The Experts below are selected from a list of 42432 Experts worldwide ranked by ideXlab platform
Todd Emrick - One of the best experts on this subject based on the ideXlab platform.
-
Quantum dots tailored with poly(para-phenylene vinylene).
Journal of the American Chemical Society, 2004Co-Authors: Habib Skaff, Kevin Sill, Todd EmrickAbstract:In Polymer−nanoparticle composites, uniform dispersion of the nanoparticles carries advantages over cases where nanoparticle aggregation dominates. Such dispersion has been particularly difficult to obtain in the case of composites prepared from nanoparticles and conjugated Polymers. Here, we show that cadmium selenide nanocrystals, or quantum dots, can be integrated into thin films of poly(para-phenylene vinylene) (PPV) without aggregation. The two key departures from previous studies of quantum-dot/Electronic Polymer composites are (1) the synthesis of high-quality quantum dots directly in novel, functional ligands, thus eliminating the need for ligand exchange, and (2) Polymerization chemistry that grafts PPV to the quantum dot surface. Solid-state photoluminescence spectra of composite materials prepared by these novel techniques reveal the critical importance of the quantum dot−Polymer interface that will enable new investigations in nanoparticle-based light-emitting devices.
Shashi Paul - One of the best experts on this subject based on the ideXlab platform.
-
Small Organic Molecules for Electrically Re-writable Non-volatile Polymer Memory Devices
MRS Online Proceedings Library, 2010Co-Authors: Iulia Salaoru, Shashi PaulAbstract:The usage of organic materials in the manufacture of Electronic Polymer memory devices is on the rise. Polymer memory devices are fabricated by depositing a blend (an admixture of organic Polymer, small molecules and nanoparticles) between two metal electrodes. The primary aim is to produce devices that exhibit two distinct electrical conductance states when a voltage is applied. These two states can be viewed as the realisation of non-volatile memory. This is an interesting development; however, there are a number of theories that have been proposed to explain the observed electrical behaviour. We have proposed a model that is based on electric dipole formation in the Polymer matrix. Here, we investigate further the proposed model by deliberately creating electric dipoles in a Polymer matrix using electron donors (8-Hydroxyquinoline, Tetrathiafulvalene and Bis(ethylenedithio)tetrathiafulvalene) and electron acceptors (7,7,8,8-Tetracyanoquinodimethane, Tetracyanoethylene and Fullerene) small molecules. Two types of structures were investigated (i) a metal/blend of Polymer and small molecules/metal (MOM ) , device and (ii) a metal/insulator/blend of small molecules and Polymer/semiconductor (MIS) architecture. A blend of Polymer and small organic molecules was prepared in methanol and spin-coated onto a glass substrate marked with thin aluminium (Al) tracks; a top Al contact was then evaporated onto the blend after drying - this resulted in a metal-organic-metal structure. The MIS structures consisted of an ohmic bottom Al contact, p-type Si, a Polymer blend (two small organic molecules and insulating Polymer), followed by polyvinyl acetate and finally a top, circular Al electrode. In-depth FTIR studies were carried out to understand the observed electrical behaviour. An electrical analysis of these structures was performed using an HP4140B picoammeter and an HP 4192A impedance analyser at a frequency of 1 MHz.
-
First contact-charging of gold nanoparticles by electrostatic force microscopy
Applied Physics Letters, 2010Co-Authors: Shashi PaulAbstract:The use of nanoparticle materials in the manufacture of Electronic Polymer memory devices is on the rise. Organic memory devices are fabricated by depositing a blend of organic Polymer, small organic molecules, and nanoparticles between two metal electrodes. The primary aim is to produce devices that exhibit two distinct electrical conductance states when control voltages are applied. By retaining the states when power is removed can be viewed as the realization of nonvolatile memory. In this letter, an attempt is made to further understand the conundrums that scholars in this field are currently facing, with questions about the nanoparticle charging mechanism being investigated.
-
Electronic Polymer memory devices—Easy to fabricate, difficult to understand
Thin Solid Films, 2010Co-Authors: Shashi Paul, Iulia SalaoruAbstract:Abstract There has been a number reports on Polymer memory devices for the last one decade. Polymer memory devices are fabricated by depositing a blend (an admixture of organic Polymer, small organic molecules and nanoparticles) between two metal electrodes. These devices show two electrical conductance states (“1” and “0”) when voltage is applied, thus rendering the structures suitable for data retention. These two states can be viewed as the realisation of memory devices. However, Polymer memory devices reported so far suffer from multiple drawbacks that render their industrial implementation premature. There is a large discrepancy in the results reported by different groups. This article attempts to answer some of the questions.
Alan G. Macdiarmid - One of the best experts on this subject based on the ideXlab platform.
-
Line patterning of graphite and the fabrication of cheap, inexpensive, “throw-away” sensors
Sensors and Actuators B: Chemical, 2008Co-Authors: Everaldo C. Venancio, Luiz H. C. Mattoso, Paulo Sérgio De Paula Herrmann Junior, Alan G. MacdiarmidAbstract:Abstract A new simple method (“line patterning technique”) using only standard office equipment is described whereby clearly defined, electrically conducting patterns of graphite can be deposited on Polymer (plastic) or paper substrates. The properties of the conductive patterns have been characterized by electrical conductivity and SEM measurements. Sensors were constructed by using interdigitated patterns of graphite deposited on plastic and paper, and coated with a thin film of conducting Electronic Polymer, e.g. polyaniline emeraldine salt.
-
Controllable Synthesis of Nanostructures of Polymers of Aniline
2006Co-Authors: Everaldo C. Venancio, Pen C. Wang, Alan G. MacdiarmidAbstract:An organic Polymer that possesses the electrical, Electronic, magnetic and optical properties of a metal while retaining the mechanical properties, processibility, etc. commonly associated with a conventional Polymer, is termed an “intrinsically conducting Polymer” (ICP) more commonly known as a “synthetic metal”. Its properties are intrinsic to a “doped” form of the Polymer. This class of Polymer – an Electronic Polymer – is completely different from “conducting Polymers” which are merely a physical mixture of a nonconductive Polymer with a conducting material such as a metal or carbon powder distributed throughout the material. We have demonstrated for the first time that nanofibers of Polymers of aniline, polyaniline in the emeraldine oxidation state, can be obtained without the need of adding an external template (soft or hard) to the Polymerization system or the use of interfacial Polymerization. A basic purpose of this research is to blend the now well-established field of Electronic conducting Polymers with the new, emerging field of nanoscience to produce the hybrid field of “nanoElectronics” involving novel nano/micro structures of Electronic Polymers which are significantly smaller than the diameter of a human hair (~50,000 nm).
-
Fiber optic chemical sensors using a modified conducting Polymer cladding
Advanced Environmental and Chemical Sensing Technology, 2001Co-Authors: Jianming Yuan, Alan G. Macdiarmid, Mahmoud A. El-sherif, Wayne E. JonesAbstract:A new class ofsensors has been designed and prepared based on replacing the original cladding material on a small section of an optical fiber with a conducting Polymer or other environmentally sensitive material. Vapor induced chemical interactions with the Polymer result in refractive index and optical absorption changes in the Polymer cladding. These changes lead to an optical intensity modulation induced within the multi-mode optical fiber. Polyaniline and polypyrrole were used as the modified cladding material on the fiber core. An in-situ deposition method was used to produce uniform thin film coatings of the Electronic Polymer on the optical fiber. It was found that optimization ofthe sensor sensitivity can be achieved by selecting the proper incident wavelength, excitation conditions, and optical detection technique. Chemical sensors were developed and tested for detection ofHCl and NH3 vapors along with the reducing agent hydrazine. The results clearly demonstrate that conjugated Polymer coated fiber optics represent a promising new approach for the detection of volatile toxic gasses.
Rajender S. Varma - One of the best experts on this subject based on the ideXlab platform.
-
Green approach to bulk and template-free synthesis of thermally stable reduced polyaniline nanofibers for capacitor applications
Green Chemistry, 2007Co-Authors: Mallikarjuna N. Nadagouda, Rajender S. VarmaAbstract:An extremely simple green approach is described that generates bulk quantities of nanofibers of the Electronic Polymer polyaniline in fully reduced state (leucoemeraldine form) in one step without using any reducing agent, surfactants, and/or large amounts of insoluble templates. Chemical oxidative Polymerization of aniline with acetic acid instead of HCl (conventional synthesis) dramatically changes the morphology of the resulting doped polyaniline powder from nonfibrillar (particulate) to almost exclusively nanofibers of the reduced leucoemeraldine state in the diameter range 20 nm to 50 nm depending on the acetic acid concentration. These reduced leucoemeraldine polyaniline nanofibers undergo a spontaneous redox reaction with noble metal ions under mild aqueous conditions, resulting in deposition of various shapes, such as leaf, particulate, nanowires and cauliflower for Ag, Pd, Au, and Pt, respectively, on the surface of polyaniline nanofibers, affording a facile entry into this technologically important class of metal–Polymer nanocomposites. These nanofibers also can act as seed templates to synthesize polyaniline nanofibers by conventional HCl doped synthesis where particulate morphology normally dominates. The ensuing polyaniline nanofibers have a broad final decomposition temperature which is at least 120 °C higher and have a very high dielectric constant ≈3500 at higher frequency when compared to reported reduced polyaniline and HCl based polyaniline.
Sanjeev K Manohar - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of polyaniline nanofibers by nanofiber seeding
Journal of the American Chemical Society, 2004Co-Authors: Xinyu Zhang, Warren J Goux, Sanjeev K ManoharAbstract:Seeding a conventional chemical oxidative Polymerization of aniline with even very small amounts of biological, inorganic, or organic nanofibers (usually <1%) dramatically changes the morphology of the resulting doped Electronic Polymer polyaniline from nonfibrillar (particulate) to almost exclusively nanofibers. The nanoscale morphology of the original seed template is transcribed almost quantitatively to the bulk precipitate. These findings could have immediate impact in the design and development of high-surface area Electronic materials.