Graphene based materials: Past, present and future

Graphene has emerged as a subject of enormous scientific interest due to its exceptional electron transport, mechanical properties, and high surface area. When incorporated appropriately, these atomically thin carbon sheets can significantly improve physical properties of host polymers at extremely small loading. We first review production routes to exfoliated graphite with an emphasis on top-down strategies starting from graphite oxide, including advantages and disadvantages of each method. Then solvent- and melt-based strategies to disperse chemically or thermally reduced graphene oxide in polymers are discussed. Analytical techniques for characterizing particle dimensions, surface characteristics, and dispersion in matrix polymers are also introduced. We summarize electrical, thermal, mechanical, and gas barrier properties of the graphene/polymer nanocomposites. We conclude this review listing current challenges associated with processing and scalability of graphene composites and future perspectives f...

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Graphene/Polymer Nanocomposites

https://cyberleninka.org/article/n/1018032.pdf

Polymer nanotechnology: Nanocomposites

In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Recently developed strategies for isolating single-layer carbon sheets from graphite have enabled production of electrically conductive, mechanically robust polymer nanocomposites with enhanced gas barrier performance at extremely low loading. In this article, we present processing, morphology, and properties of thermoplastic polyurethane (TPU) reinforced with exfoliated graphite. For the first time, we compare carbon sheets exfoliated from graphite oxide (GO) via two different processes: chemical modification (isocyanate treated GO, iGO) and thermal exfoliation (thermally reduced GO, TRG), and three different methods of dispersion: solvent blending, in situ polymerization, and melt compounding. Incorporation of as low as 0.5 wt % of TRG produced electrically conductive TPU. Up to a 10-fold increase in tensile stiffness and 90% decrease in nitrogen permeation of TPU were observed with only 3 wt % iGO, implying a high aspect ratio of exfoliated platelets. Real- and reciprocal-space morphological characteri...

Graphene/Polyurethane Nanocomposites for Improved Gas Barrier and Electrical Conductivity

Polydisperse flakes in barrier films

Barrier membranes with different sizes of aligned flakes

In this paper, we report on the design and characterization of a new hydrogel-based implantable wireless glucose sensor The basic device structure is a passive [inductor/capacitor (LC)] micromachined resonator coupled to a stimuli-sensitive hydrogel, which is confined between a stiff nanoporous membrane and a thin glass diaphragm As glucose molecules pass through the nanoporous membrane, the hydrogel swells and deflects the flexible glass diaphragm, which is the movable plate of the variable capacitor in the totally integrated passive LC resonator The corresponding change in resonant frequency can be remotely detected A glucose- sensitive phenylboronic acid-based hydrogel was loaded into the microtransponder, and its sensitivity and time response were measured Prior to hydrogel loading, the sensitivity of the pressure sensor to applied air pressure was measured to be −222 kHz/kPa over the frequency range 51 → 42 MHz The sensor showed a sensitivity of −343 kHz/mM over the glucose concentration range

A hydrogel-based implantable micromachined transponder for wireless glucose measurement.

Immobile reactive groups within films used as packaging materials can retard transport of solutes like oqgen and water uapor. A theoy developed for these films shows that these groups do not affect the steady-state transport across the film, but that they do increase the time before permeability begins. The theory is verified by experiments with acid barriers made of polyvinylalcohol containing colloidal zinc oxide. These results imply that the time that barrier polymers are effectiue can be increased about two orders of magnitude. When reactive groups are combined with impermeable flakes, this time can be increased about three orders of magnitude. For example, a polymer barrier currently effective for one hour can be made effectiue for over one year.

Eric Nuxoll

Papers

Polydisperse flakes in barrier films

Barrier membranes with different sizes of aligned flakes

A hydrogel-based implantable micromachined transponder for wireless glucose measurement.

Reactive barrier films

BioMEMS in drug delivery.