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The graphene nanoparticles incorporated in thin polystyrene film in different configurations, garner into unique phenomenon of self-assembly regulated by the self-organization of the thin polystyrene film. The polystyrene–graphene nanoparticles composite when spin-coated together to form a thin film over a substrate, was observed to self-assemble in a Voronoi tessellation of ribbon-like structure. The suppression of dewetting of thin polystyrene film at the stage, where the holes coalesce and grow to form Voronoi tessellation of polymeric ribbons, sways the path for the graphene nanoparticles to self-assemble and organize into a Voronoi tessellation-like pattern of graphene nanoparticles. In the second method, the graphene nanoparticles dispersed in solvent were casted over the instability based dewetting patterns formed on the surface of the thin polystyrene film. This method exclusively caused the graphene nanoparticles to arrange in a polygonal array of dots prompted by the dynamics and morphology of dewetting. The reversals of the dewetted patterns were observed in this process, because of the solvent evaporation and Marangoni flow. The graphene nanoparticles in the presence of solvent destruct and self-healed the dewetted holes formed on the surface of the pure polystyrene thin film.

The graphene quantum dot (GQD) is a carbon allotrope with a planar surface amenable for functionalization and nanoscale dimensions that confer photoluminescent properties. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including as optical biosensors and delivery platforms. In particular, noncovalent functionalization offers a route to reversible modification and preservation of the pristine GQD substrate. However, a clear paradigm for GQD noncovalent functionalization has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to the GQD surface, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates and investigating noncovalent polymer association to these substrates. Distinct adsorption methods are developed for successful ssDNA attachment based upon the GQD’s initial level of oxidation. ssDNA adsorption to the GQD is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. We hypothesize that high GQD oxygen content disrupts the graphitic carbon domains responsible for stacking with the aromatic ssDNA bases, thus preventing the formation of stable polymer-GQD complexes. Finally, we develop a more generic adsorption platform and assess how the GQD system is tunable by modifying both the polymer sequence and type.

Contractile behavior of cardiomyocytes relies on directed signal propagation through the electroconductive networks that exist within the native myocardium. Due to their unique electrical properties, electroactive materials, such as graphene, have recently emerged as promising candidate materials for cardiac tissue engineering applications. In this work, the potential of three-dimensional (3D) nanofibrous graphene and poly(caprolactone) (PCL + G) composite scaffold for cardiac tissue engineering has been explored for the first time. The addition of graphene into PCL led to an increased volume conductivity of scaffolds with an even distribution of graphene particles throughout the matrix. Graphene particles provided local conductive sites within the PCL matrix, which enabled application of external electrical stimulation throughout the scaffold using a custom point stimulation device. When mouse embryonic stem cell derived cardiomyocytes (mES-CM) were seeded on PCL + G scaffolds, cells adhered well, contracted spontaneously, and exhibited classical cardiomyocyte phenotype confirming the biocompatibility of electroactive PCL + G scaffolds. Further functional characterization demonstrated that graphene especially affected Ca2+ handling properties of mES-CM compared to that of cardiomyocytes cultured in 2D culture, highlighting the potential of PCL + G for in vitro cardiac tissue engineering. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part A: 106A: 2923-2933, 2018.

A novel assembly of a photocathode and a photoanode is investigated to explore their complementary effects in enhancing the photovoltaic performance of a quantum-dot solar cell (QDSC). While p-type nickel oxide (NiO) has been used previously, antimony selenide (Sb2Se3) has not been used in a QDSC, especially as a component of a counter electrode (CE) architecture that doubles as the photocathode. Here, near-infrared (NIR) light-absorbing Sb2Se3 nanoparticles (NPs) coated over electrodeposited NiO nanofibers on a carbon (C) fabric substrate was employed as the highly efficient photocathode. Quasi-spherical Sb2Se3 NPs, with a band gap of 1.13 eV, upon illumination, release photoexcited electrons in addition to other charge carriers at the CE to further enhance the reduction of the oxidized polysulfide. The p-type conducting behavior of Sb2Se3, coupled with a work function at 4.63 eV, also facilitates electron injection to polysulfide. The effect of graphene quantum dots (GQDs) as co-sensitizers as well as e...

It is one of the most important needs to develop renewable, scalable and multifunctional methods for the fabrication of 3D carbon architectures. Even though a lot of methods have been developed to create porous and mechanically stable 3D scaffolds, the fabrication and control over the synthesis of such architectures still remain a challenge. Here, we used Magnetospirillum magneticum (AMB-1) bacteria as a bio-template to fabricate light-weight 3D solid structure of carbon nanotubes (CNTs) with interconnected porosity. The resulting porous scaffold showed good mechanical stability and large surface area because of the excellent pore interconnection and high porosity. Steered molecular dynamics simulations were used to quantify the interactions between nanotubes and AMB-1 via the cell surface protein MSP-1 and flagellin. The 3D CNTs-AMB1 nanocomposite scaffold is further demonstrated as a potential substrate for electrodes in supercapacitor applications.

In this work, we present the formation of unique self-assembled graphene patterns at the interface between graphene and a thin polystyrene (PS) film at room temperature. When a minute amount of graphene dispersed in a solvent is added on PS and spin-coated into a thin film, the concentration gradient caused by centrifugal force leads to a Marangoni flow that in conjunction with the dewetting of the underlying PS at the edges lead to a series of very interesting and self-assembled morphologies of graphene. At the particle enriched zone near the center, the graphene-particles exhibit morphologies ranging from folds, wrinkles, flakes, onion-rings to blob structures depending on the aspect ratio. The graphene-particles thrown to the periphery are found to march back towards the central portion leading to the unique formation of very ordered nano-scale scratches on the PS substrate. The nano-particles that end up into the confined rims in the intermediate region get twisted into nano-ribbons and dendrimers. The paper sheds light on the forces responsible for the evolution of different origami structures formed as a result of the underlying dewetting dynamics without the aid of any high-end instrumentation or process. Since these self-assembled structures are formed over a bio-compatible polymer, the structures are anticipated to find applications in fabricating biosensor, super-capacitors, and biomedical microfluidic devices.

Fundamental understanding of interactions at the interface of biological molecules, such as proteins, and nanomaterials is crucial for developing various biocompatible hybrid materials and biosensing platforms. Biosensors comprising of graphene-based conductive nanomaterials offer the advantage of higher sensitivity and reliable diagnosis mainly due to their superior specific surface area and ballistic conductivity. Furthermore, conductive nanocomposite structures that immobilize proteins can synergize the properties of both transducers and molecular recognition elements improving the performance of the biosensing device. Here we report for the first time, using a combined molecular dynamics simulations and experimental approach, the interactions between avidin and graphene for the development of a sensing platform that can be used for the detection of biological macromolecules such as mismatch repair proteins through biotinylated DNA substrates. We find that the interactive forces between avidin and graphene are mainly hydrophobic, along with some van der Waals, electrostatic and hydrogen bonding interactions. Notably, the structure and function of the avidin molecule are largely preserved after its adsorption on the graphene surface. The MD results agree well with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) analysis of avidin immobilized on a graphenated polypyrrole (G-PPy) conductive nanocomposite confirming the adsorption of avidin on graphene nanoplatelets as observed from the Fourier-transform infrared spectroscopy (FTIR).

Novel approaches to boost quantum dot solar cell (QDSC) efficiencies are in demand. Herein, three strategies are used: (i) a hydrothermally synthesized TiO2–multiwalled carbon nanotube (MWCNT) composite instead of conventional TiO2, (ii) a counter electrode (CE) that has not been applied to QDSCs until now, namely, tin sulfide (SnS) nanoparticles (NPs) coated over a conductive carbon (C)-fabric, and (iii) a quasi-solid-state gel electrolyte composed of S2−, an inert polymer and TiO2 nanoparticles as opposed to a polysulfide solution based hole transport layer. MWCNTs by virtue of their high electrical conductivity and suitably positioned Fermi level (below the conduction bands of TiO2 and PbS) allow fast photogenerated electron injection into the external circuit, and this is confirmed by a higher efficiency of 6.3% achieved for a TiO2–MWCNT/PbS/ZnS based (champion) cell, compared to the corresponding TiO2/PbS/ZnS based cell (4.45%). Nanoscale current map analysis of TiO2 and TiO2–MWCNTs reveals the presence of narrowly spaced highly conducting domains in the latter, which equips it with an average current carrying capability greater by a few orders of magnitude. Electron transport and recombination resistances are lower and higher respectively for the TiO2–MWCNT/PbS/ZnS cell relative to the TiO2/PbS/ZnS cell, thus leading to a high performance cell. The efficacy of SnS/C-fabric as a CE is confirmed from the higher efficiency achieved in cells with this CE compared to the C-fabric based cells. Lower charge transfer and diffusional resistances, slower photovoltage decay, high electrical conductance and lower redox potential impart high catalytic activity to the SnS/C-fabric assembly for sulfide reduction and thus endow the TiO2–MWCNT/PbS/ZnS cell with a high open circuit voltage (0.9 V) and a large short circuit current density (∼20 mA cm−2). This study attempts to unravel how simple strategies can amplify QDSC performances.

The counter electrode (CE), despite being as relevant as the photoanode in a quantum dot solar cell (QDSC), has hardly received the scientific attention it deserves. In this study, nine CEs (single-walled carbon nanotubes (SWCNTs), tungsten oxide (WO3), poly(3,4-ethylenedioxythiophene) (PEDOT), copper sulfide (Cu2S), candle soot, functionalized multiwalled carbon nanotubes (F-MWCNTs), reduced tungsten oxide (WO3–x), carbon fabric (C-Fabric), and C-Fabric/WO3–x) were prepared by using low-cost components and facile procedures. QDSCs were fabricated with a TiO2/CdS film which served as a common photoanode for all CEs. The power conversion efficiencies (PCEs) were 2.02, 2.1, 2.79, 2.88, 2.95, 3.78, 3.66, 3.96, and 4.6%, respectively, and the incident photon to current conversion efficiency response was also found to complement the PCE response. Among all CEs employed here, C-Fabric/WO3–x outperforms all the other CEs, for the synergy between C-Fabric and WO3–x comes to the fore during cell operation. The low...

A novel nanocomposite has been developed using extracted cellulose from marine algae coated with conductive polypyrrole and graphene nanoplateletes. The nanocomposite fabricated via in situ polymerization was used as an electrode for a supercapacitor device. The nanocomposite material has been electrochemically characterized using cyclic voltammetry to test its potential to super-capacitive behavior. The specific capacitance of polypyrrole-graphene-cellulose nanocomposite as calculated from cyclic voltammetry curve is 91.5 Fg-1 at the scan rate 50 mV s-1. Transmission electron microscope images show the polymerized polypyrrole -graphene coated cellulosic nanofibers. Scanning electron microscope images reveal an interesting "necklace" like beaded morphology on the cellulose fibers. It is observed that the necklace like structure start to disintegrate with the increase in graphene concentration. The open circuit voltage of the device with polypyrrole-graphene-cellulose electrode was found to be around 225 mV and that of the polypyrrole-cellulose device is only 53 mV without graphene. The results suggest marked improvement in the performance of the nanocomposite supercapacitor device upon graphene inclusion.

Graphene and its derivatives having at least one dimension in nanoscale range have attracted tremendous attention in recent years due to their unique electronic, optical, chemical, and mechanical properties. This chapter is about graphene quantum dots (GQDs) that are zero-dimensional graphene derivatives with one to few layers of graphene sheet having size range less than 20nm. This chapter is an overview of synthesis of GQDs by top-down and bottom-up approaches, as well as detailed methods of synthesis of GQDs by acidic oxidation of carbon fibers. Owing to their extremely small size, quantum confinement, edge effect, biocompatibility, low toxicity, photostability as well as water solubility they are excellent candidates for understanding biological systems and cellular processes at the molecular scale. These are also suitable nanomaterials to replace inorganic semiconducting nanoparticles (e.g., CdS, CdSe, ZnS, and Si) which are toxic to biological systems.

Vaccination is a safe and effective approach to prevent deadly diseases. To increase vaccine production, we propose that a mechanical stimulation can enhance protein production. In order to prove this hypothesis, Sf9 insect cells were used to evaluate the increase in the expression of a fusion protein from hepatitis B virus (HBV S1/S2). We discovered that the ultrasound stimulation at a frequency of 1.5 MHz, intensity of 60 mW/cm2, for a duration of 10 minutes per day increased HBV S1/S2 by 27%. We further derived a model for transport through a cell membrane under the effect of ultrasound waves, tested the key assumptions of the model through a molecular dynamics simulation package, NAMD (Nanoscale Molecular Dynamics program) and utilized CHARMM force field in a steered molecular dynamics environment. The results show that ultrasound waves can increase cell permeability, which, in turn, can enhance nutrient / waste exchange thus leading to enhanced vaccine production. This finding is very meaningful in either shortening vaccine production time, or increasing the yield of proteins for use as vaccines.

The creation of three-dimensionally engineered nanoporous architectures via covalently interconnected nanoscale building blocks remains one of the fundamental challenges in nanotechnology. Here we report the synthesis of ordered, stacked macroscopic three-dimensional (3D) solid scaffolds of graphene oxide (GO) fabricated via chemical cross-linking of two-dimensional GO building blocks. The resulting 3D GO network solids form highly porous interconnected structures, and the controlled reduction of these structures leads to formation of 3D conductive graphene scaffolds. These 3D architectures show promise for potential applications such as gas storage; CO2 gas adsorption measurements carried out under ambient conditions show high sorption capacity, demonstrating the possibility of creating new functional carbon solids starting with two-dimensional carbon layers.

In the pursuit of advanced polymer composites, nanoscale fillers have long been championed as promising candidates for structural reinforcement. Despite progress, questions remain as to how these diminutive fillers influence the distribution of stresses within the matrix and, in turn, influence bulk mechanical properties. The dynamic mechanical behavior of elastomer-impregnated forests of carbon nanotubes (CNTs) has revealed distinct orientation-dependent behavior that sheds light on these complicated interactions. When compressed along the axis of the fillers, the composite will mimic open-cell foams and exhibit strain softening for increasing amplitudes due to the collective Euler buckling of the slender nanotubes. In contrast, the same material will behave similarly to the neat polymer when compressed orthogonal to the alignment direction of the nanotubes. However, in this orientation the material is incapable of achieving the same ultimate compressive strain due to the role that the embedded nanotubes play in augmenting the effective cross-link density of the polymer network. Both of these responses are recoverable, robust, and show little dependency on the diameter and wall-number of the included CNTs. Such observations give insight into the mechanics of polymer/nanoparticle interactions in nanocomposite structures under strain, and the thoughtful control of such coordinated buckling behavior opens the possibility for the development of foam-like materials with large Poisson ratios.

A novel design of a laboratory built axially rotating collector (ARC) having capability to align electrospun nanofibers have been described. A detailed morphological comparison of such nanofibers orientation and their geometry is done using scanning electron microscopy (SEM). For comparison various polymeric solutions were electrospun on conventional static collector as well as ARC. The average diameter of polyvinyl alcohol (PVA) nanofibers was found to be 250 nm while polycaprolactone (PCL) nanofibers were found to be within a range of 600-800 nm. Conducting nanoparticles such as graphene and multi-walled carbon nanotubes (MWNTs) mixed with polymer solutions shown to have a significant influence on the overall geometry of these nanofibers and their diameter distribution. It is evident from the SEM analysis that both graphene and MWNTs in polymer solution play a crucial role in achieving a uniform diameter of nanofibers. Lastly, the formation of the aligned nanofibers using ARC has been mathematically modeled and the electromagnetic field governing the process has been simulated.

Nanotechnology is an emerging paradigm for creating functional nanoscale materials for various biomedical applications. In this study, a new nanotechnology-based drug delivery method was developed using gold nanoparticles (GNPs) as a delivery vehicle to reduce adverse drug side effects. Fludarabine Phosphate is a commercial chemotherapy drug used in cancer treatment, and has ability to kill various cancer cells. KG-1 cell, a type of acute cancer leukemia cell, was selected as a proof-of-concept target in this study. Due to the small size of GNPs, they can help Fludarabine Phosphate enter cancer cells more efficiently and better interfere with DNA synthesis in the cancer cells. To enhance targeting ability, folic acid molecules were also covalently linked to GNPs, resulting in GNP-Fludarabine-folic acid (GNP-F/f). Compared to treatments with GNP-F or drugs on its own (Fludarabine Phosphate), the GNP-F/f achieves much improved cell-killing effects. The UV-Vis spectra results also revealed that the drugs had successfully bonded covalently to the GNPs. The higher cell-killing efficiency of GNP-F/f compared with GNP-Fludarabine (GNP-F) or drugs on their own further validates the effectiveness of both the vectors (GNPs) and folic acid in enhancing the drug delivery to the cancer cells. The MTT viability tests showed that the GNPs had no cytotoxicity.

The chemical mode of action as a flame retardant of calcium carbonate nanoparticles combined with ammonium polyphosphate in polypropylene was investigated. Reduction in burning rates for 0.5 mm thick samples were observed without appreciable char formation up to 30 wt % loading of additives. Thermogravimetric analysis (TGA) of the mixture of CaCO3 and ammonium polyphosphate (APP) showed that calcium carbonate nanoparticles react with ammonium polyphosphate before the degradation of the phosphate chains. TGA–FTIR studies of the polymer composite samples and powder mixtures of the additives confirmed the evolution of ammonia and carbon dioxide due to interaction between the additives. X-ray diffraction (XRD) analysis of chars, obtained after burning the films, showed definite diffraction peaks corresponding to that of calcium metaphosphate. The inert gasses produced by the interaction of the additives hindered the advancing flame and, thus, reduces the burning rates, at times even without char formation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A comparative study of the structural, thermal, mechanical and thermomechanical properties of ethylene-octene copolymer' (mPE) 2 nanocomposites synthesized with pure nanosilica (NS) and nanosilica-functionalized with diglycidyl ether of bisphenol-A (ENS) has been reported. These nanocomposites were prepared using "melt mixing" method at a constant loading level of 2 . 5 wt. %. The effects of pure nanosilica (NS) and epoxy resin-functionalized-nanosilica (ENS) on the above mentioned properties of ethylene-octene copolymer were analyzed by wide-angle-x-ray diffractometer (WAXD), transmission electron microscope (TEM), thermo gravimetric analyzer (TGA), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM). TEM studies have shown a better dispersion of nanoparticles in case of ethylene-octene copolymer-epoxy resin-functionalized-nanosilica nanocomposite (mPE-ENS) than that of ethylene-octene copolymer-nanosilica nanocomposite (mPE-NS). The tensile tests show that organic modification of nanosilica particles brings up an appreciable increase in yield strength, ultimate tensile strength and elongation at break of the polymer. DMA studies have shown an increase in the storage modulus and glass transition temperature for mPE-ENS with respect to mPE-NS. Further, the TGA results have shown a higher thermal stability for mPE-ENS in comparison to mPE-NS.

Flame-retardant properties of nylon 6/organically modified montmorillonite (OMMT) thin films, fibers, and fabrics were investigated to determine the efficacy of condensed-phase flame-retardant mechanism in relation to montmorillonite concentration, sample geometry, and flame test conditions. Horizontal flame spread conducted on thin films revealed no significant difference in burning behavior between nylon 6 and nanocomposites with 5 wt% OMMT. However, with a higher concentration level of 8–10 wt% OMMT, the films burned without any dripping. The flame spread rate was reduced by 30–40% as compared with nylon 6 films. Cone calorimeter study on nanocomposite films showed that the peak heat release rate of nylon 6 was reduced by 65–67% with 8–10 wt% OMMT. Undrawn nanocomposite monofilaments with 10 wt% OMMT burned slowly and steadily in Bunsen flame without dripping. In cone calorimeter, nanocomposite fabrics with 8 wt% OMMT showed reduced heat release rate and mass loss rate compared to nylon 6 fabrics with increase in fabric tightness factor. The mass loss rate was about 40–60% less when compared with nylon 6 fabrics. The fabric char structure remained intact after burning. This demonstrated the interdependence of fabric tightness factor, OMMT concentration, and source of heat flux in forming a protective char and affecting the flammability of fabrics. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Uniform dispersion, orientation and adhesion between carbon nanotubes and polymer matrix are essential for the improved mechanical properties in the nanocomposite. We prepared multi-wall carbon nanotubes (MWNT)-nylon 6 nanocomposites using an in-situ polymerization technique, assisted with a few minutes (3-4 minutes) of ultrasonication. Fibers were then extruded from prepared nanocomposite using a single screw extruder and stretched for draw ratio 3 and 4 respectively. Uniform dispersion was achieved due to the effect of ultrasonication and quick polymerization. DSC studies indicated the presence of interactions between nylon 6 polymer and MWNTs. SEM studies showed the nearly oriented carbon nanotubes inside the nanocomposite fibers. Improved mechanical properties were observed as a result of proper dispersion, orientation and interfacial interactions. However at higher MWNT loadings (> 0.5 %), molecular weight of the synthesized nylon 6 reduced significantly, resulting in decreased mechanical properties.

We investigated the effect of organically modified clay alone and in combination with zinc borate on the thermal/flammability behavior of nylon-6 nanocomposites. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increase in clay concentration. Nanocomposite films of approximately 0.5 mm thickness with 2.5 and 5 wt % clay burned for almost the same duration as neat nylon-6 but with reduced dripping in horizontal flame test. The 10 wt % clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25–30%. Zinc borate/clay containing nanocomposite developed into a very good intumescent system in cone calorimeter test, swelling about 10–13 mm height prior to ignition forming a cellular char structure. This was found to be an effective composition in reducing the heat release and mass loss rate of nylon-6 by about 65% and at par with 10 wt % clay nanocomposite. Flame retardant behavior could be attributed to distinct char morphologies observed through scanning electron microscopy. Fourier transform infrared spectroscopy of the 10 wt % clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1540–1550, 2007

Supercapacitors also known as electrochemical capacitors, that store energy via either Faradaic or non-Faradaic processes, have recently grown popularity mainly because they complement and can even replace, conventional energy storage systems in variety of applications. Supercapacitor performance can be improved significantly by developing new nanocomposite electrodes which utilizes both the energy storage processes simultaneously. Here we report, fabrication of the freestanding hybrid electrodes, by incorporating graphene and carbon nanotubes (CNT) in pyrrole monomer via its in-situ polymerization. At the scan rate of 5 mV s−1, the specific capacitance of the polypyrrole-CNT-graphene (PCG) electrode film was 453 F g−1 with ultrahigh energy and power density of 62.96 W h kg−1 and 566.66 W kg−1 respectively, as shown in the Ragone plot. A nanofibrous membrane was electrospun and effectively used as a separator in the supercapacitor. Four supercapacitors were assembled in series to demonstrate the device performance by lighting a 2.2 V LED.

Nanoparticle-embedded acrylic coatings that can absorb copious amounts of UV radiation yet scatter little were developed to protect base fabrics from sun-induced degradation. Zinc oxide and titanium dioxide nanoparticles with diameters ranging from 15 to 70 nm were used. Nanoparticles (5 wt%) were dispersed in acrylic emulsions. Nanoparticle-embedded acrylic films of 10 μm and 20 μm thick were prepared and bonded to Kevlar fabric. Mechanical tests as well as infrared, visible and UV spectroscopy were used to characterize nanoparticle-embedded acrylic emulsions and coated Kevlar fabric. The changes in mechanical and chemical properties of Kevlar fabric after a day and week of intense UV exposure were assessed using tear and strip tensile testing, UV, visible and infrared spectroscopy, and wide and small angle X-ray analysis. Tear and tensile data, with support from UV results, showed that 20 μm nanoparticle-embedded coatings largely prevented degradation of Kevlar fabric, allowing only 5% of the degradation that occurred in the unprotected fabric after a week of UV exposure.

During the last 10 years extensive research has been conducted on various aspects of electrospinning. These efforts include spinning many different polymer and solvent pairs, varying fiber forming conditions, fiber characterization and process modeling. In this work we explore some issues related to charging of the polymer solution, namely charge quantification of electrospun fibers and different charge delivery designs. PAN fibers electrospun in our laboratory show a charge density of 30–50 nC/mg. The charge density varied with applied voltage and solution properties. Theoretical charge density calculations agree well with experimental measurements. Different charging approaches, such as positive or negative induction charging and ionized field charging, all led to fine fiber formation.

Blends of polyethylene terephthalate (PET) and glass-filled thermotropic liquid crystalline polymer (LCP-g) were prepared by a melt mixing technique. The microstructure of the blends, as assessed by XRD, was correlated with the thermal and dynamic properties. At a lower level (up to 20%) of LCP-g, growth is favored. The transition, within the range of 254°–257°C, is the combined effect of melting followed by crystallization, resulting in precipitation of a component in the crystallizing state as observed from DSC analysis. The relaxation phenomena, as observed from DMTA analysis, changed depending on the blend ratio. The structural restrain imposed by the neighboring molecular chain in the crystalline phase shifts the relaxation peak at the higher temperature side. The variation of storage modulus, stiffness, and loss modulus as a function of blend ratio suggested that the phase inversion was at the level of 40 to 50% of LCP-g in the blend. [Under dynamic application at the lower level of LCP-g, the failu...

Magnetospirillum magneticum (AMB-1), which belong to alpha-protobacterium are gram-negative, single-celled prokaryotic organisms consisting of a lash-like cellular appendage called flagella. These filamentous structures are made up of a protein called flagellin that in turn consist of four sub-domains, two inner domains (D0, D1) made up of alpha-helices and two outer domains (D2, D3) made up of beta sheets. It is wrapped in a helical fashion around the longitudinal filament with the outermost sub-domain (D3) exposed to the surrounding environment. This study focuses on the interaction of the D3 with semiconducting as well as metallic single-walled carbon nanotubes (m-SWNT) and in turn presents the interactive forces between the SWNT and D3 from the perspective of size and type of SWNT. It is found that the SWNT interacts the most with glycine and threonine residues of flagellin both electrostatically as well as through van der waals. Further, the viability of magnetotactic bacteria Magnetospirillum magneticum (AMB-1) in the presence of SWNT is experimentally investigated and it is found that magnetotaxis in AMB-1 is preserved without any toxic effects due to SWNT. It is proposed that AMB-1 can be used as an efficient carrier of carbon nanotubes through its flagellum for semiconductor nanofabrication tasks.

Dry eye symptoms are moderately common in the general population and are often chronic particularly amongst the older adults above age 65. Dry eye can occur from conditions such as aging, dehydration, corneal ulcers and associated infections, vitamin A deficiency or as a temporary or permanent side effect of laser treatment. Some of the tests available to identify a tear deficient eye are Schirmer strip test, strip Meniscometry and phenol red thread test, the most popular being the Schirmer's test, where a patient is tested positive for a dry eye if the test strip is wet for less than 5mm of length over a period of 5 minutes and negative for wetting of at least 10mm within 5minutes. Here we report a simple design and fabrication of an efficient dry eye test strip using a laboratory developed metal rotating collector for electrospinning setup that aligns nanofibers of Polycaprolactone (PCL), a biosafe and biodegradable polymer. Electrospun PCL nanofibers have diameters in the range of 70 – 150nm depending upon the protocol creating either aligned or randomly oriented nanofibers. It was found that both random and aligned PCL nanofibers test strips show fast wetting time of 5 seconds for covering the same distance of 10mm that a conventional test strip covers in 5 minutes making our product approximately sixty times faster and exhibiting high throughput. We believe that this is because of higher capillary transport and better wetting of the nanofibers. It is further demonstrated that the concentration of PCL plays a crucial role in the formation of the nanofibers and hence the wetting phenomena.

Over the years, many designs for biobandage were introduced for different types of burns but in most cases these designs are introduced as a protection means to cover and protect the burned tissue from the bacterial infection not as a treatment means. In this paper a new model for a burns biobandage is introduced not only as a protective mean but also as a treatment technique by helping the tissue to rebuild itself as fast as possible. The main objective of this research is to develop a simple cryotherapeutic system to absorb the large amount of heat produced by the burned tissue and reducing its temperature in order to facilitate the tissue healing and regeneration process. A biobandage is proposed to include an iced layer as a cooling source, a cotton layer and a water gel layer for comfort and temperature control, and a plastic layer to seal the ice layer. The combination of these four layers physically work together to reduce inflammation, which in turn make the heeling or recovery time shorter and reduce pain as a result of decreasing the nerve conductivity. The COMSOL Multiphysics was used to model the cooling process on burned tissue using the proposed iced-biobandage. The calculated temperature profiles along the depth biobandage and burned skin provide a clear visualizing of the heat flow within each layer. The history of temperature and heat transfer rate at the burned skin surface are monitored for an effective cooling and healing process. A modeling analysis was performed to examine the changes of temperature over a predetermined time and to help in identifying the optimal period for ice cooling process, the analysis shows that the ice layer is effective within a certain period of time and after this period it doesn't add any beneficial effect.

Magnetotactic bacteria (MTB), discovered in early 1970s contain single-domain crystals of magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ) called magnetosomes ranging from 35 to 120 nm in size. These crystals tend to form a chain like structure from the proximal to the distal pole along the long axis of the cell and align through an acidic protein mamJ to the bacterial cytoskeleton filament made out of actin-like protein mamK. The ability of these bacteria to sense the magnetic field, also called magnetotaxis, arises from the magnetic dipole moment of the entire chain of magnetosomes acting as a large magnet. Such organisms being facultatively anaerobic are able to sense the geomagnetic field and traverse the oxic-anoxic interface in aquatic habitats for optimal oxygen concentrations. Two aspects that are of particular interest are their phenomenal control of direction using magnetic field as well as the efficient displacement of selective nanoparticles. We aim to understand the efficacies of Magnetospirillum magneticum (AMB-1) in miniaturized semiconductor fabrication utilizing single and multi-walled carbon nanotubes.

MEMS are typically defined as the devices or systems which are integrated with electrical and mechanical components on a silicon substrate through the microfabrication techniques. Due to its low cost, small size, low power consumption with high efficiency, MEMS technology has been widely used in many fields. In this paper, the design and simulation of a magnetic micropump with tri-membrane fully differential structure is presented. The proposed micropump has two inlets and two outlets. It has two pumping chambers sealed by three Si membranes. A permanent magnet is deposited on the middle membrane. Poly-Si coils are deposited on the top and bottom membranes separately. When electrical current is conducted in the coil, a magnetic field is excited, and its polarity (north and south poles) can be easily exchanged by reversing the conducting current. The design and analysis of the micropump has been discussed in details, and based on those theoretical analysis, a set of optimized design parameter has been achieved. The ANSYS simulation is used to verify the function of micropump. The proposed micropump leads to improved pumping rate with better efficiency.

The blending of hypalon (chlorosulfonated polyethylene [CSM]) with ethylene propylene (EP) in the presence of different grafting agents is expected to improve the interchain crosslinking between the non-functionalized EP and CSM phases. Five different grafting agents were chosen to introduce functional groups in the EP polymer. The reactive blending technique was used in the present work. The EP/CSM blending improves the shrinkability of the blends. The maximum extent of crosslinking is obtained in the presence of 4-4′ diamine diphenyl methane while the minimum magnitude in found the presence of maleic anhydride. The interchain crosslinking phenomenon has been put forward through grafting, the extent of which depends on the grafting agent used. The results of the X-ray diffraction study are in good agreement with thermal analysis.

Conductive fabrics have become an area of research interest due to the emerging applications and rapid development in e-textile industry. Advances in conductive fabrics, metal coated textile, and flexible electronics have lead to the development of novel biomedical embedded wearable system with integrated sensors, circuits and antennas. The object of the research is to develop a non-contact Ag/AgCl electrode using silver coated polyurethane fabrics. Polyurethane is considered as one of the best textiles materials for such applications [1]. Pure silver is a highly electrical and thermal conductive material. Electroplated thin film silver retain these characteristics which makes it useful in many applications such as printed circuit boards and systems [2]. Unlike electroplating, where externally supplied electrons from external energy source act as the reducing agent, electroless plating depends upon catalytic reduction of the metal ion in an aqueous solution containing reduction agent. The deposition takes place without any external electrical energy. In our research, we are using chemical plating, an autocatalytic deposition method, to depositing active metals on nonconductive passive textile surface.

An artificial pancreas has a profound impact on changing the life of patients with Type 1 diabetes (T1D). In spite of the obvious improvements in continuous glucose sensor field, there are still limitations presented such as short life time, existence of lag time, and biocompatibility issues. This paper presents a novel idea of Intravascular Multilayered Glucose Sensor (IMLGS), which is used in the closed loop system of artificial pancreas for T1D patients. This work demonstrates glucose detection directly from the blood using glucose layers made from polyaniline carbon paste (PANI-CPE) crosslinking with a glucose enzyme. The layers of glucose sensors are controlled, and switched from layer to another layer using an algorithm strategy based on calculation of calibration factor. We utilized patient glucose data and criteria of sensor replacement to simulate our proposed idea of IMLGS. Simulation results showed that the total duration time of the glucose sensor occupied approximately 134 days for a five-layer sensor. The simulations also showed that the glucose layer sensor is replaced when the calibration factor exceeds threshold value of 10.8-12.68mg/dlnA-1.

Biological tissues have the remarkable ability to remodel and repair in response to disease, injury and mechanical stresses. Synthetic materials lack the complexity of biological tissues, and man-made materials that respond to external stresses through a permanent increase in stiffness are uncommon. Here we report that polydomain nematic liquid crystal elastomers increase in stiffness by up to 90% when subjected to a low-amplitude (5%), repetitive (dynamic) compression. Elastomer stiffening is influenced by liquid crystal content, the presence of a nematic liquid crystal phase and the use of a dynamic as opposed to static deformation. Through rheological and X-ray diffraction measurements, stiffening can be attributed to a mobile nematic director, which rotates in response to dynamic compression. Stiffening under dynamic compression has not been previously observed in liquid crystal elastomers and may be useful for the development of self-healing materials or for the development of biocompatible, adaptive materials for tissue replacement.

Classical experiments show that the force required to slide liquid drops on surfaces increases with the resting time of the drop, t(rest), and reaches a plateau typically after several minutes. Here we use the centrifugal adhesion balance to show that the lateral force required to slide a water drop on a graphene surface is practically invariant with t(rest). In addition, the drop's three-phase contact line adopts a peculiar micrometric serrated form. These observations agree well with current theories that relate the time effect to deformation and molecular re-orientation of the substrate surface. Such molecular re-orientation is non-existent on graphene, which is chemically homogenous. Hence, graphene appears to provide a unique tribological surface test bed for a variety of liquid drop-surface interactions.

Most materials respond either elastically or inelastically to applied stress, while repeated loading can result in mechanical fatigue. Conversely, bones and other biomechanical tissues have the ability to strengthen when subjected to recurring elastic stress. The cyclic compressive loading of vertically aligned carbon nanotube/poly(dimethylsiloxane) nanocomposites has revealed a self-stiffening response previously unseen in synthetic materials. This behavior results in a permanent increase in stiffness that continues until the dynamic stress is removed and resumes when it is reapplied. The effect is also specific to dynamic loads, similar to the localized self-strengthening that occurs in biological structures. These observations help to elucidate the complex interactions between matrix materials and nanostructures, and control over this mechanism could lead to the development of adaptable structural materials and active, load-bearing artificial connective tissues.

“Label-free” biomolecule sensors for detection of inflammatory cardiovascular biomarker associated with vulnerable coronary vascular plaque were designed and fabricated using micro and nano-textured polystyrene structures that functioned as sensing elements coupled with electronic measurement equipment. We demonstrated that scaling down the surface texturing from the micro to the nanoscale enhances the amplitude of the measured signal strength. We believe that the nanoscale fiber morphology provides size matched spaces for trapping and immobilizing the protein biomolecules resulting in enhanced detection and signal strength. We selected polystyrene as the model system and demonstrated the detection of human serum C-reactive protein (hs-CRP). We employed these findings in designing a platform “lab-on-a-chip” protein sensor. Comparative studies were performed on two different polystyrene textured surfaces: a polystyrene microsphere mat, and an electrospun polystyrene nanofiber matrix.

Nanobiosensors are devices which incorporate nanomaterials to detect miniscule quantities of biological and chemical agents. The authors have already developed a novel bionanosensor (BNS) for quick, efficient, and precise detection of bacterial pathogens using the principles of CNT-DNA interaction and DNA hybridization. The detection ability of the (BNS) was observed to be independent of the device resistance. Two new methods (low-pass filter (LPF) and curve fitting (CF)) were developed for better analysis of the BNS. These methods successfully model the BNS. Evidence is provided to elucidate the success of the model, which can explain the DNA hybridization on the sensor surface. These models successfully demonstrated the detection of DNA hybridization versus nonhybridization. Thus, the models can not only help in better and efficient design and operation of the BNS, but can also be used to analyze other similar nanoscale devices.

“Label-free” biomolecule sensors for detection of inflammatory cardiovascular biomarker associated with vulnerable coronary vascular plaque rupture were designed and fabricated using micro- and nanotextured polystyrene (PS) polymer structures that functioned as sensing elements coupled with electronic measurement equipment. We demonstrated that scaling down the surface texturing from the micro- to the nanoscale enhances the amplitude of the measured detected signal strength. We believe that the nanoscale fiber morphology provides size-matched spaces for trapping and immobilizing the protein biomolecule, resulting in improved detection signal strength. We selected PS as the model system and demonstrated the detection of human serum C-reactive protein. We employed these findings in designing a platform “lab-on-a-chip” protein sensor. Comparative studies were performed on PS textured surfaces of two different surface features: a PS microsphere mat and an electrospun PS nanofiber matrix. From the Clinical Editor In this study, nanotechnology-based biosensors for vulnerable coronary vascular plaque rupture were designed and fabricated using micro- and nanotextured polystyrene polymer structures. The authors demonstrated that scaling down the surface texturing from the micro- to the nanoscale enhances the sensitivity of this detection method.

We demonstrate a simple one-step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV-Vis spectroscopy, transmission electron microscopy and X-ray photoemission spectroscopy. The nanoparticle-PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle-PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.

We have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.

Carbon nanotube (CNT) has emerged as potential candidate for replacement of conventional metal patch in antenna application. The principal objective of our research is to develop nanostructured flexible patch antenna array for multi- frequency operation in industrial, scientific and medical (ISM) band. Patch antenna design using CNT on flexible cotton sheets has been simulated with cotton as a substrate and CNT as conductive patch and ground plane. Due to high conformability and conductivity of CNT all antenna parameters like VSWR, return loss, gain and radiation pattern obtained using FEKO EMSS software meet design criteria. Our simulated antenna design shows a return loss less than -10 dB and VSWR less than 2 at 2.06 GHz, 2.38 GHz and 2.49 GHz. We have also simulated a versatile and conformable antenna design where the whole geometry is rolled up like patch array on cylindrical surface. Conformability to curved surfaces and integration with the structure brings about a unique antenna design. An inset fed square patch array is also proposed for RF energy harvesting operating in the 2.45 GHz ISM band that can harvest and store energy from the surrounding environment. Simulation result shows that dc voltage of 0.215 V can be achieved at -6 dbm received energy level at 2.45 GHz IEEE 802.11b band. This would correspond to potential working distance of 10m.

Electrospinning is a technique of producing nanofibers from polymer solution/melt solely under the influence of electrostatic forces. In this research, we investigated the formation of nanofibers by melt electrospinning polycaprolactone (PCL). The effect of process parameters such as molecular weight, applied voltage, and electrode separation on the fiber diameter was investigated. Controlling the process parameters could help increase the proportion of ultrafine fibers in the melt electrospun nonwoven mat. The velocity of the straight jets was in the range of 0.2-1 m/s. The melt electrospun fibers were characterized with respect to fiber diameter, distribution, mechanical properties and birefringence. Melt electrospun polycaprolactone fibers had a diameter distribution of the order of 5 -20 μm. The birefringence of the melt electrospun fibers increased with decrease in fiber diameter.

We have used inkjet printing to deposit silver conducting lines and small PEDOT (conducting polymer) sensors onto fabrics. The printed conductors penetrate into the fabric and can be shown to coat the individual fibers within the yarn, through the full thickness of the cloth. The PEDOT sensor has a resistance in the region of a few kilo-ohms and is connected to measuring equipment by printed silver lines with a resistance of a few ohms. In this way, local strains can be measured at different sites on a fabric. The PEDOT responds to a tensile strain by a reduction in resistance with a gauge factor (change in resistance/strain) from -5 to -20. This compares with conventional strain gauges where the gauge factor is normally +2. These sensors cycle to strains of over 10%. We have measured gauge factors as a function of the orientation of the sensing line to the fabric axes, to the strain axes for different fabric structures. We can correlate the gauge factor with the extent to which the twisted multifilament yarns are expected to become laterally compressed. In preliminary tests we have shown that these printed sensors can be used to monitor knee and wrist motions and so could be used to provide information in applications such as rehabilitation from joint damage.

Most hydrogel actuators and sensors are made via acrylate polymerizations. Because these chain reactions are inhibited by oxygen, it is difficult to prepare thin films or dots with good control. Epoxy curing chemistry is much less sensitive to experimental conditions. We have previously shown that hydrogels formed from reaction between water-soluble amines and epoxides can be readily printed. If the gel is filled with conducting carbon at a level close to the percolation threshold, the resistance changes as water is taken up or removed from the gel. In particular, a pH decrease results in ionization of amine groups and drives swelling of the gel. By incorporating an enzyme, such as glucose oxidase, that releases hydrogen ions when its substrate is present, a resistance change can be used to measure substrate concentrations. These gels also respond to stress with a change in resistance. By making the gel the anode or cathode of an electrolytic cell, they can also be formed as actuators that expand or contract as the pH changes locally. Epoxy chemistry has been little explored for gels. It is very versatile and could be used to make a wide range of gel composites with one or more phases, varying water contents, varying functional groups and a range of electrical conductivity.

A phenyl-containing highly cross linked polyborosiloxane (PBSiO) was synthesized as a flame retardant for polyethylene terephthalate (PET). We coated montmorillonite (MMT) clay, a very high aspect ratio and high specific surface area layered silicate with synthesized PBSiO to introduce synergism in flame retardation to the PET nanocomposite film that retained thermal and mechanical properties. This PBSiO has high thermal stability at the processing temperature (270-285° C) of PET and acts as a compatibilizer between PET and clay that are otherwise incompatible. During burning, the flame retardant PET containing PBSiO and MMT forms a protective borosilicatecarbonaceous intumescent char on the surface. Cone calorimeter tests were performed to evaluate key fire properties of the PET/PBSiO/MMT. The peak heat release rate (PHRR) of PET that contains 5 wt% PBSiO and 2.5 wt% MMT was reduced by 60% and similar trend in the reduction of mass loss rate of the nanocomposite was observed.

We have printed arrays of strain sensors on textiles by inkjet printing of conducting lines and piezoresistive polymer (PEDOT) in order to provide detailed information about the response of a fabric in use. Conducting polymer has been printed onto polyamide and cellulose woven fabrics to form sensors using a modified HP inkjet print-head and X-Y linear positioning table. Good penetration and attachment is found on mercerized cotton but not on polyamide. Silver nitrate lines have been printed onto polyamide and converted to silver connectors by electroless plating. We observed that resistance of silver lines ranged from 0.7-1.5Ω/cm whereas for the conducting polymer it was 1-3 kΩ/mm by a four point probe method. The conducting polymer formed a surface coat on the fabric and also penetrated the weave. On stretching, the surface layer tended to crack but the embedded polymer acts as a strain gauge with a gauge factor of about 5. On the other hand the silver showed minimal change in resistance with stretching, as is required for connectors. Sensitivity towards temperature and humidity and the effect of orientation to stress and weave directions will be reported. Preliminary experiments show that these sensors attached to a sleeve could be effective for monitoring human joint motion.

We investigated the effect of organically modified clay on the thermal and flammability behavior of nylon 6 nanocomposites. We also used zinc borate along with layered silicate with an aim of achieving synergistic effect in flame retardancy. It is found that addition of 10 wt% clay reduced the onset decomposition (5% wt loss) temperature of nylon 6 by 20°C, while addition of 5 wt% zinc borate and 5 wt% clay in combination reduced it by around 10°C. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increasing clay concentration. The horizontal burning behavior of the nanocomposite films of approximately 0.5mm thickness changed with additive concentration. The nanocomposites with 2.5 wt% and 5 wt% clay burned for almost the same duration as neat nylon 6 but dripping was reduced. The 10 wt% clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25-30%. The burn rate of 5 wt % zinc borate/5 wt% clay nanocomposite sample was about 20% higher than that of 10 wt% clay nanocomposite sample, which could be attributed to varying char morphology. Scanning electron microscopy images of the 10wt% clay nanocomposite char surface and cross- section revealed an integrated layer of clay platelets with increasing density gradient from the center to the surface, while the 5 wt% zinc borate/5 wt% clay nanocomposite char appeared foamy and porous. The 5 wt% zinc borate and 5 wt% clay sample developed into a very good intumescent system in cone calorimeter test, swelling about 10-13mm height prior to ignition forming a cellular char structure. This was as effective as the 10wt% clay nanocomposite sample in reducing the heat release and mass loss rate of nylon 6 by around 65%. Fourier transform infrared spectroscopy of the 10 wt% clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char.

The flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.

Polypropylene nanocomposites were prepared using zinc oxide as the filler by melt mixing process. Nanocomposites were also prepared using maleic anhydride grafted polypropylene and methylated-zinc oxide using the same method. The samples were analyzed for observing changes in morphology and thermal stability using various characterizing instruments. The results showed that zinc oxide induced changes in the morphology and thermal stability of polypropylene, though by varying amounts depending on the type of nanocomposite prepared. The nanocomposites prepared from g-PP and methylated zinc oxide showed significant changes in crystallization temperature, decomposition temperature and residue formed upon decomposition, as compared to the rest of the composites or control samples. This was attributed to higher degree of interaction existing at the interphase between the organic and inorganic phases for these nanocomposites.