Showing papers by "Emmanuel P. Giannelis published in 2010"

Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell

Abstract: Monodispersed hollow spherical mesoporous particles with tunable particle size and shell thickness were readily synthesized using latex templates and a silica precursor in a weakly basic ethanol−water mixture.

Oriented Arrays of Graphene in a Polymer Matrix by in situ Reduction of Graphite Oxide Nanosheets

Abstract: Graphite oxideNafion hybrids with a high degree of alignment are cast from aqueous solution in the absence of any external field and reduced in situ by exposure to hydrazine to produce grapheneNafion hybrids (see image). Dramatic enhancement of electrical conductivity indicates sufficient accessibility of the inorganic nanosheets to the reducing agent, through the nanochannels formed by the polymeric ionic domains.

The synthesis and properties of nanoscale ionic materials

Abstract: In this article we discuss the effect of constituents on structure, flow, and thermal properties of nanoscale ionic materials (NIMs). NIMs are a new class of nanohybrids consisting of a nanometer-sized core, a charged corona covalently attached to the core, and an oppositely charged canopy. The hybrid nature of NIMs allows for their properties to be engineered by selectively varying their components. The unique properties associated with these systems can help overcome some of the issues facing the implementation of nanohybrids to various commercial applications, including carbon dioxide capture, water desalinization and as lubricants. Copyright © 2010 John Wiley & Sons, Ltd.

Canopy Dynamics in Nanoscale Ionic Materials

Abstract: Nanoscale ionic materials (NIMS) are organic−inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canop...

Silicate Dispersion and Mechanical Reinforcement in Polysiloxane/Layered Silicate Nanocomposites

Abstract: We report the first in-depth comparison of the mechanical properties and equilibrium solvent uptake of a range of polysiloxane nanocomposites based on treated and untreated montmorillonite and fumed silica nanofillers We demonstrate the ability of equilibrium solvent uptake data (and, thus, overall physical and chemical cross-link density) to serve as a proxy for modulus (combining rubber elasticity and Flory−Rehner theory), hardness (via the theory of Boussinesq), and elongation at break, despite the nonideal nature of these networks In contrast, we find that tensile and tear strength are not well-correlated with solvent uptake Interfacial strength seems to dominate equilibrium solvent uptake and the mechanical properties it predicts In the montmorillonite systems in particular, this results in the surprising consequence that equilibrium solvent uptake and mechanical properties are independent of dispersion state We conclude that edge interactions play a more significant role than degree of exfoliat

High refractive index and high transparency HfO2 nanocomposites for next generation lithography

Abstract: HfO2 nanoparticles stabilized with selected ligands possess high refractive index and low absorbance under 193 nm radiation. These materials combined with an appropriate photopolymer were used as a nanocomposite photoresist. The resulting nanocomposite materials were used successfully for high resolution patterning.

Development of an inorganic photoresist for DUV, EUV, and electron beam imaging

Abstract: The trend of ever decreasing feature sizes in subsequent lithography generations is paralleled by the need to reduce resist thickness to prevent pattern collapse. Thinner films limit the ability to transfer the pattern to the substrate during etch steps, obviating the need for a hardmask layer and thus increasing processing costs. For the 22 nm node, the critical aspect ratio will be less than 2:1, meaning 40-45 nm thick resists will be commonplace. To address this problem, we have developed new inorganic nanocomposite photoresists with significantly higher etch resistance than the usual polymer-based photoresists. Hafnium oxide nanoparticles are used as a core to build the inorganic nanocomposite into an imageable photoresist. During the sol-gel processing of nanoparticles, a variety of organic ligands can be used to control the surface chemistry of the final product. The different ligands on the surface of the nanoparticles give them unique properties, allowing these films to act as positive or negative tone photoresists for 193 nm or electron beam lithography. The development of such an inorganic resist can provide several advantages to conventional chemically amplified resist (CAR) systems. Beyond the etch resistance of the material, several other advantages exist, including improved depth of focus (DOF) and reduced line edge roughness (LER). This work will show etch data on a material that is ~3 times more etch-resistant than a PHOST standard. The refractive index of the resist at 193 nm is about 2.0, significantly improving the DOF. Imaging data, including cross-sections, will be shown for 60 nm lines/spaces (l/s) for 193 nm and e-beam lithography. Further, images and physical characteristics of the materials will be provided in both positive and negative tones for 193 nm and e-beam lithography.

Superhydrophilic and solvent resistant coatings on polypropylene fabrics by a simple deposition process

Abstract: A simple, yet general coating method to plasma treated polymeric substrates is presented. The method is based on electrostatic interactions between the surface functionalized nanoparticles and the charged substrate and leads to stable and solvent resistant multilayer coatings. The coatings render polypropylene (PP) hydrophilic and in the case of PP fabric superhydrophilic. The superhydrophilicity is attributed to the topography and increased roughness of the fabric compared to a planar, smooth substrate.

Lead-salt quantum-dot ionic liquids.

Abstract: The electronic energies of lead–salt quantum dots (QDs) are determined primarily by quantum confinement due to their large exciton Bohr radii. The fundamental electronic structure of the QDs (PbS and PbSe) has been worked out by Kang et al., and now research with these materials is turning towards applications. For instance, lead–salt QDs have been used as active materials in photovoltaic devices due to their size-tunable infrared (IR) absorption. They are also efficient IR emitters and could be used in biomedical imaging and in electroluminescent devices. In order for QDs to realize their full potential, their stability (e.g., photostability) and compatibility with other materials must be improved. Accordingly, much effort is devoted to surface passivation and functionalization of QDs, with increasing attention being paid to the use of ionic liquids to passivate the QD surface. Using certain ionic liquid ligands, solid materials can be transferred to a new state that exhibits liquidlike behavior at room temperature. To date, metal nanoparticles and oxide nanoparticles have been functionalized using a polymer ionic liquid. Some semiconductor nanoparticles (e.g., CdSe) functionalized using small-molecule ionic ligands have been reported. In this work, we report the first lead–salt (PbS, PbSe, and PbTe) QD ionic liquid where polymer ionic liquid ligands are used as capping ligands for QDs. The resulting amphiphilic QD ionic liquids exhibit fluidlike behavior at room temperature, even in the absence of solvents. The ionic liquid capping ligands also dramatically improve the photostability of

Fullerol ionic fluids.

Abstract: We report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine®). The ionic fluid was compared to a control synthesized by mixing the partially protonated form (sodium form) of the fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine® (liquid-like) and the control (solid-like).

Random lasing action from ZnO-silica nanohybrids

Abstract: Optically active zinc oxide–silica, inorganic–inorganic nanohybrid materials have been synthesized via a sol–gel process utilizing a room temperature scheme that does not require high temperature annealing. Random laser action is demonstrated from these ZnO–silica nanocomposites. The ZnO nanoparticles act as both the gain and the strong scattering medium, which leads to random optical feedback due to multiple elastic scattering, while the amorphous silica matrix offers a high degree of material stability. Optical pumping of the nanocomposites by ultraviolet laser pulses, of duration shorter than the ZnO photoluminescence lifetime, leads to a profound optical gain behavior and random laser action above a certain threshold value of the excitation energy density. In this context, the effects of laser and material parameters on the observed random lasing are investigated for a series of nanocomposites. The observed dependence of the emission wavelength on excitation energy and the excitation energy density value of the random laser threshold are interpreted on the basis of the formation and the inversion of an electron–hole plasma, respectively.

Nanohybrid Nafion Membranes for Fuel Cells

Abstract: We review strategies to produce Nafion nanohybrid membranes with improved properties based on functionalized silica and clay nanoparticles. Two distinct approaches are presented here: a) the use of H + -exchanged clay platelets to act as physical barriers to methanol diffusion, while having high levels of ionic mobility and b) the application of depletion forces to construct a compact microstructure based on the assembly of clay platelets. Both classes of hybrids exhibit significantly improved selectivity (ratio of ionic conductivity over methanol permeability) and dramatically enhanced thermomechanical properties. Those characteristics are highly desirable for fuel cell applications and strongly depend on the morphological features of the membranes.