A Glassy Carbon Electrode Modified with Cellulose Nanofibrils from Ammophila arenaria for the Sensitive Detection of L-Trytophan

L-tryptophan is an essential amino acid for human health. Nanofibrillated cellulose (NFC) from marram grass (Ammophila arenaria) extracted from plants harvested in the center of Tunisia was used for the first time for the modification of a glassy carbon electrode (GCE), for the sensitive detection of L-tryptophan (Trp). After spectroscopic and morphological characterization of the extracted NFC, the GC electrode modification was monitored through cyclic voltammetry. The NFC-modified electrode exhibited good analytical performance in detecting Trp with a wide linear range between 7.5 × 10−4 mM and 10−2 mM, a detection limit of 0.2 µM, and a high sensitivity of 140.0 µA∙mM−1. Additionally, the NFC/GCE showed a good reproducibility, good selectivity versus other amino acids, uric acid, ascorbic acid, and good applicability to the detection of Trp in urine samples.

Buckling morphology of glassy nematic films with staggered director field

The photo-induced buckling of axially periodic glassy nematic films with alternating stripped director domains is explored by the F¨oppl-von K′arm′an plate theory along with a modified kinetics approach.The effects of domain widths on the critical light intensity as well as the buckling morphology are examined numerically.It is found that in most cases the buckled film forms regularly aligned dimples and protrusions,but shows large scale bending perpendicular to the periodic axis if the widths of the stripes are nearly the same.In addition,change in light intensity is shown to alter the wavenumber of the buckling pattern.These results are expected helpful to the design of shape-shifting structures with glassy nematic films.

DNA Immobilization on Nano-Gold Modified Glassy Carbon Electrode

CT-DNA were electrochemically immobilized on the surfaces of both nano-gold modified glassy carbon electrode and bare glassy carbon electrode. The cyclic voltammetric behavior of Co (phen)(3)(3+) adsorbed on the immobilized DNA was studied. Increase in the peak current of Co (phen)(3)(3+) redox reaction was obtained on nano-gold modified glassy carbon electrode. The result suggests that more DNA molecules were immobilized on this electrode and nano-gold modification can enhance the heterogeneous electron transfer rate constant of the Co (phen)(3)(3+).

Bulk Glassy Alloys: Historical Development and Current Research

This paper reviews the development of current research in bulk glassy alloys by focusing on the trigger point for the synthesis of the first bulk glassy alloys by the conventional mold casting method. This review covers the background, discovery, characteristics, and applications of bulk glassy alloys, as well as recent topics regarding them. Applications of bulk glassy alloys have been expanding, particularly for Fe-based bulk glassy alloys, due to their unique properties, high glass-forming ability, and low cost. In the near future, the engineering importance of bulk glassy alloys is expected to increase steadily, and continuous interest in these novel metallic materials for basic science research is anticipated.

Voltammetric behavior of sedative drug midazolam at glassy carbon electrode in solubilized systems

Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems,supporting electrolytes and pH using differential paise,square-wave and cyclic voltammetry.Based on its reduction behavior,a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage.Three welldefined peaks were observed in 0.1％ SLS,Britton-Robinson (BR) buffer of pH 2.5.The effect of surfaetants like sodium lauryl sulfate (SLS),cetyl trimethyl ammonium bromide (CTAB) and Tween 20 was studied.Among these surfactants SLS showed significant enhancement in reduction peak.The cathodic peak currents were directly proportional to the concentration of midazolam with correlation coetfficient of 0.99.

Electrooxidation of sulfanilamide and its voltammetric determination in pharmaceutical formulation,human urine and serum on glassy carbon electrode

For the first time, sulfanilamide(SFD) was determined in otologic solution, human urine and serum by electroanalytical techniques on glassy carbon electrode(GCE). The cyclic voltammetry(CV) experiments showed an irreversible oxidation peak at t 1.06 V in 0.1 mol/L BRBS(p H ? 2.0) at 50 m V/s. Different voltammetric scan rates(from 10 to 250 m V/s) suggested that the oxidation of SFD on the GCE was a diffusioncontrolled process. Square-wave voltammetry(SWV) method under optimized conditions showed a linear response to SFD from 5.0 to 74.7 μmol/L(R ? 0.999) with detection and quantification limits of 0.92 and3.10 μmol/L, respectively. The developed SWV method showed better results for detection limit and linear range than the chronoamperometry method. It has been successfully applied to determine SFD concentration in pharmaceutical formulation, human urine and serum samples with recovery close to 100%.

Nonlinear analysis of photo-induced wrinkling of glassy twist nematic films on compliant substrates

A kinetics approach is developed for the geometrically nonlinear analysis of photo-induced wrinkling of glassy twist nematic films on soft elastic substrates.In this way,the problem is reduced to finding the steady state of an overdamped evolution system according to a kinetic law,rather than directly solving the coupled nonlinear equations.This enables one to account for the complicated director distribution and obtain the precise wrinkling morphology of the film.Though the approach proposed here is for a twist nematic film,it can be extended to study glassy nematic films with other director distributions.

Voltammetric sensor based on cobalt-poly(methionine)-modified glassy carbon electrode for determination of estriol hormone in pharmaceuticals and urine

A voltammetric sensor based on the electropolymerization of cobalt-poly(methionine)(Co-poly(Met)) on a glassy carbon electrode (GCE) was developed and applied for the determination of estriol by differential pulse voltammetry (DPV) for the first time. The electrochemical properties of the Co-poly(Met)/GCE were analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the polymers on the GCE surface. The deposition of the Co-poly(Met) film on the GCE surface enhanced the sensor electronic transfer. CV studies revealed that estriol exhibits an irreversible oxidation peak at t0.58 V for the Co-poly(Met)/GCE (vs. Ag/AgCl reference electrode) in 0.10 mol/L Britton-Robinson buffer solution (pH=7.0). Different voltammetric scan rates (10-200 mV/s) suggested that the estriol oxidation on the Co-poly(Met)/GCE surface is controlled by adsorption and diffusion processes. Based on the optimized DPV conditions, the linear responses for estriol quantification were from 0.596 μmol/L to 4.76 μmol/L (R2 =0.996) and from 5.66 μmol/L to 9.90 μmol/L (R2 =0.994) with a limit of detection (LOD) of 0.0340 μmol/L and a limit of quantification (LOQ) of 0.113 μmol/L. The DPV-Co-poly(Met)/GCE method provided good intra-day and inter-day repeatability with RSD values lower than 5%. Also, no interference of real sample matrices was observed on the estriol voltammetric response, making the DPV-Copoly( Met)/GCE highly selective for estriol. The accuracy test showed that the estriol recovery was in the ranges 96.7%-103% and 98.7%-102% for pharmaceutical tablets and human urine, respectively. The estriol quantification in pharmaceutical tablets performed by the Co-poly(Met)/GCE-assisted DPV method was comparable to the official analytical protocols.

Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod （Fe0.87Co0.13）68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy （Fe0.87Co0.13）71.5.xGd3.sNbxB25 （x=1.2, 1.5, 2, 2.5, 3, 4） alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of （Fe0.87Co0.13）70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency （f0） was 6.1 MHz.

Direct Electrochemistry and Electrocatalysis of Hemoglobin at PAMAM Dendrimer-MWNTs-Au Nanoparticles Composite Film Modified Glassy Carbon Electrode

The direct electron transfer of hemoglobin at the PAMAM-MWNTs-AuNPs composite film modified glassy carbon electrode was studied. In a phosphate buffer solution（PBS, pH=7.0）, the formal potential（E^0） of Hb was -0.105 V versus SCE, the electron transfer rate constant was 4.66 s-1. E^0＇ of Hb at the modified electrode was linearly varied in a pH range of 5.0-8.0 with a slope of-49.2 mV/pH. The Hb/PAMAM-MWNTs-AuNPs/GCE gave an excellent electrocatalytic response to the reduction of hydrogen peroxide. The catalytic current increased linearly with H2O2 concentration in a range of 1.0× 10^-6 to 2.2× 10^-3 mol/L. The detection limit was 2.0× 10^-7 mol/L at a signal to noise ratio of 3. The Michaelis-Menten constant（Km^app） was 2.95 mmol/L.

Cyclic Voltammetry Determination of Epinephrine with a Nano-gold Modified Glassy Carbon Electrode in the Presence of High Concentration Ascorbic Acid

Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can not only catalytically oxidize EP and AA, but also separate the catalytic peak potentials of EP and AA by about 183.5 mV. In pH = 7.0 ogisogate byffer solution, the linear range of epinephrine was 5 106 ~ 1 ?10-4 mol/L.

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantihication of antihistamine drug pheniramine in solubilized systems

A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate.The experimental results suggest that the phcniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response.Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987.The limit of detection is 58.31 μg/m L.The modified electrode shows good sensitivity and repeatability.

Fixation for the helical structure of a glassy cholesteric liquid crystal reflective film

The planar texture of glassy cholesteric siloxane cyclic side-chain liquid crystals was fixed by quenching initially. Then the polymer network formed by the optically active polymerizable monomers imposed additional constraints on the motion of chain segments of the glassy liquid crystal and then further stabilized the molecule arrangement. A cholesteric liquid crystal film with stable optical properties was developed by this method.

NUCLEATION BEHAVIOURS OF SILVER ON GLASSY CARBON MICROELECTRODES

The initial stage of silver deposition has been investigated using the microelectrode technique A disc shaped nucleus can be obtained on glassy carbon microelectrodes and the instanta. neous nucleation model applies for the process

Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon

Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003300380032003500380030003900310035000000 [2] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003300380032003500380030003900320030000000 . The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in glassy carbon. In this paper, the determination of the mechanical properties of glassy carbon allows the analysis of reliability of structures in glassy carbon.

A Functionalized Multi-walled Carbon Nanotube and Gold Nanoparticle Composite-modified Glassy Carbon Electrode for the Detection of Enterovirus 71

Hand, foot, and mouth disease (HFMD) is a common infectious disease in children, occurring primarily in preschool children[1_3] with infants under three years old being gen erally susceptible. The disease is caused by various enteroviruses, among which EV71 and Coxsackievirus A group 16 (Cox A16) are the most comm on ⑷.According to in formation released by the Chinese Center for Disease Control and Prevention on June 8, 2016, EV71 infection- related HFMD has been prevalent among infants and young children in China since 2007, with a high incidenee and many deaths.

Interaction of glassy fertilizers and Cd^(2+) ions in terms of soil pollution neutralization

Immobilization of cadmium contamination in soils by precipitation of nonassimilable for plants Cd-phosphates was considered. Glassy fertilizer of controlled release rate of the nutrients for plants as a source of phosphate anions was applied. The negative role of Cd complexing citric acid solution simulating the natural soil conditions, which inhibits the Cd-phos-phates formation, was stated.

Voltammetric Response and Electrocatalysis of Glassy Carbon Electrode Modified with Monolayer Nickel Hydroxide

The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.

Effect of repeated melting of the mother ingot on the thermal stability of a Zr6oAl15Ni25 bulk glassy alloy

The effect of repeated melting of the mother ingot on the thermal stabilityof a Zr_(60)Al_+(15)Ni_(25) glassy alloy was investigated by differential scanning calorimetry(DSC). Experimental results indicate that after the repeated melting of the ingots at 1300 and 1580K, the glass transition temperature T_g increases from 686.4 to 690.7 and 696.8 K and the onsettemperature of crystallization T_x from 757.9 to 758.6 and 763.4 K, respectively, indicating thatthe thermal stability becomes higher after the repeated arc melting of the mother ingot and that itis more effective at higher temperature. Within the framework of structure heredity, the origin ofthe improvement of the thermal stability of Zr_(60)Al_+(15)Ni_(25) bulk glassy alloy is discussed.

Surface Modification and Model of Glassy Cementitious Materials

Basic theory of surface modification about glassy cementitous materials is presented. At the same time modified glassy cementitous materials were manufactured by means of point activation and disperse and grind aid according to technology of mechanical-chemistry. This theory about surface modification has been proved by some experimental results such as SEM, size distribution, fluidity of the paste, physical-mechanical properties of the hardened paste and heat of the hydration. The particle size of modified fly ash is tending to become smaller and the shape of microfine particles seems a ball; strength of modified glassy cementitous materials and ordinary portland cement compound paste has a obvious increment and fluidity of the paste also has a noticeable improvement; surface modification also can accelerate the formation of paste structure to a certain degree. Besides a model about the interactive mechanism of modified glassy cementitous materials and ordinary portland cement is put forward.