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Soil aggregate breakdown is the first key factor that causes soil erosion. At present, research on the mechanisms of soil aggregate breakdown during rainfall is common. However, the research to on quantifying the relative contributions of internal and external forces to aggregate breakdown remains limited. This paper was conducted to analyse the relative contribution of internal and external forces to aggregate disintegration and the factors affecting aggregate stability during rainfall. Soil aggregates with a series of textures were selected as test soil samples; deionized water was employed as the soaking solution and rainfall material in static disintegration experiments and rainfall simulation tests. The effect of internal force (soil hydrophilicity) on aggregate disintegration was analysed by the static disintegration method, and the combined effects of internal force (soil hydrophilicity) and external force (raindrop impact) on soil aggregate breakdown were analysed by rainfall simulation experiments. The results indicated that external force caused more severe soil aggregate breakdown than internal force, and the crushed aggregate was mainly distributed in the range of 2–0.25 mm. With increasing rainfall kinetic energy, the degree of aggregate breakdown increased gradually, and the degree of aggregation of the soil particles decreased gradually. Furthermore, soil aggregates with a high clay content (> 30%) were more stable than medium-clay (20–30%) and low-clay (

In this study, steels with different volume fraction of bainite and ferrite were obtained by tuning the rolling process to change the austenitic state before ferrite transformation. The volume fraction of bainite in the steel when the austenite was undeformed was ~83%, and in the steel when the austenite was deformed was ~36%. The yield strength at room temperature of the experimental steel with undeformed austenite was ~63.5 MPa higher than the experimental steel with deformed austenite, while the yield strength at 600 °C of the former was ~104.8 MPa higher than the latter. The main strengthening methods that led to difference in yield strength at elevated temperature are precipitation strengthening, dislocation strengthening and grain boundary strengthening. The experimental steel with higher volume fraction of bainite was characterized by higher Young's modulus and dislocation density at 600 °C, while the volume fraction of precipitates was relatively lower. The higher Young's modulus was mainly because of higher volume fraction of alloyed cementite precipitated from steel with higher volume fraction of bainite at 600 °C. Furthermore, the boundary densities of packet boundaries, block boundaries and sub-block boundaries had an important influence on the yield strength of steel at 600 °C.

Soil pore size distribution and pore functional characteristics are the most important for soil physical properties, water retention, and transmission. Furthermore, considerable amounts of rock fragments are present in hilly region soils. In this study, we discuss the pore size distribution and pore functional characteristics of soils as affected by rock fragments in the hilly regions of Sichuan Basin, China. The soil water characteristic curve was measured to calculate the soil total porosity and the ratio of equivalent pores in each diameter class. The results suggest that the soil total porosity decreases with increasing rock fragments size. The proportion of transmission pores increased gradually with increasing rock fragment content, whereas the fractions of storage pores and residual-bonding pores decrease gradually. Furthermore, the ratio of effective soil porosity to total porosity is higher than that of ineffective porosity to total porosity with increasing rock fragment content. In summary, increasing the rock fragment content can notably increase the proportion of soil transmission pores, thereby increasing soil aeration and water permeability. However, a high rock fragment content is not conducive to maintaining the water needed for normal plant growth.

In this study, we address the challenge of obtaining high strength at ambient and elevated temperatures in fire-resistant Ti&ndash, Mo&ndash, V steel with ferrite microstructures through thermo-mechanical controlled processing (TMCP). Thermally stable interphase precipitation of (Ti, Mo, V)C was an important criterion for retaining strength at elevated temperatures. Electron microscopy indicated that interphase precipitation occurred during continuous cooling after controlled rolling, where the volume fraction of interphase precipitation was controlled by the laminar cooling temperature. The interphase precipitation of MC carbides with an NaCl-type crystal structure indicated a Baker&ndash, Nutting (B&ndash, N) orientation relationship with ferrite. When the steel was isothermally held at 600 &deg, C for up to 3 h, interphase precipitation occurred during TMCP with high thermal stability. At the same time, some random precipitation took place during isothermal holding. The interphase precipitation increased the elastic modulus of the experimental steels at an elevated temperature. It is proposed that fire-resistant steel with thermally stable interphase precipitation is preferred, which enhances precipitation strengthening and dislocation strengthening at elevated temperatures.

High-intensity utilization of sloping farmland causes serious soil erosion and agricultural, non-point source pollution (AGNSP) in the Three Gorges Reservoir Area (TGRA). Crop-mulberry systems are important agroforestry systems for controlling soil, water, and nutrient losses. However, there are many different mulberry hedgerow planting patterns in the TGRA. In this study, soil structure, nutrient buildup, and runoff nutrient loss were observed in field runoff plots with five configurations: P1 (two longitudinal mulberry hedgerows), P2 (two mulberry contour hedgerows), P3 (three mulberry contour hedgerows), P4 (mulberry hedgerow border), and P5 (mulberry hedgerow border and one mulberry contour hedgerow), as well as a control (CT, no mulberry hedgerows). P1 had the smallest percentage of aggregate destruction (18.8%) and largest mean weight diameter (4.48 mm). P5 led to the greatest accumulation of ammonium nitrogen (NH4+&ndash, N) and total phosphorus (TP) (13.4 kg ha-1 and 1444.5 kg ha-1 on average, respectively), while P4 led to the greatest accumulation of available phosphorus (AP), nitrate nitrogen (NO3-&ndash, N), and total nitrogen (TN) (114.0, 14.9, and 1694.1 kg ha-1, respectively). P5 was best at preventing soil erosion, with the smallest average annual runoff and sediment loss of 112.2 m3 ha-1 and 0.06 t ha-1, respectively, which were over 72.4% and 87.4% lower than those in CT, respectively. P5 and P4 intercepted the most N in runoff, with average NH4+&ndash, N, NO3-&ndash, N, particulate N, and TN losses of approximately 0.09, 0.07, 0.41, and 0.58 kg ha-1, respectively, which were 49.7%, 76.2%, 71.3%, and 69.9% lower than those in CT, respectively. P5 intercepted the most P in runoff, with average TP and total dissolved phosphorus (TDP) losses of 0.09 and 0.04 kg ha-1, respectively, which were 77.5% and 70.4% lower than those in CT, respectively. Therefore, the pattern with one mulberry hedgerow border and one mulberry contour hedgerow (P5) best controlled AGNSP, followed by that with only a mulberry hedgerow border (P4).

Infiltrating water accumulates in the plough pan because of the low permeability of this layer, which results in saturation or partial saturation (soil water contents between the field water capacity and saturated water content) of the cultivated layer during continuous rainfall. Even in sloping farmlands, soil infiltration via large pores created by roots, wormholes and straw rot continuously increases, and the infiltrating water forms subsurface flow above the plough pan, causing the soil in the cultivated layer to become partially saturated. The processes and characteristics of soil particle sorting and transport in partially saturated soil were investigated in the laboratory using scouring experiments. The results showed that the stability of the aggregates was destroyed when the soil was in a soaking state and tended to be saturated, which produced a unimodal distribution of eroded sediment finer than 0.021 mm, and the main transport mechanism along the partially saturated soil was suspension/saltation. The eroded sediment in the erosion process was mainly composed of silt-sized particles, accounting for approximately 44–60% of the sediment load. Destruction of aggregates during erosion can easily enrich the soil in fine particles, especially clay-sized particles. Most fine and coarse sand-sized particles were predominantly aggregates of other finer particles; the aggregation of fine sand-sized particles was relatively poor, and a certain number of fine sand-sized particles were transported as single particles. The results reported in this study have important implications for an in-depth understanding of sediment transport in partially saturated soil.

As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. New paddy field construction can give full play to the production and ecological functions of paddy field and can adjust the development structure of the agricultural industry effectively. The soil properties of shear strength and permeability, which provide a theoretical basis for engineering design, construction, and post-operation, are important indexes in the site selection of new paddy field. The shear strength and permeability properties of soils from different land use types (vegetable field, gentle slope dryland, corn field, grapery, and abandoned dryland) for engineering new paddy field construction were investigated in this study. The results showed that the soil water content had a significant effect on the soil shear strength, internal friction angle, and cohesion. The total pressure required for soil destruction decreased with increasing water content under the same vertical pressure, resulting in easier destruction of soils. The internal friction angle decreased with increasing soil water content, and the soil cohesion first increased and then decreased with increasing soil water content. Considering that paddy fields were flooded for a long time, the soil strength properties had certain water sensitivity. Effective measures must be taken to reduce the change in soil water content, so as to ensure the stability of the embankment foundation, roadside ditch foundation, and cutting slope. In addition, the influence of changing soil water content on the strength properties of paddy soils should be fully considered in engineering design and construction, and the soil bulk density at the plough pan should reach at least 1.5 g cm−3 or more to ensure better water retention and the anti-seepage function of paddy field. The study can provide construction technology for engineering new paddy field construction in a hilly mountainous region of southwestern China.

Periodic control systems (PCSs) are widely used in real-time embedded system domain. However, traditional manual requirement analysis assumes the expert knowledge, which is laborious and error-prone. This paper proposes a novel requirement analysis approach, which supports the automated validation of the informal requirement specifications. Based on the normalized initial requirement documents, our approach can construct an intermediate SPARDL model with both formal syntax and semantics. To check the overall system behaviors, our approach can transform the SPARDL models into executable code for simulation. The derived prototype simulator from SPARDL models enables the testing-based system behavior validation. Moreover, our approach enables the analysis of the dataflow relations in SPARDL models. By revealing input/output and affecting relations, our dataflow analysis techniques can help software engineers to figure out the potential data dependencies between SPARDL modules. This is very useful for the module reuse when a new version of the system is developed. A study of our approach using an industry design demonstrates the practicality and effectiveness of our approach.

A novel composite was fabricated through dispersing multiwalled carbon nanotubes (MWNTs) in gold nanoparticle (GPs) colloid stabilized by chitosan and ionic liquid (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate, BMIMBF4). Transmission electron microscopy (TEM) experiment showed that the GPs highly dispersed on the MWNTs probably due to the electrostatic interaction among GPs, MWNTs and the imidazolium cation of BMIMBF4. X-ray photoelectron spectroscopy (XPS) indicated that thus-formed gold nanostructure was mediated by BMIMBF4. When glucose oxidase (GOD) was immobilized on the composite (MWNTs-GPs) its ultraviolet-visible absorption spectrum kept almost unchanged. The immobilized GOD coated glassy carbon electrode (GOD/MWNTs-GPs/GC) exhibited a pair of well-defined peaks in 0.10 M pH 7.0 phosphate buffer solution (PBS), with a formal potential of −0.463 V (vs. SCE). The electrochemical process involved two-electron transfer. The electron transfer coefficient was ca.0.56 and the electron transfer rate constant was 9.36 s−1. Furthermore, the immobilized GOD presented good catalytic activity to the oxidation of glucose in air-saturated PBS. The Km and Im values were estimated to be 13.7 μM and 0.619 μA. The GOD/MWNTs-GPs/GC electrode displayed good stability and reproducibility.

A novel composite film, comprising of hydrophobic ionic liquid (IL), multi-walled carbon nanotubes (MWNTs) and gold nanoparticles (GNP), was fabricated and characterized. The GNP was introduced through electrochemical deposition on IL–MWNT gel film coated glassy carbon electrodes (GCE). Experiments showed that both IL and MWNTs could facilitate the GNP deposition. With GNP the composite film exhibited smaller electron transfer resistance and higher sensitivity in sensing guanine (G) and adenine (A). Under the optimized experimental conditions, the anodic peak currents were linear to the analyte concentration in the ranges of 0.008–2.0 μM. The detection limits were down to nanomole level after an accumulation of 150 s on open-circuit. In addition, on the composite film coated GCE, the anodic peaks of G and A were well separated, and their response sensitivities kept almost unchanged no matter whether they coexisted or not. This proposed procedure was successfully applied to the detection of G and A in milk, plasma and urine samples.

A novel composite film comprising cationic gemini surfactant butyl-α,ω-bis(dimethylcetylammonium bromide) (C16H33N(CH3)2–C4H8–N(CH3)2C16H33, C16–C4–C16) and ionic liquid 1-octyl-3-methylimidazolium hexafluorophate (OMIMPF6) has been prepared. The composite film shows good biocompatibility and it can promote the direct electron transfer between hemoglobin (Hb) and glassy carbon (GC) electrode. On the C16–C4–C16 (dissolved in ethanol)-OMIMPF6 film coated GC electrode, the immobilized Hb can exhibit a pair of well-defined, quasi-reversible and stable redox peaks with a formal potential of −0.317 V (vs SCE) in 0.10 M pH 7 phosphate buffer solutions. The electron transfer coefficient (α) of Hb is calculated to be 0.44 and the heterogeneous electron transfer rate constant is 6.08 s−1. With the length of alkyl chains of gemini surfactant increasing and the ethanol concentration rising, the redox peaks of the resulting electrode C16–C4–C16–OMIMPF6–Hb/GC become bigger. The electrode presents good electrocatalytic response to peroxide hydrogen. The kinetic parameters Imax and km for the catalytic reaction are estimated. In addition, UV–vis spectra and reflectance absorption infrared spectra demonstrate that the Hb immobilized in the C16–C4–C16–OMIMPF6 film almost retains the structure of native Hb.

A novel composite material comprised of gemini surfactant (i.e. dodecyl-α,ω-bis (dimethylcetylammonium bromide), C 16 –C 12 –C 16 ) and hydrophobic room temperature ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophate, OMIMPF 6 ) has been fabricated. This composite material suits for the immobilization of horseradish peroxides (HRP). The ultraviolet–visible spectra and reflectance absorption infrared spectra of the HRP immobilized in the C 16 –C 12 –C 16 –OMIMPF 6 material are almost the same as those of native HRP. When it is coated on a glassy carbon (GC) electrode, the resulting electrode C 16 –C 12 –C 16 –OMIMPF 6 –HRP/GC exhibits a pair of well-defined, stable and reversible voltammetric peaks in 0.10 M pH 7 phosphate buffer solutions. When the hydrophobic action of ionic liquid and gemini surfactant used increases, more immobilized HRP can undergo electrochemical reaction and the voltammetric peaks become larger. In addition, the C 16 –C 12 –C 16 –OMIMPF 6 –HRP/GC electrode shows good catalytic response to dissolved oxygen and H 2 O 2 . The cathodic peak current of the electrode is linear to H 2 O 2 concentration in the range of 5.82 μM to 388 μM. The apparent Michaelis–Menten constant is estimated to be 0.159 mM. The electrode has good stability and reproducibility. Hence, the composite material has potential applications in fabricating biosensors and bioelectronics.

Single-walled carbon nanotube (SWNT) and room temperature ionic liquid (i.e., 1-butyl-3-methylimidazolium hexaflourophosphate, BMIMPF6) were used to fabricate paste modified glassy electrode (GCE). It was found that the electrode showed sensitive voltammetric response to xanthine (Xt). The detection limit was 2.0×10−9 M and the linear range was 5.0×10−9 to 5.0×10−6 M. The electrode also displayed good selectivity and repeatability. In the presence of uric acid (UA) and hypoxanthine (Hx) the response of Xt kept almost unchanged. Thus this electrode could find application in the determination of Xt in some real samples. The analytical performance of the BMIMPF6-SWNT/GCE was demonstrated for the determination of Xt in human serum and urine samples.

The direct electrochemistry and electrocatalysis of horseradish peroxidase (HRP) immobilized on a gelatin – N , N -dimethylformamide (DMF) – hydrophobic ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophsohate) gel film coated glassy carbon electrode has been studied for the first time. The immobilized HRP exhibits a pair of well-defined quasi-reversible peaks in pH 7.0 phosphate buffer solutions, which results from the direct electron transfer between the enzyme and the underlying electrode. In this case there is about 2.7% of the immobilized HRP undergoing the electrochemical reaction, which corresponds to multi-layer of HRP on the electrode surface. The HRP immobilized has higher thermal stability than in gelatin hydrogel. Experiment results also show that the voltammetric behavior of the enzyme electrode depends on the type of room temperature ionic liquid (RTIL) used. When a more hydrophobic RTIL is adopted, the resulting enzyme electrode gives better performance. In the presence of hydrogen peroxide, the enzyme electrode shows sensitive response. The sensitivity of the catalytic peak is up to 1.38 A cm −2 M −1 and the Michaelis constant is down to 6.84 × 10 −5 M, which are superior to that reported elsewhere. In addition, the UV–visible spectra of HRP entrapped in different films and the mass transfer of hydrogen peroxide are discussed as well.

An ionic liquid (i.e., 1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6)-single-walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF6-SWNT/GCE) is fabricated. At it the voltammetric behavior and determination of p-nitroaniline (PNA) is explored. PNA can exhibit a sensitive cathodic peak at −0.70 V (vs. SCE) in pH 7.0 phosphate buffer solution on the electrode, resulting from the irreversible reduction of PNA. Under the optimized conditions, the peak current is linear to PNA concentration over the range of 1.0×10−8–7.0×10−6 M, and the detection limit is 8.0×10−9 M. The electrode can be regenerated by successive potential scan in a blank solution for about 5 times and exhibits good reproducibility. Meanwhile, the feasibility to determine other nitroaromatic compounds (NACs) with the modified electrode is also tested. It is found that the NACs studied (i.e., p-nitroaniline, p-nitrophenol, o-nitrophenol, m-nitrophenol, p-nitrobenzoic acid, and nitrobenzene) can all cause sensitive cathodic peaks under the conditions, but their peak potentials and peak currents are different to some extent. Their peak currents and concentrations show linear relationships in concentration ranges with about 3 orders of magnitude. The detection limits are 8.0×10−9 M for p-nitroaniline, 2.0×10−9 M for p-nitrophenol, 5.0×10−9 M for o-nitrophenol, 5.0×10−9 M for m-nitrophenol, 2.0×10−8 M for p-nitrobenzoic acid and 8.0×10−9 M for nitrobenzene respectively. The BMIMPF6-SWNT/GCE is applied to the determination of NACs in lake water.

Glucose oxidase (GOD) immobilized in nanogold particles (NAs)- N , N -dimethylformamide (DMF) composite film on glassy carbon (GC) electrode exhibits a pair of quasi-reversible and unstable peaks due to the redox of flavin adenine dinucleotide (FAD) of GOD. When ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF 4 ) or trihexyltetradecylphosphorium bis (trifluoromethylsulfony) (P 666,14 NTf 2 ) is introduced in the film, the peaks become small. But ILs 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) and 1-octyl-3-methylimidazolium hexafluorophate (OMIMPF 6 ) make the peaks large and stable. In different composite films the formal potential ( E 0 ′) of GOD is different. UV–vis spectra show that the GOD dispersed in these films almost retains its native structure and there are weak interactions between ILs and GOD. Electrochemical impedance spectra display that NAs can promote the electron transfer between FAD and GC electrode; and ILs can affect the electron transfer through interacting with GOD. The thermal stability of GOD entrapped in NAs-DMF-ILs composite films is also influenced by ILs, and it follows such order as: in NAs-DMF-OMIMPF 6 > in NAs-DMF-BMIMPF 6 ≈ in NAs-DMF-BMIMBF 4 > in NAs-DMF. In addition, GOD immobilized in NAs-DMF-OMIMPF 6 and NAs-DMF-BMIMPF 6 films shows good catalytic activity to the oxidation of glucose. The I max of H 2 O 2 and the apparent K m (Michaelis–Menten constant) for the enzymatic reaction are calculated.

The direct electrochemistry of glucose oxidase (GOD) entrapped in nano gold particles (NAs)-N,N-dimethylformamide (DMF)-1-butyl-3-methylimidazolium hexafluophosphate (BMIMPF(6)) composite film on a glassy carbon electrode (NAs-DMF-GOD (BMIMPF(6))/GC) has been investigated for first time. The immobilized GOD exhibits a pair of well-defined reversible peaks in 0.050 M pH 5 phosphate solutions (PS), resulting from the redox of flavin adenine dinucleotide (FAD) in GOD. The peak currents are three times as large as those of GOD-NAs-DMF film coated GC electrode (i.e. NAs-DMF-GOD (water)/GC). In addition, the NAs-DMF-GOD (BMIMPF(6)) composite material has higher thermal stability than NAs-DMF-GOD (water). Results show that ionic liquid BMIMPF(6), DMF and NAs are requisite for GOD to exhibit a pair of stable and reversible peaks. Without any of them, the peaks of GOD become small and unstable. Upon the addition of glucose, the peak currents of GOD decrease and a new cathodic peak occurs at -0.8 V (versus SCE), which corresponds to the reduction of hydrogen peroxide (H(2)O(2)) generated by the catalytic oxidation of glucose. The peak current of the new cathodic peak and the glucose concentration show a linear relationship in the ranges of 1.0 x 10(-7) to 1.0 x 10(-6)M and 2.0 x 10(-6) to 2.0 x 10(-5) M. The kinetic parameter I(max) of H(2)O(2) is estimated to be 1.19 x 10(-6)A and the apparent K(m) (Michaelis-Menten constant) for the enzymatic reaction is 3.49 microM. This method has been successfully applied to the determination of glucose in human plasma and beer samples, and the average recoveries are 97.2% and 99%, respectively.

This study reports the preparation and characterization of gold nanoparticles deposited on amine-functioned hexagonal mesoporous silica (NH2–HSM) films and the electrocatalytic oxidation of glucose. Gold nanoparticles are fabricated by electrochemically reducing chloroauric acid on the surface of NH2–HSM film, using potential step technology. The gold nanoparticles deposited have an average diameter of 80 nm and show high electroactivity. Prussian blue film can form easily on them while cycling the potential between −0.2 and 0.6 V (vs saturated calomel electrode) in single ferricyanide solution. The gold nanoparticles loading NH2–HSM-film-coated glassy carbon electrode (Au–NH2–HSM/GCE) shows strong catalysis to the oxidation of glucose, and according to the cathodic oxidation peak at about 0.16 V, the catalytic current is about 2.5 μA mM−1. Under optimized conditions, the peak current of the cathodic oxidation peak is linear to the concentration of glucose in the range of 0.2 to 70 mM. The detection limit is estimated to be 0.1 mM. In addition, some electrochemical parameters about glucose oxidation are estimated.

A graphite powder – ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6) paste coated gold electrode (graphite – BMIMPF6/Au) is presented. The area and the thickness of the paste film are controlled through a sticking film with a hole. The electrode shows good stability and high electric conductivity, and K4Fe(CN)6 exhibits reversible voltammetric peaks at it. A voltammetric study of promethazine revealed that promethazine exhibits a sensitive anodic peak in pH 6.7 buffer solutions. Under the optimized conditions, the peak current is linearly related to the promethazine concentration in the range of 5.0 × 10−8–5.0 × 10−5 M. A 5 µM promethazine solution is measured successively for ten times with the same electrode, the relative standard deviation (RSD) of peak current is 1.7%. The promethazine content in a Chinese medicine (i.e. Complex Reserpine) is determined. The result is in accordance with the declared value, and the recoveries are 96.1–104%.

The adsorptive and stripping behavior of methylene blue (i.e. methylene blue chloride, MB) at a gold electrode has been studied with voltammetry, alternating current impedance spectra (ACIS) and quartz crystal microbalance (QCM). MB exhibits a pair of cyclic voltammetry peaks at about −0.3 V (versus SCE) in 0.05 M pH 6.9 phosphate buffer solutions. In the presence of cationic gemini surfactants such as C 16 H 33 N(CH 3 ) 2 –C 4 H 8 –N(CH 3 ) 2 C 16 H 33 Br 2 (C 16 –C 4 –C 16 ), C 16 H 33 N(CH 3 ) 2 –C 4 H 7 OH–N(CH 3 ) 2 C 16 H 33 Br 2 (C 16 –C 4 OH–C 16 ), C 16 H 33 N(CH 3 ) 2 –CH 2 –C 6 H 4 –CH 2 –N(CH 3 ) 2 C 16 H 33 Br 2 (C 16 –ph–C 16 ) and C 16 H 33 N(CH 3 ) 2 –C 12 H 24 –N(CH 3 ) 2 C 16 H 33 Br 2 (C 16 –C 12 –C 16 ), the anodic peak grows rapidly and moves in positive direction, but the cathodic peak gradually decreases, due to the association adsorption and electrostatic interaction of the geminis with MB and its reduced product (i.e. leuko methylene blue, LMB). With the aid of geminis the adsorption amount of MB increases under open-circuit, but the impedance of the mixed adsorption film to Fe(CN) 6 3−/4− almost keeps unchanged, compared with either bare gold electrodes or MB film, while the adsorption film of geminis exhibits greater impedance. This probably is due to the electron medium action of MB in the film. Gemini surfactants with same alkyl-chain (i.e. –(CH 2 ) 15 CH 3 ) but different molecular structure, exhibit different influence. The enhancing action of geminis studied follows such order as: C 16 –ph–C 16 > C 16 –C 4 –C 16 > C 16 –C 4 OH–C 16 > C 16 –C 12 –C 16 . The change of peak potential was ascribed to the interaction between MB and surfactants, as well as the blocking action of surfactant film. For comparison, the influence of dihexadecyldimethylammonium bromide (DCAB) and cetyltrimethylammonium bromide (CTAB) was studied, and the influence of other factors is discussed as well.

A novel carbon nanotubes modified electrode was fabricated, which was based on multi-walled carbon nanotubes (MWCNTs) dispersed in gold nanoparticles (AuNPs) colloid. It was observed that MWCNTs were dispersed in AuNPs colloid homogenously. Dihexadecyl hydrogen phosphate (DHP) was added into the suspension to prepare a more stable film modified electrode. The film showed net structure and had good electron-transfer function. On the composite film coated electrode, the electrochemical behavior of mefenamic acid was studied and an irreversible anodic peak was obtained, which was much larger than that on a bare glassy carbon electrode (GCE), due to the co-effect of MWCNTs and AuNPs on the electrochemical oxidation of mefenamic acid. Under the optimized conditions the anodic peak current was linear to the concentration of mefenamic acid in the range of 1.0 × 10-7 to 2.0 × 10-5 mol L-1. The detection limit was estimated to be 1.0 × 10-8 mol L-1 after 120 s preconcentration. The method was applied successfully to the determination of mefenamic acid in medicine sample. Um novo eletrodo modificado com nanotubos de carbono foi fabricado, com base em nanotubos de carbono multi-paredes (MWCNTs) dispersos em colóide de nanopartículas de ouro (AuNPs). Foi observado que MWCNTs foram dispersos no colóide AuNPs homogeneamente. Fosfato ácido de dihexadecil (DHP) foi adicionado à suspensão para preparar um filme mais estável. O filme mostrou estrutura em rede e teve boa função de transferência de elétron. O comportamento eletroquímico do ácido mefenâmico, no eletrodo coberto com filme composto, mostrou um pico anódico irreversível, o qual foi muito maior do que para o eletrodo de carbono vítreo (GCE), devido ao co-efeito de MWCNTs e AuNPs na oxidação eletroquímica do ácido mefenâmico. Sob ótimas condições, a corrente do pico anódico foi linear à concentração do ácido mefenâmico, no intervalo de 1,0 × 10-7 a 2,0 × 10-5 mol L-1. O limite de detecção foi estimado em 1,0 × 10-8 mol L-1 após 120 s de pré-concentração. O método foi aplicado com sucesso à determinação do ácido mefenâmico em amostra medicinal.

A novel composite film modified glassy carbon electrode has been fabricated and characterized by scanning electron microscope (SEM) and voltammetry. The composite film comprises of single-wall carbon nanotube (SWNT), gold nanoparticle (GNP) and ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophosphate), thus has the characteristics of them. The resulting electrode shows good stability, high accumulation efficiency and strong promotion to electron transfer. On it, chloramphenicol can produce a sensitive cathodic peak at −0.66 V (versus SCE) in pH 7.0 phosphate buffer solutions. Parameters influencing the voltammetric response of chloramphenicol are optimized, which include the composition of the film and the operation conditions. Under the optimized conditions, the peak current is linear to chloramphenicol concentration in the range of 1.0 × 10−8–6.0 × 10−6 M, and the detection limit is estimated to be 5.0 × 10−9 M after an accumulation for 150 s on open circuit. The electrode is applied to the determination of chloramphenicol in milk samples, and the recoveries for the standards added are 97.0% and 100.3%. In addition, the electrochemical reaction of chloramphenicol and the effect of single-wall carbon nanotube, gold nanoparticle and ionic liquid are discussed.