The replacement of antibodies by molecularly imprinted polymers (MIPs) has been investigated for many decades. However, indirect protocols (including natural primary and secondary antibodies) are still utilized to evaluate the ability of MIP thin films to recognize target molecules. MIPs can be prepared as either a thin film or as particles, and cavities that are complementary to the template can be generated on their surfaces. We have prepared thin film MIPs and particle MIPs prepared by solvent evaporation and phase inversion, respectively, from solutions of poly(ethylene-co-vinyl alcohol) (pEVAL) in the presence of the target analytes amylase, lysozyme, and lipase. These were first adsorbed on MIP thin films and by MIP particles that contain fluorescent quantum dots. Sandwich fluoroimmunoassays were then conducted to quantify them in MIP-coated 96-well microplates. The method was applied to determine amylase in saliva, and results were compared with a commercial analytical system.
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The recognition of amylase-imprinted poly(ethylene-co-vinyl alcohol)/quantum dots composite nanoparticles to amylase on the amylase-imprinted poly(ethylene-co-vinyl alcohol) coated 96-well microplates. 相似文献
In this study, we developed a liquid crystal (LC)-based detection method for polymer films synthesized on solid surfaces. A dark to bright transition in the optical appearance of nematic 4-cyano-4′-pentylbiphenyl (5CB) was observed after transferring a poly(methyl methacrylate) (PMMA) film onto a glass substrate functionalized with n-octyltrichlorosilane (OTS). This phenomenon indicates an orientational transition of 5CB from a homeotropic to a planar-random state. The optical response of 5CB was then evaluated directly through polymerization reactions on the OTS-functionalized glass substrate. Polymer films of PMMA, poly(glycidyl methacrylate) (PGMA), and poly(dimethylsiloxane) (PDMS) were synthesized on OTS surfaces covered with their reaction mixtures. All polymer films displayed bright signals of 5CB, which corresponded to the planar-random orientation of LCs. However, no change in orientation was observed for the control experiments. We confirmed the formation of polymer films on the OTS surface using atomic force microscopy. Overall, our results suggest that LCs can be used to construct optical monitoring systems for the product of polymerization reactions.
A nanocomposite film is described that is composed of alternating layers of poly(diallydimethyl ammonium chloride) and gold nanoparticles that interact through electrostatic forces. The films of varying thickness were prepared by the layer-by-layer technique, and Au-NPs were generated by electrochemical reduction of hexachloroauric acid. The composite films were characterized by UV?Cvis spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. Most nanocomposite films exhibit linear, uniform, and regular layer-by-layer growth during the process of formation. The films exhibit unique performance in terms of surface enhanced Raman scattering and electrocatalytic activitiy towards the oxidation of ascorbic acid.
Figure
A nanocomposite film was prepared by alternating layers of poly(diallydimethyl ammonium chloride) and gold nanoparticles, in which Au-NPs were generated by electrochemical reduction of hexachloroauric acid. The films exhibit unique performance in terms of surface enhanced Raman scattering and electrocatalytic activitiy towards the oxidation of ascorbic acid. 相似文献
A reagentless d-sorbitol biosensor based on NAD-dependent d-sorbitol dehydrogenase (DSDH) immobilized in a sol–gel carbon nanotubes–poly(methylene green) composite has been developed. It was prepared by durably immobilizing the NAD+ cofactor with DSDH in a sol–gel thin film on the surface of carbon nanotubes functionalized with poly(methylene green). This device enables selective determination of d-sorbitol at 0.2 V with a sensitivity of 8.7?μA?mmol?1?L?cm?2 and a detection limit of 0.11 mmol?L?1. Moreover, this biosensor has excellent operational stability upon continuous use in hydrodynamic conditions.
Figure
Reagentless D-sorbitol biosensor based on NAD-dependent D-sorbitol dehydrogenase (DSDH) immobilized in sol-gel/carbon nanotubes/poly(methylene green) composite 相似文献
We have investigated the oxidative electrochemistry of nitrite on glassy carbon electrodes modified with cobalt nanoparticles, poly(3,4-ethylenedioxythiophene) (PEDOT), and graphene. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The results suggest that this new type of electrode combines the advantages of PEDOT-graphene films and cobalt nanoparticles and exhibits excellent electrocatalytic activity towards the oxidation of nitrite. There is a linear relationship between the peak current and the nitrite concentration in the range from 0.5?μM to 240?μM, and the detection limit is 0.15?μM. The modified electrodes also enable the determination of nitrite at low potentials where the noise level and interferences by other electro-oxidizable compounds are weak.
Figure
The present work describes the design of a Co NPs-PEDOT-GE nanocomposite- modified GCE and its electrocatalytic properties toward the oxidation of nitrite. Compared with the Co NPs-GE/GCE (b) or PEDOT-GE/GCE (c), the as-prepared Co NPs-PEDOT-GE/GCE (d) exhibits remarkably enhanced electrocatalytic activity towards nitrite 相似文献
The present work has studied electrochemical and optical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film electrodes drop-casted from commercial PEDOT:PSS aqueous dispersion with preliminary addition and without addition of LiClO4 electrolyte (further denoted as PEDOT:PSS/LiClO4 and PEDOT:PSS). Cyclic voltammetry measurements showed the significant increase in capacitance of PEDOT:PSS/LiClO4 film electrodes in comparison to PEDOT:PSS. Furthermore, the improved charge transport in PEDOT:PSS/LiClO4 films was demonstrated by electrochemical impedance spectra. In situ spectroelectrochemical measurements revealed that preliminary addition of LiClO4 into PEDOT:PSS aqueous dispersion allows to increase amount of free charge carriers (polaron and bipolaron states) in the resulting film during electrochemical oxidation in LiClO4 propylene carbonate solution. This increase was attributed to ion-induced charge screening between positively charged PEDOT and negatively charged PSS in polyelectrolyte structure, which was supported by structural investigations of both types of film electrodes by using FTIR, SEM, and XPS measurements. Charge screening results from a more open structure that allows conformational relaxation of PEDOT molecules during charge transport, which leads to partial separation of oppositely charged PSS and PEDOT molecules and facilitating the increase of electrochemical activity.
We have studied the effect of treatment of multiwalled carbon nanotubes (MWCNTs) for use in DNA-based biosensors with oxygen plasma. Well-patterned MWCNT electrodes were photolithographically fabricated on glass substrates. Pure oxygen was used for etching and functionalization of the MWCNT film in a lab-made plasma chamber. The resulting electrodes exhibited a dramatic change in the morphology of their surface, the chemical composition, and the electrochemical properties in terms of peak current and peak potential separation. The electrodes also showed increased DNA immobilization efficiency and much higher sensitivity in the detection of target DNA as compared to non-treated MWCNT electrodes. Plasma treatment was optimized and electrodes were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and differential pulse voltammetry.
Figure
Well-patterned MWCNT electrodes were photolithographically fabricated on glass substrates. Pure oxygen was used for etching and functionalization of the MWCNT film. The electrodes showed increased DNA immobilization efficiency and much higher sensitivity in the detection of target DNA as compared to non-treated MWCNT electrodes 相似文献
Highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as transparent electrodes for organic light‐emitting diodes (OLEDs) are doped with a new solvent 1,3‐dimethyl‐2‐imidazolidinone (DMI) and are optimized using solvent post‐treatment. The DMI doped PEDOT:PSS films show significantly enhanced conductivities up to 812.1 S cm−1. The sheet resistance of the PEDOT:PSS films doped with DMI is further reduced by various solvent post‐treatment. The effect of solvent post‐treatment on DMI doped PEDOT:PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated PEDOT:PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped PEDOT:PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized PEDOT:PSS films with the new solvent of DMI can be a promising transparent electrode for low‐cost, efficient ITO‐free white OLEDs.
We report the successful synthesis of transparent thin film of conducting poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS) coated monodisperse polystyrene (PS) microspheres via a simple physical adsorption route in an aqueous media and their electrorheological (ER) application under an applied electric field. Due to the insulating PS core, the PEDOT/PSS wrapped PS (PEDOT/PSS/PS) particles possess a low volume conductivity appropriately applied as ER active materials. Tested by a rotational rheometer under an applied electric field, the PEDOT/PSS/PS based ER fluid dispersed in a silicone oil shows a typical Bingham‐fluid behavior with increased yield stresses according to the increase of electric field strength.
We report on the fabrication of an enzyme–free electrochemical sensor for glucose based on a printed film consisting of multi–walled carbon nanotubes (MWCNTs). The MWCNT–based film can be produced by means of a flexographic printing process on a polycarbonate (PC) substrate. The electrochemical response of the MWCNT–based film (referred to as MWCNT–PC) towards the oxidation of glucose at pH 7 was studied by means of cyclic voltammetry and electrochemical impedance spectroscopy. The MWCNT–PC film exhibits substantial electrocatalytic activity towards the oxidation of glucose at an anodic potential of 0.30?V (vs. Ag/AgCl). The findings reveal that the MWCNT–PC film enables non–enzymatic sensing of glucose with a detection limit as low as 2.16?μM and a sensitivity of 1045?μA?mM?1?cm?2.
Figure
Enzyme–free electrochemical sensor for glucose consisting of multi–walled carbon nanotubes was fabricated by means of flexographic printing process on polycarbonate substrate. The sensor exhibits electrocatalytic activity for glucose oxidation at an anodic potential of 0.30?V (vs. Ag/AgCl) with detection limit of 2.16?μM and sensitivity of 1045?μA?mM?1?cm?2. 相似文献
Electrochemistry can be used for fabrication and characterization of mesoporous oxide films. First, this review provides insight into the methods used to prepare templated mesoporous thin films on an electrode surface, i.e., evaporation-induced self-assembly (EISA) and electrochemically assisted self-assembly (EASA). Electrochemical characterization of mass transport processes in pure and organically functionalized mesoporous oxide films is then discussed. The electrochemical response can be basically restricted by the electron/mass transfer reaction at the electrode–film interface and diffusion through mesopore channels. The contributions of cyclic voltammetry, hydrodynamic voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy to the characterization of films with distinct mesostructures are finally described, with special emphasis on identification of conditions that can affect the electrochemical response recorded with such modified electrodes.
We report on a glassy carbon electrode that was modified with a composite made from graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) that enables highly sensitive determination of L-tyrosine. The sensor was characterized by transmission electron microscopy and electrochemical impedance spectroscopy, and its electrochemical properties by cyclic voltammetry, chronocoulometry and differential pulse voltammetry. The GO/MWCNT hybrid exhibits strong catalytic activity toward the oxidation of L-tyrosine, with a well defined oxidation peak at 761 mV. The respective current serves as the analytical information and is proportional to the L-tyrosine concentration in two ranges of different slope (0.05 to 1.0 μM and 1.0 to 650.0 μM), with limits of detection and quantification as low as 4.4 nM and 14.7 nM, respectively. The method was successfully applied to the analysis of L-tyrosine in human body fluids. The excellent reproducibility, stability, sensitivity and selectivity are believed to be due to the combination of the electrocatalytic properties of both GO and MWCNT. They are making this hybrid electrode a potentially useful electrochemical sensing platform for bioanalysis.
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A new L-tyrosine electrochemical sensor was fabricated based on graphene oxide and multiwalled carbon nanotube. The prepared sensor exhibits excellent electro-catalysis to the oxidation of L-tyrosine, and can improve determination sensitivity and decrease detection limit. This sensor was successfully applied to detect L-tyrosine in human fluids with satisfactory results. 相似文献
We report on the voltammetric determination of the flavonoid Baicalein by using a carbon paste electrode that was doped with multi-walled carbon nanotubes. The resulting sensor exhibits excellent redox activity towards Baicalein due to the large surface area and good conductivity of the electrode. Cyclic voltammetry at various scan rates was used to investigate the redox properties of Baicalein. At the optimum conditions, the sensor displays a linear current response to Baicalein in the 0.02–10 μM concentration range, with a limit of detection of 4.2 n M. The method was successfully applied to the determination of Baicalein in spiked human blood serum samples and in a Chinese oral liquid.
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We construct a new voltammetric sensor, based on multi-walled carbon nanotubes (MWCNT) doped Carbon paste electrode(CPE), The proposed electrode can improve the oxidation of Baicalein intensively, which can applied to the quantitative determination of Baicalein with wide linear response and low detection limit. 相似文献
We report on an investigation of the optical properties of gold nanoparticles assembled as thin films of different thickness. The nanoparticles were linked to the surface of a gold chip by dithiol reagents and studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy. There is good correlation between the experimental findings and theoretical simulation, and the respective data reveal the presence of ordered nanostructures in the assemblies. The shift in the SPR angle is linearly dependent on the particle size and the ratio of the different particles. SPR spectroscopy also reveals important information in terms of the optical constants of such films. This shall be further applied to in-situ quality control in the fabrication of optoelectronic, solar cell and semiconductor devices.
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SPR angle shifts according to the immobilization of gold nanoparticles with different size on BDMT SAM 相似文献
In this work, polyacrylamide/multi-walled carbon nanotubes (MWCNT) solution is electrospun to nanocomposite nanofibrous membranes for acetylcholinesterase enzyme immobilization. A new method for enzyme immobilization is proposed, and the results of analysis show successful covalent bonding of enzymes on electrospun membrane surface besides their non-covalent entrapment. Fourier transform infrared spectroscopy, mechanical and thermal investigations of nanofibrous membrane approve successful cross-linking and enzyme immobilization. The enzyme relative activity and kinetic on both pure and nanocomposite membranes is investigated, and the results show proper performance of designed membrane to even improve the enzyme activity followed by immobilization compared to free enzyme. Scanning electron microscopy images show nanofibrous web of 3D structure with a low shrinkage and hydrogel structure followed by enzyme immobilization and cross-linking. Moreover, the important role of functionalized carbon nanotubes on final nanofibrous membrane functionality as a media for enzyme immobilization is investigated. The results show that MWCNT could act effectively for enzyme immobilization improvement via both physical (enhanced fibers’ morphology and conductivity) and chemical (enzyme entrapment) methods.
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Mechanism for APTS surface modification of nanofibrous nanoweb for enzyme immobilization 相似文献
There is an actual need of advanced materials for the emerging field of bioelectronics. One commonly used material is the conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) due to its general use in organic electronics. However, depending on the application in bioelectronics, PEDOT:PSS is not fully biocompatible due to the high acidity of the residual sulfonate protons of PSS. In this paper, the synthesis and biocompatibility properties of new poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) aqueous dispersions and its resulting films are shown. Thus, negatively charged GAGs as an alternative to PSS are presented. Three different commercially available GAGs, hyaluronic acid, heparin, and chondroitin sulfate are used. Indeed, PEDOT:GAGs dispersions are prepared through an oxidative chemical polymerization in water. Biocompatibility assays of the PEDOT:GAGs coatings are performed using SH‐SY5Y and CCF‐STTG1 cell lines and with ATP and Ca2+. Results show full biocompatibility and a pronounced anti‐inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.