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Films
Kinds of Films Terms modified by Films Selected AbstractsFILM FORMING MECHANISM AND MECHANICAL AND THERMAL PROPERTIES OF WHEY PROTEIN ISOLATE-BASED EDIBLE FILMS AS AFFECTED BY PROTEIN CONCENTRATION, GLYCEROL RATIO AND PULLULAN CONTENTJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2010MAHAMADOU ELHADJI GOUNGA ABSTRACT Tensile strength (TS), elongation at break (EAB) and elastic modulus (EM) of edible films prepared from 5, 7 and 9% whey protein isolate (WPI) plasticized with different levels of glycerol (Gly) (WPI : Gly = 3.6:1, 3:1 and 2:1) were investigated in order to completely characterize WPI-Gly films. On increasing protein concentration an increase in TS and EAB was observed. On the other hand, increasing Gly led to a decrease in TS and EM, while EAB increased. The addition of pullulan (Pul) into the film forming solution (FFS) increased EAB while TS, EM and thermal properties were reduced. This suggested that Pul had a similar effect as plasticizers. Films with higher Pul content showed lighter protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fourier transform infrared spectroscopy showed that hydrogen bonding was high in WPI : Pul films as compared with the control. This is attributed to the protein-polysaccharide interactions brought about by the dominance of Pul in the FFS. PRACTICAL APPLICATIONS This work describes some physical properties of films based on blends of whey protein isolate (WPI) and pullulan (Pul), made after a previous study on some characteristics of films based on pure WPI plasticized by glycerol. The most studied proteins in the edible films technology being gluten and WPI, the use of Pul in mixture with WPI is considered as a new investigation to explore the utilization of WPI-Pul in edible film and coating materials applied to food products. Furthermore, the use of WPI-Pul films and coatings could potentially extend the shelf life and improve the stability of the coated products as shown by the resultant properties in this investigation and previous works. [source] EFFECT OF DIFFERENT METHODS FOR APPLICATION OF AN ANTIFOG SHRINK FILM TO MAINTAIN CAULIFLOWER QUALITY DURING STORAGEJOURNAL OF FOOD QUALITY, Issue 3 2003J. R. DeELL The antifog shrink film improved quality retention and cauliflower packaged using any of the four methods exhibited less weight loss than controls (unwrapped) after 23 days in storage at 0,1C or 10C. The overwrap and sealed bag treatments resulted in higher appearance ratings and less curd browning and butt discoloration after storage at 0,1C. Shrinking the film with heat and/or vacuum may have damaged the tissue, providing a more favorable environment for microorganism growth, since more decay was found on these curds. [source] RIPENING AND QUALITY CHANGES IN MANGO FRUIT AS AFFECTED BY COATING WITH AN EDIBLE FILMJOURNAL OF FOOD QUALITY, Issue 5 2000A. CARRILLO-LOPEZ ABSTRACT Mango fruit has a relatively short storage life of about 2 to 3 weeks at 13C. In order to prolong the storage life of ,Haden' mangoes, fruit were coated with 3 concentrations (8,16 and 24 g.L,1) of the edible coating film "Semperfresh" and then stored at 13C and 85% RH. Fruit were then evaluated every 4 days for up to 32 days for total soluble solids (TSS), titratable acidity (TA), pH, firmness, weight loss, color of the skin, and ascorbic acid content. All 3 concentrations applied to the fruit affected fruit ripening. TA, firmness, and green color were higher in coated fruit, and weight loss, SST, and pH were lower compared with the noncoated fruit. "Semperfresh" had no effect on decay development. Ascorbic acid decreased in all stored fruit, but this decrease was slower in coated fruit, and there were no significant differences between the different "Semperfresh" concentrations. [source] THE CONTINUUM COMPANION TO RELIGION AND FILM edited by William L. Blizek FILM, LACAN AND THE SUBJECT OF RELIGION: A PSYCHOANALYTIC APPROACH TO RELIGIOUS FILM ANALYSIS by Steve NolanNEW BLACKFRIARS, Issue 1035 2010KEITH TESTER No abstract is available for this article. [source] FILM FORMING MECHANISM AND MECHANICAL AND THERMAL PROPERTIES OF WHEY PROTEIN ISOLATE-BASED EDIBLE FILMS AS AFFECTED BY PROTEIN CONCENTRATION, GLYCEROL RATIO AND PULLULAN CONTENTJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2010MAHAMADOU ELHADJI GOUNGA ABSTRACT Tensile strength (TS), elongation at break (EAB) and elastic modulus (EM) of edible films prepared from 5, 7 and 9% whey protein isolate (WPI) plasticized with different levels of glycerol (Gly) (WPI : Gly = 3.6:1, 3:1 and 2:1) were investigated in order to completely characterize WPI-Gly films. On increasing protein concentration an increase in TS and EAB was observed. On the other hand, increasing Gly led to a decrease in TS and EM, while EAB increased. The addition of pullulan (Pul) into the film forming solution (FFS) increased EAB while TS, EM and thermal properties were reduced. This suggested that Pul had a similar effect as plasticizers. Films with higher Pul content showed lighter protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fourier transform infrared spectroscopy showed that hydrogen bonding was high in WPI : Pul films as compared with the control. This is attributed to the protein-polysaccharide interactions brought about by the dominance of Pul in the FFS. PRACTICAL APPLICATIONS This work describes some physical properties of films based on blends of whey protein isolate (WPI) and pullulan (Pul), made after a previous study on some characteristics of films based on pure WPI plasticized by glycerol. The most studied proteins in the edible films technology being gluten and WPI, the use of Pul in mixture with WPI is considered as a new investigation to explore the utilization of WPI-Pul in edible film and coating materials applied to food products. Furthermore, the use of WPI-Pul films and coatings could potentially extend the shelf life and improve the stability of the coated products as shown by the resultant properties in this investigation and previous works. [source] EFFECT OF OLIVE OIL AND GLYCEROL ON PHYSICAL PROPERTIES OF WHEY PROTEIN CONCENTRATE FILMSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2008MAJID JAVANMARD ABSTRACT Olive oil was incorporated into whey protein through emulsification to produce films. Whey protein films were prepared by dispersing 10% protein in distilled water; and plasticized with different levels of glycerol (glycerol : protein [Gly : pro ] = 0.5 and 0.6). Olive oil was added at different levels (oil : pro = 0.0, 0.2, 0.3 and 0.4). The emulsion films were evaluated for mechanical properties, water vapor permeability (WVP) and opacity. Increasing the levels of Gly or olive oil in the films led to decreases in modulus and tensile strength. Increasing Gly content of films at oil/pro ratios of 0.2, 0.4 led to slight increases in elongation (EL). Increasing the oil : pro ratio further resulted in a decrease in EL for all films. No significant difference in WVP and opacity was observed between films made from mixtures of various proportions of whey protein concentrate,Gly with increasing olive oil (addition) at all levels of the plasticizer. PRACTICAL APPLICATIONS The main advantages of using edible films are extending food shelf life, improving food quality, adding value to the edible film-forming polymer and reducing synthetic packaging materials. Whey, obtained as a by-product in cheese, is produced in large quantities and has excellent functional properties and could potentially be used for edible films. [source] OXYGEN TRANSMISSION RATE THROUGH MICRO-PERFORATED FILMS: MEASUREMENT AND MODEL COMPARISONJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2001V. GHOSH ABSTRACT Static and flow-through techniques were used to experimentally measure the oxygen transmission rate of micro-perforated films. The static method simulates the actual package conditions but is very time consuming. Whereas, the flow-through method is relatively simple and takes less time to give the results, but it gave higher values than that obtained by the static method. A regression equation was developed to correlate the data obtained by these two methods. Published models for predicting gas exchange through micro-perforations were evaluated. The predicted data by these models were compared with the experimental data obtained by the static method and the flow-through method for six different films. The model proposed by Fishman et al. (1996) (J=-D(c-cA)/Lh; Lh= thickness of the film + radius of the perforation) had very good agreement with the experimental data from the static method. [source] EFFECT OF GLYCEROL ON PHYSICAL PROPERTIES OF CASSAVA STARCH FILMSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2010P. BERGO ABSTRACT In this work, the effect of glycerol on the physical properties of edible films were identified by X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared (FTIR) and microwave spectroscopy. According to XRD diffractograms, films with 0 and 15% glycerol displayed an amorphous character, and a tendency to semicrystallization, for films with 30% and 45% glycerol. From DSC thermograms, the glass transition (Tg) of the films decreased with glycerol content. However, two Tgs were observed for samples with 30% and 45% glycerol, due to a phase separation. The intensity and positions of the peaks in FTIR fingerprint region presented slight variations due to new interactions arising between glycerol and biopolymer. Microwave measurements were sensitive to moisture content in the films, due to hydrophilic nature of the glycerol. The effect of plasticizer plays, then, an important rule on the physical and functional properties of these films, for applications in food technology. PRACTICAL APPLICATIONS Edible and/or biodegradable films are thin materials used mainly in food recovering, food packaging and other applications, in substitution of the films obtained by synthetic ways. In view of these applications, these films must satisfy some of the exigencies in order to increase the food shelf-life, or in other words, they must be flexible, transparent, resistant to some gases such as oxygen, as well as resistant to water vapor. The addition of plasticizers alters the functional properties of the films. Thus, the physical characterization of these films becomes fundamental in order to increase their potential use in industry. [source] EFFECT OF POLYGODIAL ON MECHANICAL, OPTICAL AND BARRIER PROPERTIES OF CHITOSAN FILMSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2010L. MORENO-OSORIO ABSTRACT The mechanical, optical and barrier properties of chitosan films containing polygodial (0.0, 2.7, 13.9, 25.0 mg/g of chitosan) were studied. Water vapor permeability (WVP), tensile strength, percentage elongation at break, CIELab color parameters, hue angle and chroma of films were determined. Fourier transform infrared (FTIR) was also performed to determine functional group interaction between the matrix and polygodial added. The use of polygodial resulted in stronger films without losing their extensibility and with low WVP. Films became darker with yellow-green coloration with increasing polygodial concentration. Polygodial added to chitosan films did not have any interaction with the amino groups of chitosan as measured by FTIR. Polygodial as a natural dialdehyde can effectively be applied to enhance some physical properties of edible films prepared with chitosan. PRACTICAL APPLICATIONS There has been an increased interest in the study of edible,biodegradable packaging films during the last decade, offering an alternative and partial solution to the problem of accumulation of solid waste composed of synthetic inert polymers, and chitosan films has been studied with this purpose. Furthermore, replacing synthetic additives by natural compounds such us polygodial can be a suitable manner to improve some physical properties of those chitosan films. [source] EFFECT OF HEADSPACE OXYGEN AND FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN RAINBOW TROUT FILLETS STORED UNDER MODIFIED ATMOSPHERESJOURNAL OF FOOD SAFETY, Issue 3 2000ISABELLE DUFRESNE ABSTRACT Studies were conducted to determine the effect of various levels of headspace oxygen (0,100%, balance CO2) or film oxygen transmission rate (OTR) on the time to toxicity in modified atmosphere packaged (MAP) fresh trout fillets challenged with C. botulinum type E (102 spore/g) and stored under moderate temperature abuse conditions (12C). In all cases, trout were toxic within 5 days, irrespective of the initial levels of oxygen in the package headspace. However, spoilage preceded toxigenesis. Packaging of trout fillets in low gas barrier films, with OTRs ranging from 4,000 to 10,000 cc/m2/day at 24C and 0% relative humidity, also had no effect on time to toxicity in all MAP trout fillets. All fillets were toxic within 4,5 days and spoilage again preceded toxigenesis. This study has shown that the addition of headspace O2, either directly to a package or indirectly by using a low gas barrier film, had no influence on the time to toxigenesis or spoilage. Additional barriers, other than headspace O2 or film transmission rate, need to be considered to ensure the safety of MAP trout fillets, particularty at moderate temperature abuse conditions. [source] FROM WOMEN'S WORK TO THE UMBILICAL LENS: MARY KELLY'S EARLY FILMSART HISTORY, Issue 1 2008SIONA WILSON This essay presents a historical and theoretical account of Mary Kelly's formative involvement in experimental filmmaking in Britain during the early- to mid-1970s. The argument develops by tracing the complex interconnections between Kelly's political engagement with Marxist-feminism and her theoretical involvement with psychoanalysis and film theory. After discussing Kelly's participation in the Berwick Street Film Collective's Night Cleaners (1975) and the London Women's Film Group's Women of the Rhondda (1973), I present a sustained close reading of the artist's first solo work, the film loop installation Antepartum (1974). I argue that Antepartum interpellates the spectator into a feminine subject position. This reading of the film draws upon recent post-Lacanian feminist scholarship in philosophical ethics that focuses on the intrauterine relation. Antepartum offers a politically informed aesthetic experiment that prefigures some of these insights. [source] Politics and Film: A letter to the Secretary of State, Department for Culture, Media and SportCRITICAL QUARTERLY, Issue 1-2 2008COLIN MacCABE No abstract is available for this article. [source] Film: State of Cinema Address: 49th San Francisco International Film Festival, 29 April 2006CRITICAL QUARTERLY, Issue 3 2006TILDA SWINTON Letter to a boy from his mother Boy, my darling, You asked me the other day, just as you were dropping off, what people's dreams were like before the cinema was invented. You who talk blabberish and chase rabbits in your sleep, hurrumphing like a dog . . . you who never watch television . . . I've been thinking of your question ever since. I have to talk to some people in America about cinema. I'm going there now on the plane and I can't think of anything but your question... [source] Film: ,We shouldn't be doing this',The Navigators: Stories from the TracksideCRITICAL QUARTERLY, Issue 1 2002Richard Kelly First page of article [source] Film: Bravely in harm's way: A report from the 55th Edinburgh International Film FestivalCRITICAL QUARTERLY, Issue 4 2001Richard Kelly First page of article [source] The Ideological Implications of Using "Educational" Film to Teach Controversial EventsCURRICULUM INQUIRY, Issue 3 2009JEREMY D. STODDARD ABSTRACT Use of media in today's classrooms, from feature and documentary film to news clips streamed via the Web, has grown exponentially. Film can be a powerful medium for teaching and learning, but is often viewed as a neutral source of information. This collective case study focuses on two teachers who use documentary film to teach about controversial events, with the goal of better understanding teacher selection and use of film as part of pedagogy and the experiences of students who are engaged in deliberative activities with film. In this case, teachers utilized film to help students examine two controversial events in U.S. history, the use of atomic weapons against Japan at the end of World War II and the role of the United States in Vietnam. These cases illustrate a tension that many teachers, who want to engage students in deliberative activities but who also want students to adopt particular moral or political stances, face in today's classrooms. The teachers in these cases utilize film as a neutral source for students to use as evidence for taking a position, despite the value-laden perspectives included in the films, perspectives that aligned with the teachers' own political beliefs. Other findings include student inability to recognize the perspectives in documentary films, the epistemic stances of teachers and students that documentaries are accurate and neutral, and the characteristics of students who are better equipped to recognize ideological perspectives. Implications for teachers, teacher educators, and especially democratic and social studies education researchers are explored. [source] Humor im deutschen Film?DIE UNTERRICHTSPRAXIS/TEACHING GERMAN, Issue 2 2005Kein Oxymoron in Good Bye Lenin! und Sonnenallee: Vorschläge für den DaF-Unterricht auf der Mittel- und Oberstufe [source] A Novel Polycatechol/Ordered Mesoporous Carbon Composite Film Modified Electrode and Its Electrocatalytic ApplicationELECTROANALYSIS, Issue 15 2010Jing Bai Abstract Polycatechol (PCC) was prepared by electropolymerizing catechol (CC) on the surface of an ordered mesoporous carbon (OMC) modified electrode for the first time. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to characterize the structure and electrochemical behaviors of PCC/OMC nanocomposite film. Compared with the bare GC and OMC/GC electrodes, the PCC/OMC/GC electrode exhibits a good electrocatalysis toward the oxidation of NADH at 0.0,V with a high sensitivity (8.7 mA/mM). These make PCC/OMC/GC electrode a promising candidate for stable and efficient electrochemical sensors for the detection of NADH. [source] Fabrication of Nanoporous Copper Film for Electrochemical Detection of GlucoseELECTROANALYSIS, Issue 21 2009Sirilak Sattayasamitsathit Abstract A nanoporous copper film was fabricated on a copper wire by electrodeposition of copper/zinc alloy and chemically etching of zinc. The surface morphology was investigated by SEM. When applied to detect glucose in an amperometric flow injection system the porous copper electrode provided 12 times higher sensitivity than solid copper. It could be continuously used up to 50 times (%RSD=5.7). Different preparations of the porous film provided reproducible responses (P<0.05). Detection of glucose in E. coli cultivation medium compared well with spectrophotometric technique (P<0.05). This simple technique can produce a nanoporous electrode with good performances and can easily be applied to other metals and analytes. [source] Multiwalled Carbon Nanotubes Encased in Ruthenium Oxide Film as a Hybrid Material for Neurotransmitters SensorELECTROANALYSIS, Issue 16 2009Chien-Chieh Ti Abstract A hybrid film (MWCNTs-RuOx,nH2O) which contains multiwalled carbon nanotubes (MWCNTs) along with the incorporation of ruthenium oxide (RuOx,nH2O) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of MWCNTs in the hybrid film enhances surface coverage concentration (,) of RuOx,nH2O to ,2100%. The surface morphology of the hybrid film deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy. These two techniques reveal that the RuOx,nH2O incorporated on MWCNTs. Electrochemical quartz crystal microbalance study too reveals the incorporation of MWCNTs and RuOx,nH2O. The MWCNTs-RuOx,nH2O hybrid film exhibits promising enhanced electrocatalytic activity towards the biochemical compounds such as epinephrine and norepinephrine. The electrocatalytic responses of these analytes at RuOx,nH2O, MWCNTs and MWCNTs-RuOx,nH2O hybrid films have been measured using cyclic voltammetry. The obtained sensitivity values from electrocatalysis studies of analytes for MWCNTs-RuOx,nH2O hybrid film are higher than the RuOx,nH2O and MWCNTs films. Finally, the flow injection analysis has been used for the amperometric studies of analytes at MWCNTs-RuOx,nH2O hybrid film modified SPCEs. [source] Reagentless Biosensor for Hydrogen Peroxide Based on the Immobilization of Hemoglobin in Platinum Nanoparticles Enhanced Poly(chloromethyl thiirane) Cross-linked Chitosan Hybrid FilmELECTROANALYSIS, Issue 12 2009Shanshan Jia Abstract An unmediated hydrogen peroxide (H2O2) biosensor was prepared by co-immobilizing hemoglobin (Hb) with platinum nanoparticles enhanced poly(chloromethyl thiirane) cross-linked chitosan (CCCS-PNs) hybrid film. CCCS could provide a biocompatible microenvironment for Hb and PNs could accelerate the electron transfer between Hb and the electrode. Spectroscopic analysis indicated that the immobilized Hb could maintain its native structure in the CCCS-PNs hybrid film. Entrapped Hb exhibited direct electrochemistry for its heme Fe(III)/Fe(II) redox couples at ,0.396,V in the CCCS-PNs hybrid film, as well as peroxidase-like activity to the reduction of hydrogen peroxide without the aid of an electron mediator. [source] Electrochemical Cholesterol Sensor Based on Tin Oxide-Chitosan Nanobiocomposite FilmELECTROANALYSIS, Issue 8 2009Anees Abstract A chitosan (CS)-tin oxide (SnO2) nanobiocomposite film has been deposited onto an indium-tin-oxide glass plate to immobilize cholesterol oxidase (ChOx) for cholesterol detection. The value of the Michaelis,Menten constant (Km) obtained as 3.8,mM for ChOx/CS-SnO2/ITO is lower (8,mM) than that of a ChOx/CS/ITO bioelectrode revealing enhancement in affinity and/or activity of ChOx towards cholesterol and also revealing strong binding of ChOx onto CS-SnO2/ITO electrode. This ChOx/CS-SnO2/ITO cholesterol sensor retains 95% of enzyme activity after 4,6 weeks at 4,°C with response time of 5,s, sensitivity of 34.7,,A/mg dL,1 cm2 and detection limit of 5,mg/dL. [source] Electrochemical Properties of Ordered Mesoporous Carbon Film Adsorbed onto a Self-Assembled Alkanethiol Monolayer on Gold ElectrodeELECTROANALYSIS, Issue 2 2009Dan Zheng Abstract A stable ordered mesoporous carbon (OMC) film electrode was successfully constructed by adsorbing OMC onto a self-assembled monolayer (SAM) of C18H37SH chemisorbed on the Au electrode. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and electrochemical methods were used to characterize the properties of the OMC film electrode. The adsorbed OMC can restore the heterogeneous electron transfer almost totally blocked by the alkanethiol monolayer. Nyquist plots show a sharply decrease of the charge transfer resistance (Rct) of the Fe(CN) couple at the OMC film electrode. Furthermore, the OMC film electrode is found to possess a significantly reduced interfacial capacitance and largely enhanced current response of hydrogen peroxide. This novel approach to the fabrication of stable OMC film electrode with excellent electrochemical properties is believed to be very attractive for electrochemical studies and electroanalytical applications. [source] An Organic Sol-Gel Film as Modifier to Construct BiosensorELECTROANALYSIS, Issue 2 2009Jian-Feng Wu Abstract A new amperometric biosensor for hydrogen peroxide (H2O2) was developed by adsorbing hemoglobin (Hb) on an organic sol-gel film. The organic sol-gel was prepared using resorcinol and formaldehyde as monomers. This sol-gel film shows a biocompatible microenvironment for retaining the native activity of the adsorbed Hb. The direct electron transfer between Hb and electrode is achieved. Hb adsorbed on the film shows an enzyme-like catalytic activity for the reduction of H2O2. The reduction peak currents are proportional linearly to the concentration of hydrogen peroxide in the range of 6×10,8 to 3.6×10,6,M, with a detection limit of 2.4×10,8,M (S/N=3). This research enlarges the applications of organic sol-gel materials in biosensor field. [source] Preparation, Electrochemistry, and Electrocatalytic Activity of Lead Pentacyanonitrosylferrate Film Immobilized on Carbon Ceramic ElectrodeELECTROANALYSIS, Issue 21 2008H. Razmi Abstract Lead pentacyanonitrosylferrate (PbPCNF), a new Prussian blue analog, was immobilized on the surface of a carbon ceramic electrode (CCE) prepared by sol-gel method. The immobilization process consists of adding a certain amount of metallic lead to the electrode matrix before gelation, and chemical derivatization of Pb on the electrode surface to a PbPCNF solid film by immersing the electrode in a solution of sodium pentacyanonitrosylferrate (PCNF). The composition of the synthesized PbPCNF was characterized by FTIR, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) techniques. The resulting modified electrode showed electroactivity at two redox centers. The electrochemical behavior of the PbPCNF modified carbon ceramic electrode (PbPCNF|CCE) was studied by cyclic voltammetry. Under optimized conditions the peak-to-peak separation is only 39,mV, indicative of a surface reaction. Ion effects of the supporting electrolyte suggest that cations have a considerable effect on the electrochemical behavior of the modified electrode. The transfer coefficient (,) and the charge transfer rate constant at the modifying film|electrode interface (ks) were calculated. The electrocatalytic activity of the modified electrode toward the electro-reduction of peroxodisulfate was studied in details. [source] Comparison of Electrochemical and Surface Plasmon Resonance Immunosensor Responses on Single Thin FilmELECTROANALYSIS, Issue 20 2008Ryoji Kurita Abstract This paper reports results obtained when comparing an electrochemical enzyme immunosensor and a surface plasmon resonance (SPR) based immunosensor on the same gold surface installed in an electrochemical SPR flow cell. Simultaneous electrochemical and SPR measurements were performed on a gold surface modified with multilayers of poly- L -lysine and poly-styrenesulfonate assembled with the layer-by-layer method. First, we obtained the SPR response induced by the formation of an immunocomplex from the shift in the SPR angle by injecting an anti tumor necrosis factor-, antibody solution labeled with alkaline phosphatase into the flow cell containing the multilayer modified with tumor necrosis factor-,. Then we compared this SPR result with that obtained for the electrochemical oxidation current of p -aminophenol catalyzed by alkaline phosphatase from p -aminophenolphosphate on the same gold film. We compared the two immunosensor responses obtained using the different measurement principles and found that there was a high correlation efficient of 0.973 between them. This was because we were able to immobilize the immunoreagents with good stability and without losing the transport of the enzyme product in the multilayer whose thickness we easily controlled with nanometer scale accuracy. We also report that the detection limit of our electrochemical immunosensor after optimization was around 100,pg/mL (0.4,pM), which is one of the lowest values yet reported for an electrochemical immunosensor. [source] Direct Electrochemistry and Electrocatalysis of Myoglobin Immobilized on Gold Nanoparticles/Carbon Nanotubes Nanohybrid FilmELECTROANALYSIS, Issue 17 2008Wei Cao Abstract A novel nanohybrid material, constructed by gold nanoparticles (GNPs) and multiwalled carbon nanotubes (MWNTs), was designed for immobilization and biosensing of myoglobin (Mb). Morphology of the nanohybrid film was characterized by SEM. UV-vis spectroscopy demonstrated that Mb on the composite film could retain its native structure. Direct electrochemistry of Mb immobilized on the GNPs/MWNTs film was investigated. The immobilized Mb showed a couple of quasireversible and well-defined cyclic voltammetry peaks with a formal potential of about ,0.35,V (vs. Ag/AgCl) in pH,6.0 phosphate buffer solution (PBS) solution. Furthermore, the modified electrode also displayed good sensitivity, wide linear range and long-term stability to the detection of hydrogen peroxide. The experiment results demonstrated that the hybrid matrix provided a biocompatible microenvironment for protein and supplied a necessary pathway for its direct electron transfer. [source] Properties of Poly(sodium 4-styrenesulfonate)-Ionic Liquid Composite Film and Its Application in the Determination of Trace Metals Combined with Bismuth Film ElectrodeELECTROANALYSIS, Issue 5 2008Jianbo Jia Abstract A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF6) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4-styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)64,/Fe(CN)63, can be effectively improved at the PSS-BMIMPF6 modified GC. The bismuth modified PSS-BMIMPF6 composite film electrodes (GC/PSS-BMIMPF6/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS-BMIMPF6/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50,,g L,1. And the detection limits were 0.07,,g L,1 for Cd(II) and 0.09,,g L,1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120,s, respectively. Finally, the GC/PSS-BMIMPF6/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy. [source] Preparation, Characterization and Electrocatalytic Studies on Copper Complex Dye Film Modified ElectrodesELECTROANALYSIS, Issue 13 2007Shen-Ming Chen Abstract Copper complex dye (C.I. Direct Blue 200) film modified electrodes have been prepared by multiple scan cyclic voltammetry. The effect of solution pH and nature of electrode material on film formation was investigated. The optimum pH for copper complex film formation on glassy carbon was found to be 1.5. The mechanism of film formation on ITO seems to be similar to that on GC surface but completely different mechanism followed with gold electrode. Cyclic voltammetric features of our modified electrodes are in consistent with a surface-confined redox process. The voltammetric response of modified electrode was found to be depending on pH of the contacting solution. UV-visible spectra show that the nature of copper complex dye is identical in both solution phase and after forming film on electrode. The electrocatalytic behavior of copper complex dye film modified electrode towards oxidation of dopamine, ascorbic acid and reduction of SO52, was investigated. The oxidation of dopamine and ascorbic acid occurred at less positive potential on film electrode compared to bare glassy carbon electrode. Feasibility of utilizing our modified electrode in analytical estimation of dopamine, ascorbic acid was also demonstrated. [source] Differential Pulse Voltammetric Determination of Selenocystine Using Selenium-gold Film Modified ElectrodeELECTROANALYSIS, Issue 17 2005Yan Bai Abstract Differential pulse voltammetric determination of selenocystine (SeC) using selenium-gold film modified glassy carbon electrode ((Se-Au)/GC) is presented. In 0.10,mol,L,1 KNO3 (pH,3.20) solution, SeC yields a sensitive reduction peak at ,740,mV on (Se-Au)/GC electrode. The peak current has a linear relationship with the concentration of SeC in the range of 5.0×10,8,7.0×10,4,mol,L,1, and a 3, detection limit of SeC is 3.0×10,8,mol,L,1. The relative standard deviation of the reduction current at SeC concentration of 10,6,mol,L,1 is 3.88% (n=8) using the same electrode, and 4.19% when using three modified electrodes prepared at different times. The content of SeC in the selenium-enriched yeast and selenium-enriched tea is determined. The total selenium in ordinary or selenium-enriched tea is determined by DAN fluorescence method. The results indicate that in selenium-enriched yeast about 20% of total selenium is present as SeC and in selenium-enriched tea SeC is the major form of selenoamino acids. The total selenium content in selenium-enriched tea soup is 0.09,,gSe/g accounting by 7% compared with that in selenium-enriched tea. Hence, only a little amount of selenium is utilized by drinking tea, and most selenium still stay in tealeaf. Uncertainty are 22.4% and 16.1% for determination of SeC in selenium-enriched yeast and selenium-enriched tea by differential pulse voltammetry (DPV) on (Se-Au)/GC electrode, respectively. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||