370 results on '"hybrid nanomaterials"'
Search Results
352. Grape-Like Fe3O4 Agglomerates Grown on Graphene Nanosheets for Ultrafast and Stable Lithium Storage.
- Author
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Qi L, Xin Y, Zuo Z, Yang C, Wu K, Wu B, and Zhou H
- Abstract
An in situ simple and effective synthesis method is effectively exploited to construct MOF-derived grape-like architecture anchoring on nitrogen-doped graphene, in which ultrafine Fe3O4 nanoparticles are uniformly dispersed (Fe3O4@C/NG). In this hybrid hierarchical structure, new synergistic features are accessed. The graphene oxide plane with functional groups is expected to alleviate the aggregation problem in the MOFs' growth. Moreover, the morphology and size of iron-based MOFs and carbon content are conveniently controlled by controlling the solution concentration of precursor. Through making use of in situ carbonization of the organic ligands in MOFs, Fe3O4 subunits are effectively protected by 3D interconnected conductive carbon at microscale. Consequently, when applied as anode materials, even as high as 10 A g(-1) after 1000 cycles, Fe3O4@C/NG still maintains as high as 458 mA h g(-1).
- Published
- 2016
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353. Structural Phase Transition Effect on Resistive Switching Behavior of MoS2 -Polyvinylpyrrolidone Nanocomposites Films for Flexible Memory Devices.
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Zhang P, Gao C, Xu B, Qi L, Jiang C, Gao M, and Xue D
- Abstract
The 2H phase and 1T phase coexisting in the same molybdenum disulfide (MoS2 ) nanosheets can influence the electronic properties of the materials. The 1T phase of MoS2 is introduced into the 2H-MoS2 nanosheets by two-step hydrothermal synthetic methods. Two types of nonvolatile memory effects, namely write-once read-many times memory and rewritable memory effect, are observed in the flexible memory devices with the configuration of Al/1T@2H-MoS2 -polyvinylpyrrolidone (PVP)/indium tin oxide (ITO)/polyethylene terephthalate (PET) and Al/2H-MoS2 -PVP/ITO/PET, respectively. It is observed that structural phase transition in MoS2 nanosheets plays an important role on the resistive switching behaviors of the MoS2 -based device. It is hoped that our results can offer a general route for the preparation of various promising nanocomposites based on 2D nanosheets of layered transition metal dichalcogenides for fabricating the high performance and flexible nonvolatile memory devices through regulating the phase structure in the 2D nanosheets., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
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- 2016
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354. Core-shell nanostructured hybrid composites for volatile organic compound detection.
- Author
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Tung TT, Losic D, Park SJ, Feller JF, and Kim T
- Subjects
- Bridged Bicyclo Compounds, Heterocyclic chemistry, Ionic Liquids chemistry, Polymers chemistry, Magnetite Nanoparticles chemistry, Nanocomposites chemistry, Volatile Organic Compounds analysis
- Abstract
We report a high-performance chemiresistive sensor for detection of volatile organic compound (VOC) vapors based on core-shell hybridized nanostructures of Fe3O4 magnetic nanoparticles (MNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT)-conducting polymers. The MNPs were prepared using microwave-assisted synthesis in the presence of polymerized ionic liquids (PILs), which were used as a linker to couple the MNP and PEDOT. The resulting PEDOT-PIL-modified Fe3O4 hybrids were then explored as a sensing channel material for a chemiresistive sensor to detect VOC vapors. The PEDOT-PIL-modified Fe3O4 sensor exhibited a tunable response, with high sensitivity (down to a concentration of 1 ppm) and low noise level, to VOCs; these VOCs include acetone vapor, which is present in the exhaled breath of potential lung cancer patients. The present sensor, based on the hybrid nanostructured sensing materials, exhibited a 38.8% higher sensitivity and an 11% lower noise level than its PEDOT-PIL-only counterpart. This approach of embedding MNPs in conducting polymers could lead to the development of new electronic noses, which have significant potential for the use in the early diagnosis of lung cancer via the detection of VOC biomarkers.
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- 2015
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355. Ultrafast sonochemical synthesis of protein-inorganic nanoflowers.
- Author
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Batule BS, Park KS, Kim MI, and Park HG
- Subjects
- Biosensing Techniques methods, Colorimetry methods, Copper chemistry, Epinephrine analysis, Nanocomposites chemistry, Nanotechnology methods, Proteins chemistry, Sonication methods
- Abstract
We developed a simple but efficient method to synthesize protein-inorganic hybrid nanostructures with a flower-like shape (nanoflowers), which relies on sonication to facilitate the synthesis of the nanoflowers. With this technique, we synthesized nanoflowers containing laccase as a model protein and copper phosphate within 5 minutes at room temperature. The resulting laccase nanoflowers yielded greatly enhanced activity, stability, and reusability, and their usefulness was successfully demonstrated by applying them in the colorimetric detection of epinephrine. The strategy developed could be used to rapidly synthesize nanoflowers for various applications in biosensor and enzyme catalysis and would expand the utilization of nanoflowers in diverse fields of biotechnology.
- Published
- 2015
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356. 3D Hybrid Plasmonic Nanomaterials for Highly Efficient Optical Absorbers and Sensors.
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Park SG, Mun C, Lee M, Jeon TY, Shim HS, Lee YJ, Kwon JD, Kim CS, and Kim DH
- Abstract
3D hybrid plasmonic nanomaterials are composed of 3D-stacked Ag nanowires and nanoparticles separated by a nanoscale-thick alumina interlayer. The 3D hybrid plasmonic nanostructures exhibit strong plasmonic coupling between the ultrahigh populations of plasmonic nanomaterials, overcoming the physical limitation of inefficient plasmonic coupling of the Ag nanowire stacks., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
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- 2015
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357. One-Dimensional Dielectric/Metallic Hybrid Materials for Photonic Applications.
- Author
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Li YJ, Xiong X, Zou CL, Ren XF, and Zhao YS
- Abstract
Explorations of 1D nanostructures have led to great progress in the area of nanophotonics in the past decades. Based on either dielectric or metallic materials, a variety of 1D photonic devices have been developed, such as nanolasers, waveguides, optical switches, and routers. What's interesting is that these dielectric systems enjoy low propagation losses and usually possess active optical performance, but they have a diffraction-limited field confinement. Alternatively, metallic systems can guide light on deep subwavelength scales, but they suffer from high metallic absorption and can work as passive devices only. Thus, the idea to construct a hybrid system that combines the merits of both dielectric and metallic materials was proposed. To date, unprecedented optical properties have been achieved in various 1D hybrid systems, which manifest great potential for functional nanophotonic devices. Here, the focus is on recent advances in 1D dielectric/metallic hybrid systems, with a special emphasis on novel structure design, rational fabrication techniques, unique performance, as well as their wide application in photonic components. Gaining a better understanding of hybrid systems would benefit the design of nanophotonic components aimed at optical information processing., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2015
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358. Observation of Ground- and Excited-State Charge Transfer at the C60/Graphene Interface.
- Author
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Jnawali G, Rao Y, Beck JH, Petrone N, Kymissis I, Hone J, and Heinz TF
- Abstract
We examine charge transfer interactions in the hybrid system of a film of C60 molecules deposited on single-layer graphene using Raman spectroscopy and Terahertz (THz) time-domain spectroscopy. In the absence of photoexcitation, we find that the C60 molecules in the deposited film act as electron acceptors for graphene, yielding increased hole doping in the graphene layer. Hole doping of the graphene film by a uniform C60 film at a level of 5.6 × 10(12)/cm(2) or 0.04 holes per interfacial C60 molecule was determined by the use of both Raman and THz spectroscopy. We also investigate transient charge transfer occurring upon photoexcitation by femtosecond laser pulses with a photon energy of 3.1 eV. The C60/graphene hybrid exhibits a short-lived (ps) decrease in THz conductivity, followed by a long-lived increase in conductivity. The initial negative photoconductivity transient, which decays within 2 ps, reflects the intrinsic photoresponse of graphene. The longer-lived positive conductivity transient, with a lifetime on the order of 100 ps, is attributed to photoinduced hole doping of graphene by interfacial charge transfer. We discuss possible microscopic pathways for hot carrier processes in the hybrid system.
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- 2015
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359. Roll-to-Roll Nanomanufacturing of Hybrid Nanostructures for Energy Storage Device Design.
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Oakes L, Hanken T, Carter R, Yates W, and Pint CL
- Abstract
A key limitation to the practical incorporation of nanostructured materials into emerging applications is the challenge of achieving low-cost, high throughput, and highly replicable scalable nanomanufacturing techniques to produce functional materials. Here, we report a benchtop roll-to-roll technique that builds upon the use of binary solutions of nanomaterials and liquid electrophoretic assembly to rapidly construct hybrid materials for battery design applications. We demonstrate surfactant-free hybrid mixtures of carbon nanotubes, silicon nanoparticles, MoS2 nanosheets, carbon nanohorns, and graphene nanoplatelets. Roll-to-roll electrophoretic assembly from these solutions enables the controlled fabrication of homogeneous coatings of these nanostructures that maintain chemical and physical properties defined by the synergistic combination of nanomaterials utilized without adverse effects of surfactants or impurities that typically limit liquid nanomanufacturing routes. To demonstrate the utility of this nanomanufacturing approach, we employed roll-to-roll electrophoretic processing to fabricate both positive and negative electrodes for lithium ion batteries in less than 30 s. The optimized full-cell battery, containing active materials of prelithiated silicon nanoparticles and MoS2 nanosheets, was assessed to exhibit energy densities of 167 Wh/kgcell(-1) and power densities of 9.6 kW/kgcell(-1).
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- 2015
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360. Lipid Nanotube Arrays: Exploring Nanoscale Phenomena on Lipid-Substrate Interfaces.
- Author
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Alaouie, Ali Mustafa
- Subjects
- electron paramagnetic resonance, hybrid nanomaterials, phase transitions, self assembly, substrate supported bilayers, lipid nanotubes
- Abstract
Substrate-supported-phospholipids bilayers (SSPB) could be utilized to stabilize functional membrane proteins on solid surfaces while providing an ideal medium to mimic the many properties of biological membranes. Our approach to the fabrication of SSPB relies on the property of phospholipids to self-assemble inside Anodic Aluminum Oxide (AAO) nanoporous substrates into cylindrical structures, which we call 'lipid nanotubes'. In our design, the phospholipids are adequately protected from any surface perturbations or contamination and yet accessible to solute molecules. Furthermore, when compared with planar supported membrane designs, our substrate would have a larger surface area covered with lipids for an identical outside dimensions. This improvement would allow for accommodating more functional proteins. An additional advantage is that our porous biochip should be able to retain more water and for a longer time duration through capillary action. Since water is known to be essential for the phospholipids to maintain their bilayer assembly, our design will be more robust in handling and applications than the fragile planar surface assemblies. The purpose of this research was to investigate the presence and formation of ordered lipid nanotubes as well as studying the effects of nano-scale confinement on the structure and dynamics of self-assembled phospholipid membranes. These lipid nanotubes were found to behave very much similar to unsupported phospholipid bilayers. The existence of ordered lipid nanotube assemblies was confirmed by spin-labeling electron paramagnetic resonance (sl-EPR). Differential scanning calorimetry and spin-labeling experiments demonstrated that the main phase transition temperatures for AAO-confined and unsupported DMPC bilayers were essentially the same; however, the van't Hoff enthalpy was lower for AAO-confined bilayers. Additionally, it was observed that the main effect of nanopore confinement is in longer time constants associated with lipid rearrangement during the phase transition and/or motional restrictions but not in the thermodynamics as previously thought. This research also examined the inclusion of a model gramicidin A (gA) ion channel into lipid nanotube arrays and demonstrated using sl-EPR that ordered assemblies are present in addition to confirming that the active dimer form of gA was being formed.
- Published
- 2006
361. Polysilsesquioxane nanoparticles for triggered release of cisplatin and effective cancer chemoradiotherapy.
- Author
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Rocca JD, Werner ME, Kramer SA, Huxford-Phillips RC, Sukumar R, Cummings ND, Vivero-Escoto JL, Wang AZ, and Lin W
- Subjects
- Animals, Antineoplastic Agents chemistry, Cell Line, Tumor, Cisplatin chemistry, Delayed-Action Preparations, Disease Models, Animal, Dose-Response Relationship, Drug, HL-60 Cells, Humans, Hydrodynamics, Mice, Microscopy, Electron, Scanning, Nanomedicine, Nanoparticles chemistry, Polyethylene Glycols chemistry, Polymers chemistry, Temperature, Antineoplastic Agents administration & dosage, Carcinoma, Non-Small-Cell Lung therapy, Chemoradiotherapy methods, Cisplatin administration & dosage, Lung Neoplasms therapy, Organosilicon Compounds chemistry, Prodrugs chemistry
- Abstract
Chemoradiotherapy is a well-established treatment paradigm in oncology. There has been strong interest in identifying strategies to further improve its therapeutic index. An innovative strategy is to utilize nanoparticle (NP) chemotherapeutics in chemoradiation. Since the most commonly utilized chemotherapeutic with radiotherapy is cisplatin, the development of an NP cisplatin for chemoradiotherapy has the highest potential impact on this treatment. Here, we report the development of an NP comprised of polysilsesquioxane (PSQ) polymer crosslinked by a cisplatin prodrug (Cisplatin-PSQ) and its utilization in chemoradiotherapy using non-small cell lung cancer as a disease model. Cisplatin-PSQ NP has an exceptionally high loading of cisplatin. Cisplatin-PSQ NPs were evaluated in chemoradiotherapy in vitro and in vivo. They demonstrated significantly higher therapeutic efficacy when compared to cisplatin. These results suggest that the Cisplatin-PSQ NP holds potential for clinical translation in chemoradiotherapy., (Copyright © 2015 Elsevier Inc. All rights reserved.)
- Published
- 2015
- Full Text
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362. Preparation of MoS2-MoO3 hybrid nanomaterials for light-emitting diodes.
- Author
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Yin Z, Zhang X, Cai Y, Chen J, Wong JI, Tay YY, Chai J, Wu J, Zeng Z, Zheng B, Yang HY, and Zhang H
- Abstract
A facile strategy to prepare MoS2 -MoO3 hybrid nanomaterials is developed, based on the heat-assisted partial oxidation of lithium-exfoliated MoS2 nanosheets in air followed by thermal-annealing-driven crystallization. The obtained MoS2 -MoO3 hybrid nanomaterial exhibits p-type conductivity. As a proof-of-concept application, an n-type SiC/p-type MoS2 -MoO3 heterojunction is used as the active layer for light-emitting diodes. The origins of the electroluminescence from the device are theoretically investigated. This facile synthesis and application of hybrid nanomaterials opens up avenues to develop new advanced materials for various functional applications, such as in electrics, optoelectronics, clean energy, and information storage., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2014
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363. Quantum dot tailored to single wall carbon nanotubes: a multifunctional hybrid nanoconstruct for cellular imaging and targeted photothermal therapy.
- Author
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Nair LV, Nagaoka Y, Maekawa T, Sakthikumar D, and Jayasree RS
- Subjects
- Animals, Cell Death, Cell Line, Cell Line, Tumor, Cell Survival, Diagnostic Imaging, Female, Humans, Laser Therapy methods, MCF-7 Cells, Mice, Microscopy, Electron, Transmission, Nanotechnology, Quantum Dots chemistry, Nanotubes, Carbon ultrastructure, Phototherapy methods, Quantum Dots therapeutic use
- Abstract
Hybrid nanomaterial based on quantum dots and SWCNTs is used for cellular imaging and photothermal therapy. Furthermore, the ligand conjugated hybrid system (FaQd@CNT) enables selective targeting in cancer cells. The imaging capability of quantum dots and the therapeutic potential of SWCNT are available in a single system with cancer targeting property. Heat generated by the system is found to be high enough to destroy cancer cells., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2014
- Full Text
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364. Exciton Quenching Due to Copper Diffusion Limits the Photocatalytic Activity of CdS/Cu2S Nanorod Heterostructures.
- Author
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Jen-La Plante I, Teitelboim A, Pinkas I, Oron D, and Mokari T
- Abstract
The formation of donor/acceptor junctions in hybrid nanomaterials is predicted to enhance photocatalytic activity as compared to single-component semiconductor systems. Specifically, nanomaterials containing a junction of n-type cadmium sulfide (CdS) and p-type copper sulfide (Cu2S) formed via cation exchange have been proposed as potential photocatalysts for reactions such as water splitting. Herein, we study the elemental distribution of Cu within these nanostructures using analytical transmission electron microscopy techniques. The resulting effects of this elemental distribution on photocatalytic activity and charge dynamics were further studied using a model photoreduction reaction and transient absorption spectroscopy. We find that copper diffusion in the hybrid nanostructure quenches the exciton lifetime and results in low photocatalytic activity; however, this effect can be partially mitigated via selective extraction. These results provide a deeper understanding of the physical processes within these hybrid nanostructures and will lead to more rational design of photocatalyst materials.
- Published
- 2014
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365. Hybrid platinum nanobox/carbon nanotube composites for ultrasensitive gas sensing.
- Author
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Popa A, Li J, and Samia AC
- Subjects
- Gases chemistry, Nanotubes, Carbon chemistry, Platinum chemistry
- Published
- 2013
- Full Text
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366. Diamond-lipid hybrids enhance chemotherapeutic tolerance and mediate tumor regression.
- Author
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Moore LK, Chow EK, Osawa E, Bishop JM, and Ho D
- Subjects
- Animals, Antineoplastic Agents therapeutic use, Breast Neoplasms pathology, Cell Line, Tumor, ErbB Receptors metabolism, Female, Humans, Mice, Xenograft Model Antitumor Assays, Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology, Breast Neoplasms drug therapy, Drug Tolerance, Lipids chemistry, Nanodiamonds chemistry
- Abstract
Self-assembled nanodiamond-lipid hybrid particles (NDLPs) harness the potent interaction between the nanodiamond (ND)-surface and small molecules, while providing a mechanism for cell-targeted imaging and therapy of triple negative breast cancers. Epidermal growth factor receptor-targeted NDLPs are highly biocompatible particles that provide cell-specific imaging, promote tumor retention of ND-complexes, prevent epirubicin toxicities and mediate regression of triple negative breast cancers., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2013
- Full Text
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367. Hybrid metal-carbon nanostructures for energy-related applications
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Herreros Lucas, C. and Herreros Lucas, C.
- Abstract
Recent technological advances such as the transition from non-renewable to renewable energy have been intimately related to the development of new nanostructured materials. A rational thinking is required for the development of nanomaterials with functional properties by targeting the combination of two or more nanocomponents with different properties, and preparation methodologies ensuring the utilisation of cheaper and abundant materials such as non-precious metals. Therefore, the main motivation of this work is to expand the frontiers of knowledge for the preparation of functional nanomaterials by designing hybrid carbon nanostructures suitable for energy storage applications containing a range of electrochemically active nanocomponents including molecules, nanoparticles and metal coordination polymers. The first chapter describes a general overview of the current approaches within the energy area to prepare uncoupled carbon nanostructures as well as the strategies to combine them with several active components (i.e. molecular metal clusters, nanoparticles and metal coordination polymers). Relevant concepts for this thesis such as electrochemical storage mechanisms, differences between hybrid and composite nanomaterials, synergetic effects and the distinction between ex situ and in situ synthetic approaches are discussed in the introductory chapter. For the sake of clarity, only the most relevant examples of hybrid carbon nanostructures from the literature will be highlighted and discussed. Before describing the hybridisation of carbon with molecules, nanoparticles and metal-coordination polymers, different carbon nanostructures will be analysed on their own due to their outstanding electrochemical properties. After the introductory chapter (Chapter 1), the thesis is followed by two parts: Part A and B. Part A, which is divided in two chapters (Chapter 2 and 3), gathers only carbon nanostructure investigations. In Chapter 2, a facile and solvent-free method is pr
368. Modulation de l’interaction électrostatique entre nanomatériaux en solutions et aux interfaces : Vers la génération de surfaces fonctionnelles hybrides
- Author
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SEKAR, Sribharani, Jean-Paul Chapel, Élodie Bourgeat-Lami [Rapporteur], Serge Stoll [Rapporteur], Jean-François Berret, Ling Qi, Sébastien Lecommandoux, Philippe Richetti, STAR, ABES, Chapel, Jean-Paul, Berret, Jean-François, Qi, Ling, Lecommandoux, Sébastien, Richetti, Philippe, Bourgeat-Lami, Élodie, and Stoll, Serge
- Subjects
Couche par couche ,Transition de dessalage ,[CHIM.OTHE] Chemical Sciences/Other ,Hybrid nanomaterials ,Electrostatic complexation ,Complexation électrostatique ,Nanomatériaux hybrides ,Layer-by- Layer (LbL) ,Functional surfaces ,Desalting transition ,Surface fonctionnelle - Abstract
In this manuscript, one-step bottom-up fabrication of “smart organic-inorganic hybridfunctional layers” at a liquid/solid interface were fabricated via a novel surfacefunctionalization pathway termed as “Surface Grown Hybrid Functional Layers” or SgLthrough fine tuning of electrostatic interaction between “highly stable” and oppositelycharged nanomaterials as a function of ionic strength of the dispersion. Cationic and anionicnanomaterials based on different hybrid nanoparticles/nanotubes that are very stable towardshigh saline environment have been formulated. The electrostatic complexation between theseoppositely charged nanomaterials has been studied in bulk and at an interface through theconcept of “desalting transition” pathway. In a second step, the growth of functional hybridlayers directly from a substrate via the novel SgL approach was then compared with theconventional Layer-by-Layer approach (LbL). Finally the preliminary experiments haveshown the potential applications of generated functional surfaces., Des couches fonctionnelles hybrides organiques/inorganiques ont été générées à une interface solide/liquide à l’aide d’une nouvelle technique de fabrication ascendante (bottomup) dénommée Croissance de Couche à partir d’une Surface (Surface Grown Layers - SgL)grâce à une modulation très fine de l’interaction électrostatique entre nano-objets decharges opposés en fonction de la force ionique de la dispersion aqueuse. Différents nanoparticules/tubes à la fois cationiques et anioniques et très stables vis-à-vis d’un environnement fortement salin ont été développés. La complexation électrostatique entre ces nanomatériaux a été étudiée en solution et près d’une interface au travers du concept de “transition de dessalage”. Dans un deuxième temps la croissance de couches hybrides à partird’un substrat a été étudiée en comparant l’approche SgL et la méthode classique d’adsorption séquentielle couche par couche (Layer by layer - LbL). Des expériences préliminaires ont montré le potentiel de cette approche dans le développement de substrats fonctionnels.
369. Study of the structural, morphological and electrochemical properties of thin films of hybrid nanocomposites made of layered double hydroxide (LDH) / biomolecules : application to the design of polyphenols biosensors
- Author
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SOUSSOU, Asma, Christine Grauby-Heywang, Adel Kalboussi, Touria Cohen-Bouhacina [Président], Nicole Jaffrezic-Renault [Rapporteur], Adnane Abdelghani [Rapporteur], Zouhair M. Baccar, Laboratoire Ondes et Matière d'Aquitaine (LOMA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux, Grauby-Heywang, Christine, Kalboussi, Adel, Cohen-Bouhacina, Touria, Abdelghani, Adnane, Jaffrezic-Renault, Nicole, and Baccar, Zouhair M.
- Subjects
[SPI.OTHER]Engineering Sciences [physics]/Other ,Nanocomposites hybrides ,Hybrid nanomaterials ,Layered double hydroxide (LDH) ,Spin coating ,Polyphénols ,Host matrix ,Surface fonctionalization ,Microscopie à force atomique (AFM) ,Matrice hôte ,Microbiocapteurs ,Fonctionnalisation de surface ,Polyphenols micro-biosensor ,Atomic force microscopy (AFM) ,Nanofilms ,Tyrosinase ,Hydroxyde double lamellaire (HDL) - Abstract
Polyphenols are in abundance in diet, being present in various fruits or vegetables, but also in tea or wine. Their antioxidant properties attracted an increasing interest of different researchers in the field of medicine and food manufacturers. Consequently, very intensive studies have been conducted to develop efficient polyphenols biosensors, while respecting certain criteria (simplicity of use, speed of measurement, low cost). In the case of enzymatic biosensors, the decisive step is the immobilization of the enzyme on the transducer surface without affecting its performances.In this thesis, we used layered double hydroxides (LDHs) as a host matrix to immobilize tyrosinase, an enzyme recognizing specifically polyphenols, at the surface of screen printed gold electrodes. Polyphenols used to study the biosensors were extracted from green tea.LDHs nanosheets were prepared by the co-precipitation method. In a first step, their structural properties were characterized by X-ray powder diffraction, Raman and Infra-Red spectroscopies, confirming crystalline phase and chemical composition of LDHs. In a second step, LDHs-thin films were prepared by self-assembly and spin coating deposition under various experimental conditions (nature and concentration of LDHs …), and studied by Atomic Force Microscopy (AFM) to obtain information about the surface morphology of the host matrix before enzyme immobilization. The presence of tyrosinase after the immobilization step was also confirmed by AFM. Electrochemical characteristics of the amperometric biosensors, whose design is based on this study, were determined by cyclic voltammetry and chronoamperometry. This study showed that these systems are highly sensitive to polyphenols, detecting them by their oxidation but also by the reduction of compounds enzymatically generated. They exhibit also other very attractive characteristics for the detection of complex mixture of polyphenols: a large dynamic range (up to 1000 ng.mL-1)and a very low detection limit (few pg.mL-1).; Les polyphénols sont des bioproduits générés par le métabolisme des végétaux. Récemment, ils ont attiré l’attention par leur impact potentiellement positif sur la santé, en grande partie lié à leur capacité antioxydante. Ils interviennent également dans les arômes de vin, café, thé… et intéressent donc l’industrie agroalimentaire. Le développement de biocapteurs adaptés à ces molécules est donc nécessaire, tout en respectant certains critères (simplicité d’utilisation, rapidité de la mesure, faible coût). Dans le cas des biocapteurs enzymatiques, l’étape déterminante est l'immobilisation de l’enzyme sur la surface du transducteur sans affecter ses performances.Dans cette thèse nous avons utilisé des matériaux de type « hydroxyde double lamellaires » (HDLs) comme matrice d’immobilisation de la tyrosinase, enzyme reconnaissant spécifiquement les polyphénols, afin de fonctionnaliser la surface d’électrodes d’or sérigraphiées. L’objectif était d’élaborer des microbiocapteurs pour détecter les polyphénols extraits du thé vert.Les HDLs ont été synthétisés par la méthode de coprécipitation directe, puis caractérisés par différentes méthodes physiques (spectroscopies Raman et infrarouge, diffraction des RX) afin de confirmer leur composition et de définir leur structure cristalline. Puis, des films minces bidimensionnels de HDL de différentes compositions ont été réalisés en faisant varier différents paramètres comme la nature du substrat, la concentration de la solution initiale de HDL et la méthode de dépôt (auto-assemblage « SAM » ou spin coating). L’étude morphologique de ces films a été réalisée par microscopie de force atomique (AFM) afin d’optimiser l’état de surface avant l’immobilisation de la tyrosinase. Le greffage de cette dernière a également été étudié par AFM. Enfin, une étude électrochimique (par voltammétrie cyclique et chronoampérométrie) nous a permis de déterminer les caractéristiques analytiques des microbiocapteurs ampérométriques ainsi élaborés. Les résultats ont montré que nos systèmes présentent une grande sensibilité aux polyphénols et sont capables de détecter ces molécules grâce à leur oxydation et aussi à la réduction des composés enzymatiquement générés par la réaction catalytique. Ils sont dynamiques dans une large gamme linéaire de détection (jusqu'à 1000 ng.mL-1) et peuvent également détecter des traces de polyphénols (de m’ordre de quelques pg.mL-1).
370. Microwave-mediated preparation of bio-inorganic hybrid materials for cosmetic and pharmaceutical applications
- Author
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CARLA VILLA, Priarone, G., Rosa, R., and Leonelli, C.
- Subjects
Organoldhs ,Green chemistry ,Carboxyilic acids ,Hybrid nanomaterials ,Microwave-mediated intercalation ,Solvent free
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