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Taihyun Chang - One of the best experts on this subject based on the ideXlab platform.
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structure and thermal stability of cadmium arachidate poly tert butyl methacrylate alternating Langmuir Blodgett Film
Synthetic Metals, 2001Co-Authors: Junhoe Cha, Yoon Ki See, Jungmin Lee, Taihyun ChangAbstract:Abstract Layer structure and thermal stability of alternating Langmuir–Blodgett (LB) Films of cadmium arachidate (CdA 2 ) and poly( tert -butyl methacrylate) (PtBMA) was investigated by X-ray reflection and in-plane diffraction study. The LB Films were deposited on hydrophobically pre-treated silicon wafer surface and the polymer layers are inserted between CdA 2 bilayers. Layer spacing of the alternating LB Film increases linearly by 9.8 A per PtBMA layer, which is consistent with the single layer spacing of homo-PtBMA LB Film. Lateral lattice structure of CdA 2 in alternating LB Films maintains its hexagonal packing structure as found in CdA 2 monolayers while the multilayer CdA 2 LB Film is known to change its structure from hexagonal to orthorhombic lattice. Therefore, the polymer layers inserted between CdA 2 bilayers in the alternating LB Films effectively prevent the CdA 2 Film not only from the growth of defect but also from the formation of three-dimensional crystallites of CdA 2 . In addition, the hexagonal packing structure of CdA 2 bilayer was maintained up to 90°C while the molecular area increases slightly.
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x ray diffraction study of cadmium arachidate poly tert butyl methacrylate alternating Langmuir Blodgett Film
Langmuir, 1999Co-Authors: Junhoe Cha, Yongjun Park, Ki Bong Lee, Taihyun ChangAbstract:The layer structure of alternating Langmuir−Blodgett (LB) Films of cadmium arachidate (CdAA2) and poly(tert-butyl methacrylate) (PtBMA) was investigated by an X-ray reflection and in-plane diffraction study. The LB Films were deposited on a silicon wafer surface pretreated hydrophobically by transferring a behenic acid monolayer, and two or four PtBMA layers are inserted between each CdAA2 bilayer. While CdAA2 homo-LB Films are known to show gradual deterioration of the transfer ratio as the number of accumulated layers increases, the alternating LB Films maintain the transfer ratio near unity up to 32 layers. The layer spacing of the alternating LB Films determined from the position of the Bragg diffraction peaks increases linearly by 9.9 A per PtBMA layer. The lateral lattice structure of CdAA2 in alternating LB Films maintains its hexagonal packing structure, as found in CdAA2 monolayers, while the multilayer CdAA2 LB Film is known to change its structure from hexagonal to orthorhombic lattice. The spa...
Junhoe Cha - One of the best experts on this subject based on the ideXlab platform.
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structure and thermal stability of cadmium arachidate poly tert butyl methacrylate alternating Langmuir Blodgett Film
Synthetic Metals, 2001Co-Authors: Junhoe Cha, Yoon Ki See, Jungmin Lee, Taihyun ChangAbstract:Abstract Layer structure and thermal stability of alternating Langmuir–Blodgett (LB) Films of cadmium arachidate (CdA 2 ) and poly( tert -butyl methacrylate) (PtBMA) was investigated by X-ray reflection and in-plane diffraction study. The LB Films were deposited on hydrophobically pre-treated silicon wafer surface and the polymer layers are inserted between CdA 2 bilayers. Layer spacing of the alternating LB Film increases linearly by 9.8 A per PtBMA layer, which is consistent with the single layer spacing of homo-PtBMA LB Film. Lateral lattice structure of CdA 2 in alternating LB Films maintains its hexagonal packing structure as found in CdA 2 monolayers while the multilayer CdA 2 LB Film is known to change its structure from hexagonal to orthorhombic lattice. Therefore, the polymer layers inserted between CdA 2 bilayers in the alternating LB Films effectively prevent the CdA 2 Film not only from the growth of defect but also from the formation of three-dimensional crystallites of CdA 2 . In addition, the hexagonal packing structure of CdA 2 bilayer was maintained up to 90°C while the molecular area increases slightly.
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x ray diffraction study of cadmium arachidate poly tert butyl methacrylate alternating Langmuir Blodgett Film
Langmuir, 1999Co-Authors: Junhoe Cha, Yongjun Park, Ki Bong Lee, Taihyun ChangAbstract:The layer structure of alternating Langmuir−Blodgett (LB) Films of cadmium arachidate (CdAA2) and poly(tert-butyl methacrylate) (PtBMA) was investigated by an X-ray reflection and in-plane diffraction study. The LB Films were deposited on a silicon wafer surface pretreated hydrophobically by transferring a behenic acid monolayer, and two or four PtBMA layers are inserted between each CdAA2 bilayer. While CdAA2 homo-LB Films are known to show gradual deterioration of the transfer ratio as the number of accumulated layers increases, the alternating LB Films maintain the transfer ratio near unity up to 32 layers. The layer spacing of the alternating LB Films determined from the position of the Bragg diffraction peaks increases linearly by 9.9 A per PtBMA layer. The lateral lattice structure of CdAA2 in alternating LB Films maintains its hexagonal packing structure, as found in CdAA2 monolayers, while the multilayer CdAA2 LB Film is known to change its structure from hexagonal to orthorhombic lattice. The spa...
Fei Wang - One of the best experts on this subject based on the ideXlab platform.
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sensitive voltammetric determination of baicalein at dna Langmuir Blodgett Film modified glassy carbon electrode
Talanta, 2011Co-Authors: Fei Wang, Fangyuan Zhao, Yanzheng Zhang, Huige YangAbstract:Abstract The present paper describes to modify a double stranded DNA–octadecylamine (ODA) Langmuir–Blodgett Film on a glassy carbon electrode (GCE) surface to develop a voltammetric sensor for the detection of trace amounts of baicalein. The electrode was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). Electrochemical behaviour of baicalein at the modified electrode had been investigated in pH 2.87 Britton–Robinson buffer solutions by CV and square wave voltammetry (SWV). Compared with bare GCE, the electrode presented an electrocatalytic redox for baicalein. Under the optimum conditions, the modified electrode showed a linear voltammetric response for the baicalein within a concentration range of 1.0 × 10 −8 –2.0 × 10 −6 mol L −1 , and a value of 6.0 × 10 −9 mol L −1 was calculated for the detection limit. And the modified electrode exhibited an excellent immunity from epinephrine, dopamine, glucose and ascorbic acid interference. The method was also applied successfully to detect baicalein in the medicinal tablets and spiked human blood serum samples with satisfactory results.
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polyaniline Langmuir Blodgett Film modified glassy carbon electrode as a voltammetric sensor for determination of ag ions
Electrochimica Acta, 2010Co-Authors: Qiongyan Liu, Fei Wang, Yonghui Qiao, Shusheng ZhangAbstract:Abstract A highly sensitive electrochemical sensor made of a glassy carbon electrode (GCE) coated with a Langmuir–Blodgett Film (LB) containing polyaniline (PAn) doped with p-toluenesulfonic acid (PTSA) (LB/PAn-PTSA/GCE) has been used for the detection of trace concentrations of Ag+. UV–vis absorption spectra indicated that the PAn was doped by PTSA. The surface morphology of the PAn LB Film was characterized by atomic force microscopy (AFM). The electrochemical properties of this LB/PAn-PTSA/GCE were studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The LB/PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ag+ at pH 5.0 using linear scanning stripping voltammetry. Under the optimal experimental conditions, the stripping current was proportional to the Ag+ concentration over the range from 6.0 × 10−10 mol L−1 to 1.0 × 10−6 mol L−1, with a detection limit of 4.0 × 10−10 mol L−1. The high sensitivity, selectivity, and stability of this LB/PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag+ in water samples.
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Langmuir Blodgett Film of p tert butylthiacalix 4 arene modified glassy carbon electrode as voltammetric sensor for the determination of hg ii
Talanta, 2010Co-Authors: Fei Wang, Xiaohan Wei, Chenbin Wang, Shusheng ZhangAbstract:Abstract The π – A isotherms and UV–vis spectra of the transferred Films suggested that the monolayer of p - tert -butylthiacalix[4]arene can coordinate with Hg 2+ at the air–water surface. From these observations, a glassy carbon electrode coated with Langmuir–Blodgett Film of p - tert -butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg 2+ . Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir–Blodgett Film-modified electrode can greatly improve the measuring sensitivity of Hg 2+ . Under the selected conditions, the Langmuir–Blodgett Film-modified electrode in 0.1 mol L −1 H 2 SO 4 + 0.01 mol L −1 KCl solution shows a linear voltammetric response for Hg 2+ in the range of 5.0 × 10 −10 to 1.5 × 10 −7 mol L −1 , with a detection limit of 2.0 × 10 −10 mol L −1 . The proposed method was also applied to determine Hg 2+ in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability.
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electrochemical behavior of 8 azaguanine at dna Langmuir Blodgett modified glassy carbon electrode and its analytical application
Electroanalysis, 2009Co-Authors: Fei Wang, Lin Gao, Tianlai XingAbstract:A highly sensitive electrochemical biosensor for the detection of trace amounts of 8-azaguanine has been designed. Double stranded (ds)DNA molecules are immobilized onto a glassy carbon electrode surface with Langmuir–Blodgett technique. The adsorptive voltammetric behaviors of 8-azaguanine at DNA-modified electrode were explored by means of cyclic voltammetry and square wave voltammetry. Compared with bare glassy carbon electrode (GCE), the Langmuir–Blodgett Film modified electrode can greatly improve the measuring sensitivity of 8-azaguanine. Under the optimum experimental conditions, the Langmuir–Blodgett Film modified electrode in pH 3.0 Britton–Robinson buffer solutions shows a linear voltammetric response in the range of 5.0×10−8 to 1.0×10−5 mol L−1 with detection limit 9.0×10−9 mol L−1. The method proposed was applied successfully for the determination of 8-azaguanine in diluted human urine with wonderful satisfactory.
Mitsumasa Iwamoto - One of the best experts on this subject based on the ideXlab platform.
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electronic density of state at metal polyimide Langmuir Blodgett Film interface
IEEE International Conference on Properties and Applications of Dielectric Materials, 1997Co-Authors: Eiji Itoh, Mitsumasa IwamotoAbstract:Surface potentials of heat-treated polyimide (PI) LB Films deposited on Au, Cr and Al electrodes were measured in a dark vacuum vessel at various temperatures as a function of the number of deposited layers. The spatial charge distribution in PI LB Films on various electrodes was determined from the relationship between the surface potential and the number of deposited layers. Based on this result, distribution of the density of electronic state in PI LB Films was determined. It was experimentally shown that the charge exchange phenomena in PI LB Films at the metal/Film interface were explained with taking account of interfacial states which exist within the range of 1 nm from the interface and molecular-ion states which exist in the entire range. Further, it was found that the distribution of electronic density of states in polyimides was broadened as the temperature increases.
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electronic density of state in metal polyimide Langmuir Blodgett Film interface and its temperature dependence
Journal of Applied Physics, 1997Co-Authors: Eiji Itoh, Mitsumasa IwamotoAbstract:Surface potentials of heat-treated polyimide (PI) Langmuir–Blodgett (LB) Films deposited on Au, Cr, and Al electrodes were measured in a dark vacuum vessel at various temperatures as a function of the number of deposited layers. The potential depended on the thickness of PI LB Films and the work function of base metal electrode. The spatial charge distribution in PI LB Films on various electrodes was determined from the relationship between the surface potential and the number of deposited layers. Based on this result, distribution of the density of electronic state in PI LB Films was determined. It was experimentally shown that the electrostatic phenomena in PI LB Films at the metal/Film interface were explained taking account of surface states which exist within the range of ∼1 nm from the interface and molecular–ion states which exist in the entire range. Further, it was found that distribution of electronic density in states of polyimides was broadened with the increment of temperature.
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electronic density of state at metal polyimide Langmuir Blodgett Film interface
Applied Physics Letters, 1996Co-Authors: Eiji Itoh, Mitsumasa IwamotoAbstract:Surface potentials of heat‐treated polyimide Langmuir‐Blodgett (PI LB) Films deposited on Au, Cr and Al electrodes were measured in a dark vacuum vessel at room temperature as a function of the number of deposited layers. The potential depended on the thickness of PI LB Films and the work function of base electrode. The spatial charge distribution in PI LB Films on various electrodes was determined from the relationship between the surface potential and the number of deposited layers. Based on this result, distribution of the density of electronic state in PI LB Films was determined. It was experimentally shown that the electrostatic phenomena in PI LB Films at the metal/Film interface were explained with taking into consideration of surface states which exist within the range of ∼1 nm from the interface and molecular‐ion states which exist in the entire range.
B D Malhotra - One of the best experts on this subject based on the ideXlab platform.
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polyaniline Langmuir Blodgett Film based aptasensor for ochratoxin a detection
Biosensors and Bioelectronics, 2011Co-Authors: Nirmal Prabhakar, Zimple Matharu, B D MalhotraAbstract:Ochratoxin A (OTA) produced by Aspergillus Ochraceus and Penicillium verrucosum is a very dangerous toxin due to its toxic effects in human beings and its presence in a wide range of food products and cereals. A Langmuir-Blodgett (polyaniline (PANI)-stearic acid (SA)) Film based highly sensitive and robust impedimetric aptasensor has been developed for ochratoxin A (OTA) detection. DNA Aptamer (Apt-DNA) specific to OTA has been covalently immobilized onto mixed Langmuir-Blodgett (LB) monolayer comprising of PANI-SA deposited onto indium tin-oxide (ITO) coated glass plates. This Apt-DNA/PANI-SA/ITO aptaelectrode has been characterized using scanning electron microscopy, Fourier transform-infrared spectroscopy, contact angle measurements, cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The Apt-DNA/PANI-SA/ITO aptasensor shows detection of OTA by electrochemical impedance spectroscopy in the linear range of 0.0001 μg/ml (0.1 ng/ml) to 0.01 μg/ml (10 ng/ml) and 1 μg/ml-25 μg/ml with detection limit of 0.1 ng/ml in 15 min. The Apt-DNA/PANI-SA/ITO aptasensor can be reused ∼13 times. The binding or affinity constant (K(a)) of aptamer with OTA, calculated using Langmuir adsorption isotherm, is found be 1.21×10(7) M(-1).
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functionalized gold nanoparticles octadecylamine hybrid Langmuir Blodgett Film for enzyme sensor
Electroanalysis, 2009Co-Authors: Zimple Matharu, Pratibha Pandey, Madhurima Pandey, Vinay Gupta, B D MalhotraAbstract:Mediator free enzyme sensor has been fabricated by covalently immobilizing cholesterol oxidase (ChOx) onto 11-mercaptoundecanoic acid functionalized gold nanoparticles (MUDA-AuNPs) – octadecylamine (ODA) hybrid Langmuir–Blodgett Film. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies reveal that MUDA-AuNP/ODA LB Film has good affinity for ChOx and provides favorable microenvironment for direct electron transfer between enzyme and electrode. Interference free estimation of cholesterol has been realized at 0.3 V with linear range from 25 to 500 mg/dL, detection limit of 23.38 mg/dL, sensitivity of 1.085 μA mM−1 and response time of 20 s at pH 7.0.
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Langmuir Blodgett Film based on meh ppv for cholesterol biosensor
Analytica Chimica Acta, 2009Co-Authors: Zimple Matharu, Vinay Gupta, Sunil K Arya, S P Singh, B D MalhotraAbstract:Cholesterol oxidase (ChOx) has been immobilized onto conducting poly[2-methoxy,5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/stearic acid (SA) Langmuir–Blodgett Film transferred onto octadecanethiol (ODT) modified gold plate. The ChOx/MEH-PPV/SA LB Film bioelectrode exhibits has been characterized by FT-IR, contact angle, and atomic force microscopy. The response of the ChOx/MEH-PPV/SA LB Film bioelectrode carried out using differential pulse voltammetry (DPV) studies reveal linearity from 1.29 to 12.91 mM of cholesterol concentration and response time as 30 s. This ChOx/MEH-PPV/SA bioelectrode exhibits values of correlation coefficient as 0.9939, standard deviation as 0.0029 μA and limit of detection as 1.66 mM. UV–visible spectrophotometer studies reveal that 5.2 × 10−3 U of ChOx are actively working per cm2 area of ChOx/MEH-PPV/SA LB Film bioelectrode and this bioelectrode is thermally stable upto 55 °C with reusability of about 60 times.
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polyaniline Langmuir Blodgett Film based cholesterol biosensor
Langmuir, 2007Co-Authors: Zimple Matharu, Vinay Gupta, Sunil K Arya, S P Singh, Gajjala Sumana, B D MalhotraAbstract:Cholesterol oxidase (ChOx) has been covalently linked to Langmuir−Blodgett (LB) monolayers of polyaniline (PANI)-stearic acid (SA) prepared onto indium−tin-oxide (ITO) coated glass plates via glutaraldehyde (Glu) chemistry. These ChOx/Glu/PANI-SA LB Film/ITO electrodes have been characterized by FT-IR, cyclic voltammetry, and scanning electron microscopy, respectively. The results of response measurements carried out on these bioelectrodes using linear sweep voltammetry (LSV) reveal linearity from 25 to 400 mg/dL of cholesterol concentration with sensitivity of 88.9 nA mg-1 dL. The linear regression analysis of bioelectrode reveals standard deviation and correlation coefficient of 0.737 μA and 0.9988, respectively. The low value of the Michaelis−Menten constant of these bioelectrodes obtained as 1.21 mM for the immobilized enzyme indicates increased interaction between ChOx and cholesterol in the PANI-SA LB Film.
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Langmuir Blodgett Film based biosensor for estimation of galactose in milk
Electrochimica Acta, 2004Co-Authors: Sandeep K Sharma, B D Malhotra, Rahul Singhal, Neeta Sehgal, Ashok KumarAbstract:Abstract A mono-enzyme amperometric biosensor has been developed for the estimation of galactose in milk and milk products. Galactose oxidase was immobilized with poly(3-hexyl thiophene)/stearic acid (P3HT/SA) on to indium tin-oxide (ITO) coated glass plates using Langmuir–Blodgett (LB) Film deposition technique. The immobilized galactose oxidase in P3HT/SA LB Films was characterized using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy. This P3HT/SA/GaO LB Film on ITO-coated glass plate was used as working electrode with platinum as reference electrode for development of galactose biosensor. The biosensor shows the linearity 1–4 g/dl galactose. The effect of galactose concentration, pH, temperature, detection limit, response time and stability of the immobilized galactose oxidase in LB Films were also studied. The electrode was found stable upto 45 °C and has a shelf life of more than 90 days.
