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The seamless integration of functional biomolecules with advanced nanomaterials not only allows for a hybrid material yielding their combined properties but also can enable novel joint functionality. In this work, the protein bovine serum albumin is used to simultaneously reduce and stabilize graphene oxide, demonstrating complete reduction of the graphene oxide to its reduced graphene oxide form. Where previous work has utilized a protein-reduced graphene oxide hybrid material as an attachment point for subsequent metal nanoparticle binding, this effort establishes an in situ methodology to directly synthesize tailored metal nanoclusters within the stabilizing protein complex. The successful synthesis of gold metal nanoclusters within the protein component of the hybrid system is verified, allowing for the creation of high-density protein-nanocluster ensembles on the graphene substrate. Utilizing the sensitive nature of the high-density protein-nanocluster materials, a protease sensor platform is demonstrated to detect the presence of trypsin, which is a biomarker for acute pancreatitis, at concentrations below 100 ng/mL.

The processing conditions used in the production of advanced polymer fibers facilitate the formation of an oriented fibrillar network that consists of structures spanning multiple length scales. The irregular nature of fiber tensile fracture surfaces suggests that their structural integrity is defined by the degree of lateral (interfacial) interactions that exist within the fiber microstructure. To date, experimental studies have quantified interfacial adhesion between nanoscale fibrils measuring 10-50 nm in width, and the global fracture energy through applying peel loads to fiber halves. However, a more in-depth evaluation of tensile fracture indicates that fiber failure typically occurs at an intermediate length scale, involving fibrillation along interfaces between fibril bundles of a few 100s of nanometers in width. Interaction mechanisms at this length scale have not yet been studied, due in part to a lack of established experimental techniques. Here, a new focused ion beam-based sample preparation protocol is combined with nanoindentation to probe interfaces at the intermediate length scale in two high-performance fibers, a rigid-rod poly(

Copper-nanocarbon, called covetic, films made using pulsed laser deposition (PLD) from a target containing nominally 4 wt% carbon in the copper matrix show uniform integration of up to 4.1 ± 0.2 wt.% C. We observe evidence of s p 2 carbon in PLD Cu covetic films in XPS and a peak in the C K-edge in electron energy loss spectroscopy indicative of transitions from the 1s to π * anti-bonding unoccupied state, suggesting that the C incorporated in the film is graphitic in nature. We measure sheet resistance of 1.7 Ohm/sq and transmittance of 25% at 550 nm in a ≈ 27 nm thick PLD Cu covetic film after deposition. These films also show much reduced oxidation by scanning probe techniques and very stable resistance for over 120 days - significantly longer than e-beam films of the same thickness. Cu covetic films made by PLD show good promise as transparent electrodes.

Electrocharging assisted process is a method for the incorporation of carbon in molten metals under high electric current which results in the formation of networks of carbon nanostructures inside the metal matrix, and gives the new material improved mechanical, electrical and thermal properties. Alloys produced with this method are called covetics. In our previous works, different characterization techniques such X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) confirmed the presence of sp2 crystalline graphene nanoribbons and sheets in Ag and Al-covetic samples. Here, we report on detailed Raman mapping and characterization of Al-6061, Al-7075 and Ag covetics to further investigate the fraction of sp2/sp3 bonding, strain, defects, degree of oxidation, and crystalline sizes of the graphene nanoribbons. Gradual changes of strain are observed in regions with sp2 bonding and some degree of amorphous carbon is revealed by Raman scattering. Different degrees of oxidation of the carbon nanostructures with mostly sp2 bonding are evident by EELS spectrum imaging. Atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) also reveal the presence of graphene ribbons and sheets with different lengths and conductivity.

Electrocharging assisted process has been used to incorporate carbon in Aluminum 6061 and 7075 alloys ensuing significant improvements of the ultimate tensile strength, hardness, and electrical conductivity. This work investigates the presence of carbon, its structure, carbon-metal bonding, surface characterization and dispersion of carbon incorporated in Al alloys by electrocharging assisted process. Networks of Graphene nanoribbons with 3D epitaxy and preferred orientation along the 〈110〉 and 〈112〉 directions of Al are evident by transmission electron microscopy and spectrum imaging of the C K edge electron energy loss spectra. X-ray photoelectron spectroscopy and Raman scattering corroborate sp 2 carbon in Al-6061, and hybrid sp 2 -sp 3 in Al-7075 with added carbon. Kelvin probe force microscopy substantiates the presence of carbon in the Al matrix. Phonon density of states derived from first-principles calculations predicts C Al Raman active modes whilst density functional theory indicates covalent bonding between carbon and Al. This method of incorporation of graphene nanostructures in metals with strong carbon-metal bonding can open up new avenues for incorporation of sp 2 carbon structures in other materials.

The aim of the present study is to utilize fractographic methods employing scanning electron microscope (SEM) images to investigate the effects of build direction and orientation on the mechanical response and failure mechanism for Acrylonitrile–Butadiene–Styrene (ABS) specimens fabricated by fused deposited modeling (FDM). The material characterized here is ABS-M30 manufactured by Stratasys, Inc. Measurements of tensile strength, elongation-at-break and tensile modulus measurements along with the failure surfaces were characterized on a range of specimens at different build direction and raster orientation: ±45°, 0°, 0/90°, and 90°. The analysis of mechanical testing of the tensile specimens until failure will contribute to advances in creating stronger and more robust structure for various applications. Parameters, such as build direction and raster orientation, can be interdependent and exhibit varying effects on the properties of the ABS specimens. The ABS-M30 specimens were found to exhibit anisotropy in the mechanical response when exposed to axial tensile loading. The stress-strain data was characterized by a monotonic increase with an abrupt failure signifying brittle fracture. In certain combinations of build direction and raster orientation tensile failure was preceded by slight softening. The tensile strength and modulus, and elongation-at-break were found to be highly dependent upon the raster orientation and build direction. The relationship between the mechanical properties and failure was established by fractographic analysis. The fractographic analysis offers insight and provides valuable experimental data for the purpose of building structures in orientations tailored to their exemplified strength. For instance, specimens loaded such that bonds between adjacent rasters are the primary load bearing mechanism offer the least significant failure resistance. Other examples are shown where artifacts of the FDM fabrication process act to enhance tensile strength when configured properly with respect to the load. The results highlighted in this study are fundamental to the development of optimal design of complex ultra-light structure weight with increased structural efficiency. The study also presents a systematic scheme employing analogs to traditional fiber-reinforced polymer composites for the designation of build orientation and raster orientation parameters.

Low fiber-direction compressive strength of high-modulus (HM) carbon fiber-reinforced polymers (CFRPs) has been their major weakness prohibiting implementation of such materials in aircraft primary structures despite improving mechanical stiffness at a lower weight. A new HM CFRP achieving fiber-direction compressive strength of intermediate-modulus (IM) CFRPs but with more than 30% higher axial modulus has been recently developed. This work looks into fiber-matrix interface shear strength as a potential mechanism driving the compression strength improvement of the new material system. In-situ scanning electron microscopy (SEM) based single fiber push-out experiments addressing standing challenges associated with manufacturing high-quality samples as well as distinguishing same-diameter HM and IM carbon fibers in the hybrid composite system are used to measure fiber-matrix interface shear strength. The experiments show a 29% lower average value of the fiber-matrix interface shear strength for the HM carbon fibers compared to the IM carbon fibers in the new material system. Such a significant reduction corresponds to a 22% lower fiber-direction compressive strength of the HM CFRP without the integrated IM fibers. The results support the idea of integrating off-the-shelf IM carbon fibers with a stronger fiber-matrix interface and a higher shear modulus into HM CFRPs to improve their compressive strength.

Poly(urethane-urea) (PUU) has been infused into ultrahigh volume fraction carbon nanotube (CNT) forests using a heat-curable polymer formula. Polymer nanocomposites with carbon nanotube volume-fractions of 1%, 5%, 10%, 20%, and 30% were fabricated by overcoming densification and infusion obstacles. These polymer nanocomposites were nanoindented quasi-statically and dynamically to discern process-structure-(mechanical) property relations of polymerizing PUU in such densely-packed CNT forests. A 100× increase in indentation modulus has been observed, which is attributed not only to CNT reinforcement of the matrix, but also to molecular interactions in the matrix itself. Quasi-static elastic moduli ranging from 10 MPa–4.5 GPa have been recorded. Storage modulus for all materials is found to track well at loadings of 200 Hz, with little effect observed from increasing CNT volume fraction. Keywords: carbon nanotubes; polymer nanocomposites; polyurethane urea; self-assembly, United States. Army Research Office (Contract W911NF-13-D-0001)

New methods are needed to reprocess the excess of plastics in the waste stream. In this work, bottle-grade polyethylene terephthalate (PET), Styrofoam, and polycarbonate from compact discs (CDs) were spun into nanofibers as fine as ca. 100 nm in diameter using the electrospinning technique. The mechanical properties of the fibers were evaluated using microtensile testing. The elastic moduli ranged from 15 to 60 MPa, and displayed stiffnesses comparable or greater than fibers made from commercial polymers of equivalent molecular weight. Nanofibers were also prepared from blends of Styrofoam and recycled polycarbonate. Recycled PET fibers were tested for application in water filtration and had greater than 99% filtration efficiency of 1 μm particles. Nanofibers from both pure and mixed waste streams are expected to have applications in myriad areas such as ultra/microfiltration, composites, and tissue engineering.

The direct synthesis of monolayer and multilayer ReS2 by chemical vapor deposition at a low temperature of 450 °C is reported. Detailed characterization of this material is performed using various spectroscopy and microscopy methods. Furthermore initial field-effect transistor characteristics are evaluated, which highlight the potential in being used as an n-type semiconductor.

Protein-encapsulated gold nanocluster (P-AuNC) synthesis was first demonstrated in 2009 [1]. Initially, these P-AuNCs were used as cellular imaging agents as the protein shell surrounding the AuNC made them highly biocompatible. However, recent studies have begun to show that these stabilizing proteins may also retain native biological function, thus giving a dual functionality to these hybrid molecules. Here, we present the synthesis of DNase 1 stabilized AuNCs (DNase 1:AuNCs) with core sizes consisting of either eight or 25 atoms. The DNase 1:Au8NCs exhibit blue fluorescence, whereas the DNase 1:Au25NCs are red emitting. Moreover, in addition to the intense fluorescence emission, the synthesized DNase 1:AuNC hybrids retain the native functionality of the protein, allowing simultaneous detection and digestion of DNA with a detection limit of 2 mg/mL (Figure 1). The DNase 1:AuNCs could be conveniently employed as efficient and fast sensors to augment the current inefficient and time-consuming DNA contamination analysis techniques.

Here we present the synthesis of the enzyme DNase 1 stabilized gold nanoclusters (DNase 1:AuNCs) with core size consisting of either 8 or 25 atoms. The DNase 1:Au8NCs exhibit blue fluorescence whereas the DNase 1:Au25NCs are red emitting. In addition to the intense fluorescence emission, the synthesized DNase 1:AuNC hybrid retains the native functionality of the protein, allowing simultaneous detection and digestion of DNA with a detection limit of 2 μg/mL. The DNase 1:AuNCs could be conveniently employed as efficient and fast sensors to augment the current time-consuming DNA contamination analysis techniques.

We describe a novel approach for coupling pristine graphene with superparamagnetic iron oxide nanoparticles to create dispersed, magnetically responsive hybrids. The magnetic iron oxide (Fe3O4) nanoparticles are synthesized by a co-precipitation method using ferric (Fe3+) and ferrous (Fe2+) salts and then grafted with polyvinylpyrrolidone (PVP). These PVP-grafted Fe3O4 nanoparticles are then used to stabilize colloidal graphene in water. The PVP branches non-covalently attach to the surface of the pristine graphene sheets without functionalization or defect creation. These Fe3O4–graphene hybrids are stable against aggregation and are highly responsive to external magnetic fields. These hybrids can be freeze-dried to a powder or magnetically separated from solution and still easily redisperse while retaining magnetic functionality. At all stages of synthesis, the Fe3O4–graphene hybrids display no coercivity after being brought to magnetic saturation, confirming superparamagnetic properties. Microscopy and light scattering data confirm the presence of pristine graphene sheets decorated with Fe3O4 nanoparticles. These materials show promise for multifunctional polymer composites as well as biomedical applications and environmental remediation.

We describe an experimental approach for characterizing the local mechanical behavior of acrylonitrile butadiene styrene (ABS) structures processed through fused deposition modeling. ABS test specimens processed in various build orientations were subject to multiscale mechanical tests as well as local morphology and chemical analyses. Instrumented indentation, local dynamic mechanical analysis, and atomic force microscopy tests were used to explore the mechanical behavior and morphology of build surfaces and weld interfaces. An interfacial stiffening effect was found for the majority of the specimens tested, with up to a 40% increase in the indentation elastic modulus measured with respect to the build surfaces. Raman spectroscopy mapping of the interfacial areas revealed ∼30% less butadiene/styrene and butadiene/acrylonitrile ratios with respect to analysis of the build surfaces. The results provide insight into the multiscale behavior of additive manufactured structures and offer the potential to guide processing–structure–property understanding of these materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43671.

In this paper, a new approach for characterizing dispersion in nano-enhanced polymers and polymer composites using nanomechanical characterization is developed. Dispersion of Carbon nanofibers (CNFs) as a model nanoscale ingredient is characterized in two model polymer systems: (a) a thermoplastic polymer processed using a Twin Screw Extruder, and (b) a thermoset epoxy processed using sonication during solvent processing. For the first time, the modulus of agglomerated nanofibers was isolated from the polymer matrix enhanced with dispersed nanofibers by using nanomechanical characterization. Thus, it was possible to use these nanomechanical properties in a microstructural model using a Rule-of-Mixtures (ROM) formulation to determine the fraction of dispersed nanofibers, which yielded a dispersion limit of 3 vol% CNFs in the nano-enhanced thermoplastic polymer and 3.5 vol% CNFs in the nano-enhanced thermoset epoxy. It was also possible to predict the modulus measured using microtensile testing, and to determine an effective modulus of 30 GPa for the CNFs, which was attributed to a spring-like effect from kinking along the nanofibers. Applying this characterization to control of dispersion through sonication in the nano-enhanced thermoset epoxy, it was possible to determine the degree of dispersion with sonication time which was described using an Avrami equation. Finally, a carbon-fiber mat was used to create a model nano-enhanced polymer composite whose properties were found to be insensitive to sonication time due to filtering effects from the carbon-fiber mat and varied with CNF concentration in a manner where the CNF modulus could be extrapolated to 30 GPa, consistent with the nano-enhanced polymers.

Protein encapsulated gold nanocluster (P-AuNC) synthesis was first demonstrated in 2009. Initially these P-AuNCs were used as cellular imaging agents as the protein shell surrounding the AuNC made them highly biocompatible. However, recent studies have begun to show that these stabilizing proteins may also retain native biological function thus giving a dual functionality to these hybrid molecules. Here we present the synthesis of DNase 1 stabilized gold nanoclusters (DNase 1:AuNCs) with core sizes consisting either 8 or 25 atoms. The DNase 1:Au8NCs exhibit blue fluorescence whereas the DNase 1:Au25NCs are red emitting. Moreover, in addition to the intense fluorescence emission; the synthesized DNase 1:AuNC hybrid retain the native functionality of the protein, allowing simultaneous detection and digestion of DNA with a detection limit of 2 g/mL (Scheme 1). The DNase 1:AuNCs could be conveniently employed as efficient and fast sensors to augment the current inefficient and time consuming DNA contamination analysis techniques.

As-received morphologies, defect structures, and contact moduli of Kevlar KM2 Plus and three other ballistic fibers varying in chemistry and processing, were observed and compared using atomic force microscopy (AFM) and instrumented nanoindentation (NI) techniques. Surface features and defects were defined and measured for each fiber chemistry: p-phenylene terephthalamides (PPTA including KM2 Plus and Twaron), co-polymer aramid (AuTx), and ultra high molecular weight polyethylene (UHMWPE including Dyneema). Although a multitude of surface defects were observed in each fiber, the types of defects were similar from one fiber type to another. It was found that surface defects generally map to a more compliant local modulus value. Contact modulus values were compared with NI elastic modulus values to demonstrate validity for the AFM technique. Challenges and limitations of the AFM technique for cataloging defects are discussed. This study is the first which attempts to outline the various morphologies found on several fiber surfaces. These local property studies will enable future comparisons with single filament and bulk fiber properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40880.

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

There is a strong need for small, lightweight energy storage devices that can satisfy the ever increasing power and energy demands of micro unmanned systems. Currently, most commercial and developmental micro unmanned systems utilize commercial -off -the -shelf (COTS) lithium polymer batteries for their energy storage needs. While COTS lithium polymer batteries are the industry norm, the weight of these batteries can account for up to 60% of the overall system mass and the capacity of these batteries can l imit mission durations to the order of only a few minutes. One method to increase vehicle endurance without adding mass or sacrificing payload capabilities is to incorporate multiple system functions into a single material or structure. For example, the body or chassis of a micro vehicle could be replaced with a multifunctional material that would serve as both the vehicle structure and the on -board energy storage device. In this paper we present recent progress towards the development of carbon nanotube (CNT)- based structural-energy storage devices for micro unmanned systems. Randomly oriented and vertically aligned CNT-polymer composite electrodes with varying degrees of flexibility are used as the primary building blocks for lightweight structural-supe rcapacitors. For the purpose of this study, the mechanical properties of the CNT-based electrodes and the charge-discharge behavior of the supercapacitor devices are examined. Because incorporating multifunctionality into a single component often degrades the properties or performance of individual structures, the performance and property tradeoffs of the CNT -based structural -energy storage devices will also be discussed.

Diabetes alters adult brain glucose uptake and glucose transporter 1 gene expression. To investigate the effect of diabetes on genes regulating fetal brain glucose uptake, we examined the effect of moderate (blood glucose 10–16.7 mM, normoinsulinemia) and severe (blood glucose >16.8 mM, hypoinsulinemia) maternal diabetes on the expression of genes regulating fetal brain glucose uptake in the genetically nonobese diabetic mouse. In the moderately diabetic state, a 50% decline in fetal brain GLUT1 mRNA levels was associated with a 20% increase in the corresponding GLUT1 protein levels. Simultaneously, although fetal brain GLUT3 mRNA and protein levels were barely detectable, no change in hexokinase I enzyme mRNA, protein (115,000 and 100,000 Mr) or activity, was noted. In the severe form of maternal diabetes GLUT1 protein was unchanged, GLUT3 protein levels remained low, and a 2- to 3-fold increase in the lower molecular form of the hexokinase I protein (100,000 Mr) and enzyme activity occurred. These observations suggest that moderate and severe forms of maternal diabetes do not affect the fetal brain glucose transporter levels to a physiologically significant extent. The severe form of maternal diabetes, however, enhances 1.5- to 3-fold the expression and activity of hexokinase I. This enzyme mediates the rate-limiting step in brain glucose metabolism, namely the intracellular conversion of glucose to glucose–6-phosphate.