network electrodes have been fabricated through electrodeposition using mesoporous silica thin films as templates. These electrodes were characterized by X-ray diffraction, transmission electron microscope, and scanning electron microscope. The electrochemical properties of the electrodes, such as electrochemical active area and methanol oxidation, have also been studied. Compared with conventional polycrystalline Pt electrodes, these novel nanowire network electrodes possess high electrochemical active areas and demonstrate higher current densities and a lower onset potential for methanol electro-oxidation. Enzymatic Pt nanowire-network-based sensors show higher sensitivity for glucose detection than that using conventional polycrystalline Pt electrode. Such macroscopic nanowire network electrodes provide ideal platforms for sensing and other device applications.     

Three-dimensional heterostructured MnO2/graphene/carbon nanotube composite on Ni foam for binder-free supercapacitor electrode

In this article, three-dimensional (3D) heterostructured of MnO₂/graphene/carbon nanotube (CNT) composites were synthesized by electrochemical deposition (ELD)-electrophoretic deposition (EPD) and subsequently chemical vapour deposition (CVD) methods. MnO₂/graphene/CNT composites were directly used as binder-free electrodes to investigate the electrochemical performance. To design a novel electrode material with high specific area and excellent electrochemical property, the Ni foam was chosen as the substrate, which could provide a 3D skeleton extremely enhancing the specific surface area and limiting the huge volume change of the active materials. The experimental results indicated that the specific capacitance of MnO₂/graphene/CNT composite was up to 377.1 F g^?1 at the scan speed of 200 mV s^?1 with a measured energy density of 75.4 Wh kg^?1. The 3D hybrid structures also exhibited superior long cycling life with close to 90% specific capacitance retained after 500 cycles.     

Effect of chitosan-gluconic acid conjugate/poly(vinyl alcohol) cryogels as wound dressing on partial-thickness wounds in diabetic rats

We previously developed chitosan cryogels from chitosan-gluconic acid conjugate without using toxic additives for wound care. In this study, we improved physiological characteristics of the previous cryogels by incorporating poly(vinyl alcohol) that also form cryogels. Mechanical strength of the cryogels was more than two times higher than that of the previous cryogels. Furthermore, the incorporation of poly(vinyl alcohol) enhanced water retention and resistance to degradation of the gels by lysozyme. The cryogels retained the favorable biological properties of the previous cryogels that they accelerate infiltration of inflammatory cells into wound sites. Time period for repairing 50 % of initial area of partial-thickness skin wound treated with the cryogels (4.0 ± 1.1 days) was shorter than those with gauze (6.5 ± 0.3 days) or a commercial hydrogel dressing (5.7 ± 0.3 days). Finally, we confirmed that incorporation of basic fibroblast growth factor into the cryogels was effective to further accelerate wound healing (2.7 ± 1.0 days). These results demonstrate that the cryogels in this study are promising for wound care.     

Room temperature corrosion properties of AZ31 magnesium alloy processed by extrusion and equal channel angular pressing

The electrochemical properties of AZ31 magnesium alloy processed by extrusion and equal channel angular pressing (ECAP) were investigated. The electrochemical properties were evaluated using potentiodynamic tests and electrochemical impedance spectroscopy in corrosion solution of 0.1 M sodium chloride. The electrochemical changes of the sample surface were correlated with microstructure evolution. Material processed by extrusion and subsequently by 8 passes of ECAP shows similar or even inferior corrosion resistance to the extruded material after immersion time up to 96 h. However, corrosion resistance of material after extrusion and ECAP is significantly better than that of the extruded material for immersion time of 168 h. This sudden improvement is caused by different formation and fall off of protective corrosion products. Microstructure after extrusion is inhomogeneous and contains relatively large grains, whereas material after ECAP possesses homogeneous ultrafine-grained (UFG) microstructure. As a result, material after ECAP offers more corrosion nucleation sites, but UFG microstructure causes that only smaller clusters of corrosion products fall off the surface. The easier and faster corrosion protective layer restoration on the surface of UFG material after ECAP leads to enhanced corrosion resistance.     

Effective size-controlled synthesis and electrochemical characterization of ordered Pt nanopattern arrays from self-assembling block copolymer template

This work offers an effective size-controlled synthesis of platinum nanoparticle (Pt NP) arrays for electrocatalyst through self-assembled nanopatterns of block copolymers on titanium (Ti) wafers. Size, spacing and uniformity of Pt NP with loading of Pt to a minimum were investigated to be controlled and adjusted in order to improve the electrochemically active surface area (ECSA) and ECSA stability, and Pt concentration in copolymer/chloroplatinic acid (H₂PtCl₆) solution was verified to be one of the most important factors to control the arrays’ structure. In our case, the Pt NPs with predictable size of 5–16.5 nm could be obtained when the Pt concentration is larger than 0.05 mg ml^?1, which the dominant diameter is proved to be proportional to one-third power of the Pt concentration according to the linear relation of templates’ Pt/N mass ratio versus Pt concentration, and the Pt NPs remain highly ordered arrays with predictable spacing when the Pt concentration is larger than 0.125 mg ml^?1. Decrease in Pt concentration from 2 to 0.125 mg ml^?1 is an effective method to improve the ECSA and durability simultaneously. The Pt NP arrays exhibit not only a remarkable initial ECSA value of 106.2 m² g^?1, but also a pseudo-zero particle aggregation possibility during 3000-cycle voltammetry, which is attributed to the high Pt NP dispersion and the ordered arrays that improve the Pt utilization and lower the possibility of aggregation.     

Electrochemical deposition and evaluation of electrically conductive polymer coating on biodegradable magnesium implants for neural applications

In an attempt to develop biodegradable, mechanically strong, biocompatible, and conductive nerve guidance conduits, pure magnesium (Mg) was used as the biodegradable substrate material to provide strength while the conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) was used as a conductive coating material to control Mg degradation and improve cytocompatibility of Mg substrates. This study explored a series of electrochemical deposition conditions to produce a uniform, consistent PEDOT coating on large three-dimensional Mg samples. A concentration of 1 M 3,4-ethylenedioxythiophene in ionic liquid was sufficient for coating Mg samples with a size of 5 × 5 × 0.25 mm. Both cyclic voltammetry (CV) and chronoamperometry coating methods produced adequate coverage and uniform PEDOT coating. Low-cost stainless steel and copper electrodes can be used to deposit PEDOT coatings as effectively as platinum and silver/silver chloride electrodes. Five cycles of CV with the potential ranging from ?0.5 to 2.0 V for 200 s per cycle were used to produce consistent coatings for further evaluation. Scanning electron micrographs showed the micro-porous structure of PEDOT coatings. Energy dispersive X-ray spectroscopy showed the peaks of sulfur, carbon, and oxygen, indicating sufficient PEDOT coating. Adhesion strength of the coating was measured using the tape test following the ASTM-D 3359 standard. The adhesion strength of PEDOT coating was within the classifications of 3B to 4B. Tafel tests of the PEDOT coated Mg showed a corrosion current (I_CORR) of 6.14 × 10^?5 A as compared with I_CORR of 9.08 × 10^?4 A for non-coated Mg. The calculated corrosion rate for the PEDOT coated Mg was 2.64 mm/year, much slower than 38.98 mm/year for the non-coated Mg.     

Preparation and electrochemical performances of LiFePO4/C composite nanobelts via facile electrospinning

LiFePO₄/C composite nanobelts were synthesized by calcination of the [LiOH + Fe(NO₃)₃ + H₃PO₄]/polyvinyl pyrrolidone (PVP) electrospun nanobelts. PVP was used as the electrospinning template and carbon source. During the calcination, [LiOH + Fe(NO₃)₃ + H₃PO₄] were transformed to lithium iron phosphate (LiFePO₄) and PVP was decomposed into carbon. The morphology and properties of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area analysis, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The results indicate that the mean width of LiFePO₄/C composite nanobelts is 2.50 ± 0.33 μm, the average thickness is about 162 nm and the BET specific surface area is 19.4 m² g^?1. The addition of carbon does not affect the structure of LiFePO₄, but improves its electrochemical performances. At the current density of 0.2 C, the initial discharge capacity of LiFePO₄/C electrode is 123.38 mAh g^?1 and there is no obvious capacity fading after 50 cycles. The formation mechanism of LiFePO₄/C composite nanobelts was also proposed.     

Chip cleaning and regeneration for electrochemical sensor arrays

Sensing systems based on electrochemical detection have generated great interest because electronic readout may replace conventional optical readout in microarray. Moreover, they offer the possibility to avoid labelling for target molecules. A typical electrochemical array consists of many sensing sites. An ideal micro-fabricated sensor-chip should have the same measured values for all the equivalent sensing sites (or spots). To achieve high reliability in electrochemical measurements, high quality in functionalization of the electrodes surface is essential. Molecular probes are often immobilized by using alkanethiols onto gold electrodes. Applying effective cleaning methods on the chip is a fundamental requirement for the formation of densely-packed and stable self-assembly monolayers. However, the available well-known techniques for chip cleaning may not be so reliable. Furthermore, it could be necessary to recycle the chip for reuse. Also in this case, an effective recycling technique is required to re-obtain well cleaned sensing surfaces on the chip. This paper presents experimental results on the efficacy and efficiency of the available techniques for initial cleaning and further recycling of micro-fabricated chips. Piranha, plasma, reductive and oxidative cleaning methods were applied and the obtained results were critically compared. Some interesting results were attained by using commonly considered cleaning methodologies. This study outlines oxidative electrochemical cleaning and recycling as the more efficient cleaning procedure for electrochemical based sensor arrays.     

The effects of early osseointegration in different implant sites in rabbit tibias

The aim of this study was to evaluate the early osseointegration of implants with the same surface treatment in different implant sites in rabbit tibias after 4 weeks. A total of 42 acid-etched implants were implanted in three different sites in the tibia: group A was 2.08 ± 0.18 mm below epiphyseal line; group B was 7.00 ± 0.61 mm below the epiphyseal line; group C was 13.01 ± 1.26 mm below the epiphyseal line. After 4 weeks, the average bone-to-implant contact (BIC) values were as follows: group A, 40.02 ± 4.82 %; group B, 28.20 ± 5.41 %; group C, 20.76 ± 3.10 %. The BIC measurements yielded statistically significant differences among group A, group B and group C (P < 0.01); group A demonstrated the best osseointegration. In the present study, the different implantation sites in the selected 20-mm area demonstrated different early osseointegration; the sites located 7 ± 1.5 mm below the epiphyseal line were best suited for observing the effectiveness of early osseointegration among the three sites. The statistical results of the early osseointegration of implants are therefore affected by the location of the implant sites in this 20-mm area.     

Optical second harmonic generation at platinum phthalocyanine-modified platinum electrodes

Optical second harmonic generation (SHG) has been used to observe changes within electronically conducting platinum phthalocyanine (PtPc) films deposited on polycrystalline platinum electrodes as the film undergoes electrochemical modification. PtPc-modified electrodes produced enhanced SHG responses over bare platinum surfaces. This is proposed to be due to an electric quadrupole contribution from the PtPc molecule. Examination of the polarization dependence of the SHG response reveals that electroactive PtPc molecules exist in environments both parallel and perpendicular to the electrode surface. It has been possible to observe redox processes occurring within the films by monitoring the magnitude of the SHG response with variations in potential. The decrease in SHG signal has been shown empirically to be proportional to the charge removed from the film during oxidation of the phthalocyanine (Pc) ring.